Daniel D. Schelling¹, David A. Wavrek²

(1) Structural Geology International, Salt Lake City, UT
(2) Petroleum Systems International, Inc, Salt Lake City, UT

ABSTRACT: Structural Geology and Petroleum Systems of the Northwestern Wind River Basin, Wyoming

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. The northwestern Wind River Basin is characterized by a series of basement-rooted, dominantly south- to southwest-vergent thrust faults and associated hanging wall anticlines which have formed in the footwall of the Owl Creek thrust system, though north-south oriented structures are also present within the basin. Two different petroleum systems have been identified within the western Wind River Basin, including (1) Phosphoria-sourced oils which are reservoired primarily in the Tensleep Sandstone, Phosphoria Formation and Nugget Sandstone, and (2), Cretaceous-sourced gas/gas-condensate which are reservoired primarily within Cretaceous sandstones. Phosphoria oils were generated during the Cretaceous in the Wyoming fold-thrust belt area, prior to the development of the Wind River Basin. The oils accumulated within subtle structural highs and/or stratigraphic traps within the basin, and subsequently re-migrated into structural traps on the southern and western margins of the basin during the Maastrichtian-early Paleocene. In contrast, gas generation from the Cretaceous section occurred in the Tertiary and continues in certain parts of the basin to the present day. Post-Laramide extensional faults supply critical vertical migration pathways for Cretaceous gases, which migrate either up or down section according to the prevalent overpressure regimes. This study provides petroleum system insights into the hydrocarbon resources of the Wind River Basin that are applicable to other Laramide basins as well.

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