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AAPG Pacific Section and Rocky Mountain Section Joint Meeting

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Mowry Shale - Outcrop to Production


The increase in commodity prices and development of technology in the late 2000s created opportunity to exploit previously uneconomic drilling targets, including a number of oil-generating shales. Two important source-rock shale in the Northern Rocky Mountains are the Mowry and Niobrara shales. Although both shales have been drilled using current completion techniques, the Niobrara has been targeted much more than the Mowry in the Powder River Basin. Momper and Williams (1984) estimated that the Mowry Shale has generated 11.9 billion barrels of oil and expelled 7% or approximately 830 million barrels of oil in the southern Powder River Basin. This illustrates the importance of the Mowry Shale to oil production in eastern Wyoming. A small number of vertical and horizontal wells in the Powder River Basin produce oil from the Mowry but few of these have been economic. The keys to drilling, completing and economically producing the Mowry have yet to be discovered. The Mowry Shale is a siliceous shale, which makes it very brittle. It is interbedded with bentonites and other clay minerals. Although the carbonate-based Niobrara Shale has interbedded bentonites and other clays, the Mowry has some different issues with respect to drilling and completing than the Niobrara. This presentation will review geologic aspects of the Mowry and review historic and recent development.