Geothermal Systems

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Comprehensive Physical-Chemical Modeling to Reduce Risks and Costs of Flexible Geothermal Energy Production (CEC-EPIC)

California Energy Commission (CEC)

LBNL’s TOUGH family based tool for analyzing flexible mode geothermal production.

The Issue

The increased use of variable renewable energy (primarily wind and solar) increases the inherent variability and uncertainty in electricity demand and resource availability, and thus drives the need for operational flexibility of other renewable such as geothermal energy. Flexible-mode geothermal energy production may involve rapid changes in geothermal production, such as reducing the production by half within tens of minutes and after a few hours again restoring full production. Converting production from (steady) base-load to (variable) flexible production may result in significant changes to the system related to corrosion and mineral deposition (scaling) in wells, mechanical damage fatigue to well components or the reservoir. A better understanding of the impacts of flexible-mode production on the reservoir-wellbore system is needed to assure safe and sustainable production.

Technical Approach

In this project, LBNL develop modeling tools that will be tested and applied to comprehensively investigate the impacts of flexible-mode geothermal energy production on the many technical challenges that are also faced for base-load production, including wellbore and reservoir integrity, scaling and corrosion of wellbore and pipeline, and flow and transport under the influence of injection and production. The modeling tools will be based on components of LBNL’s existing suite of TOUGH family of codes for modeling multiphase and multicomponent fluid flow and heat transport in geological media. The relevant modules of the family codes to be utilized in this project include T2WELL for coupled reservoir-wellbore multiphase multicomponent flow and transport modeling, and TOUGHREAC for reactive transport modeling, all with TOUGH2 as the core simulator. The improvement of the modeling capabilities will include (1) coupling FLAC3D with T2WELL for thermal-hydrological-mechanical (THM) modeling in both reservoirs and wellbores, and (2) coupling numerical modeling of thermal-hydrological (TH) processes with analytical modeling of diffusion-type processes in matrix blocks in fractured reservoirs. This will provide the necessary tools for investigating all the challenges related to flexible-mode production by efficient and accurate modeling of key coupled processes in the reservoir and wellbore system. In this project, LBNL will apply the model tools to quantify reservoir-wellbore THMC processes during flexible-mode production pilot tests at the vapor-dominated geothermal system at Geysers Geothermal Field, California. Moreover, the modeling approach will be extended and applied to model flexible-mode production from liquid-dominated geothermal systems.

Funding

Funding for this project is provided by the California Energy Commission under the EPIC grant program (GFO-16-301) under agreement EPC-16-022, as part of Work for Others funding from Berkeley Lab, provided by the Director, Office of Science, of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.