Measuring and testing – Borehole or drilling – Formation logging
Reexamination Certificate
2005-03-01
2005-03-01
Williams, Hezron (Department: 2856)
Measuring and testing
Borehole or drilling
Formation logging
C073S152050, C073S152110, C073S152020, C166S263000, C166S266000, C166S268000, C166S280100, C166S305100, C166S253100, C166S267000, C166S402000
Reexamination Certificate
active
06860147
ABSTRACT:
A method for predicting the secondary porosity system (SPS) porosity, and thereby permeability, of a coal bed involves determining an initial condition in the coal bed, including an initial SPS pressure and an initial sorbed gas composition, determining a pressure strain effect due to increasing the SPS pressure to a value greater than the initial SPS pressure, and determining a sorption strain effect due to changes in the sorbed gas composition resulting from decreasing the methane content and increasing the content of a stronger adsorbing fluid (SAG) relative to the initial sorbed gas composition. Preferably, the method uses data from test injections of water and/or a weaker adsorbing fluid (WAG) and a SAG. The data is used in the inventors' model to compute a SPS porosity and an absolute permeability at a reference SPS pressure and a reference sorbed gas composition. Preferably, the reference pressure is atmospheric pressure. The inventors' model accounts for both dynamic pressure strain and dynamic multicomponent sorption strain effects. As a result, a calibrated model can be produced for the coal bed for predicting the coal bed's SPS porosity, and thereby permeability, as a function of a pre-selected injection or production fluid's composition and/or SPS pressure conditions.
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Gunter William Daniel
Mavor Matthew John
Alberta Research Council Inc.
Jackson André K.
Tassel Kurt D. Van
Van Tassel & Associates
VandenHoff Deborah G.
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