Downhole Measurements and Fluid Chemistry of a Castle Rock Steam Well,The Geysers, Lake County, California

Abstract

Certain wells within The Geysers steam field have standing water columns either when first drilled or when produced at low flow rates. These water columns have been attributed by Lipman et al. (1978) to accumulation of water condensing in the well bore. Alternative explanations are that perched water bodies exist within the reservoir or that a deep water body underlying the steam reservoir has been tapped. A well in the Castle Rock field of The Geysers drilled by Signal Oil and Gas Company (now Aminoil, U.S.A.) with such a water column was sampled in 1976 for water, gas, and isotope chemistry in hopes of distinguishing between these possible origins; the results along with the well history and downhole pressure and temperature measurements are reported here.

The well is located in Lake County, California, in the central part of the Castle Rock field, 4.8 km west-northwest of the town of Anderson Springs. Drilling was started in mid 1970 on a ridge at an elevation of 700 m above sea level. Steam entries were encountered at depths (below land surface) of 1,899, 1,902, 2,176, 2,248 2,288, and 2,295 m; the total depth drilled was 2,498 m. Large volume water entries above 685 m were cased off to 762 m.