Optimised chemical cleaning of geothermal wells: A laboratory study

Abstract

The chemical cleaning of geothermal production and reinjection wells is a helpful maintenance activity in treating formation 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. While we have had several successful chemical workovers of both production and reinjection wells in recent years, there have also been scenarios where the uplift was not as expected, or the recovery was short lived. In an effort to explain the behaviour we have observed, we have undertaken a thorough laboratory study to understand the efficacy of the chemicals typically used to chemically clean 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. These baseline results have given us valuable 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 and formations and discusses the implications of the results for future well workovers.