Manoj Das ONGC project

A project on

“SHRINKAGE IN CEMENTATION OF HIGH PRESSURE AND HIGH TEMPERATURE

WELLS”

Presented to the Institute of Drilling Technology (IDT)Oil and Natural Gas Corporation (ONGC), Dehradun

Winter Project Training Program

Under Guidance of:Dr. Kishori lal

Chief Chemist.Cementing R & D Department

Submitted by:

Manoj Das

B.tech(Petroleum Engineering)

LORDS INSTITUTE OF ENGINEERING AND TECHNOLOGY

HYDERABAD.

A Report on “SHRINKAGE IN CEMENTATION OF HIGH PRESSURE AND HIGH TEMPERATURE

WELLS”

As a part of Project Work, 3rd year of Petroleum Engineering. Session 2014-2015. Project work carried at IDT ONGC, Dehradun. Project mentor Dr. Kishori Lal, Chief Chemist, Cementing R & D Department.

Name : MANOJ DAS

Reg No: 12M21A2709

3rd Year

Petroleum Engineering

Lords Institute of Engineering & Technology.

Hyderabad - 500 008

Telangana.

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ACKNOWLEDGEMENT

This is my sincere attempt to condense the wealth of knowledge “SHRINKAGE IN CEMENTATION OF HIGH PRESSURE AND HIGH TEMPERATURE WELLS” at INSTITUTE OF DRILLING TECHNOLOGY, ONGC DEHRADUN, UTTARAKHAND.

I am immensely grateful to DR. RAVI RASTOGI, (DGM) for providing me such an opportunity to undergo this valuable project training.I am immensely indebted to my mentor DR. KISHORI LAL (Chief Chemist) whose guidance and expertise has helped me immensely during the tenure of my project.

I am also express my deep sense of gratitude to MR. B.S Chandal, MR. Madanlal, MR. Promod kumar, MR. H.S Negi, MR. R.P Baliwal for assisting me to perform the experimental work. I would like to thank MR. AK Saxxena and MR. Trilokchand for assisting me for the various instruments at drilling rig and their uses for drilling.

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PROJECT COMPLETION CERTIFICATE

This is to certify that the project entitled “SHRINKAGE IN CEMENTATION OF HIGH PRESSURE AND HIGH TEMPERATURE WELL” is an approved record of work done by MANOJ DAS(petroleum Engineering) of batch 2012-2016 from LORDS INSTITUTE OF ENGINEERING AND TECHNOLOGY, Hyderabad at IDT ONGC, DEHRADUN from 31-12-2012 to 31-1-2015 for the partial fulfillment of the requirements of the Project Work, 3rd year of Petroleum Engineering.

Date: 02/02/2015 Dr.KISHORI LALPlace: Dehradun Chief Chemist,

Cementing R & D Department, IDT ONGC, Dehradun.

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ABOUT ONGC

Oil and Natural Gas Corporation Limited (ONGC) is Indian multinational oil andGas Company headquartered in Dehradun, India. It is a public sector undertaking of the government of India’s under the administrative control of the Ministry of Petroleum and Natural Gas. It is India’s largest oil and gas exploration and production company. It produces around 69% of India’s crude oil and around 62% of its natural gas.

ONGC was founded on 14 August 1956 by Government of India, which currently holds a 69% equity stake. On 31 March 2013 its market capitalization was INR 2.6 trillion, making it countries second largest publicity traded company. It is involved in exploring for and exploiting hydrocarbons in 26 sedimentary basins of India and owns and operates over 11,000 km of pipelines in the country.

ONGC has discovered 6 of the 7 commercially producing Indian Basins in the last 50 years. ONGC has maintained production from its brown field’s like Mumbai High with the help of aggressive investments in various IOR and EOR schemes.In 2011 ONGC applied to purchase 2000 acres of land at Dahanu to process offshore gas.

ONGC went offshore in early 70’s and discovered a giant oil field in the form of Bombay high now known as Mumbai high this discovery along the subsequent discoveries of huge oil and gas fields in the western offshore change the scenario of the country subsequently, over 5billion tones of hydrocarbons, which were present in the country were discovered the most important contribution of ONGC however is its self-reliance and development of core competence in E&P activities at a globally competitive level.

