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Coal Bed Methane - CBM Drilling

2013-07-16

Coal Bed Methane

Coal-Bed Methane (CBM) Drilling is performed with rotary and core drilling equipment. Rotary rigs are used to drill and set casing for production wells, and, along with core drills, are used to drill long directionally-drilled holes into coal seams from which coal-bed methane gas is extracted.  Due to the occurrence of gas, blow-out preventers are often needed.

CBM is an unconventional source of natural gas produced from gas residing in coal seams.  Often this gas is not pressurized, and is dissolved in the naturally occurring groundwater. CBM wells are typically shallow (less than 1000 meters total depth) and have a single string of surface casing cemented in place.  This surface casing string is usually 10% of the final hole depth.
A production casing extends from the surface to the gas rich seams, and in some cases a third "pump" casing is set, to facilitate pumping groundwater/gas liquid out of the hole.
Typical CBM wells are drilled quickly.  Often a well can be drilled and completed in less than 48 hours.  Drilling penetration rates and final well construction details can vary greatly between different CBM fields.