Coal-Bed Methane Production in Eastern Kansas: Its Potential and Restraints

Bill T. Stoeckinger

In 1921 and again in 1988, workers demonstrated that the high volatile A and B coals of the Pennsylvanian Cherokee Group can be produced economically from vertically drilled holes, and that some of these coals have a gas content as high as 200 ft³/ton. Detailed subsurface mapping on a county-by-county basis using geophysical logs shows the Weir coal seam to be the thickest (up to 6 ft thick) and to exist in numerous amoeba-shaped pockets covering several thousand acres. Lateral pinch-out into deltaic sands offers a conventional gas source. New attention to geophysical logging shows most coals have a negative SP response, high resistivities, and densities of 1.6 g/cm³. Highly permeable coals cause lost circulation during drilling and thief zones durin cementing, and they are the source of abundant unwanted salt water. Low-permeability coals can be recognized by their high fracture gradients, which are difficult to explain but are documented to exceed 2.2. Current successful completions use both limited-entry, small-volume nitrogen stimulations or an open hole below production casing. Subsurface coals are at normal Mid-Continent pressures and may be free of water. Initially, some wells flow naturally without pumping. Saltwater disposal is often helped by the need for water in nearby waterflood projects and the easy availability of state-approved saltwater disposal wells in Mississippi and Arbuckle carbonates. Recent attempts to recomplete coal zones in slim-hole completions are having mixed results. The major restraints to coal-bed me hane production are restricted to low permeability of the coals and engineering problems, not to the availability or gas content of the coals.

AAPG Search and Discovery Article #91025©1989 AAPG Midcontinent, Sept. 24-26, 1989, Oklahoma City, Oklahoma.