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Oil Waste Refinery. Wastes from Crude oil and how they are treated.
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OIL AND GAS WASTE
This research project is carried out to find out the types of waste generated at the well
during crude oil exploration, development and production
Oil and gas wastes are broadly defined to include; Drilling, operation, and plugging of wells
associated with the exploration, development, or production of oil and gas, including oil and gas
wells, fluid injection wells used in enhanced recovery projects, and disposal wells;
• Separation and treatment of produced fluids in the field or at natural gas processing plants;
• Storage of crude oil before it enters a refinery; • Underground storage of hydrocarbons and
natural gas;
• Transportation of crude oil or natural gas by pipeline; • Solution mining of brine; and • Storage,
hauling, disposal, or reclamation of wastes generated by these activities.
‘Oil and Gas Waste’ includes both hazardous and non‐hazardous wastes arising from
generally oil and gas operations. These wastes may be in a liquid, semi‐liquid or solid form.
A NON HAZARDOUS OIL FIELD WASTE (NOW)
An oil and gas waste may be categorized as non‐hazardous via two avenues ‐ If (1) it meets the
EPA hazardous waste exemption criterion or (2) if it is categorized as non‐hazardous based on
sampling, analytics and/or process knowledge to determine that ignitibility, reactivity,
corrosivity, and toxicity criterion are not exceeded. Both approaches entail details and
misconceptions that challenge accurate categorization of the waste.
NON EXEMPT WASTE
Oil and gas wastes not listed by the EPA as generally exempt may or may not be considered
nonhazardous. If the waste is included in EPA’s non‐exempt list, see Appendix C, the waste does
not meet the ‘uniquely associated with primary field operations’ criterion and may not be
categorized as nonhazardous. Other wastes may be considered non‐hazardous if (1) it meets the
‘uniquely associated with primary field operations’ criterion or (2) the waste is characterized as
non‐hazardous. An oil and gas waste may be categorized as non‐hazardous if it:
• Is not listed by non‐exempt (see Appendix C); and • Is not a Listed Hazardous waste, per
Reference 13 and applicable EPA regulations; and • Is sampled, tested, and does not exceed the
ignitibility, corrosivity, reactivity, toxicity hazardous waste criterion of Reference 13 and
applicable EPA regulations; or • By way of process knowledge is characterized as non‐
hazardous.
A .OIL SPILLAGE
SOURCES OF OIL SPILLAGE
Crude oil spill disasters are due to very many factors such as oil well blow – outs, burst and
leaking pipelines or flow stations, overpressure failure and overflow of process equipment
components, hose failure, failures along pump discharge manifolds, sabotage to well heads and
flow line. The principal factors at play in oil spill at the Niger delta can be broadly classified into
three major groups. (i) Equipment failure due to ageing and malfunctioning of systems, (ii) Act
of sabotage, (iii)Negligence on the part of operators.
ENVIRONMENTAL EFFECTS OF OIL SPILLAGE
The effects of crude oil spills when oil comes ashore it kill shore animals by smothering them, or
if sufficiently fresh, kill them because of its toxic constituents. Oil taints fish and interferes with
fishing activities and navigation. Spilled oil makes a great mess. Polycyclic aromatic
hydrocarbons in crude oil may be toxic, Carcinogenic and teratogenic. Whereas the sea has
enormous capacity to absorb the various attempts by man to degrade it, the streams, creek, rivers,
estuaries, swamps and land have only a little capacity to do so’.
PROBLEMS ASSOCIATED WITH OIL SPILL DISASTER: The devastating effects of oil
spill disaster in Nigeria have long defiled comprehensive solution especially as there are many
unresolved issues on the management of oil spill disaster. The issues can be briefly described as
follows; (1) Oil spill takes time before it is detected and reported to the appropriate agencies.
(2) The response time is too long to allow effective quick cleanup.
(3) Substantial parts of oil spill are caused by act of sabotage and vandals in attempts to claim
damages.
(4) The methods of cleanup and emergency response are not only obsolete they are ineffective.
(5) There are discrepancies in the claim of communities and the estimated damages from the
operating agencies.
(6) There are suspicion by the host communities of the possible cover up of spill by oil
companies (and thus avoid heavy compensation) if the latter (oil companies) want to respond
promptly to oil spill.
(7)The nature of terrain and the characteristics of oil spill areas cannot be ascertained by the oil
companies to send clean up team on time and to fix the price of spill clean up
(8) There is mistrust from the oil companies on the integrity of their contract staff (whom they
accused of framing oil spill to claim allowance).
(9)New and emergency villages spring up at the oil spill site overnight in order to claim
damages.
FATE AND EFFECTS OF SPILLED OIL
This section describes the properties and behavior of spilled oil that are important to a spill
response operation, and the potential effects that the spilled oil and associated response
operations may have in the various environments encountered in the project area.
FATE OF SPILLED OIL
The chemical composition of oil changes due to weathering. Weathering occurs by evaporation,
microbial degradation, chemical oxidation, and photochemical reactions. Some oils weather
rapidly and undergo extensive changes in character, whereas others remain relatively unchanged
over long periods of time. The effects of weathering are generally rapid (1 to 2 days) for
hydrocarbons with lower molecular weights as a result of evaporation. Degradation of the higher
weight fractions is slower and occurs primarily through microbial degradation and chemical
oxidation. The weathering or fate of spilled oil depends on the oil properties and on
environmental conditions. It is important to recognize the dynamic nature of spilled oil and the
fact that the properties of spilled oil can change over time. During a response operation, it is
important to monitor the continuous changes in the properties of the spilled oil, as response
strategies may have to be modified.
(1) Properties; Crude or refined oils vary in their physical and chemical characteristics. These
characteristics affect their volatility, toxicity, weathering rate and persistence. These
characteristics include; (2) Specific gravity (density); Determines if the oil will float on water or
sink. The specific gravity of most crude and refined oils lies between 0.78 and 1.00. The U.S.
petroleum industry has customarily used the so-called °API (Degrees API Gravity). API gravity
is inversely proportional to the true specific gravity and corrects the specific gravity value to
15.5ºC (60ºF), so that on the API scale, freshwater has a specific gravity of 10.00. Light oils with
a low specific gravity (<0.8) have high values on the API Scale (>45), whereas heavier oils have
low API gravity values. The °API gravity places most oils within a convenient range of 10 – 50
°API. The specific gravity of spilled oil will increase with time, as the more volatile (and less
dense)
(3) Pour point — the lowest temperature at which the oil will flow, below which the oil will act
as a semi-solid substance. As ambient air temperatures vary, stranded oil may be alternately fluid
or semi-solid. This property is important in evaluating whether oil will penetrate into sediments
or move down slope.
(4)Viscosity — a measure of the resistance of the oil to flow, or its internal cohesion, that
controls the rates of spreading and the degree to which oil can penetrate into sediments. Low
viscosity oils are light and fluid whereas high viscosity oils are semisolid or tarry. Estimated
viscosity at 70º F of Chad crude is 400–1000 cp (similar to Bunker C).
H 2S unlike other sulphur compounds in crude oils, which tend to accumulate in the
distillation residue, hydrogen sulphide is evolved during distillation or other heating
processes. During an oil spill, this makes it a safety concern, as hydrogen sulphide is a
toxic gas with a time-weighted average (TWA; an 8-hr. exposure limit established by
ACGIH) exposure limit of 10 ppm and a short-term exposure limit (STEL) of 15 ppm
(ACGIH, 1996). Other oil properties to be considered during a response include boiling
point, flash point, surface tension, adhesion, solubility and aromatic content.
Boiling point — determines the temperature at which each hydrocarbon will evaporate.
Many of the light (low boiling) fractions (“light ends”) evaporate at temperatures less
than 20ºC (68ºF). As these light fractions evaporate, the remaining oil is reduced in
volume and becomes denser and more viscous.
Flash point — the lowest temperature at which the fractions of the oil will ignite when
exposed to an ignition source. This is a critical safety parameter; it must be remembered
that a serious hazard may exist if air temperatures are above flash points of light fractions
in spilled oils. Gasoline and other light fuels can be ignited under most ambient
conditions and therefore pose a serious hazard when spilled. Many freshly spilled crude
oils also have low flash points until the lighter components have evaporated or dispersed.
Surface tension — controls the rate at which the oil will spread. Oils with a low surface
tension spread more rapidly, so that a greater surface area is exposed to weathering.
Surface tension is partially controlled by ambient temperatures and decreases as
temperatures increase.
Adhesion — is important in determining whether the oil will stick to sediments or other
materials it comes in contact with.
Solubility — determines if oil will dissolve in water and become toxic to marine life.
Aromatic content — aromatics are more toxic, have a high solubility that may increase
toxic effects, and are more volatile than other hydrocarbon components. Again, it is
important to remember that these properties, and the environmental conditions that affect
them, change over time and should continuously be monitored. For example, as oil
weathers due to evaporation processes after a spill, the specific gravity usually increases,
and the evaporation rate increases with increased temperatures and wind speed.
ON-LAND SPILLS
The pipeline will be buried in order to reduce the risk of leaks and to prevent interference with
agricultural lands and wildlife migration routes. Typically, the pipeline will be buried one meter
underground. In some areas, like stream and road crossings, the pipeline may be buried even
deeper.
Oil movement or flow over the ground surface follows the topography of the land (oilflows
downhill). In general, oil will flow until it reaches a surface water body or a depression, or until
sorbent effects prevent further movement. Oil flowing over land can infiltrate vegetation cover
and soil. The rate of oil movement and depth of penetration are dependent on a variety of factors
and are best determined by direct observation. If ground water becomes contaminated,
contaminants generally remain concentrated in plumes. Because ground water moves relatively
slowly, contaminants do not mix or spread rapidly. Contaminants from ground water may
eventually migrate and appear in surface waters. A leak of heated oil from the pipeline at or near
the pump stations would tend to initially flow faster and be more likely to penetrate permeable or
porous materials than leaks from cooler (pipeline) temperature areas of the oil transportation
system. In the case of a spill, the oil flow speed and ability to penetrate into sediments and soils
would decrease as it cooled.
OFFSHORE SPILLS
The fate of hydrocarbons in the marine environment depends on a number of factors, including
air and water temperatures; the type and amount of nutrients and inorganic substances present;
winds, tides, and currents; and the amount of sediment suspended in the water.
MOVEMENT
Currents and wind are the driving forces for the movement of an offshore oil spill. Ocean
currents have three components: the residual current, the tidal current, and the wind driven
surface currents. Currents produced by fresh or brackish water outflow from a river can also
deflect oil away from a river mouth or estuary.
Residual currents are produced by the long-range motion of water in the ocean caused by the
rotation of the earth, the geometry of the oceans, and temperature differences in the ocean. These
rivers of water within the ocean change slowly, although they may have a seasonal variation.
More localized residual currents can occur due to geometric effects of the ocean-land boundary.
Residual currents generally flow in the same direction for long periods of time. Coastal boundary
currents can trap or contain oil close to a shore (Murray and Owens, 1988) or keep oil away from
a shore. Tidally driven ocean currents are produced by changes in water level caused by
astronomical effects. These currents change both their magnitude and direction with every tidal
cycle. In most cases, the tidal flow is symmetrical with time, particularly in deep water. The net
motion of oil due to tidal currents is very low, even for large currents, because tidal currents
oscillate. If an oil slick is spread over regions with varying water depths, tidal currents can result
in a net advection of the oil. This is due to the fact that the currents are stronger in shallow-water
areas and weaker in deep water. Both the direction and magnitude of future tidal currents can be
predicted easily, after measurements have been taken during tidal cycles. The third type of ocean
current is a surface current generated by the interaction of the wind with the water surface (see
also Section 5.1). The speed of these surface currents is 2–4% of the wind speed (Table 4-2), and
motion is approximately in the direction of the wind. This is the only effect of the wind on oil
motion. Wind-produced waves are oscillatory and do not causes net oil movement in deep water.
PRIMARY WEATHERING PROCESSES
When oil is released onto the water surface, its characteristics start to change due to a number of
physical-chemical processes. All of the processes are interactive. Weathering rates depend on oil
type, physical properties such as viscosity and pour point, chemical properties such as wax
content, amount of oil spilled, weather and sea state conditions, and location (whether oil stays at
sea or is stranded). The primary processes affecting the fate of most spilled oil are: Spreading,
Evaporation, Dispersion, Dissolution and Emulsification. These processes dominate in the first
few days to weeks of a spill, and, except dissolution, these processes may dramatically change
the nature of the oil. In addition, a number of longer term processes include the following:
Biodegradation, Photo- and auto-oxidation and Sedimentation. These longer-term processes are
less important than the first five for the initial prediction of the fate of spilled oil, and their
contribution to the oil fate is typically neglected in models. These are, however, more important
in the later stages of weathering and usually determine the ultimate fate of the spilled oil.
SPREADING: Spreading occurs during the early stages of the spill. According to Fay (1971),
there are three stages of spreading. These are:
(1)Phase One: Gravity-inertia: This early phase occurs immediately after the oil has been
released and is driven by gravity. This is simply due to the fact that oil, being a liquid, will not
remain in a pile. The rate at which the oil moves depends on its inertia; that is, the oil needs time,
due to its mass, to move. The process occurs for a few minutes to hours and is generally finished
by the time a spill response is initiated.
(2)Phase Two; Gravity-viscous: This phase also starts immediately after the oil has been
released and is again caused by gravity. In this phase, however, the viscosity retards the rate of
oil motion. That is, light oil will spread more rapidly than heavy oil. The time span for this
process is from minutes to many hours. As other fate processes act on the oil (for example,
evaporation), viscosity increases, and the spreading process slows.
(3)Phase Three; Surface tension-viscous: This is the final phase of spreading and occurs over a
time period of many hours to days. The driving force is the surface tension, a force at the
molecular level that may make the oil spread on the water. The retarding force is the oil
viscosity.
EVAPORATION
Components of spilled oil evaporate at varying rates and are transported and diluted by
atmospheric processes. Evaporation is usually the most important weathering process in the first
days immediately following a spill. Evaporation may be responsible for the loss of one-third to
two-thirds of an oil spill mass within a few hours or a day (Jordan and Payne, 1980). Rapid
initial loss of the more volatile fractions is.
