University of Calgary PRISM: University of Calgary's Digital Repository Graduate Studies The Vault: Electronic Theses and Dissertations 2016 Hydraulic Fracturing and Flow-back Simulation in Unconventional Tight Reservoirs Lin, Menglu Lin, M. (2016). Hydraulic Fracturing and Flow-back Simulation in Unconventional Tight Reservoirs (Unpublished master's thesis). University of Calgary, Calgary, AB. doi:10.11575/PRISM/26401 http://hdl.handle.net/11023/2965 master thesis University of Calgary graduate students retain copyright ownership and moral rights for their thesis. You may use this material in any way that is permitted by the Copyright Act or through licensing that has been assigned to the document. For uses that are not allowable under copyright legislation or licensing, you are required to seek permission. Downloaded from PRISM: https://prism.ucalgary.ca UNIVERSITY OF CALGARY Hydraulic Fracturing and Flow-back Simulation in Unconventional Tight Reservoirs by Menglu Lin A THESIS SUBMITTED TO THE FACULTY OF GRADUATE STUDIES IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE GRADUATE PROGRAM IN CHEMICAL AND PETROLEUM ENGINEERING CALGARY, ALBERTA APRIL, 2016 © Menglu Lin 2016 Abstract At present, combination of the multistage hydraulic fracturing and horizontal wells has become a widely used technology in stimulating unconventional tight reservoirs in Western Canadian Sedimentary Basin (WCSB). It is important to understand hydraulic fracture propagation mechanism, effects of their properties and controlling factors affecting flow-back recovery. In this thesis, based on tight reservoir models in WCSB, firstly we examine different fracture geometry distributions and further discuss their effects on well productions. Then reservoir simulation coupled with rock geomechanics is employed to perform dynamic hydraulic fracturing for predicting hydraulic fracture dimensions and simulating fracturing liquid distribution. At last, Design of Experiments and response surface methodology are conducted to explore well operational parameters affecting flow-back recovery and net present value (NPV). This study provides new insights on the hydraulic fracturing and can be a reference for fracturing treatments in unconventional tight reservoirs. ii Acknowledgements I would like to thank my nice supervisor, Dr. Shengnan (Nancy) Chen and my generous co- supervisor, Dr. Zhangxing (John) Chen for their guidance, patience and support during my master study at the University of Calgary. I would also like to thank my respectable committee members: Dr. Christopher Clarkson, Dr. Hossein Hejazi and Dr. Laurence R. Lines for reviewing my thesis and giving insightful comments. I would like to acknowledge the support from the Natural Sciences and Engineering Research Council (NSERC) of Canada and Seven Generations Energy Ltd. I also want to acknowledge the help from Reservoir Simulation Group (RSG) and Department of Chemical and Petroleum Engineering. In addition, I would like to extend the gratitude to all my great friends for making the experience at UCalgary wonderful. In particular, thank you to Mr. Jinze Xu, Mr. Mingxu Ma, and my officemates, Mr. Francisco J. Pacheco and Mr. Muhammad Fowaz Ikram, for their help on my master research. Last but not the least, I appreciate the love, encouragement and support from my family. iii Table of Contents Abstract ............................................................................................................................... ii Acknowledgements ............................................................................................................ iii Table of Contents ............................................................................................................... iv List of Tables ..................................................................................................................... vi List of Figures and Illustrations ........................................................................................ vii List of Symbols, Abbreviations and Nomenclature ........................................................... xi CHAPTER ONE: INTRODUCTION ..................................................................................1 1.1 Background ................................................................................................................1 1.1.1 Tight Resource in Western Canadian Sedimentary Basin .................................1 1.1.2 Hydraulic Fracturing in Tight Reservoirs ..........................................................8 1.2 Research Objectives .................................................................................................14 1.3 Thesis Organization .................................................................................................14 CHAPTER TWO: EFFECT OF FRACTURE GEOMETRY ON WELL PRODUCTION16 2.1 Abstract ....................................................................................................................16 2.2 Introduction ..............................................................................................................17 2.3 Geological Model ....................................................................................................18 2.4 Numerical Simulation Model ...................................................................................20 2.4.1 Reservoir and Fluid Properties ........................................................................20 2.4.2 Relative Permeability Curves and Initial Condition ........................................22 2.4.3 Hydraulic Fracture – Local Grid Refinement ..................................................23 2.4.4 History Matching .............................................................................................24 2.4.5 Microseismic Data ...........................................................................................25 2.4.6 Hydraulic Fracture Geometry Scenarios .........................................................27 2.4.6.1 Scenario 1 ..............................................................................................28 2.4.6.2 Scenario 2 ..............................................................................................29 2.4.6.3 Scenario 3 ..............................................................................................30 2.5 Results and Discussion ............................................................................................32 2.5.1 The Effect of Non-Darcy Flow in Hydraulic Fractures ...................................32 2.5.2 Ideal Planar Fractures - Effect of Main Fracture Length and Conductivity ....33 2.5.3 Effect of Fracture Geometry ............................................................................35 2.5.4 Effect of Secondary Fracture Permeability .....................................................37 2.6 Flow Regime Analysis .............................................................................................40 2.7 Conclusions ..............................................................................................................43 CHAPTER THREE: APPLICATION OF RESERVOIR FLOW SIMULATION COUPLED WITH ROCK GEOMECHANICS ..........................................................................45 3.1 Abstract ....................................................................................................................45 3.2 Introduction ..............................................................................................................46 3.3 Coupled Reservoir Simulation and Barton-Bandis Model ......................................48 3.4 Field Background .....................................................................................................50 3.4.1 Recombined Fluid Analysis ............................................................................51 iv 3.5 Fracturing Simulation ..............................................................................................52 3.6 Reservoir Simulation ...............................................................................................57 3.7 Results and Discussion ............................................................................................60 3.7.1 Effect of Non-Darcy Flow in Hydraulic Fracture ...........................................60 3.7.2 Effect of Pressure-Dependent Permeability of Natural Fractures ...................62 3.7.3 Effect of Well Bottom-hole Pressure ..............................................................65 3.8 Conclusion ...............................................................................................................66 CHAPTER FOUR: SENSITIVITY ANALYSIS ON FLOW-BACK RECOVERY AND NPV IN LIQUID RICH GAS WELL .......................................................................68 4.1 Abstract ....................................................................................................................68 4.2 Introduction ..............................................................................................................69 4.3 Injection and Flow-back of Fracturing Fluid ...........................................................72 4.4 The Effect of Capillary Pressure and BHP ..............................................................77 4.5 The Effect of Well Shut-in Time .............................................................................79 4.6 Sensitivity Study of Flow-back Recovery and NPV ...............................................81