AN ASSESSMENT OF RISK OF HYDROCARBON OR FRACTURING FLUID MIGRATION TO FRESH WATER AQUIFERS: CASE STUDY OF COLORADO OIL AND GAS FIELDS by Carver Haentjens Stone A thesis submitted to the Faculty and the Board of Trustees of the Colorado School of Mines in partial fulfillment of the requirements for the degree of Master of Science (Petroleum Engineering). Golden, Colorado Date _______________________ Signed: _______________________________ Carver Haentjens Stone Signed: _______________________________ Dr. Alfred Eustes III Thesis Advisor Golden, Colorado Date _______________________ Signed: ______________________________ Dr. Erdal Ozkan Professor and Head Department of Petroleum Engineering ii ABSTRACT The United States National Science Foundation, engaging 29 researchers at nine institutions, has funded a Sustainability Research Network (SRN) focused on natural gas development. The mission is to provide a science-based framework for evaluating the environmental, economic, and social trade-offs between development of natural gas resources and protection of water and air resources. There are a series of independent events that must occur to allow hydrocarbon or fracturing fluid migration to fresh water aquifers. A statistical analysis of data from 36,682 oil and gas wells, from four main basins in Colorado, was made to demonstrate the low rate of complete wellbore failures that resulted in hydrocarbon or fracturing fluid contamination. These results will help shape the discussion of the risk of oil and gas development and will assist in identifying areas of improved well construction and hydraulic fracturing practices to minimize the risk of aquifer or surface soil contamination. iii TABLE OF CONTENTS ABSTRACT ....................................................................................................................iii LIST OF FIGURES ........................................................................................................vii LIST OF TABLES ......................................................................................................... xv LIST OF SYMBOLS .................................................................................................... xvii ACKNOWLEDGEMENTS .......................................................................................... xviii CHAPTER 1 INTRODUCTION .................................................................................... 1 1.1 Overview of Colorado Oil and Gas Basins ............................................. 2 1.2 Barrier Definition .................................................................................... 3 1.3 Failure Definition .................................................................................... 8 CHAPTER 2 MIGRATION FLOW PATHS AND THE ORIGIN OF HYDROCARBON PRESENCE IN AQUIFER SYSTEMS ....................... 9 2.1 Hydrocarbon Migration Flow Paths ........................................................ 9 2.2 Thermogenic Gas and Biogenic Gas in Fresh Water Aquifers ............. 11 2.3 Fracturing Fluid Migration to Fresh Water Aquifers .............................. 11 CHAPTER 3 METHODS, DATA ASSUMPTIONS AND ERRORS ............................ 15 3.1 Methods ............................................................................................... 15 3.2 Data Assumptions ................................................................................ 16 3.3 Errors ................................................................................................... 18 CHAPTER 4 RISK ASSESSMENT OF OIL AND GAS WELLS IN THE WATTENBERG FIELD, DENVER-JULESBURG BASIN, COLORADO ........................................................................................ 20 4.1 Wattenberg Field Geology ................................................................... 21 4.2 Wattenberg Field Population Density ................................................... 22 4.3 Wattenberg Field Water Sourcing ........................................................ 26 4.4 Wattenberg Field Data Sourcing and Assumptions .............................. 28 4.5 Wattenberg Field Historical Wellbore Designs ..................................... 28 4.6 Wattenberg Field Wellbore Barrier Categories ..................................... 34 iv 4.7 Wattenberg Field Potential Barrier Failures ......................................... 44 4.8 Wattenberg Field Catastrophic Barrier Failure Overview ..................... 47 4.9 Wattenberg Field Catastrophic Barrier Failures ................................... 51 4.10 Wattenberg Field Existing Conditions .................................................. 55 CHAPTER 5 RISK ASSESSMENT OF OIL AND GAS WELLS IN THE PICEANCE BASIN, GARFIELD COUNTY, COLORADO ..................... 60 5.1 Piceance Basin Geology ...................................................................... 61 5.2 Piceance Basin Population Density ...................................................... 62 5.3 Piceance Basin Water Sourcing ........................................................... 62 5.4 Piceance Basin Data Sourcing and Assumptions ................................ 64 5.5 Piceance Basin Historical Wellbore Barrier Designs ............................ 65 5.6 Piceance Basin Wellbore Barrier Categories ....................................... 69 5.7 Piceance Basin Potential Barrier Failures ............................................ 79 5.8 Piceance Basin Catastrophic Barrier Failure Overview ........................ 83 5.9 Piceance Basin Catastrophic Barrier Failures ...................................... 84 5.10 Piceance Basin Existing Conditions ..................................................... 87 CHAPTER 6 RISK ASSESSMENT OF OIL AND GAS WELLS IN THE RATON BASIN, COLORADO .............................................................. 90 6.1 Raton Basin Geology ........................................................................... 91 6.2 Raton Basin Population Density ........................................................... 92 6.3 Raton Basin Water Sourcing ................................................................ 93 6.4 Raton Basin Data Sourcing and Assumptions...................................... 94 6.5 Raton Basin Historical Wellbore Designs ............................................. 95 6.6 Raton Basin Wellbore Barrier Categories .......................................... 101 6.7 Raton Basin Potential Barrier Failures ............................................... 111 6.8 Raton Basin Catastrophic Barrier Failure Overview ........................... 113 6.9 Raton Basin Catastrophic Barrier Failures ......................................... 115 6.10 Raton Basin Existing Conditions ........................................................ 118 v CHAPTER 7 RISK ASSESSMENT OF OIL AND GAS WELLS IN THE SAN JUAN BASIN, COLORADO ....................................................... 121 7.1 San Juan Basin Geology .................................................................... 122 7.2 San Juan Basin Population Density ................................................... 123 7.3 San Juan Basin Water Sourcing ........................................................ 124 7.4 San Juan Basin Data Sourcing and Assumptions .............................. 125 7.5 San Juan Basin Historical Wellbore Designs ..................................... 126 7.6 San Juan Basin Wellbore Barrier Categories ..................................... 132 7.7 San Juan Basin Potential Barrier Failures .......................................... 143 7.8 San Juan Basin Catastrophic Barrier Failure Overview ..................... 146 7.9 San Juan Basin Catastrophic Barrier Failures .................................... 148 7.10 San Juan Basin Existing Conditions ................................................... 150 CHAPTER 8 CONCLUSIONS ................................................................................. 152 8.1 Further Research Recommendations ................................................ 156 REFERENCES ........................................................................................................... 157 vi LIST OF FIGURES Figure 1.1 Geographic locations of oil and gas basins in the State of Colorado ................................................................................................... 2 Figure 1.2 Wellbore barrier categories that are ranked from highest risk to lowest risk ................................................................................................. 5 Figure 1.3 Example of a high risk wellbore barrier design ......................................... 6 Figure 1.4 Example of a low risk wellbore barrier design ........................................... 7 Figure 2.1 Typical composition of hydraulic fracturing fluids and their common uses in commercial products .................................................................. 13 Figure 4.1 Geographic location of the Wattenberg Field, Colorado ......................... 20 Figure 4.2 Geologic stratigraphic units of the Denver-Julesburg Basin, Wattenberg Field, Colorado .................................................................... 22 Figure 4.3 Population of Weld County, Colorado from 1970 to 2013 ....................... 23 Figure 4.4 Population of Adams County, Colorado from 1970 to 2013 .................... 24 Figure 4.5 Population of Boulder County, Colorado from 1970 to 2013 ................... 25 Figure 4.6 Population of Larimer County, Colorado from 1970 to 2013 ................... 25 Figure 4.7 Cross section of the