What is Hydraulic Fracturing?
Hydraulic fracturing involves injecting fluid under controlled pressure intermittently over a short period (three to five days) to create fractures in a targeted rock formation permitting oil or natural gas to flow to the wellbore.
Hydraulic fracturing is essential to produce oil and natural gas that is otherwise trapped in low-permeability rock formations. It significantly improves the recovery from the reservoir by stimulating the movement of oil and natural gas.
It is important to understand where hydraulic fracturing fits within the entire drilling, well construction/completion and production cycle of oil and natural gas activities. Hydraulic fracturing is not a method for drilling or constructing a well.
To reach a hydrocarbon formation – thousands of feet below the surface and freshwater resources – a hole (wellbore) is drilled in successive sections through the rock layers. Once the desired length of each wellbore section has been drilled, the drilling assembly is removed and steel casing is inserted and cemented in place. As the well is constructed, concentric layers of steel casing and cement form the barrier between potential groundwater resources and the hydrocarbons that will later flow inside the well. Next, only the section of casing within the hydrocarbon formation is perforated at the desired location.
The well is now ready for the hydraulic fracturing process. As previously mentioned, this process involves pumping fluid through the perforations. The fracturing fluid exerts pressure against the rock, creating tiny cracks, or fractures, in the reservoir deep underground. The fluid is predominantly water, proppants (grains of sand or ceramic particles) and a small fraction of chemical additives.
Once fluid injection stops, pressure begins to dissipate, and the fractures previously held open by the fluid pressure begin to close. Proppants then act as tiny wedges to hold open these narrow fractures creating pathways for oil, natural gas and fracturing fluids to flow more easily to the well. A plug is set inside the casing to isolate the stimulated section of the well. The entire perforate-inject-plug cycle is then repeated at regular intervals along the casing within the targeted section of the reservoir. Finally, the plugs are drilled out, allowing the oil, natural gas and fluids to flow into the well casing and up to the surface.
The hydrocarbon and fracturing fluid mixture is separated at the surface, and the fracturing fluid (also known as flowback water) is collected in tanks or lined pits. The fracturing fluids are then disposed of according to government-approved methods.
Hydraulic fracturing operations generally occur over a three- to five-day period. The entire well construction process (including hydraulic fracturing) takes about two or three months, compared to the 20- to 30-year productive life of a typical well.
To learn more about the drilling and hydraulic fractuing process, watch this video.
Why is Hydraulic Fracturing Important?
Since the late 1940s more than one million wells have been hydraulically fractured in the United States, and more than two million have been hydraulically fractured worldwide. When used in conjunction with horizontal drilling – an advanced drilling technology – hydraulic fracturing has made it possible to develop vast unconventional resources, including tight sands, coalbed methane and shale gas. According to the U.S. Energy Information Administration, these combined resources accounted for 50 percent of U.S. natural gas production in 2009 and are projected to account for 60 percent of supply by 2035.
Is Hydraulic Fracturing Safe?
Hydraulic fracturing is a safe and proven technique that has helped develop oil and natural gas resources safely for more than 60 years. According to the National Petroleum Council, "95 percent of oil and gas wells drilled today are hydraulically fractured". Many studies – and decades of history – indicate that oil and natural gas operations, including hydraulic fracturing, are safe when wells are properly designed, constructed and operated.
Recent studies have found no substantiated connection between hydraulic fracturing and groundwater contamination:
- A 2004 Environmental Protection Agency study of fracturing in coalbed methane reservoirs found "little or no threat" to underground sources of drinking water. Hydraulic fracturing continues to be studied by the EPA.
- A 2009 study by the Ground Water Protection Council, an association of state regulators, reviewed 10,000 wells and found only one water complaint, which proved to be unrelated to hydraulic fracturing.
- In 2010, the Interstate Oil & Gas Compact Commission, which represents 30 state governments, confirmed that there have been no verified cases of drinking water contamination resulting from hydraulic fracturing operations in states where shale gas is produced.
- A 2012 University of Texas Energy Institute study found "no evidence of aquifer contamination from hydraulic fracturing in the subsurface by fracturing operations, and observed no leakage from hydraulic fracturing at depth.”
Discover how groundwater is protected through every stage of oil and natural gas development; here.