USE OF FINITE-ELEMENT ANALYSIS TO IMPROVE WELL CEMENTING IN HTHP CONDITIONS A

266 Pages·2013·11.74 MB·English

by  Joo Sitt Tan

USE OF FINITE-ELEMENT ANALYSIS TO IMPROVE WELL CEMENTING IN
HTHP CONDITIONS

A Dissertation
by
HENRY ARIAS

Submitted to the Office of Graduate Studies of
Texas A&M University
in partial fulfillment of the requirements for the degree of

DOCTOR OF PHILOSOPHY

Chair of Committee, Jerome J. Schubert
Committee Members, Hans Juvkam-Wold
Catalin Teodoriu
Giovanna Biscontin
Head of Department, A. Daniel Hill

August 2013

Major Subject: Petroleum Engineering
Copyright 2013 Henry Arias
ABSTRACT

Oil companies need to evaluate the risk of annular fluid or gas migration if cement
fails during the life of the well. Sustained casing pressure can lead to shutting in the
wells to avoid health, safety, and environment (HSE) risks and government fines. To
understand the long-term integrity of cement in high temperature and high pressure
(HTHP) conditions and the mechanical properties that affect the ability of cements to
seal fluids, this project used finite-element models (FEMs) to study the stress-causing
phenomena. FEM analyses in ABAQUS version 6.11 were used to determine the
potential of cement failure in oil wells. The model uses a 3D section of a well that can be
used for different casing and formation types under different loading conditions.
The model built in ABAQUS version 6.11 allows incorporating materials with
nonlinear mechanical properties; it also uses FEM analysis to forecast fractures inside
the cement under different loading scenarios like hydraulic fracture jobs or casing tests.
The finite-element model included cases for cement cracking, cement debonding, and
plastic deformation of the cement and rock that can generate loss of zonal isolation.
Linear manner: set cements behave elastically until a failure criterion is reached, and
then they can behave plastically. The FEM approach can reproduce stresses, strains, and
volume changes in the material under different environmental HTHP conditions.
Cemented wells have both tensile and compressive stresses that make some parts
of the cement sheath experience fracture initiation, plastic deformation, or debonding.
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This dissertation provides a model that will help drillers design the set cement for long-
term integrity in HPHT well conditions. The FEM predicts if the cement sheath can
develop debonding, cracks or plastic deformations during the life of the well. The
cement sheath needs to be designed for long-term zonal isolation to avoid interzonal
communications, remedial costs and environmental problems related to cement seal.
A CMS™-300 Automated Permeameter, a mechanical properties analyzer, HPHT
cement consistometer, annular expansion molds, and tri-axial test equipment were used
in this study to test cements for specific applications in three Colombian oil fields,
including an oil field with in-situ combustion project.

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DEDICATION

To my parents (in memory) and all my family

To my wife Delvi and my son Leonardo for their love and understanding during
the long period of time to complete this research.

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ACKNOWLEDGEMENTS

I wish to express my sincere thanks and appreciation to the chairman of my
graduate advisory committee, Dr. Jerome J. Schubert, for his continuous guidance,
enthusiasm and support throughout my graduate studies and research. I extend my
appreciation to the other members of the Dissertation Committee, Dr. Hans Juvkam-
Wold, Dr. Catalin Teodoriu, and Dr. Giovanna Biscontin for their suggestions to
complete this work.
I would like to express to my sincere gratitude (in memory) to Dr. James E.
Russell, who encouraged me to pursue this Ph.D. at Texas A& M University. His
knowledge and kindness have been continuous reasons for admiration.
I would like to acknowledge the invaluable help and knowledge provided by all
to the faculty and staff at the Department of Petroleum Engineering at Texas A&M
University, especially to Dr. Christine Ehlig-Economides, Dr. A. Daniel Hill, Dr.
Stephen A. Holditch, Dr. Hans Juvkam-Wold, Dr. Peter P. Valkó, Dr. Darla-Jean
Weatherford, and Dr. Ding Zhu, for providing me the opportunity to pursue my studies
for the Master’s Degree and Ph.D. at Texas A&M University.
Finally, I express my sincere indebtedness to all engineers at Ecopetrol S.A.,
Halliburton Colombia, and Kimeca de México, especially to Jenny Carvajal, Sergio
Acosta, Gino Nucci, Luis Ignacio Valderrama, Javier Urdaneta, Juan R. Garzón, Jose
Luis Garcia Lozano, and all my coworkers who believed in this project and gave me the
support necessary to carry it out successfully.
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NOMENCLATURE

