Optimising the Cleaning of Geothermal Wells Through Laboratory

Abstract

The cleaning of geothermal production and reinjection wells is a helpful maintenance activity in treating formation and wellbore scale. Removal of this troublesome scale can be used to maximise generation, increase the useful life of wells and defer the drilling of new wells. As the opportunity to conduct field trials is limited and costly, we have undertaken a thorough laboratory study to understand the efficacy of the chemicals typically used to remove scale from geothermal wells and find the optimal chemical mix for both production and reinjection wells. We employed a systematic, statistical experimental design approach to allow testing of a range of variables and chemical types in the smallest number of experiments possible. This work builds on baseline laboratory testing conducted previously, which has given us further insight into the optimal chemical selection for production and reinjection wells to provide the best chance of success when applied in the field. This paper summarises the results of several hundred experiments across different scale types, formations and fluid types and discusses the implications of the results for future well workovers. We also present some initial field results from formation cleans conducted following our laboratory work.