DISPERSION:
Natural dispersion is the removal of oil from the water surface by its incorporation, in the form
of small droplets, into the water column by wave action. The rate of dispersion depends on the
amount of wave energy at the sea surface. For low energy wave conditions, the rate of dispersion
is low. For high sea states, dispersion may dominate with the result that most of the oil is
removed from the water surface in a few hours. The more viscous the oil, the slower the rate of
dispersion. In the water column, oil is present as small droplets and, thus, has a much higher
surface area in contact with the water. This increases the rate of dissolution and the rate of
natural biodegradation. The rates of both evaporation and dispersion increase with increasing
wind and decreasing viscosity. They are thus competing processes in the oil mass balance.
EMULSIFICATION:
Emulsification is the incorporation of water into oil and is the opposite of dispersion. Small
drops of water become surrounded by oil. In order to emulsify oil, external energy from wave
action is needed. In general, heavier oils emulsify more rapidly than lighter oils. The oil may
remain in a slick, which can contain as much as 70% water by weight and can have a viscosity a
hundred to a thousand times greater than the original oil. Water-in-oil emulsions often are
referred to as “(chocolate) mousse”. Due to its high viscosity, emulsified oil is difficult to
remove from the water surface. Emulsion affects the adhesion properties of oil; this dramatically
affects the on-water recovery options, and an oil-in-water emulsion likely will not stick to shore
zone materials.
SUBMERGED OR SINKING OIL
Oil floats as long as it is less dense that the surrounding water. The density of fresh water is
taken as 1.0 and the density of seawater usually is 1.025 (i.e., it is more dense). As oil weathers
due to evaporation processes after a spill, the specific gravity usually increases. Mixing with
sediments also can alter the specific density of oil. This may occur as oil is washed from a beach
and incorporated with sediments by wave action. Oil on the surface may sink if the density of the
water changes. This may occur in coastal waters where different water bodies meet, such as at
density fronts or at inlets and in estuaries. Current speed and temperature can affect floatation.
The same oil that would sink in calm waters (<0.1 knot) likely will remain on the surface in
currents of more than 0.5 knot. In warm or hot climates, as the water in near shore areas warms
and cools each day, oil that has a density close to that of water may sink during the overnight
cooling and rise again during the daytime warm period, creating sinking and refloating cycles.
Natural collection sites for sinking oils include trenches, depressions and eddy areas. It is often
difficult to obtain information on natural subsurface collection sites.
WHERE OIL STRANDS
On sheltered coasts with small waves; most of the oil will be deposited as a thin band in
the middle to upper intertidal zone (in the zone of wave action).
If washed ashore during periods of storm-wave activity, oil can be carried farther up a
beach and deposited in the supratidal zone (above the limit of most wave action); this oil
is stranded and will not be affected by waves until the next period of high water levels.
On impermeable surfaces (bedrock, solid man-made structures), oil remains on the
surface.
On permeable shores (i.e., shores with sediments), subsurface oil can be present due to
burial and/or penetration.
Oil may penetrate below the surface of a beach, depending on the size of the sediment
and the viscosity of the oil. Only light oils (e.g., a diesel) can penetrate a sand or mixed
sand-gravel beach, whereas all but the more viscous oils can easily penetrate into a
pebble-cobble beach.
ON-LAND SPILLS
It is recognized that despite best management practices the potential exists for accidental releases
of vehicle and equipment fluids and oil to occur. The potential for a spill to occur during
operations allows for the possibility that areas near the pipeline could be affected.
Spills of diesel, gasoline, hydraulic, brake, transmission, and other equipment fluids, as well as
other chemicals, could have an impact on vegetation, animals, and local land use activities. They
could also impact water supplies and aquatic resources if they were to enter surface waters or
groundwater aquifers (see Section 4.2.4, Critical Habitats, discussion of shallow aquifers). Spills
of this nature may tend to be isolated and generally occur on access roads, maintenance facilities,
and other areas where vehicular traffic is common. These impacts would be reduced by control
measures. Any incidents that occur would be small, localized, and intermittent. Crude oil spills
could occur in the Oil Field Development Area and along the PTS during the operational life of
the Project. On land impacts would include infiltration of oil into surrounding vegetation cover
and soils. Animals and birds could ingest contaminated vegetation. Disruption of migration
routes and local activities, such as hunting and agriculture, could also occur, especially during
response activities. Attention should be paid to the considerable numbers of animals that move
through the area regularly on their way to livestock markets. The primary concern of a spill on
land would be to prevent it from impacting surface water channels or groundwater aquifers.
IMPACT OF RESPONSE ACTIVITIES
When soils are moved and compacted by heavy equipment, the particle size and porosity can be
altered, important soil components such as mycorrhiza and seeds can be destroyed, and a loss of
soil nutrients by leaching can occur. Mycorrhiza associated with the root systems of many
tropical plants influence nutrient cycling and germination processes. Response activities utilizing
heavy equipment for oil containment or excavating of oiled soil materials (see Section 8) may
cause a mixing of soil layers and movement of organic materials. Once mixing occurs, essential
nutrients could be leached from topsoil by underlying substrates. This impact would be short-
term and limited to the response area. If soil structure and fertility are degraded by repeated
disturbance, re-establishment of the native vegetation may be greatly retarded. An alternate and
less desirable, successional sequence also could occur, resulting in the rapid establishment of
introduced plant species or undesirable weeds. When this occurs, the normal successional
sequence halts or is dramatically slowed and the regenerative capacity of savanna or forest
habitat could be impaired. Weedy shrubs and woody pioneer species readily re-establish
OFFSHORE SPILLS
Despite best management practices the potential exists for accidental releases of oil to occur
from offshore facilities. The potential for an offshore spill to occur during operations, coupled
with the proximity of the FSO to the shoreline, allows for the possibility that the Cameroon
coastline in the vicinity of the FSO could be affected. The coastal characteristics information
presented in the Cameroon EA, Appendix C, was used to help develop an environmental
sensitivity index (ESI) classification system for the Cameroon coastline between the
Cameroon/Equatorial Guinea border at the mouth of the Ntem River to Point Souelaba at the
mouth of the Cameroon Estuary.
MARINE BIOTA
The effects of an oil spill on marine organisms would depend on the organisms exposed, the
conditions of the exposure, the volume of oil spilled, and other variables at the time of the spill.
Response activities may also affect organisms. Sediment suspension due to disturbance during
response activities could impact the near-shore biota; however, the marine organisms in the FSO
area are well adapted to turbid waters. An oil spill could have potential effects on marine
mammals. Sublethal effects such as changes in normal migration routes and in behavior could
also occur; however, there is a general lack of marine mammal populations in the study area
(none were observed during marine field investigations). Fish could be susceptible to effects of
spilled oil. While juvenile and adult fish would be able to avoid oily areas, the near-surface eggs
and larvae of many species would not be able to do so due to their lack of mobility. Therefore,
these early life stages generally are more susceptible to oil spill impacts. Fish can be affected
indirectly by spilled oil due to death of prey species, or through an effect on reproduction.
Because of the widespread geographic distribution and large reproductive potential of most fish
species, however, recovery from potential impacts as a result of an oil spill is expected to be
rapid. Fishing is a primary economic activity in the proposed project area. Commercial and/or
subsistence fishing could be temporarily halted to avoid harvesting organisms potentially tainted
with oil, or to avoid contamination of boats and gear with oil. Deaths of birds could result from
oil coating their plumage and possibly from the toxic effects of ingesting oil. Certain birds would
be particularly susceptible because they float on the water and dive for food. Sublethal effects
from exposure to spilled oil may also contribute to increased mortality rates under certain
environmental conditions. Although some reduction of phytoplankton productivity could occur
as a result of an oil spill, the impact on phytoplankton populations is expected to be less than
significant because of the widespread distribution and large reproductive potentials of
phytoplankton. Zooplankton could also be affected directly by increased mortality or indirectly
through a decrease in food supply and changes in behavior, respiration, and reproduction.
BENTHOS; The largest impact of an oil spill on the benthic biota probably would result if the
oil sank and coated the bottom. The more toxic, lightweight components probably would have
evaporated or dissolved into the water before the oil reached the bottom. A direct effect would be
mortality from smothering, although some mobile organisms would probably be able to move
through this material. However, for most oil spills, coating of benthic biota has not been
observed.
SANDY INTERTIDAL HABITAT
The physical effects of spilled oil probably would be more significant than chemical toxicity to
the sandy beach biota. By the time the oil reached the shoreline, the more toxic fractions would
likely have evaporated or dissolved. Because of the high-energy nature of sandy beaches, the
residence time of oil is usually short, about one to two tidal cycles. Sandy beaches in the study
area generally have few species, and these species characteristically have a high turnover and
wide geographic distribution. Under these conditions, biotic recovery to pre-spill conditions
would likely occur within one to two years.
ROCKY INTERTIDAL HABITAT
Rocky intertidal habitats in the study area generally support a greater biomass and variety of
plants and animals than do sandy beach habitats. As in the sandy beach habitats, physical effects
of oil would be more likely to cause harmful impacts than would chemical toxicity. Both direct
and indirect effects of spilled oil on rocky habitat organisms could occur. Direct effects include
mortality due to smothering; indirect effects include behavioral changes due to the coating of the
substrate. Although local, short-term impacts could be significant long-term impacts are typically
rare for these habitats. The high-energy nature of the environment generally leads to a relatively
rapid recovery of available habitat and decolonization by most species. Recovery to pre-spill
conditions would likely occur within one to three years.
TOURISM/RECREATIONAL BEACH USE
An oil spill that reaches the beaches could halt the tourism/recreational use of beaches until
cleanup had been completed.. While a decline in tourism might be felt by local population
centers most affected by a spill, the overall level of tourism in the event of a large spill in the
region would be expected to remain relatively stable. Thus, the short term impacts of an oil spill
on tourism/recreation beach use could be significant in the areas affected by the spill; however,
the longer-term impacts would be mitigated by the cleanup.
POTENTIAL IMPACTS DUE TO RESPONSE
Commercial and/or subsistence fishing could be interrupted as a result of fishing vessels being
confined to port by oil containment booms.
RIVER SPILLS
Spills during construction or resulting from pipeline releases at river crossing may lead to oil
impacts on rivers in Chad or Cameroon. In marine oil spills, it is very unusual to consider the
water itself as a resource to be protected. Spilled oil may move over or through the water, but the
water itself is not usually thought to be damaged. For inland spills this is not true. In many cases,
the water is used as a primary resource (potable water) and threats to the water supply are a
public health problem, immediately escalating the level of concern in river spills. If spills are
allowed to enter surface waters, the decrease in water quality following such an event could also
adversely affect botanical, wildlife, and other aquatic resources. Crude oil is generally lighter
than water and floats on the surface, potentially coating or causing impact to animals and plants
that it may contact. While these impacts could be significant, their likelihood of occurrence
would be minimized by the implementation of oil spill response countermeasures and associated
safety and environmental protection measures. Streams and rivers in the project area appear to
support relatively small populations of fish, invertebrates, and other organisms. In the Nanga
Eboko area fishing is mostly on the Sanaga and in small streams. Fishing is less important in
streams and rivers elsewhere in the project area. As in marine spills, the nature of the shoreline
will determine the amount of potential damage that a spill could cause. The flat gradients of the
rivers in southern Chad allow development of extensive sandbanks that attract winter migrant
wading birds as well as local black-crowned cranes (Balearica pavonina), Maribou storks
(Leptoptilus crumeniferus), herons, egrets, and plovers. The vertical, sandy banks are well suited
for colonies of Carmine bee eaters (Merops nubicus) and red-throated bee eaters (M. bulockii).
Flooding can strand pollution at high levels and threaten larger areas than might otherwise be
expected. During a flood event, high water could transport oil into overbank habitats and impact
large areas of the floodplains. Agricultural crops and grazing lands may be affected during these
situations. Floodplains also are recognized as being important historically as fish nursery sites in
Benech and Leveque (in Burgis and Symoens, 1987). The impacts of spill response activities to
these areas would be similar to those for on-land spills. Effects of response operations on
botanical resources could include direct disturbance to, or loss of, individuals or populations of
plant species. Temporary and permanent loss of riverine (gallery) vegetation could occur during
disruptive response operations on the Nya, Loulé and Pendé river floodplains. Erosion and
sediment transport would be minimized during response by the use of prudent erosion control
practices.
CRITICAL HABITATS
Pipeline routing and facility sitting has been undertaken to avoid various biologically important
locations near the project area, including:
Important wildlife habitats in the Faro Reserve.
The Laramanay Wildlife Reserve; a proposed hunting reserve approximately 7 km north
of the proposed pipeline route, east of Bam and Bégangber (see Figure A-1, Appendix
A), which is reported to contain important habitat for elephants that may migrate between
Chad and Cameroon.
The Logon floodplain is a wetland area that contains valuable gallery forest and marsh
habitat that supports relatively diverse bird and mammal populations and provides
important grazing habitat for resident and trans-human livestock.
A large contiguous stand of African bamboo (Oxyanthera abyssinica) northeast of
Bessao contains important timber and fuel wood resources for local residents and also provides
important elephant habitat. This is not currently an official reserve, though it is a recognized area
of value to local residents.
SHALLOW AQUIFERS
Shallow aquifers of the Doba Basin provide almost all of the water supplies for the population of
the area. The most common domestic water supply source is through wells or occasional hand
pumps. Some of the traditional hand dug wells have little protection against surface runoff, and
spilled oil flowing on the ground surface in their vicinity could infiltrate these wells. Some of
these wells are located in the floodplains of nearby streams, are only 5 to 8 m deep, and
presumably capture water of the same or similar quality as that contributing base flows to the
streams in the area. The groundwater gradient follows the topographic slopes. A groundwater
contour map for the upper shallow zones of the aquifer is included as Figure 6.4-3 in the Chad
EA. The data indicate that the direction of shallow groundwater flow in the vicinity of the Komé
and Bolobo well fields is toward the north and northeast, i.e., toward the Nya River, and toward
the east in the vicinity of the Miandoum well field. The clay and silty surface soils within the
project area should form a barrier to the aquifers from above.
