CH9

Slide 1 GEOL4324: Geology of Hydrocarbons

Ch9: Nonconventional Petroleum Resources

GEOL4324: T & Th 2:00GEOL4324: T & Th 2:00--3:20pm3:20pmGeology of HydrocarbonsGeology of Hydrocarbons

Prof. HuaProf. Hua--wei Zhouwei ZhouRm211 of Science, Rm211 of Science, x21308x21308, , [email protected]@ttu.eduOffice Hours: T & Th 11amOffice Hours: T & Th 11am--noon, 3:30noon, 3:30--5pm, 5pm,

or by appointmentor by appointment



Ch6: Reservoir continuity & characterization. Reserve calculations3/916

Ch6: Production methods; QZ4 (Ch6)3/1117

Ch6: Texture relating to porosity & perm. Effects of diagenesis on reservoir quality3/415

Ch6: The Reservoir: Porosity & permeability. Capillary Pressure. Grain texture3/214

Ch5: Petroleum system & basin modelling. QZ3 (Ch5)2/2513

Ch5: Formation of Kerogen. Petroleum migration2/2312

Ch5: Origin of petroleum. Modern surface organic processes2/1811

Midterm Exam One (Ch1-4)2/1610

Ch4: Subsurface fluid dynamics. Preview for Midterm One2/119

Ch4: Subsurface environment: waters. Subsurface temperatures & pressures2/98

Ch3: Subsurface geology. Remote sensing. QZ2 (Ch3)2/47

Ch3: Non-seismic & seismic methods. Borehole geophysics and 4D seismics.2/26

Ch3: Formation evaluation w/ various loggings. Intro to geophysical methods1/285

Ch3: Exploration: drilling & completion. Formation evaluation w/ e-logs1/264

Ch2: Crude oil chemistry & classification; QZ1 (Ch1-2)1/213

Ch2: Properties of various gases & gas hydrates1/192

Ch1: Historical review of petroleum exploration1/141

ContentDate#

Syllabus (adjustable)



Final Exam5/629

Ch10: Assessment of basin & global reserves. Course review for Final Exam4/2728

QZ7 (Ch9); Ch10: Prospect appraisal. Geology, economics & probabilities4/2227

Ch9: Oil shales. Extraction of oil and oil shales. Shale gas & coal bed methane4/2026

Ch9: Plastic & solid hydrocarbons. Tar sands4/1525

Ch8: Distribution of hydrocarbons in basins; QZ6 (Ch8)4/1324

Ch8: Plate tectonics. Cratonic basins, troughs, rift basins & strike-slip basins4/823

Ch8: Formation & classification of sedimentary basins4/622

Midterm Exam Two (Ch5-7)4/121

Ch7: Review of Ch6 & Ch7. QZ5 (Ch7); Preview for Midterm Two3/3020

Ch7: Structural, diapiric, stratigraphic & hydrodynamic traps3/2519

Ch7: Traps: Nomenclature, petroleum distribution & classification. Seals and cap rocks3/2318

Spring Break3/18

Spring Break3/16

ContentDate#

Syllabus (adjustable)



Ch9: Nonconventional Petroleum ResourcesCh9: Nonconventional Petroleum Resources

1.1. Plastic & solid hydrocarbonsPlastic & solid hydrocarbons

2.2. Tar sandsTar sands

3.3. Oil shalesOil shales

4.4. Shale gas & coalShale gas & coal--bed methanebed methane



1.1. Plastic & solid hydrocarbonsPlastic & solid hydrocarbonsClassificationClassification



1.1. Plastic & solid hydrocarbonsPlastic & solid hydrocarbonsOccurrenceOccurrenceTwo genetically distinct modes of occurrence:Two genetically distinct modes of occurrence: Inspissated & secondary depositsInspissated & secondary deposits

Inspissated depositsInspissated depositsThese are heavy hydrocarbons from which the light fraction has been removed. The situation can occur where an accumulation of liquid oil has been brought to the surface of the earth by a combination of migration, coupled with uplift and erosion. The oil will be subjected to flushing by meteoric water, leading to oxidation & bacteria degradation.

Surface occurrence of asphalt may be Surface occurrence of asphalt may be produced from seepages escaping from oil produced from seepages escaping from oil fields in the subsurface in various ways.fields in the subsurface in various ways.




