A History of Tracer Studies of the East Flank Area of the Coso Geothermal Field

Abstract

Multiple tracer studies of the East Flank Area of the Coso Geothermal Field have been done over the last two decades. Comparisons of several tests and wells with multiple tests indicate returns from 2 days to 2 months with an average of 5 weeks for returns to production wells. The East Flank currently has four main injection wells, 56-16, 34-9, 34B-9 and 64A-16 that inject 1000 kph of brine. There are twelve two phase production wells. Residual tracer can be found in production wells two years after the addition of tracer with a baseline increase of 2-5 ppb. Virtually all test are brine phase tracers. The brine phase tracers used were Naphthalene Sulfonates. Fluid injection pressures do not exceed 250 psi. East Flank injection wells are not stepped out they are in close proximity to the production wells. Therefore connectivity studies have been made to estimate injection well to production well interconnectivity.