Reservoir Formation Damage

Assessment of the FormationDamage Potential CHAPTER 15 Laboratory Evaluation of Formation Damage 456 Summary, 456.. pro-This book provides an understanding of the fundamentals of the rel

RESERVOIR FORMATION DAMAGE

Fundamentals, Modeling, Assessment, and Mitigation

University of OMafcattia

Gulf Publishing Company

Houston, Texas

RESERVOIR FORMATION DAMAGE

Faruk Civan

Copyright ©2000 by Gulf Publishing Company, Houston, Texas.All rights reserved This book, or parts thereof, may not bereproduced in any form without express written permission ofthe publisher

Gulf Publishing Company

Includes bibliographical references and index

ISBN 0-88415-301-0 (alk paper)

1 Hydrocarbon reservoirs 2 Petrolum—Geology I Title.TN870.57.C58 2000

622'.338—dc21 00-027480Printed in the United States of America

Printed on acid-free paper (°o)

my family

and

Dr C M Sliepcevich with love and appreciation

Preface, xv

CHAPTER 1

Overview of Formation Damage

Summary, 1 Introduction, 1 Common Formation

Damage Problems, Factors, and Mechanisms, 4 Team for

Understanding and Mitigation of Formation Damage, 6

Objectives of the Book, 6 References, 7

PARTI

Characterization of the Reservoir Rock

for Formation Damage

CHAPTER 2

Mineralogy and Mineral Sensitivity of

Petroleum-Bearing Formations 10

Summary, 10 Introduction, 10 Origin of Petroleum-Bearing

Formations, 11 Constituents of Sedimentary Rocks, 11

Composition of Petroleum-Bearing Formations, 12 Mineral

Sensitivity of Sedimentary Formations, 14 Mechanisms of

Clay Swelling, 22 Models for Clay Swelling, 25 Graphical

Representation of Clay Content, 42 Hayatdavoudi Hydration

Index (HHI), 43 References, 44

Petrophysics-Flow Functions and Parameters 66

Summary, 66 Introduction, 66 Wettability Alteration, 66

End-Point Saturations, 72 Alteration of the Row Functions:

Capillary Pressure and Relative Permeability, 72 References, 77

CHAPTER 5

Permeability Relationships 80

Summary, 80 Introduction, 80 The Carman-Kozeny Hydraulic

Tubes Model, 80 The Modified Carman-Kozeny Equation

Incorporating the Row Units Concept, 83 The Modified

Carman-Kozeny Equation for Porous Media Altered by Deposition, 84 The

Row Efficiency Concept, 84 The Plugging-Nonplugging Parallel

Pathways Model, 87 Multi-Parameter Regression Models, 92

Network Models, 92 Modified Fair-Hatch Equation, 93

Power-Law Row-Units Equation, 94 Effect of Dissolution/Precipitation

on Porosity and Permeability, 94 Effect of Deposition/Dissolution

and Stress on Porosity and Permeability, 95 Effect of Temperature

on Porosity and Permeability, 95 Exercises, 96 References, 97

CHAPTER 6

Instrumental and Laboratory Techniques for

Characterization of Reservoir Rock 102

Summary, 102 Introduction, 102 Formation Evaluation, 103

X-Ray Diffraction, 107 X-Ray CT Scanning, 107 X-Ray

Fluoroscopy, 108 Scanning Electron Microscope (SEM), 108

Thin Section Petrography, 109 Petrographic Image Analysis,

109 Polarized Light Microscopy, 109 Nuclear Magnetic

Resonance Spectroscopy (NMR), 110 Acoustic Techniques,

111 Cation Exchange Capacity, 111 £ (Zeta)-Potential, 116

Wettability, 117 Mineral Quantification, 120 References, 123

PART 11

Characterization of the Porous Media

Processes for Formation Damage

Transport Equations, 133 References, 138.

CHAPTER 8

Participate Processes in Porous Media 140

Summary, 140 Introduction, 140 Paniculate Processes, 141 ForcesActing Upon Particles, 145 Rate Equations for Paniculate

Processes in Porous Matrix, 148 References, 160

CHAPTER 9

Crystal Growth and Scale Formation

in Porous Media 164

Summary, 164 Introduction, 164 Inorganic Precipitation, 164

Organic Precipitation, 165 Crystallization, 166 Grain Nucleation,

Growth, and Dissolution, 167 Crystallization Kinetics, 171

Particle Growth and Dissolution in Solution, 174 Scale Formation

and Dissolution at the Pore Surface, 176 Crystal Surface

Displace-ment by Dissolution and Precipitation, 178 References, 178

PART III

Formation Damage by Participate Processes

CHAPTER 10

Single-Phase Formation Damage by Fines

Migration and Clay Swelling 183

Summary, 183 Introduction, 183 The Thin Slice Algebraic

Model, 184 The Compartments-in-Series Ordinary Differential

Model, 197 Simplified Partial Differential Model, 199 The

Plugging-Nonplugging Parallel Pathways Partial Differential

Model, 221 Model Considering the Clayey Formation Swelling

and Indigeneous and External Particles, 208 Model Assisted

Analysis of Experimental Data, 213 References, 235

CHAPTER 11

Two-Phase Formation Damage by Fines Migration 238

Summary, 238 Introduction, 238 Formulation, 239 Fluid and

Species Transport, 241 Wettability Transformation and Interface

Transfer of Particles, 247 Particle Retention in Porous Media, 247

Filter Cake Formation on the Injection Face, 251 Model Assisted

Analysis of Experimental Data, 251 References, 259

Cake Filtration: Mechanism, Parameters

and Modeling

Summary, 262 Introduction, 263 Incompressive Cake Filtration,

265 Compressive Cake Filtration Including Fines Invasion, 291

Summary, 323 Introduction, 323 Geochemical Phenomena—

Classification, Formulation, Reactions in Porous Media, 326

Geochemical Modeling, 335 Graphical Description of the Fluid Chemical Equilibria, 339 Geochemical Model Assisted