Inspissated depositsInspissated depositsIn the seepages on the shores of the Caspian Sea, such as Baku, not only oil but also mud and gas pour out on the earth’s surface. Spontaneous ignition frequently occurs, so that this region has been called the land of Eternal Fires.

Caspian SeaCaspian Sea




Inspissated depositsInspissated depositsPetroleum seeps also occur offshore, in the Santa Barbara Channel of California, and off the coasts of Trinidad, Yucatan, and Ecuado.

Gas seeps, possibly of both shallow biogenic and thermal origin, are commonly recorded on sparker surveys around the world, and a major hazard to drilling and pipeline laying operations.




Secondary depositsSecondary depositsThese are admixtures of sediment and heavy

degraded oil.

Extensive deposits of secondary petroleum are extremely rare, due to the tendency for oil to be degraded and oxidized in air & water.

Secondary deposits are occasionally found around oil seeps and mud volcanoes. They are important to help date the migration of petroleum.



1.1. Plastic & solid hydrocarbonsPlastic & solid hydrocarbonsCompositionComposition

Waxy solid hydrocarbons Waxy solid hydrocarbons are produced by the inspissation of paraffinic crude oils. They are generally plastic, waxy yellow to dark brown substances called ozokerite.

Chemically, the waxy solid hydrocarbons are paraffin derivatives, ranging from C22 to C29, with 84-86% carbon, 14-16% hydrogen, and traces of sulfur & nitrogen.

Asphaltic solid hydrocarbons Asphaltic solid hydrocarbons are produced by inspissation of naphthenic crude oil.

These compounds are similar to the waxy solid hydrocarbon in elemental chemistry, with 79.5-87.2% carbon, 8.9-13.2% hydrogen, <8% sulfur, and commonly traces of nitrogen, oxygen, and inorganic compounds.

Relative to that of the waxy solid hydrocarbons, the molecular composition of asphaltic solid hydrocarbons has much less paraffins & naphthenes, more aromatics, oxygen, nitrogen and sulfur.

As the asphalts are subject to inspissation, they grade through the asphaltites to asphaltic pyrobitumen.



1.1. Plastic & solid hydrocarbonsPlastic & solid hydrocarbonsCompositionCompositionAsphaltic solid hydrocarbons Asphaltic solid hydrocarbons

The asphaltites have a specific gravity of <1.2 and a melting point of 120-320oC. They are <60% soluble in naphtha and 60-90% soluble in carbon disulfide.

The asphaltic pyrobitumen are rubbery, brown substances with a specific gravity of <1.25. They do not melt, but swell and decompose on heating. They are insoluble in naphtha and only slightly soluble in carbon disulfide.



1.1. Plastic & solid hydrocarbonsPlastic & solid hydrocarbons

Composition & evolution of Composition & evolution of the solid hydrocarbons.the solid hydrocarbons.



1.1. Plastic & solid hydrocarbonsPlastic & solid hydrocarbonsSpace for self summarySpace for self summary



2.2. Tar sandsTar sandsCompositionComposition

Heavy, viscous oil depositsoccur at/near the surface of the Earth in many parts of the world.

These deposits have API gravities in the range of 5-15o

and typically occur within highly porous sands, generally referred to as tar sands, or oil sands.

Canadian Tar Sands

Tar sands specimen close-up photo. From Asphalt Ridge near Vernal, Utah. Source: Argonne National Laboratory




Heavy, viscous oil depositsoccur at/near the surface of the Earth in many parts of the world.

These deposits have API gravities in the range of 5-15o

and typically occur within highly porous sands, generally referred to as tar sands, or oil sands.

Canadian Tar Sands



2.2. Tar sandsTar sands

Vast reserves of Vast reserves of hydrocarbons are hydrocarbons are contained in tar sands!contained in tar sands!

Notice error in the Notice error in the amount of reserves of amount of reserves of this table!this table!

CompositionComposition



2.2. Tar sandsTar sandsCompositionCompositionIn terms of physical and chemical properties, the change from normal crude oil, via heavy oil, into tar is a gradual one.

Physically, the oils become heavier & more viscous. Chemically, the oils tends to contain more inorganic impurities and to be more sulfurous and aromatic.

Comparing the composition of a number of tar sands with light crudes in Fig. 9.6, tar sands tend to be enriched in resins & asphaltenes, and impoverished in saturated hydrocarbons. There is not as much difference in their aromatic content.




Two possible explanations have been proposed to account for the differences between normal light crudes & tar sands.

Firstly, the heavy oils of tar sands may be young and have yet to mature to light oil.

