Rapid growth of the shale gas industry has triggered concerns about the industrial practices used to extract natural gas trapped in shale rock formations below the earth’s surface. Shale drilling practices can impact vital natural resources, including air and water quality.
Shale gas operators can prevent or lessen impact of shale gas drilling and related industry activities on air and water by following best management practices.
Control dust and prevent escaping gas
To control airborne dust raised by construction and traffic, operators are encouraged or required to apply chemical dust suppressants or water to unpaved roads and other bare soil surfaces. This is required in many areas where property is under the administration of the Bureau of Land Management.
To control release of greenhouse gases, particularly methane, the dominant ingredient of natural gas, many producers are installing recovery equipment to capture and recycle gas vented from tanks, pipelines and processing plants. Reducing fugitive methane is a pivotal step that can be economically and realistically achieved with current technology. Using electric equipment for compressors and other in the field, rather than diesel equipment, also produces many air quality benefits. Reducing and reusing waste heat to improve thermal energy efficiency can also offer cost and environmental benefits as well.
Monitor for leaks and follow regulations
Leaks, a source of “fugitive” emissions, can be minimized through regular inspections of valves, connectors, and open lines with detection technologies such as infrared imaging. Detection methods can also reduce amounts of surplus gas that would otherwise be “flared,” or burned off at well sites. Methane, the primary component of natural gas, is a valuable commodity and preventing its escape offers economic benefits to the site operator.
Further best management practices include strict compliance with the numerous clean air regulations enacted by federal, state and local jurisdictions. The federal Environmental Protection Agency’s New Source Review requires a permit for a new plant or plant modification if it will increase air pollution emissions by a large amount. The permit requires that operators minimize air pollution by installing emission control equipment.
In addition to the federal and state air-quality requirements, some city, county and regional air-quality oversight entities are now being established to deal with possible exceedances of air quality standards.
Preserve water quality with casing and cementing
One of the fundamental best practices for protecting groundwater during hydraulic fracturing is casing and cementing of natural gas wells. Casing and cementing ensures that neither the fracking fluid pumped through the well, nor the gas that will eventually be collected, enters the water supply.
As the wellbore is drilled, casings from large diameter to smaller are inserted into the well to depths of between 1,000 and 4,000 feet. The space between these casing “strings” and the drilled hole (wellbore), called the annulus, is filled with cement. Once the cement has set, then the drilling continues from the bottom of the surface or intermediate cemented steel casing to the next depth. This process is repeated, using smaller steel casing each time, until the gas-bearing reservoir is reached (generally 6,000 to 10,000 ft). All states have standards for this process.
A more detailed look at casing and its role in groundwater protection is available on the FracFocus website, a joint project of the Ground Water Protection Council and the Interstate Oil and Gas Compact Commission, which offers information about the chemicals used in the hydraulic fracturing of oil and gas wells and other materials.
Pursue "green" practices and water recycling
A “green frac” best practice has been developed jointly by residents and operators in at least one community in Colorado. “Green frac” fluid is defined as water and other materials that are “biodegradable, non-toxic neutral pH, residual free, non-corrosive, non-polluting and nonhazardous in the forms and concentrations being used,” and “are not known carcinogens in the methods or concentrations being used.” Further, a study by an energy research institute and several operating companies suggests that “wells fractured with water produced more gas and cost considerably less to fracture than wells fractured with a gel comprised of chemicals.”
Rather than storing used fracking fluid in deep injection wells, an alternative best practice is recycling or reusing used drilling fluid, which is mostly water. In Arkansas, a switch from injection wells to recycling was driven literally by earth-shaking occurrences. The water stored in nearby injection wells induced earthquakes. Another driver for recycling in some regions is the continuing effects of the great drought of summer 2011, which left many water-supply lakes and reservoirs at dramatically low levels.
As in most matters related to energy production, compliance with regulations, as well as application of reasonable and prudent practices, is fundamental. Specifically, regarding storm water, the Independent Petroleum Association of America encourages operators to apply reasonable and prudent practices to control erosion and sedimentation around oil and gas construction sites and to consider federal, state or local regulatory requirements to achieve compliance with associated regulations.
Protecting water from contamination caused by potential leaks of fracking fluids is addressed in several best practices: avoid constructing reserve pits in areas of shallow groundwater; avoid operations in stream areas, floodplains, and wetlands; confine fracturing fluids and condensates in lined pits or tanks.