Table Of Content

Hydrofracking.book Page ii Wednesday, March 6, 2013 11:46 AM GULF DRILLING SERIES Casing and Liners for Drilling and Completion Managed Pressure Drilling Underbalanced Drilling: Limits and Extremes Hydraulic Fracturing Explained Hydrofracking.book Page iii Wednesday, March 6, 2013 11:46 AM Hydraulic Fracturing Explained Evaluation, Implementation and Challenges Erle C. Donaldson, Waqi Alam and Nasrin Begum Tetrahedron, Inc Houston, TX Hydrofracking.book Page iv Wednesday, March 6, 2013 11:46 AM Hydraulic Fracturing Explained: Evaluation, Implementation and Challenges Copyright © 2013 Gulf Publishing Company, Houston, Texas. All rights reserved. No part of this publication may be reproduced or transmitted in any form without the prior written permission of the publisher. Gulf Publishing Company 2 Greenway Plaza, Suite 1020 Houston, TX 77046 ISBN: 978-1-933762-40-1 10 9 8 7 6 5 4 3 2 1 Library of Congress Cataloging-in-Publication Data Donaldson, Erle C. Hydraulic fracturing explained : evaluation, implementation, and challenges / Erle C. Donaldson, Waqi Alam, and Nasrin Begum, Tetrahedron, Inc. pages cm. — (Gulf drilling series) Includes bibliographical references and index. ISBN 1-933762-40-3 (978-1-933762-40-1 : alk. paper) 1. Oil wells—Hydraulic fracturing. I. Alam, Waqi. II. Begum, Nasrin. III. Title. TN871.D584 2013 622'.338—dc23 2012047687 Printed in the United States of America ∞ Printed on acid-free paper. Production services and design by TIPS Technical Publishing, Inc. Hydrofracking.book Page v Wednesday, March 6, 2013 11:46 AM Dedication This book is dedicated to Dr. George V. Chilingar who has devoted his life's work to the education of many generations of students that have passed through the hall of the University of Southern California. Dr. Chilingar has also enhanced the knowledge of countless engineers and scientists around the world with a stream of fine technical books that have resulted from his untiring encouragement and assistance to countless co-authors of multiple technical books, and others that he authored and edited through the years. I am personally grateful for his guidance and patient advice throughout my own career. —Erle C. Donaldson This book is also dedicated to all the engineers and scientists who have contributed to the methods of development of energy that is sustainable and fuels our economic growth in a responsible manner. Dedication is also made to our parents, teachers, family members, and friends who inspired us in doing the right things in life. —Waqi Alam and Nasrin Begum Hydrofracking.book Page xi Wednesday, March 6, 2013 11:46 AM Foreword The development of natural gas production from shale beds, which were previously by-passed, has expanded rapidly during the past 20years. This development took place as a result of the improved technology of horizontal well drilling and hydraulic fracturing. Development of this new hydrocarbon resource in many areas that have not previously been impacted by oil production has increased the awareness of this activity with consequent questions regarding the technology, surface environmental impacts, and concerns of fresh water aquifer contamination by the practice of hydraulic fracturing. Hydraulic fracturing is noteworthy because of the relatively large amount of specialized equipment required for its implementation. Shale gas is gradually increasing in importance as a natural hydrocarbon resource that has the potential for replacing a high percentage of the petroleum products currently in large demand. In fact, several large natural gas producing companies are contemplating the introduction of liquefied natural gas stations along the network of automotive express highways for use by vehicles equipped with engines that use natural gas. Thus natural gas may one day fulfill a large part of the demand for automotive energy and ease the future reliance on economically volatile imported hydrocarbon energy sources. Fresh water aquifers near the surface are protected by state and federal regulations and refinements of technology. The accurate assessment of subsurface stress conditions and the mathematics of rock mechanics predict the size and extent of fractures with great accuracy. The use of micro-seismic monitoring during fracture propa- gation to precisely follow the actual growth and extent of the induced fractures in "real time" have all increased the precision of the technology. In addition, the practice of maintaining the integrity of xi Hydrofracking.book Page xii Wednesday, March 6, 2013 11:46 AM xii Foreword overlying formations above the shale formation that is being exploited and the near-surface fresh water aquifers is an added safeguard. At the end of the fracture stimulation (that uses as much as 2 to 4million gallons of water) there is a period when a considerable amount (as much as 30%) of frac-fluid flows back to the surface when the well is placed on production. This fluid contains some of the special chemicals that make up the frac-fluid mixed with brine from the formation. This "flow-back" fracture fluid and formation brine is collected for proper disposal as authorized by state and federal regulations. In some cases the fluid is injected into a deep brine subsurface formation where it is permanently sequestered. If the flow-back can be recovered for reuse in another nearby fracture stimulation project, it will be collected in a tank and moved to the new site since this is most economical for the company. In any case, the water will be treated and processed for proper disposal or re-use; and a vigorous research program is on-going for development of new methods for treating water produced from shale gas operations for reuse. This book is designed to explain the geological aspects (rock mechanics) of hydraulic fracturing in terms that can easily be understood, the technology of hydraulic fracturing and fluids used in the process, and the environmental concerns that have developed as part of the process. Mathematical concepts have been presented in their simplest form with careful attention to the explanation of the theo- ries involved. Some theoretical issues have been removed from the text but are included as appendices for more comprehensive explana- tions. A few example calculations have also been incorporated as AppendixC for further analyses. A glossary of special terms has been attached and all acronyms used in the text are explained in the Nomenclature. Hydrofracking.book Page xiii Wednesday, March 6, 2013 11:46 AM Preface The technology and applications of hydraulic fracturing have enjoyed tremendous growth following advancements of (1) horizontal directional drilling, (2) micro-seismic monitoring of drilling and fracture growth, (3) development of digital imaging software, and (4) the discovery of slick-water (addition of a polymer to fracture fluid that reduced the conductor tubing pressure loss of injected fluids). The first three blossomed together in the 1990s and underwent rapid refinement into the following decade when they were joined by the introduction of slick-water for fracturing gas-shale. The developments of hydraulic fracturing technology were cou- pled to the excitement of the rapid discoveries of gas-shale around the world that could suddenly be produced economically and effi- ciently. This enormously complex endeavor burst into the public domain under a dark cloud of suspicion when allegations of careless, or inept, applications resulting in shallow fresh water contamination by fluids and gas began to appear in widely read publications. Part of the problem seemed to be a lack of understanding of the process: the use of chemical compounds for friction control, fluid viscosity enhancement to enable the conduct of proppants (generally graded sand), corrosion control, and the enormous amount of fluid that is required to fracture sections of long horizontal wells. Two fine, very technical, publications by the Society of Petroleum Engineers: Reser- voir Stimulation and Recent Advances in Hydraulic Fracturing were available along with multiple papers of conferences specifically addressing hydraulic fracturing. All of these are readily available, but the problem associated with them is that they are written at a level that is understood only by engineers. Clearly, there is a need for a comprehensive text on the subject that can explain the salient technical xiii Hydrofracking.book Page xiv Wednesday, March 6, 2013 11:46 AM xiv Preface aspects of the art in terms that can be readily understood by anyone who is truly interested in learning about the amazing technical advances that make hydraulic fracturing possible with fine controls that yield great technical precision in its application. That is the pur- pose and aim of this book. Acknowledgments The authors would like to acknowledge the assistance received from Tetrahedron, Inc., specifically Mr. Daniel Ewald and Ms. Andrea Bou- wkamp, in conducting literature search and drafting. Also, our grati- tude goes to Mr. Robert A. Hefner IV for his encouragement and advice during the writing of this book. Hydrofracking.book Page xv Wednesday, March 6, 2013 11:46 AM List of Figures Figure 1–1 Fracturing the rock formation for production. 2 Figure 1–2 Origin and accumulation of petroleum hydrocarbon. 4 Figure 1–3 Production of hydrocarbons from geological formations using vertical or directional wells. 5 Figure 1–4 Cross-section view of the Eagle Ford Shale. (US Geolog- ical Survey 2010) 6 Figure 1–5 Major shale plays in the United States. 8 Figure 1–6 United States natural gas production, 1990–2035. (US Energy Information Adm., AE02012 Early Release Overview, Jan 23, 2012) 9 Figure 1–7 Source of energy in the United States. (EIA, 2008) 11 Figure 1–8 World demand for oil. (Extrapolated from EIA report on world demand for oil, 2009) 11 Figure 2–1 Burial of successive layers of sediments produced by variations of the surface environment and subsidence. 26 Figure 2–2 Parameters used in Darcy’s Eq.(2.1) where the sub- script e represents the limit of the producing zone where the flow of fluid to the wellbore is zero. The total flow of gas in the wellbore is q (sct/D) and r is the ra- w dius of the well. 31 Figure 2–3 Design of a typical open hole disposal well for protec- tion of useful aquifers. Water pressure in the annulus monitored for leaks. 34 xv Hydrofracking.book Page xvi Wednesday, March 6, 2013 11:46 AM xvi List of Figures Figure 2–4 Two stages of a ball-drop/sleeve fracture system of a horizontal well in a shale bed. The wavy lines w/in the shale indicate micro-fractures. 35 Figure 3–1 An elastic cylinder, with no confining lateral stress, resting on a flat surface and subjected to a vertical compressive stress (lbs./in2). 49 Figure 3–2 Hooke’s Law. Stress is proportional to strain. The slope of the line is equal to Young’s Modulus of elasticity. 49 Figure 3–3 Stress-strain relationship of a rock. Region I: Plastic strain caused by closure of micro-fractures. Region II: Elastic compression of the rock matrix material. Re- gion III: Plastic strain caused by micro-fracture formation in response to the applied stress until failure occurs. 50 Figure 3–4 The shear modulus is the ratio of the shear stress to the angle of deformation (θ, expressed in radians). 51 Figure 3–5 Schematic examples of uniaxial, biaxial and triaxial core-holders and tests. 53 Figure 3–6a Horizontal fracture occurs when the least principal stress is vertical σ > σ > σ where the maximum stress x y y is horizontal, a horizontal fracture will occur. 55 Figure 3–6b Vertical fracture occurs when the least principal stress- es are horizontal σ > σ > σ where the maximum stress z y x is vertical, a vertical fracture will occur. 55 Figure 3–7 Segment of a cylindrical section about a wellbore illus- trating the use of radial coordinates as defined by a set of equations. 56 Figure 3–8 Rupture of the core will normally occur along a diago- nal shear plane when subjected to a compressive stress (σ) under a specific confining stress (σ). 59 z Figure 3–9 I Mohr circles of uniaxial tensile test (σ = 0). r II Mohr circle of uniaxial compressive test (σ = 0). r III Mohr circle of triaxial compressive test (σ > 0) r (σ) = (σ) + (σ ) * tanϕ 59 t Test t 0 n Test Figure 3–10 Mohr Circle example calculations: Semi-circles from laboratory data are solid lines that define the Mohr failure line for the formation rock. The dashed semi- circles represent the conditions expressed by examples I, II, and III. 63 Figure 3–11 The mud pressure at the bottom of the hole propagates the fracture when it is positive and greater than the