LAB 4 GEO

UNIVERSITI TEKNOLOGI MARAFAKULTI KEJURUTERAAN KIMIAGEOLOGY AND DRILLING LABORATORY(CGE 558)NAME : MUHAMMAD AIZUDDIN B ZAINAL ABIDIN SHAHSTUDENT NO : 2014489078EXPERIMENT : DRILLING FLUID CONTAMINATION TESTDATE PERFORMED : 17/3/2015SEMESTER : 03PROGRAMME/ CODE : EH 243/3GROUP : 2 No.TitleAllocated marks %Marks

1Abstract / summary5

2Introduction5

3Aims / objectives5

4Theory5

5Apparatus5

6Procedures10

7Results10

8Calculations10

9Discussion20

10Conclusions10

11Recommendations5

12References5

13Appendix5

TOTAL100

Remarks:

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TABLE OF CONTENTS :

NOTOPICSPAGES

1Abstract3

2Introduction4

3Objectives5

4Theory5

5Apparatus6

6Procedures7

7Results8

8Sample calculations10

9Discussion12

10Conclusions13

11Recommendations14

12References14

13Appendix15

ABSTRACTThe main purpose of this experiment is to determine the effect of contamination of Gypsum(CaSO4 2H2O) to the density, pH changes, Plastic Viscosity (PV) and Yield Point (Yp) of water based mud. Gypsum is one of the contaminate that may affect drilling fluid properties. The experiment started by preparing 200ml based mud in a drilling mud container and the drilling fluid initially tested for weight, pH value, PV and Yp by using viscometer and mud balance. After the values recorded, 5 grams of Gypsum were added in the container that contains water based mud. The mud containing Gypsum was stirred for 3 minutes. The values of viscosity, PV, Yp, density and pH value were recorded. The experiment was repeated by adding 10, 15 and 20 grams of Gypsum into the water based mud. Eventhough the results that we obtained is slightly different from theoritical value, the result in experiment shows that the value of density, PV, Yp changed when different amount of Gypsum was added into the water based mud. As the conclusion, based on theory, the higher the amount of gypsum added, the higher the Yp and Pv values.

INTRODUCTIONDrilling mud, also called drilling fluid, in petroleum engineering, a heavy, viscous fluid mixture that is used in oil and gas drilling operations to carry rock cuttings to the surface and also to lubricate and cool the drill bit. The drilling mud, by hydrostatic pressure, also helps prevent the collapse of unstable strata into the borehole and the intrusion of water from water-bearing strata that may be encountered. Drilling muds are traditionally based on water, either fresh water, seawater, naturally occurring brines, or prepared brines. Many muds are oil-based, using direct products of petroleum refining such as diesel oil or mineral oil.A most basic water-based mud system begins with water, then clays and other chemicals are incorporated into the water to create a homogenous blend resembling something between chocolate milk and a malt (depending on viscosity). The clay (called "shale" in its rock form) is usually a combination of native clays that are suspended in the fluid while drilling, or specific types of clay that are processed and sold as additives for the WBM system. The most common of these is bentonite, frequently referred to in the oilfield as "gel". Gel likely makes reference to the fact that while the fluid is being pumped, it can be very thin and free-flowing (like chocolate milk), though when pumping is stopped, the static fluid builds a "gel" structure that resists flow. When an adequate pumping force is applied to "break the gel", flow resumes and the fluid returns to its previously free-flowing state. Many other chemicals (e.g. potassium formate) are added to a WBM system to achieve various effects, including: viscosity control, shale stability, enhance drilling rate of penetration, cooling and lubricating of equipment.A mud is said to be contaminated when a foreign material enters the mud 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.Gypsum is used as contaminator that mixes with water based-mud which are soluble and can flocculate colloidal clays in the experiment. The calcium ion tends to replace the sodium ions on the clay surface through a base exchange, thus causing changes in mud properties such as rheology and filtration. It can raised the pH level. Its solubility will increased at higher chloride levels. It also causes added thinners to the mud system to become ineffective.

OBJECTIVESThis experiment was conducted to study the effect of contamination of Gypsum (CaSO4 2H2O) to the density, Plastic Viscosity and Yield Point of water-based mud.

THEORYGypsum occurs in nature as flattened and often twinned crystals, and transparent, cleavable masses called selenite. Selenite contains no significant selenium. Gypsum is a common mineral, with thick and extensive evaporite beds in association with sedimentary 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 + SO42-Gypsum is deposited from lake and sea water, as well as in hot springs, from volcanic vapors, and sulfate solutions in veins. Hydrothermal anhydrite in veins is commonly hydrated to gypsum by groundwater in near-surface exposures. It is often associated with the minerals halite and sulfur. 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

APPARATUSSteel cup, Viscometer, Mud balance, Hamilton beach mixer, Measuring cylinder, Stirrer, Stopwatch, pH meter, Gypsum, Water base mudMud BalanceMud Beach Mixer

Viscometer

PROCEDURE1. 200 ml of water base mud was measured and put in the beaker2. The weight, plastic viscometer and yield point were determined and recorded using the viscometer3. The water base mud was then contaminated with 5 g of gypsum4. The sample was then stirred for 3 minutes and aged for 15 minutes. Then it was stirred again for 3 minutes.5. The value of viscosity, yield point, density and pH of the contaminated gypsum were determined using pH meter and the viscometer.6. Another 200 ml of sample was prepared again.7. The steps were then repeated but using different weight of gypsum which was 10, 15 and 20 grams of gypsum.8. The data was then recorded and the graph of density, PV and Yp versus amount of gypsum were plotted.

