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Case Study: Greater Wamsutter Field, Wyoming—Tight Gas Reservoir

G. Earl Norris and Tony McClain. BP America Production Co, WL-1, 2.220, Houston, TX 77079, phone: 281 366 5452, [email protected]

The development and exploitation of one of Wyoming's Cretaceous tight gas plays in complex marine, marginal-marine, and coastal plain reservoirs can be challenging. Indeed, there does seem to be gas nearly “everywhere.” However, the presence of associated water production and reservoir complications make economically producible rates far from guaranteed. Some specific areas of the greater Wamsutter field have proven to be particularly challenging in this regard, and lessons learned from these “failures” can broaden the understanding of risks associated with tight gas development.

The Rasmussen area (northwest side of the “Greater Wamsutter” field) has experienced particularly disappointing results over an eighteen month stretch of drilling activity in 2003-4. The targeted perforated intervals underlie a thick and extensive upper Almond marine bar that is one of the few water-wet reservoirs in the upper Almond. The presence of this water zone, linked to the rest of the usually productive Almond sands, presumably by fractures, may be at least partially responsible for the poor performance. There may also be other reservoir-compromising issues at play. The southeast side of Wamsutter is also seeing a similar relationship between an extensive, water-wet, shoreface sand and underlying reservoirs. In both areas, it is suspected that these extensive sands are plumbed to the surface, explaining their high water saturations.