Abstract
Abstract
The Barnett Shale play of the Ft. Worth Basin has sparked considerable investment in the Woodford, Fayetteville, Haynesville, and Marcellus Shales, as well as in other shale plays. Key to developing these unconventional natural gas resources is the management of water and other environmental issues facing the developers active in these plays including water availability, water handling/transport, hydraulic fracturing and management of fracturing fluids, water disposal, urban drilling, NORM, and other environmental considerations. This paper will discuss these environmental considerations and challenges related to modern shale gas development in several major plays within the United States, as well as the potential impacts of the expanding public concern regarding shale gas development, and practices and solutions implemented to facilitate ongoing development.
Introduction
Natural Gas Basics.
Natural gas is an odorless, colorless mixture of light-end, flammable hydrocarbons primarily composed of methane (CH4),1 but also containing lesser percentages of butane, ethane, propane, and other gases. When combusted, natural gas releases significant amounts of energy, while emitting less carbon and other constituents to the atmosphere than other fossil fuel sources.2,3
Extracted from rock formations (reservoirs) beneath the earth's surface and in some cases associated with oil deposits, natural gas usually requires processing to eliminate other gases, water, sand, and impurities before it can be distributed and utilized commercially. Some hydrocarbon gases, such as butane and propane (referred to as natural gas liquids), are captured during the processing and marketed separately. Natural gas is distributed through a system of pipelines across thousands of miles4 to its endpoints for residential, commercial, industrial, and transportation use.
Eighty-four percent of the natural gas consumed in the U.S. is produced here, and 98 percent is produced in North America.5 Thus, the supply of natural gas for the United States is not dependent on unstable foreign countries and the delivery system is less subject to interruption.
The Role of Natural Gas in the United States' Energy Portfolio.
Natural gas plays a key role in meeting U.S. energy demands. Natural gas, coal and oil supply about 85 percent of the nation's energy (See Figure 16), with natural gas supplying about 22 percent of the total.7 Currently, it is estimated that the U.S. has 1,744 tcf (trillion cubic feet) of technically recoverable natural gas, including 211 tcf of proven reserves (reserves are the discovered, economically recoverable fraction of the original gas-in-place).8,9 Given that one tcf is one trillion cubic feet, the proven reserves alone could provide heating energy to 3.06 billion homes, generate 2.04 trillion kilowatt-hours of electricity, or fuel 2.53 billion natural gas-powered vehicles for one year.10 Maintaining U.S. production rates of 2008, the current reserve estimate would take 82 years to fully produce.11