Rock-Analysis of Solid Mineral—Aqueous Phase Interactions and

Construction of Charts, 344 References, 372

CHAPTER 14

Formation Damage by Organic Deposition 379

Summary, 379 Introduction, 379 Characteristics of

Asphaltenic Oils, 382 Mechanisms of the Heavy Organic

Deposition, 388 Asphaltene and Wax Phase Behavior and

Deposition Envelopes, 392 Asphaltene Adsorption, 405

Empirical Algebraic Model for Formation Damage by

Asphaltene Precipitation in Single Phase, 410 Simplified

Analytic Model for Asphaltene-Induced Formation Damage in

Single-Phase, 414 Plugging-Nonplugging Pathways Model for

Asphaltene Deposition in Single-Phase, 421 Two-Phase and

Dual-Porosity Model for Simultaneous Asphaltene-Paraffin

Deposition, 428 Single-Porosity and Two-Phase Model for

Organic Deposition, 438 References, 449

Assessment of the Formation

Damage Potential

CHAPTER 15

Laboratory Evaluation of Formation Damage 456

Summary, 456 Introduction, 456 Fundamental Processes of

Formation Damage in Petroleum Reservoirs, 458 Selection of

Reservoir Compatible Fluids, 459 Experimental Set-up for

Formation Damage Testing, 459 Special Purpose Core Holders,

461 Guidelines and Program for Laboratory Formation DamageTesting, 470 Core Flood Tests, 478 Laboratory Procedures for

Evaluation of Formation Damage Problems, 478 The Liquid

Block Problem, 481 The Mud Damage Problem, 482

Evaluation of Drilling Muds—Damage Potential and Removal,

482 Evaluation of Hydraulic Fracturing Fluids, 488 Evaluation

of Workover and Injection Fluids, 488 Evaluation of Workover

Damage and Remedial Chemicals, 491 Critical Interstitial FluidVelocity and pH for Hydrodynamic Detachment of Fines in

Porous Media, 491 Scaling from Laboratory to Bottom Hole,

499 Determination of the Formation Damage Potential by

Laboratory Testing, 500 References, 522

CHAPTER 16

Simulator Development 528

Summary, 528 Introduction, 528 Description of Fundamental

Model Equations, 529 Numerical Solution of Formation

Damage Models, 532 Ordinary Differential Equations, 533

Partial Differential Equations, 538 References, 549

CHAPTER 17

Model Assisted Analysis and Interpretation

of Laboratory and Field Tests 552

Summary, 552 Introduction, 552 Measurement Error, 554

Error Analysis—Propagation, Impact, Estimation, 556

Sensitivity Analysis—Stability and Conditionality, 561 Model

Validation, Refinement, and Parameter Estimation, 564

Determination of the Formation Damage Potential by

Simulation, 570 References, 603

XI

Formation Damage Models for

Field Applications

CHAPTER 18

Drilling Mud Filtrate and Solids Invasion

and Mudcake Formation 60S

Summary, 608 Introduction, 608 Simplified Single Phase Mud

Filtrate Invasion Model, 613 Two-Phase Wellbore Mud Invasionand Filter Cake Formation Model, 617 References, 623

CHAPTER 19

Interjectivity of the Water-flooding Wells 627

Summary, 627 Introduction, 627 Injectivity Ratio, 628 Models

Separating the Internal and External Filtration Processes, 632

Diagnostic-Type Curves for Water Injectivity Tests, 639 Modelsfor Field Applications, 641 Models Coupling the Internal and

External Filtration Processes, 643 References, 644

CHAPTER 20

Reservoir Sand Migration and Gravel-Pack Damage: Stress-Induced Formation Damage, Sanding

Tendency, Prediction, and Control 647

Summary, 647 Introduction, 647 Sand Control, 648 Gravel

Design Criteria, 651 Prediction of Sanding Conditions, 655

Massive Sand Production Model, 658 Sand Retention in

Gravel-Packs, 664 References, 665

CHAPTER 21

Formation Damage by Scale Deposition 669

Summary, 669 Introduction, 669 Sulfur Deposition Model, 669

Calcite Deposition Model, 674 References, 677

xn

Diagnosis and Mitigation of Formation Damage

CHAPTER 22

Field Diagnosis and Measurement of

Formation Damage 680

Summary, 680 Introduction, 680 Diagnosis and Evaluation of

Formation Damage in the Field, 681 Pseudo-Damage Versus

Formation Damage, 684 Measures of Formation Damage, 684

Flow Efficiency, 691 Depth of Damage, 693 Model-Assisted

Estimation of Skin Factor, 694 Model-Assisted Analysis of the

Near-Wellbore Permeability Alteration using Pressure Transient

Data, 694 Continuous Real Time Series Analysis for Detection

and Monitoring Formation Damage Effects, 698 Formation

Damage Expert System, 702 References, 703

CHAPTER 23

Formation Damage Control and Remediation 706

Summary, 706 Introduction, 706 Selection of Treatment Fluids,

710 Clay Stabilization, 711 pH-Buffer Solutions, 714 Clay

and Silt Fines, 715 Bacterial Damage, 716 Inorganic Scales,

717 Organic Deposits, 717 Mixed Organic/Inorganic Deposits,

718 Formation Damage Induced by Completion-Fluids and

Crude-Oil Emulsions, 718 Wettability Alteration and Emulsion

and Water Blocks, 718 Intense Heat Treatment, 719

Stimulation by Hydraulic Fracturing, 719 References, 725

Index 730

About the Author 741

Formation damage is an undesirable operational and economic problemthat can occur during the various phases of oil and gas recovery from sub-surface reservoirs including production, drilling, hydraulic fracturing, andworkover operations Formation damage assessment, control, and remediationare among the most important issues to be resolved for efficient exploitation

of hydrocarbon reservoirs Such damage is caused by various adverse cesses, including chemical, physical, biological, and thermal interactions offormation and fluids, and deformation of formation under stress and fluidshear Formation damage indicators include permeability impairment, skindamage, and decrease of well performance The properly designed experi-mental and analytical techniques presented in this book can help understand-ing, diagnosis, evaluation, prevention and controlling of formation damage inoil and gas reservoirs

pro-This book provides an understanding of the fundamentals of the relevantprocesses causing formation damage and reducing the flow efficiency in thenear-wellbore formation during the various phases of oil and gas production;

