drilling fluid contamination test

7/21/2019 drilling fluid contamination test

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1.0 ABSTRACT

This experiment conducted to study the effect of contamination of Gypsum (CaSO42H2O) tothe density, Plastic Viscosity (p) and Yield Point (Yp) of water based mud. Gypsum is one of thesalts that commonly encountered during drilling, completion or work over operations. Theexperiment started by preparing 200ml based mud in a Beaker A and Beaker B and the drillingfluid initially tested for weight, PV and Yp by using viscometer. Drilling fluid initially tested forweight, PV and Yp by using viscometer. After the values were recorded, about 5g of gypsumwere added in the beaker that contains water based mud. The mud containing gypsum is stirredfor 3 minutes. The values of viscosity, PV, Yp, density and pH value are recorded. Theexperiment was repeated by adding 10, 15 and 20 grams of gypsum into the water based mud.Basically, the viscosity, pH value, density, yield point and the mud weight is increasing as theamount of gypsum is increase while for plastic viscosity; the value is decreasing as the gypsumis increase.

2.0 INTRODUCTION

The drilling fluid system, commonly known as the mud system is the single component

of the well-construction process that remains in contact with the wellbore throughout the entire

drilling operation. Drilling fluid systems are designed and formulated to perform efficiently under

expected wellbore conditions. Advances in drilling fluid technology have made it possible to

implement a cost-effective, fit for purpose system for each interval in the well-construction

process.

Drilling fluid can be divided by three types which are freshwater systems, saltwatersystems, oil- or synthetic-based systems pneumatic (air, mist, foam, gas) fluid systems. The

functions of drilling fluid in drilling operation are to clean the hole by transporting drilled cuttings

to the surface, where they can be mechanically removed from the fluid before it is recirculated

down hole, to balance or overcome formation pressures in the wellbore to minimize the risk of

well-control issues and to support and stabilize the walls of the wellbore until casing can be set

and cemented or open hole-completion equipment can be installed. Besides, drilling fluid also

act to prevent or minimize damage to the producing formations, cool and lubricate the drill string

and bit, transmits hydraulic horsepower to the bit and allow information about the producingformations to be retrieved through cuttings analysis, logging-while-drilling data, and wire line

logs.


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Amud is said to be contaminated when a foreign material enters themud system and

causes undesirable changes in mud properties, such as density, viscosity, and filtration.

Generally,water-based mud systems are the most susceptible to contamination. Mud

contamination can result from overtreatment of the mud system with additives or from material

entering the mud during drilling.

The most common contaminants to water-based mud systems are solids which are

being added, drilled, active or inert, gypsum or anhydrite, cement or lime, makeup water,

soluble bicarbonates and carbonates, soluble sulfides and salt or salt water flow.

The calcium ion is a major contaminant to freshwater-based sodium-clay treated mud

systems. The calcium ion tends to replace the sodium ions on the clay surface through a base

exchange, thus causing undesirable changes in mud properties such as rheology and filtration.

It also causes added thinners to the mud system to become ineffective. The treatment depends

on the source of the calcium ion. For example, sodium carbonate (soda ash) is used if the

source is gypsum or anhydrite. Sodium bicarbonate is the preferred treatment if the calcium ion

is from lime or cement. If treatment becomes economically unacceptable, break over to a mud

system, such as gypsum mud or lime mud, that can tolerate the contaminant.

One of the sources of calcium is gypsum. In this experiment, gypsum is used as

contaminator that mixes with water based-mud. Gypsum is ground Calcium Sulfate Dihydrate. It

is typically act as an inexpensive source of calcium and alkalinity in gyp-based drilling muds. It

can raised the pH level. Its solubility will increased at higher chloride levels. In water-based

systems, it can treated trona water and CO2 contamination. Gypsum is a very softsulfate

mineral composed ofcalcium sulfatedihydrate,with thechemical formula CaSO42H2O. It can

be used as afertilizer,is the main constituent in many forms ofplaster and is widely mined. A

very fine-grained white or lightly tinted variety of gypsum, calledalabaster, has been used for

sculpture.

