Hydraulic Fracturing, or Hydro-Fracking
Oil and gas reserves that were once considered inaccessible are now available to be exploited, due to the development of hydraulic fracturing, or hydro-fracking, a multi-step extraction process in which fossil fuel-bearing rock formations are drilled and fractured using high volumes of water and associated processes. The hydro-fracking process has both expanded oil and gas development and significant environmental and societal water resources management and environmental risks. These risks, however, are currently the subject of the Earth Sustaining Sciences Group’s economic, environmental and societal all-natural process solutions design and delivery completion. Hydraulic fracturing, or hydro-fracking, describes a multi-step oil and natural gas extraction process in which the fossil fuel-bearing rock formations are both vertically and horizontally directionally drilled. Once the well is drilled, a charge is detonated to blast fissures open, then a proprietary mix of water, chemicals and proppants are injected into underground rock layers at high pressure in order to further fracture the rock and keep the fissures open. Once the production well is fully open, some “produced” wastewater flows back to the surface, and finally, the oil and natural gas is extracted. Vital to the hydro-fracking process are the millions of gallons of fracking fluid required for each well; a fluid made up of more than 90 percent water. While each company’s hydro-fracking process formula is often a closely guarded secret, a review of the recognized 1,021 chemicals in these various proprietary mixes are known to include surfactants, biocides, volatile organic compounds and carcinogens. As hydro- fracking has become more widespread the proximity to major population centres has raised significant public health concerns as evidenced by conflict over development in the Marcellus Shale in the Northeastern United States for example. Of primary concern is the potentially damaging impact on water reserves, natural resources and ecologies.
Concern about the impact of hydro-fracking’s significant water use on local water resources as well the potential for resultant pollution has led to a number of studies. Two such recent recent studies from Duke University assessed the water footprint of each step and the full life cycle of the hydro-fracking process. The first study evaluated the median water use of six basins for shale-gas and shale oil and found that shale-gas water use ranged from 390 thousand to 6.27 million gallons per well, while shale-oil use ranged from 70 thousand to 2 million gallons of water per well. Following the hydro-fracturing process, a percentage of the water returns fairly quickly to the surface as wastewater, or “flow-back.” The saline effluent called “produced water,” that has long been underground and progressively returns to the surface during continued operation of the well, can contain naturally occurring contaminants like the radioactive elements (radium), other heavy metals, complex organics and salts. The volume of this toxic wastewater must be collected and stored, then treated and environmentally discharged or re-injected into deep disposal wells. This wastewater is often pumped into holding ponds where it can leech and settle unfavourably into surrounding environments. Environmental and groundwater contamination is of major concern, especially given the criticality of aquifers.
Water Volumes Produced in Hydro-Fracking
There isn’t really a typical hydraulically fractured well because the amount of water used depends on the rock formation, the operator, whether the well is vertical or horizontal, and the number of portions (or stages) of the well that are fractured. In addition, some water is recycled from fluids produced by the well, so the net consumption might be smaller at sites that recycle. Water use per well can be anywhere from about 1.5 million gallons to about 16 million gallons. Examples of Researched Average Reported Hydraulic Fracturing Water Usage Per Well Include:
- Marcellus Shale, Pennsylvania, 4.5 million gallons (Risser, 2012, USGS Public Lecture, Shale gas, Hydraulic Fracturing, and Induced Earthquakes)
- Wattenburg Sandstone, Colorado, 2.7 million gallons (Goodwin and others, 2012, Oil and Gas Journal)
- Barnett Shale, Texas, 2.8 million gallons (Nicot and Scanlon, 2012, Environmental Science and Technology)
- Eagle Ford Shale, Texas, 4.3 million gallons (Nicot and Scanlon, 2012, Environmental Science and Technology)
- Haynesville Shale, Texas, 5.7 million gallons (Nicot and Scanlon, 2012, Environmental Science and Technology)
- Bakken Formation, North Dakota, 1.5 million gallons (S. Haines, 2012, USGS personal communication)
- Horn River Shale, British Columbia, Canada, 15.8 million gallons (Horn River Basin Producers Group, 2010).
Oil and Gas Produced Water
The process of oil and gas production creates a saltwater effluent, which is considered hazardous waste that is further contaminated with hydrocarbons, complex organics and industrial compounds. Hydraulic fracturing of shale gas/oil well sites produces millions of gallons of this contaminant laden saltwater, also known as produced water or oilfield brine. The water brings oil and gas to the earth's surface where impurities are chemically removed, resulting in leftover liquor that must then be treated and safely re-used or discarded. Usually, currently, companies can recycle the produced water, albeit at often excessive cost, injecting it back into working reservoirs for reuse in gathering any remaining oil or gas, or they can discard it at a saltwater well disposal site. Placement of these high-pressure disposal sites can be a controversial issue because of the potential for groundwater contamination and small earthquakes.
Saltwater Disposal Well Construction
Current common practice describes a saltwater disposal well as a bored, drilled, or driven shaft whose depth is greater than the largest surface dimension; or, a dug hole whose depth is greater than the largest surface dimension; or, an improved sinkhole; or, a subsurface fluid distribution system. Widely used since the 1930s, saltwater disposal wells contain the water with the intent it will not contaminate land or water resources. Initially, the saltwater was largely disposed of in surface waters, but moved to being contained in deeper wells in the 1950s. They're mighty fortresses designed with the intent to spare the environment the effects of gas and oil production. Many jurisdictions require wells intended to contain disposed carbon dioxide or other hazardous wastes be constructed of as many as three layers. The first outer layer extends as deep into the ground as necessary to protect area groundwater. It's typically constructed of steel pipe and cement. Another layer covers the entire well, and a third encloses the injection device. This triple-layer system means all three protective coverings must be breached before contamination of surrounding groundwater can occur.