Huge Subsalt Natural Gas and Condensate Play on Land in the Gulf Coast Basin in Texas and Louisiana
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“YEGUA DOWNDIP GAS PLAY
The Yegua Downdip Gas Play is defined by Eocene Yegua sandstone reservoirs that produce gas from deep overpressured reservoirs across the Western Gulf. The play is bounded updip by the boundary of the Yegua Updip Fluvial Deltaic Oil and Gas Play (4726), and the downdip limit is placed at a depth to Yegua reservoirs of 25,000 ft.
The play begins at the Mexican border and crosses the province to intersect the State-Federal water boundary in southern Louisiana.
Reservoirs in this play are Eocene Yegua slope and submarine fan sandstones. Porosity in the reservoir sandstones ranges up to 25 percent, and permeabilities range up to 100 mD. Slope and fan sandstones are known to exhibit a high degree of reservoir heterogeneity, which seriously affects recovery efficiency.
Depths to undiscovered reservoirs range from 8,000 to 25,000 ft.
Source rocks for the deep overpressured gas have not been positively
identified, but potential source rocks include organic-bearing mudstones of the deep downdip Eocene, including mudstones of the Wilcox, Queen City, Sparta, and Yegua.
Migration of hydrocarbons into reservoirs of this play would have been local, either updip or locally up faults.
Traps for the gas in this play are predominantly structural and are on Yegua
growth faults and possibly on to shale ridges. Gas in fan sandstones in the extreme downdip part of the play may be stratigraphically trapped. Seals are provided by Yegua mudstones that in many cases enclose reservoir sandstones.
Exploration status and resource potential: This play contains 39 gas reservoirs with a median size of 26.3 BCFG discovered between 1948 and 1989. Of the 39 reservoirs, 35 were discovered since 1975, indicating that this is an emerging play. Given the level of exploration and the mapped area of the play, the potential for undiscovered resources of gas is estimated to be very high.” (http://www.sharescene.com/index.php?showtopic=2452&st=2880)