A Practical Application of Chloride Mass Balance Method to the Evaluation of a Geothermal Steam Gathering System in Indonesia

Abstract

A new geothermal power plant with an 85 MW generation capacity was built last year in Muara Laboh, West Sumatra, Indonesia. The double-flash geothermal steam generation system consists of two high pressure separators and one low pressure separator. As the performance of the separators is critical to the safe and efficient operation of the turbines, a testing program was developed and conducted to verify the performance of the separators.
A key indicator of separator performance is the steam dryness measured on the pipeline downstream of the separator. A natural tracer mass balance method is used to measure the steam dryness, with chloride selected as the natural tracer due to its abundance in geothermal fluids and being preferentially dissolved in brine rather than in steam.
Representative steam and brine samples were collected from steamline and brineline test points downstream of the separators and analysed for chloride and sodium in the laboratory. These chloride and sodium concentrations are used to calculate the steam dryness using a mass balance method. Special traversing isokinetic probes were developed and successfully used to collect representative steam samples in the tests.