2014 Rocky Mountain Section AAPG Annual Meeting

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Core Facies, Log Facies and Sequence Stratigraphic Analysis of the Late Cretaceous Turner Sandstone, Porcupine Field Area, Powder River Basin, Wyoming


The USGS estimates that the Powder River Basin contains as much as 1050 MMBO and 15,000 MCFG in unconventional, continuous reservoirs, making it one of the more prospective oil and gas basins in the Rocky Mountain region of the western United States. The Turner Sandstone has emerged as one of the “hottest” resource plays in the Powder River Basin. However, unlike its stratigraphically equivalent Wall Creek Member of the Frontier Formation, there is very little published data on the Turner Sandstone. This paper presents the workflow and preliminary results of a core facies, log facies, and sequence stratigraphic evaluation of the Turner Sandstone Member of the Carlile Shale in the Porcupine Field area of southeastern Campbell County. More than a dozen cores and hundreds of well logs were used in this evaluation. The Turner Sandstone disconformably overlies the Pool Creek Member and is conformably overlain by the Sage Breaks Shale Member of the Carlile Shale. The lower Turner Sandstone consists of streaky, lenticular, and wavy bedded heterolithic strata and contains a low diversity, stressed, restricted, or brackish water trace fossil assemblage. The upper Turner Sandstone consists of upward coarsening vertical successions of bioturbated mudstone, bioturbated shaly sandstone, and bioturbated sandstone that are commonly “capped” by cross stratified sandstone and structureless, “cryptically bioturbated” sandstone. The upper Turner Sandstone contains a high diversity, normal marine inner shelf trace fossil assemblage dominated by filter-feeding organisms. Most conventional production was from cross-stratified and structureless sandstone facies that accumulated in elongated, isolated sand bodies or sand ridges. Much of the remaining reserves are stored in low resistivity, pervasively bioturbated, shaly sandstone that represents less active parts of the inner and outer shelf system.