EDA Renovaveis, S.A., operates two power plants that exploit the 240 degC liquid-dominated reservoir of the Ribeira Grande geothermal field on the island of Sao Miguel in the Azores archipelago. The two plants—Ribeira Grande and Pico Vermelho—have a combined capacity of 23 MW and presently generate 44% of the total electric energy consumption of the island and 23% of that of the archipelago.

In 2015 a tracer test using naphthalene sulfonate and disulfonate tracers was conducted to evaluate the hydraulic communication between the injection and production wells of the field. The main goal of the test was to verify the effectiveness of relocating injection in the Pico Vermelho sector, where earlier (2007–2008) tracer testing and numerical reservoir modeling had predicted severe cooling as a result of injection breakthrough.

The results of the 2015 tracer test, along with recent information provided by new wells, exploitation data, logging, testing, and sampling were used to update the numerical reservoir model and generate field-performance forecasts under the new injection configuration. The results indicate that cooling will be minimal under the current scheme of exploitation and that the reservoir can sustain an increase of generation from the Pico Vermelho sector and maintain the current output from the Ribeira Grande power plant for 30 years, with only about one makeup well needed.

To request abstracts or topics from previous years, please contact geothermexinfo@slb.com.