Developing Shale Gas Wells, From Leasing to Production
There are several steps in the development process of any hydrocarbon resource, including obtaining permission to drill from the landowner and government, constructing a temporary drilling site, and using a drilling rig to drill the well. A key aspect of releasing natural gas from shale rock formations is the combination of two established technologies—horizontal drilling and hydraulic fracturing, where water is injected under pressure to crack the rock and release the trapped gas. Once this process is complete, the well is ready to produce natural gas, which will be transported to market.
Signing Leases and Securing Permits
We first obtain permission to drill from the landowner, typically through a lease, and consult with the landowner when choosing a well site. Next, we secure permits from regulatory agencies. We conduct environmental impact studies to identify sensitive areas such as archeological sites or threatened and endangered plants and animals. We then submit our designs and construction plans as well as other information for regulatory approval.
Gathering Seismic Data
Seismic imaging is a tool that helps us understand what lies beneath the earth by bouncing sound waves off underground rock structures to reveal possible oil- and gas-bearing formations. Seismologists use seismic trucks to generate sound waves and ultrasensitive devices called geophones to record how the sound waves echo within the earth. By studying the echoes, earth scientists try to determine the best location to place the well in the shale rock. Seismic imaging also helps well-site teams optimize drilling before it starts. Seismic activity requires permits by regulators.
Constructing the Well Site
Once permits are secured, we build a well site. These sites, called well pads, vary in size, and we work to build pads as small as possible. By drilling multiple wells from one well pad, we minimize land use and the number of roads needed to the site.
Drilling the Well
In our Marcellus operations, a drilling rig is used to drill a vertical well approximately 8,000 feet (2,438 m) below the earth's surface. The rig then drills horizontally, about 2,000 to 6,000 feet (610–1,829 m) outward into the layer of shale rock. Our wells in Pennsylvania have a combination of as many as eight layers of steel casing and cement, which forms a continuous barrier between the well and the surrounding formations.
Hydraulic Fracturing
Hydraulic fracturing is a common practice in oil and natural gas development—90 percent of oil and gas wells in the U.S. undergo fracturing to stimulate production. It has been used since the 1940s in more than 1 million wells in the United States. In hydraulic fracturing, a fluid comprised of more than 99 percent water and sand and less than 1 percent chemical additives is pumped down the well at a high pressure for a short period of time, usually hours. This creates a network of cracks in the rock that allows trapped natural gas to flow to the well. The sand helps keep the fractures open and gas flowing. In Chevron's Marcellus operations, hydraulic fracturing is performed in sections along the length of the horizontal well. The entire process takes five to seven days.
Building Natural Gas Pipelines
Once a well has been completed, it is ready to produce natural gas for market. A pipeline will be installed from the new well to an existing system that will take the natural gas to market. It will be used for electrical generation, heat for homes and other energy needs.
Remediating the Drilling Site
It takes up to a year to build the well site and drill and complete the well. After the process is complete, we work with the landowner to restore the land with minimal impact to its original contours. We plant indigenous grass using a process called hydroseeding to accelerate regrowth. Throughout the well development process, the regulatory agency ensures compliance through regular inspections.
Producing Natural Gas for Decades
After the well site has been remediated, the remaining footprint of a natural gas well is typically less than one acre. It includes a well head, a gas processing unit and one or two water tanks. Natural gas wells that produce from shale rock are expected to have a long production life spanning several decades.
Updated: May 2012