The Feasibility of Recovering Medium to Heavy Oil Using Geopressured-Geothermal Fluids

NEQUS-DE WYS, JANE, EG&G Idaho, Idaho Falls, ID, C. E. KIMMELL, Fanion Production Company, San Antonio, TX, G. F. HART, Louisiana State University, Baton Rouge, LA, and M. M. PLUM, EG & G Idaho, Idaho Falls, ID

Thermal enhanced oil recovery using geopressured-geothermal (GPGT) 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.

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 shallow depth. GPGT fluids will heat the reservoir as in conventional thermal enhanced oil recovery. 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 waters. The exact effect of the brine on the target reservoir is uncertain, but it may have a beneficial effect not only on viscosity and oil extraction but also on permeability and porosity. The operational and mechanical problems associated with piping 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 production is possible are California (42 billion bbl), Alaska (25 billion bbl), Arkansas, Louisiana, and Texas (6 billion bbl each), Wyoming (5 billion bbl), and 2 billion bbl in other states. The leading basins for application of the technology in the United States include the Gulf Coast basin, San Joaquin basin, and Los Angeles basin. Totals for these basins are 8.134 billion bbl of medium oil and 4.239 billion bbl of heavy oil.

Alworth field of the south Texas Mirando trend is proposed as a pilot site. 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/L. The pressures are from 800 to 3500 psia flowing wellhead pressure. The target reservoirs for injection of the GPGT fluids are the upper Eocene Jackson and Yegua sandstones. These reservoirs contain an estimated four million bbl of heavy oil in place (18 degree API) of which at least one million bbl could be recovered by thermal enhanced oil recovery. An additional 1.5 billion bbl of oil is recoverable from the 87 fields within the Mirando trend.

Run of the economic model on the Alworth field suggests that it will be economic.

AAPG Search and Discovery Article #91007© 1991 AAPG International Conference, London, England, September 29-October 2, 1991 (2009)