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DEFORMATION AND ACOUSTIC BEHAVIOR OF OIL WELL

CEMENTS

by

William Yi Guo, B.S. in Petroleum Engineering

Thesis

Presented to the Faculty of the Graduate School of

The University of Texas at Austin

in Partial Fulfillment

of the Requirements

for the Degree of

Master of Science in Engineering

The University of Texas at Austin

May 2006


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DEFORMATION AND ACOUSTIC BEHAVIOR OF OIL WELLCEMENTS

Approved bySupervising Committee:


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ACKNOWLEDGEMENTS

The author wishes to express his appreciation to Dr. K.E. Gray, who initiated the

Life-of-Well Rock, Fluid, and Stress Systems project. Dr. Grays guidance and assistance

during the completion of this work have been of great value.

The author also wishes to thank Dr. Jon Holder for his help. Dr. Holder has

provided valuable data analysis methods and suggestions towards success of this project.

Special thanks are due to Mr. Charles Stephenson, the lab technician who carried

out all experimental work.

Grateful acknowledgement is made to Craig Gardner, Chevron; Dan Mueller, BJ

Services; and Glenn Benge, Exxon-Mobile for financial support of this work through the

Life-of Well Program.

William Yi Guo


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ABSTRACT

DEFORMATION AND ACOUSTIC BEHAVIOR OF OIL WELL

CEMENTS

William Yi Guo, M.S. Engineering

The University of Texas at Austin, 2006

Supervisor: Kenneth E. Gray

The experiments described in this thesis were designed to assess the evolution of

deformation and acoustic behavior of cement slurry as it hardens. Laboratory facilities

and test procedures developed over four decades in the University of Texas Rock

Mechanics Laboratory were used to characterize static and dynamic deformation, failure,

and inelastic behavior of two cement mixtures as they cured from freshly-mixed slurry to

intact material.

The experiments provide documentation of material behavior during curing in a

carefully controlled environment, to develop a better understanding of physical and

chemical processes that are active during curing. The database of mechanical properties

will provide useful inputs into numerical modeling of well-bore casing behavior. It is

anticipated that the shakedown measurements in this project will form the basis for the

design of more elaborate studies of cement-casing behavior in cemented casings.


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Two cement recipes were used. Slurry mixtures for each of the specimens were

placed immediately after mixing into the testing system. Length changes and

compressional wave velocities were measured during an initial 24-hour curing and during

several tri-axial deformational cycles carried out at 24-48 hour intervals, over a one-

week-long-term curing period. Eight specimens of Mix #1 cement and seven specimens

of Mix #2 cement were tested. Specimens were cured under ambient, 200 psi, and 1 kpsi

confining pressure. Several of the tests were repeated to assess measurement

reproducibility. Excess water layer was removed from the top of some of the poured

specimens as it was produced, for approximately 30 minutes prior to the application of

confining pressure, to assess the effects of initial water content on mechanical behavior.

Experiments were carried out to determine the degree of cement stiffness and

Non-Recoverable Strain (NRS) using static deformation and ultrasonic pulses through the

cement slurry during hardening. Data were used to determine P-wave velocity, NRS,

Youngs modulus, and static and dynamic modulus.

Axial stress vs. axial strain and total axial stress axial strains vs. elapsed time

were plotted for each test sample. P-wave velocity, Youngs modulus, and static and

dynamic constrained modulus were plotted versus elapsed time for both mix #1 and #2

(H2O wicked and not wicked). Results show that P-wave velocity increased non-linearly

with elapsed time; Youngs modulus increased with each succeeding stress-strain

unloading cycle, and static and dynamic constrained modulus both increased non-linearly

with elapsed time.


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Table of Contents

Acknowledgements .............................................................................................. iii

Abstract ................................................................................................................ iv

List of Tables ..................................................................................................... viii

List of Figures ...................................................................................................... ix

List of Illustrations .............................................................................................. xii

Nomenclature....................................................................................................... xiii

Chapter 1 Introduction ........................................................................................1

Literature Review ..........................................................................................1

Problem Statement ........................................................................................4

Chapter 2 Theoretical Considerations...................................................................5

Chapter 3 Experiment Apparatus, Sample Preparation, and ExperimentalProcedures.......................................................................................................6

Experimental Apparatus ................................................................................6

Sample Preparation ......................................................................................7

Experimental Procedure ...............................................................................8

Experiment Loading .............................................................................8

Data Recording ..9

Chapter 4 Experimental Results..........................................................................11

Test Results ................................................................................................11

Equations .....................................................................................................13

Accuracy of Results ...................................................................................14

Discussion of Results .................................................................................15


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Chapter 5 Conclusions ........................................................................................19

Chapter 6 Recommendations ..............................................................................20

Bibliography ........................................................................................................53Vita .....................................................................................................................55


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List of Tables

Table 1: Cement Slurry Design Mix #1 ..........................................................21

Table 2: Cement Slurry Design Mix #2 ..........................................................22

Table 3: Summary for Mix #1.........................................................................23

Table 4: Summary for Mix #2.........................................................................24


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List of Figures

Figure 1: Axial Stress vs. Axial Strain (Sample #2) ........................................25

Figure 2: Total Axial Stress - Axial Strain vs. Elapsed Time (Sample #2)......25



Figure 5: Axial Stress vs. Axial Strain (Sample #4) .........................................27



Figure 8: Total Axial Stress - Axial Strain vs. Elapsed Time (Sample #5)......28Figure 9: Axial Stress vs. Axial Strain (Sample #6) .........................................29




Figure 13: Axial Stress vs. Axial Strain (Sample #8) .........................................31




Figure 17: Axial Stress vs. Axial Strain (Sample #10) ......................................33

Figure 18: Total Axial Stress - Axial Strain vs. Elapsed Time (Sample #10)....33







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Figure 29: Axial Stress vs. Axial Strain (Sample #16) .......................................39


Figure 31: Total Axial Stress - P-wave Velocity vs. Elapsed Time...................40

Figure 32: Dynamic vs. Static Constrained Modulus Mix #1 (Wicked)............40

Figure 33: Dynamic vs. Static Constrained Modulus Mix #2 (Wicked)............41

Figure 34: Dynamic vs. Static Constrained Modulus Mix #1 (Not Wicked).....41

Figure 35: Dynamic vs. Static Constrained Modulus Mix #2 (Not Wicked).....42

Figure 36: Dynamic - Static Constrained Modulus vs. Elapsed Time

Mix #1 (Wicked)...............................................................................42