3.0 OBJECTIVES

This experiment is to study the effect of contamination of Gypsum (CaSO4- 2H2O) to to the

density, Plastic Viscosity (p) and Yield Point (Yp) of water based mud.
http://petrowiki.spe.org/Drilling_fluidshttp://petrowiki.spe.org/Drilling_fluid_typeshttp://petrowiki.spe.org/Drilling_fluid_types#Water-based_fluidshttp://en.wikipedia.org/wiki/Sulfate_mineralhttp://en.wikipedia.org/wiki/Sulfate_mineralhttp://en.wikipedia.org/wiki/Calcium_sulfatehttp://en.wikipedia.org/wiki/Dihydratehttp://en.wikipedia.org/wiki/Chemical_formulahttp://en.wikipedia.org/wiki/Fertilizerhttp://en.wikipedia.org/wiki/Plasterhttp://en.wikipedia.org/wiki/Alabasterhttp://en.wikipedia.org/wiki/Sculpturehttp://en.wikipedia.org/wiki/Sculpturehttp://en.wikipedia.org/wiki/Alabasterhttp://en.wikipedia.org/wiki/Plasterhttp://en.wikipedia.org/wiki/Fertilizerhttp://en.wikipedia.org/wiki/Chemical_formulahttp://en.wikipedia.org/wiki/Dihydratehttp://en.wikipedia.org/wiki/Calcium_sulfatehttp://en.wikipedia.org/wiki/Sulfate_mineralhttp://en.wikipedia.org/wiki/Sulfate_mineralhttp://petrowiki.spe.org/Drilling_fluid_types#Water-based_fluidshttp://petrowiki.spe.org/Drilling_fluid_typeshttp://petrowiki.spe.org/Drilling_fluids


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4.0 THEORY

Gypsum occurs in nature as flattened and oftentwinnedcrystals, and transparent,

cleavable masses calledselenite. Selenite contains no significant selenium. Gypsum is a

common mineral, with thick and extensiveevaporite beds in association withsedimentary rocks.

Gypsum is used in gypsum or lignosulfonate or polymer muds as a source of calcium ions for

inhibition and to convert bentonite to the calcium ion form. This avoids problems that might

otherwise occurs when anhydrite ids drilled. It can also be used as an economical treatment for

carbonate contamination in high pH muds with reaction:

CaSO4+ CO32-CaCO3+ SO4

2-

Gypsum is deposited from lake and sea water, as well as in hot springs,

fromvolcanic vapors, and sulfate solutions inveins.Hydrothermalanhydrite in veins is

commonly hydrated to gypsum by groundwater in near-surface exposures. It is often associated

with the mineralshalite andsulfur. Pure gypsum is white, but other substances found as

impurities may give a wide range of colours to local deposits. Because gypsum dissolves over

time in water, gypsum is rarely found in the form of sand.

In order to conducted the experiment, the properties that be measured surely known

in term of theory which means, what the relation between the properties and the mud. Yield

Point (yp) is one of parameters that be measured. Basically, it is resistance of initial flow of fluid

or the stress required in order to move the fluid. The parameter usually referred to the ability of

drilling mud where act as to carry cuttings to surface. Plastic Viscosity (PV) is referred to the

resistance of fluid to flow. It can be measured by using viscometer. The unit of PV is Centi-

Poise (CP) while for Yp is lb/100 ft2.