an update review of the various approaches used in the modeling and tion of formation damage for model assisted analysis and interpretation oflaboratory core tests, and for prediction and control of formation damage; andthe techniques used for assessment, diagnosis, minimization, and control offormation damage in petroleum reservoirs It focuses on the modeling andsimulation of the rock, fluid, and particle interactions, fluid and particle inva-sion, filter cake, in-situ mobilization, migration, and deposition of fines, or-ganic and inorganic precipitation and scale formation, alteration of porosity,permeability, and texture in laboratory cores and reservoir formations, andthe effects of single and multi-phase fluid systems

simula-Formation damage is an interesting interdisciplinary subject that attracts manyresearchers This book is a recapitulation of the present state-of-the-art knowl-edge in the area of formation damage It is intended to be a convenient source

of information, widely spread over different sources I have tried to cover therelevant material with sufficient detail, without overwhelming the readers.This book can be used by those who are engaged in the various aspects of

xv

the knowledge of the theoretical and practical aspects of formation damagefor various purposes, including model assisted interpretation of experimentaltest data, prediction and simulation of various formation damage scenarios,evaluation of alternative strategies for formation damage minimization, andscientific guidance for conducting laboratory and field tests.

Exhaustive effort has been made to gather, analyze, and systematicallypresent the state-of-the-art knowledge accumulated over the years in the area

of formation damage in petroleum reservoirs This book is intended toprovide a quick and coordinated overview of the fundamentals, and theexperimental and theoretical approaches presented in selected publications.However, it should not be viewed as a complete encyclopedic documentation

of the reported studies It discusses processes causing formation damage andreducing the productivity of wells in petroleum reservoirs and systematicallypresents various approaches used in the diagnoses, measurement, production,and simulation of formation damage The techniques for assessment, minimiza-tion, control, and remediation of the reservoir formation damage are described.This book is intended for the petroleum, chemical, and environmentalengineers, geologists, geochemists, and physicists involved in formation dam-age control, and for the undergraduate senior and graduate petroleum engi-neering students Therefore, this book can be used in industry training coursesand undergraduate senior and graduate level petroleum engineering courses It isrecommended for formation damage courses and as a companion for drilling,production, and stimulation courses Readers will:

• Learn the mechanisms and theoretical background of the common mation damage processes

for-• Be familiar with the testing, modeling and simulation techniques able for formation damage assessment, and

avail-• Be able to develop strategies for better management of the adverse cesses to minimize and avoid formation damage in petroleum reservoirs.The material presented in this book originates from my industry shortcourses and curriculum courses at the School of Petroleum and GeologicalEngineering at the University of Oklahoma

pro-I am indebted to the researchers who have contributed to the understandingand handling of the various issues and aspects of formation damage and miti-gation Their efforts have led to the accumulation of a substantial amount ofknowledge and expertise on formation damage and helped develop techniquesand optimal strategies for effective detection, evaluation, and mitigation offormation damage in subsurface reservoirs Their works have been published

in various literature I am pleased to have had the opportunity to analyze,

xvi

age in a consistent manner in one source for the readers of this book Many ofthe figures, tables, and other relevant materials used in the preparation of thisbook were extracted from the literature published by various researchers, com-panies, and organizations These include the following: Academic Press;AAPG—American Association of Petroleum Geologists; ACS—AmericanChemical Society; AIChE—American Institute of Chemical Engineers;American Institute of Physics; API—American Petroleum Institute; ASME—American Society of Mechnical Engineers; A.A Balkema Publisher; BaroidDrilling Fluids, Inc.; Canadian Institute of Mining, Metallurgy and Petroleum;

Chemical Processing magazine; Chemicky Prumysl; Computational

Mechan-ics, Inc.; Elsevier Science, Geological Society, IEEE—Institute of Electricaland Electronics Engineers, Inc.; International Institute for GeothermalResearch, Italy; Ilinois State Geological Survey; John Wiley & Sons Limited;Marcel Dekker, Inc.,; M-I L.L.C.; Plenum Press; Sarkeys Energy Center atthe University of Oklahoma; SPE—Society of Petroleum Engineers;SPWLA—Society of Professional Well Log Analysis; Transportation Research

Board; National Academies, Washington, D.C.; Turkish Journal of Oil and Gas; and the U.S Department of Energy In addition, G Atkinson, T Dewers,

A Hayatdavoudi, I B Ivanov, P R Johnson, P A Kralchevsky, R Philip, T S.Ramakrishnan, M M Reddy, G W Schneider, H Tamura, and K J Weberallowed the use of materials from their publications B Seyler of the IllinoisState Geological Survey provided the photographs included in the book Thepermission for use of these materials in this book is gratefully acknowledged

I am also grateful to Gulf Publishing Company, Timothy W Calk, andExecustaff Composition Services for their support in the preparation and real-ization of this book Special thanks are due to Susan Houck for her care intyping the manuscript

Any comments, corrections, and suggestions by the readers to improve thisbook are welcomed

Faruk Civan, Ph.D P.E.

University of OklahomaNorman, Oklahoma

xvn

Chapter 1

Overview of Formation Damage

Summary

A comprehensive review of the various types of formation damageproblems encountered in petroleum reservoirs is presented The factorsand processes causing these problems are described in detail The design

of a team effort necessary for understanding and controlling of the mation damage problems in the field is explained The motivation for thewriting of this book and the specific objectives are stated The approachtaken in the presentation of the materials in this book is explained A briefexecutive summary of the topics covered in the book is given The rolesplayed by different professionals, such as the petroleum and chemical engi-neers, chemists, physicist, geologists, and geochemists, are described

for-Introduction

Formation damage is a generic terminology referring to the impairment

of the permeability of petroleum bearing formations by various adverseprocesses Formation damage is an undesirable operational and economicproblem that can occur during the various phases of oil and gas recoveryfrom subsurface reservoirs including production, drilling, hydraulic fractur-ing, and workover operations As expressed by Amaefule et al (1988) "For-mation damage is an expensive headache to the oil and gas industry."Bennion (1999) described formation damage as: "The impairment of theinvisible, by the inevitable and uncontrollable, resulting in an indeter-minate reduction of the unquantifiable!" Formation damage assessment,control, and remediation are among the most important issues to beresolved for efficient exploitation of hydrocarbon reservoirs (Energy High-lights, 1990) Formation damage is caused by physico-chemical, chemi-cal, biological, hydrodynamic, and thermal interactions of porousformation, particles, and fluids and mechanical deformation of formation