Mix #2 (Wicked)...............................................................................43


Mix #1 (Not Wicked)........................................................................43


Mix #2 (Not Wicked)........................................................................44

Figure 40: Young's Modulus vs. Elapsed Time Mix #1 (Wicked).....................44

Figure 41: Young's Modulus vs. Elapsed Time Mix #2 (Wicked).....................45

Figure 42: Young's Modulus vs. Elapsed Time Mix # 1 (Not Wicked).............45

Figure 43: Young's Modulus vs. Elapsed Time Mix #2 (Not Wicked)..............46

Figure 44: P-wave Velocity vs. Elapsed Time Mix # 1 (Wicked) .....................46


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Figure 45: P-wave Velocity vs. Elapsed Time Mix #2 (Wicked) ......................47

Figure 46: P-wave Velocity vs. Elapsed Time Mix # 1 (Not Wicked) ..............47

Figure 47: P-wave Velocity vs. Elapsed Time Mix #2 (Not Wicked) ...............48


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List of Illustrations

Illustration 1: Cement Slurry Sleeve (Side View).............................................49Illustration 2: Cement Slurry Sleeve (Top View)..............................................49

Illustration 3: Apparatus Setup Diagram...........................................................50

Illustration 4: Normal Sample (Side View).......................................................50

Illustration 5: Normal Sample (Top View)........................................................51

Illustration 6: Damaged Sample (Side View)....................................................51

Illustration 7: Damaged Sample (Top View) ....................................................52


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Nomenclature

DevAx : Deviatoric Axial Stress

L Ax : Axial Load

L AxMean : Mean Axial Load

A: Sample Contact Area

Ax : Axial Strain

Ax1: Axial Transducer Reading 1

Ax2: Axial Transducer Reading 2

Ax1i:

Initial Axial Transducer Reading 1Ax2i: Initial Axial Transducer Reading 2

P c: Confining Pressure

H: Sample Height

Rad: Radial Strain

Rad1: Radial Transducer Reading 1

Rad2: Radial Transducer Reading 2

Rad1i: Initial Radial Transducer Reading 1

Rad2i: Initial Radial Transducer Reading 2D: Sample Diameter

TotAx : Total Axial Stress

Mean : Mean Stress

NRS: Non-Recoverable Strains

E: Youngs Modulus

Vp: P-wave Velocity

StatC p: Static Constrained Modulus

DynC p: Dynamic Constrained Modulus


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CHAPTER 1: INTRODUCTION

Literature Review

Cementing is an essential operation during construction of an oil or gas well. The

quality of the cement behind a casing plays a vital role during drilling of the next interval,

the production period of the well, and has a serious impact on secondary cementing,

work-over and stimulation operations. 1

Gas migration is a common problem in petroleum drilling operations. Ongoing

problems with sustained annular gas pressure on producing wells worldwide is a prime

indicator that more work is needed in understanding how cement system design can

impact long-term annular isolation. One important area is the relative expansion or

shrinkage of cement systems during hydration in the annulus of a well. Cement expansion

or shrinkage is a dynamic process that may take many hours or even days before anysignificant degree of volumetric stability is achieved. 2

Service companies and operators have become more aware of the many factors

that can influence long-term zonal isolation in a cemented annulus. It is now apparent

that a significant change in the physical volume of set cement in an annulus, whether it is

an excessive reduction (shrinkage), or increase (expansion), can play a major role in the

determination of success or failure for long-term annular isolation. 2

Past efforts within the well cementing industry focused attention on the long-term

competency of the cement sheath under the stress conditions expected during the life of


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the well. Recent study 18 showed that tensile strength of cement is a much more important

factor in maintaining zonal isolation than is the compressive strength of the material

during early stage of well completion.

Cement Shrinkage contributes to gas migration (early pore pressure decrease), to

interfacial bonds, and to pressure integrity. Reduction of the absolute volume, which

occurs when water and cement particles combine to form hydrates, is the phenomena that

causes this chemical shrinkage. This volume change proceeds continuously, at different

rates, from the time of cement mixing until the time of final hardening several weeks or

months later. 5

The fact that most typical Portland cement systems exhibit some degree of

shrinkage hydration process is well documented, and for the most part is now accepted

within the industry. A wide variety of tests and devices have been developed in an effort

to quantify both the type and amount of shrinkage that occurs, although the oil and gas

industry has not standardized testing for cement volumetric changes during hydration. 2

Immediately after mixing, shrinkage occurs at a low rate because of minerals

dissolution. Then shrinkage increases during cement setting and slows down during the

hardening phase, as hydration of other phases produce long term low rate shrinkage. 5

According to Muller et al. 15, shrinkage of the cement begins at initial set and is most

pronounced from three to six hours of elapsed time. After six hours, the rate of shrinkage

declines.

Cement shrinkage is divided between a bulk (or outer) shrinkage, and a matrix (or

inner) one. The relative importance of these two types of shrinkage depends on the

balance between the inter-granular stresses and the local tensile ones which are induced


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by the shrinkage. Inner shrinkage creates, at the time of cement setting, a secondary or

extra porosity, mainly made of free and inter-connected pores, which enhances cement

permeability, and therefore contributes to the phenomenon of gas migration.5

Muller et al. 15 observed that class H cement had 1.05% linear expansion during

the ramp phase of the heat-up cycle. After 24 hours the sample had a total linear

contraction of 3.05%. Similar results were experienced with different cement types. The

slurries tested exhibited linear expansion until the time of initial compressive strength.

Once compressive strength is developed, cement undergoes a period of pronounced

shrinkage. The rate of shrinkage diminishes with time, producing an average of 3 to 4

percent linear shrinkage in 24 hours 12.

Bonding performances are also affected by cement chemical shrinkage during

hydration, as well as by stress changes induced by down-hole deformations or variations

in hydrostatic pressure, and by variation with the wettability and the surface condition of

the casing and formation. Few data are available regarding the contribution of other

cement physical properties, such as shrinkage and stress-strain relationships, on cements

effectiveness in properly isolating zones. 5

The total Hydration Volume Reduction (HVR) for high-cement-content slurries

(90 lbm/ft 3) can exceed 7%. With unrealistic restraints applied with an impermeable

diaphragm, plastic-state shrinkage of over 6% has been measured 14. Although not directly

noted as such, some investigators have associated plastic-state shrinkage with gas-

migration and cement-bonding mechanism. In isolated annuli, plastic-state shrinkage can

contribute to poor bond interpretations, even when good annular sealing is achieved. 12


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Problem Statement

This study had three objectives:

1. Documentation of material behavior during curing in a carefully controlled

environment in order to develop a better understanding of physical and chemical

processes that are active during curing;

2. Measurement of material properties for input into numerical modeling of

well-bore casing behavior; and

3. Shakedown measurements for the design of more elaborate studies of

cement-casing behavior in cemented casings.


