Drillsites are selected based on a number of factors including, availability of land suitable for drilling, city permits, proximity to buildings, parks and other infrastructure, geologic considerations, proximity to natural gas pipelines, feasibility of installing new pipelines if necessary, environmental impact, and the location of wetlands, floodplains, wildlife habitats, and archeological sites. The company’s lease position in the area is also a consideration. Ultimately, energy companies strive to select sites that are the least-intrusive to daily life.
Minor short-term disruptions may occur on-site. There can be noise, dust and traffic. Like any typical construction project, however, the majority of residents will experience few, if any, changes to daily life. Drilling practices are designed to have the smallest possible impact on the environment, and new pipelines pose no more danger than the common public natural gas lines that already service most neighborhoods.
The drilling process begins with padsite construction, which typically lasts approximately one to four weeks depending on the location. Next, the set up of the rig and the drilling of the well will take approximately three to four weeks per well. Multiple wells are sometimes drilled from a single pad site. Although the rig is the most visible part of drilling operations, it is temporary and will be removed once the drilling is completed. Once the layer of rock that holds the natural gas (pay zone) is reached, the well will be completed and prepped for production. Even with multiple-well padsites, the entire process frequently takes less time than the building of a house or store in the same area.
During the approximately three to four weeks of drilling, operations run continuously 24 hours a day, seven days a week. The completion process takes approximately three to five days.
Multiple measures are in place to ensure that drilling operations are environmentally sensitive. Operators must work with communities in determining truck routes and implementing security measures.
As with any construction site, there will be additional truck traffic for the setting up and taking down of the equipment. After the wells are completed, the company regularly returns to monitor and maintain the site. At some wellsites trucks may return to remove naturally occurring water, which is separated from natural gas during the lifting process and stored in tanks located on the site. A typical padsite is three to five acres in size.
Once drilling is completed, storage tanks and other production equipment are installed and the wellsites are fenced for security. In many cases, the company makes additional improvements to the area surrounding the drillsite. Because of these improvements, completed wellsites are frequently more appealing than other utilitarian structures, such as water pump houses or electrical stations.
Chesapeake’s cementing and casing program protects the aquifers from drilling activities. The vertical portion of the wellbore is normally drilled with “air” (through the freshwater aquifers) thus minimizing any risk of contamination. On the rare occasions when fluid is required, freshwater and mud are used instead of air.
Steel casing and surrounding layers of concrete are then installed to isolate the well from the drinking water aquifers through which the wellbore penetrates. The depth at which the surface casing must extend is mandated by applicable state regulatory agencies. In Marcellus Shale operations, the surface casing is typically set to a depth of approximately 1,000 feet, usually more than 300 feet below the freshwater aquifer1.
After it is determined that the well can produce natural gas, additional strings of casing and tubing are set to provide additional layers of separation between the gas stream and the freshwater aquifer. The five layers of steel and cement which go into the construction of a natural gas well virtually eliminate the possibility of contamination to any fresh water zones2.
The state water regulatory agencies require documentation of drinking water aquifer intervals, the design and installation of surface casing relative to those intervals, and the reporting of characteristics of the wellbore along with completion and production data.
Although rare, situations can occur which require an immediate, organized and focused response by Chesapeake. To prepare for and respond to these situations, Chesapeake has developed a single, comprehensive approach to emergency management. By working as a team with emergency response contractors and local first responders, we are able to respond quickly and efficiently with one main objective: protect the public, our employees and the environment.
Sourcing Reference:
1 US Department of Energy - “Modern Shale Gas Development in the United States. A Primer” – Page 76
2 “Hydraulic fracturing considerations for natural gas wells of the Marcellus Shale” Arthur, Bohm, et al presented to Groundwater Protection Council, September 2008. pg 15