Fluid reserves and the production of superheated steam from fractured, vapor-dominated geothermal reservoirs

Journal Article · Wed Nov 10 04:00:00 EST 1982 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JB087iB11p09329· OSTI ID:6630207

Pruess, K; Narasimhan, T N

Vapor-dominated geothermal reservoirs produce saturated or superheated steam, and vertical pressure gradients are close to vapor static. These observations have been generally accepted as providing conclusive evidence that the liquid saturation must be rather small (<50%) in order that liquid may be nearly immobile. This conclusion ignores the crucial role of conductive heat transfer mechanisms in fractured reservoirs for vaporizing liquid flowing under two-phase conditions. We have developed a multiple interacting continuum method (MINC) for numerically simulating two-phase flow of a homogeneous fluid in a fractured porous medium. Application of this method to reservoir conditions representative of The Geyers, California, and results from an analytical approximation show that, for matrix permeability less than a critical value (roughly-equal2.5 to 5 microdarcies), the mass flux of water from the matrix to the fractures will be continuously vaporized by heat transported due to conduction. This gives rise to production of superheated steam even when the matrix has nearly full liquid saturation. Simple estimates also show that heat-driven steam/water counterflow can maintain a nearly vapor static vertical pressure profile in the presence of mobile liquid water in a reservoir with low vertical matrix permeability. The implication of these findings is that the fluid reserves of vapor-dominated geothermal reservoirs may be larger by a factor of about 2 than has generally been believed in the past.

• Research Organization: Earth Sciences Division, Lawrence Berkeley Laboratory, Berkeley, California 94720
• OSTI ID: 6630207
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 87:B11; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
150100* -- Geothermal Energy-- Resources &amp; Availability
CRACKS
ENERGY SYSTEMS
ENERGY TRANSFER
EVAPORATION
FAILURES
FLUID FLOW
FRACTURES
GEOTHERMAL FIELDS
GEOTHERMAL SYSTEMS
GEYSERS GEOTHERMAL FIELD
HEAT TRANSFER
HEATING
HYDROTHERMAL SYSTEMS
NUMERICAL SOLUTION
PERMEABILITY
PHASE TRANSFORMATIONS
POROSITY
STEAM
SUPERHEATING
THERMAL CONDUCTION
TWO-PHASE FLOW
VAPOR-DOMINATED SYSTEMS