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C HAPTER 2: T HEORETICAL C ONSIDERATIONS

Beirute and Tragesser 3

pointed out several shortcomings in existing cement

behavior testing methodology:

1. Reference measurements were made at 8, 12, or 24 hours after the slurry was mixed.

As a result, the most chemical reactive stage of cement setting was overlooked.

2. Cement samples were cured in confined molds under temperature and pressure that

were not always representative of down-hole conditions.

3. The test specimens had to be removed from the curing environment before test

measurements were made; they were transferred in and out of the curing environment

during the entire test period.

As a result, curing temperature and pressures have not, in most cases, been

representative of conditions encountered in wells. Data were determined at atmospheric

pressure and room temperature. 8 In addition, when cement shrinks, free water is allowed

to stand. Free water has a slower transit time than the set cement, thus slowing down

ultrasonic travel time, resulting in lower compressive strength predictions as a result. 13

This project concerns the three problems mentioned above. Experimental results

can be useful because the amount of shrinkage in API class H cement at down-hole

temperatures and pressures is significant. With shrinkage of 2.7%, good bonding of the

cement to casing and formation is uncertain. Achievement of isolation is probably

questionable. Thus, cement shrinkage during setting can lead to a poor cement job, inter-

zone communication, and lack of fracture containment during hydraulic fracturing. 13


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C HAPTER 3: E XPERIMENTAL APPARATUS , SAMPLE

PREPARATION , AND E XPERIMENTAL P ROCEDURES

Experimental Apparatus

Currently, the procedure for tracking the cement setting process is the Ultrasonic

Cement Analyzer (UCA) which yields by estimates the cement compressive strength

from sound velocities. The UCA can be used throughout the entire setting process over

several days or weeks.7

The equipment used in this project, the Simultaneous Pressure System (SPS), is

designed to measure stress and strain of the sample under triaxial testing condition.

Ultrasonic transducers housed in the end platens of the apparatus provides for

sending and receiving electronic pulses through the sample. Shear and compressional

waves are generated and detected. A pressure chamber provides for testing cement

slurries under various confining pressures. Illustration 3 indicates the function of each

test apparatus. The acquired data were then used in calculating P-wave velocity, NRS,

Youngs modulus, and static and dynamic modulus.


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Sample Preparation

For test purposes, two cement mixes were provided by BJ Services. Both cement

mixes were Class H cement and water. Mix #1 (Table 1) contained a small trace of Silica

ASA-301, and mix #2 (Table 2) contained a small amount of bentonite gel and BA-90.

The additional chemicals provide more solid control, thus ensure a better experimental

result when high pressure is being applied to the sample slurries.

Slurry mixtures for each of the specimens were prepared according to API

Specification 10A. An electronic balance was used to weight dry Class H cement, silica

flour (ASA-301), bentonite gel, and BA-90. Controlled accuracy of 0.01 grams was used.

A plastic container was used to mix dry chemicals first to ensure a uniform blend, before

combined to liquid chemicals.

In this test, the only liquid component was water, which had been weighed in the

same manner as the solid chemicals. Water was first mixed at 4,000 RPM for 15 seconds.

Then the dry blend of cement and chemicals was added in while the mixer turns to ensure

a uniform mix. The mixer was then switched to 12,000 RPM for 35 seconds.

Mix #1 was used for sample #2, 7, 8, 9, 10, 11, 12, and 16.

Mix #2 was used for sample #3, 4, 5, 6, 13, 14, and 15.


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Experimental Procedure

Experiment Loading

Modified rubber sleeves (2 ID 4 height) were used to hold the cement slurry.

A thin lead sheet (0.025 inch) was glued to the top and bottom ends of the SPS contact to

provide acoustic coupling and to prevent corrosion of the transducer load. Then, resin

296 V-9 was used to coat both contact surfaces.

A clamp ring connected the rubber sleeve and Linear Variable Displacement

Transducers (LVDT); it also provided satiability for the cement slurry sample. These

procedures precede slurry mixing.

The axial LVDT was secured into position. The top end of the SPS contact was

then lowered to make contact with the cement slurry. After filling the jacket with the

cement slurry (and removing excess water from the top of the specimen), the top platen

was inserted into the jacket, and the three alignment rods were secured to the bottom and

top end platens. At this point the sample end platen assembly was a continuous

column.

Axial specimen length was determined directly by measurement of the spacing

between the platens. Also, the reference axial displacement transducer output

corresponding to this initial state was measured and recorded. No subsequent adjustments

of the axial displacement transducer position were made, and all subsequent changes in

length were relative to this initial position.


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Excess water was removed for some of the tests. Then before inserting the sample

into the pressure chamber, initial LVDT readings were taken for reference reading points.

The sample was lowered into the pressure vessel carefully to minimize sample

disturbance.

The entire sample loading procedure from the end of slurry mixing to sample

installation is approximately 15 to 20 minutes. It usually takes more than 48 hours for the

cement slurry to turn into solid concrete blocks, and during that period electronic pulses

were periodically sent through the sample and recorded by a computer program. Test

duration for all specimens was one week.

Data Recording

A diagram of the entire apparatus setup is presented in illustration 3.

The first wave velocity measurement was carried out when initial contact was

made between the sample and the transducers. All waveforms readings were digitized

and recorded as a function of time.

P-wave and S-wave are generated by an ultrasonic transducer and propagated

through the sample in the SPS machine. Data were sent to an oscilloscope, which convert

data into digital format.

Waveform data were then transferred to a computer. The entire test progress was

monitored using a data acquiring program, which also controls confining pressure applied

to the sample.

In the case of specimens to be cured under confining pressure, the sample

assembly was placed in the pressure vessel and the confining pressure (200 psi or 1 kpsi)


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was applied. Length changes were measured continuously during the initial 24-hour

curing stage. However, for specimens cured under no confining pressure, no mechanism

was available to maintain contact between the specimen and end platens (and hence the

axial displacement transducers) as the sample shortened. Only after application of a small

confining pressure then could specimen length be determined.

The initial positioning was not carried out for sample #2, 3, and 4, so no specimen

shortening during the initial 24-hour curing period was determined for those specimens.

