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.