Shale gas: Hydraulic fracturing and environmental issues

Hydraulic fracturing ("fracking") is a well completion technique designed to improve oil and gas production. The process involves injecting large volumes of fluids and proppants—small spheroids of solid material—at high pressure to create fractures in the source rock and carry the proppants into the fractures to hold them open when production commences. The hydraulic fracturing fluid is typically water-based and contains various chemicals, including bactericides, buffers, stabilizers, fluid-loss additives, and surfactants, to promote the effectiveness of the fracturing operation and prevent damage to the formation. Without hydraulic fracturing, shale deposits would not produce natural gas, and most low-permeability deposits would be uneconomical. It is estimated that hydraulic fracturing is used for more than 50 percent of the natural gas wells currently drilled each year in the United States. In 2010, shale and low-permeability reservoirs accounted for about 52 percent of U.S. natural gas production and about 46 percent of total consumption [97].

Concerns about the extensive use of hydraulic fracturing have been raised by the public in the United States and elsewhere in the world because of the large volumes of water required, the chemicals added to fracturing fluids, and the need to dispose of the fluids after wells have been completed. A principal concern is the potential for contamination of aquifers and ground water, either from wells passing through aquifers or from surface spills. Other environmental concerns range from air emissions and noise pollution to surface impacts (such as increased truck traffic and road damage), infrastructure considerations (such as roads, pipelines, and water treatment facilities), and public disclosure of the chemical makeup of fracking fluids.

Studies are underway to assess specific environmental concerns. The U.S. Environmental Protection Agency (EPA) is developing a study to examine the relationship between hydraulic fracturing and drinking water resources [98]. The scope of the proposed research includes study of the full life cycle of fracking water, from its acquisition to the mixing of chemicals to the fracturing and post-fracturing stages, including management of flowback and produced water and the ultimate treatment and/or disposal of the water recovered. In early 2011, the EPA submitted its draft study plan on hydraulic fracturing for review by the agency's Science Advisory Board (SAB). Initial research results are expected by the end of 2012, and a final report is expected in 2014. In addition, environmental issues related to shale gas are being addressed in public hearings on the safety of shale gas development, held by the U.S. Secretary of Energy Advisory Board [99].

It is too early to tell whether environmental concerns will result in any long-term restrictions that significantly impede application of hydraulic fracturing techniques. Every country with an interest in developing its shale gas resources will develop its own policies to address such concerns, and the resulting framework could influence the pace of shale gas development around the world.