ENDANGERED AND SENSITIVE SPECIES
The only significant biological habitats remaining in the vicinity of the oil field development
area and pipeline in Chad consist mainly of remnant gallery forest and herbaceous wetland
vegetation in the alluvial floodplains of major watercourses, and occasional stands of African
bamboo (Oxyanthera abyssinica) in the region around Bessao and Baibokoum. The pipeline has
been routed to avoid large stands of bamboo. The Mbéré Rift Valley supports a great variety of
animals, including large mammals. A large portion of the Mbéré Rift Valley in Cameroon
(comprising approximately 60 km of the 320 km pipeline route) is unique in its relative lack of
disturbance. It has a high diversity and abundance of wildlife, including elephant, hippopotamus,
bongo, and eland, and little-disturbed diverse vegetation including wooded savanna and gallery
forest. Response activities are expected to have little impact on those wildlife resources that
remain in the area. Agricultural activity has long since displaced most of the natural habitats and
associated wildlife of the region. Temporarily disturbed areas could be re-colonized and
repopulated by the same species, but probably not by the same individuals, depending on the
degree and extent of disturbance. Such differences could affect the ability of certain species to
return and persist in remaining natural habitat fragments. Consequently, a limited number of
individuals could be affected during response operations. The following regionally sensitive
mammal species have the potential to occur in the study area (see EAs for details).
Giant eland (Tragelaphus derbianus gigas) — formerly occurred in SW Chad in the
wooded savanna zone. It may be completely absent from Chad today.
Red-flanked duiker (Cephalophus rufilatus) - This small antelope species was restricted
to gallery forests in the wooded savanna zone of Logon Oriental and Moyen Chari
prefectures. The population, if it exists, does not appear to be large.
Grey duiker (Sylvicapra grimmia) -This small antelope species was, until recently,
widespread throughout the savanna zone of southern Chad. Its total population today is
not thought to be abundant overall.
Bushbuck (Tragelaphus scriptus) -This species normally is confined to areas with
sufficient cover near permanent water (i.e., gallery forest). Once locally common, total
numbers today are unknown.
Buffon's or western kob (Kobus kob) -This species occurs along permanent watercourses
within the savanna zone. It may still possibly occur on isolated floodplains in less
populated areas.
Roan (Hippotragus equinus) -This species exists in moderate numbers throughout most of
the savanna zone of southern Chad, but has been eliminated from densely populated
regions.
Oribi (Ourebia ourebi) -This species was once widespread in the southern savannas of
Chad, south of latitude 11º north.
African elephant (Loxodontia africana) -Some elephant habitat exists within the
Laramanay Reserve, and there may be some use of this area by seasonally migrating
elephants. Elephants occur in the Mbéré Rift Valley, the forest in the region east of the
Sanaga River, and in the vicinity of the Campo Reserve in Cameroon.
African linsang (Poiana richardsonii) -This species appears to be very rare in the
Cameroon Atlantic littoral evergreen forest and are threatened by continued hunting
pressure.
Gorillas -while uncommon, can be observed in the Semideciduous Forest off the road
between Deng Deng and Bélabo.
The following sensitive bird species have the potential to occur in the study area:
River prinia (Prinia fluviatilis)-This bird species was known only from waterside
Vegetation in a few localities in southern Chad (Chappuis, 1974). It prefers marshy
Floodplain vegetation for nesting and foraging.
The Mbéré Rift Valley is not exceptionally rich in bird species, but it is possible to find
several species of eagle. The rare Abyssinian calao might be present in the zone, as well
as the big bustard.
In addition to the above, there are wildlife species whose status in Chad is thought to be
reasonably secure at present, either within or outside existing parks. These species are
partially protected under Article 25 of Chadian Wildlife Legislation. They include:
Antbear, Aardvark (Orycteropus afer) -The status of this species is uncertain. It is a
nocturnal animal relatively widespread in savanna areas where termite species occur.
Serval (Leptailurus serval) - This felid is a hardy survivor in floodplains and near rivers.
All vultures (Gyps and related genera) — All species currently appear to be stable, but
the white-headed vulture (Gypohierax angolensis) is the least common.
Cattle egret (Bubulcus ibis), little egret (Egretta garzetta), yellow-billed egret (Egretta
Intermedia), and great white egret (Casmerodius alba) — These species are widespread to
occasional along rivers.
Marabou stork (Leptoptilus crumenifer) — This species is common near water.
Saddlebill stork (Ephippiorhynchus senegalensis) — This species is occasionally found
along rivers, lakes, and open flooded areas.
Borassus aethiopum — a threatened endangered tree.
Some species are still numerous in the Semideciduous Forest areas of Cameroon, buare
beginning to decline in numbers. These include the bongo (Boocercus euryceros),blue
duiker, chevrotain, water chevrotain, several monkey species (e.g., potto, galago,
colobus, and chimpanzee), African ground squirrel (Euxerus erythopus), caracal, serval
(Felis serval) and golden cat (Felis aurata). This decline is due to hunting pressure and
loss of habitat from human activity. The warthog is not seen frequently and lion, leopard,
and spotted hyena, though once present, apparently have disappeared from the region.
ARCHAEOLOGICAL AND SACRED SITES
Sacred sites would pose a problem because they are not identified easily by outsiders.
On the other hand, local people state that they would be more than willing to identify such sites
to contractors in advance of response work crews and to move sacred objects to new sites
whenever possible. There is a strong prohibition against the disturbance of physical remains
(buried in household compounds; in most villages, cemeteries are reserved for the burial of
“strangers”). If absolutely necessary, ancestral remains may be moved to another site. This,
however, has to be carried out in close consultation with the owners of the remain sand be
accompanied by certain rituals that should be performed by the descendants themselves. Another
issue involves local religious beliefs. Many areas are considered to merit “special handling”. In a
fishing village in the peri-urban area of Kribi, for example, a water spirit is believed to exist that
needs regular appeasement. In other areas, forest spirits frighten people from certain areas and
cast their curses on individuals who might try to dare the spirits. The appeasement of spirits
involves certain essential rituals that are performed by the local “notables”. In most of the “spirit
culture” areas, locals believe that if projects do not do “what is necessary” they are doomed to
fail. An implication of this sort of belief is that if these rituals are not performed in the manner
considered adequate by the local know how, project-related accidents, no matter how minor, are
likely to be attributed to spirits that are “taking revenge” on those who showed them disrespect.
It is estimated that half of the labor force may refuse to work if accidents are attributed to the
violation of certain rituals, especially if they feel physically or spiritually threatened. It is
essential to note that most sacred areas are neither clearly marked nor easily identifiable. In fact,
they might be known only to the very small groups that perform their rituals there; it is therefore
important to verify the presence of such places in each area when making response operations
decisions.
TREATMENT OIL SPILLAGE
Methods for cleaning up include:
BIOREMEDIATION ACCELERATOR:
Bioremediation: use of microorganisms or biological agents to break down or remove oil.
Oleophilic, hydrophobic chemical, containing no bacteria, which chemically and physically
bonds to both soluble and insoluble hydrocarbons. The bioremediation accelerator acts as a
herding agent in water and on the surface, floating molecules to the surface of the water,
including solubles such as phenols and BTEX, forming gel-like agglomerations. Undetectable
levels of hydrocarbons can be obtained in produced water and manageable water columns. By
over spraying sheen with bioremediation accelerator, sheen is eliminated within minutes.
Whether applied on land or on water, the nutrient-rich emulsion creates a bloom of local,
indigenous, pre-existing, hydrocarbon-consuming bacteria. Those specific bacteria break down
the hydrocarbons into water and carbon dioxide, with EPA tests showing 98% of alkanes
biodegraded in 28 days; and aromatics being biodegraded 200 times faster than in nature they
also sometimes use the hydro fireboom to clean the oil up by taking it away from most of the oil
and burning it.
BURNING
Controlled burning can effectively reduce the amount of oil in water, if done properly. But it can
only be done in low wind, and can cause air pollution. Burning of oil can actually remove up to
98% of an oil spill. The spill must be a minimum of three millimeters thick and it must be
relatively fresh for this method to work. There has been some success with this technique in
Canada. The burning of oil during the Gulf War was found not as large a problem as first thought
because the amount of pollution in the atmosphere did not reach the expected high levels. Field-
testing is needed to check.
USE OF DISPERSANTER
Dispersants act as detergents, clustering around oil globules and allowing them to be carried
away in the water. This improves the surface aesthetically, and mobilizes the oil. Smaller oil
droplets, scattered by currents, may cause less harm and may degrade more easily. But the
dispersed oil droplets infiltrate into deeper water and can lethally contaminate coral. Recent
research indicates that some dispersants are toxic to corals. Watch and wait: in some cases,
natural attenuation of oil may be most appropriate, due to the invasive nature of facilitated
methods of remediation, particularly in ecologically sensitive areas such as wetlands. ; Dredging:
for oils dispersed with detergents and other oils denser than water. ; Skimming: Requires calm
waters.
SOLIDIFYING: Solidifiers are composed of dry hydrophobic polymers that both adsorb and
absorb. They clean up oil spills by changing the physical state of spilled oil from liquid to a
semi-solid or a rubber-like material that floats on water. Solidifiers are insoluble in water,
therefore the removal of the solidified oil is easy and the oil will not leach out. Solidifiers have
been proven to be relatively non-toxic to aquatic and wild life and have been proven to suppress
harmful vapors commonly associated with hydrocarbons such as Benzene, Xylene, Methyl Ethyl,
Acetone and Naphtha. The reaction time for solidification of oil is controlled by the surf area or
size of the polymer as well as the viscosity of the oil. Some solidifier product manufactures
claim the solidified oil can be disposed of in landfills, recycled as an additive in asphalt or rubber
products, or burned as a low ash fuel. A solidifier called C.I.Agent (manufactured by C.I.Agent
Solutions of Louisville, Kentucky) is being used by BP in granular form as well as in Marine and
Sheen Booms on Dauphin Island, AL and Fort Morgan, MS to aid in the Deepwater Horizon oil
spill cleanup.
VACUUM AND CENTRIFUGE: Oil can be sucked up along with the water, and then a
centrifuge can be used to separate the oil from the water - allowing a tanker to be filled with near
pure oil. Usually, the water is returned to the sea, making the process more efficient, but
allowing small amounts of oil to go back as well. This issue has hampered the use of centrifuges
due to a United States regulation limiting the amount of oil in water returned to the sea.
Equipment used includes (1) Booms: large floating barriers that round up oil and lift the oil off
the water.It’s easier to clean-up oil if it’s all in one spot, so equipment called containment booms
act like a fence to keep the oil from spreading or floating away. Booms float on the surface and
have three parts: a ‘freeboard’ or part that rises above the water surface and contains the oil and
prevents it from splashing over the top, a ‘skirt’ that rides below the surface and prevents the oil
from being pushed under the booms and escaping, and some kind of cable or chain that connects,
strengthens, and stabilizes the boom. Connected sections of boom are placed around the oil spill
until it is totally surrounded and contained
(2) Skimmers: Skimmers are machines that suck the oil up like a vacuum cleaner, blot the oil
from the surface with oil-attracting materials, or physically separate the oil from the water so that
it spills over a dam into a tank. Much of the spilled oil can be recovered with skimmers. The
recovered oil has to be stored somewhere though, so storage tanks or barges have to be brought
to the spill to hold the collected oil. Skimmers get clogged easily and don’t work well on large
oil spills or when the water is rough.
(3) Sorbents: These are materials that soak up liquids by either absorption or adsorption. Oil
will coat some materials by forming a liquid layer on their surface (adsorption). This property
makes removing the oil from the water much easier. This is why hay is put on beaches near an
oil spill or why materials like vermiculite are spread over spilled oil. One problem with using
this method is that once the material is coated with oil, it may then be heavier than water. Then
you have the problem of the oil-coated material sinking to the bottom where it could harm
animals living there. Absorbent materials, very much like paper towels, are used to soak up oil
from the water’s surface or even from rocks and animal life on shore that becomes coated with
oil.
(4) Chemical and biological agents: helps to break down the oil Chemicals, such as detergents,
break apart floating oil into small particles or drops so that the oil is no longer in a layer on the
water’s surface. These chemicals break up a layer of oil into small droplets. These small droplets
of oil then disperse or mix with the water. The problem with this method is that dispersants
often harm marine life and the dispersed oil remains in the body of water where it is toxic to
marine life.
(5) Vacuums: remove oil from beaches and water surface
(6) Shovels and other road equipments: typically used to clean up oil on beaches
B. PRODUCED WATER ; Water is very often found together with petroleum in the reservoirs
where the water, as a consequence of higher density than oil, lays in vast layers below the
hydrocarbons in the porous reservoir media. This water, which occurs naturally in the reservoir,
is commonly known as formation water. After oil and gas production has been occurring for a
time, the formation water will reach the production wells and water production will initiate. The
well water-cuts will normally increase throughout the whole oil and gas field lifetime, such that
when the oil production from the field is shut down, the oil content can be as low as a couple of
percent with ninety eight percent water. To maintain the hydraulic pressure in the petroleum
reservoir, which is reduced as soon as production is started, seawater is commonly pumped into
the reservoir water layer below the hydrocarbons. This pressure maintenance due to water
injection causes high extensions in recoverable hydrocarbons but simultaneously contributes to
increased water production.
PRODUCED WATER COMPOSITION: The compositions of formation water originally in
place vary significantly in characteristics between the different reservoirs. As field production is
initiated, produced water composition from the production wells may be continuously
transformed due to injection of seawater, reinjection of produced water, reservoir stimulation,
bacterial activity, introduction of production chemicals and more. Produced water is basically a
mixture of formation water and injected water but also contains smaller quantities of: Dissolved
organics (included hydrocarbons), Traces of heavy metals, Dissolved minerals, Suspended oil
(non-polar), Solids (sand, silt) and Production chemicals. Dissolved hydrocarbons are found
naturally in formation water and can be both toxic and bio-accumulative. Such water-soluble
components, which in produced water are mainly BTEX (benzene, toluene, ethyl benzene and
xylene), polyaromatic hydrocarbons (PAH) and alkylphenols, are together with heavy metals
considered the most harmful contaminants in produced water.