under stress and fluid shear These processes are triggered during thedrilling, production, workover, and hydraulic fracturing operations For-mation damage indicators include permeability impairment, skin damage,and decrease of well performance As stated by Porter (1989), "Forma-tion damage is not necessarily reversible" and "What gets into porousmedia does not necessarily come out." Porter (1989) called this phenom-enon "the reverse funnel effect." Therefore, it is better to avoid forma-tion damage than to try to restore it A verified formation damage modeland carefully planned laboratory and field tests can provide scientificguidance and help develop strategies to avoid or minimize formationdamage Properly designed experimental and analytical techniques, andthe modeling and simulation approaches can help understanding, diagno-sis, evaluation, prevention, remediation, and controlling of formationdamage in oil and gas reservoirs.

The consequences of formation damage are the reduction of the oil andgas productivity of reservoirs and noneconomic operation Therefore, it

is essential to develop experimental and analytical methods for standing and preventing and/or controlling formation damage in oil andgas bearing formations (Energy Highlights, 1990) The laboratory experi-ments are important steps in reaching understanding of the physicalbasis of formation damage phenomena "From this experimental basis,realistic models which allow extrapolation outside the scaleable range may

under-be constructed" (Energy Highlights, 1990) These efforts are necessary

to develop and verify accurate mathematical models and computer lators that can be used for predicting and determining strategies to avoidand/or mitigate formation damage in petroleum reservoirs (Civan, 1994).Confidence in formation damage prediction using phenomenologicalmodels cannot be gained without field testing Planning and designingfield test procedures for verification of the mathematical models areimportant Once a model has been validated, it can be used for accuratesimulation of the reservoir formation damage Current techniques forreservoir characterization by history matching do not consider the alter-ation of the characteristics of reservoir formation during petroleum pro-duction In reality, formation characteristics vary and a formation damagemodel can help to incorporate this variation into the history matchingprocess for accurate characterization of reservoir systems and, hence, anaccurate prediction of future performance Formation damage is an ex-citing, challenging, and evolving field of research Eventually, the researchefforts will lead to a better understanding and simulation tools that can

simu-be used for model-assisted analysis of rock, fluid, and particle tions and the processes caused by rock deformation and scientific guid-ance for development of production strategies for formation damagecontrol in petroleum reservoirs

interac-In the past, numerous experimental and theoretical studies have beencarried out for the purpose of understanding the factors and mechanismsthat govern the phenomena involving formation damage Although vari-ous results were obtained from these studies, a unified theory and ap-proach still does not exist.

Civan (1996) explains:

A formation damage model is a dynamic relationship expressing thefluid transport capability of porous medium undergoing variousalteration processes Modeling formation damage in petroleum res-ervoirs has been of continuing interest Although many models havebeen proposed, these models do not have the general applicability.However, an examination of the various modeling approaches re-veals that these models share a common ground and, therefore, ageneral model can be developed, from which these models can bederived Although modeling based on well accepted theoreticalanalyses is desirable and accurate, macroscopic formation damagemodeling often relies on some intuition and empiricism inferred bythe insight gained from experimental studies

As J Willard Gibbs stated in a practical manner: "The purpose of a theory

is to find that viewpoint from which experimental observations appear

to fit the pattern" (Duda, 1990)

Civan (1996) states:

The fundamental processes causing damage in petroleum bearingformations are: (1) physico-chemical, (2) chemical, (3) hydrody-namic, (4) thermal, and (5) mechanical Formation damage studiesare carried out for (1) understanding of these processes via labora-tory and field testing, (2) development of mathematical models viathe description of fundamental mechanisms and processes, (3) opti-mization for prevention and/or reduction of the damage potential ofthe reservoir formation, and (4) development of formation damagecontrol strategies and remediation methods These tasks can be accom-plished by means of a model assisted data analysis, case studies, andextrapolation and scaling to conditions beyond the limited test condi-tions The formulation of the general purpose formation damage model

is presented by describing the relevant phenomena on the macroscopicscale; i.e by representative elementary porous media averaging

As stated by Civan (1990):

Development of a numerical solution scheme for the highly non-linearphenomenological model and its modification and verification by

means of experimental testing of a variety of cores from cal porous media are the challenges for formation damage research.

geologi-As expressed by Porter (1989) and Mungan (1989), formation age is not necessarily reversible Thus, it is better to avoid forma-tion damage than try to restore formation permeability using costlymethods with uncertain successes in many cases When a verifiedgeneralized formation damage model becomes available, it can beused to develop strategies to avoid or minimize formation damage.Finally, it should be recognized that formation damage studies involvemany interdisciplinary knowledge and expertise An in-depth review ofthe various aspects of the processes leading to formation damage mayrequire a large detailed presentation Presentation of such encyclopedicinformation makes learning of the most important information difficultand, therefore, it is beyond the scope of this book Instead, a summary

dam-of the well proven, state-dam-of-the-art knowledges by highlighting the tant features, are presented in a concise manner for instructional purposes.The details can be found in the literature cited at the end of the chapters

impor-Common Formation Damage Problems, Factors,

and Mechanisms

Barkman and Davidson (1972), Piot and Lietard (1987), and Amaefule

et al (1987, 1988) have described in detail the various problems tered in the field, interfering with the oil and gas productivity

encoun-Amaefule et al (1988) listed the conditions affecting the formationdamage in four groups: (1) Type, morphology, and location of residentminerals; (2) In-situ and extraneous fluids composition; (3) In-situ tem-perature and stress conditions and properties of porous formation; and(4) Well development and reservoir exploitation practices