Alternatively, the heavy oils of tar sands may have been produced by the degradation of mature light oil.

Degradation occurs by both organic & inorganic processes. Nonetheless, the origin of heavy oils is controversial.



2.2. Tar sandsTar sandsGeologic settingGeologic setting

Let consider the geologic setting of tar sands.

The majority occur where major basins transgress over Precambrian shields.

They occur in fluvial or deltaic sands, rather than marine sands or carbonates.

On a smaller scale tar sands occur in two ways:

in situ in erosionally breached traps (e.g., Bemolanga oil sands of Malagasy);

migrated from deep traps into surface seepages (e.g., La Brea deposits of Trinidad & Athabasca tar sands of Canada).



2.2. Tar sandsTar sandsGeologic settingGeologic settingThe The BemolangaBemolanga tar sands of Malagasytar sands of MalagasyOccur in the Isalo Group (Triassic) of the Karroo system, covering an area of ~388 km2 with an overburden of >100 m in thickness.

The tar sands lie within a complex faulted anticline, where the cap rock of the Bemolanga clay has been removed by recent erosion.

The sands are cross-bedded, coarse, and fluvial. Local dykes of Cretaceous age have locally metamorphosed the tar. The underlying Sakamena shale is believed as the source for the oil.

The average pay is ~30 m thick, and reserves is ~ 1.75 b. bbl.



2.2. Tar sandsTar sandsGeologic settingGeologic settingThe La Brea tar sands of TrinidadThe La Brea tar sands of Trinidad

Oil of the 126-acre La Brea asphalt lake has emigrated from an accumulation in a Cretaceous anticline up through an imperfect seal to reach the surface.

The tar sands lie in a depression within Miocene sands; it is still actively flowing, as shown by modern mud volcano activity.The estimated reserves is 60 million barrels.



2.2. Tar sandsTar sandsGeologic settingGeologic settingThe La Brea tar sands of TrinidadThe La Brea tar sands of Trinidad

Oil of the 126Oil of the 126--acre La Brea asphalt lake has emigrated acre La Brea asphalt lake has emigrated from an accumulation in a Cretaceous anticline up from an accumulation in a Cretaceous anticline up through an imperfect seal to reach the surface.through an imperfect seal to reach the surface.

The tar sands lie in a depression within Miocene sands; The tar sands lie in a depression within Miocene sands; it is still actively flowing, as shown by modern mud it is still actively flowing, as shown by modern mud volcano activity.volcano activity.The estimated reserves is 60 million barrels.The estimated reserves is 60 million barrels.



2.2. Tar sandsTar sandsGeologic settingGeologic settingThe Athabasca tar sands of CanadaThe Athabasca tar sands of CanadaThe heavy oil occur in fluviodeltaic sands of the Manville Group (Lower Cretaceous), which where derived mainly from the west, but with local deltaic spreads of sand from the east. Subsequently, the strata were tilted regionally to the west and very gently folded.

Normal light oils (35-40o API) were generated in the western part of the Alberta basin, but tar sands are now encountered in stratigraphic pinchout and fold-pinchout combination traps along the eastern margin.



Schematic section showing oil trapped in sands and carbonates (from Proctor et al., 1983).

2.2. Tar sandsTar sandsGeologic settingGeologic settingThe Athabasca tar sands of CanadaThe Athabasca tar sands of CanadaThe heavy oil occur in fluviodeltaic sands of the Manville Group (Lower Cretaceous), which where derived mainly from the west, but with local deltaic spreads of sand from the east. Subsequently, the strata were tilted regionally to the west and very gently folded.

Normal light oils (35-40o API) were generated in the western part of the Alberta basin, but tar sands are now encountered in stratigraphic pinchout and fold-pinchout combination traps along the eastern margin.

Index map of oil sands, carbonate triangle, heavy oil, and deep-basin gas (from Proctor et al., 1983).



2.2. Tar sandsTar sandsOrigin of tar sandsOrigin of tar sands

The origin of tar sands is controversial. The debate revolves around whether the oil is immature, or mature and subsequently degraded.

An early idea stated that the oil was formed in the sands that now contain them. The reasons included the flat-lying nature of the sediments and the apparent absence of normal crudes in the area.

Another idea is that the heavy oils are mature oils that have undergone degradation by meteoric flushing. The reason included cases that oils can be traced gradationally up the basin margin from deep light oil pools. The gradational lightening of the oil basinward is accompanied by increased formation water salinities.

