Using Fluid Inclusion Stratigraphy Analyses to Distinguish Producing Wells from Non-producing Wells in the Coso Geothermal Field, California

Abstract

A method for using bulk fluid inclusion analyses performed on well cuttings is now being tested for possible use on geothermal wells. Similar analyses are used by the petroleum industry. Here we report preliminary results of this project - the use of fluid inclusion analyses to distinguish between producing and non-producing wells. Approximately 1,700 samples, from three producing Coso wells and one non-producing Coso well, were analyzed at a commercial laboratory, Fluid Inclusion Technology, in Tulsa, Oklahoma. Volatiles released from fluid inclusions in well cuttings crushed under vacuum were analyzed using mass spectrometry. Analyses of samples from producing and non-producing wells show distinct differences in relative concentration between select species including water, carbon dioxide, nitrogen, methane, and hydrogen sulfide, as well as the ratio of pentane/pentene. Water released during analysis of the non-producing well chips from all depths is about 2 orders of magnitude less than that from producing well chips. The low water yield is attributed to a low fluid inclusion density. Our preliminary results indicate that fluid inclusion analyses can readily differentiate producing wells from non-producing wells, and that this determination can be made before drilling is completed.