| Abstract |
A pilot project has been initiated at the Awibengkok (aka Salak) Geothermal Field that investigates the applicability of fluid inclusion gas analyses for exploration and development of geothermal fields. Fluid inclusion gas analyses are widely used in the oil and gas industries as an exploration tool using borehole profiles of fluid chemistry for delineating reservoir compartmentalization and fluid contacts but the application to geothermal systems has not been thoroughly tested. An initial fluid inclusion study in Awibengkok was conducted in 2011. Fluid inclusion gas chemistry from seven edgefield wells was reviewed and correlations extracted in this initial analysis. This study adds the fluid inclusion gas chemistry from five wells within the Awibengkok reservoir. The goal of this study was to discover definitive chemical relationships in fluid inclusion gases that distinguish zones above or within the reservoir compared to outside or peripheral to the reservoir. Ratios of gases on ternary plots and groupings on histograms were used to distinguish between areas of the Awibengkok reservoir. Methane decrement in ratios of methane-hydrogen and methane-carbon dioxide appears to be associated with regions above or within reservoir compared to chemistry of fluid inclusions at similar depths outside or peripheral to the reservoir. In addition, fluid inclusion gases inside or above reservoir show consistently tighter groupings between Air-ASW on the N2-CO2-Ar ternary plot compared to outside the reservoir. The results from this study suggest these three chemical “signals” are associated with fluid inclusion gases in rocks above the Awibengkok geothermal system. As a test of these correlations, a similar study will be undertaken at the Darajat Geothermal System. Preliminary results from fluid inclusion gas chemistry from within and above the reservoir compared to edgefield and outside the reservoir warrant more detailed review focusing on individual host minerals, relationships to measured temperatures and, for potential exploration applications, chemical differences referenced to location relative to an active geothermal system. |