--> ABSTRACT: Hydrocarbon Plays and Depositional Styles of Reservoirs: Texas Offshore State Waters, by Bruce A. Desselle, Steven J. Seni; #91020 (1995).

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Hydrocarbon Plays and Depositional Styles of Reservoirs: Texas Offshore State Waters

Bruce A. Desselle, Steven J. Seni

The University of Texas at Austin, Bureau of Economic Geology, in cooperation with the Minerals Management Service, the Gas Research Institute, and the U.S. Department of Energy, is developing gas and oil atlases of reservoirs in State and Federal waters, offshore northern Gulf of Mexico. Reservoirs in 24 hydrocarbon plays in Texas Offshore State waters alone have produced more than 3.6 Tcf of gas. Hydrocarbon-producing facies are apportioned to four depositional styles: progradational (71%), retrogradational (17%), submarine fan (11%), and aggradational (1%). The progradational plays, best developed in upper Oligocene and lower Miocene reservoirs, have favorable sand-shale ratios, excellent porosity, and numerous seals. Progradational styles characteristically produce ab ndant hydrocarbon traps associated with growth faults and rollover anticlines. Submarine-fan plays are both aerially restricted and limited to lower Miocene strata in Texas Offshore State waters. Middle Miocene reservoirs are dominated by aggradational and retrogradational plays as a result of progradation of the early Miocene continental margin. Retrogradational plays have thin packages of backstepping sandstone reservoirs separated by transgressive shales. The small amount of gas from the aggradational style results from limited seals in a sandstone-rich interval.

The lower Miocene interval contains the largest number of reservoirs (285) and the greatest cumulative gas production (2.4 Tcf). The LM4 chronozone (Discorbis B and Marginulina ascensionensis) has the most reservoirs (162) and the greatest production (1.1 Tcf) in Texas Offshore State waters. The Progradational Siphonina Davisi Sandstone-Galveston and High Island Areas (LM2-1) is the largest play, comprising 61 reservoirs and having a cumulative production of 649.3 Bcf (18.0%). The Progradational Marginulina Ascensionensis Sandstone-Matagorda Island and Brazos Areas (LM4-1) is the second largest play, comprising 40 reservoirs and having a cumulative production of 627.8 Bcf (17.4%) in Texas Offshore State waters.

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995