One more idea is the immature origin. The evidence includes their higher porphyrin content, the absence of insoluble benzene matter, their molecular weight distribution, and their nickel:vanadium ratio. Also the chemical composition of the oil shows that it has not undergone significant thermal maturation.



2.2. Tar sandsTar sandsExtraction of oil from tar sandsExtraction of oil from tar sandsDuring the last half century, the low cost of conventional light crude inhibited interest in heavy oil production, and little research was put into the technology of extracting the oil from tar sands.

The situation is rapidly changing due to the huge price rises of crude oil and the ultimate global shortage of conventional oil.

The methods extracting heavy oil include:

Surface mining

Tar Sands Open Pit Mining, Alberta, Canada






Surface mining

Tar Sands Extraction Separation Cell, Alberta, Canada






Surface miningSubsurface extraction



2.2. Tar sandsTar sandsExtraction of oil from tar sandsExtraction of oil from tar sandsProblems of strip mining tar sands include:

The economic thickness of overburden that can be tolerated;The degree of environmental opposition of the native population

Once the tar sands have been quarried, the extraction consists of disaggregation of the sand and separation of the oil by hot water and/or stem.

Where the overburden is too thick for open-cast mining, in situ extraction methods are developed:

Injection of solvent to dissolve the oilSeeking to reduce the oil’s viscosity be heating

The technology of extracting oil from tar sands still has long way to go, and is the subject of current research.



2.2. Tar sandsTar sandsSpace for self summarySpace for self summary



3.3. Oil shalesOil shalesDefinitionDefinition

Oil shale is a fine-grained sedimentary rock that yields oil on heating.

Fractured oil shale specimen showing weathered and unweathered surfaces. UintaBasin, Utah. Source: Argonne National Laboratory



3.3. Oil shalesOil shalesDefinitionDefinition

Oil shale is a fine-grained sedimentary rock that yields oil on heating.

It differs from tar sand in more than grain size. In tar sands the oil is free and occurs within the pores. In oil shales, however, oil seldom occurs free, but is contained within the complex structure of kerogen, from which it may be distilled.

Craig (1915) wrote: “To make the matter clear, the relation of malt & hops to beer is somewhat similar to that of oil shales, coal &lignite to petroleum. The malt & hops do not contain beer, but it can be made from them by causing certain chemical changes. Oil can be made from oil shales, coal & lignite, but only by destroying them.”

Combustion of oil shale

Oil shales are widely distributed around the globe and may contain locked within them more energy than in all the presently discovered conventional oil reserves. The world’s oil shales may contain ~30 trillion bbl of oil, only about 2% of which is accessible using present-day technology (Yen & Chilingarian, 1976).



3.3. Oil shalesOil shalesChemical compositionChemical composition

Most oil shales are essentially claystones & siltstones, but bituminous marls and lime mudstones are also known. The basic constituents of oil shales may be grouped as follows:

1. Inorganic components (<90%)1. Inorganic components (<90%)QuartzFeldsparMica

Detrital Accessory mineralsCarbonatesClays AuthigenicPyrite

2. Organic components (102. Organic components (10--27%)27%)Bitumens (hydrocarbons soluble in CS2) around 2%Kerogens (insoluble in CS2) around 8%



3.3. Oil shalesOil shalesChemical compositionChemical composition

The exact amount of organic matter needed before a shale can be classified as an oil shale is arbitrary. A cut off value of 10% has been cited. With increasing organic content to more than 27%, oil shales grade into the cannel coals.

The inorganic component of oil shales differs little from that of conventional shales. Detrital grains include quartz, feldspar, mica. Large amount of clay are present, both detrital floccules & authigenic crystals. Various carbonate minerals are present. Authigenic pyrite also presents, carrying sulfur which causes a major problem of oil shale refining.

Kerogen is the important constituent of oil shale. An oil definition of kerogen by Stewart (1912) is “carbonaceous matter in shale which gives rise to crude oil on distillation”. Currently, kerogen is defined and distinguished from bitumen by its insolubility in carbon disulfide.

The organic precursor of the kerogens in oil shales are hard to determine, though thesource of the organic matter of most oil shales is generally believed be admixtures of algal & terrestrial humic materials. Two rare types of oil shale whose biological origin is well know are Torbanite & Tasmanite. Torbanite, also termed bog head or cannel coal, are made of algal matter. Tasmanite occurs in marine deposits.