Amaefule et al (1988) classified the various factors affecting tion damage as following: (1) Invasion of foreign fluids, such as water andchemicals used for improved recovery, drilling mud invasion, and workoverfluids; (2) Invasion of foreign particles and mobilization of indigenous par-ticles, such as sand, mud fines, bacteria, and debris; (3) Operation con-ditions such as well flow rates and wellbore pressures and temperatures;and (4) Properties of the formation fluids and porous matrix

forma-Figure 1-1 by Bennion (1999) delinates the common formation damagemechanisms in the order of significance Bishop (1997) summarized theseven formation damage mechanisms described by Bennion and Thomas(1991, 1994) as following:

1 Fluid-fluid incompatibilities, for example emulsions generatedbetween invading oil based mud filtrate and formation water

s ion

i

|

Phase Trapping

1

^

Water-based Fluids

r

Solids Invasion

i

r

1

Oil-based Fluids

r

Foamy Oils

ir

|

Perforation Induced

Mechanica Damage

i r

Geomechanical Induced

Dirty Injection Fluids

Rock-Fluid Interactions

^

g i

Wettability Alterations

^

Clay 1 Defloculation 1 —

Adsorption

Fluid-Fluid Interactions

Figure 1-1 Classification and order of the common formation damage mechanisms (modified after Bennion, ©1999; reprinted by

permission of the Canadian Institute of Mining, Metallurgy and Petroleum)

O n>

2 Rock-fluid incompatibilities, for example contact of potentiallyswelling smectite clay or deflocculatable kaolinite clay by non-equilibrium water based fluids with the potential to severely re-duce near wellbore permeability.

3 Solids invasion, for example the invasion of weighting agents ordrilled solids

4 Phase trapping/blocking, for example the invasion and entrapment

of water based fluids in the near wellbore region of a gas well

5 Chemical adsorption/wettability alteration, for example emulsifieradsorption changing the wettability and fluid flow characteristics

of a formation

6 Fines migration, for example the internal movement of fine ticulates within a rock's pore structure resulting in the bridgingand plugging of pore throats

par-7 Biological activity, for example the introduction of bacterial agentsinto the formation during drilling and the subsequent generation

of polysacharide polymer slimes which reduce permeability

Team for Understanding and Mitigation

of Formation Damage

Amaefule et al (1987, 1988) stated that formation damage studies quire a cooperative effort between various professionals These and theirresponsibilities are described in the following: (1) Geologist and geochem-ist on mineralogy and diagenesis and reservoir formation characterizationand evaluation; (2) Chemist on inorganic/organic chemistry, physicalchemistry, colloidal and interfacial sciences, and chemical kinetics; and(3) Chemical and petroleum engineers on transport phenomena in porousmedia, simulator development, interpretation of laboratory core tests,scaling from laboratory to field, interpretation of field tests, and devel-opment and implementation of strategies for formation damage control

re-Objectives of the Book

The focus of this book is to provide sufficient knowledge for the lowing purposes: (1) Understand relevant processes by laboratory andfield testing; (2) Develop theories and mathematical expressions fordescription of the fundamental mechanisms and processes, and phenom-enological mathematical modeling and obtain numerical solutions forsimulator development and computer implementation; (3) Predict andsimulate the consequences and scenarios of the various types of forma-tion damage processes encountered in petroleum reservoirs; (4) Optimizefor prevention and/or reduction of the damage potential of the reservoir

fol-formation; and (5) Develop methodologies and strategies for formationdamage control and remediation.

This book reviews and systematically analyzes the previous studies,addressing their theoretical bases, assumptions and limitations, and pre-sents the state-of-the-art knowledge in formation damage in a systematicmanner The material is presented in seven parts:

I Characterization of the Reservoir Rock for Formation Damage—Mineralogy, Texture, Petrographies, Petrophysics, and Instrumen-tal Techniques

II Characterization of the Porous Media Processes for FormationDamage—Accountability of Phases and Species, Rock-Fluid-Particle Interactions, and Rate Processes

III Formation Damage by Particulate Processes—Fines Mobilization,Migration, and Deposition

IV Formation Damage by Inorganic and Organic cal Reactions, Saturation Phenomena, Deposition, Dissolution

Processes—Chemi-V Assessment of the Formation Damage Potential—Testing, lation, Analysis, and Interpretation

Simu-VI Drilling Mud Filtrate and Solids Invasion and Mudcake FormationVII Diagnosis and Mitigation of Formation Damage—Measurement,Control, and Remediation

References

Amaefule, J O., Ajufo, A., Peterson, E., & Durst, K., "UnderstandingFormation Damage Processes," SPE 16232 paper, Proceedings of theSPE Production Operations Symposium, Oklahoma City, Oklahoma,1987

Amaefule, J O., Kersey, D G., Norman, D L., & Shannon, P M., vances in Formation Damage Assessment and Control Strategies", CIMPaper No 88-39-65, Proceedings of the 39th Annual Technical Meet-ing of Petroleum Society of CIM and Canadian Gas Processors Asso-ciation, Calgary, Alberta, June 12-16, 1988, 16 p

"Ad-Barkman, J H., & Davidson, D H., "Measuring Water Quality and

Pre-dicting Well Impairment," Journal of Petroleum Petroleum Technology,

Vol 253, July 1972, pp 865-873

Bennion, D B., Thomas, F B., & Bennion, D W., "Effective tory Coreflood Tests to Evaluate and Minimize Formation Damage inHorizontal Wells," presented at the Third International Conference onHorizontal Well Technology, November 1991, Houston, Texas.Bennion, D B., & Thomas, F B., "Underbalanced Drilling of Horizon-tal Wells: Does It Really Eliminate Formation Damage?," SPE 27352

Labora-paper, SPE Formation Damage Control Symposium, February 1994,Lafayette, Louisiana.

Bennion, D F., Bietz, R F, Thomas, F B., & Cimolai, M P., tions in the Productivity of Oil & Gas Reservoirs due to Aqueous PhaseTrapping," presented at the CIM 1993 Annual Technical Conference,May 1993, Calgary

"Reduc-Bennion, B., "Formation Damage—The Impairment of the Invisible, bythe Inevitable and Uncontrollable, Resulting in an Indeterminate

Reduction of the Unquantifiable!" Journal of Canadian Petroleum Petroleum Technology, Vol, 38, No 2, February 1999, pp 11-17.