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ABOUT IDT

The institute of drilling technology IDT was setup in 1978 at Dehradun is engaged in relentless efforts in R&D and has rendered excellent services in the area of oil gas well drilling technology. Over the years, the institute has emerged as a premier R&D center in south EAST ASIA capable of providing advance technical knowledge through training and offering plausible solution to field problems.

The institute with highly qualified and experienced scientists and engineers carry out applied research in all facets of drilling related activities to achieve technical excellence in R&D efforts and assimilation of emerging technologies.

The infrastructure for applied R&D has been developed with the state of the art equipment and machines to achieve qualitative experimental results. Focus of R&D is directed towards drilling technology drilling fluid engineering and cementation and cementing material to meet challenges of drilling industry.

IDT and QHSE certified institute have international accreditation from globally reputed agencies.

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ABSTRACTShrinkage is a worldwide problem arising in oil & gas well cement, this condition arises at the depth where there is a high pressure and high temperature conditions that is HTHP conditions. Shrinkage is a challenge for today’s oil field that some remedial measures are required for avoiding this shrinkage at high pressure and high temperature.

Characterization of cement bonding performance required the setup of new pieces of laboratory equipment. The evaluation of cement bonding property has pressure curing conditions, and was proved to be reproducible with a very small dispersion of results. Shear bond has been tested through mechanical and hydraulic means, and related to other parameters such Volumetric Shrinkage development, Stress-strain relationships, permeability, and compressive strength. A laboratory and field experiments program has been conducted to compare the bonding capability of standard cement compositions with that of modified with a bonding agent. Laboratory and field results are in perfect accordance.

Gas Migration represents 25% of the primary cement jobs failures. For this reason, studies have been done in order to evaluate several properties of cement slurry like fluid loss, Permeability, Static gel strength, and others. The Failure probability of casing collapse is high in HPHT wells because of the cementing complications and the operational environment. Due to the High pressure and High Temperature (HPHT) conditions, the cement sheath plays a more important role in maintaining well bore integrity.

Transition time or right angle sight of cement slurry should be low to avoid shrinkage of cement slurry in high pressure and high temperature wells.

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CONTENTS1. Introduction ………………………………………………………….. 9

2. Aim & Objective of Project ……………………………………. 10

3. Equipments and Materials Required …………………….. 11

4. About Cement ………………………………………………………. 11

5. Classification of Cement ……………………………………….. 12

6. Importance of Cementation …………………………………. 13

7. Functions of Cementing ……………………………………….. 14

8. Cementation Job ………………………………………………….. 14

9. Cement Additives …………………………………………………. 15

10. Slurry Design Parameters …………………………………….. 16

11. Different Instruments used in this experiment …….. 17

12. Experimental Work ………………………………………………. 22

By Stability Test ………………………………………….. 22

By Molds Methods ……………………………………. 49

13. Conclusion& Recommendation..………………………….. 58

14. Reference ………………………………………………………………. 59

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INTRODUCTIONGas Migration due to Shrinkage:

The condition for gas migration develop when the hydrostatic pressure of the hydrated cement slurry column slowly declines and finally fall below the pore pressure this is mainly cause due to chemical shrinkage.

A serious problem in well cementing is the failure of bond between the cement and the formation. Such failure may allow fluid and or gas movement from one zone to another.

Cement shrinkage is a very important factor, contribution both to gas migration and to interfacial bonds. The reduction of the absolute volume, which occurs when water and cement particles combine to form hydrates, is the phenomenon that causes this chemical shrinkage.

Also a poor bond may result in loss of produced materials, premature reservoir depletion, and unsatisfactory stimulation operations. A means of decreasing such problems is the introduction of expensive properties to the cement system and has been used for this purpose.

The purpose of this study compares the expansion properties of shrinkage- compensating cements with other cements. Other properties such as pumping time, compressive strength, and bonding of the cement systems were evaluated.

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AIM& OBJECTIVE OF THIS PROJECT

Completely focused on the problemsthat cause oil well cement to shrink at high temperature and pressure.To give some solutions to overcome from this burning problem being faced in oil wells.Comparison of various physical properties of slurries like fluid loss, compressive strength, on using other materials which may be responsible for shrinkage. Designing cement slurry with improved physical properties with indigenous sources.

The objective of this project is to provide a solution for shrinkage in oil well cement at high pressure and high temperature.