These test conditions were repeated for Specimens # 16, 14, and 15, respectively -

including initial positioning of the axial displacement transducer - and measurements of

total specimen shortening were carried out for the initial 24 hour curing period.

Shear wave propagation measurements proved to be problematic for this series of

measurements. No S-wave propagation is possible prior to solidification of the cement.

Moreover, the lead shims used for isolation of platens and specimen led to a degradation

of signal quality, and determination of first arrival times for velocity determinations was

not reliable. No shear wave velocity measurements are reported for these tests.

A data file of time, confining pressure, and axial load (stress and strain) was

generated by the computer program. Using those data, P-wave velocity, Non-Recoverable

Strain (NRS), static and dynamic modulus, and various other deformation and acoustic

parameters were calculated indirectly.


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C HAPTER 4: E XPERIMENTAL R ESULTS

Test Results

A total of 15 cement slurry samples were tested. Solidified cement cylinders from

confined and ambient conditions were tested. Illustrations 4, 6, and 7 shows cement

samples after the test.

Using Excel as the primary analysis tool, a deformation spreadsheet was

constructed for each test. Deviatoric axial stress, axial strain, radial strain, total axial

stress, and mean stress as a function of elapsed time were plotted in the deformation

spreadsheet. The equations used for calculating those parameters are listed at the end of

this section.

Table 3 and 4 tabulates selected data for both mix #1 and mix #2, respectively P-

wave velocity, NRS, Youngs modulus, both static and dynamic constrained modulus for

selected data points within each trial.

Amplitudes of P-waves against elapsed time were plotted, and the initial time for

the first wave was selected as the reference time. Subsequent waves were then shifted in

time to overlap the reference waveform. Travel times were calculated and tabulated as

differences in P-wave velocity.

Various deformation and acoustic parameters were plotted based on the P-wave

velocity data. Axial stress vs. axial strain plots are available for each sample trial as

Figure 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, and 29. Total axial stress axial


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strain vs. elapsed time plots are also available for each sample trial plots as Figure 2, 4, 6,

8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, and 30.

In addition, plots of dynamic vs. static constrained modulus (Figure 32, 33, 34,

and 35), static & dynamic constrained modulus vs. elapsed time (Figure 36, 37, 38, and

39), Youngs modulus vs. elapsed time (Figure 40, 41, 42, and 43), and P-wave velocity

vs. elapsed time (Figure 44, 45, 46, and 47) for Mix #1 and #2 (H 2O wicked and not

wicked for each) are also available in the appendix.


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Equations

1. Deviatoric Axial Stress

DevAx = (L Ax L AxMean ) / A

2. Axial Strain

Ax = {[Ax1 + Ax2 (Ax1i+Ax2i) ] / 2 DevAx P c } / H

3. Radial Strain

Rad = [Rad1 + Rad2 (Rad1i+Rad2i) ] / D

4. Total Axial Stress

TotAx = DevAx + P c

5. Mean Stress

Mean = ( TotAx + 2 P c ) / 3


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Accuracy of Results

The mixing procedure followed API standards. However, loading of the sample

into the SPS apparatus required a longer time period than usual cement testing

procedures. It required approximately 15 to 20 minutes from end of cement slurry mixing

to the time when the cement slurry sample is securely inside the SPS pressure chamber.

As a result, the accuracy of the experimental results was possibly affected. Fortunately,

transducer outputs began once the electrical transducers are connected to the rubber

sleeve. Cement slurry usually takes more than 48 hours to harden, which made the extra

loading time somewhat less significant.

Based on results from previous projects, the SPS equipment itself is very reliable.

Voltage readings were all within 2% accuracy (compared with previous projects) during

the electric transducer connection stage, and minimum movements were maintained

when lowering the samples into the SPS pressure chamber.

The initial problem of chemical reaction between the sample and SPSs aluminum

surface was resolved by using thin lead sheets to separate the sample from the contacting

ends. Illustration 5 shows effects of chemical reaction between cement and coated resin.

For later trials, non-sticking cooking spread was used for coating the contacting surface

to reduce possible chemical reactions.


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Discussion of Results

P-wave Velocity

P-wave velocity for all tests increased non-linearly with increasing elapsed time.

According to the plots, P-wave velocity of early elastic behavior acted in increasingly

complex behavior and eventually showed development of a pronounced failure cone.

Then the stress-strain curve increased non-linearly, followed by slowly changing total

stress with increasing total strain i.e., what is usually called plastic behavior.

Stress Strain Analysis

Axial stress versus axial strain plots show that recoverable, non-recoverable, and

failure behavior. Figure 3 is an example of axial stress vs. axial strain plot for sample #3.

Total axial stress axial strains versus elapsed time plots during post shrinkage

period are also plotted for each sample. For example, Figure 8 is one such plot for sample

#5.

Most of the samples did not experienced failure, except sample #8, 11, and 12.

Those samples encounter failure strain approximately 14 hours after mixing. The

exceptional failure result is possibly due to the confining pressure applied, but no certain

conclusion can be drawn.

From the data result in table #3 and #4, samples from mix #2, not wicked

category experienced cement failure at a relatively later time. Based on this result, free


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water content (which is low in mix #2 and wicked samples) is vital in reducing cement

failure.

Non-Recoverable Strain

As seen in the axial stress vs. axial strain plots, NRS is much larger for the first

unloading cycle than for the succeeding unloading cycles. While NRS can be as high as

10 milli-strains for some first unloading cycles, it is often immeasurable or less than 1

milli-strain for the subsequent unloading cycles.

Measured NRS for each sample is tabulated in Tables #3 and 4. Average NRS for

wicked mix #1 samples is 2.3 milli-strains, for not-wicked mix #1 samples is 7 milli-

strains, for wicked mix #2 samples is 1 milli-strain, and for not-wicked mix #2 samples is

1.75 milli-stains.

Non-recoverable strain is in general higher for mix #1 than for mix #2 and higher

for not wicked than wicked samples. The additional bentonite content in mix #2 (which

reduces free water) and not having the samples wicked (which also reduces free water)

seems to have a negative effect on NRS. It can be concluded that minimizing the amount

of free water in the cement is an important factor in reducing cement failure. Based on

the data shown in the summary tables, no conclusive evidence can be drawn about the

effect of confining pressure on NRS.

Youngs Modulus

Youngs modulus ( E ) for each unloading cycle was obtained from axial stress

versus axial strain plot. A linear trend line through each unloading cycle gives Youngs


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modulus. For example, since the axial stress vs. axial strain plot for sample #3 had five

different unloading cycles, five different Youngs modules were measured from those

unloading cycles. Based on the plots, Youngs modulus increased with each succeeding

unloading cycle, and with increasing curing time.