PRODUCED WATER IMPACT ON THE ENVIRONMENT
The most common practice in use in the North East Atlantic for management of produced water
is treatment in gravity based separation equipment and discharge to sea. For a long time the only
governmental regulation for produced water discharges in this petroleum sector has been
concerning concentration of non-polar oil in water (OIW). Little attention has been given to
dissolved organics. There is now wide agreement within the petroleum industry, governments
and scientists that focus should now be put on dissolved organic components, heavy metals and
production chemicals. The oil in water content shall be as low as possible and the industry shall
make use of best available technology (BAT). The quantity of produced water in Figure 3 that is
not discharged to sea is re-injected into the reservoir or to another formation suitable for
disposal. The long-term effects of such contaminants on the environment are not fully
documented and understood. Some research programmed is completed and several new studies
are underway to map possible consequences for living organisms. Dilution aspects and
movement of species in the oceans makes definite conclusions hard to make. There are so many
variable that the modelling is extremely complex. Results from recent research show however
that fish exposed to alkyl phenols have disturbances in both organs and fertility. These results are
serious and have triggered further investigations.
1 CONVENTIONAL TECHNOLOGY FOR WATER TREATMENT
During petroleum production, vast volumes of liquids have to be managed each day. Deferred
production causes high economical losses and therefore continuous operations are always strived
for. The capacity, reliability and performance of the produced water management system is often
critical for continuous oil production particularly in mature oil field where the water production
can greatly exceed the oil production. The water production system needs to be designed to
receive continuously increasing quantities of water as oil production continues.
2 GRAVITY BASED SEPARATION - FLOTATION
Produced water treatment has traditionally taken place in gravity based equipment, where the
difference in the density of the two liquids to be separated is utilized. Such separation is
commonly performed in huge horizontal tanks at different pressures. Flotation of the lighter
components (oil) can be enhanced by means of finely distribute solution (pressure reduction) and
parallel plate packages installed diagonally in the separation vessel.
3 SEPARATION TECHNIQUES BASED ON FILTRATION
A well known technique for separating non soluble components is by filtration. Several
principles for handling produced water have been considered including microfiltration
membranes and media filters. Such treatment technologies are potentially advantageous because
of very good separation degrees can be achieved. However microfiltrations have found very
limited practical application because of cost and poor operability, very high energy consumption
and degradation of the filters elements with use.
4 CYCLONIC SEPARATION METHODS
The continuous demand for higher treatment capacity in very limited space has resulted in
improved treatment methods. The most commonly used technology in offshore production since
around 1990 is the static hydro cyclone that utilizes available pressure for enhanced speed in
gravity separation. The advantages for this equipment type are high reliability (no moving parts),
low maintenance, requires very little space, and gives good separation effect and high capacity
shows the water (red) going out in the underflow, while oil (blue) is forced into the middle and
led out in the cyclone overflow. Another application for separation of oil and water is high-effect
centrifuges. Because the device is motor driven it is often used for low pressure water streams.
This kind of equipment has high energy and higher maintenance requirements
NEW CHALLENGES IN HANDLING PRODUCED WATER
Gravity based separation techniques have together with static hydro cyclones been the most
extensive method for treating produced water. Other types of equipment have also been utilized,
mostly in special cases with difficult operating treatment characteristics or small volumes,
though to a less extent. Even if produced water systems more or less have functioned as intended
with respect to the design specifications, the future has brought new considerations regarding
what is sufficient treatment. A good alternative for disposal of produced water would be to send
it back into the reservoir where it came from as part of the pressure support, or to another
suitable formation. Unfortunately this requires extensive treatment prior to re- injection and due
to high costs it is an economically viable alternative mainly for fields with large water
production. Reinjection could also cause degradation of the reservoir production quality and
productivity.
RECENT PRODUCED WATER TREATMENT DEVELOPMENTS
As there is still no economically practically method for disposal of all the produced water via re-
injection or various recycle methods, a range of innovative wastewater technologies have been
developed or are under development. The different technologies all have their operating
characteristics that make them suitable for only certain produced waters or operating
characteristics. There is a major focus on new technique to remove dissolved components from
produced water.
1SEPARATION BY FILTRATION
Utilization of membranes has been considered for treatment of oily wastewater to reduce
dissolved components. The new systems include the use of nano filtration membranes. However,
although the filtration method has very good separation effect, the high costs and complexity of
these treatment techniques means that applications are only experimental.
2 WATER TREATMENTS BY EXTRACTION
Another technology that has been widely tested on both pilot and full scale on the Norwegian
continental shelf is rooted in the solvent properties of supercritical liquids (CTour). The process
utilizes liquid condensate (NGL) from the gas scrubbers and injects it into the produced water
upstream of the hydro cyclones. The dispersed and dissolved hydrocarbons, which have higher
solubility in the condensate, go into the condensate phase and are separated in the hydro
cyclones. This equipment has undergone extensive pilot testing and its field tests are imminent.
The process is very sensitive to the available condensate quality.
3 ENHANCED OIL SEPARATIONS BY MEANS OF COALESCENCE
Several modern produced water treatment methods are based on the coalescing of dispersed oil
droplets, often prior to cyclonic separation. The devices are installed upstream of the cyclonic
vessels to increase oil droplet diameters which will result in better separation degree in the hydro
cyclones. The process of coalescence could be accelerated by different means. One method is to
install a special fiber media in the pipelining or the hydro cyclone vessels that attracts oil
droplets and promotes coalescence into larger aggregates. These systems have no effect on
removing dissolved hydrocarbons, but are simple and easily retrofitted. The fiber media is
sensitive to fouling and any abrasive elements (sand) in the water. Other processes include
combinations of chemical injection (coagulation/flocculation) and mechanical agitation in
specially built vessels. Compact flotation units are hybrid cyclone/degassers that could replace
standard degasser equipment.
4 METHODS BASED ON ADSORPTION
Adsorption has proven a successful area in maintaining compliance with produced water
discharges. Unfortunately most processes involve filters and therefore are restricted in volume or
require advanced regeneration processes which could be both energy demanding and expensive.
The adsorption techniques include activated carbon filters with regeneration by wet air oxidation
and oil-adsorbing media canisters based on resins, polymer and clay technologies
5THE NATURE TECHNOLOGY SOLUTIONS
Nature Technology Solution (Nature) provides state of the art treatment and management of
most kinds of contaminated wastewater. Nature is delivering services and equipment for efficient
handling of polluted wastewater from onshore, shipping and the offshore industry Nature offers a
range of physical, chemical and biological treatment methods for industrial wastewater.
THE NATURE PROCESS FOR PRODUCED WATER TREATMENT
The Nature process for treatment of produced water is based on addition of patented
coagulant/flocculants in existing or partially modified water systems. The agent is injected into
the produced water upstream a static mixer or various process equipment (pumps, valves etc.) to
provide sufficient in- mixing. The agent separates dispersed and dissolved hydrocarbons and is
floated and skimmed off in a flotation vessel downstream the in-mixing point.
THE NATURE PROCESS – Why Advantageous?
The Nature process combines coalescence and adsorption and significantly reduces dissolved
and dispersed hydrocarbons from produced water to less than 5 ppm. The Nature process utilizes
documented non- hazardous agents for professional treatment of oily produced water.
Implementation of new process equipment is usually not needed. The Nature technology
provides excellent water handling at low capital and operating costs. Rapid processing time
promotes small, less heavy and more compact treatment facilities.
NATURE EXPERIENCE WITH PRODUCED WATER
Nature technology has achieved good results in separating both polar (dissolved) and non-polar
(OIW) hydrocarbons from several produced water types from the Norwegian continental shelf.
Produced water from the Shell operated Draugen installation was treated with Nature coagulant
in the spring 2002. The OIW concentration was 93 ppm before treatment with nature coagulant.
Three different doses were used during fixed in- mixing and flocculation time of 150 and 120
seconds respectively. Draugen salinity was measured to < 3.4 %. Produced water temperature
was 50 °C. Figure 7 presents reduction of OIW following treatment with three different doses
Nature coagulant CF – 200 (dry The produced water temperature and salinity was 80 °C and 3,6
% respectively. The OIW concentration in the Statfjord C produced water was 19 ppm before
treatment with Nature coagulant. Three different doses of Nature coagulant CF – 200 (dry solid)
were added to the water. Four tests were performed on disposal well water at 50 °C. In- mixing
and flocculation periods were set to 60 and 120 seconds respectively. The water sample from the
disposal pit had such low oil in water concentration (2 ppm) that further testing was cancelled.
The salinity in the Kuwait produced water was quite high, measured to 10 % salt concentration.
C. SLUGE
Crude oil is a major source of energy and feedstock for petrochemicals. Oily sludge, bio-sludge
and chemical sludge are the major sludge generated from the processed sand effluent treatment
plants of the refineries engaged in crude oil refining operations. Refineries in India generate
about 28,220tons of sludge per annum. Various types of pollutants like phenols, heavy metals,
etc. are present in the sludge and they are treated as hazardous waste. Oily sludge, which is
generated in much higher amount compared to other sludge, contains phenol (90-100 mg/kg),
nickel (17-25 mg/kg), chromium (27-80 mg/kg), zinc (7-80 mg/kg), manganese (19-24 mg/kg),
cadmium (0.8-2 mg/kg), copper (32-120 mg/kg) and lead (0.001-0.12 mg/kg). Uncontrolled
disposal practices of sludge in India cause degradation of environmental and depreciation of
aesthetic quality. Environmental impact due to improper sludge management has also been
identified. Salient features of various treatment and disposal practices have been discussed.
Findings of a case study undertaken by the authors for Numaligarh Refinery in India have been
presented. Various system alternatives have been identified for waste management in
Numaligarh Refinery. A ranking exercise has been carried out to evaluate the alternatives and
select the appropriate one. A detailed design of the selected waste management system has been
presented. Sludge generation and management. The major sludge generated from the refineries is
oily sludge, bio sludge and chemical sludge. Sources of sludge generation in refineries have been
depicted in Fig. 2. Oily sludge is usually generated during cleaning operations of crude oil tanks.
In Indian refineries, tanks are usually cleaned once in 4 to 5 years. Oily sludge is also generated
when oily wastewater is treated in an American Petroleum.(1) Biological sludge is usually
generated during biological treatment of waste water. It is obtained from trickling filter and
clarifier unit. Solutions of sodium hydroxide are used primarily to wash the hydrocarbon
products in order to remove dissolved sulphides, mercaptans, phenolic and other acidic
compounds. (2) Chemical sludge is generated during the treatment of caustic treated effluent
with ferric chloride and polyelectrolyte. The quantity of sludge generation depends on various
factors, for example the characteristics of crude oil, effluent and sludge treatment process
involved, etc. The total quantity of sludge generated in Indian refineries is about 28,220
tons/year. In order to meet the growing demands for petroleum products, most of the refineries
are being expanded and new refineries are being set up. The total capacities of the plant after
expansion and future sludge generation scenarios have been depicted. In the refineries in India
oily sludge from wastewater treatment plant is usually stored in lagoons. Oily sludge from the
crude oil tank and the dried sludges from lagoons are disposed of in low-lying areas. A sludge
treatment facility is available in a few refineries. Centrifuge and vacuum filters are used in these
refineries for dewatering and volume reduction of sludge. Bio-sludge and chemical sludge are
usually stored in drying beds. The drying beds in the refineries are provided with filter medium
like sands, gravels, etc. Dried bio sludge is often applied on agricultural land and gardens in
order to exploit its manure potential. However, presence of heavy metals in the sludge is a major
constraint for its safe use as manure.
Environmental impact of disposal activities
The majority of the lagoons of refineries in India are lined with cement and bricks, and a few are
unlined. It has been observed that cracks developed in these lagoons which make a pathway for
the leach to enter the ground water aquifer and thus ground water is contaminated. In lagoons,
disposal of sludge create problems of odour and fire hazard. Uncontrolled disposal of oily sludge
from the tank and dried sludge from the lagoon on land also causes serious environmental
pollution. Leachate contaminated with the pollutants migrates through subsoil strata and pollutes
the ground water. The locations of landfill sites of Indian refineries have mostly been selected
according to availability of land and convenience rather than consideration of the hydro
geological features of the sites. Moreover, the majority of the refineries are located in coastal
areas where the ground water table is high. The sandy soils in these regions promote rapid
infiltration of leachate.
TREATMENT AND DISPOSAL; The salient features of various treatment and disposal
options for refinery sludges and their applicability.
SLUDGE DISPOSAL IN LAGOON/PIT
Containment of oily sludges in a lagoon is one of the commonly used methods for
storage/disposal of sludges. The lagoons are usually lined with bricks and cement. In Kuwait,
sludges are disposed of in the pits located within desert areas (Einawawy Amins et al. 1987).
Lagoons are used as storage places for sludges and cannot provide long term solutions for the
ultimate disposal of sludges. Moreover, lagooning of refinery sludge is not an environmentally
friendly solution to the disposal problem.
INCINERATION OF OILY SLUDGE
Incineration is the process of complete combustion of wastes in the presence of excess air. Time,
temperature and turbulence are the major factors, which control the combustion process. A
significant reduction in the volume of waste is achieved during the incineration process. Though
incineration of sludges is practiced in a few developed countries, it is not popular due to the
following reasons: (1) Fugitive and stack emissions from incineration and products of incomplete
combustion cause environmental pollution. (2) Incineration is the treatment process only and
landfill facilities are still needed for the final disposal of ashes. (3) Ashes resulting from the
incineration process contain heavy metals and need to be disposed of in an environmentally
friendly manner. (4) Commercial incinerators which are available in India are not designed for
the burning of oily sludge from refineries. Non-availability of incinerators appropriate for the
burning of refinery sludge and the emission of polluting gases are the major constraints in
adopting incineration for disposal of refinery sludges in India.
LAND FARMING
Land farming involves the application of wastes in controlled quantities to the land, followed by
application of fertilizer and regular planting of crops. This method depends mainly on the natural
in-situ biological decomposition of hydrocarbons by the vast and varied population of micro
flora in natural soils associated with photo-degradation. The structure of the soil and humus
content are the major factors in the process of hydrocarbon decomposition as they influence oil
and water retention, type and population of microflora and the rate of oxygen transfer. This
method is widely practiced, particularly in North America (Arora et al. 1982) where it is
successfully implemented in a wide range of soil types and climatic conditions. Land farming
has also been tried on an experimental basis in Kuwait (Einawawy Amins et al. 1987) and India.