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EQIUPMENTS AND MATERIALS REQUIRED

• API class G cement ( Dig Vijay)

• CEMENT ADDITIVES:

• Silica flour

• Suspend HT

• Gas stop HT

• Haled -567

• Comp

• Component R

• CFR-3

• HTHP curing chamber

• Gas Migration Analyzer (GMA)

ABOUT CEMENT

Cement is typically a fine powder of alumina, silica, lime, iron oxide etc. These raw materials are extracted from the quarry crushed to a very fine powder and then blended in definite proportions.

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These blended raw materials is called the raw feed or kiln feed and is heated in rotary kiln where it reaches a temperature of about 1400 deg c to 1500 c. in its simplest form, the rotary kiln is a tube up to 2000M long and perhaps 6 meters

Diameter, with a long flame at one end and gradually passes down to the hot end. Then falls out of the kiln and cools down.It is a hydraulic blinder it hardens when water is added. Thus, they can harden underwater or when constantly exposed to wet weather.

PHYSICAL AND CHEMICAL PROPERTIES OF OIL WELL CEMENT

1. Particle size of oil well cement is finer than constructioncement.

2. Percentage of tri calcium aluminate is more.

3. Oil well cement is high sulphate resistant (HSR) than construction cement.

API CLASSIFICATION OF CEMENT

API has recommended six classification of oil well cement which are- A,B,C,D,G & H, these are further classified in to 3 categories of ordinary, moderate, and high sulphate resistant depending upon tri calcium sulphate amount.

CLASS A:Depth surface is 6000ft No special properties.Similarto ASTM C150, type1.

CLASS B:Depth surface 6000ft.Moderate to high Sulphate resistant.Similarto ASTM C 150

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CLASS C:Depth surface 6000ft.High early strength.Moderate to high sulphate resistant.Similar to ASTM C 150 type 3.

CLASS D: Depth 6000-10000ft.Moderate and high sulphate resistant.Moderately high pressure and cement.

CLASS G:Depth surface 8000ft as basic cement fine.Can be used with accelerators and retarders for other specifications.Moderate to high sulphate resistant.

CLASS H:Depth surface 8000ft as basic cement coarse.Can be used with accelerators and retarders.Moderate to high sulphate resistant.No addition other than calcium sulphate and water. No addition other than calcium sulphate and or water.

IMPORTANCE OF CEMENTATIONOil well cementation is the process of mixing and displacing the slurry down the casing and up the annulus behind the casing, where it is allowed to set thus bonding the casing to the formation.TYPES OF CEMENTINGPROCESSES:PRIMARY CEMENTING.SQUEEZE CEMENTING.PLUGGING.

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SPECIAL TECHNIQUES.

FUNCTIONS OF CEMENTING

1. Protecting producing formations.2. Providing support for thecasing.3. Protecting the casing from corrosion.4. Stop the movement of fluid into vugular or fractured formations.5. Close an abandoned well or a portion of a wellSidetracking.6. Sealing of troublesomezones.7. Protecting the borehole in the events of problems.

CEMENTATION JOB

Cementing is performed when the slurry is deployed into the well via pumps, displacing the drilling fluidand replacing them with cement. The cement slurry flows into the bottom of the well bore through the casing and from there it fills in the space between the casing and actual wellbore and hardens. This creates a seal so that outside material cannot enter the well flow as well as permanently positions the casing in place.

Most commonly cementing is used to permanently shut off water penetration into the well. Part of completion process of a prospective production well, cementing can be used to seal the annulus after a casing string has been run in the wellbore.

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Additionally cementing is used to seal a loss circulation zone.In directional drilling cementing is used to plug an existing well in order to run a directional well from that point.

CEMENT ADDITIVESAt present more than 40 different types of additives are used with various API class of cement to provide optimum slurry characteristics for any downhole condition.

Cement additives are classified as:• Accelerators.• Light-weight additives.• Heavy-weight additives.• Retarders.• Lost-circulation control agents.• Filtration control agents.• Friction reducers.• Special types of additives.

ACCELERATORS:In a low temperature formation, accelerators are used to minimize the thickening time ofadditives are used. These additives must have higher specific gravity, uniform size, must be chemically inert. The most commonly used is hematite.

