Reservoir Response to Production: Castle Rock Springs Area, East Geysers, California, USA

Abstract

Steam deliverability of the original 20 wells, supplying steam to Unit 13 power plant, has undergone five different decline trends since unit's start up in May 1980. High decline rates after 1984 were influenced by the regional effects associated with the installation of new capacity in the adjoining areas totalling 383 in 1983-84 and 347 NMW in 1985-86. Unit 13's production declined Harmonically for the first 6.6 years, near exponentially for the next year and hyperbolically to harmonically thereafter. Near exponential decline trend resulted from the combined effect of local and regional pressure drawdowns and an accelerated makeup well drilling program. Analysis of the decline rate versus generating capacity suggests that a sustainable 2 per month decline is achievable if the capacity is held at about 160 NMW in the Unit 13-16 wellfield and 830 NMW The East Geysers.