Bishop, S R., "The Experimental Investigation of Formation Damage Due

to the Induced Flocculation of Clays Within a Sandstone Pore ture by a High Salinity Brine," SPE 38156 paper, presented at the 1997SPE European Formation Damage Conference, The Hague, The Neth-erlands, June 2-3 1997, pp 123-143

Struc-Civan, F, Predictability of Formation Damage: An Assessment Study andGeneralized Models, Final Report, U.S DOE Contract No DE-AC22-90-BC14658, April 1994

Civan, F., "A Multi-Purpose Formation Damage Model," SPE 31101paper, Proceedings of the SPE Formation Damage Symposium, Feb-ruary 14-15, 1996, pp 311-326, Lafayette, Louisiana

Duda, J L., "A Random Walk in Porous Media," Chemical Engineering Education Journal, Summer 1990, pp 136-144.

Energy Highlights, "Formation Damage Control in Petroleum Reservoirs,"article provided by F Civan, The University of Oklahoma EnergyCenter, Vol 1, No 2, p 5, Summer 1990

Mungan, N., "Discussion of An Overview of Formation Damage," nal of Petroleum Technology, Vol 41, No 11, Nov 1989, p 1224.

Jour-Piot, B M., & Lietard, O M., "Nature of Formation Damage in Reservoir

Stimulation, in Economides," M J and Nolte, K S (eds.), Reservoir Stimulation, Schlumberger Education Services, Houston, Texas, 1987 Porter, K E., "An Overview of Formation Damage," JPT, Vol 41, No 8,

1989, pp 780-786

Mineralogy and Mineral Sensitivity

of Petroleum-Bearing Formations*

Summary

The origin, mineralogy, and mineral sensitivity of petroleum-bearing mations are reviewed The mechanisms of mineral swelling, alteration, andfines generation are described The models for mineral sensitive properties

for-of rock and the methods for interpretation for-of experimental data are presented

et al., 1988) Formation damage also occurs as a result of the invasion

of drilling mud, cements, and other debris during production, hydraulicfracturing, and workover operations (Amaefule et al., 1988)

This chapter describes the mineral content and sensitivity of typical mentary formations, and the relevant formation damage mechanisms involv-ing clay alteration and migration Analytical models for interpretation andcorrelation of the effects of clay swelling on the permeability and porosity

sedi-of clayey porous rocks are presented (Civan, 1999) The parameters sedi-of the

* Parts of this chapter have been reprinted with permission of the Society of PetroleumEngineers from Civan (1999)

10

models, including the swelling rate constants, and terminal porosity andpermeability that will be attained at saturation, are determined by corre-lating the experimental data with these models The swelling of clayeyrocks is essentially controlled by absorption of water by a water-exposedsurface hindered diffusion process and the swelling-dependent properties

of clayey rocks vary proportionally with their values relative to their ration limits and the water absorption rate These models lead to propermeans of correlating and representing clayey rock properties

satu-Origin of Petroleum-Bearing Formations

As described by Sahimi (1995), sedimentary porous formations areformed through two primary phenomena: (1) deposition of sediments, fol-lowed by (2) various compaction and alteration processes Sahimi (1995)states that the sediments in subsurface reservoirs have undergone fourtypes of diagenetic processes under the prevailing in-situ stress, thermal,and flow conditions over a very long period of geological times:(1) mechanical deformation of grains, (2) solution of grain minerals,(3) alteration of grains, and (4) precipitation of pore-filling minerals,clays, cements, and other materials These processes are inherent in de-termining the characteristics and formation damage potential of petroleum-bearing formations

Constituents of Sedimentary Rocks

Many investigators, including Neasham (1977), Amaefule et al (1988),Macini (1990), and Ezzat (1990), present detailed descriptions of the vari-ous constituents of oil and gas bearing rocks Based on these studies, theconstituents of the subsurface formations can be classified in two broadcategories: (1) indigenous and (2) extraneous or foreign materials.There are two groups of indigenous materials: (1) detrital materials,which originate during the formation of rocks and have restricted forma-tion damage potential, because they exist as tightly packed and blendedminerals within the rock matrix; and (2) diagenetic (or authigenic) mate-rials, which are formed by various rock-fluid interactions in an existingpack of sediments, and located inside the pore space as loosely attachedpore-filling, pore-lining, and pore-bridging deposits, and have greater for-mation damage potential because of their direct exposure to the pore flu-ids Extraneous materials are externally introduced through the wellscompleted in petroleum reservoirs, during drilling and workover opera-tions and improved recovery processes applied for reservoir exploitation

A schematic, pictorial description of typical clastic deposits is given inFigure 2-1 by Pittman and Thomas (1979)

!LY PACKED AUTHIGENIC CLAY IN PORES.

DETUTM ClAY AGGREGATE GRAIN! TIGHTIY

DETKITAL CUV MATRIX NILS PORES

Figure 2-1 Disposition of the clay minerals in typical sandstone (after Pittman

and Thomas, ©1979 SPE; reprinted by permission of the Society of leum Engineers)

Petro-Composition of Petroleum-Bearing Formations

The studies of the composition of the subsurface formations by many,including Bucke and Mankin (1971) and Ezzat (1990), have revealed thatthese formations basically contain: (1) various mineral oxides such asSiO2, A12O3, FeO, Fe2O3, MgO, K2O, CaO, P2O5, MnO, TiO2, Cl, Na2O,which are detrital and form the porous matrix, and (2) various swellingand nonswelling clays, some of which are detrital, and the others areauthigenic clays The detrital clays form the skeleton of the porous ma-trix and are of interest from the point of mechanical formation damage.The authigenic clays are loosely attached to pore surface and of interestfrom the point of chemical and physico-chemical formation damage.Typical clay minerals are described in Table 2-1 (Ezzat, 1990)