RESULTTypes of Mud : Water Based Mud

Initial water base mudWater based mud + gypsum

5 g10 g15 g20 g

Mud weight (ppg)8.2 ppg8.8 ppg8.85 ppg9.1 ppg9.1 ppg

Density (SG)1.12 SG1.02 SG1.05 SG1.07 SG1.08 SG

pH7.237.177.517.607.63

351.0 CP 50.0 CP48.0CP36.0 CP33.0 CP

30084.8 CP60.2 CP59.4 CP46.9 CP43.5 CP

600119.0 CP71.0 CP72.0 CP58.0 CP54.0 CP

Apparent Viscosity (a)59.5 CP35.5 CP36.0 CP29.0 CP27.0 CP

Plastic Viscosity ( 600 - 3) (p)68.0 CP21.0 CP24.0 CP22.0 CP21.0 CP

Yield Point ( 3- p(0.5)) (yp)17.0 CP39.5 CP36.0 CP25.0 CP22.5 CP

Plastic Viscosity ( 600 - 300) (p)34.2 CP10.8 CP12.1 CP11.1 CP10.5 CP

Yield Point ( 300- p(0.5)) (yp)79.4 CP54.8 CP53.9 CP41.4 CP38.2 CP

Figure 1: Relationship between density and amount of gypsum

Figure 2: Relationship between plastic viscosity and amount of gypsum

Figure 3: Relationship between yield point and amount of gypsum

SAMPLE CALCULATION

At 20 g water based mud + gypsum Apparent viscosity= = = 27 cP

Plastic viscosity= 600 rpm reading 300 rpm reading = 54 cp 43.5 cP =10.5 cP

Yield point= 300 rpm reading plastic viscosity(0.5 N/m2)= 43.5 cP 10.5(0.5) = 38.2 lb/100 ft2

DISCUSSIONA mud is said to be contaminated when a foreign substance enters the mud 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 calcium ion such as from source of gypsum 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. It also causes added thinners to the mud system to become ineffective. The treatment depends on the source of the calcium ion.The experiment was conducted by adding 5g, 10g, 15 g and 20 g of gypsum as contaminant into the water based mud. The mud density is measured using mud balance. Density of the mud is taken before and after the mud was added with gypsum.Theoritically,the density of the mud will increase as the gypsum was added to the mud. Based on the Figure 1, this experiment proves that as the increasing of amount of gypsum added, the density of the mud will increase. The results proved that by increasing the solid contents will increase the mud density. The trend of the ph also is increasing as the gypsum is added to the water based drilling mud. This is because gypsum is alkaline in origin, thefore by adding gypsum inside the drilling mud it will increase the alcalanity of the water based mud thus making the ph higher than the normal ph of the mud that is close to the natural ph value.As for plastic viscosity and yield point there are some errors in our results because our results are bit drifted way from the expected values. Theoritically, as the amount of gypsum added to the mud is increased, the plastic viscosity will aslo increases because the addition of contaminant will increase the viscosity of the mud.Yield point and plastic viscosity is intercorrelated which mean their relationship is directly propotional because the calculation of yield point was based on plastic viscosity value. If the plastic viscosity increases the yield point will also increases. Nevertheless, our result is totally reverse from the expected theory. Based on Figure 2 and Figure 3, the trend of the results or the value of plastic viscosity and yield point is slightly increase at 10 gram amount of gypsum and follow by decreasing trend in the graph potrayed. This situation should not be happen because as amount of contaminants increase, the viscosity also should be increase as the calcium ion inside the gypsum mixed with the mud and causes some reactions and changes the resistivity of the mud to flow, but in our case it is the other way around and the result goes exaclty the same to the graph in Figure 3.The procedure are followed closely and there are no mistakes that we have done. Maybe due to the long waiting list to use the viscometer machine make a huge difference in our results. Long period of time maybe hasd affect and largely reduce the significant of of our result. The gypsum contained mud had been left for about 45 minutes before it went to viscometer machine.The mud maybe has settle down for way too long and the gypsum has lost it consistency and also settle at the bottom of the container,leaving the upper part nothing but the original mud itself. This might be the cause and machanisme that flipped our result in the first place.

CONCLUSIONThe objective of this experiment was to study the effect of contamination of Gypsum (CaSO4 2H2O) to the density, Plastic Viscosity (p) and Yield Point (Yp) of water based mud. Generally the addition of gypsum will affect the properties of the mud such as density, pH value, plastic viscosity, yield point and so on.The increment if the contaminers added will directly increase the value of the plastic viscosity of the drilling mud. Once the plastic viscosity (PV) increased the yield point (YP) will also increase because it depends on the amount of PV. Although clearly from our result the addition of gypsum decrease the YP and PV values but based on the theoritical result is opposite to the result obtained from the experiment.

RECOMMENDATION1. 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. Take the viscosity reading several times to obtain the average to ensure more accurate calculation.4. 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.5. Repair the other viscometer or replace the old unused viscometer with a new one to avoid any wasting of time while performing the experiments.

REFFERENCES1. Faculty of Chemical Engineering, Geology and Drilling Laboratory Manual2. http://petrowiki.spe.org/Drilling_fluids, Retrieved on 29th March 20153. http://petrowiki.spe.org/Mud_contamination , Retrieved on 29th March 20154. Ryen Caenn, H.C.H. Darley and George R. Gray, (2011), Composition and Properties of Drilling and Completion Fluids, Sixth Edition.

APPENDICES1