Geologic and Hydrologic Controls Critical to Coalbed Methane Producibility and Resource Assessment:Williams Fork Formation, Piceance Basin. Northwest Colorado

摘要

As predicted from an evolving coalbed methane producibility model, extraordinary coal gas production is precluded in the Piceance Basin by the absence of reservoir continuity and dynamic ground-water flow The best potential for coal gas production may lie in conventional traps basin ward of where outcrop and subsurface coals are in good reservoir and hydraulic communication and in areas of vertical flow potential. Synergism between tectonic and structural setting, depositional systems and coal distribution, coat rank, gas content, permeability and hydrodynamics are controls critical to coalbed methane producibility. Within the genetically defined, coal-bearing Upper Cretaceous Williams Fork Formation, net coal thickness is typically 80 to 120 ft and is thickest in a north-south belt, behind west-east prograding shoreline sequences. Depositions) setting and thrust faults cause coals along the Grand Hogback and in the subsurface to be in modest to poor reservoir and hydraulic communication, restricting meteoric ground water recharge and flow basinward.