--> ABSTRACT: Facies, Faults and Potential Sweet Spots in a Tight Gas Reservoir: Almond Formation, Wyoming, by Randi Martinsen, William Iverson, and Ronald Surdam; #91019 (1996)

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Facies, Faults and Potential Sweet Spots in a Tight Gas Reservoir: Almond Formation, Wyoming

Randi Martinsen, William Iverson, and Ronald Surdam

The Almond Formation is a major producer of gas in southwestern Wyoming. Although exploration generally is aimed at finding conventional reservoirs in upper Almond marine sandstones, the majority of Almond gas is contained in the underlying main Almond, a succession of dominantly non- marine, interbedded tight sandstones, siltstones, carbonaceous shales and coals. Production data indicate that some of the best gas wells completed in upper Almond sands show little production decline and have already produced more gas than calculations indicate they contain. This implies that these wells have somehow successfully tapped into the vast supply of gas contained in the main Almond. We believe that the more permeable reservoirs, in addition to providing "sweet spots" for explorat on, also serve as lateral conduits capable of draining gas over a broad area from the main Almond. The "sweet spots" themselves do not need to be volumetrically large, only permeable and laterally continuous. Previously unrecognized marine sands, similar to those in the upper Almond, are favorably located in the middle of the main Almond succession and may provide additional lateral conduits. Studies also show that syndepositional faults significantly influenced deposition and may also be important in terms of fluid flow. At least some syndepositional faults are associated with anomalously high gas and/or water production within fields, and may be vertical conduits for fluid flow.

AAPG Search and Discover Article #91019©1996 AAPG Convention and Exhibition 19-22 May 1996, San Diego, California