3.3. Oil shalesOil shalesDistributionDistributionThe occurrence & distribution of oil shales are widespread in place & time.

There appear to be few genuine Precambrian oil shales.

In the early Paleozoic, however, siliceous oil shales were deposited on marine shelves throughout the Northern Hemisphere.

In the late Paleozoic, oil shales were deposited on marine shelves in central European Russia and in the central & eastern US and Canada.

At the Devonian-Carboniferous boundary oil-shale-forming environments appear to have changed significantly. Paralic deltaic-lacustraine oil shales are characteristic of Carboniferous deposits worldwide.

During the Permian period both paralic & marine shelf oil shales formed. The Iratioil shale of this age covers several hundred thousand km2 in eastern South America and South Africa.



3.3. Oil shalesOil shalesDistributionDistributionDuring the Permian period both paralic & marine shelf oil shales formed. The Irati

oil shale of this age covers several hundred thousand km2 in eastern South America and South Africa.



3.3. Oil shalesOil shalesDistributionDistributionIn late Mesozoic time many oil shales formed in marine, deltaic, and lacustrine environments. In NW Europe, a major phase of oil shale and organic-rich shale deposition began in N. Germany in the Liassic and moved diachronically northward up the North Sea into the East Greenland Mesozoic basin. Analogous marine platform oil shales occur in Alaska, Saskatchewan, Manitoba, and in Nigeria.

The Cenozoic Era saw another return to lacustrine oil shale deposition, although marine oil shales do occur. The best example is the Eocene Green River Formation of Colorado, Utah & Wyoming.



3.3. Oil shalesOil shalesDistributionDistribution

Three major depositional environments are favourable for oil shale generation: Lakes, fluvially dominated deltas, & certain marine shelves.

Torbanites & oil shales of mixed humic and nonmarine algal origin are characteristic of lacustrine & deltaic shales.

Shallow marine oil shales, however, are commonly of mixed humic and marine algal composition, including the rarer algally dominated tasmanite variety.

Oil shales of both lacustrine & marine types are occasionally associated with autochthonous chemical deposits.

The world’s reserves of shale oil are estimated to be on the order of 30 trillion bbl, and the US alone contains >0.7 trillion bbl (Yen & Chilingarian, 1976).



3.3. Oil shalesOil shalesExtraction of oil from oil shaleExtraction of oil from oil shale

Production of oil shale (megatons) in Estonia, Russia (Leningrad & Kashpirdeposits), UK (Scotland, Lothians), Brazil (IratíFormation), China (Maoming & Fushun deposits), and Germany (Dotternhausen) from 1880 to 2000.

The commercial extraction of oil from shale was begun by James Young in Scotland in 1862. During the next century, oil shale extraction was carried out in England, France, Spain, Sweden, Australia, & South Africa. The industry has since collapsed in these countries.

The Figure below shows the peak of oil shale production around 1980. The main producing countries include Estonia, China, Russia & Brazil. Two reasonsTwo reasons for the rise and fall of the oil shale extraction are economics & technologyeconomics & technology. So we expend the trend to pick up again.



3.3. Oil shalesOil shalesExtraction of oil from oil shaleExtraction of oil from oil shaleLike the tar sands, there are two basic methods of winning oil from shale:

(1) By retorting shale quarried at the surface: Shale is crushed on the open-cast quarry, then placed in a retort and heated. Several sources of heat can be used, but the most efficient is by the combustion of gas previously generated from the shale. As the shale is heated in the range of 425-475oC, oil and gas are driven off by the pyrolysis of the kerogen. Spent shale collects at the bottom of the retort. The oil is refined, the gas reinjected, and the ash cooled and disposed of, it is hoped at least partly back in the hole whence it came. This method has considerable environmental objections.

(2) By underground in situ extraction: Two requirements are that an effective method of heating the shale is available and the rock must be rendered permeable. Several example case were described in the text.

The day may come soon when the rising cost of conventional crudeThe day may come soon when the rising cost of conventional crude oil intersects oil intersects the coast of shale oil.the coast of shale oil.



3.3. Oil shalesOil shalesSpace for self summarySpace for self summary



4.4. Shale gas & coalShale gas & coal--bed methanebed methaneShale gasShale gasShale gas is natural gas produced from shale. Because shales ordinarily have insufficient permeability to allow significant fluid flow to a well bore, most shales arenot sources of natural gas. Shale gas is one of a number of “unconventional”sources of natural gas, usually from fractured shale reservoirs.

