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NEGUS-DE WYS, J., and C. E. KIMMELL, no affiliation given

ABSTRACT: The Geopressured Habitat and Possible Recovery of Oil with Geopressured-Geothermal Fluids

The characteristics and occurrence of geopressured-geothermal (GPGT) reservoirs are discussed. Causal agents and relation to sedimentary depositional environments and heat flow are presented. Global reports of occurrence are reviewed. Thermal enhanced oil recovery (TEOR) using geopressured/geothermal fluids is a unique concept for recovering heavy and medium oils that are bypassed during conventional production processes. The successful implementation of this technology would provide an environmentally clean and less expensive method of thermal recovery as opposed to the burning of crude oil or natural gas used widely by industry at the present time.

The GPGT fluids are under high pressure in their parent reservoir and when linked to shallow reservoirs by suitable plumbing will provide a self propelled method of heat transfer to a target reservoir existing at shallower depth. The GPGT fluids will heat the reservoir as in conventional TEOR. This will reduce the residual oil saturation and lower the viscosity of the oil so that it can be moved more easily and in greater amounts.

The method is similar to hot water flooding and thus the basic technology already exists. However, the major difference is the usually high total dissolved solids present in GPGT fluids. The exact effect of the brine on the target reservoir is uncertain but may have a beneficial effect not only on viscosity and oil extraction

but also on permeability and porosity (Negus-de Wys, in press). The operational and mechanical problems associated with piping the GPGT fluids into shallow reservoirs also are uncertain but probably can be readily overcome. The important point is that an enormous amount of additional domestic heavy and medium oil will be recovered if the concept works. GPGT fluids combine the temperatures, propulsion, and technology that would be comparatively clean environmentally.

The major states from which considerable quantities of additional productions are possible are California (42 Bbbls), Alaska (25 Bbbls), Arkansas, Louisiana, and Texas (6 Bbbls each), Wyoming (5 Bbbls), and 2 Bbbls in other states. The leading basins for application of the technology in the United States include the Gulf Coast Basin, the San Joaquin Basin, and the Los Angeles Basin. Totals for these basins are: 8.134 Bbbls of medium oil and 42.3g Bbbls of heavy oil.

An example in the south Texas Mirando Trend is discussed. The temperatures of the upper Wilcox GPGT fluids in this region range from 350 to 500 degrees F, and salinities in the range of 3600 to 70,000 mg/E. The pressures are from 800 to 3500 psia flowing wellhead pressure. The target reservoirs for injection of the GPGT fluids are the Jackson and Yegua sandstones of the late Eocene Epoch. These reservoirs contain an estimated 4 million bbls of heavy oil in place (OIP [18(approx.) API]) of which at least 1 million bbls could be recovered by TEOR. An additional 1.5 Bbbls of oil is recoverable from the 87 fields within the Mirando Trend.

Geopressured-Geothermal basins have been identified world wide by Fertl, Hunt, Powley, Bradley, Amoco Production and others (Negus-de Wys, in press). Where collocation of geopressured-geothermal fluids with medium to heavy oil exists, there is the potential for recovering the oil using the geopressured hot fluids.

AAPG Search and Discovery Article #90988©1993 AAPG/SVG International Congress and Exhibition, Caracas, Venezuela, March 14-17, 1993.