Coalbed Methane in China: Geological Theory and Development

✍ Scribed by Yan Song; Xinmin Zhang; Shaobo Liu

• Tongue: English
• Leaves: 463
• Category: Library

✦ Table of Contents

Foreword by Yan Song
Foreword by Yan Song
Preface
Contents
1 Status Quo and Research of CBM Exploration and Development
1.1 CBM Development Status Quo in Some Countries
1.1.1 CBM Industry Development in the United States
1.1.2 CBM Industry Development in Other Countries
1.2 CBM Industry Development Course in China—Theory and Technology Status
1.2.1 Development Course
1.2.2 Progress in Basic Research
1.2.2.1 Genesis Types and Identification of CBM
1.2.2.2 Characteristics and Evaluation of Coal Reservoirs
1.2.2.3 Dynamic Field of CBM Reservoirs
1.2.2.4 Forming Process of CBM Reservoirs
1.2.2.5 Adsorption and Desorption Mechanism
1.2.2.6 Evaluation of CBM Resources
1.2.3 Status and Progress of CBM Exploration and Development Technology in China
1.2.3.1 CBM Geophysical Exploration Technique
1.2.3.2 CBM Well Drilling and Completion Technique
1.2.3.3 CBM Stimulation Technique
1.3 Key Scientific and Technological Challenges in CBM Exploration and Development in China
References
2 Genesis and Criteria of CBM
2.1 Geochemical Characteristics of CBM and Its Difference from Natural Gas
2.1.1 Sample Testing Method
2.1.2 Composition and Basic Characteristics
2.1.3 Composition and Distribution of Isotope
2.1.4 Difference and Specificity of Isotope Composition
2.2 Control Factors on Carbon Isotope Indicator
2.2.1 Desorption and Fractionation of Methane Carbon Isotope
2.2.2 Impact of Secondary Biogenic Gas on Methane Carbon Isotope Composition
2.2.3 Impact of Microscopic Composition of Coal Rock on Methane Carbon Isotope Composition
2.3 Genetic Classification and Geochemical Tracer System
2.3.1 Primary Biogenic CBM
2.3.2 Thermally Degraded CBM
2.3.2.1 Composition of Drained CBM
2.3.2.2 Composition of Desorbed CBM
2.3.2.3 Composition of Isotopes
2.3.3 Thermally Cracked CBM
2.3.3.1 CBM Geochemical Composition Characteristics
2.3.3.2 Genetic Types and Tracer Indicators
2.3.4 Secondary Biogenic CBM
2.3.4.1 Geology of Liyazhuang Coalmine
2.3.4.2 Geochemical Composition and Genetic Types
2.3.5 Mixed CBM
2.3.5.1 Xinji CBM
Geology
Geochemical Composition and Genetic Types
2.3.5.2 Enhong CBM
Geology
Geochemical Composition and Genetic Types
2.3.5.3 Resources Significance of Secondary biog- Enetic CBM
2.3.6 Tracer Indicator System
2.4 Characteristics and Formation Mechanism of Secondary Biogenic CBM
2.4.1 Characteristics
2.4.2 Organic Geochemistry and Microbial Degradation
2.4.2.1 Soluble Organic Matter in Coal Rock
2.4.2.2 Thermal Evolution and Sedimentary Environment
Thermal Evolution
Sedimentary Environment
2.4.2.3 Microbial Degradation
2.4.2.4 Detection of iC25 and iC30 Acyclic Isoprenoid Alkanes and Their Geological Significance
Distribution Characteristics of Acyclic Isoprenoid Alkanes in Coal Rock Samples
Detection of iC25 and iC30 Acyclic Isoprenoid Alkanes and Their Geological Significance
2.4.2.5 Experiments on Methanogenic Bacteria and Microbial Colonies in Coal Rocks
Experimental Study on Heterotrophic Bacteria
Enrichment and Isolation of Methanogenic Bacteria
Gas Production Experiment on Methano-genic Bacteria from Coal
2.4.2.6 Organic Geochemistry of Coal Rock and Generating Mechanism of CBM
References
3 Characterization and Controlling Factors of CBM Reservoirs
3.1 CBM Reservoir Space
3.1.1 Pore System
3.1.1.1 Pore System in Highly Metamorphic Coals in Qinshui Basin
Basic Structure
Development Degree of Pore System
3.1.1.2 Pore System of Medium- and Low-Rank Metamorphic Coal Reservoirs in Eastern Ordos Basin
3.1.2 Fracture System
3.1.2.1 Large Fracture System
Development Characteristics
Control Factors on Large Fracture Systems
