Abstract: Assessment of Oil and Gas Resources in Idaho-Wyoming Thrust Belt

Richard B. Powers

New oil and gas discoveries in the past 2 years in the southern part of the greater Cordilleran overthrust belt at Pineview field, Utah, and at Ryckman Creek and Yellow Creek fields, Wyoming, indicate a significant oil and gas resource potential in the province. The province contains widespread source beds and reservoirs, particularly in Cretaceous, Jurassic, Triassic, and Permian rocks. On the basis of recent discoveries, the Nugget Sandstone reservoir of probable Triassic-Jurassic age and the overlying Jurassic Twin Creek Limestone constitute the main exploration targets.

Promising structural traps are indicated in overthrust and subthrust blocks. However, lateral-facies foreshortening, trap distortion by thrusting, and lack of subsurface control make pinpointing of these structural targets uncertain. Detailed interpretation of seismic data, coupled with geologic estimation of preexisting sedimentary-basin outlines and knowledge of the regional structural evolution of the province, is the primary approach to solving these problems.

Estimates of undiscovered recoverable resources are made by using volumetric-yield analytic procedures. Appraisals of undiscovered resources based on geologic evaluation are made by use of subjective probability techniques.

AAPG Search and Discovery Article #90969©1977 AAPG-SEPM Rocky Mountain Sections Meeting, Denver, Colorado