RETARDERS:At high bottom hole static temperature cement sets very quickly and to prevent the cement from setting too quickly, retarders are used. Most retarders affect the viscosity to some deg, the governing factor for the use of retarders are temperature and pressure. Common types of retarders are lignin retarders, organic acids, borax etc.

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LOST CIRCULATION CONTOL AGENTSLost circulation is defined as the loss to induced fractures of either drilling mud or cement slurry used in drilling. Due to lost circulation the density of cement slurry decreases. So these additives are used to control the loss of cement slurry to the formation.Some examples are cellophane, walnut shells, coal, nylon etc.

FILTRATION CONTROL AGENTS:Filtration control additives are used to form films or micelles which control the flow of water from the cement slurry and prevent rapid dehydration. The most commonly used filtration control materials are cellulose and friction reducers.

FRICTION REDUCERS:These additives are used to cement slurries to improve their flow properties. Dispersed slurries have lower viscosity and can be pumped in turbulence at lower pressure, thereby minimizing the horsepower required to pump the slurry. Some examples are sodium chloride, polymers, calciumlignosulfonates etc.

SPECIAL ADDITIVES:These types of additives are used in cement slurry to perform some special functions. Examplesare mud decontaminants, silica flour which is used to prevent loss of strength, hydrazine which prevent from corrosion etc.

FACTORS THAT INFLUENCE CEMENT SLURRY DESIGN:

• Well depth.• Well temperature.• Mud column pressure.• Viscosity and water content of cement slurry.

• Pumping and thickening time.

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• Strength of cement slurry to support the pipe.• Quality of the mixing water.• Slurry density.• Heat of hydration.• Permeability of set cement.• Filtration control.

SLURRY DESIGN PARAMETERS• SPECIFIC GRAVITY.• FLUID LOSS /FILTRATION LOSS.• FREE WATER.• RHEOLOGICAL PARAMETERS.• COMPRESSIVE STRENGTH.• STABILITY.• GAS TIGHT PROPERTY (BY GMA).

DIFFERENT INSTRUMENTS USED IN THE EXPERIMENT

1.SLURRY MIXERWe use cement slurry mixer which is designed according to API specifications. It has a blade assembly which is within strict guidelines of the API specifications 10 and 10A methods of the evaluation of the oil well cement. This instrument is used to prepare oil well cement slurries, as close as possible to stimulating the appropriate shear encountered in the field.

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2. MUD BALANCE:

Mud balance provides simple practical method for the accurate determination of the fluid density. It is one of the most sensitive and accurate fieldinstrumentsavailable for determining the density or weight per unit volume of drilling fluids. An outstanding advantage of this mud balance is that the temperature of the sample does not materially affect the accuracy of reading.

3. ATMOSPHERIC CONSISTOMETER:

Atmospheric consistometer is specifically designed to condition the cement slurries for testing properties such as thickening time free water content viscosity rheological properties and fluid loss. The slurry is stirred at 150 rpm by an API designed paddle while the temperature is increased to desired level. The temperature is controlled by a micro-processor which displays the process temperature via a digital indicator.

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Consistency measured in bearden units is determined by measuring the deflection of calibrated spring. This

Deflection is created by the amount of torque the cement slurries exert upon the paddle and is a function of the consistency of the cement

4. RHEOMETER:

A Rheometer is a laboratory device to measure the way in which the liquid suspension or slurry flows in response to applied forces. It is used for those fluids which can’t be defined by single value of viscosity and therefore requires more parameters to be set and measured then in the case for a viscometer. It measures the rheology of the cement slurry at bottom hole and HPHT consistometer

5. HPHT CURING CHAMBER:

It is high temperature and high pressure curing chamber in which we put the cement slurry by putting it in to 2*2*2 cube or in cylindrical tube for 48 hours at a definite temperature and pressure. After curing its strength is checked by breaking it in the compressive strength tester.

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6. COMPRESSIVE STRENGTH TESTER:

It is a strength testing machine in which we find the strength of the cement block of 2*2, it is placed on the face of machine and load is put on it. On increasing load block breaks at a particular point at which the reading is noted down. The strength is measured in PSI

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7. GAS MIGRATION ANALYZER:

Gas migration analyzer are used to evaluate a cement slurry’ susceptibility to invasive gas or liquid flow by realistically simulating the well parameters including temperature, hydrostatic head pressure, fluid formation pressure and the pressure gradients that drive these invasive flows.

Gas Migration will result in the pore pressure of the sample rising and porosity becoming and/or remaining equal to the gas injection pressure. If no gas migration occurs, the pore pressure will continue to drop (due to the shrinkage and loss of fluid communication through the sample) during hydration, possibly continuing to reach a vacuum.

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EXPERIMENTAL WORKS

PREPARATION OF CEMENT SLURRY:

Weight dry materials and then blend thoroughly and uniformly prior to adding them to mixing fluid. Place the mixing container with the required mass of mix water and any liquid additives on the mixture base. Turn on the motor and maintain at 4000rpm/min. If the additives are present in the mix water stir at the above rotational speed to thoroughly disperse them prior to addition of cement.

In certain cases, the order of addition of the additives to the mixture water can be critical Document any special mixing procedures and mixing time. Add the cement or slurry dry additive blend at uniform rate. Some slurry designs make longer time to completely wet the cement blend, however the time used to blend the shall be kept at a minimum. When all the dry material have been added to the mix water, the place cover on mixing container and continue the rotational speed under load.

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EXPERIMENTAL WORK DONE TO KNOW ABOUT SHRINKAGE

Shrinkage is because of chemical reaction between cement and water that occurs during hydration process, as result of shrinkage hydrocarbons can migrate in to environments. Reaction between cement and water is exothermic process this cause the decrease in volume of cement slurry. It is due to HTHP and result of chemical reaction taking place in oil well.

EXPERIMENTAL METHOD TO FIND SHRINKAGE:

There are generally two experimental methods to find out the % of shrinkage in oil well cementation at HTHP wells:

1.BY CALCULATING VOLUME REDUCTION USING STABILITY TEST.

2. CURING MOULD AT DESIRED TEMPERATURE AND PRESSURE.

1. SHRINKAGE DETERMINATION BY STABILITY TEST:

In stability test we first make the cement slurry by taking the below mentioned additives in the table. We have checked the density of the slurry and it was found 1.94. Then we put the slurry in cylindrical tube whose volume is 102ml and kept it for 48 hours in the HTHP curing chamber by applying of temperature 1160 C and pressure 3000 psi. Chemical reaction took place between the cement, water and with other chemicals during the period of 48 hours. After 48 hours it observed that the volume of the cement slurry reduced from that of initial volume which was kept before 48 hours.

The amount of volume reduced within 48 hours is called shrinkage of cement slurry in oil well cementation. Shrinkage problem is mostly occurs in high temperature and high pressure wells. Due to high bottom hole temperature cement slurry losses its some crucial properties such as strength, thickening time and volume of slurry reduction etc. So to overcome from such problems we have to make the cement slurry according to such environments where it can be placed for a long time without losing its any physical and chemical properties.

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Following are the list of chemicals which are used to make the slurry.

Cement 100Water 44Sio2 33Suspend H.T 1.00H-447 0.8Gas stop H.T 0.4HR-12 0.6CFR-3 0.1D Air 4k 0.1

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Temperature = 1160c

Pressure = 3000 psi

Time = 48 hours

From above mentioned composition slurry was prepared by taking 600 gram of cement by weight and according to by weight of cement we took the remaining chemicals.

In stability test we first calculate the initial volume of the slurry which is to be placed in the curing chamber which was about

102 ml.

Starting time of the experiment was note down and the tube was ready to place in the HTHP curing chamber.

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After 48 hours we observed the above situation to the cement slurry which we called shrinkage of cement slurry. Due to which we clearly see that there is reduction of cement slurry volume in the cylindrical tube.

Due to high temperature rate of hydration was very high. Chemical reaction took place between the compositions of the slurry which were kept in the tube.

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CALCULATION:

Total height of the cylindrical tube = 21cm.

After 48 hours height of tube filled

With cement slurry= 19cm.

Radius of the tube= 1.25cm

From the above mentioned data

We can find the initial and final

Volume of the tube and from

That we can know the % of shrinkage

Initial volume v=πr 2 .h1

= 3.14×(1.25)2×21

= 102 ml.

Final volume v=πr 2.h2

= 93 ml

Volume reduced = 9ml

Shrinkage %= 9÷102×100

= 8.8%

DENSITYTEST:

To check the density we have broken the tube in two equal pieces and took the weight of particular pieces in air and in water respectively.