Youngs Modulus was also plotted against elapsed time for mix#1 and #2 (both

H2O wicked and not-wicked samples). Plots show that Youngs modulus increased with

elapsed time, and values of Youngs modulus are higher for wicked samples than not-

wicked ones. These results indicate that free water content causes acceleration of cement

stiffness.

Static and Dynamic Constrained Modulus

Static constrained modulus ( StatCp ) was calculated using the equation:

StatCp = E (1- )/((1+ )/(1-2 )), where E is Youngs modulus and is Poissons ratio.

(Some S-wave velocity data were obtained. However, the quality was too low to be

usable. Thus, an estimated value of 0.25 was used as Poissons ratio for data analyses).

Static constrained modulus was plotted against both dynamic constrained modulus and

elapsed time. For example, Figure 36 shows trend of static & dynamic constrained

modulus as a function of elapsed time for H 2O-wicked mix #1. The plots show that both

static and dynamic constrained modulus increased non-linearly as time increases.

Dynamic constrained modulus ( DynCp ) was calculated using the equation:

DynCp = V 2 , where is cement density and V is P-wave velocity. Dynamic constrained

modulus was plotted against both static constrained modulus and also elapsed time. For


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example, Figure 32 shows dynamic constrained modulus vs. static constrained modulus

for H 2O-wicked mix #1. Such plots were made for both H 2O wicked and not-wicked

samples. In general, both static and dynamic constrained modulus values were lower for

wicked samples. This observation suggests that wicking (which is equivalent to lower

free water content) is a retarding process that prevents cement from becoming stiffer.

Future Cement Shrinkage Research

Future research on cement shrinkage will consider length changes to the cement

sample being hardening. Graphically, cement shrinkage may be obtained from the total

axial stress axial strain versus elapsed time plot by evaluating the difference between

the two curves.


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C HAPTER 5: C ONCLUSIONS

From the data taken and the graphs plotted, the following conclusions are drawn:

Use of silica flour or bentonite gel resulted in no experiment difference on

cement properties, at least with the small amounts used in these experiments.

P-wave velocity increased in a non-linear fashion with elapsed time during the

unloading stage of the stress-strain cycle.

NRS are generally lower for mix #2 and wicked samples, which suggest free

water content as a controlling factor in minimizing cement failure.

Youngs modulus ( E ), static constrained modulus ( StatCp ), and dynamic

constrained modulus ( DynCp ) all increased with elapsed time and higher for

wicked than not wicked samples, indicating that stiffness increased with

additional cement settling time and free water content.


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C HAPTER 6: R ECOMMENDATIONS

The cement designed and used had some free-water, as evidenced by visible water

separation from the cement slurry 10 minutes after initial mixing. Expanding vermiculite

could be used in early slurry to provide improvement to other lightening additives such as

bentonite and microspheres, which was commonly used to prevent hydrostatic pressure

reduction during the waiting-on-cement period.

The time needed to load the experiment should be reduced to five minutes or less.

UCA test sets the sample loading time at 60 seconds; for SPS tests, sample loading time

must be shortened to 5 minutes or less.

A method should be developed to obtain reliable S-wave data in order that

Poissons ratio can be calculated and applied.

Finally, the addition of UCA equipment is recommended.


34/68

21

Tables:

Table 1 Cement Slurry Design Mix #1

18.00Slurry

Volume (mls) 600 Project#

Yield(cu

ft/sk) 1.619 Slurry SG 2.158 Distri ct: Appl ied techTotalFluid (gps) 5.175

TotalFluid % 46.501 Analys t: DTM

Cement Brand: Grams Mix H20 Ab. Vol. Desired MixH20

Cement Mix H20 Cement: H 557.83 Fresh 0.1199 Ab.Vol.

GPS 4.575 Poz: 0.00 Sea 0.1169 0.1199 % 40.596 Slag/Other : 0.00 COMMENTS

%NACL: NACL 0.00%KCL: KCL 0.00% bwoc gal/sk Add # Additive Grams

1 ASA- 301 1.292 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.00

10 0.0011 0.0012 0.00

Fresh H20: 326.14


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22

Table 2 Cement Slurry Design Mix #2

18.00Slurry

Volume (mls) 600 Project#

Yield(cu

ft/sk) 1.619 Slurry SG 2.158 Distri ct: Appl ied techTotalFluid (gps) 5.175

TotalFluid % 46.501 Analys t: DTM

Cement Brand: Grams Mix H20 Ab. Vol. Desired Mix H20Cement Mix H20 Cement: H 840.36 Fresh 0.1199 Ab. Vol.

GPS 4.575 Poz: 0.00 Sea 0.1169 0.1199 % 40.596 Slag/Other : 0.00 COMMENTS

%NACL: NACL 0.00%KCL: KCL 0.00% bwoc gal/sk Add # Additive Grams

1 Bent. Gel 3.362 BA-90 25.213 0.004 0.005 0.006 0.007 0.008 0.009 0.00

10 0.0011 0.0012 0.00

Fresh H20: 319.56


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23

Table 3 Summary for Mix #1

Test#

RealTime(hr) H 2OWick P(cure) NRS

E(kpsi)

StatCp(kpsi)

Vp(ft/sec) DynCp(kpsi)

2 25.1 2 hr 0 2 1553 465.9 10042 3871.8

25.8 1553 465.9 10314 4083.726 1553 465.9 10332 4098.5

49.6 1569 470.7 11223 4835.472.3 3661 1098.3 11680 5237.895.6 5759 1727.7 12049 5573.5

167.9 6929 2078.7 12387 5891.2

16 22.5 30 min 0 3 1330 399 8004 2459.723.0 1330 399 9112 3187.423.8 1330 399 9552 3503.024.1 1330 399 9805 3690.924.4 1330 399 9805 3690.9

9 23.9 30 min 1000 2 1120 336 8674 2888.724.6 2148 644.4 8867 3018.549.1 2149 644.7 10880 4544.978.8 2150 645 11619 5183.0

