A Critical Compilation of 1,500 Large Onshore Gas Reservoirs in Texas Gulf Coast and East Texas

E. C. Kosters, R. J. Finley, N. Tyler

About 1,500 gas reservoirs in the Texas Gulf Coast and east Texas have a cumulative production of at least 10 bcf. The Gulf Coast contains nearly 90% of these reservoirs. One-third of all reservoirs have produced more than 30 bcf, and another 10% have produced more than 100 bcf. In the Gulf Coast, total production from the greater than 30 bcf reservoirs is 66 to 75% of the cumulative production of all greater than 10 bcf reservoirs, the Oligocene Frio Formation accounting for about 55% of reservoirs and cumulative production. In east Texas, the greater than 30 bcf reservoirs represent 75 to 80% of the cumulative production.

Reservoirs are segregated into plays, each identified on the basis of structural and depositional setting, trapping mechanism, and lithology. In the Gulf Coast, 33 gas plays, including 20 subplays, are defined. East Texas contains 12 plays with 7 subplays. Important gas plays occur in multiple formations in each region.

Fluviodeltaic sandstones of the upper Vicksburg and lower Frio Formations, overlying the south Texas Vicksburg fault zone, form the most prolific play of both regions. Other important Tertiary plays are south Texas upper Wilcox shelf-edge deltaic and reworked shallow marine sandstones, deltaic Yegua sandstones in the Houston salt basin, and Miocene stream-plain reservoirs in the central coastal region. Shallow-marine limestones of the Edwards Formation form the most important play of the Gulf Coast Cretaceous. In east Texas, the biggest plays occur in the Lower Cretaceous Glen Rose limestones of the Sabine uplift, followed by Smackover limestones of the western part of the East Texas basin.

Play designation enhances understanding of critical geologic and engineering parameters and is crucial to increasing effectiveness in exploration and production. Future detailed development studies of representative reservoirs within important plays will help define reservoir behavior, allow predictions of potential ultimate recovery, and where applicable, aid in suggesting appropriate recovery enhancement techniques such as infill drilling and recompletion of bypassed zones.

AAPG Search and Discovery Article #91030©1988 AAPG Annual Convention, Houston, Texas, 20-23 March 1988.