Plastic Viscosity (PV) = viscosity at 600 rpmviscosity at 300 rpm

Yield Point (Yp) = viscosity at 300 rpmPV

Apparent Viscosity = Viscosity at 600 rpm /2
http://en.wikipedia.org/wiki/Crystal_twinninghttp://en.wikipedia.org/wiki/Crystalhttp://en.wikipedia.org/wiki/Selenite_(mineral)http://en.wikipedia.org/wiki/Seleniumhttp://en.wikipedia.org/wiki/Evaporitehttp://en.wikipedia.org/wiki/Sedimentary_rockhttp://en.wikipedia.org/wiki/Hot_springhttp://en.wikipedia.org/wiki/Volcanohttp://en.wikipedia.org/wiki/Vein_(geology)http://en.wikipedia.org/wiki/Hydrothermalhttp://en.wikipedia.org/wiki/Anhydritehttp://en.wikipedia.org/wiki/Halitehttp://en.wikipedia.org/wiki/Sulfurhttp://en.wikipedia.org/wiki/Sulfurhttp://en.wikipedia.org/wiki/Halitehttp://en.wikipedia.org/wiki/Anhydritehttp://en.wikipedia.org/wiki/Hydrothermalhttp://en.wikipedia.org/wiki/Vein_(geology)http://en.wikipedia.org/wiki/Volcanohttp://en.wikipedia.org/wiki/Hot_springhttp://en.wikipedia.org/wiki/Sedimentary_rockhttp://en.wikipedia.org/wiki/Evaporitehttp://en.wikipedia.org/wiki/Seleniumhttp://en.wikipedia.org/wiki/Selenite_(mineral)http://en.wikipedia.org/wiki/Crystalhttp://en.wikipedia.org/wiki/Crystal_twinning


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5.0 APPARATUS

To test for density

1) Lid and Cup 4) Rider

2) Level bubble 5) Counterweight

3) Graduated arm

Figure 5.1 Mud Balance

To test for pH value

Figure 5.2 pH meter


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To test for viscosity

1) Motor 5) Propeller

2) Gearhead 6) Transformer

3) Shaft coupling 7) Power supply

4) Extension rod

Figure 5.3 Viscometer

Material

1) Water Based Mud

2) Gypsum


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6.0 PROCEDURE

For viscometer

1. The power supply is first switched on then the mud sample is filled into the mud cup.

2. The thermocouple is plugged in.

3. The bob is screwed into the bob shaft until it is tight.

4. The sleeve is tightening onto the rotor shaft.

5. The mud sample is placed on the stage by positioning the alignment stem over the

corresponding hole on the stage.

For unit measurement

i. Go button- After enter the test step, Press 1.

ii. Set up button- Press 2 will display the test set up screen, enter the parameter for

the temperature and rotational speed for the first step of the test. Enter twice to

return to main screen.

iii. Review button- After running the test, press 3 to allow to allow review the test

result.

6. The speed of the viscometer is set to 300 rpm and the data is recorded. Step 1-6 is

repeated using 600 rpm.

Experimental procedure

1. A 400 ml water based mud is measured in a beaker.

2. The mud is test for weight, plastic viscosity and yield point using viscometer. The

data is recorded in the table.

3. The water based mud is then divided separately into two different beakers with 200

ml in each beaker.

4. Then, the beaker is labeled as Beaker A and Beaker B.

5. Five grams of gypsum is added for Beaker A and 15 grams for Beaker B.


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6. The sample is stirred for three minutes using mixer.

7. The sample is being rest for 15 minutes.

8. Step 2 is repeated for both Beaker A and Beaker B.

9. Another five grams of gypsum is added in both Beaker A and Beaker B.

10. Step 6-8 is repeated and the data is recorded.

7.0 RESULT

INITIAL

WATERBESED MUD

WATER BASED MUD + GYPSUM

5g 10g 15g 20g

MUD

WEIGHT

(ppg)

10.6 8.5 8.7 9.1 9.0

PLASTIC

VISCOSITY

(p)

8.33 23 18 18 18

YIELD POINT

(YP) 21. 835 18.5 27 28 29

DENSITY

(sp.gr) 1.28 1.02 1.05 1.07 1.08

pH 7.23 7.17 7.51 7.60 7.63

APPARENT

VISCOSITY

(a)

17.17 26.50 27.00 27.50 28.00

300 26.00 30.00 36.00 37.00 38.00

600 34.33 53.00 54.00 55.00 56.00


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Graph 7.1 shows a graph of density against the amount of gypsum.

