Conceptual Model At Raft River Geothermal Area (1988)

GEOTHERMAL ENERGY

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Exploration Activity: Conceptual Model At Raft River Geothermal Area (1988)

Exploration Activity Details
Location	Raft River Geothermal Area
Exploration Technique	Conceptual Model
Activity Date	1988
Usefulness	not indicated
DOE-funding	Unknown

Exploration Basis

Use geophysical logs to determine the reservoir transmissivity

Notes

Seven fracture orientation sets are recognized in the sedimentary and metamorphic rock units. Although the conventional geophysical logs showed good lithological correlations among the five deep geothermal wells, individual fractures observed using the borehole televiewer logs can be not be traced from well to well. Interpretation of temperature logs, drilling rates and fracture intensity and characteristics indicates that most of the geothermal inflow occurs from three producing zones in each deep geothermal production well. The producing zones are associated mainly with steeply dipping fractures. Single-well pumping tests performed in the site indicate that plots of drawdown per log cycle of time versus discharge rate are nonlinear for each well. This suggests that the calculated values of transmissivity using the single-well pump test data may not represent the actual transmissivity of the reservoir. The multiple-well pumping tests indicate that the geothermal reservoir is anisotropic with transmissivity ranging from 11,200 gpd/ft to 23,900 gpd/ft.

References

• Rashrash, S. M.   (1 January 1988) Fracture characteristics and their relationships to producing zones in deep wells, Raft River geothermal area