Genesis Model of Large Fracture Systems
3.1.2.2 Microfracture System
3.2 Characterization and Mathematical Model of Favorable Coal Reservoirs
3.2.1 Pore System Model
3.2.1.1 Modeling and Analysis of Pore System
Cluster Analysis of Pore System
Fractal Mathematical Model of Pore System
Pore System Models
3.2.1.2 Contribution of Pore System Structure to Reservoir Physical Properties
Relationship Between Reservoir Pore System and Physical Properties
Influence of Pore Structure on Desorption, Diffusion and Permeation of CBM
3.2.2 Heterogeneous Models of CBM Reservoir
3.2.2.1 Modelling Method and Coalmine Selection
3.2.2.2 Intralayer Heterogeneous Models
Intralayer Heterogenous Model of No. 15 Coal Seam in Yangquan No. 1 Coalmine
Intralayer Heterogeneous Model of No. 2 Coal Seam in the Qinxin Coalmine
Intralayer Heterogeneous Model of No. 3 Coal Seam in Changcun Coalmine
Intralayer Heterogeneous Model of No. 3 Coal Seam in Sihe Coalmine
3.3 Forming Mechanism and Controlling Factors of Favorable Coal Reservoirs
3.3.1 Coal Diagenesis
3.3.1.1 Control of Sea Level on Heterogeneity
Control of Sea Level on Planar Heterogeneity of Coal Reservoirs
Control of Sea Level on Intralayer Heterogeneity
Control of Sea Level on Interlayer Heterogeneity
3.3.1.2 Relationship Between Ash and Porosity and Permeability
3.3.1.3 Control of Coal Facies
3.3.1.4 Diagenetic Transformation
3.3.2 Changes in Porosity and Permeability During Coalification
3.3.2.1 Relationship Between Metamorphism and Porosity
3.3.2.2 Relationship Between Coal Metamorphism and Pore Size Distribution
3.3.2.3 Relationship Between Coal Metamorphism and Specific Surface Area of Pores
3.3.2.4 Relationship Between Coal Metamorphism and Cleat Development and Coal Seam Permeability
3.3.3 Structural Stress and Strain Response
3.3.3.1 Mechanical Properties of Medium- and High-Rank Metamorphic Coal
Low-Pressure Fractures
High-Pressure Fractures
3.3.3.2 Mechanical Properties of Medium- and Low-Rank Metamorphic Coals
3.3.3.3 Microscopic Deformation Mechanism of Coal Rock
Fracturing Nucleation
Fracture Expansion and Association
3.3.3.4 Stress and Strain Response
3.3.4 Control of Basin Evolution on Coal Reservoir Physical Properties
3.3.4.1 Physical Properties and Geological Factors
Coupling Relationship Among Controlling Factors
Control of Fractures on Permeability
Control of Stress on Permeability
3.3.4.2 Control of Burial History on Permeability
3.3.4.3 Thermal and Maturity Histories on Permeability
References
4 Coal Absorption Characteristics and Model Under Reservoir Conditions
4.1 Experimental Study on Methane Absorption Characteristics Under the Combined Influences of Temperature and Pressure
4.1.1 Isothermal Absorption Experiments
4.1.2 Temperature-Variable and Pressure-Variable Absorption Experiments
4.1.2.1 Experimental Samples
4.1.2.2 Experimental Design
4.1.2.3 Experimental Method
4.1.2.4 Processing of Experimental Data
4.2 Absorption Characteristics of Coal Under Formation Conditions
4.2.1 Effect of Temperature on Coal Absorption Capacity
4.2.2 Effects of Temperature and Pressure on Coal Absorption Capacity
4.2.2.1 Coal Absorption Capacity Investigated by Isothermal Experiments
4.2.2.2 Coal Absorption Capacity Investigated by Temperature- and Pressure-Variable Experiments
4.2.3 Change Mechanism of Adsorption Capacity Under Reservoir Conditions
4.3 Adsorption Model Under Reservoir Conditions
4.3.1 Characteristics Curve of Methane Adsorption
4.3.2 High-Pressure Isothermal Adsorption Curve and Its Correction to k Value
4.3.3 Absorption Model
4.4 Verification and Application of Models
4.4.1 Verified Models by Isothermal Adsorption Experiments
4.4.2 Temperature- and Pressure-Variable Experiment Results and Models
4.4.3 Coal Adsorption Capacity in Qinshui Basin