However, the near-wellbore formation may also contain other stances, such as mud, cement, and debris, which may be introduced dur-ing drilling, completion, and workover operations, as depicted by Mancini(1991) in Figure 2-2

sub-"Clay" is a generic term, referring to various types of crystalline erals described as hydrous aluminum silicates Clay minerals occupy alarge fraction of sedimentary formations (Weaver and Pollard, 1973) Clayminerals are extremely small, platy-shaped materials that may be present

min-in sedimentary rocks as packs of crystals (Grim, 1942; Hughes, 1951).The maximum dimension of a typical clay particle is less than 0.005 mm(Hughes, 1951) The clay minerals can be classified into three main groups(Grim, 1942, 1953; Hughes, 1951): (1) Kaolinite group, (2) Smectite (or

Table 2-1 Description of the Authigenic Clay Minerals*

Irregular, wavy, wrinkledsheets, webby or honeycomb.Ribbons substantiated byfilamentous morphology

* After Ezzat, ©1990 SPE; reprinted by permission of the Society of Petroleum Engineers

SAND-SIZE RITAL GRAIN

PORE THROAT

CEMENT

MICROPOROSITY

IN CLAY

Figure 2-2 Description of the constituents in typical sandstone (after Mancini,

1991; reprinted by permission of the U.S Department of Energy)

Montmorillonite) group, and (3) Illite group In addition, there are layer clay minerals formed from several of these three basic groups(Weaver and Pollard, 1973).

mixed-The description of the various clay minerals of the sedimentary mations is given by Degens (1965, p 16) The morphology and the majorreservoir problems of the various clay minerals is described in Table 2-2

for-by Ezzat (1990)

Readers are referred to Chilingarian and Vorabutr (1981), Chapters 5and 8, for a detailed review of the clays and their reactivity with aque-ous solutions

Mineral Sensitivity of Sedimentary Formations

Among other factors, the interactions of the clay minerals with ous solutions is the primary culprit for the damage of petroleum-bearingformations Amaefule et al (1988) state that rock-fluid interactions insedimentary formations can be classified in two groups: (1) chemicalreactions resulting from the contact of rock minerals with incompatiblefluids, and (2) physical processes caused by excessive flow rates andpressure gradients

aque-Table 2-2 Typical Problems Caused by the Authigenic Clay Mineral

20 Breaks apart, migrates and concentrates at

the pore throat causing severe pluggingand loss of permeability

100 Extremely sensitive to acid and oxygenated

waters Will precipitate gelatineous Fe(OH)3

which will not pass through pore throats

100 Plugs pore throats with other migrating

fines Leaching of potassium ions willchange it to expandable clay

700 Water sensitive, 100% expandable Causes

loss of microporosity and permeability.100-700 Breaks apart in clumps and bridges across

pores reducing permeability

t After Ezzat, ©1990 SPE; reprinted by permission of the Society of Petroleum Engineers

* After David K Davies—Sandstone Reservoirs—Ezzat (1990)

Amaefule et al (1988) point out that there are five primary factorsaffecting the mineralogical sensitivity of sedimentary formations:

1 Mineralogy and chemical composition determine the

a dissolution of minerals,

b swelling of minerals, and

c precipitation of new minerals

2 Mineral abundance prevails the quantity of sensitive minerals

3 Mineral size plays an important role, because

a mineral sensitivity is proportional to the surface area of als, and

miner-b mineral size determines the surface area to volume ratio ofparticles

4 Mineral morphology is important, because

a mineral morphology determines the grain shape, and thereforethe surface area to volume ratio, and

b minerals with platy, foliated, acicular, filiform, or bladed shapes,such as clay minerals, have high surface area to volume ratio

5 Location of minerals is important from the point of their role in mation damage The authigenic minerals are especially susceptible toalteration because they are present in the pore space as pore-lining,pore-filling, and pore-bridging deposits and they can be exposeddirectly to the fluids injected into the near-wellbore formation.Mungan (1989) states that clay damage depends on (1) the typeand the amount of the exchangeable cations, such as K+, Na+, Ca2+, and(2) the layered structure existing in the clay minerals Mungan (1989)describes the properties and damage processes of the three clay groups

for-as following:

1 Kaolinite has a two-layer structure (see Figure 2-3), K+ exchangecation, and a small base exchange capacity, and is basically anonswelling clay but will easily disperse and move

2 Montmorillonite has a three-layer structure (see Figure 2-4), a large

base exchange capacity of 90 to 150 meq/lOOg and will readilyadsorb Na+, all leading to a high degree of swelling and dispersion

3 Illites are interlayered (see Figure 2-5) Therefore, illites combinethe worst characteristics of the dispersible and the swellable clays.The illites are most difficult to stabilize

Sodium-montmorillonite swells more than calcium-montmorillonitebecause the calcium cation is strongly adsorbed compared to the sodium cat-ions (Rogers, 1963) Therefore, when the clays are hydrated in aqueous

SILICON -OXY6EN TETRAHEDRA SHEET

GIBBSITE SHEET

SILICON-OXYGEN TETRAHEDRA SHEET

O) «<OH)

v x

6® D O ©

b - A X I S KAOLINITE (OH), Al, SI 4 0 IO

Figure 2-3 Schematic description of the crystal structure of kaolinite

(after Gruner-Grim, 1942, and Hughes, 1951; reprinted courtesy of the can Petroleum Institute, 1220 L St., NW, Washington, DC 20005, Hughes,

Ameri-R V., "The Application of Modern Clay Concepts to Oil Field Development,"

pp 151-167, in Drilling and Production Practice 1950, American Petroleum

Institute, New York, NY, 1951, 344 p.)

SILICON - OXV8EN TETRAHEDRA SHEET

T i H 2 O

9.6 - 21.4 A *

SILICON-OXYGEN TETRAHEDRA SHEET

GIBBSITE SHEET

SILICON -OXYGEN TETRAHEDRA

DC 20005, Hughes, R V., "The Application of Modern Clay Concepts to Oil

Field Development," pp 151-167, in Drilling and Production Practice 1950,

American Petroleum Institute, New York, NY, 1951, 344 p.)

