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The AAPG/Datapages Combined Publications Database

AAPG Bulletin


Volume: 71 (1987)

Issue: 7. (July)

First Page: 777

Last Page: 787

Title: Exploration for Deep Geopressured Gas: Corsair Trend, Offshore Texas

Author(s): H. A. Vogler (2), B. A. Robison (3)


The Corsair trend is a structural feature centered in the Brazos and Mustang Island areas of offshore Texas, along which proven deep geopressured gas reserves exceed 2 tcf (57 billion m3). The trend is defined by the Corsair fault, a northeast-southwest oriented down-to-the-southeast growth fault that expands the middle Miocene interval. In the central region of the trend, the fault consists of an updip shallow listric portion, an intermediate nearly horizontal platform, and a deep ramp that dips moderately basinward. Bigenerina humblei age sandstones, deposited by a major prograding deltaic system, are exploration objectives in the expanded downthrown section where rollover anticlines occur against the fault ramp. Calcite cementation and/or high clay content r duce porosity and permeability in many Corsair trend sandstones; however, a diagenetic episode of calcite dissolution has resulted in secondary porosity enhancement in some areas, creating excellent quality reservoirs.

Picaroon field, in Brazos area Blocks A-19 and A-20, is a major deep Corsair trend field with estimated gas reserves of 400 bcf (11 billion m3). Development of the field was dependent on solving engineering problems associated with corrosive gas, high temperature, and hard geopressured environment. The Picaroon field structure is a northeast-southwest-trending anticline cut by numerous small faults and truncated by an unconformity on its eastern flank. Further exploration along the Corsair trend will probably consist of field stepouts and drilling to deeper zones on already productive structures.

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