4.4.3.1 Characteristics of Coal Adsorption
4.4.3.2 Relationship Between Langmuir Volume and Coal Metamorphism
4.4.3.3 Coal Adsorption Capacity
Depth, Temperature and Pressure
Rmax
Coal Absorption Capacity
4.4.4 Scientific and Applied Values
References
5 Dynamic Conditions and Accumulation/Diffusion Mechanism of CBM
5.1 Structural Dynamics for CBM Accumulation
5.1.1 Structural Evolution Laid the Foundation for CBM Accumulation
5.1.1.1 Control of Yanshanian Structural Inversion on CBM Accumulation
5.1.1.2 Profound Influence on CBM Accumulation from Intense Middle Yanshanian Magmatic Events
5.1.1.3 Control of Yanshanian Tectonic Stress Field on CBM Accumulation
5.1.2 Structural Differentiation Causes Complicated Dynamic Conditions
5.1.3 Transformation from Tectonic Dynamics on Coal Seams Controls Permeable CBM Zones
5.1.3.1 Dynamic Conditions Reflected by Photosynthetic Structures of Vitrinite Reflectance
5.1.3.2 Structural Curvature of Coal Seams and Its Indicative Significance for CBM Accumulation
5.1.3.3 Control of Modern Principal Stress Difference on Coal Seam Permeability
5.1.4 Combined Structural Dynamic Conditions Control the Basic Pattern of CBM Accumulation and Distribution
5.2 Thermal Dynamic Conditions and Accumulation/Diffusion History of CBM
5.2.1 Thermal History of Carboniferous–Permian Coal Seams
5.2.1.1 Paleo-Geothermal Field and Thermal History of Qinshui Basin
5.2.1.2 Paleo-Geothermal Field Evolution and Coal Seam Heating History of Ordos Basin
5.2.2 Middle Yanshanian Tectonic Thermal Event and Its Thermodynamic Source
5.2.3 Numerical Simulation of CBM Accumulation/Diffusion History
5.2.3.1 History of CBM Accumulation and Diffusion and Its Regional Differentiation in Qinshui Basin
5.2.3.2 History of CBM Accumulation and Diffusion and Its Regional Differentiation in Ordos Basin
5.2.4 Control of Thermodynamic Conditions on CBM Accumulation
5.3 Control and Mechanism of Underground Hydrodynamic System on CBM Accumulation and Diffusion
5.3.1 Hydrogeological Unit Boundary and Its Internal Structural Differences and Characteristics of CBM Accumulation and Diffusion
5.3.1.1 Qinshui Basin
5.3.1.2 he Southern Segment of the Eastern Margin of Ordos Basin
5.3.2 Underground Hydrodynamics Zoning and CBM-Bearing Characteristics
5.3.2.1 Qinshui Basin
5.3.2.2 The Southern Segment of the Eastern Margin of Ordos Basin
5.3.3 Groundwater Geochemical Field and CBM Preservation Conditions
5.3.3.1 Qinshui Basin
5.3.3.2 The Southern Segment of the Eastern Margin of Ordos Basin
5.3.4 Groundwater Head Height and Gas-Bearing Properties
5.3.5 Control Effect of Groundwater Dynamic Conditions and Its Manifestation
5.3.6 Relationship Between Hydrodynamic Conditions and CBM Enrichment
5.3.6.1 Control of Groundwater on CBM Content
5.3.6.2 Control of Groundwater on Carbon Isotope of CBM
5.3.6.3 Close Relation Between Carbon Isotope Values and CBM Content
5.3.6.4 Control of Groundwater on CBM Reservoirs
5.4 Coupling Controls of Dynamic Conditions on CBM Reservoirs
5.4.1 Geological Dynamic Conditions
5.4.2 Representational Dynamic Conditions
5.4.2.1 Superposition of Reservoir Forming Control Representational Dynamic Conditions
5.4.2.2 In Qinshui Basin
5.4.2.3 In the Southern Segment of the Eastern Margin of Ordos Basin
5.4.3 Energy Dynamic Balance System and Its Geological Evolution Process
5.4.3.1 Elastic Energy and Its Relative Contribution to CBM Accumulation
Elastic Energy of Coal Base Block
Elastic Energy of Water
Elastic Energy of Gas
Total Elastic Energy of Coal Seam
5.4.3.2 Control of the Evolution of Coalbed Elastic Energy on CBM Accumulation in Qinshui Basin
5.4.3.3 Control of the Evolution of Coalbed Elastic Energy on CBM Accumulation Conditions in the Southern Segment of the Eastern Margin of Ordos Basin
