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), 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 state regulatory agencies. In Colorado, the surface casing is typically set to a depth of approximately 1,000 to 1,600 feet, usually about 200 feet below the freshwater aquifer.
Additional strings of casing and tubing are then set to provide additional layers of separation between the oil or gas stream and the freshwater aquifer. The multiple layers of steel and cement that go into the construction of an oil or natural gas well virtually eliminate the possibility of contamination of any freshwater zones.
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.​