In India, oily sludge has been applied at the rate of 5-10 kg/m2 on soil of silty clay category to
produce crops burseem & mellet (Gujrat Refinery, 1991). However, the feasibility of this
technique for large-scale application in India is yet to be established. Various environmental
issues such as the presence of oily odour during initial spreading, groundwater pollution due to
migration of leachate contaminated with hydrocarbons, phenols and heavy metals and health
problems associated with the contact of oily sludge need detailed investigations before any large-
scale application.
SECURE LANDFILL OF SLUDGES
In secure landfill techniques, the isolation from air and water is achieved through the use of thick
layers of impermeable clay and synthetic liner. When landfill is completed, it is capped with
layers of clay, flexible membrane liners and soil for vegetation. The top is contoured to prevent
ponding of rainwater on the surface and the vegetated contoured clay cover prevents water
intrusion into the completed landfill. The secure landfill system also employs a leachate
collection system above the bottom liner as a safeguard. Secure landfill is popular in developed
countries such as the USA, UK, Canada, Germany, etc. After dewatering, the sludges are
disposed of by secure landfill technique. Environmental problems encountered during land
disposal have been solved to a large extent by the introduction of secure landfill technique.
ACTIVATED SLUDGE TREATMENT WITH POWDERED ACTIVATED CARBON
(PACT®
The PACT® (Powdered Activated Carbon Treatment) system is similar to the conventional
activated sludge system described above. In this treatment system both biological oxidation and
carbon absorption occur simultaneously, thus enhancing the removal of contaminants in the
wastewater. Most of the powdered activated carbon is recycled with the activated sludge, but the
system requires a continuous makeup of fresh carbon. PACT® systems are generally used for
refinery wastewater in those cases where stringent standards need to be met for certain
contaminants.
SEQUENCING BATCH REACTOR
A sequencing batch reactor (SBR) is a fill-and-draw semi-batch biological treatment alternative
that employs aeration, sedimentation and clarification in a single reactor. The unit processes of
aeration and sedimentation are common to both the SBR and activated sludge systems. In
activated sludge systems the unit operations take place in different basins, while in the SBR the
operations take place in a sequential order in a common basin. Although still practiced in some
refineries, SBR technology is increasingly uncommon and has limited application in refinery
wastewater treatment. The various steps of operation are described below: ● Fill: During the fill
operation, wastewater with the substrate is added to the reactor. The aeration system is not
operated as the reactor is charged with wastewater from the equalization tank. ● React: During
this step, wastewater is aerated in the same way as in the activated sludge system. Biological
activity is initiated in this cycle of operation. ● Settle: In this step, aeration is terminated and
MLSS is allowed to settle. The settling is accomplished under quiescent conditions; no flow
enters, or is withdrawn from the reactor during the settle period. ● Decant: During the decant
period, clarified or treated supernatant effluent is withdrawn from the upper portion of the
reactor. The sludge blanket at the bottom of the reactor is maintained so that it is available as
seed sludge for the next cycle. ● Idle: This is not a necessary step and is usually omitted for the
refinery wastewater treatment system. The idle period is the time between the draw and the fill; it
could be zero or could be days. Generally, it is used in multi-tank systems, thereby providing
time to one reactor to complete its fill phase before switching to another unit.
MEMBRANE BIOREACTOR TECHNOLOGY
Membrane bioreactors (MBRs) are suspended growth biological treatment processes and are a
variation on the activated sludge system. A membrane bioreactor combines a membrane process
(e.g .microfiltration) with a suspended growth bioreactor, thereby eliminating the secondary
clarification used in an activated sludge system. A schematic of a typical MBR system is
D. CEMENTING WASTE
Used for a number of different reasons, cementing protects and seals the wellbore. Most
commonly, cementing is used to permanently shut off water penetration into the well. Part of the
completion process of a prospective production well, cementing can be used to seal the annulus
after a casing string has been run in a wellbore. Additionally, cementing is used to seal a lost
circulation zone, or an area where there is a reduction or absence of flow within the well. In
directional drilling, cementing is used to plug an existing well, in order to run a directional well
from that point. Also, cementing is used to plug a well to abandon it. Cementing is performed
when the cement slurry is deployed into the well via pumps, displacing the drilling fluids still
located within the well, and replacing them with cement. The cement slurry flows to the bottom
of the wellbore through the casing, which will eventually be the pipe through which the
hydrocarbons flow to the surface. From there it fills in the space between the casing and the
actual wellbore, and hardens. This creates a seal so that outside materials cannot enter the well
flow, as well as permanently positions the casing in place. Additives can be include accelerators,
which shorten the setting time required for the cement, as well as retarders, which do the
opposite and make the cement setting time longer. In order to decrease or increase the density of
the cement, lightweight and heavyweight additives are added. Additives can be added to
transform the compressive strength of the cement, as well as flow properties and dehydration
rates. Extenders can be used to expand the cement in an effort to reduce the cost of cementing,
and antifoam additives can be added to prevent foaming within the well. In order to plug lost
circulation zones, bridging materials are added, as well.
Cementing the Well; After casing, or steel pipe, is run into the well, an L-shaped cementing head
is fixed to the top of the wellhead to receive the slurry from the pumps. Two wiper plugs, or
cementing plugs, that sweep the inside of the casing and prevent mixing: the bottom plug and the
top plug. Keeping the drilling fluids from mixing with the cement slurry, the bottom plug is
introduced into the well, and cement slurry is pumped into the well behind it. The bottom plug is
then caught just above the bottom of the wellbore by the float collar, which functions as a one-
way valve allowing the cement slurry to enter the well.
Then the pressure on the cement being pumped into the well is increased until a diaphragm is
broken within the bottom plug, permitting the slurry to flow through it and up the outside of the
casing string.
Bottom and Top Plugs
After the proper volume of cement is pumped into the well, a top plug is pumped into the casing
pushing the remaining slurry through the bottom plug. Once the top plug reaches the bottom
plug, the pumps are turned off, and the cement is allowed to set. The amount of time it takes
cement to harden is called thickening time or pump ability time. For setting wells at deep depths,
under high temperature or pressure, as well as in corrosive environments, special cements can be
employed.
SOURCES OF CONTAMINATION
The main source of this contamination is the drilling of green.
cement or adoption of poor placement procedures.
DIAGNOSIS; Cement contamination will result in:
increased pH
an increase in Pf and calcium
a large increase in Pm.
TREATMENT
Prior to drilling cement, pre-treat the mud with 0.5-1.0 lb/bbl
of sodium bicarbonate.
If this is insufficient, treat cement contamination at the rate
of 0.15 lb/bbl sodium bicarbonate per 100 ppm calcium
(determine calcium using procedure below)
If sodium bicarbonate treatment levels are based on filtrate calcium
only, an incorrect treatment level will be obtained. This is because
the majority of the cement will stay in suspension rather than go into
solution due to the high pH.
To obtain the total calcium level, the following procedure is
recommended:
1. Add 90 cm3 distilled water to 10 cm3 mud.
2. Titrate with 0.1 NH2S04 to a pH of 7.5 - 8.0.
3. Continue mixing for two minutes to ensure no pH rise.
4. Filter the slurry on the standard filter press.
5. Titrate 10 cm3 of filtrate with standard Versenate (001 molar).
Calcium = mls versenate x 4000
Note:
1. When large quantities of cement are drilled it may not be
economical to treat out the contamination due to the large
concentrations of bicarbonate required. In this case, the best
course of action may be to change out the contaminated mud
for new mud or drill cement with sea water if available.
2. When drilling cement, the rig crew shall be aware of the
possibility of plugged/blinded screens.
3. Onshore operations tend to drill cement with well water and
or mud and dump the contaminated mud.
E. PAINTING WASTE: If you conduct spray painting operations, a hazardous waste
determination must be made on waste paint, solvents/thinners, paint sludge, primer waste, and
spray booth filters. The paints and paint sludges may be hazardous if they contain heavy metals,
such as arsenic, lead and chromium. The solvents may be characteristically hazardous due to
their ignitability or they could be a listed hazardous waste. Also, many primers, lacquers, and
enamels are flammable. Furthermore, during spray painting operations, volatile organic
compounds and hazardous air pollutants are released into the environment. These pollutants are
regulated under the Clean Air Act. Below you will find resources to help owners and operators
of auto repair shops understand and comply with federal, state, and local regulations concerning
painting operations as well as "green" practices to reduce your wastes and emissions from spray
paint.
F. CRUDE OIL RADIOACTIVE TRACERS WASTE; Are used in the oil industry in order to
qualitatively or quantitatively gauge how fluid flows through the reservoir, as well as being a
useful tool for estimating residual oil saturation. Tracers can be used in either interwell tests or
single well tests. In interwell tests, the tracer is injected at one well along with the carrier fluid
(water in a waterflood or gas in a gas flood) and detected at a producing well after some period
of time, which can be anything from days to years. In single well tests, tracer is injected into the
formation from a well and then produced out the same well. The delay between a tracer that does
not react with the formation (a conservative tracer) and one that does (a partitioning tracer) will
give an indication of residual oil saturation, a piece of information that is difficult to acquire by
other means. Tracers can be radioactive or chemical, gas or liquid and have been used
extensively in the oil industry and hydrology for decades.
G. DRILLING FLUID (DRILL MUD): Drill mud (also called cutting mud) is a complex
colloidal mixture of water, bentonitic clays, chemical additives, and trace amounts of oil from
cuttings of the hydrocarbon-bearing zones. This mud serves several purposes in oil drilling as it
is circulated down the inside of the rotating drill from the surface and backup the annular space
between the drill pipe and the drilled hole. At the drill bit/rock interface, it cools and lubricates
the cutting action. As it flows up the annular space, it lifts rock chips which can then be screened
out at the surface. Most important, the column of mud creates hydrostatic pressure which keeps
pressurized oil or gas from being expelled uncontrollably (a “blowout”).Much of this drill mud is
recycled, but after repeated use it picks up fine rock particles and water soluble subsurface
minerals until it is no longer economically practical to recondition it. The colloidal mass can then
be separated from the water either by centrifugal processes or by simply allowing it to settle in a
pit. The remaining fluid is then disposed of by deep injection. Much progress has been made in
the last decade in the employment of low toxicity mud additives, which has enabled the EPA to
issue NPDES permits for offshore discharges of treated muds and cuttings.
One roundtable suggestion was to investigate lower toxicity components or better reconditioning
techniques. Several participants noted that more uniform drilling systems and chemical
formulations in a single oil field or petroleum province might lead to more cost effective
recycling of muds by avoiding the “customized” treatment required when multiple formulations
are used. Another suggestion was to investigate the recycling of used muds or cuttings into
masonry, tiles, bentonite caps for landfills, or other products.
Drill cutting: Drill cuttings are the pieces of rock and soil removed from the ground as a drill bit
cuts a hole for a well. Present technology for disposal of these cuttings is to bury them in a non-
leaching lined landfill which freezes and becomes incorporated into the permafrost on the
Alaskan North Slope. In at least one North Slope oil field, cuttings are ground using a ball mill.
The ground material is then slurried and injected into a permeable subsurface formation.
COMPOSITION OF DRILLING MUD: Water-based drilling mud most commonly consists of
bentonite clay (gel) with additives such as barium sulfate (barite), calcium carbonate (chalk) or
hematite. Various thickeners are used to influence the viscosity of the fluid, e.g. xanthan gum,
guar gum, glycol, carboxymethylcellulose, polyanionic cellulose (PAC), or starch. In turn,
deflocculants are used to reduce viscosity of clay-based muds; anionic polyelectrolytes (e.g.
acrylates, polyphosphates, lignosulfonates (Lig) or tannic acid derivates such as Quebracho)
are frequently used. Red mud was the name for a Quebracho-based mixture, named after the
color of the red tannic acid salts; it was commonly used in 1940s to 1950s, and then was made
obsolete when lignosulfonates became available. Other components are added to provide various
specific functional characteristics as listed above. Some other common additives include
lubricants, shale inhibitors, and fluid loss additives (to control loss of drilling fluids into
permeable formations). A weighting agent such as barite is added to increase the overall density
of the drilling fluid so that sufficient bottom hole pressure can be maintained thereby preventing
an unwanted (and often dangerous) influx of formation fluids.
HEALTH EFFECT ASSOCIATED WITH DRILLING FLUIDS CONTACT:
The risk of adverse health effects from drilling fluids is determined by the hazardous components
of the fluids, additives and by human exposure to those components.
Skin irritation and contact dermatitis are the most common health effects observed from drilling
fluids exposure in human beings, with headache, nausea, eye irritation, and coughing seen less
frequently. The effects are caused by the physico-chemical properties of the drilling fluid as well
as the inherent properties of drilling fluid additives, and are dependent on the route of exposure
such as dermal, inhalation, oral and others.
