AskChesapeake

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 the applicable state regulatory agencies. In Anadarko Basin operations, 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.In Texas, conductor casing is set approximately 60 to 80 feet below ground, while the surface casing is typically set to a depth of approximately 1,200 to 1,800 feet.In Texas, the surface casing is typically set to a depth of approximately 1,100 to 4,800 feet, usually about 50 to 100 feet below the freshwater aquifer.In Haynesville Shale operations, the surface casing is typically set to a depth of approximately 1,850 feet. Then intermediate casing is set inside the surface casing to a depth of usually more than 11,200 feet below the freshwater aquifer¹.In Mississippi Lime operations, 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.In Marcellus Shale operations, the surface casing is typically set to a depth of approximately 700 feet. Then intermediate casing is set inside the surface casing to a depth of approximately 2,500 feet, usually more than 1,000 feet below the freshwater aquifer¹.In Wyoming, the surface casing is typically set to a depth of approximately 1,500 to 2,000 feet, usually about 100 to 200 feet below the freshwater aquifer.In Ohio, Chesapeake follows the rules of the Ohio Department of Natural Resources along with adding extra protection measures to protect freshwater aquifers.

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 to any freshwater zones¹²².

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.