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Density = weight in air÷ weight in water.

Parts Weight in air Weight in water DensityTop 75.2 41.2 1.82Bottom 75.8 39.2 1.93

Bottom portion is more denser than the top portion.

Difference of density = 1.93-1.82 = 0.11

OBSERVATION:

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Initial volume Final volume

102 93

EXPERIMENT TO PREVENT THE SHRINKAGE:To prevent the shrinkage percentage now we are adding two cement additives latex and wallosonite to prevent from shrinkage at HTHP conditions.

CEMENT SLURRY WITH 10% LATEX:

In this experiment I am adding 10% latex to the cement slurry to minimize the shrinkage. Latex modified cement will create a film between a hydrated cement particles and this will prevent the fluid loss. Latex is generally used in high temperature and high pressure well.

Base slurry with 10% latex:

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Cement 100Water 44Sio2 33Suspend H.T 1.00H-447 0.8Gas stop H.T 0.4HR-12 0.6Latex 10CFR-3 0.1D air 4k 0.1

Temperature = 1160C

Pressure = 3000psi

Specific gravity = 1.80

After curing the slurry in HTHP curing chamber for 48 hours we have got the below mentioned changes.

Some changes occurred with the slurry after mixing the latex in the earlier slurry.

Shrinkage occurs but less than found in the earlier expt.

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Calculation:



With cement slurry = 20cm.

Radius of the tube = 1.25cm





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= 3.14×(1.25)2×21

= 102 ml.


= 3.14×(1.25)2×20

= 98 m

Volume reduction = 4ml.

Shrinkage %= 4÷102×100

= 3.9 %

DENSITY TEST:




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Bottom portion is having more density than the top portion.

Density difference = 1.84-1.74 = 0.10

OBSERVATION:


102 98

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BASE SLURRY WITH 10% WALLOSONITE:

Now the same slurry is treated with same amount of wallosonite instead of latex.

Cement 100Water 54Sio2 33Suspend H.T 1.00H-447 0.8Gas stop H.T 0.4HR-12 0.6Wallosonite 10CFR-3 0.1D air 4k 0.1

Temperature = 1160C

Pressure = 3000 psi


After curing the slurry in HTHP curing chamber for 48 hours we have got the below mentioned changes.

Some changes occurred with the slurry after mixing the latex in the earlier slurry.

Wallosonite reacts with the cement slurry and with other additives and able to minimize the shrinkage rate by some extent.

Experiment result is shown below after adding of wallosonite to the base slurry.

We can use wallosonite as a shrinkage control additive.

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Fig.slurry with 10% wallosonite.

CALCULATION:








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= 3.14×(1.25)2×21

= 102 ml.


= 3.14×(1.25)2×20

= 98 m

Volume reduction = 4 ml.

Shrinkage % = 4÷102×100

= 3.9%

DENSITY TEST:



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Density difference = 0.10

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OBSERVATION:


102ml 98 ml

RHEOLOGY OF THE SLURRY:


Temperature = 900C

@(rpm) UP DOWN3 20 126 26 1530 75 4560 100 78100 135 115200 210 195300 255 255

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Plastic viscosity (Pv) = 219

Yield Point = 45

K = 1.2

n = 0.65, Density = 1.90

Critical velocity (VC) = 13 ft/sec.

THICKENING TIME (T.T):


Temperature = 1160C

Pressure = 10000psi

Raising time = 40 minutes


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Thickening time observation table:

Time(min) Consistency(B.C) Temperature (0C) Pressure(psi)o.oo 20 21 50010 12 47 200020 12 70 500030 10 93 800040 6 116 1000050 6 116 1000060 6 116 1000070 4 116 10000150 4 116 10000278 30 116 10000283 70 116 10000286 100 116 10000

Thickening time of the above slurry = 286 minutes.

BASE SLURRY WITH 15% LATEX:


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In this experiment we increase the % of latex by 15% earlier which was 10% to see whether we can see any improvement in the slurry or not.

Temperature = 1520C

Pressure = 3000 psi


Fig. 15% latex added.

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CALCULATION SHRINKAGE:










= 3.14×(1.25)2×21

= 102 ml.


= 3.14×(1.25)2×20

= 98 ml

Volume reduction = 4ml.