INHALATION EXPOSURE:
The potential chemical changes in drilling during use and recycling can result in more toxic
substance being released. Since drilling fluids are subjected to elevated temperatures and
increased pressures, there has been a concern that organic components might break down, or
chemical reactions might occur, to form more toxic substances. There was a particular concern
that base oil high in aromatics might contain, or form Polycyclic Aromatic Hydrocarbons
(PAHs), while muds (drilling fluids) based on alkyl benzenes might break down to yield free
benzene. OGP and IPIECA (2009) also reported that drilling fluids are often circulated in an
open system at elevated temperatures with agitation that can result in a combination of vapours,
aerosol and/or dust above the mud pit. In the case of water-based fluids the vapours comprise
steam and dissolved additives. In the case of non-aqueous drilling fluids the vapours can consist
of the low boiling-point fraction of hydrocarbons (paraffin, olefins, naphthenes and aromatics),
and the mist contain droplets of the hydrocarbon fraction used. This hydrocarbon fraction may
contain additives, sulphur, mono-aromatics and/or polycyclic aromatics. It should be noted that
although the hydrocarbon fraction may contain negligible amounts of known hazardous
constituents such as Benzene, toluene, ethylbenzene and xylenes (BTEX) at low boiling point,
these will evaporate at relatively higher rates potentially resulting in higher concentrations in the
vapour phase than anticipated. McDougal et al. (2000), also reported that petroleum distillates
such crude oil, diesel oil (Group I-Non Aqueous Fluids) have been associated with renal, hepatic,
neurologic, immunologic, and pulmonary toxicity when they are inhaled or ingested. They are
also irritating to the skin and mucus membrane. ATSDR (1999a) reported some health effects
associated with inhalation exposure as: Neurological effects, Carcinogenicity, Haematological
effect, Immunological effect, Lymphoreticular effects and pulmonary effects
DERMAL EXPOSURE: Most chemicals are readily absorbed through the skin and can cause
other health effects and/or contribute to the dose absorbed by inhalation of the chemical from the
air. When drilling fluids are circulated in an open system with agitation, there is a high likelihood
of dermal exposure resulting in dermatitis and skin irritation. The potential dermal exposure is
not limited to the hands and forearms, but extends to all parts of the body. Actual exposure
depends on the drilling fluid system and the use of Personal Protection Equipment (PPE). Many
studies indicate that absorption of chemicals through the skin can occur without being noticed by
the worker. In many cases, skin is a more significant route of exposure than the lung (OSHA,
2009).
DERMATITIS AND IRRITATION: Skin contact with drilling fluids or mud can also cause
inflammation of the skin, referred to as dermatitis. Signs and symptoms of dermatitis can include
itching, redness, swelling, blisters, scaling, and other changes in the normal condition of the skin
(Fig. 5, Anonymous, 2009). On the drill floor, in particular, skin contamination can be broad, but
occasionally dermatitis also occurs in divers who make contact with discarded cuttings on the sea
bed (Ormerod et al., 1998). Petroleum hydrocarbons will remove natural fat from the skin, which
results in drying and cracking. These conditions allow compounds to permeate through the skin
leading to skin irritation and dermatitis. Some individuals may be especially susceptibility to
these effects. Skin Fig. 5: Dermatitis of the hands irritation can be petroleum hydrocarbons,
specifically with aromatics and C8-C14 paraffins. Petroleum streams containing these
compounds, such as kerosene and diesel (gas oil), are clearly irritating to skin. This is suggested
to become malignant caused by the paraffins, which do not readily penetrate the skin but are
absorbed into the skin, hereby causing irritation (McDougal et al., 2000). Linear alpha olefins
and esters commonly used in drilling fluids are only slightly irritating to skin, whereas linear
internal olefins are not irritating to skin. In addition to the irritancy of the drilling fluid
hydrocarbon constituents, several drilling fluid additives may have irritants, corrosive or
sensitizing properties (Cauchi, 2004). For example calcium chloride has irritant properties and
zinc bromide is corrosive whereas a polyamine emulsifier has been associated with sensitizing
properties. Although water based fluids are not based on hydrocarbons, the additives in the fluid
may still cause irritation or dermatitis. Excessive exposure under conditions of poor personal
hygiene may lead to oil acne and folliculitis (OGP and IPIECA, 2009). ATSDR (1997)
concluded that it is reasonable to expect that adverse haematological and immunological effects
might occur following dermal exposure to benzene.
ORAL EXPOSURE: Oral exposure is negligible as compared to the other exposure routes such
dermal, inhalation and others. Oral exposure may occur when hands are not well washed before
they are used to handle thing like cigarette. Data for the oral route of exposure are less extensive.
The BTEXs cause neurological effects, generally central nervous system depression, by the oral
route. Renal and hepatic effects are also seen with oral exposure to these compounds. Renal
effects are the basis for the intermediate. The hepatic effects tend to be mild, including increased
liver weight an cytochromes.
Benzene causes haematological effects by the oral route that is similar to those seen from
inhalation exposure.
HIERARCHY OF PRINCIPLE OF CONTROL:
If hazardous components of drilling fluids are identified at each stage of any drilling operation or
areas where drilling fluids are likely to be exposed, together with a risk of exposure then, the
following hierarchy of principles of control should be considered: C Elimination (not feasible)
C Substitution (low toxic base oils, WBFs), C Engineering controls (greater enclosure)
C Administrative controls (rotate jobs, hygiene measures, education of Control of Substances
Hazardous to Health (COSHH), skin management systems and improved laundry practices)
C Personal protective equipment (chemical resistant slicker suit and gloves)
CHALLENGES IN SETTING DRILLING FLUID EXPOSURE STANDARDS:
The health exposure standard of drilling fluid during oil and gas operations has always not be
given the same attention or concern as its effects and risk management guidelines due to the
following challenges:
C Drilling fluids are complex mixtures of variable composition, C It unclear about the longer
term of health effect, C There is no scientific basis on which to set health exposure limit
C Exposure must be made up of all pertinent fractions such aerosol, vapour, etc., and all
variation in composition, C Exposure should reflect the level that can be achieved using good
practices.
EXPOSURE INDICATORS: In spite of the challenges of setting health exposure standards of
drilling fluid exposure to oil and gas workers, Agency for Toxic Substances and Disease
Registry (ATSDR) has researched into the BTEXs which are released as a result of drilling fluids
during agitation under high pressures and temperature. The study presents these findings by
ATSDR as an Exposure Indicator or Lowest Observed Adverse Effect Level (LOAEL) for
drilling fluid exposure to operators to help reduce the dangers of abnormal drilling fluids
exposure.
TREATMENT OF DRILLING FLUIDS AND DRILLING MUD: Contaminated drilling fluids
and mud are a considerable potential hazard to the sensitive marine ecosystem. The appropriate
process treats the contaminated fluids and muds sufficiently so that by the end of the process,
purified and thus unpolluted water can be discharged into the environment. This task is
performed by the high-speed decanters and clarifiers from GEA Westfalia Separator. Drilling
fluids are understood to be viscous emulsions which are circulated through the drilling pipe
during drilling for crude oil in order to pump the milled product upwards at the same time as the
oil. These emulsions rapidly become contaminated with mud, salt water and oil residues. This
means that the drilling fluids have to be continuously cleaned to ensure a smooth drilling
process. The contaminated fluids are also a hazard to the sea; however, so continuous treatment
is all the more important. Once the drilling fluids have passed through a coarse screen and had a
flocculant and a flush liquid added, the coarser solids are separated off by a decanter of the
appropriate output. The liquid phase is initially passed to a slop oil tank. A clarifier from GEA
Westfalia Separator then separates the fine residual solids so that the liquid phase can be
discharged into the environment in the form of pure water after passing through a protective
filter. This complies with the “zero emission” philosophy in an exemplary manner.
Treatment of drilling fluids
To treat drilling mud rich in solids, GEA Westfalia Separator has also developed special high-
speed decanters which, in the form of the Westfalia Separator cdforce generation, work
efficiently on drilling platforms and FPSOs.
THE ELECTROCHEMICAL METHOD OF DRILLING MUD TREATMENT.
The electrochemical methods of and devices for drilling mud treatment, which became
the basis for electrochemical activation technology, had been over. Drilling mud is a
complex poly-disperse system containing clayey mineral particles in water with added
organic substances - stabilizers, structure forming agents, thinners and fluid loss
additives. The main technological function of drilling mud is bringing drill cuttings
from the well bottom to the surface. Clayey particles in drilling mud are normally
negatively charged, the charge density depending on surface configuration and
chemical composition of clayey particle crystal lattice, as well as on chemical
composition and electrolyte content of the liquid phase of drilling mud. Passing current
through drilling mud commonly results in deposition on the anode of firm clayey crust
made up of the most fine-disperse and highly-charged clayey particles. This crust
prevents products of anode electrochemical reactions from entering the drilling mud,
therefore the solution’s рН value increases due to cathode, actually unipolar,
electrochemical treatment. It was found that in conditions of the same consumed
quantity of specific power, the smaller the cathode area as compared to the anode one,
the stronger thixotropic properties of drilling mud (structural-mechanic strength) with
simultaneously lower dynamic viscosity (paradox). The paradox can be explained in
the following way: electric charges accumulated on the edges and pointed parts of tiny
scales or needle-like particles of argillaceous minerals are several times stronger than
the charges on their flat facets. Under the influence of electrochemical treatment, in a
high voltage electric field close to the cathode surface (in the area of spatial charge),
there increased absolute value of particles’ negative charge, thus enhancing their
repulsion forces and therefore lowering viscosity. At the same time, however,
difference of potentials between the edges and facets of argillaceous particles also
increased, causing growth of forces putting in good order structural arrangement of
interacting clayey particles. So, drilling mud’s structural and mechanical properties
improved due not to mechanical, but to electrostatic adhesion of clayey particles.
Electrochemical and chemical regulation methods, and attempt practical application of
the discovered effect in the process of oil and gas well drilling. The reported effect had
not been known before; therefore the process of unipolar cathode electrochemical
treatment of drilling mud was first called by V.M. Bakhir low-voltage polarization, and
three years later –electrochemical activation. The above-indicated first invention
established a non-chemical method to improve drilling mud parameters by treatment in
an engineering electrochemical system consisting of a current power supply and two
electrodes, the cathode surface area being smaller than the anode one. In this
electrochemical system, the surfaces of drilling rig circulation system coming into
contact with drilling mud actually performed the function of anode. Practical trials
proved the method’s high efficiency, which allowed saving up to 30 % of chemical
reagents commonly used for a well drilling. However, the method had a significant
disadvantage, that is, the necessity to periodically remove clayey crust from anode
surface and laboriousness of this procedure.
H. SCALES
The oil and gas TENORM-contamination arises in the piping, pumps, valves and tanks used in
the drilling and oil-extraction processes due to so-called scale which is mainly a precipitation
containing radioactivity. The radioactivity in the scale is dominated by radium and its daughter
nuclides. The origin of the radioactivity is of course the natural occurrence of uranium and
thorium in the bedrock.
Scale formed in the oil and gas industry is, according to the literature [see for example 1], mainly
barium sulphate. Barium sulphate is a substance more or less famous for its very low solubility
product. Since radium is a chemical analogue to barium, radium will naturally accumulate in the
scale matrix of barium sulphate, which will then become radioactive and in need of treatment/
handling according to the local regulations.
Scale is often removed from piping with high-pressure water-jetting. This results in a slurry of
scale, water and some oil which can be radioactive or not. The piping from which the scale is
removed are often slightly contaminated as well, due to cracks and corrosion on the pipe walls.
In other parts of the North Sea the radium is not the main contamination. In parts where gas is
extracted Po-210 and Pb-210 is the most important contaminant due to the decay of radon in the
gas.
Scale is composed primarily of insoluble barium, calcium, and strontium compounds that
precipitate from the produced water due to changes in temperature and pressure. Radium is
chemically similar to these elements and as a result is incorporated into the scales.
Concentrations of Radium-226 (Ra-226) are generally higher than those of Ra-228.
Scales are normally found on the inside of piping and tubing. The API found that the highest
concentrations of radioactivity are in the scale in wellhead piping and in production piping near
the wellhead. Concentrations were as high as tens of thousands of picocuries per gram. However,
the largest volumes of scale occur in three areas:
(1) Water lines associated with separators, (separate gas from the oil and water)
(2) Heater treaters (divide the oil and water phases)
(3) Gas dehydrators, where scale deposits as thick as four inches may accumulate.
Chemical scale inhibitors may be applied to the piping complexes to prevent scales from slowing
the oil extraction process. If the scales contain TENORM, the radiation will remain in solution
and eventually be passed on to the produced waters. Approximately 100 tons of scales per oil
well are generated annually in the United States. As the oil in a reservoir dwindles and more
water is pumped out with the oil, the amount of scale increases. In some cases brine is introduced
into the formation to enhance recovery; this also increases scale formation. The average radium
concentration in scale has been estimated to be 480 pCi/g. It can be much higher (as high as
400,00s0 pCi/g) or lower depending on regional geology Petroleum pipe scale, consisting of
concentrated inorganic solids such as barium sulfate, can deposit on the inside of down-hole
pipes during the normal course of oil field pumping operations. A portion of this scale has been
shown to contain naturally occurring radioactive materials (NORM), predominantly compounds
of radium. When these pipes are removed from the well, there is a potential for radiation doses to
the oil field workers handling the pipes, especially as the pipes are cleaned for reuse. A thorough
sampling and measurement protocol was applied under a variety of weather conditions in an
outdoor laboratory to obtain an accurate indication of the radiological and aerodynamic
characteristics of scale release and dust dispersion during petroleum pipe scale removal from
out-of-service pipes with a restored, historically relevant outdoor pipe-cleaning machine.
Exposure rate data were also obtained for both the pre-cleaned pipes, and the general area
inhabited by workers during the descaling operation. Four radiation exposure pathways were
investigated: inhalation of pipe scale dust generated during pipe rattling, incidental ingestion of
the pipe scale dust, external exposure from uncleaned pipes, and external exposure from pipe
scale dispersed on the ground. Pipes from three oil fields were rattled to collect as much
industry-representative data as possible. The 226Ra specific activity of the pipe scale ranged from
33.6 ± 0.4 to 65.5 ± 0.7 Bq g-1, depending on the formation. A median atmospheric dust loading
of 0.13 mg m-3 was measured in the operator breathing zone. The respirable fraction was
observed to be about 42% to 46%. Based on cleaning 20 pipes per day,250 d per year on
average, annual committed effective doses for the operator and helper ranged from 0.11 mSv (11
mrem) to 0.45 mSv(45 mrem) for inhalation and from 19 μSv (1.9 mrem) to 97 μSv (9.7mrem)
for incidental ingestion. Worker annual external dose from the pipe racks ranged from 0 to 0.28
mSv (28 mrem). In the deposition experiment, more than 99% by weight of the deposited scale
fell within 2 m of the machine centerline, the vast majority of which was in the downwind
direction. The dose from this deposited material dominated the worker dose estimates. The
annual external dose from dispersed material was estimated to be 2.8 mSv (280 mrem) for the
operator and 4.1 mSv (410 mrem) for the helper.
