Hydraulic Fracturing and Rock Mechanics

Description

This open access book is the first to consider the effect of non-uniform fluid pressure in hydraulic fractures. The book covers the key topics in the process of hydraulic fracture nucleation, growth, interaction and fracture network formation. Laboratory experiments and theoretical modeling are combined to elucidate the formation mechanism of complex fracture networks. This book is suitable for master’s/Ph.D. students, scientists and engineers majoring in rock mechanics and petroleum engineering who need to use a more reliable model to predict fracture behavior. Preface Acknowledgements Contents 1 Introduction 1.1 Background 1.2 Research Progress 1.2.1 Initiation and Propagation of Hydraulic Fracture in Shale Reservoirs 1.2.2 Model of the Intersection of Hydraulic and Natural Fracture 1.2.3 Formation Mechanism of the Complicated Crack Network of Shale 1.2.4 Existing Problems References Part I Theoretical Background 2 Rock Mechanics in Hydraulic Fracturing Operations 2.1 Stress 2.2 Stain 2.3 Linear Elastic Material and Its Failure 2.4 Pressurized Crack References Part II Laboratory Observation 3 Reservoir Characteristics 3.1 Introduction 3.2 Sample Preparation 3.2.1 Sampling Location 3.2.2 Mineral Composition Characteristics 3.2.3 Microstructural Characteristics 3.3 Determination of the Physical and Mechanical Parameters of Shale 3.3.1 Porosity 3.3.2 Permeability 3.3.3 Basic Mechanical Properties of Longmaxi Shale 3.4 Uniaxial Hydraulic Fracturing Characteristics 3.4.1 Experimental Set-Up 3.4.2 Experimental Procedures 3.4.3 Experiment Results and Analysis 3.5 Characteristics of True Triaxial Hydraulic Fracture 3.5.1 Sample Preparation and Test Equipment 3.5.2 Fracturing Scheme 3.5.3 Analysis of Fracturing Results References 4 Constant Flow Injection 4.1 Introduction 4.2 Instantaneous Fracturing Mechanism of Constant Flow Pressurization 4.2.1 Impact of Axial Load 4.2.2 Effect of Injection Rate References 5 Constant Pressure Injection 5.1 Introduction 5.2 Results and Analysis 5.2.1 Typical Curves of Pump Pressure and Injection Rate Versus Time 5.2.2 New Insights from Observing Hydraulic Fracture Morphology 5.3 Correlation Between Fracture Behavior and Pumping Parameters Based on Engineering Parameters 5.4 Characterization of the Relationship Between Fracture Propagation and Pumping Parameters References Part III Theoretical Modelling Considering Non-uniform Fluid Pressure 6 Fracture Initiation 6.1 Breakdown Process Under Constant Injection Flow 6.2 Breakdown Process Under Constant Injection Pressure References 7 Fracture Propagation 7.1 Introduction 7.2 Mathematical Formulation 7.2.1 Nonuniform Fluid Pressure Consideration 7.2.2 Semianalytical Solution 7.2.3 Propagation Conditions Under Nonuniform Fluid Pressure 7.3 Validation of the Semianalytical Solution 7.3.1 Degradation from Nonuniform Pressure to Constant Pressure 7.3.2 Stress Distribution 7.3.3 Critical Propagation Condition 7.4 Parametric Sensitivity Analysis 7.4.1 Reliability Analysis of the Numerical Solution (Perturbation of the Number of Subintervals m) 7.4.2 Sensitivity Analysis of the Initial Fluid Pressure P0 and Crack Length a 7.4.3 Perturbation Analysis of the Number of Terms n Appendix 1. ξ-Integrals Function Appendix 2. Closed—Form of F(ξ) References 8 Fracture Interaction Behaviors 8.1 Introduction 8.2 Intersection Model Between Hydraulic Fracture and Natural Fracture 8.2.1 Solution of Net Pressure Inside the Toughness-Dominated HF 8.2.2 Slippage Condition for the NF 8.3 Validation of Composite Criterion 8.3.1 Comparison with Previous Intersection Criteria 8.3.2 Comparison with Laboratory Experiments 8.4 Composite Criterion Considering Nonuniform Fluid Pressure 8.4.1 Nonuniform Form of Fluid Pressure 8.4.2 Comparison with Laboratory Experiments 8.5 Perturbation Analysis of Key Parameters 8.5.1 Impact of Initial Horizontal In-Situ Stress 8.5.2 Impact of Fracture Toughness 8.5.3 Impact of Approaching Distance References Part IV Field Implication 9 Formation of Complex Networks 9.1 Introduction 9.2 Effect of Bedding Anisotropy on Hydraulic Fracturing 9.2.1 Pump Pressure and Deformation 9.2.2 Acoustic Emission Response of Microfracture 9.2.3 Hydraulic Fracture Morphology 9.3 Effect of Different In-Situ Stress States and Wellbore Orientations on the Formation Mechanism of Complex Fracture Networks 9.3.1 Characteristics of Fluid Pressure and Deformation 9.3.2 Hydraulic Fracture Propagation Modes 9.3.3 Quantitative Evaluation of Fracture Morphology 9.3.4 Effects of Bedding Planes 9.3.5 Effects of In-Situ Stress 9.3.6 Effects of Wellbore Orientations References Epilogue Main Insights Implications for Future Study