The Basics: Hydraulic Fracturing

Hydraulic fracturing is the process of creating small fissures, or fractures, in underground geological formations to allow natural gas and oil to flow into a wellbore and up to the surface where it is collected and prepared. It is part of the final stages of the overall drilling procedure, called the completion phase. It occurs thousands of feet—often more than a mile—below ground surface and groundwater aquifers, separated by multiple layers of impermeable rock or shale. Hydraulic fracturing is critical to the development of unconventional oil and gas reservoirs that would otherwise be uneconomical. Unlike conventional reservoirs that will produce oil and gas solely from drilling a well, unconventional plays require stimulation to unlock the oil and gas that is in the rock itself. In fact, over 90% of the wells drilled today are hydraulically-fractured. Unconventional natural gas and oil reserves are constantly being discovered and developed which has vastly increased our domestic reserves. As with any phase of oil and gas drilling, Colorado has a robust regulatory structure, to which all operators must adhere, and hydraulic fracturing is no different. Before the hydraulic fracturing process begins, a robust Colorado regulatory framework requires all wellbores to be lined with three types of casing: Conductor casing, surface casing, and production casing. By Colorado regulations, the production casing on all wells is required to be verified by a specialized well survey (cement bond log). The entire wellbore’s construction is also tested at pressures greater than that calculated to occur during the fracturing treatment itself, to ensure the finished wellbore’s integrity. After wellbore testing, hydraulic fracturing begins with a mechanical perforation of the casing thousands of feet below the surface, into the oil and gas producing zone. Once the perforations are complete, hydraulic pumps and blending equipment pressurize a mixture of water, sand, and other chemical additives into the shale formation to create small fractures. The mixture is approximately 99.5% water and sand, along with a small amount of special-purpose hydraulic fracturing additives. The water pressure is reduced and fluids are carried up the wellbore for disposal or treatment and re-use, leaving the sand in place. The newly created fractures are “propped” open by the sand, which allows natural gas and oil to flow into the wellbore where it is collected at the surface. Experts continually monitor and gauge pressures, fluids, and proppant levels. This process may be repeated in stages to reach the entire length of the wellbore. When these stages are complete, the well is tested for results. When used properly, hydraulic fracturing chemicals are no more dangerous than any industrial or household chemicals. They do require safe work practices, proper site preparation, and attentive handling to ensure safety and the protection of the public, employees, contractors, and the environment. It is important to note that deep natural gas and oil shale drilling operations target hydraulic fracturing zones that are, on average, located almost 1.5 miles below the earth’s surface and many thousands of feet below freshwater formations, and are separated by thousands of feet and the immense weight of tons of protective rock barriers. These depths and formations make the potential for migration into freshwater zones a near scientific impossibility. Colorado has some of the most comprehensive oil and gas regulations in the country. Every aspect of oil and gas activity is regulated, including site selection, permitting, down-hole activities, hydraulic fracturing, groundwater protection, and final site reclamation. Colorado’s hydraulic fracturing rule is one of the strongest in the country because it requires public disclosure of all hydraulically fractured treatments performed. Disclosure includes hydraulic fracturing chemicals, concentrations, and the volume of water used. View this information at FracFocus.org, a national hydraulic fracturing chemical disclosure registry created the Ground Water Protection Council and the Interstate Oil and Gas Compact Commission.