5.4.4 CBM Accumulation Effect and Model
5.4.4.1 Elastic Self-Regulating Effect
5.4.4.2 Self-Sealing Effect
5.4.4.3 Effective Pressure System and Effective Migration System
Effective Pressure System and Its Energy Evolution
Efficient Migration System and Its Energy Evolution
5.4.4.4 Control Mechanism of Energy System Evolution on CBM Accumulation
5.4.4.5 CBM Accumulation Types and Energy Accumulation/diffusion Models
Types of CBM Accumulation
Energy Model for CBM Accumulation
References
6 Formation and Distribution of CBM Reservoirs
6.1 Meaning and Types of CBM Reservoir
6.1.1 Meaning of CBM Reservoir
6.1.2 Differences Between CBM Reservoirs and Conventional Natural Gas Reservoirs
6.1.3 Boundary and Types of CBM Reservoir
6.1.3.1 Economic Boundary
6.1.3.2 Hydrodynamic Boundary
6.1.3.3 Weathered and Oxidized Boundary
6.1.3.4 Physical Property Boundary
6.1.3.5 Fault Boundary
6.1.3.6 Lithologic Boundaries
6.1.4 Types of CBM Reservoir
6.1.4.1 Classification Based on Groundwater Dynamic Conditions and Boundaries
6.1.4.2 Classification by Coal Rank
6.2 Accumulation Process and Accumulation Mechanism of Medium- to High-Ranked CBM Reservoir
6.2.1 Theoretical Basis of CBM Accumulation
6.2.1.1 Application of Adsorption Potential Theory in the Change History of CBM Content
6.2.1.2 Application of Adsorption Potential Theory in the Discussion of CBM Desorption and Fractionation Mechanism
Fractionation of 12CH4 and 13CH4 in CBM Desorption-Diffusion Process
Fractionation of Multi-component gas in CBM Desorption Process
6.2.2 Analysis of Reservoir Forming Mechanism of Typical CBM Reservoirs
6.2.2.1 CBM Reservoir Forming Process and Accumulation Mechanism in Southern Qinshui Basin
Scope of CBM Reservoir
Forming Conditions of CBM Reservoir
CBM Accumulation Process
Forming Characteristics of CBM Reservoir
6.2.2.2 Process and Mechanism of CBM Accumulation in the Liulin Area, the Eastern Margin of Ordos Basin
Division of CBM Reservoirs
CBM Accumulation Conditions
Evolution History of CBM Reservoirs
6.2.2.3 Process and Mechanism of CBM Accumulation in the Wangying-Liujia Low-Ranked Coal in Fuxin Basin
Division of CBM Reservoirs
CBM Accumulation Conditions
Evolution History of CBM Reservoirs
6.2.3 Geological Models of CBM Reservoirs
6.2.3.1 Medium- and High-Ranked Coal
More Favorable Enrichment Model
Favorable Enrichment Mode
Unfavorable Accumulation Model
6.2.3.2 Low-Ranked Coal
6.3 Mechanism and Favorable Conditions of CBM Accumulation
6.3.1 Comparison of CBM Source Conditions
6.3.1.1 Genesis of High-Ranked CBM
6.3.1.2 Genesis of Low-Ranked CBM
Genesis
Physical Simulation Experiment on Low-Ranked Biogenetic CBM
6.3.2 Comparison of CBM Reservoir Conditions
6.3.2.1 Pore Structure Comparison
6.3.2.2 Permeability Comparison
6.3.2.3 Adsorption Characteristics
Influencing Factors
Comparison of Adsorption Characteristics
6.3.3 Features of CBM Occurrence Comparison
6.3.3.1 Occurrence State Comparison
Adsorbed CBM
Free CBM
