Mamm Creek Field produces from sandstones of the Mesaverde Group that are part of a pervasive gas accumulation in the deeper part of the Piceance Basin. Most production is from discontinuous fluvial sands in the Williams Fork Formation, but marine sands in the Corcoran, Cozzette, and Rollins members of the Iles Formation and middle and upper sands of the Williams Fork Formation also contribute. Coals are present in the lower third of the Williams Fork, and are believed to be the primary source of gas for the Williams Fork production. The sandstones of the Mesaverde have permeabilities in the 1–100 microdarcy range and have average porosities of about 9%. Abundant natural fracturing has been documented in core and image logs, and is critical to providing permeability for commercial production. Detailed mapping of all features that may control the distribution of both reservoir gas and fractures is critical to effective development of the resources at Mamm Creek. The application of advanced seismic analysis and mapping techniques, some of which are discussed below, is part of the effort to more fully understand the relationships between geology and gas production.

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