Structural Framework and Evolution of the Northern Wind River Basin:

Implications for Hydrocarbon Migration and Accumulation

By

Daniel D. Schelling

Structural Geology International, LLC, Salt Lake City, UT

David A. Wavrek

Petroleum Systems International, Salt Lake City, UT

Located within the Rocky Mountain foreland of Wyoming, the Wind River Basin is an intracontinental depression surrounded by Laramide basement-uplifts, including the Owl Creek Mountains to the north and the Wind River Mountains to the southwest. While the northern boundary of the Wind River Basin is defined by the Owl Creek Thrust system, which has accommodated up to 10 km of structural uplift, the southwestern boundary is characterized by gently tilted stratigraphic sequences located along the northeast-limb of the Wind River uplift. Within the northern Wind River Basin, hydrocarbon accumulations are generally located along basement-rooted, dominantly south- to southwest-vergent hanging wall anticlines which have formed in the footwall of the Owl Creek thrust system and which have undergone variable degrees of post-Laramide extensional deformation. Two different petroleum systems have been identified within the northern Wind River Basin, including (1) Phosphoria sourced oils which are concentrated along the perimeter of the basin, and (2), Cretaceous-sourced gas and gas-condensate which is concentrated within the central sectors of the basin. Phosphoria oils, generated during the Cretaceous west of the Wind River Basin, accumulated within subtle structural and/or stratigraphic traps prior to remigrating into structural traps located along the southern and western margins of the basin during the Maastrichtian-early Paleocene. In contrast, gas generation from the Cretaceous section occurred during the Tertiary and continues in certain parts of the basin to the present day. Post-Laramide extensional deformation has been critical in creating migration pathways for gas within the deeper sectors of the basin.

AAPG Search and Discovery Article #90004©2002 AAPG Rocky Mountain Section, Laramie, Wyoming