HANDLING OF SCALE – A NEW APPROACH
Based on the experience from waste treatment for the nuclear industry and with the same
approach, development of a method for treatment of radioactive material from the oil and gas
industry was started. The aim was to minimize the final waste volume and to produce a waste,
which will not chemically or biologically degrade over long time and maybe produce chelates, as
in a final storage, or being contained in a non-solid matrix. The aim is supported by the intention
that the majority of other materials, for example steel from piping, after treatment which no
longer are classified as radioactive shall be recycled. There is also the intent of the method to
meet environmental demands as they are agreed upon today and also to meet demands that might
be more restrictive in the future. In the oil and gas industry today there are radioactive material
identified on several of the large oilfields [5-8 and references therein]. Depending on the
regulations and legislation the handling of the occurring TENORM material are very different
from site to site. From the above given prerequisites a process which can handle both the scale
and scrapped steel piping was designed. The procedure is divided into two parts, one for the
metal and one for the scale. Discalced and scrapped piping can be melted in order to simplify the
clearance procedure if the authorities or the industry demand it. The scale is treated in a separate
procedure in which the radioactive components are separated from the non-radioactive
components. This means that the amount of radioactive waste that need handling and disposal is
minimised, and therefore also the costs. The procedure also ensures that the waste is dry, not
biodegradable or contains any chelates, which is essential for the repository, especially if the
repository is in contact with water. The process is yet in its development stage but so far a
volume reduction factor of at least 20 is reasonable. This means that the amount of waste after
treatment is only 5 % of the original volume.
H METALS SCRAPS
Treating low-level scrap metals from the nuclear industry. The aim for the treatment is to release
the metals from regulatory control and to recycle the metals outside the nuclear industry.
Studsvik Rad Waste has a permit to store material for 20 years awaiting decay of the
radioactivity. At Studsvik all scrapped metal are melted in one of the induction furnaces. The
induction homogenizes the melt and one sample is representing the whole batch, 3.5 tonnes of
steel. This makes proving the activity content for clearance of the metal very easy. Since
uranium cannot be stored for decay and since there are metals contaminated with uranium that
can be re-used Studsvik RadWaste AB has, in the last few years, developed a method for
decontamination of steel from uranium during the melt process. This method can be used for
TENORM contaminated material as well. With these experiences a handling and clearance of
material from the oil and gas industry can be done according to regulations. Melting of these
materials in an induction furnace has the advantage that any radioactivity left in the metal is
homogeneously distributed. How this material will be released from regulatory control is under
implementation in many countries today and the outcome is to be seen.
I. PIGGING WASTE
What is the purpose of pigging? In order to protect these valuable investments, maintenance
must be done and pigging is one such maintenance tool. During the construction of the line, pigs
can be used to remove debris that accumulates. Testing the pipeline involves hydro-testing and
pigs are used to fill the line with water and subsequently to dewater the line after the successful
test. During operation, pigs can be used to remove liquid hold-up in the line, clean wax off the
pipe wall or apply corrosion inhibitors for example. They can work in conjunction with
chemicals to clean pipeline from various build-ups. Inspection pigs are used to assess the
remaining wall thickness and extent of corrosion in the line, thus providing timely information
for the operator regarding the safety and operability of the line. Pigs (or more specifically) plugs
can be used to isolate the pipeline during a repair. A pig is a device inserted into a pipeline which
travels freely through it, driven by the product flow to do a specific task within the pipeline.
These tasks fall into a number of different areas: (a) Utility pigs which perform a function such
as cleaning, separating products in-line or dewatering the line; (b) Inline inspection pigs which
are used to provide information on the condition of the pipeline and the extent and location of
any problem (such as corrosion for example) and (c) special duty pigs such as plugs for isolating
pipeline. The pipeline layout and features will dictate the geometry of the pig largely. The pig
must be long enough to span features such as wyes and tees yet must be short enough to
negotiate bends. Changes in internal line diameter will influence the design effort required for
the pig. In summary, the correct pig type is chosen for the task but then the pipeline design and
operating conditions will affect the actual design of the pig. The differences between offshore
and onshore pipelines and their intelligent pigging procedures. Offshore pipelines are of thicker wall
than onshore-sometimes up to 35mm thick. Offshore pipelines can have greater operating pressures,
particularly the deepwater pipelines offshore Angola, Brazil or Gulf of Mexico. Maximum operating
pressures onshore can be 100barg but offshore can be 300barg. Flow rates of products both onshore
and offshore are the same dependant upon the type of pipeline or its position with regard to
transporting product either between offshore platforms or from platform to shore.
A cleaning pig for a 6-inch oil pipeline. The wire brush encircles the shaft and scours the interior
of the pipeline. Pigging can be used for almost any section of the transfer process between, for
example, blending, storage or filling systems. Pigging systems are already installed in industries
handling products as diverse as lubricating oils, paints, chemicals, toiletries, cosmetics and
foodstuffs. Pigs are used in lube oil or painting blending: they are used to clean the pipes to avoid cross-
contamination, and to empty the pipes into the product tanks (or sometimes to send a component back
to its tank). Usually pigging is done at the beginning and at the end of each batch, but sometimes it is
done in the midst of a batch, e.g. when producing a premix that will be used as an intermediate
component.
ETYMOLOGY: The original pigs were made from straw wrapped in wire used for cleaning.
They made a squealing noise while traveling through the pipe, sounding to some like a pig
squealing, which gave pigs the name. (Disputed: 'PIG' is an acronym or backronym derived from
the initial letters of the term 'Pipeline Inspection Gauge.').
PIGGING IN PRODUCTION ENVIRONMENTS
A major advantage of piggable systems is the potential resulting product savings. At the end of
each product transfer, it is possible to clear out the entire line contents with the pig, either
forwards towards the receipt point, or backwards to the source tank. There is no requirement for
extensive line flushing. Without the need for line flushing, pigging offers the additional
advantage of a much more rapid and reliable product changeover. Product sampling at the receipt
point becomes faster because the interface between products is very clear, and the old method of
checking at intervals, until the product is on-specification, is considerably shortened.
ENVIRONMENTAL ISSUES
Pigging has a significant role to play in reducing the environmental impact of batch operations.
Traditionally, the only way that an operator of a batch process could ensure a product was
completely cleared from a line was to flush the line with a cleaning agent such as water or a
solvent or even the next product. This cleaning agent then had to be subjected to effluent
treatment or solvent recovery. If product was used to clear the line, the contaminated finished
product was downgraded or dumped. All of these problems can now be eliminated due to the
very precise interface produced by modern pigging systems.
SAFETY CONSIDERATIONS
Pigging systems are designed so that the pig is loaded into the launcher, which is pressured up to
launch the pig into the pipeline through a kicker line. In some cases, the pig is removed from the
pipeline via the receiver at the end of each run. All systems must allow for the receipt of pigs at
the launcher, as blockages in the pipeline may require the pigs to be pushed back to the launcher.
Most of the time, systems are designed to pig the pipeline in either direction. The pig is pushed
either with an inert gas or a liquid; if pushed by gas, some systems can be adapted in the gas inlet
in order to ensure pig's constant speed, whatever the pressure drop is. The pigs must be removed,
as many pigs are rented, pigs wear and must be replaced, and cleaning pigs push contaminants
from the pipeline such as wax, foreign objects, hydrates, etc., which must be removed from the
pipeline. There are inherent risks in opening the barrel to atmosphere and care must be taken to
ensure that the barrel is depressured prior to opening. If the barrel is not completely depressured,
the pig can be ejected from the barrel and operators have been severely injured when standing in
front of an open pig door. When the product is sour, the barrel should be evacuated to a flare
system where the sour gas is burnt. Operators should be wearing a self-contained breathing
apparatus when working on sour systems.
A pig on display in a section of cutaway pipe, from the Alaska Pipeline. Pipeline inspection
gauge or "PIG" in the pipeline industry is a tool that is sent down a pipeline and propelled by the
pressure of the product in the pipeline itself. There are four main uses for pigs:
1. Physical separation between different liquids being transported in pipelines;
2. Internal cleaning of pipelines;
3. Inspection of the condition of pipeline walls (also known as an Inline Inspection (ILI)
tool);
4. Capturing and recording geometric information relating to pipelines (e.g. size, position).
One kind of pig is a soft, bullet shaped polyurethane foam plug that is forced through pipelines to
separate products to reduce mixing. There are several types of pigs for cleaning. Some have
tungsten studs or abrasive wire mesh on the outside to cut rust, scale, or paraffin deposits off the
inside of the pipe. Others are plain plastic covered polyurethane. Inline inspection pigs use
various methods for inspecting a pipeline. A sizing pig uses one (or more) notched round metal
plates that are used as gauges. The notches allow different parts of the plate to bend when a bore
restriction is encountered. More complex systems exist for inspecting various aspects of the
pipeline. Intelligent pigs, also called smart pigs, are used to inspect the pipeline with sensors and
record the data for later analysis. These pigs use technologies such as MFL and ultrasonics to
inspect the pipeline. Intelligent pigs may also use calipers to measure the inside geometry of the
pipeline.
J. AIR EMISSON
The effects of the Nigerian oil industry on global climate change should also raise great concern.
Wasteful gas flaring - the burning of the gas released during oil production – results in enormous
levels of greenhouse gas emissions every year. According to Friends of the Earth Netherlands, in
the Niger Delta alone, these emissions are equivalent to the CO2 emissions of 4 million cars or
of 2 million European households. Gas flaring also causes health problems such as leukemia and
asthma. The acid rain caused by flaring also negatively affects food production. Nigeria is the
largest gas flarer in the world. Nigeria’s flaring is sometimes described as "environmental
racism" since this outdated, harmful and wasteful practice has already been terminated decades
ago in Northern, rich, and industrialized countries.
CRUDE OIL EXTRACTION
GHG emissions in the extraction phase are determined by the interactions of eight main
parameters:age of oil field, gas-to-oil ratio, reservoir depth, pressure, viscosity, American
Petroleum Institute (API) gravity (a measure of how “light” or “heavy” a crude is relative to
water), type of feedstock (e.g., tar sands, conventional crude), and development type [onshore,
offshore, surface mining, steam-assisted gravity drainage (SAGD)]. This study does not consider
coal-to-liquid and gas-to-liquid methods or oil shale.
The ratio of the volume of gas in solution to the volume of crude oil at standard conditions is the
gas-to-oil ratio (GOR). Higher values of GOR lead to higher production of natural gas. The gas
produced can be used in extraction for meeting onsite energy needs, exported, and/or flared and
vented. If it is flared and vented, it can substantially increase life-cycle GHG emissions. A high
GOR can also correspond to production of substantial amounts of oil condensates. The age of an
oil field influences GHG emissions because as fields mature, oil production declines; energy
intensive techniques such as water or gas injection must then be used to extend production levels,
resulting in increased GHG emissions. Heavier crude oils (low API gravity) require more energy
to extract, transport, and refine. Crude oils with higher viscosity require more energy for
pumping. Reservoir depth and pressure also affect energy use in extraction. With a decrease in
depth, friction losses increase in the drill pipe. As fields mature, the initial pressures tend to
decline in the absence of intervention. Maintenance techniques such as water injection are
required to maintain the initial pressure. These pumping or compression techniques involve
pumping fluids back into the reservoir to extract crude oil. If the initial reservoir pressure is high,
the energy required for maintaining the pressure will also be high. Different amounts of energy
are required to extract and upgrade crude oil from different types of feedstock. Tar sands and
conventional oil require completely different extraction technologies. Among tar sands,
differences exist between surface mining and in situ methods such as SAGD, resulting in
different GHG emissions. In addition, the type of oil field development [onshore/offshore,
surface mining, thermally enhanced oil recovery (TEOR), etc.] determines the infrastructure
required. Differences in infrastructure also influence energy requirements affecting GHG
emissions during extraction of crude oil. For example, TEOR requires more energy than any
other conventional form of offshore or onshore crude oil extraction. Note as the age of an oil
field influences GHG emissions because as fields mature, oil production declines; energy-
intensive techniques such as water or gas injection must then be used to extend production levels.
FLARING AND VENTING: Flaring and venting are an important source of GHG emissions
from oil fields. When crude oil is extracted, gas dissolved in crude oil is released, which can be
used for meeting energy needs in extraction, captured and sold as product, or flared and vented.
Flaring refers to disposal of associated gas produced during extraction through burning. Venting
refers to intentional releases of gas and the release of uncombusted gas in flaring (the
combustion efficiency of flaring is not 100%, so some methane is left in the exhaust gas). In this
study, the volume of gas flared is derived from GOR, energy use in the field, and the quantity of
gas exported. Satellite data (e.g., from NOAA) and country-level emission factors [Global Gas
Flaring Reduction (GGFR); World Bank, n.d.] were also used. Besides the volume of gas flared,
gas specifications are important in determining GHG emissions from flaring. In general, gas with
higher energy content per unit volume produces more GHG emissions when flared. One can be
reasonably confident about which oil fields are flaring and which are not from satellite data and
the lack or presence of infrastructure. However, uncertainties exist with regard to the volumes of
gas.
FUGITIVE EMISSIONS: Fugitive emissions represent unintentional or uncontrollable releases
of gas—for example, from valves and mechanical seals. It is difficult to measure fugitive
emissions. The usual practice is to base such measurements on emission factors suggested by the
Canadian Association of Petroleum Producers (CAPP), the U.S. Environmental Protection
Agency (EPA), and the International Association of Oil and Gas Producers (OGP). In this study,
fugitive emissions were determined on the basis of CAPP emission factors (CAPP, 2003) for
equipment fittings such as seals, valves, and flanges. The use of such emission factors can result
in significant errors. The alternative is to use leak detection methods, such as acoustic sensors
and hyperspectral imaging, and optical methods such as tunable diode laser absorption
spectroscopy and laser-induced fluorescence. The costs of monitoring and verification using
these techniques can be high.
TRANSPORT
GHG emissions from crude oil transport to a refinery are a function of distance, API gravity, and
mode of transport. API data were taken from PennWell. Distances between oil fields and
refineries were determined using Port World. Emission factors for a given mode of transport
were taken from GREET (Wang, 2010).
REFINING
GHG emissions from refining are a function of API gravity, sulfur content, and type of refinery.
In general, heavy crudes (low API gravity) require more energy to process than light crudes. In
this study, we applied the relationship devised by Keesom, Unnasch, and Moretta (2009),
calibrated to European refineries, to estimate GHG emissions. The relationship between API
gravity and energy consumption is not linear for API gravities above 45. GHG emissions also
vary from one refinery type to another depending on the level of complexity and type of refined
products produced. As a simplification, this study assumes that crude oils are refined in a
notional refinery where GHG emissions are determined entirely by API gravity. The impact of
sulfur content was not considered in this study.
UNCERTAINTIES IN THE ASSESSMENT
There are uncertainties involved in undertaking a carbon intensity assessment such as this. For
instance, some of the most important emissions sources, such as flaring and fugitive emissions,
are not fully monitored by oil companies, and where they are, the data may not be publicly
available. Even where gas flaring and fugitive emissions are monitored, the measurement tools
currently available are subject to a degree of inaccuracy determined by the physical
characteristics of the measurement system. Flare efficiency may also be subject to factors beyond
the control of oil companies, such as local wind conditions. To test the robustness of the results,
we undertook a sensitivity analysis in which key input parameters were varied for three typical
cases (low-, medium-, and high-intensity fields). Emissions from high-intensity fields that flare
are inevitably sensitive to the parameters that determine flaring emissions. For example, when
we used the Canadian model of a default flaring value instead of estimating flaring on the basis
of data about the oil fields, the intensity of the high-intensity case was reduced by nearly 30%.
Varying other parameters resulted in changes of less than 10%.
K. TANK BOTTOMS AND HEAVY HYDROCARBONS
Tank bottoms are defined by the API as basic sediment with water and other materials that
collect in the bottom of treatment and storage vessels, such as production separators fluids
treating vessels, and production impoundments. Tank bottoms can contain hydrocarbons, heavy
metals, sands, emulsions and other solids, which can affect human health and environment. The
API considers tankbottoms to be in the same category as pit sludge’s, paraffin’s and pigging
wastes generated in gathering lines and finds that the primary environmental consideration when
managing these types of waste by maximizing hydrocarbons recovery. There are a number of
innovative reclamation processes, which can be utilized either on or off-site to facilitate
hydrocarbons recovery. Prior to recycling, reclamation and /or disposal, these wastes should be
managed in tank or lined pits or in lined diked piles properly to protect vegetations and surface
waters. Tank bottoms contain heavy metals; hydrocarbons and other solids so before disposed on
off site, it should be checked for flash point, leach able heavy metals content and density and
compared with the results of the road mix oil. There may be permits or other authorization
required from state agencies before road-spreading practices are allowed or sell to road
construction agencies.
TREAMENT
The volume of solids collected in storage tanks been minimized.
Tanks designed to reduce the volume of produced tank bottoms (for example, cone-
shaped bases)?
Gas blanket kept on tanks to reduce oxygen and formation of iron oxides.
Installation of return line to run bottoms through heat-treaters more frequently than
normal.
Have sources of solids been identified? If yes, have engineering or operations solutions
been attempted?
If oil is reclaimed onsite or sent to reputable reclaimer.
Are light oil tank bottoms treated in heavy oil dehydration facilities.
The tank bottoms sent to a refinery coker.
Centrifuge or filter press used to recover oil and water form tank bottoms.
Re-circulation pumps are added to product storage tanks to reduce the settling of heavy
hydrocarbons on tank bottoms.
L. WORKOVER AND COMPLETION WASTES.
Workover and completion wastes result from operations where an oil well’s head is partially
open to the atmosphere and is filled with a water base fluid that maintains pressure on the
formation to prevent blowout. Workover fluid is injected into such a well while the well’s
interior tubing string, valves, packer gaskets, or other components are undergoing maintenance.
When maintenance is complete, the workover fluid is removed from the well before starting
routine operation. Completion fluids are typically used in a well when the well casing is
perforated just before starting production. Both fluids become contaminated with oil and
formation brine. Standard practice for handling workover and completion wastes calls for
separating the oil from the fluid and recycling both the oil and the fluid by filtering and adding
more solute to make up for dilution by formation brine. Although the oil can easily be recycled,
after several uses the base fluid can no longer be brought back to specification. Unreclaimable
fluid is presently disposed of through subsurface injection, but better ways to recycle these fluids
are currently being investigated by industry researchers. One technique to minimize excess fluid
production is to use a continuous mix process, rather than a batch, producing only enough fluid
to fill a well. Selection of fluid components that simplify this process, such as hydrogen sulfide
scavengers, should encourage its use.
M. USED OR SPENT SOLVENTS: Solvents are used in tasks such as cleaning, degreasing, and
painting. Unused solvent intended for disposal is considered a waste.
TREATMENT
ON-SITE RECYCLING: On-site recycling is economical when approximately 8 gallons of
solvent waste is generated per day (Schwartz, 1986). The simplest form of solvent reuse is
termed “downgrading,” which is the use of a solvent that has become contaminated through
initial use for a second cleaning process. For example, precision bearings need very high purity
solvents for cleaning. The solvent acquires very little contamination in usage and can be
downgraded or used for less demanding cleaning operations. More effort is required to recycle
solvent that has become heavily contaminated and the possibilities for both on-site and off-site
recycling or reclamation need to be explored. In vapor degreasing and cold cleaning, the soil
removed accumulates in the equipment. Eventually the solvent becomes too contaminated for
further use and it must be reclaimed or disposed of via incineration. For on-site recycling, many
different separation technologies are available. Commonly used separation technologies for
contaminated solvents include gravity separation, filtration, bath distillation, fractional
distillation, evaporation, and fuel use.
GRAVITY SEPARATION
The use of settling to separate solids and water from solvent often permits the reuse of solvent.
For example, paint thinners may be reused many times if solids are allowed to settle out.
FILTRATION
Filters can be used to remove solids from many solvents thus extending solvent life.
BATCH DISTILLATION
A batch still vaporizes the used solvent and condenses the overhead vapors in a separate vessel.
Solids or high boiling residues (>4000F) remain in the still as a residue. Solvent stills range in
size from 5 gallon to 500 gallon capacity. A vapor degreaser can be used as a batch still for
recycling solvent. This is often done by employing proper boil-down procedures. Detailed
discussion of these procedures is available from major solvent suppliers. In many applications, it
is necessary to keep the water content of the recovered solvent to less than 100 ppm. This can
often be accomplished by distilling off the solvent-water azeotrope, decanting the water, and
then drying the remaining solvent with a molecular sieve, or other desiccant. The water removed
in this operation must then be either treated or drummed for disposal.
FRACTIONAL DISTILLATION
Fractional distillation is carried out in a refluxed column equipped with either trays or packing.
Heat is supplied by a reboiler located at the bottom of the column while heat is removed at the
top of the column by a condenser. Fractional distillation allows for separation of multi-
component mixtures or mixtures of solvent and oils with very similar boiling points.
EVAPORATION
Evaporation can be employed for solvent recovery from viscous liquids, sludges, or still bottoms
resulting from distillation. Scraped or wiped-film evaporators utilize revolving blades which
spread the liquid against a heated metal surface. The vapors are recovered by means of a
condenser. Another type of system, a drum dryer, employs two heated counter-rotating drums
through which the liquid feed must pass. While both systems can handle viscous wastes, the
drum dryer is more tolerant of polymerizable contaminants.
OFF-SITE RECYCLING
If recycling of waste solvent on site is impractical, several off-site recycling schemes are
available.
RECYCLING SOLVENTS EFFICIENTLY
Segregating solvent wastes is usually an essential step prior to recycling. IBM Corporation
reported that segregation may also-increase recycling efficiency; segregating non-chlorinated
from chlorinated solvents resulted in 15 to 20 percent greater yields (Waste Reduction - The
Untold Story, 2985).
MOBILE SOLVENT DEGREASING UNITS
Automobile repair shops in California can lease fully-contained degreasing systems from Safety
Kleen Inc. Safety Kleen provides a batch-tolling service for degreasing solvents; it leases its
mobile units, including solvents, as one system. Safety Kleen periodically replaces the spent
solvent with fresh solvent, and recycles the spent solvent at a separate facility.
WASTE EXCHANGES
Waste exchanges generally exchange some 20 to 30 percent of the wastes they list (Banning,
1983, 1984). At present, the most common wastes listed are solvents and metal wastes. Other
wastes listed include acids, alkalis, other inorganic chemicals, organics and solvents, and metals
and metal sludges.
Toll recyclers: Toll recyclers offer services to generators by supplying solvent wash equipment
and solvent and waste recycling services. The solvent wash equipment is maintained by these
companies and the solvent is replaced periodically. The used solvent is recycled at an off-site
facility. Costs for these services range from 50-90% of new solvent cost.
WASTE EXCHANGE AND BROKERAGE
This is not a technology but an information service. A waste exchange can match a generator of
waste with a facility that can use the waste as a raw material. Commercial waste brokerage
services are also available. A waste generator is matched with a potential waste user who can
utilize the waste as a feedstock. Matching generators and users is based on the knowledge of raw
material inputs and wastes and product outputs of individual industries and firms.
Used Oil and Filters : Used Oil if managed improperly can potentially contaminate drinking
water. In fact, used oil from one oil change can contaminate 1 million gallons of fresh water - a
years' supply for 50 people! Moreover, used oil may be considered hazardous waste depending
on how it is disposed of or mixed with other wastes. Below you will find resources to help
owners and operators properly manage their used oil and filters.
Fueling : While gasoline offers a great advantage to us by powering our cars and buses, it has
some drawbacks too. Gasoline is composed of over 200 different chemicals, but there are four
that are toxic to humans – benzene, toluene, ethyl benzene, and xylene. When people pump
gasoline into their cars, the vapors escape into the atmosphere and can get into people’s lungs
when they breathe and also be deposited on their skin. Gasoline also evaporates very quickly and
pollutes the atmosphere. Certain chemicals called volatile organic compounds (such as benzene)
react with sunlight and form smog in urban areas. Moreover, spills of gasoline can contaminate
our drinking water supplies. A spill of one gallon of gasoline can render one million gallons of
water undrinkable. Finally, gasoline is flammable. A spark can ignite gasoline vapors. Below
you will find resources to help owners and operators manage their fueling operations in such a
way as to miminize its harmful effects, including the installation of vapor recovery systems
which is required for certain areas or gas stations with high monthly throughput under the Clean
Air Act.
Proppants/frac sand: Proppants (also called “frac sand”) refers to the aluminum silicate beads
of varying sizes injected into wells to hold formation fractures open, thus increasing subsurface
oil flow to the wells. When these materials are transported back to facilities with crude oil from
the wells, the beads settle out, along with formation sand, to form a semi-solid sludge in the
bottoms of vessels. This proppant/frac sand now goes into lined landfills in South Alaska, but it
has been suggested that the material could be sold as construction fill if it could be separated
from the crude oil. Janet Platt of BP. Exploration noted that BP considered constructing an oily
waste facility that would have separated the recyclable solids from the oil, but the company
cancelled the project because the viewed as prohibitive. Roundtable participants also raised
concern that less of this proppant/frac sand will likely be produced in the future, making
recycling less feasible economically.
Bottom wastes: Tank bottom wastes are a type of sediment that accumulates in oil field vessels
and pipelines when fluid turbulence is low. These dense sludges are composed of crude oil,
paraffin, asphaltics, reservoir material, drilling mud, and slightly radioactive material (called
NORM--“naturally occurring radioactive material”), in addition to the frac sand/proppant
discussed above. Historically, bottom waste has been put into lined oily waste pits either for
permanent burial or for temporary storage until it can be treated to remove hydrocarbons, usually
by thermal processes. As mentioned previously, BP designed a plant using solvent extraction to
recover salable crude oil from bottom wastes, plus a recyclable solid for construction purposes.
This waste stream was strongly suggested by roundtable participants as a subject for future
research, as it represents a large, potentially toxic waste stream which is not recycled. Partially
cleaned solids might be safely recycled by incorporating them into Portland cement or other
materials for oil field applications. As with drill cuttings, determining acceptable levels of trace
contaminants and methods of reducing analytical costs might also prove fruitful topics for
research.
Dehydration and sweetening wastes: Polyols and glycols are used in the oil and gas industry as
antifreeze and to remove traces of water from natural gas streams in the production of fuel gas. It
was mentioned in the course of the roundtable discussion that waste dehydration polyols and
glycols sometimes emit traces of benzene. Identifying an inhibitor chemical or process of
benzene formation in these processes was suggested as a worthwhile research objective. A
general study of how to reduce or inhibit contamination of triethylene glycol (TEG) and methyl
ethyl glycol (MEG) streams, perhaps by using alternative dehydrating agents, might also be
worthwhile. Hydrogen sulfide (H2S), a corrosive gas more toxic than hydrogen cyanide, is
emitted by sulfate-reducing bacteria growing in subsurface formations and oil field surface
equipment. The evolution of hydrogen sulfide is currently inhibited by using powerful biocides
like acrolein and formaldehyde; unfortunately, these biocides are highly toxic and dangerous
materials. The best way to avoid spills of these materials might be to institute a research and
development project find an effective, but less toxic, biocide to use in their place.
USED OIL AND USED OIL FILTERS:
Engines and other machinery in all areas of operations require lubricating oil and oil filters.
DRUMS AND CONTAINERS: Drums and containers are required for delivery and storage of
chemicals and materials used in all areas of operations.
SANDBLAST MEDIA: Sandblasting is typically used to prepare equipment for painting and to
remove scale from equipment.
PAINT AND PAINT WASTES: Painting is generally required for maintenance of equipment.
Paint thinners, solvents, and unused paint are generated wastes.
PESTICIDES AND HERBICIDES: These chemicals are used to control insects and vegetation at
various locations (e.g., drilling locations).
VACUUM TRUCK RINSATE: Vacuum trucks recover waste liquids generated by various
operations.
SCRAP METAL: Scrap metal consists of damaged tubular or other equipment, crushed drums,
remnants of welding operations, cut drill line, etc. Scrap metal may contain naturally occurring
radioactive materials (NORM). Scrap metal Sheet metal, piping, tubing, wire, cable, empty
drums/containers, tanks, pump housings, valves, fittings, vehicle/equipment parts