Geochemistry Characteristic Monitoring at LHD-α, a Cyclic Geothermal Well in Lahendong Geothermal Field, Indonesia

Abstract

LHD-α is one of the latest drilled wells in Lahendong Field. A cyclical in production flow rate was observed during production test. The well has a sinusoidal trend in flow rate and enthalpy. At the top of the cycle, the well can deliver fluid with 47% of dryness and 1609 KJ/Kg enthalpy. Meanwhile, at the bottom of the cycle, the well only produces of fluid with 41% dryness and 1486 KJ/Kg enthalpy. Spinner result of this well implied that well is supported by multiple feed zones. Static temperature profile showed the differences temperature profile in each feed zone. The deeper feed zone is known as a cyclic liquid reservoir with temperature 250-260oC, and upper feed zone is a steam reservoir with temperature 310-320oC. In order to detailed characteristics of the well, flow measurement and complete geochemical sampling were carried out on the well in various production parameters. The chloride and silica content of the produced brine increased when the cyclic reservoir contributes. The concentration of total NCG decreased, which indicates the steam reservoir is diluted by low NCG liquid. That is also shown on CH4-H2-H2S diagram where the sample dragged to CH4 apex. The result of these observations is expected to investigate the causes of cyclic production of this well. Moreover, the optimization strategy to utilize this well can be carried out.