During the drilling process, Chesapeake’s cementing and casing program is used to protect water 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 the 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 freshwater 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:
1US 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