Exploration History of the Northern Mustang Island, Gulf of Mexico, Texas State Waters

Jeff A. Spencer and Elliot Barrett
Black Pool Energy, 12012 Wickchester Ln., Ste. 140, Houston, Texas 77079

During the last fifty years, the northern Mustang Island, Gulf of Mexico, Texas state waters have experienced renewed periods of successful exploration, approximately every ten years. The first state leases in the area were awarded in 1953, and initial exploration on these tracts resulted in the discovery of the two largest fields in the area; Mustang Island Block 889-S/883-S Field(s) (150+ BCFGE [billion cubic ft of gas equivalent]; 1955) and Mustang Island Block 904-S Field (130+ BCFGE; 1957). Subsequent periods of drilling success occurred in 1969-74, 1981-90, and 1998-2005. In addition to step-outs and deeper pool discoveries within existing fields, new fields included Mustang Island Block 772-L (42 BCFGE; 1981) and Mustang Island Block 749-L/746-L (67 BCFGE; 1969/1987). An extensive 3D seismic grid, shot in the mid-90s, helped initiate the most recent period of drilling. Exploration using 3D amplitudes and amplitude versus offset (AVO) techniques has been successful in the discovery of new reserves in the area’s Middle Frio sands near the northern edge of this thick fluvial-deltaic system.

Major reservoirs include Upper Frio thin, shelf sands, as well as, Middle Frio thick, stacked, fluvial-deltaic sands. Production ranges from about 7500 ft to 15,000 ft. The traps are predominantly high-side fault closures, but downthrown fault closures, subtle four-way closures, and small combination structural-stratigraphic traps do occur. All of the Frio reservoirs are in, or very near the top, of geopressure. Surprisingly, the first shallow, normally-pressured Miocene discovery occurred in 2006.

Production in the area includes a high-rate oil reservoir (MT-2 Sand; Mustang 904- S), a low resistivity/low contrast log pay (Mustang 904-S and 883-S), and a single zone completion gas well that has been producing for nineteen years (32 BCFG; Mustang 746- L).

AAPG Search and Discover Article #90069©2007 GCAGS 57th Annual Convention, Corpus Christi, Texas