Dissolved Gas
6.3.3.2 Comparison of CBM Content
6.3.4 Reservoir Forming Process
6.3.5 Hydrogeological Conditions
6.3.5.1 Hydrodynamic Conditions Comparison
6.3.5.2 Hydrodynamic Simulation Experiment
Different Influence of Hydrodynamics
6.3.5.3 Comparison of Geochemical Characteristics of Groundwater
6.3.5.4 Influence of Groundwater Geochemistry on CBM Accumulation
Influence of Groundwater Geochemistry on Low-Ranked CBM Accumulation
Differences in Groundwater Geochemistry on CBM Accumulation
6.4 Controlling Factors and Distribution Rules of CBM Enrichment
6.4.1 Structural Control and Key Period
6.4.1.1 Controlling Mechanism and Key Controlling Period of Tectonic Evolution on CBM Accumulation
6.4.1.2 Three Geological Models of Tectonic Evolution Control
6.4.1.3 Case Analysis and Application
6.4.2 Control of Effective Overburden and Coal Seam Top and Bottom on CBM Accumulation
6.4.2.1 The Sealability of Coal Seam Top and Bottom and Their Control on CBM Enrichment
6.4.2.2 Control of Effective Overburden Thickness on CBM Enrichment
6.4.3 Theory of CBM Enrichment in Synclines
References
7 Evaluation and Prediction of Technically Recoverable CBM Resources
Abstract
7.1 Classification System
7.2 Prediction Methods of CBM GTR
7.2.1 Controlling Factors on CBM Recoverability
7.2.1.1 Geological Factors
7.2.1.2 Well Pattern
7.2.1.3 Development Technology
7.2.1.4 Market, Gas Price, Policies and Regulations, Etc.
7.2.2 Determination Methods for Important CBM Parameters
7.2.2.1 Statistical Prediction of Coal Seam Permeability
Controlling Factors on Coal Seam Permeability
Statistical Prediction of Coal Seam Permeability Changing with Burial Depth
Case Analysis
7.2.2.2 Determination Methods for CBM GRF
Desorption Experiment
Isothermal Adsorption Curve
Gas Reservoir Numerical Simulation
CBM Gas Content Attenuation Rate
Material Balance Method
Analogy Method
7.2.2.3 Determination Methods for Lignite Gas Content
CBM Reservoir Properties
Determination Methods for CBM Gas Content
7.2.3 Predicting Methods of CBM GTR
7.2.3.1 Calculating Methods
7.2.3.2 Gas Reservoir Numerical Simulation
Analysis of Basic Characteristics
Division and Description
Determination of Grids in a Block
Selection of Typical CBM Production Wells in a Block
Numerical Simulation (Establish a CBM Reservoir Model and Calculate EUR)
Establish EUR Probability Distribution
Calibrate CBM GTR
7.2.3.3 Loss Analysis
7.3 Potential Analysis of CBM GTR in China
7.3.1 Division of CBM Enrichment Units
7.3.1.1 Sequence of CBM Enrichment Units
Definition of CBM Enrichment Unit
Sequence Divisions of CBM Enrichment Units
7.3.1.2 Division Scheme of CBM Enrichment Units in China
7.3.2 Predicted CBM GTR in China
7.3.2.1 Scope and Units Calculated
Scope
Unit
7.3.2.2 Calculating Methods
Gas-Enriched Belts Explored and Developed
Gas-Enriched Belts not Explored or Developed
7.3.2.3 Predicted Results
Results
Result Evaluation
7.3.3 Distribution of CBM GTR in China
7.3.3.1 CBM-Bearing Regions
