Enhancing the viability of calcite inhibition systems via targeted dose rate reduction

Abstract

Calcite scaling of Te Ahi Tamou (geothermal) production wells is an issue that requires ongoing attention and maintenance to maintain generation. Chemical cleaning is an important maintenance activity where the well is flashing in the formation, while broaching and live well cleanouts using air hammer are mechanical means to recover production when the scaling occurs within the wellbore. These methods have the limitation of accepting loss of production as the well scales up between interventions (Moya et al, 2005). Calcite inhibition systems (CIS) are a viable alternative that, when functioning correctly, remove the need for mechanical workovers and can maintain production without the need to accept productivity losses.
The installation of CIS on 13 of our production wells has been successful in allowing us to maintain a clear wellbore in wells that would typically have scaled up rapidly. As part of an ongoing optimisation of our systems, we have undertaken a targeted programme of work to optimise our chemical dose rates to reduce our operational costs and enhance the viability of installing CIS in further wells. This paper details the steps taken to reduce our chemical usage, while still maintaining clear wells. Dose rates have been tuned through assessment of chemical trends, comparison of calcite saturation of similar wells, analysis of operational data and through the use of an XY caliper tool to assess the effectiveness of reduced dosing rates. Analysis of this data has given us confidence that our targeted dose rate reductions have been successful and has allowed us to realise valuable operational savings that increases the appetite for future installations to maintain production for our wharehiko (geothermal power stations).