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Title: Measurement of stress-dependent permeability in coal and its influence on coalbed methane production

It is known that coal permeability measured in the laboratory is highly sensitive to the net confining pressure applied on the sample. Since many coalbed methane modeling studies assume that the permeability of a coal seam does not change with reservoir pressure depletion, skepticism about the accuracy of future predictions is understandable. This paper presents laboratory-measured permeability reduction during reservoir pressure depletion using a whole-core sample of coal in uniaxial strain at reservoir conditions. These laboratory results have been used in a numerical simulation study to determine the influence of pressure-dependent permeability on coalbed methane production. The productivity of a coalbed methane well is substantially reduced because of the decline in coal permeability during reservoir pressure depletion. More significantly, most of the reduction in gas and water production rates because of pressure-dependent permeability occurs during well start-up. Thereafter, the well productivity loss due to stress dependent permeability is fairly gradual over a very long period of time. The characteristic gas and water production-rate profiles obtained from a numerical simulator are almost the same regardless of whether the coal seam permeability is assumed to be constant or stress-dependent.
Authors:
 [1] ;  [2]
  1. (Amoco Production Co., Denver, CO (US))
  2. (Amoco Production Co., Tulsa, OK (US))
Publication Date:
OSTI Identifier:
7103499
Resource Type:
Journal Article
Resource Relation:
Journal Name: In Situ; (United States); Journal Volume: 16:3
Country of Publication:
United States
Language:
English
Subject:
03 NATURAL GAS; COAL; PERMEABILITY; METHANE; PRODUCTION; FLUIDIZED BEDS; INHIBITION; LABORATORIES; NATURAL GAS WELLS; PRESSURE DEPENDENCE; SIMULATION; SIMULATORS; STRESSES; ALKANES; ANALOG SYSTEMS; CARBONACEOUS MATERIALS; ENERGY SOURCES; FOSSIL FUELS; FUELS; FUNCTIONAL MODELS; HYDROCARBONS; MATERIALS; ORGANIC COMPOUNDS; WELLS 030300* -- Natural Gas-- Drilling, Production, & Processing