Leta K. Smith¹

(1) IHS Energy Group, Houston, TX

ABSTRACT: Gas Production and Fractures in Almond Sandstones, Greater Green River Basin, Wyoming

The presence of fracture swarms and larger through-going faults commonly are critical elements of gas producibility from basin center gas accumulations. The Almond Formation has a complex plumbing system that is related to both major lineaments in the basin and smaller scale fractures in the reservoir. At the basin scale, high salinity anomalies spatially correlate with major lineaments. At the reservoir scale, fractures provide conduits for fluid flow between reservoir units at some places but compartmentalize the reservoir at others. For example at Standard Draw field, high gas-production areas are ones generally lacking in calcite cement, and connection between Upper and Lower Almond reservoirs is provided by open fractures. Evidence of gas contribution from the Lower Almond is given by Lower Almond formation water producing from wells completed in the Upper Almond in high gas production areas. At Siberia Ridge field on the other hand, Lower Almond contribution to gas production was not found to be important which is one of several reasons that Siberia Ridge is not as prolific a gas producer as Standard Draw. At Siberia Ridge numerous compartment barriers were identified by variations in fluid chemistry between adjacent wells. This corroborated the existence of linear features identified from 3-D seismic and provided additional information on whether fractures were open or closed, which was not apparent from seismic.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado