International Journal of Coal Geology, Vol.49, No.1, 19-31, 2002
Key parameters controlling coalbed methane cavity well performance
Openhole cavity completions have proved to be remarkably successful in improving the coalbed methane well productivity in the "fairway" region of the San Juan basin, USA. This technique employs a series of controlled injection/blowout processes to create a cavity in the target seams to enhance the formation permeability around the cavity. The cavity wells in the "fairway", which are characterised by overpressured, highly permeable thick coals, generally yield production levels several times greater than hydraulically fractured wells. In the areas outside the fairway, however, hydraulically fractured wells have generally proved to be more productive. This paper reports on the application of a geomechanical finite element model to a dedicated field research cavity well established in the fairway, Using the published field data as input, the model predictions are in good agreement with the field findings in terms of the cavity size and post-cavity permeability enhancement. The results of a parametric study demonstrate that the formation permeability is the most important parameter controlling cavity well performance. This result is consistent with the field experience in the San Juan basin. (C) 2002 Elsevier Science B.V. All rights reserved.