7.3.3.2 CBM-Bearing Basins
7.3.3.3 GTR Statistics by Types of CBM Reservoir
7.3.3.4 GTR Statistics by Reservoir Depth
References
8 Seismic Prediction Technology of Favorable CBM Zones
8.1 Primary Geological Attributes of CBM Occurrence and Prediction
8.1.1 Seismic Survey to Coal Seam Depth
8.1.2 Coal Seam Thickness from Seismic Inversion
8.1.3 Roof Lithology from Seismic Inversion
8.1.3.1 Linear Regression Method for Single Attribute
8.1.3.2 Linear Regression Method for Multiple Attributes
8.1.3.3 Regression Method of Multiple Attributes with a Convolution Operator
8.1.3.4 Nonlinear Statistical Methods
8.1.4 Seismic Waveform Classification for Predicting CBM Content
8.2 Multiwave Seismic Responses and Prediction of Fractures in Coal Seams
8.2.1 Multiwave Seismic Responses of Vertical Fractures
8.2.2 Detection of Vertical Fractures by Multiwave Seismic Data
8.2.2.1 Extract Mixed-Phase Wavelet
8.2.2.2 Suppress Surface Wave
8.2.2.3 Model-Driven CCP Three-Parameter Velocity Analysis
8.2.2.4 Model-Based Distortion-Free NMO Correction to Converted Wave
8.2.2.5 Use Multi-wave Seismic Data to Obtain Primary Fracture Orientation
8.2.2.6 Separate Fast from Slow Waves
8.3 AVO Inversion and Prediction of CBM Enrichment Zones
8.3.1 Basic Dynamics of AVO Theory
8.3.2 The Basis of Using AVO to Detect CBM
8.3.3 AVO Responses of Controlling Geological Parameters on CBM Enrichment
8.3.3.1 AVO Responses of Coal Structure, and Roof and Floor Lithology
8.3.3.2 AVO Response of Coal Seam Thickness
8.3.4 AVO Responses of CBM Enrichment Zones
8.3.5 Three-Parameter AVO Method for CBM Zones
8.3.6 Three-Parameter AVO Prediction of CBM Enrichment Zones
References
9 Comprehensive Evaluation of Geological Conditions for Coalbed Methane Development
9.1 Favorable Zones for Coalbed Methane Development in China
9.1.1 Overview of Coalbed Methane Resources in China
9.1.2 Comprehensive Evaluation and Optimum Selection of Favorable Areas for CBM Development
9.1.2.1 Distribution of CBM
9.1.2.2 Factors Considered in Selecting Gas Enrichment Zones
9.1.2.3 Gas Accumulation Areas Selected
9.1.2.4 Analysis, Validation, Application
9.2 Evaluation and Optimization of CBM Enrichment Zone (Target Area) in Key Basins
9.2.1 Evaluation Methods, Parameter and Criteria
9.2.1.1 Theoretical Basis and General Idea
Overview of Analytic Hierarchy Process
Ideas for Optimizing CBM Accumulation Areas
9.2.1.2 Key Parameters for Selecting Favorable CBM Areas
Gas-Bearing Factors
Coal Reservoir Factors
9.2.1.3 Evaluation System of CBM Reservoir
Methods and Models
Selection Method of CBM Accumulation Zones in China
Principle of Optimal Segmentation Method
9.2.2 Evaluation of CBM Enrichment Zones (Target) in Key Coal Basins
9.2.2.1 Geological Survey of Key Coal Basins
Ordos Basin
Qinshui Basin
Junggar Basin
9.2.2.2 Case Study on Ordos Basin
CBM Enrichment Zones Divided
Screened by Area and Resource Abundance
Screened by Gas Content
Ordered by Key Factors
