Scaling Potential Analysis Along Production Wellbore in Awibengkok Geothermal Field Indonesia

Abstract

The combination of pressure and temperature drop with boiling and degassing contributes to mineral scaling formation in the geothermal wellbore. The formation of mineral scaling decreases the flow rate of geothermal wells by clogging boreholes and surface equipment. Since scaling remediation effort is highly dependent on the chemistry of geothermal water, a geochemical assessment is required to support it. This study aims to perform geochemical modeling to identify the potential and rate of scale formation in the Awibengkok Geothermal Field. An advection simulation is made using PHREEQC by utilizing published water chemistry and well pressure-temperature data. The result from the modeling shows the following at depth shallower than 1000 m: i) increase in species concentration due to boiling except for Na++K+ and Cl-, ii) the drop in pH and saturation index (SI) of calcite, aragonite, and amorphous silica, and iii) calcite and quartz as potential scaling mineral determined by equilibrium phase calculation. Maintaining temperature between depth of 1000-0 m show that pH, SI of potential scaling mineral, and the amount of possible calcite precipitate can be controlled throughout the wellbore, while possible quartz precipitate is reduced with the maximum amount occurring at a depth of 800 m.