--> A Vintage Well Perspective on Basin Model Production Prediction Within the Niobrara Formation, Southern Powder River Basin, Wyoming

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A Vintage Well Perspective on Basin Model Production Prediction Within the Niobrara Formation, Southern Powder River Basin, Wyoming

Abstract

The Late Cretaceous Niobrara formation is a steadily emerging unconventional resource play within the greater Rocky Mountain foreland province. A substantial amount of research and operational effort has been directed towards understanding the complexity of the Niobrara in the Denver-Julesberg (DJ) basin. While sharing the same shallow seaway depositional environment as the DJ basin, but with an alternative Laramide-style deformation sequence of events and diagenetic alteration, the Powder River basin stands valiantly as a viable resource play for the Niobrara. This is especially true for the deeper, geochemically mature southern portion (Converse and Niobrara Counties) of the Powder River basin. As a completely self-sourced reservoir, the Niobrara formation makes up a cohesive petroleum system, free from the effects of any external geology. The alternating brittle, chalk-rich reservoir intervals and associated ductile, marl-rich source rock intervals lead to a predictable hydrocarbon migration system. Such migration information plays a critical role in optimized well placement and hydraulic stimulation planning, ultimately leading to enhanced production. It was therefore of paramount importance that a complete visualization of the brittleness behavior, trends, and patterns be actualized. A basin model was created in order to statistically interpolate such patterns and trends inherent within the subsurface environment. The approach to such an endeavor had one objective in mind - use free, publicly available well data. The gamma ray (GR) log curve provided the much needed information pertaining to the "purity" of the chalk-rich reservoir intervals. Within the confines of the Niobrara, lower GR units indicated increasingly "pure", and hence, more brittle reservoir rocks conducive to natural hydrocarbon migration and fracturing. In order to test such results, this information pertaining to the optimal "sweet spot" well placement was compared to present-day and historical petroleum production. The results prove that if the basin modeler continually ties the model back to a clearly defined objective central to the history of the rocks, the limitation of data availability may be ultimately ignored.