Selected by Fuzzy Comprehensive Evaluation Method and Optimal Segment Method
9.2.2.3 Optimized CBM Enrichment Zones in Typical Basins
References
10 Desorption-Seepage Mechanism and Development Schemes
10.1 Elastic Mechanics of Coal Rock in Multiphase Medium
10.1.1 Triaxial Mechanical Experiment
10.1.1.1 Experimental Equipment
10.1.1.2 Experimental Samples
10.1.1.3 Preparation of Samples
10.1.1.4 Experiment Item
10.1.1.5 Experimental Method
10.1.2 Experimental Principle
10.1.2.1 Static Elastic Modulus and Poisson’s Ratio
10.1.2.2 Volume Compressibility and Bulk Modulus
10.1.3 Triaxial Mechanical Characteristics
10.1.4 Volume Compressibility and Bulk Modulus
10.2 Permeability Change of Coal Reservoir While Mining
10.2.1 Permeability Experiment
10.2.1.1 Equipment and Samples
10.2.1.2 Experiment Scheme and Procedures
10.2.1.3 Experiment Principles
10.2.1.4 Adsorption Expansion and Desorption Shrinkage
10.2.1.5 Field Measurement
10.2.2 Self-regulating Effect Model
10.2.2.1 Study on Effective Stress
10.2.2.2 Coal Matrix Shrinkage
10.2.2.3 Self-regulating Effect Model of Coal Matrix
10.3 Desorption-Seepage Mechanism of CBM in Production Process
10.3.1 Characteristics of CBM Production
10.3.1.1 Desorption Mechanism
10.3.1.2 Diffusion Mechanism
10.3.1.3 Seepage Mechanism
10.3.2 Kinetic Characteristics and Desorption Behavior of CBM Desorption
10.3.2.1 Kinetic Characteristics
Essence and Difference of Adsorption and Desorption of CBM
Dynamic Characteristics and Desorption Types
10.3.2.2 Experiments on Desorption Behavior of CBM
Experimental Methods and Equipment
Absorption and Desorption Reversibility Experiments
Experiments on Desorption Characteristics of CBM
10.3.2.3 Desorption Mechanism of CBM
10.3.3 CBM Seepage Mechanism
10.3.3.1 Experiments on Influencing Factors and Degree
Basic Experimental Methods
Experiments on Seepage Conditions
10.3.3.2 Experiments on Seepage Mechanism of CBM
Experiment Method
Experiment Procedures
10.3.3.3 CBM Seepage Mechanism
Gas Flow Rate Versus Pressure Gradient
How Adsorbing Boundary Layer Influence CBM Seepage Law
Analysis of CBM Seepage Mechanism
10.4 Optimal CBM Reservoir Development Schemes
10.4.1 CBM Production Performance
10.4.2 Comparison of Development Schemes
References
11 Stimulation Mechanism and Application
11.1 Hydraulic Fracturing Simulation
11.1.1 Experimental Study
11.1.1.1 Mechanical Properties of Coal Rock
Triaxial Mechanical Properties
Tensile Strength
Internal Friction Angle
Dynamic and Static Mechanical Parameters
Laboratory Hydraulic Fracturing Experiment
The Influence of Mechanical Properties of Coal Rock on Hydraulic Fracturing Design
11.1.1.2 Experiments on Conductivity of Coal Rock
Experimental Equipment
Principle of Experiment
Evaluation Methods of Short-Term Conductivity and Their Limitations
Experimental Conditions and Samples
Experimental Results
11.1.2 Characteristics of Induced Fractures
11.1.2.1 Fracture Azimuth and Length
Fracture Azimuth
