The Use of Surface Gravity Methods in Monitoring Subsurface Reservoir Changes, with Case Studies at Cerro Prieto, Mexico, and Heber, California
- Key words
- Exploration; General; USA; Mexico; California; Cerro Prieto; Heber; Geophysical Exploration; Gravity; Case Studies; Resource Assessment
- Location
- Cerro Prieto, Mexico; Heber, California; Imperial Valley
- Conference
- Geothermal Resources Council Transactions
- Year
- 1980
- Session
- Geophysical surveys; Gravity surveys; Subsidence
- Language
- English
Abstract
Precise gravimetry is useful for monitoring reservoir changes during geothermal production. Temporal gravity changes are due to mass and elevation changes; when leveling accompanies repeated gravity observations, mass and elevation factors are separable, and each can be quantified. Gravity monitoring must be initiated prior to production, since non geothermal changes are numerous and of large magnitude. Microgal are .05-.1 mgal in magnitude, depending on production. State of the art instruments are adequate, but several readings are required. Ongoing studies at Cerro Prieto show no significant changes in two years (confirmed by leveling); similar work has been started at Heber. Precisions range from 8-15 mirogals for both surveys.
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