Shrinkage % = 4÷102×100

= 3.9 %

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DENSITY TEST:




Density difference = 0.13.

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OBSERVATION:


102 98

BASE SLURRY WITH 15% WALLOSONITE:

In this experiment we have taken 15% wallosonite for better results.


Temperature = 1160C

Pressure = 3000 psi


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After curing the in HTHP curing chamber for 48 hours we came to the conclusion below described.

After adding 15% wallosonite to the slurry shrinkage found was almost negligible.

Wallosonite is able to prevent the slurry from shrinkage.

CALCULATION OF SHRINKAGE:



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With cement slurry = 20.7cm.







= 3.14×(1.25)2×21

= 102 ml.


= 3.14×(1.25)2×20.7

= 101.5 ml.

Volume reduction = 0.5ml

Shrinkage % = 0.5÷102.80×100

= 0.5 %

OBSERVATION:

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102ml 101.5 ml

DENSITY TEST:




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Density difference = 0.11

IMPORTANCE OF LATEX IN OIL WELL CEMENTATION:

Latex is the emulsion polymer which is generally very fine ball suspension emulsion polymer particle and the particle size is between 200-500 nm. Adding latex to the oil well cement slurry can increase the toughness of the set cement, restrain the cement hydration contraction, reduce the fatigue, improve the slurry and sidewall interface structure and realize the aim of anti-fluid channeling. It can also increase cement stone flexural strength, reduce the broken degree of perforation to cement ring. Latex can clog cement internal pore, fast become the membrane in the process of fluid loss.

Due to the complicated cement slurry ingredients, the high ions concentration, and the complex underground environment the mechanical stability and chemical stability of latex are demanded.

The application temperature is 30-1500C BHCT.

ABOUT WALLOSONITE:

Wollasonite is a calcium ion silicate mineral that contains small amount of iron, magnesium, and manganese substituting calcium.

It is generally white in color and forms when impure limestone or dolomite is subjected to high temperature and pressure sometimes in the presence of silica bearing fluids.

Wollasonite has low moisture content property, low oil absorption property, and low volatile content.

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CONCLUSION FROM STABILITY TEST:

SLURRY WITH LATEX

Slurry type Result

Neat slurry 8.8% shrinkage

Slurry with 10% latex 3.9% shrinkage

Slurry with 15% latex 3.9% shrinkage

SLURRY WITH WOLLASONITE:

Slurry type Result

Neat slurry 8.8% shrinkage

Slurry with 10% wollasonite 3.9% shrinkage

Slurry with 15% wollasonite 0.5% shrinkage

CONCLUSION:

Among latex and wollasonite, wollasonite is the best chemical to prevent from shrinkage in oil well cementation of high temperature and high pressure wells.

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SHRINKAGE DETERMINATION BY MOLDS METHOD:

In this method we put the cement slurry in 2/2 inch size cube and cured in HTHP curing chamber for 48 hours at 1520C and after 48 hours it becomes 2/2 size molds.

We observed if there is any change to the prepared molds dimension with compared to the dimension of the cube or not at 1520C for 48 hours.

EXPERIMENT NO. 1:

NEAT SLURRY:

Cement 100Water 44Sio2 33Suspend H.T 1.00H-447 0.8Gas stop H.T 0.4HR-12 0.6CFR-3 0.1D Air 4k 0.1

Temperature = 1520C

Pressure = 3000 psi


Time = 48 hours

We have prepared the slurry with above mentioned compositions and put it in to the cubes for 48 hours in the HTHP curing chamber.

After 48 hours we have got the below mentioned changes.

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RESULT: Initial dimension of the cube= length= 2 inch.

Breath= 2 inch.

Height= 2 inch.

After 48 hours length= 2 inch.

Breath= 2 inch.

Height= 1.8 inch.

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VOLUME CALCULATION:

Initial volume= 2×2×2

= 8 cubic inch.

Final volume= 2×2×1.8

= 7.2 cubic inch.

Volume decreased= 0.8 cubic inch.

SHRINKAGE % = 10%

COMPRESSIVE STRENGTH:

Mold 1= 7500 psi

Mold 2= 8000 psi

COMPRESSIVE STRENGTH OF THIS SLURRY:

= 1937 psi.

EXPERIMENT TO PREVENT THIS SHRINKAGE:

To prevent the above slurry from shrinkage we have added 15% latex and wollasonite to this slurry.

