--> Abstract: Main Pass 299, Offshore, Louisiana: Producing Oil, Gas, and Sulfur from the Same Reservoir, by R. J. Christensen and L. B. Green; #91004 (1991)

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Main Pass 299, Offshore, Louisiana: Producing Oil, Gas, and Sulfur from the Same Reservoir

CHRISTENSEN, ROBERT J., Freeport-McMoRan Oil & Gas Company, New Orleans, LA, and LARRY B. GREEN, Freeport Sulphur Company, New Orleans, LA

In 1989, a world class sulfur deposit and a new oil pool with a small gas cap were discovered together in the limestone caprock of a shallow piercement salt dome at Main Pass 299, Offshore, Louisiana. Twenty exploration wells were drilled to delineate the resource. The salt dome is roughly circular and relatively flat-topped with a diameter of 8000 ft at the shallowest occurrence of salt at 1775 ft subsea. Vugular limestone caprock occurs at 1250 ft subsea and is up to 400 ft thick in the southeast quadrant of the dome. Porosity in the limestone averages 27% with permeability as high as 18 d. Below the limestone is dense anhydrite, up to 125 ft thick, and then diapiric salt. Native sulfur occurs up to 200 ft thick in the lower part of the limestone. Oil and gas occur in the upper part of the limestone with the G/O contact at 1350 ft subsea and the O/W contact at 1532 ft subsea. Proven recoverable reserves are currently estimated at 67 million long tons sulfur, 38 MMBO, and 8.5 BCFG.

Sulfur, oil, and gas will be produced concurrently using a synergistic blending of Frasch sulfur mining techniques and oil and gas production technology. Using the Frasch method, seawater heated under pressure to 325 degrees F is injected into the limestone caprock where it melts in situ the elemental sulfur at 246 degrees F, which is produced, stored, and transported as a liquid. Six platform structures and ultimately about 1500 sulfur wells are well planned to produce the sulfur at a rate of two million long tons per year for 30+ years. Hot water injection is anticipated to enhance oil production by maintaining reservoir pressure and lowering the viscosity of the 22 degree gravity oil. Four platform structures and from 22 to 44 wells, some with horizontal completions, are planned to produce the oil and gas at an initial rate of 50,000 BOPD and 13 MMCFPD.

 

AAPG Search and Discovery Article #91004 © 1991 AAPG Annual Convention Dallas, Texas, April 7-10, 1991 (2009)