(GP/GT) for Additional Water Supply in the Lower Rio Grande

III-25
III. B-3
TIIERMAL ENHANCED OIL RECOVERY
USING GEOPRESSURED - GEOTIIERMAL FLUIDS
Concept and Methodology
The concept of GP/GT TEOR is very simple. Geopressured-geothermal reservoirs contain high pressure,
high temperature, and usually, gas saturated brine. The concept is to use these fluids to recover oil from
a shallow reservoir found structurally above the geopressured-geothermal reservoir. The high pressure
of the GP/GT reservoir compared with the low pressure of the target reservoir allows moving the fluid
to the target reservoir simply by pressure differential. The high temperature of the brine will heat the
oil in the target reservoir and thus reduce its viscosity to a level where it can be pumped. Thus, viscosity
reduction techniques have made the greatest contribution to EOR when compared with other tertiary
recovery processes especially when considering the efficiency of recovering heavy oil. The explanation
is seen in the temperature - viscosity - oil gravity relationships. Hence, the advantages of using the
GP/GT fluids in TEOR are as follows:
• A source of high temperature water
• Internal drive method determined by the pressure differential that will pump the GP/GT
brine hydraulically into the target reservoir.
• No emissions from the burning of crude oil.
• No outside use of fresh water.
• Possible use of natural gas from the GP/GT fluids to drive surface equipment.
PROCESS FEASIBILITY
Three steps are important in proving the GP/GT TEOR technology. The first step in proving the
technology is a co-Iocational analysis to find suitable GP/GT and target reservoirs. Analyses are being
undertaken by The University of Texas at Austin for Texas heavy oil fields; and, by Louisiana State
University for Louisiana heavy oil occurrence. As an example, a test field (AI worth Field) has been
proposed for Texas and is available as part of an industry cost-sharing proposal with Fanion Production
Company. The target reservoir is the Cole Sandstone, at a depth of 1,000 ft. The field is presently
marginally economical and is currently producing about 20 bpd (8°API) from five producing wells. The
viscosity of 18° API gravity oil can be reduced from about 100 centipoise at a temperature of 90"F (32°C)