Latex and wollasonite having the property of hydration control and can maximize the strength of set cement.

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From the previous experiment we came to the conclusion that latex and wollasonite are two chemicals which can be used to prevent the shrinkage in oil well cementation at high temperature and high pressure wells.

EXPERIMENT NO. 2

SLURRY WITH 15% LATEX:


Temperature = 1520C

Pressure = 3000 psi


Time = 48 hours


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After 48 hours we did not got any changes in the dimension of the prepared mold to the dimension of the cube.

RESULT:

Initial dimension of the cube length= 2 inch.

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Breath= 2 inch.

Height= 2 inch.

After 48 hours length= 2 inch

Breath= 2 inch

Height= 2 inch

VOLUME CALCULATION:


= 8 cubic inch.

Final volume= 2×2×2

= 8cubic inch.

NO CHANGE IN VOLUME.

NO SHRINKAGE


Mold 1= 8000psi

Mold 2= 10250 psi


= 2281 psi.

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EXPERIMENT NO. 3

SLURRY WITH 15% WOLLASONITE:


Temperature = 1520C

Pressure = 3000 psi


Time = 48 hours


After 48 hours we did not got any changes in the dimension of the prepared mold to the dimension of the cube.

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RESULT:

Initial dimension of the cube length= 2 inch.

Breath= 2 inch.

Height= 2 inch.

After 48 hours length= 2 inch

Breath= 2 inch

Height= 2 inch

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VOLUME CALCULATION:


= 8 cubic inch.

Final volume= 2×2×2

= 8cubic inch.

NO CHANGE IN VOLUME.

NO SHRINKAGE


Mold 1= 9500psi

Mold 2= 8500 psi


= 2250 psi.

From molds method we have come to the conclusion that latex and wollasonite are two cement additives which can prevent oil well cement from shrinkage at high pressure and high temperature wells.

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CONCLUSION:

BASED ON THE EXPERIMENT PERFORMED AND RESULTS AS SHOWN ABOVE, FROM THAT WE HAVE COME TO THE CONCLUSION THAT

AT HIGH PRESSURE AND HIGH TEMPERATURE WELLS LATEX AND WOLLASONITE ARE THE ONLY TWO CEMENT ADDITIVES WHICH CAN AVOID THE CEMENT SLUURY FROM SHRINKAGE.

LATEX AND WOLLASONITE ALSO ABLE TO MAINTAIN OTHER SLURRY DESIGN PARAMETERS SUCH AS FLUID LOSS, COMPRESSIVE STRENGTH, RHEOLOGY AND GAS MIGRATIONFROM DISTURBANCES AT HIGH PRESSURE AND HIGH TEMPERATURE CONDITIONS.

RECOMMENDATION:

THE EXPERIMENTAL RESULTS CLEARLY SHOW THAT LATEX AND WOLLASONITE EXHIBIT THE SUPERIOR PARAMETERS THAT CAN BE USED IN OIL WELL CEMENT TO AVOID SHRINKAGE.

TRANSITION TIME OR RIGHT ANGLE SIGHT OF THE CEMENT SLURRY SHOULD BE LOW.

HYDRATION RATE SHOULD BE LESS.

SLURRY DESIGN SHOULD BE GOOD.

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BIBLIOGRAPHY/REFERANCES

1. Well Cementing, Edited by Erick B Nelson, Elsevier Science Publisher, B.VThe Netherlands.

2. Recommended Practices for Testing Well Cements. API Recommended Practice 10 B 2005

3. Standard Handbook of Petroleum and Gas Engineering, Vol-2, By William C.Lyons, Joseph Zaba

4. SPE-24978 Preventing Shallow gas migration in offshore well: The Performance of Lead Cements By OD. Coker et. Al.

5. SPE-160217; Reliable Completion System for Gas Migration Prevention By CharlesW.Pleasants,et al.

6. SPE-14500 New Quick-Setting Cement solves Shallow Gas Migration Problems and Reduces WOC Times By D.J Sepos and B.W Cart.

7. IADC/SPE 47775 Prevention of Shallow Gas Migration through Cement. By Khalid Al-Buraik,et at.

8. SPE 97168, New API Practices for Isolating Potential flow Zones during Drilling.

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THE END

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