Hydraulic fracturing is a process in the development of oil and natural gas resources that involves using water under carefully controlled conditions to crack, or fracture, part of a layer of solid rock thousands of feet below the surface. Although it is a common process used in oil and gas development for decades, its importance in freeing up resources previously overlooked is a primary reason for the remarkable expansion of American energy supplies.
Why hydraulic fracturing is needed
Conventional oil and natural gas development has been practiced around the world for more than 150 years. A conventional well is drilled into a reservoir of oil or gas trapped within porous or fractured rock by an overlying formation of impermeable rock. Think of a wet sponge under a concrete sidewalk. Drilling a hole straight through the sidewalk allows the fluid in the sponge to move to the surface. Conventional oil and gas reservoirs are becoming increasingly scarce and tapping them from offshore platforms or remote, difficult to access locations is now more expensive and often carries political risk.
Unconventional oil and gas development, which includes shale oil, heavy-oil sands and tight oil, is considered more expensive than conventional oil and gas. And while rock formations such as the Eagle Ford and Barnett in Texas, the Marcellus in Pennsylvania, and the Bakken in North Dakota have long been known to hold oil and gas, the key to unlocking them from the confines of their rock containers was only recently uncovered.
Without the ability to create, and hold open tiny cracks or fractures in the rock, the oil and gas in these formations cannot be tapped. Hydraulic fracturing provides that ability.
How is a well hydraulically fractured?
By the late 1990s, modern horizontal drilling techniques were being combined with new hydraulic fracturing processes to complete wells that went thousands of feet down and additional thousands of feet out through a layer of shale or other hard rock formation that might be just 50 feet thick.
Depending on the type of completion, the hydraulic fracturing process usually includes portable storage tanks or a water impoundment for the millions of gallons of water needed plus several tons of sand and a relatively small amount of specialized chemicals. Each fracturing project requires a dozen or so workers, advanced control equipment and the assistance of specialist service companies.
To fracture a well, water, sand and trace amounts of chemicals are pumped under high pressure down the wellbore causing tiny cracks in the rock formation. Once the pressure is relieved, some sand remains to prop open the small cracks and allow oil and gas to flow into the wellbore for recovery at the surface.
Concerns have been raised about the chemicals used in hydraulic fracturing. First, the well is isolated from the surrounding rock to prevent oil, gas and fracturing fluids from reaching groundwater. During the drilling process, the wellbore it is lined with concentric layers of cement and steel pipe. Once the well casing is in place, it is tested to make sure the seal is tight. Such testing is one of many regulations applied to oil and gas development to protect the environment.
Although a variety of specialized chemicals are combined to create fracturing fluid depending on the characteristics of the rock, there are a limited number of purposes for which these chemicals are used. Generally, acids are used to scrub the rock face before fracturing, biocides are added to prevent bacteria build-up in the water, corrosion inhibitors prevent rust formation, friction reducers help the fluid move more freely, gels hold the sand in suspension and breakers dissolve the gels after the rock is fractured and allow the fluid to flow back to the surface.
Since 2011, FracFocus, a national registry for hydraulic fracturing, has managed a database for disclosure of chemicals used during hydraulic fracturing. There are currently 16 states that require companies to disclose on FracFocus information about the chemicals used on each well.
What specialized services are needed in hydraulic fracturing?
During a hydraulic fracturing operation, specialized services are needed. These may include water and materials hauling, heavy equipment, water logistics and frac water heating.
Frac water heating and frac fluids heating services in general are necessary in colder climates to prevent water from freezing, to maintain proper downhole tubular temperatures, and to meet the specifications of some cross-linked gel fluid formulas. Frac water heating service is a crucial part of many hydraulic fracturing operations. Providers of frac fluids heating services are contracted to provide flexible, efficient solutions to the variety of challenges operators face with every new job.
What is the difference between fracing and fracking?
The term hydraulic fracturing describes when water is used to create small cracks in the rock surrounding a wellbore. The industry uses the term to fracing or frac’ing as an abbreviation. About ten years ago, conservation and environmental organizations seized on the term and spelled it fracking to describe what they saw as a potential hazard and possible threat to health and the environment from oil and gas development.
In the years since, fracking has become a catch-all to describe and to malign the entire oil and gas development and production process. Even the resource itself, for example, is sometimes referred to as “fracking gas” even though natural gas produced from a tight formation is no different from gas produced from a conventional well. This spelling and its connotation have become so widely accepted that the term fracking was added to the Merriam-Webster dictionary in May.
Earlier, the industry-supported education program Coloradans for Responsible Energy Development (CRED) acknowledged that the term fracking is more widely found in Google searches than when searching for fracing. It made the change to fracking because: “We felt our time was better spent educating Coloradans on the issue, not arguing about whether or not to include the “k.”
FracFocus, fracing process: http://fracfocus.org/hydraulic-fracturing-process
FracFocus, what chemicals: http://fracfocus.org/chemical-use/what-chemicals-are-used
FracFocus, chemical use in fracking: http://fracfocus.org/water-protection/drilling-usage
FracFocus, chemicals & public disclosure: http://fracfocus.org/chemical-use/chemicals-public-disclosure
FracFocus, find a well page: http://www.fracfocusdata.org/DisclosureSearch/
EPA fracturing page: http://www2.epa.gov/hydraulicfracturing
CU-Boulder, Glossary: http://airwatergas.org/public-resources/glossary
HCN article, War of Words: http://www.hcn.org/articles/war-of-the-words
NPR article, Spell Fracking: http://www.npr.org/2014/05/28/316552595/no-matter-how-you-spell-it-fracking-stirs-controversy
FuelFix article: fracing or fracking: http://fuelfix.com/blog/2011/12/23/is-it-fracking-or-fracing/
Dept. of Energy study on gas migration in Marcellus well: http://www.netl.doe.gov/File%20Library/Research/onsite%20research/publications/NETL-TRS-3-2014_Greene-County-Site_20140915_1_1.pdf
Energy in Depth, chemicals in fracturing fluid: http://energyindepth.org/docs/frac-fluid.pdf
Energy in Depth, well casing fact vs. myths: http://energyindepth.org/wp-content/uploads/2014/06/well-casing-failure.pdf
Penn State University, hydraulic fracturing water not a risk to groundwater: http://news.psu.edu/story/325692/2014/09/10/research/residual-hydraulic-fracturing-water-not-risk-groundwater
Halliburton, fluids disclosure page: http://www.halliburton.com/public/projects/pubsdata/hydraulic_fracturing/fluids_disclosure.html
CRED faq: where did the term fracking come from? http://studyfracking.com/faq/#faq-70
CRED round-up of fracturing research: http://studyfracking.com/research/
Image: Chesapeake illustration of hydraulic fracturing process: http://www.chk.com/Media/Educational-Library/Illustrations/Illustrations/Hydraulic_Fracturing.pdf