Fracture Length
Prediction of Effective Fracture Length Contributing to Gas Production
11.1.2.2 Diagnosis of Fracture Height
In-situ Stress
Fracture Height
11.1.3 Fracture Distribution Model
11.1.3.1 Models and Control Equations
Heat Transfer Equation
Seepage Equation
Stress Field Equation
Fracture Propagation Criteria
Disposal of Damage
Interaction of Multiple Fields
Non-uniform Medium Distribution
11.1.3.2 Numerical Simulation Algorithm
11.1.3.3 Numerical Simulation Analysis of Vertical and Horizontal Fractures
The Planar Model of Vertical Fractures
Numerical Simulation Results and Analysis
Numerical Simulation and Analysis of a Plane Model of Horizontal Fractures
11.1.3.4 Numerical Simulation to How In-situ Stress Influences Fracture Propagation
Effect on Fracture Length
Simulation to Fracture Bifurcating
11.1.3.5 Numerical Simulation to How Natural Fractures Influence Fracture Propagation
11.1.3.6 Numerical Simulation to How Heterogeneous Media Influence Fracture Propagation
Rock Heterogeneity
Simulation Results and Analysis of How Heterogeneous Parameters Influence Fracture Propagation
11.1.3.7 Numerical Simulation to How Uneven Temperature Field Influences Fracture Propagation
Temperature Field Model
Numerical Simulation Results
11.1.4 Hydraulic Fracturing Measures and Echnology
11.1.4.1 Increase Effective Fracture Length
Control Fracture Height
Control Multiple Fractures and Increase Effective Fracture Length
11.1.4.2 Reduce Secondary Reservoir Damage and Improve Fracture Conductivity
Improve Fracturing Fluid System to Reduce Reservoir Damage
Develop and Apply Low-Density and High-Strength Proppants
Clean Fractures to Improve Fracture Conductivity
11.2 Stimulation Mechanism of Multi-branch Horizontal Wells
11.2.1 Mathematical and Numerical Models
11.2.1.1 Mathematical Model
Flow Equation of CBM and Water in Dual Media
Pressure-Sensitive Models of Porosity and Permeability
Simplified Model of Multi-branch Horizontal Wells
Wellbore Pressure Drop Model
11.2.1.2 The Numerical Model of CBM Production in Multi-branch Horizontal Wells
Differential Discretization of Gas–Water Two-Phase Flow Equation in Coal Seams
Discrete Form of Wellbore Pressure Drop Model
Solution of Numerical Model
Ideas of Programming Design
11.2.2 Stimulation Mechanism of Multi-branch Horizontal CBM Wells
11.2.2.1 Analysis of Simulation Mechanism
11.2.2.2 Influencing Production Factors
11.2.3 Application Conditions and Economic Analysis
11.2.3.1 Technical Introduction
11.2.3.2 Production Characteristics and Applicable Geological Conditions
Production Characteristics
Suitable Reservoir Conditions
Economic Analysis
11.3 Application Cases
11.3.1 Fracturing Operation and Effect
11.3.1.1 Application to Daning-Jixian CBM Field
11.3.1.2 Application to No. 3 Coal Seam in Xizhuang Block
11.3.2 Application of Multi-branch Horizontal Wells and Result Analysis
11.3.2.1 Application Cases
11.3.2.2 Production Increase
Reference
Appendix_1