Steps to Safety
There are stringent standards, procedures and regulations in place to ensure the safety of natural gas production using hydraulic fracturing based on nearly a century of experience in oil and natural gas drilling.
American Petroleum Institute (API) standards documents detail procedures that should take place before, during and after the hydraulic fracturing process. These steps include site preparation, drilling the well; running and cementing the steel casing through which the fluids and gas will travel; the hydraulic fracturing process itself; and the testing and monitoring.
The objective of these standards is safety. For example, API HF1, Hydraulic Fracturing Operations—Well Construction and Integrity Guidelines, describes well construction and hydraulic fracturing. In this document API states "The ultimate goal of the well design is to ensure the environmentally sound, safe production of hydrocarbons by containing them inside the well, protecting groundwater resources, isolating the productive formations from other formations, and by proper execution of hydraulic fractures and other stimulation operations."
Once a drilling site has been selected, production teams prepare the site by constructing access roads and the well location, and installing and testing all equipment such as the drilling rig, fluid handling equipment, water tanks and other ancillary equipment. API standards provide environmentally sound practices for the selection, design and construction of roads and well locations, including factors such as erosion, wildlife, waste management, water discharge, and waste disposal. Standards also guide comprehensive plans such as equipment operations and maintenance, fluid management, spill contingency, and land reclamation and cleanup.
Drilling and Well Construction
After the drilling site is constructed and all equipment has been tested, the well is ready to be drilled. Wells are typically drilled to vertical depths of 5,000 to 8,000 feet, and often combined with horizontal drilling to extend the length of the wellbore another few thousand feet. In either case, the fracturing process takes place thousands of feet below the underground water aquifer, as depicted below.
Multiple layers of well casings and cement are installed to create the infrastructure through which the hydraulic fracturing fluids and natural gas will flow. Casing and cementing are critical parts of the well construction that protect water and hydrocarbon bearing zones. Upon drilling the well (below), steel pipe known as surface casing is cemented into place at the uppermost portion of a well to protect the groundwater. As the well is drilled deeper, additional casing is installed to isolate the formation(s) from the fluids and natural gas, further protecting groundwater. Standards cover the construction process, including the type of steel for the casing, the number of casings installed and the curing of cement. Monitoring and testing of the construction process also tests the strength of the wellbore and the equipment which is used to inject the fracturing fluids to withstand the pressure of the hydraulic fracturing process.
Upon completion and testing of the wellbore, the hydraulic fracturing process can begin. As depicted at bottom of the image above, this process begins with the perforation of the horizontal portion of the well. Small holes are created in the well casing where small electrical charges will create an initial fracture in the shale. Then, a special mixture of hydraulic fracturing fluids is injected into the well that travels through the perforations to create further fractures within the rock. This mixture also "props open" the fractures to aid in the release of the natural gas.
Comprehensive data collection, analysis and monitoring take place before, during and after the hydraulic fracturing process. Engineers take baseline measurements of the water and rock, and continually monitor the strength of the well throughout the process and conduct real-time mapping of the fracturing of the rock formation. A combination of decades-old techniques and technologically advanced computer systems enable engineers to examine the progress of the hydraulic fracturing treatment, and identify any problems that require intervention.
Production and Site Restoration
Handling of the hydraulic fracturing fluids is a critical step in the process, and research and investments in technology are continually being conducted to develop effective methods of water treatment The fluids that were used during the hydraulic fracturing process are either sent to a water treatment facility or more often than not, being recycled to be used in future hydraulic fracturing jobs.
Once the hydraulic fracturing process is complete, the well is put into production. This entails the installation of a permanent wellhead and other equipment to collect and monitor the production of natural gas. The area surrounding the well is restored, which could include road reconstruction, regrading and landscaping. According to the Pennsylvania Department of Environmental Protection (DEP), companies must comply with Pennsylvania regulations to use preventative measures to"restore the site and vegetation within nine months of well completion by planting grass, trees or crop plots.". Standards are documented in API document, RP 51R, to reclaim, or restore, the site during the life of the producing well as well as after production is complete.
- API HF1, Hydraulic Fracturing Operations—Well Construction and Integrity Guidelines
- API HF2, Water Management Associated with Hydraulic Fracturing
- API HF3, Practices for Mitigating Surface Impacts Associated with Hydraulic Fracturing
- RP 51R, Environmental Protection for Onshore Oil and Gas Production Operations and Leases
- PI Std. 65-2, Isolating Potential Flow Zones During Well Construction
- EPA's Study of Hydraulic Fracturing and Its Potential Impact on Drinking Water Resources