Real-Time Acid Treatment Performance Analysis of Geothermal Wells

Abstract

In the Salak geothermal field, a five well acid treatment campaign was conducted in 2008. The choice of candidate wells for stimulation was based on low production/injection capacity, flowing wellhead pressure below normal system operating pressure, and massive water-based mud losses while drilling the reservoir section. After the wells were selected, the treatments were designed as follows: 1) select the target intervals, 2) select the acids and additives for pre- and post-flush stages, and (3) identify the acid concentrations and volumes.

The performance of the acid treatments and the adequacy of the treatment design are conventionally evaluated by measuring injectivity before and after stimulation. Through this process, we can obtain quantitative evaluation of the treatment. However, with the existing practices we cannot assess on-site the change of well characteristics as result of acid stimulation.

In this study we applied real-time acid treatment performance analysis tools, which have proved to be effective in oil and gas reservoirs, to a geothermal reservoir, the Salak Field in West Java. We evaluated these methods to monitor time variant skin factor and/or injectivity change in the course of acid stimulation. The field data clearly depict skin factor evolution over time. By tracking the real-time performance, improvements for future acid treatment design were identified.