Graph 7.2 shows a graph of plastic viscosity against the amount of gypsum.

0

0.2

0.4

0.6

0.8

1

1.2

1.4

0 5 10 15 20

density (sp gravity)

The amount of gypsum (g)

The graph of density versus amount of gypsum

0

5

10

15

20

25

0 5 10 15 20

plastic viscosity (p)


The graph of plastic viscosity versus amount of

gypsum


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Graph 7.3 shows a graph of yield point against the amount of gypsum.

8.0 SAMPLE CALCULATION

Apparent viscosity = 600 rpm reading 2

= 34.33 cp 2

= 17.165 cp

Plastic viscosity = 600 rpm reading300 rpm reading

= 34.33 cp26.00 cp

= 8.33 cp

Yield point = 300 rpm readingplastic viscosity

= 26 cp(8.33x0.5) cp

=21.835 lb/100 ft2

0

5

10

15

20

2530

35

0 5 10 15 20

yield point (Yp)


The graph of yield point versus amount of

gypsum


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9.0 DISCUSSION

A mud is said to be contaminated when other materials enters the mud system and

causes undesirable changes in mud properties such as to the density, Plastic Viscosity (p) and

Yield Point (Yp) of water based mud. Comparing between water based mud and oil based mud,

water based mud systems are the most susceptible to contamination of various types. Mud

contamination can result from overtreatment of the mud system with additives or from material

entering the mud during drilling. Based on this experiment, it can be resolved that the objective

of this experiment which is to study the effect of contamination of Gypsum (CaSO 42H2O) to

density, Plastic Viscosity and Yield Point of water-based mud has been achieved. From the

experiment, it can be stated that density, Plastic Viscosity (p) and Yield Point (Yp) of the mud

can be influenced by the gypsum.

The experiment is run by using 5g, 10g, 15 g and 20 g of gypsum which are added as

contamination into the water based mud. The mud balance is used to measure the mud density.

Density of the mud is taken before added with gypsum. Gypsum is substances that have solid

properties. Some expectation has been made that the density of the drilling mud will increase

when the amount of gypsum was added to the drilling mud where the solid contents increased.

Based on the graph 7.1, density versus the number of gypsum, it showed that it is almost same

as theory which states that the density will increase as the amount of gypsum is higher. This is

because as the number of gypsum is increase 5g for each experiment, the weight must be

increase as well and same goes to the density which is the unit is in specific gravity. In

cementing, normally chemical additives are usually used to decrease the density when the

density is too high which then can cause the formation to break at lower pressure zones. The

results also proved the theory by which increased in solid contents will then increase the mud

properties.

The pH of the mud slightly increases as the amount of gypsum was added. As the

contamination in the mud is higher, the pH value must be more to be alkaline. In this

experiment, it has been proven that statement and it is also related to the theory. A 20g of

gypsum +water based mud has more alkalinity which is 7.63 compared to the others runs.

For apparent viscosity which is 300rpm and 600rpm, both readings show an increasing

when the amount of gypsum is increase too. Viscosity is a measure of a fluid resistance to flow.

It describes the internal friction of a moving fluid. A fluid with large viscosity resists motion

because its molecular makeup gives it a lot of internal friction and vice versa. In this experiment,


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both reading even in different rpm, shows that the mud is hard to move and have a lot of internal

friction when there is contamination in it. With that, the mud is more viscous as the gypsum is

added and it actually a treatment to the mud to make it more alkaline and make it more

effective.

