Powder River

Commentary

Activity continues in the Basin, but discoveries are becoming increasingly small. Nevertheless, the Basin will remain a focus for M&A activity and consolidation. However, despite a supportive State regulator, the overriding concern is at the Federal level, and to what extent the Biden Administration will use Federal powers to override State legislation to prevent oil & gas development.

Updated

August 17, 2023

Location

Description

The PRB, located in north-eastern Wyoming and south-eastern Montana, developed during the Laramide orogeny similar to other Rocky Mountain foreland structural basins; the Basin is asymmetric with the axis on the west side. The deepest part can be >17,000ft to the top of the Precambrian basement. The boundaries of the Basin are delineated by several uplifts including the Black Hills to the east (including the Fanny Peak monocline), the Hartville uplift and Laramie Range to the south, the Casper arch, Bighorn Mountains, and the Hardin platform on the west, and the Miles City arch, Bull Mountains, and Porcupine dome on the north. Except for the broad arching structures, most basin bounding features are hydrologic as well as structural boundaries. In the PRB, numerous structures now observed at the surface originated as faults, shear zones, or zones of weakness in the basement rocks during Precambrian time and were rejuvenated during the Laramide orogeny, and by periodic recurrent movement throughout the Phanerozoic. In the PRB, most structures are oriented northwest-southeast and northeast‑southwest, trends that probably influenced local and regional sedimentation patterns. The location of the shoreline during deposition of the Upper Minnelusa Sandstone was parallel to northeast southwest-trending normal faults, with the downthrown side to the southeast toward an open sea. Upper Minnelusa oil fields are generally aligned with the prevailing trend, thereby reflecting the structural control on the orientation of reservoir rock deposition. The same structures also influenced drainage patterns on erosional surfaces during deposition of Cretaceous reservoirs. It has long been established that the Phosphoria Formation generated considerable amounts of hydrocarbons that were trapped in numerous Palaeozoic reservoirs in the north-central Rocky Mountains, including the Minnelusa Formation and Tensleep Sandstone. Although alternative sources of oil in Minnelusa and Tensleep reservoirs in the Basin have been proposed, most agree that the Phosphoria is the main source of oil, based on published geochemical evidence.

Summary

While widely explored, the Basin continues to present new play types, not least the growing focus on shale gas. However, the low gas price presents a headwind to most activity.