Thermal depletion of a geothermal reservoir with both fracture and pore permeability

Technical Report · Tue Aug 10 04:00:00 EDT 1976

DOI:https://doi.org/10.2172/5321874· OSTI ID:5321874

Kasameyer, P W; Schroeder, R C

A method for estimating the useful lifetime of a reservoir in porous rock where the injection and production wells intersect a fracture system is presented. Equations were derived for the pore-fluid and fracture-fluid temperatures averaged over large regions of the geothermal field. Problems such as incomplete areal sweep and interfingering of cool and hot fluids are ignored. Approximate equations relating average temperatures to the heat flowing from rock to fluid were developed, and their use is justified by comparing the results with solutions of the exact equations. The equations for the temperature decline can be solved quickly. In the model, fractures are characterized by three parameters: aperture w, permeability k/sub fr/, and spacings between fractures D. For certain values of these parameters, cool reinjected fluid in fractures may reach the production wells long before all the warm pore fluid has been tapped, shortening the useful lifetime of the field. The traditional (and important) problems of reservoir engineering, flow rate determination, drawdown, sweep patterns, etc. were ignored. Thus the results are most useful in providing a correction factor which can be applied to lifetime estimates obtained from a detailed simulation of a field assuming porous rock. That correction factor is plotted for clean fractures (k/sub fr/ = w/sup 2//12) as a function of w and D for several lifetime ranges. Small-scale fractures seen in cores from the Salton Sea Geothermal Field are too closely spaced to reduce lifetime estimates. However, large-scale fault systems exist within that field, and they are attractive drilling targets because they produce large flow rates. If large scale faults communicate between injection and production wells, they may reduce the useful lifetime of those wells.

• Research Organization: California Univ., Livermore (USA). Lawrence Livermore Lab.
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 5321874
• Report Number(s): UCRL-77323
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
150201 -- Geology & Hydrology of Geothermal Systems-- USA-- (-1989)
150904* -- Geothermal Engineering-- Geothermal Reservoir & Well Performance
DIAGRAMS
ENERGY LOSSES
ENERGY TRANSFER
EQUATIONS
FAILURES
FLUIDS
FRACTURED RESERVOIRS
FRACTURES
GEOLOGIC FAULTS
GEOLOGIC STRUCTURES
GEOPHYSICAL SURVEYS
GEOTHERMAL FIELDS
GEOTHERMAL FLUIDS
GEOTHERMAL SYSTEMS
GEOTHERMAL WELLS
Geothermal Legacy
HEAT FLOW
HEAT LOSSES
HEAT TRANSFER
INJECTION WELLS
LIFETIME
MATERIALS
POROUS MATERIALS
PREDICTION EQUATIONS
RESERVOIR ROCK
ROCKS
SALTON SEA GEOTHERMAL FIELD
TEMPERATURE MEASUREMENT
WELLS