In the US petroleum gas was first produced from fractured shale reservoir in 1821. Extensive shale gas production was established in the Appalachian basin, and there are many other potential areas for shale gas production throughout the US.



4.4. Shale gas & coalShale gas & coal--bed methanebed methaneShale gasShale gas

Shale gas is seldom trapped in well-defined fields; instead it occurs in siltstone bands and irregular fracture systems. The gas is of high calorific value, and commonly wet, with >10% ethane. After an initial high pressure “blow” well head pressures stabilize at 300-500 psi with flow rates of 50-100 thousand cubic feet of gas per day. Depletion rates however are of the order of 10% per year, with individual wells producing for 40-50 years. Wells are seldom >700 m deep, and thus cheap to drill.

Shale gas exploitation is not profitable for major international oil companies, because the reserves are too small and the payout time too long. Shale gas is economically viable in the US because land ownership includes the mineral rights of a property, and the “cottage industry’ scale of many small oil companies permits operations with small profit margins.



4.4. Shale gas & coalShale gas & coal--bed methanebed methaneShale gasShale gas

It is now known that the regional distribution of shale gas is controlled by the quantity, quality, and level of the maturation of organic matter in the shale formations. Local concentrations of shale gas occur either in siltstone strata or in fracture systems.

Siltstone beds commonly occur in the syndepositional lows that are carefully avoided in conventional petroleum exploration.



4.4. Shale gas & coalShale gas & coal--bed methanebed methaneShale gasShale gasUK also has good potential for shale gas. This figure shows the main Carboniferous features of Britain. During the early Carboniferous, N Britain consisted of a serious of stable platforms and subsiding basins. Limestones were deposited on the former and shales in the latter. The shales are rich in organic matter, ranging from the Tasmanites-bearing oil shales of the Midland Valley of Scotland to the more humic shales of N. England.



4.4. Shale gas & coalShale gas & coal--bed methanebed methaneShale gasShale gasRemote sensing and seismic surveys may help located fracture systems, which may be best developed where strata are stretched over the crests of anticlines, or along regional fault and basin hinge-line trends. Specific methods of seismic survey and processing have now been developed to locate low-velocity gas-charged shale zones.

Shale gas is found by air drilling. Conventional drilling with a mud-filled hole will seldom locate shale gas. The weight of the mud forces the gas away from the well bore. Such gas as may escape into the drilling mud is recorded as “background gas”, with little thought that it may be commercial.

Transportation of shale gas far from the well head is seldom feasible. Because of the low pressure, the gas must be pressurized for it to flow along a pipeline. This additional cost generally destroys the profitability. Hence, shale gas is an eminently suitable energy source when located adjacent to a town or users.

Shale gas production has a negligible environmental impact. Once the well is drilled there is no derrick. There is no need for well-head pumps, no flaring, and no long-distance pipelines. The production is modest, but reliable, quiet, and long term.



4.4. Shale gas & coalShale gas & coal--bed methanebed methaneCoalCoal--bed methanebed methaneCoal-bed methane (CBM), also called coal-bed gas, is a form of natural gas extracted from coal beds. The methane is adsorbed into the solid matrix of the coal. It is 'sweet' because of its lack of hydrogen sulfide. A truckA truck--mounted drill rig used by gas mounted drill rig used by gas

developers for shallow drilling of developers for shallow drilling of coalcoal--beds in the Powder River Basin. beds in the Powder River Basin.

Traditionally CBM is a major safety hazard to coal miners. Extensive ventilation systems are required to extract methane from working coal mines.

CBM is distinct from a typical sandstone or other conventional gas reservoir, as the methane is stored within the coal by a process called adsorption. The methane is in a near-liquid state, lining the inside of pores within the coal matrix. The open fractures in the coal can also contain free gas or can be saturated with water.



4.4. Shale gas & coalShale gas & coal--bed methanebed methaneCoalCoal--bed methanebed methane

Unlike shale gas, most coals only produce dry gas, methane. The goal-bed gas thus have a lower calorific value than shale gas. Coal beds normally have more fractures and higher permeability than shales.

The parameters that control the methane-generating potential of a coal include: rank, ash content, maceral (component of coal) type, matrix porosity, fracture porosity, pressure, and water content.