For graph 7.2, which is the graph of plastic viscosity versus the amount of gypsum in the

mud, the value of the plastic viscosity itself can be determine by using a calculation in the theory

part. According to the theory, as the amount of gypsum is increase, plastic viscosity should be

decreasing. In this experiment, the value of plastic viscosity is decrease and keeps constant for

10g, 15g and 20g. This is probably due to the error during taking the viscosity of the mud using

a viscometer. The value doesnt keep constant yet the reading already been taken. With that,

there is an error in the result.

For graph 7.3, which is the graph of yield point versus the amount of gypsum, it tells that

after adding some amount of gypsum, the graph increasing. Before the gypsum was added, the

mud is higher point which is 21.84 lb./100ft2. Yield point is actually a resistance of initial flow of

fluid or the stress required in order to move the fluid. Theoretically, after adding a calcium ion,

the value of yield point should be increasing and it is proven in this experiment. The yield point

value can be calculated from the formula that is stated in the theory part.

10.0 CONCLUSION

The objective of this experiment was to study the effect of contamination of Gypsum

(CaSO42H2O) to the density, Plastic Viscosity (p) and Yield Point (Yp) of water based mud.

From the result obtained, it can be shown that all the data were recorded in the table and the

necessary graph were plotted. In this experiment, there is some error and mistake that affect the

result and make the reading not totally accurate. However, as expected, the density of drilling

fluid increased as the amount of Gypsum added increase because the increased in solid

contents will then increase the mud properties. For PV, it is decreases and the constant when

the amount of Gypsum increased. For yield point, it is increasing when amount of gypsum

increases. Therefore, the objective is achieved.


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11.0 RECOMMENDATIONS

1. Wear a fully PPE when conducting the experiment as it can be harmful to the students.

2. The amount of gypsum must be weight accurately in order to prevent an error happen

during taking the data of the experiment.

3. The water based mud must be filter first before conducting the experiment as to filter the

impurities. This is to prevent the data for measuring the mud weight, the viscosity and

others.

4. The mud must only contain gypsum as if other contaminant is involved in this

experiment, the result will be not consistent.

5. During run the viscometer, make sure the time taken for each sample of mud is

consistent as the longer the viscometer rotate, the viscosity of the mud will be higher

thus, it will affect the reading.

12.0 REFERENCES

http://petrowiki.spe.org/Drilling_fluids

http://petrowiki.spe.org/Mud_contamination

http://www.drillingahead.com/profiles/blogs/yield-point-yp

http://www.slb.com/~/media/Files/miswaco/product_sheets/gypsum.ashx

http://www.princeton.edu/~gasdyn/Research/T-C_Research_Folder/Viscosity_def.html
http://petrowiki.spe.org/Drilling_fluidshttp://petrowiki.spe.org/Drilling_fluidshttp://petrowiki.spe.org/Mud_contaminationhttp://petrowiki.spe.org/Mud_contaminationhttp://www.drillingahead.com/profiles/blogs/yield-point-yphttp://www.drillingahead.com/profiles/blogs/yield-point-yphttp://www.slb.com/~/media/Files/miswaco/product_sheets/gypsum.ashxhttp://www.slb.com/~/media/Files/miswaco/product_sheets/gypsum.ashxhttp://www.princeton.edu/~gasdyn/Research/T-C_Research_Folder/Viscosity_def.htmlhttp://www.princeton.edu/~gasdyn/Research/T-C_Research_Folder/Viscosity_def.htmlhttp://www.princeton.edu/~gasdyn/Research/T-C_Research_Folder/Viscosity_def.htmlhttp://www.slb.com/~/media/Files/miswaco/product_sheets/gypsum.ashxhttp://www.drillingahead.com/profiles/blogs/yield-point-yphttp://petrowiki.spe.org/Mud_contaminationhttp://petrowiki.spe.org/Drilling_fluids


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13.0 APPENDICES

Viscometer Mud balance

Mixer pH meter

Documents

drilling fluid contamination test