A Area, in2
BWOC By weight of cement
CAE Complete Abaqus environment
CAP Calcium aluminate phosphate
CBL-VDL Cement bond log-variable density log
CCS Confining compressive strength, psi
CHP Critical hydration period
C Bulk compressibility, psi-1
b
Co Cohesive strength of cement, psi
c Specific heat, Btu/(lbm×°F)
p
C Rock matrix compressibility, psi-1
r
D Diameter, in
DST Drill stem test
De Fourth-order elasticity tensor
E Young’s modulus, psi
E Young’s modulus of cement, psi
c
E Young’s modulus of formation, psi
f
ECD Equivalent circulating density, ppg
E Dynamic Young’s modulus, 106 psi
D
E Static Young’s modulus, 106 psi
S
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F Force, psi
FEA Finite-element analysis
FEM Finite-element model
FMA Fluid migration analyzer cell
G Shear modulus, psi
Gps Gallons per sack
H (x) Heaviside function
HPHT High-pressure and high-temperature
ICP Colombian Petroleum Institute
M Hardening parameter
MDT Modular dynamic tester
K Bulk modulus, psi
K Fracture toughness, psi×in0.5
C
K Stress intensity factor, psi×in0.5
I
k, k , k , k Thermal conductivity, Btu/(hr×in×°F)
x y z
K Bulk modulus of the skeleton material, psi
r
L Length, in
lbs/sx Pounds per sack
MPRO Mechanical properties analyzer
P Load at failure, lbf
PEEQ Equivalent plastic strain
p Pore pressure, psi
p
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Q Generated heat, BTU
q , q , q Energy conducted in x,y, and z axis
x y z
ppg Pounds per gallon
S Overburden pressure, psi
So Cohesive strength of rock, psi
S Radial stress
11
S Tangential stress
22
SAGD Steam-assisted gravity drainage
SCP Sustained casing pressure
SCVF Surface casing vent flow
S/Z overburden gradient, psi/ft
T Temperature, °F
T Tensile strength, psi
o
t Compressional wave transit time, s/ft
c
t Compressional wave transit time of the matrix rock, s/ft
ma
t Shear-wave transit time of the matrix rock, s/ft
sma
t Shear-wave transit time, s/ft
s
UCA Ultrasonic cement analyzer
UCS Unconfined compressive strength, psi
UGS Underground gas storage
VM Von Mises stresses
Vp Compressional wave sonic velocity, km/s
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V Shear-wave sonic velocity, km/s
s
V Nonlinear volume of shale
sh
WOC Water/oil contact
Woc Waiting-on-cement time
XFEM Extended finite-elment model
Z Depth, ft
 Linear thermal expansion coefficient, 1/°F
 Biot’s constant
b
α Volumetric thermal expansion coefficient, 1/°F
V
 Tensorial shear strain
ij
 Volumetric strain
vol
ε Total strain
εcp Creep strain
εe Elastic strain
εp Plastic strain
 Engineering strain
ij
 Shear bond strength, psi
 Radial expansion, in
r
 Kronecker delta
ij
 Porosity
ϕ Angle of internal friction of cement
c
ϕ Angle of internal friction of formation
f
ix
 Dilation angle, deg.
d
 Coefficient of internal friction
f
  Bulk density, g/cm3
b
 Maximum normal stress, psi
1
 Intermediate normal stress, psi
2
 Minimum normal stress or confining pressure, psi
3
 Effective stress, psi
ij
 Total stress, psi
ij
 Octahedral stress, psi
oct
 Vertical stress, psi
v
  Minimum horizontal stress, psi
h
  Maximum horizontal stress, psi
H
  Normal stress in x, y directions, psi
xx yy
 Radial stress, psi
r
 Tangential stress, psi

 Poisson’s ratio
 Poisson’s ratio of cement
c
 Poisson’s ratio of formation
f
  Static Poisson’s ratio
s
 Shear stress in the Mohr-Coulomb criterion, psi
 Shear stress acting in the i, j plane; psi
ij
x