ABSTRACT
Two coalbed methane wells have been drilled at Red Mountain Unit in the Piceance basin near Collbran, Mesa County, Colorado. The wells were drilled as part of the Deep Coal Seam Project, a multi-well project sponsored by the Gas Research Institute to develop, improve, evaluate, and communicate the technology required to produce gas from deeply buried coals. To better characterize the geologic parameters controlling coalbed methane production, research efforts have been directed at a single coal seam at a depth of 5,500 ft (1,800 m). The thickness of the objective or D seam coal, included in the Cameo coal member of the Williams Fork Formation, Upper Cretaceous Mesaverde Group, ranges from 16 to 20 ft (5 to 6.5 m) throughout the unit and is substantiated by nearby well control.
A continuous core, over 200 ft (61 m) thick, was recovered from the first well. Routine and special core tests were performed on samples from both the objective coal and overlying sandstone for the purposes of reservoir evaluation, log analysis, and stimulation design. Pressure transient testing of the objective coal in the first well confirmed the low permeability and/or high skin damage caused by deep invasion of drilling and completion fluids. Interpretation of in-situ state of stress measurements indicates that a conventional hydraulic fracture initiated in the coal will grow upward into the overlying sandstone. Geologic characteristics of the coal and bounding formations were incorporated in a stimulation design to maximize enhancement of the cleat or natural fracture system of the coalbed methane reservoir.
