Recent exploitation of shale to extract gas and oil has resulted in a boom of drilling and hydraulic fracturing across the United States. The U.S. Energy Information Administration has mapped the primary shale gas basins in the United States as shown in the accompanying figure. None are in Arizona.
Controversy involving the shale gas boom
Vast numbers of wells are being drilled and fractured in shale formations that extend over thousands of square miles across multiple states. In some cases this creates conflict with surface uses such as agriculture and grazing and disturbance of watersheds that provide drinking water. Most wells drilled for shale gas are drilled vertically to much deeper than freshwater aquifers, then angled to horizontal to penetrate and fracture as much of the productive shale formation as possible. The accompanying schematic depicts a typical well drilled first vertically then horizontally for shale gas.
The sheer number of wells being drilled and fractured has created controversy about contamination of groundwater even though the fractured horizontal segment of most shale-gas wells is much deeper than freshwater aquifers. In some areas the construction of many well pads and access roads and increased truck traffic to complete the hydraulic fracturing process could result in significant surface disturbance and adversely impact surface watersheds. Significant surface-disturbance activities also concern agriculture and grazing users. The controversy surrounding the shale gas boom involves land owners, lessees of surface rights such as agriculture and grazing, oil and gas companies, conservation groups, regulatory agencies and film makers. The movie Gasland released in 2010 by Josh Fox dramatically expresses the controversy. Gasland describes several individuals and communities that claim to be adversely impacted by the drilling and fracturing boom.
What is hydraulic fracturing?
Hydraulic fracturing is a relatively short-term activity that stimulates the flow of gas and oil (hydrocarbon production) from deep shale formations that do not naturally allow fluids to flow through them. These tight shale formations are the target of the drilling and fracturing boom. The fracturing process involves pumping a mixture of about 99 percent water and sand plus a minor amount of additional chemicals into a well at a pressure high enough to crack or fracture the tight shale formation of interest. The chemicals used and their purpose is reported at FracFocus, the hydraulic fracturing chemical registry website (http://fracfocus.org/). Once created, the sand-packed fractures open pathways that allow oil or gas to move or migrate from the tight formation to the well. The watery fluid is recovered from the fractures shortly after being pumped into the well. This is done slowly enough to allow the geologic formation to compress against and prevent the sand from flowing back out of the fractures with the watery fluid. The sand remains in the fractures and props them open. That is why the sand or similar granular substance such as walnut shells or ceramic particles is often called a propping agent or “proppant.”
Partly because of the short-term duration of the hydraulic fracturing process to stimulate production in oil and gas wells, the Energy Policy Act of 2005 (EPACT) Section 322 excludes from the Safe Drinking Water Act the underground injection of fluids or propping agents, other than diesel fuels, used in hydraulic fracturing related to oil, gas, or geothermal production activities. EPACT does not exclude wells used in relatively long term activities to dispose of fluids associated with the production of oil and gas, to inject fluids for enhanced oil recovery, or for wells used for the storage of liquid hydrocarbons.
Hydraulic fracturing is regulated in Arizona
The Arizona Oil and Gas Conservation Commission (AZOGCC) has received several inquiries over the past few years regarding shale gas drilling and hydraulic fracturing in Arizona. A common concern is environmental damage due to hydraulic fracturing. Hydraulic fracturing is rarely used in Arizona and thus is not a threat. There are no shale-gas wells in Arizona and there has been no horizontal drilling and no hydraulic fracturing associated with those types of wells. In fact no wells have ever been drilled in Arizona for shale-gas. The geology of Arizona does not include the extensive areas of the type of shale formation that shale-gas developers are looking for.
Only ten wells have been hydraulically fractured in Arizona in the last 15 years. Seven were fractured in 1997, one in 2004 and two in 2008. All of the wells were drilled for carbon dioxide gas, not shale gas, in east-central Arizona between St Johns and Springerville.
The AZOGCC has rules to ensure that fracturing oil and gas wells is done safely and does not contaminate groundwater or surface resources. Permission is not required in advance of fracturing but an operator is required to report hydraulic fracturing activities to the AZOGCC in writing showing the type of stimulation, the amounts and types of materials used, pressures applied, and the flow and pressure results before and after stimulation. An operator is also required to immediately notify the AZOGCC if the stimulation of a well results in any damage to the producing formation, to a freshwater formation, or to a well casing, or casing seat if this damage permits fluid communication between fluid-bearing zones. The well operator must then proceed with diligence to correct the damage. The operator must also properly plug and abandon the well if the stimulation results in irreparable damage to the well.
Useful references about hydraulic fracturing
http://fracfocus.org/: FracFocus is the hydraulic fracturing chemical registry website. It is a joint project of the Groundwater Protection Council and the Interstate Oil and Gas Compact Commission. On this website you can search for well sites that have been hydraulically fractured to see what chemicals were used in the process.
http://www.iogcc.state.ok.us/: The IOGCC is the Interstate Oil and Gas Compact Commission. On this website you will find useful information and many informative presentations about hydraulic fracturing.
http://www.eia.gov/energy_in_brief/about_shale_gas.cfm: The U.S. Department of Energy Energy Information Agency. On this website you will find useful information about what is shale gas and why is it important.
http://www.ngwa.org/Media-Center/press/2012/Pages/2012-01-31-hydraulic-fracturing.aspx: The National Groundwater Association. On this website you will find hydraulic fracturing guidance offered to policy makers by the National Groundwater Association.
http://www.kgs.ku.edu/Publications/PIC/pic32.html: The Kansas Geological Survey. On this website you will find useful information to explain hydraulic fracturing in Kansas including several informative diagrams and photographs.
http://energy.utexas.edu/: University of Texas at Austin Energy Institute. On this website you will find documents assessing the real and perceived consequences of shale gas development.