SILICON-OXYGEN TETRAHEORA SHEET ~T~

I

SILICON-OXY6EN TETRAHEDRA SHEET

8I88SITE OR BRUCITE SHEET

SILICON-OXYGEN TETRAHEORA SHEET

o

O

AI 4 -Ft 4 -Ms 4 -Mg,)(SI, y -Aly) 0 2O

Figure 2-5 Schematic description of the crystal structure of illite (after Grim,

Bray, and Bradley-Grim, 1942, and Hughes, 1951; reprinted courtesy of theAmerican Petroleum Institute, 1220 L St., NW, Washington, DC 20005,

Hughes, R V., "The Application of Modern Clay Concepts to Oil Field Development," pp 151-167, in Drilling and Production Practice 1950, Ameri-

can Petroleum Institute, New York, NY, 1951, 344 p.)

media, calcium-montmorillonite platelets remain practically intact, close

to each other, while the sodium-montmorillonite aggregates readily swellsand the platelets separate widely Therefore, water can easily invade thegaps between the platelets and form thicker water envelopes around thesodium-montmorillonite platelets than the calcium-montmorillonite plate-lets (Chilangarian and Vorabutr, 1981) as depicted in Figure 2-6.Clay damage can be prevented by maintaining high concentrations of

K+ cation in aqueous solutions At high concentrations of K+ cation, clayplatelets remain intact, because the small size K+ cation can penetrate theinterlayers of the clay easily and hold the clay platelets together(Mondshine, 1973 and Chiligarian and Vorabutr, 1981) as depicted inFigure 2-7

Many investigators, including Mungan (1965), Reed (1977), Khilar andFogler (1983), and Kia et al (1987), have determined that some degree

of permeability impairment occurs in clay containing cores when ous solutions are flown through them This phenomenon is referred to

aque-as the "water sensitivity."

Reed (1977) observed that young sediments are mostly friable ceous sands and proposed a mechanism for damage To justify his theory,

mica-CALCIUM MONTMORILLONITE

It

SODIUM MONTMORILLONITE

SODIUM OR CALCIUM MONTMORILLONITE

Figure 2-6 Expansion of the calcium and sodium montmorillonite byhydration (after Magcobar, ©1972, Fig 2, p 2; reprinted by permission ofthe M-l L.L.C.)

Figure 2-7 Effect of the cation size on the cation migration into a clayinterlayer (modified after Baroid Mud Handbook, 1975, Fig 12, p 21;reprinted by permission of Baroid Drilling Fluids, Inc.)

he also conducted laboratory core tests by flowing various aqueoussolutions through cores extracted from micaceous sand formations Thedata shown by Figure 2-8 of Reed (1977) indicates permeability reduc-tion Based on the severeness of formation damage indicated by Figure2-8, he concluded that mica alteration is a result of the exchange of K+

cations with cations of larger sizes Figure 2-8 shows that the deionizedwater caused the most damage, CaCl2 solution made the least damageand damage by the NaCl solution is in between Thus, the cations in-volved can be ordered with respect to the most to least damaging as

H+>Na+>Ca++ Whereas, Grim (1942) determined the order of placeability of the common cations in clays from most to least easy cat-ions as Li+>Na+>K+>Rb+>Cs+>Mg++> Ca++>Sr++>Ba++>H+ Hughes (1951)states: "hydrogen will normally replace calcium, which in turn will re-place sodium With the exception of potassium in illites, the firmness withwhich cations are held in the clay structure increases with the valence

re-of the cation."

Reed (1977) postulated that formation damage in micaceous sands is

a result of mica alteration and fines generation according to the processdepicted in Figure 2-9 by Reed (1977) and later deposition in porousrock As depicted in Figure 2-10, when clays are exposed to aqueous so-lutions containing no or small amounts of K+ cation or larger cations such

as H+, Ca+2 and Na+, the K+ cation diffuses out of the clay platelets cording to Pick's law, because there are more K+ than the solution In

VOLUME THROUGHPUT (liters)

Figure 2-8 Comparison of the permeability damages by the deionized

water, and calcium chloride and sodium chloride brines in field cores(after Reed, ©1977 SPE; reprinted by permission of the Society of Petro-leum Engineers)

EFFECTS OF MICA ALTERATION:

t PARTICLES MADE SMALLER

2 EXPANDED STRUCTURE

3 PARTICLES MORE MOBILE

4 TRIGGERS INSTABILITY IN OTHER MINERALS

5 PLUGGED PORES AND DECREASED PERMEABILITY

Figure 2-9 Reed's mechanism of mica alteration (after Reed, ©1977 SPE;

reprinted by permission of the Society of Petroleum Engineers)

Relative size of cations

Piece broken off

the brine

Figure 2-10 Schematic explanation of Reed's (1977) mechanism for particle

generation by mica alteration during exposure to low-potassium salt brine

contrast, the larger cations present in the aqueous solution tend to fuse into clays because there are more of the larger cations in the solu-tion compared to the clays Because larger cations cannot fit into theinterplanar gap depleted by K+ cations, the edges of the friable micaflakes break off in small pieces as depicted in Figure 2-10 By a differ-ent set of experiments, Reed (1977) also demonstrated that dissolution

dif-of natural carbonate cement by aqueous salt solution can free mineral ticles held by the cement His reasoning is based on Figure 2-11, indi-cating increased concentrations of Ca+2 in the effluent while thepermeability gradually decreases The fine particles generated by micaalteration and unleashed by cement dissolution can, in turn, migrate withthe flowing fluid and plug pore throats and reduce permeability

par-Mohan and Fogler (1997) explain that there are three processes ing to permeability reduction in clayey sedimentary formations:

lead-1 Under favorable colloidal conditions, non-swelling clays, such askaolinites and illites, can be released from the pore surface and thenthese particles migrate with the fluid flowing through porous for-mation (Mohan and Fogler, 1997)

2 Whereas swelling clays, such as smectites and mixed-layer clays,first expand under favorable ionic conditions, and then disintegrateand migrate (Mohan and Fogler, 1997)

0.10 £

0.04 0.02 3

0.00

VOLUME 3.7* KCI THROUGHPUT (literj)

10

Figure 2-11 Carbonate leaching from a field core by flowing a potassium

chloride brine (after Reed, ©1977 SPE; reprinted by permission of the ety of Petroleum Engineers)