122.4 2151 645.3 11967 5498.3

10 24.2 NO 0 1 1004 301.2 8269 2625.348.2 2968 890.4 10463 4202.772.2 2969 890.7 11049 4686.872.5 2970 891 11111 4739.8

8 23.7 NO 0 10 1028 308.4 8569 2818.825.8 3193 957.9 9384 3380.948.8 3194 958.2 11153 4775.673.5 3195 958.5 11705 5259.6

11 23.8 NO 0 9 995 298.5 9384 3380.825.6 995 298.5 9845 3721.227.0 996 298.8 10354 4115.727.4 996 298.8 10354 4115.7

12 22.6 NO 200 10 848 254.4 8060 2494.424.5 848 254.4 8436 2732.525.8 849 254.7 8644 2868.727.3 849 254.7 8707 2910.7

7 23.2 NO 1000 5 1006 301.8 8328 2662.424.1 1006 301.8 8506 2777.625.4 1006 301.8 8629 2858.725.5 1007 302.1 8629 2858.7


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24

Table 4 Summary for Mix #2

Test#

RealTime(hr) H 2OWick P(cure) NRS

E(kpsi)

StatCP(kpsi)

Vp(ft/sec)

DynCp(kpsi)

4 24.4 35 min 0 1 1340 402 9257 3290.1725 1340 402 9410 3399.75

25.2 1340 402 9504 3468.1448.4 2657 797.1 11736 5288.0672.5 3363 1008.9 12373 5877.81144 3364 1009.2 12935 6423.67

15 23.6 30 min 0 1 1538 461.4 8403 2710.7124.1 1538 461.4 8718 2918.2024.6 1538 461.4 8989 3101.8325.0 1538 461.4 9030 3130.8725.4 1538 461.4 9059 3150.45

5 0.2 30 min 1000 1 2001 600.3 6809 1779.9324 4560 1368 10788 4467.94

25.3 4560 1368 10995 4641.2626.1 4560 1368 11210 4824.8826.3 4560 1368 11210 4824.8849.2 4561 1368.3 13294 6784.71

121.6 4562 1368.6 14655 8245.85145.6 4563 1368.9 14655 8245.85

3 25.6 NO 0 3 959 287.7 7765 2314.8826.2 959 287.7 8093 2514.4926.5 959 287.7 8116 2528.7126.8 959 287.7 8116 2528.7148.2 2231 669.3 10079 3900.0271.7 4472 1341.6 10638 4344.97

95.6 4473 1341.9 10942 4596.56167.7 4475 1342.5 11263 4870.65

14 21.3 NO 0 2 1273 381.9 9107 3184.1521.6 1273 381.9 9326 3339.1322.1 1273 381.9 9634 3563.3322.5 1273 381.9 9714 3622.7623.4 1273 381.9 9730 3634.70

6 24.9 NO 1000 1 4238 1271.4 9221 3264.5948.2 5257 1577.1 9221 3264.5997.2 5258 1577.4 10729 4419.28

144.3 5259 1577.7 11347 4943.39

13 22.6 NO 200 1 913 273.9 8004 2459.6624.0 913 273.9 8226 2598.11

24.7 913 273.9 8401 2709.76


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Figures:

0

500

1,000

1,500

2,000

2,500

0 1 2 3 4

Axi al Str ain (mil li )

A x i a l

S t r e s s

( p s i

)

5

SSa (24 hr.)SSd (96 hr.)

SSb (48 hr.)

SSf (168 hr .)

SSc (72 hr.)

Figure 1. Axial Stress vs. Axial Strain (Sample #2)

0

500

1,000

1,500

2,000

2,500

0 1 2 3

Elapsed Time (Hour)

T o

t a l A x i a l

S t r e s s

( p s i

)

-5

0

5

10

15

20

25

A x i a l

S t r a i n

( m i l l i )

4

Figure 2. Total Axial Stress - Axial Strain vs. Elapsed Time (Sample #2)

25


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SSa (24 hr.)SSb (48 hr.)

SSc (72 hr.)

0

500

1,000

1,500

2,000

2,500

0 2 4 6 8 10

Axial Strain (milli)

A x

i a l S t r e s s

( p s

i )


0

500

1,000

1,500

2,000

2,500

0 1 2 3 4Elapsed Time (Hour)

T o

t a l A x

i a l S t e s s

( p s

i )

-5

0

5

10

15

20

25

A x

i a l S t r a

i n ( m i l l i )


26


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SSa (24 hr.)SSc (72 hr.)

SSb (48 hr.)

0

500

1,000

1,500

2,000

2,500

0 2 4 6 8 10 Axi al Str ain (m il li )

A x

i a l S t r e s s

( p s

i )


0

500

1,000

1,500

2,000

2,500

0 1 2 3 4

Elapsed Time (Hour)

T o

t a l A x

i a l S t r e s s

( p s

i )

-5

0

5

10

15

20

25

A x

i a l S t r a

i n ( m i l l i )


27


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0

500

1,000

1,500

2,000

2,500

0 2 4 6 8 10

Axial St rai n (m il li)

A x

i a l S t r e s s

( p s

i )


0

500

1,000

1,500

2,000

2,500


T o

t a l A x

i a l S t r e s s

( p s

i )

-5

0

5

10

15

20

25

A x

i a l S t r a

i n ( m i l l i )


28


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SSa (24 hr.)

SSb (48 hr.)SSc (96 hr.)

0

500

1,000

1,500

2,000

2,500

0 2 4 6 8 10 Axi al St rain (m il li )

A x

i a l S t r e s s

( p s

i )


0

500

1,000

1,500

2,000

2,500

0 1 2 3 4

Elapsed Time (Hour)

T o

t a l A x

i a l S t e s s

( p s

i )

-5

0

5

10

15

20

25

A x

i a l S t r a

i n ( m i l l i )


29


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SSa (24 hr.)

0

500

1,000

1,500

2,000

2,500

0 2 4 6 8

Axi al St rai n (mil li)

A x

i a l S t r e s s

( p s

i )

10


0

500

1,000

1,500

2,000

2,500


T o

t a l A x

i a l L o a

d ( p s

i )

-5

0

5

10

15

20

25

A x

i a l S t r a

i n ( m i l l i )


30


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SSa (24 hr.)

SSb (72 hr.)

0

500

1,000

1,500

2,000

2,500

0 2 4 6 8 10 12 14

Axi al St rai n (mil li )

A x

i a l S t r e s s

( k p s

i )


0

500

1,000

1,500

2,000

2,500

0 1 2 3 4 5

Elapsed Time (Hour)

T o

t a l A x

i a l S t r e s s

( p s

i )

-5

0

5

10

15

20

25

A x

i a l S t r a

i n ( m i l l i )


31


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0

500

1,000

1,500

2,000

2,500

0 2 4 6 8 10 Axial St rain (mil li )

A x

i a l S t r e s s

( p s

i )


0

500

1,000

1,500

2,000

2,500

0 1 2 3 4 5Elapsed Time (Hour)

T o

t a l A x

i a l S t r e s s

( p s

i )

-5

0

5

10

15

20

25

A x

i a l S t r a

i n ( m i l l i )


32


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SSb (24 hr.)

