The remarkable success achieved for producing gas fromcoal seams in the San Juan Basin can be attributed largely toutilization of the innovative open-hole cavitation (OHC) technique. Nearly 70% of the San Juan Basin coalbed methane is produced fromOHC wells even though they only account for 20% of the producingcoalbed methane wells. Most OHC wells are located within anorthwest trending fairway situated in the north central portion ofthe San Juan Basin. Within this fairway, wells completed with theOHC outperform hydraulic fractured wells by a factor of five. Outside the fairway, hydraulically fractured wells typicallyoutperform OHC wells. The production variability is related toregional changes in reservoir conditions as reflected by varyinggeologic characteristics. The geological parameters leading tosuccessful OHC wells have been inadequately studied forpredictability using the OHC technique outside of the existingcavity fairway. The planned research is directed towards resolvingthe geologic systems favorable to achieving cavitation with initialhigh gas rates. Preliminary production mapping suggests thecavitation fairway is characterized by a northwest trendextensional fractured zone which has intersected coal reservoirs atfull absorptive capacity with free gas in the fractures. Phase Iwill delineate the origin of this unique system by (1) establishingbasement wrench faulting tectonics using seismic andstratigraphic mapping, (2) thermal modeling to help quantifyorigin of high gas retention and trapping mechanisms, and (3)extensional, low stress setting, and fracturing hypothesis to besupported with surface fracture mapping using remote imagery. InPhase II the predictive model calibrated against the productionanomaly fairway in the San Juan Basin will be used in screeningother coal basins for regions suitable for the OHC completiontechnique.Anticipated Results/Potential Commercial Applications as described by the awardee:A predictive exploration rationale and model forlocating potential coalbed methane production using cavitycompletion methods will be developed. The predictive model will becalibrated against the cavity fairway in the San Juan Basin. InPhase II, the model and methodology will be applied to other coalbearing basins in an effort to locate regions where the OHCtechnique could be utilized. Successful identification of newcavity fairways would result in the discovery of substantial newgas reserves.