CBM production(from EPA)



4.4. Shale gas & coalShale gas & coal--bed methanebed methaneCoalCoal--bed methanebed methane

A CBM treatment ponds on the Black Warrior River. (Jefferson County, Alabama)

CBM well in the foreground, Miller Steam Plant in the background. (Jefferson County, Alabama)

Nonconventional petroleum resources Nonconventional petroleum resources will play a much big role in the future!will play a much big role in the future!



Production of oil and gas in reservoirs with low primary permeability (e.g. carbonate and shale reservoirs) depend heavily on natural or induced fractures

Reservoir fracture & stress may be characterized based on seismic data (velocity anisotropy and micro-seismicity), together with geologic and production info

Extra information:Extra information:Reservoir fracture & stress characterizationReservoir fracture & stress characterization



Sections & volumes of seismic images

Seismic-well tie

Seismic attributes

Seismic anisotropy

Monitoring of micro-seismicity

o First motion strain axes of micro-seismicity?

o ‘Day light’ seismic imaging?

Reservoir fracture & stress characterizationReservoir fracture & stress characterizationSeismologic Contributions:Seismologic Contributions:



Reservoir fracture & stress characterizationReservoir fracture & stress characterization



Generalized stratigraphic column and detail of Mississipian strata


(Pollastro, 2003)



Isochron map of the reservoir (4ms intervals). The reservoir is slightly thicker towards the NE; the main fault does not define areas of different thickness, showing that the vertical displacement happened after reservoir formation

(Simon, 2005)




Time contours of the top of the reservoir (4ms contour interval) and azimuthal interval velocity icons. The azimuthal change in the velocity field around the fault is consistent with right-lateral strike-slip motion.

(Simon, 2005)





(Simon, 2005) 0300

600

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15001800

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36003900

Fast Int. Veloc.Mid-Reservoir

[ft/s]

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(FA

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Azimuth Arrows:Azim. Fast Int. Veloc.

Mid-Reservoir

FLAT AREA

LARGE K+CONVEX

SMALL K-CONCAVE

Km

axBO

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ColorColor--filled contours of filled contours of bottombottomreflector reflector KKmaxmax, and arrows of interval , and arrows of interval velocity attributes (azimuth & size is velocity attributes (azimuth & size is that of that of VfVf, color show , color show VfVf--Vs).Vs).

10K FT0







Definition: Capturing an interpreter’s thoughts with a computer algorithm。

Seismic attributes



Fault detectionFault detection (Gulf of Mexico, USA)(Gulf of Mexico, USA)

Salt

Salt



kpos < 0 kpos = 0 kpos > 0

kneg = 0

kneg > 0

kneg < 0bowl

plane

synform

saddle

antiform

dome(Bergbauer et al., 2003)

Geometrical Attributes：

Curvature of folded surfaces



Line 1

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Coherence AttributesCoherence Attributes

(Chopra and Marfurt, 2007b)



Line 1

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Most-Positive Curvature Strat Slices


PositivePositive curvaturecurvature



Line 1

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Most-Negative Curvature Strat Slices


NegativeNegative curvaturecurvature



B B′5 km

Caddo

Ellenburger

Basement?

pos

Amp

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neg

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e (s

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0.75

1.00

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A seismic section of the A seismic section of the FortworthFortworth BasinBasin



0.80

Time (s)

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B′5 kmTime/structure of Caddo horizonCaddoCaddo group group horizon structurehorizon structure



0.06

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B′5 kmDip magnitude from picked horizonCaddoCaddo group group dipping attributesdipping attributes



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CaddoCaddo group group NS dip attributeNS dip attribute



B

B′NS dip from multi-window scan

-2

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CaddoCaddo groupgroup windowed NS dip attributewindowed NS dip attribute



B

B′EW dip from picked horizon

-0.06

Dip (s/km)

0.00

+0.06

CaddoCaddo group group EW dip attributeEW dip attribute



B

B′

-2

Dip (deg)

0

+2

CaddoCaddo groupgroup EW dip from multiEW dip from multi--window scanwindow scan



-2

Dip (deg)

0

+2

ϕ=00ϕ=300ϕ=600ϕ=900ϕ=1200ϕ=1500

Time slices through apparent dip (t=0.8s)CaddoCaddo groupgroup



ϕ=00ϕ=300ϕ=600ϕ=900ϕ=1200ϕ=1500

Time slices through apparent dip (t=1.2s)

-2

Dip (deg)

0

+2

Caddo groupCaddo group



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Documents

CH9