SSc (72 hr.)

0

500

1,000

1,500

2,000

2,500

0 2 4 6 8 10

Axial Str ain (mil li )

A x

i a l S t r e s s

( p s

i )SSc (72 hr.)


0

500

1,000

1,500

2,000

2,500

0 1 2 3 4 5

Elapsed Time (Hour)

T o

t a l A x

i a l S t r e s s

( p s i )

-5

0

5

10

15

20

25

A x

i a l S t r a

i n ( m i l l i )


33


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SSa (24 hr.)

0

500

1,000

1,500

2,000

2,500

0 2 4 6 8 10 12 14 Axi al St rain (m il li )

A x

i a l S t r e s s

( p s

i )


-500

0

500

1,000

1,500

2,000

2,500


T o

t a l A x

i a l S t r e s s

( p s

i )

-5

0

5

10

15

20

25

A x

i a l S t r a

i n ( m i l l i )


34


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SSa (24 hr.)

0

500

1,000

1,500

2,000

2,500

0 2 4 6 8 10 12 14

Axi al Str ain (mil li )

A x

i a l S t r e s s

( p s

i )


0

500

1,000

1,500

2,000

2,500

0 1 2 3 4 5

Elapsed Time (Hour)

T o

t a l A x

i a l S t r e s s

( p s

i )

-15

-10

-5

0

5

10

15

20

A x

i a l S t r a

i n ( m i l l i )


35


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SSa (24 hr.)

0

500

1,000

1,500

2,000

2,500

0 2 4 6 8

Axi al Str ain (mi ll i)

A x

i a l S t r e s s

( p s

i )

10


0

500

1,000

1,500

2,000

2,500


T o

t a l A x

i a l S t r e s s

( p s

i )

-5

0

5

10

15

20

25

A x

i a l S t r a

i n ( m i l l i )


36


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SSa (24 hr.)

0

500

1,000

1,500

2,000

2,500

0 2 4 6 8

Axi al St rai n (m ill i)

A x

i a l S t r e s s

( p s

i )

10


0

500

1,000

1,500

2,000

2,500

0 1 2 3 4

Elapsed Time (Hour)

T o

t a l A x

i a l S t r e s s

( p s

i )

-5

0

5

10

15

20

25

A x

i a l S t r a

i n ( m i l l i )


37


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SSa (24 hr.)

0

500

1,000

1,500

2,000

2,500

0 2 4 6 8


A x

i a l S t r e s s

( p s

i )

10


0

500

1,000

1,500

2,000

2,500


T o

t a l A x

i a l S t r e s s

( p s

i )

-5

0

5

10

15

20

25

A x

i a l S t r a

i n ( m i l l i )


38


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SSa (24 hr.)

0

500

1,000

1,500

2,000

2,500

0 2 4 6 8


A x

i a l S t r e s s

( p s

i )

10


0

500

1,000

1,500

2,000

2,500

0 1 2 3 4 5

Elapsed Time (Hour)

T o

t a l A x

i a l L o a

d ( p s

i )

-5

0

5

10

15

20

25

A x

i a l S t r a

i n ( m i l l i )


39


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Mix #1, wicked

0

500

1,000

1,500

2,000

2,500

0 20 40 60 80 100 120 140 160 180 200

Elapsed Time (Hour)

T o

t a l A x

i a l S t r e s s

( p s i

)

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

V p

( f t / s e c

)p5

SS a SS b SS c SS d

p12 p17

p6p7

p20 p26

SS f

Figure 31. Total Axial Stress P-wave Velocity vs. Elapsed Time (Sample #2)

0

1000

2000

3000

4000

5000

6000

7000

0 500 1000 1500 2000 2500

Static Cp (kpsi)

D y n a m

i c C p

( k p s

i )

Test2

Test9

Test16

Figure 32. Dynamic vs. Static Constrained Modulus Mix #1 (Wicked)

40


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0

1000

2000

3000

4000

5000

6000

7000

8000

9000

0 200 400 600 800 1000 1200 1400 1600

Static Cp (kpsi)

D y n a m

i c C p

( k p s

i )

Test4Test5Test15

Figure 33. Dynamic vs. Static Constrained Modulus Mix #2 (Wicked)

0

1000

2000

3000

4000

5000

6000

0 200 400 600 800 1000 1200

Static Cp(kpsi)

D y n a m

i c C p

( k p s i

) Test7Test8

Test10Test11Test12

Figure 34. Dynamic vs. Static Constrained Modulus Mix #1 (Not Wicked)

41


55/68

0

1000

2000

3000

4000

5000

6000

0 200 400 600 800 1000 1200 1400 1600 1800

Static Cp (kpsi)

D y n a m

i c C p

( k p s

i )

Test3Test6Test13Test14

Figure 35. Dynamic vs. Static Constrained Modulus Mix #2 (Not Wicked)

0

1000

2000

3000

4000

5000

6000

7000

0 20 40 60 80 100 120 140 160 180

Elapsed Time (hour)

C p

( k p s

i )Test2 StaticTest2 DynamicTest9 StaticTest9 DynamicTest16 StaticTest16 Dynamic

Figure 36. Dynamic & Static Constrained Modulus vs. Elapsed Time Mix #1(Wicked)

42


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0

1000

2000

3000

4000

5000

6000

7000

8000

9000

0 20 40 60 80 100 120 140 160

Elapsed Time (hour)

C p

( k p s

i )Test4 StaticTest4 DynamicTest5 StaticTest5 DynamicTest15 StaticTest15 Dynamic

Figure 37. Dynamic & Static Constrained Modulus vs. Elapsed Time Mix #2(Wicked)

0

1000

2000

3000

4000

5000

6000

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0

Elapsed Time (hour)

C p

( k p s

i )

Test7 DynamicTest8 StaticTest8 DynamicTest10 StaticTest10 DynamicTest11 StaticTest11 DynamicTest12 StaticTest12 Dynamic

Figure 38. Dynamic & Static Constrained Modulus vs. Elapsed Time Mix #1 (NotWicked)

43


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0

1000

2000

3000

4000

5000

6000

7000

0 20 40 60 80 100 120 140 160 180

Elapsed Time (Hour)

