The Role of Decline Curve Analysis at The Geysers
- Key words
- Reservoir Engineering; USA; California; Lake; The Geysers; Mass Withdrawal; Depletion; Decline Curve; Reserve Estimates; Forecast; Permeability; Haromic Decline; Exponental Decline; Fetkovich Method
- Location
- The Geysers, California
- Conference
- Geothermal Resources Council Transactions
- Year
- 1989
- Session
- Production decline; Reservoir modeling
- Language
- English
Abstract
Recent increases in mass withdrawal rates as new power plants went on production at the Geysers have complicated standard decline curve analysis and associated reserve estimates. This paper demonstrates a method of calculating reserves using Fetkovich type curves to aid in proper application of harmonic and exponential decline equations where significant steepening in flow rate trends occurred between 1985 and 1988. However, extrapolation of production data during this transient decline condition may present conservative reserve estimates. Actual remaining reserves per well are thought to be between 2.7 billion (exponential) and 7.9 billion (harmonic) pounds of steam. The permeability thickness (kh) calculated from the Fetkovich type curve equations compare favorably with kh values calculated from long term pressure buildup analyses.
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