C p

( k p s

i )Test3 StaticTest3 DynamicTest6 StaticTest6 DynamicTest13 StaticTest13 DynamicTest14 StaticTest14 Dynamic

Figure 39. Dynamic & Static Constrained Modulus vs. Elapsed Time Mix #2 (NotWicked)

0

1000

2000

3000

4000

5000

6000

7000

8000

0 20 40 60 80 100 120 140 160 180

Elapsed Time (hour)

E ( k p s

i )Test2Test9Test16

Figure 40. Youngs Modulus vs. Elapsed Time Mix #1 (Wicked)

44


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0

500

1000

1500

2000

2500

3000

3500

4000

4500

5000

0 20 40 60 80 100 120 140 160

Elapsed Time (Hour)

E ( k p s

i )

Test4Test5Test15

Figure 41. Youngs Modulus vs. Elapsed Time Mix #2 (Wicked)

0

500

1000

1500

2000

2500

3000

3500

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0

Elapsed Time (hour)

E ( k p s

i ) Test7


Figure 42. Youngs Modulus vs. Elapsed Time Mix #1 (Not Wicked)

45


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0

1000

2000

3000

4000

5000

6000

0 20 40 60 80 100 120 140 160 180

Elapsed Time (Hour)

E ( k p s

i ) Test3Test6Test13Test14

Figure 43. Youngs Modulus vs. Elapsed Time Mix #2 (Not Wicked)

0

2000

4000

6000

8000

10000

12000

14000

0 20 40 60 80 100 120 140 160 180

Elapsed Time (Hour)

V p

( f t / s e c

)

Test2Test9Test16

Figure 44. P-wave Velocity vs. Elapsed Time Mix #1 (Wicked)

46


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0

2000

4000

6000

8000

10000

12000

14000

16000

0 20 40 60 80 100 120 140 160

Elapsed Time (Hour)

V p

( f t / s e c

)

Test4Test5Test15

Figure 45. P-wave Velocity vs. Elapsed Time Mix #2 (Wicked)

0

2000

4000

6000

8000

10000

12000

14000

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0

Elapsed Time (Hour)

V p

( f t / s e c

) Test7Test8Test10Test11Test12

Figure 46. P-wave Velocity vs. Elapsed Time Mix #1 (Not Wicked)

47


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0

2000

4000

6000

8000

10000

12000

0 20 40 60 80 100 120 140 160 180

Elapsed Time (Hour)

V p

( f t / s e c

)


Figure 47. P-wave Velocity vs. Elapsed Time Mix #2 (Not Wicked)

48


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Illustrations:

Illustration 1. Cement Slurry Sleeve (Side View)

Illustration 2. Cement Slurry Sleeve (Top View)

49


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PanasonicPulse Generator /

Receiver

TektronixStorage

Oscilloscope

Computer

Trigger Load

DisplacementTransducer

Load Cell

Waveform

Digital Output

Illustration 3. Apparatus Diagram

Illustration 4. Normal Sample (Side View)

50


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Illustration 5. Normal Sample (Top View)

Illustration 6. Damaged Sample (Side View)

51


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Illustration 7. Damaged Sample (Top View)

52


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53

Bibliography

1. Backe, K. R., Lile, O. B., A Laboratory Study on Oilwell Cement and ElectricalConductivity, SPE 56539 (October 1999)

2. Goboncan, Virgilio C., Dillenbeck, Robert L., Real-Time Cementexpansion/Shrinkage Testing Under Downhole Conditions for EnhancedAnnular Isolation, SPE/IADC 79911 (February 2003)

3. Beirute, Robert, Tragesser, Art, Expansion and Shrinkage Characteristics ofCements under Actual Well Conditions, SPE 4091 (August 1973)

4. Catala, G. N., Stowe, I. D., Henry, D. J., A Combination of AcousticMeasurements to Evaluate Cementations, SPE 13139 (September 1984)

5. Parcevaux, P. A., Sault, P. H., Cement Shrinkage and Elasticity: A NewApproach for a Good Zonal Isolation, SPE 13176 (September 1984)

6. Chenevert, M. E., Shrestha, B. K., Chemical Shrinkage Properties of OilfieldCements, SPE Drilling Engineering, (March 1991) P.37 43.

7. Backe, K. R., Lile, O. B., Lyomov, S. K., Characterizing Curing Cement Slurries by Electrical Conductivity, SPE 46216 (May 1998)

8. Backe, K. R., Lile, O. B., Lyomov, S. K., Elvebakk, Harald, Skalle, Pal,Characterizing Curing-Cement Slurries by Permeability, Tensile Strength,and Shrinkage, SPE Drilling & Completion, (September 1999) P.162 167.

9. Moreno, Francisco J., Chalaturnyk, Rick, Jimenez, Jaime, Methodology forAssessing Integrity of Bounding Seals (Wells and Caprock) for GeologicalStorage of CO2, M. S. Thesis, University of Alberta, Edmonton.

10. Bonett, Art, Pafitis, Demon, Getting to the Root of Gas Migration, OilfieldReview, (Spring 1996) P.36 49.

11.

Klyusov, Anatoly A., Fattakhov, Zafir M., Klyusov, Vsevolod A., CompressibleCement Compositions Improve Isolation, WorldOil Magazine,WorldOil.Com Online Magazine Articles: Special Focus, (October 2005)

12. Sabins, F. L., Sutton, D. L., Interrelationship Between Critical Cement Propertiesand Volume Changes During Cement Setting, SPE Drilling Engineering,(June 1991) P.88 94.


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13. Moon, Jeff, Wang, Steven, Acoustic Method for Determining the Static GelStrength of Slurries, SPE 55650 (May 1999)

14. Lacy, Lewis L., Rickards, Allan, Analyzing Cements and Completion Gels

Using Dynamic Modulus, SPE 36476 (October 1996)15. Muller, Dan T., Lacy, Lewis L., Boncan, Virgilio Go, Characterization of the

Initial, Transitional, and Set Properties of Oilwell Cement, SPE 36475(October 1996)

16. Al Hammad, Mansour A., Altameimi, Yehya M., Cement Matrix Evaluation,IADC/SPE 77213 (September 2002)

17. Lecolier, E., Rivereau, A., Ferrer, N., Audibert, A., Longaygue, X., Durability ofOilwell Cement Formulations Aged in H2S-Containing Fluids, SPE 99105(February 2006)

18. Mueller, D.T., Eid, R.N., Characterization of the Early-Time MechanicalBehavior of Well Cements Employed in Surface Casing Operations, SPE98632 (February 2006)


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