TitleUnderstanding Stimulation of Crystalline Rock: The EGS Collab Project
Timothy Kneafsey, PE, PhDStaff Scientist | Lawrence Berkeley National Laboratory
AbstractEnhanced or engineered geothermal systems (EGS) offer tremendous potential as an energy resource estimated in excess of 500 GWe, supporting the energy security of the United States. There are technological challenges associated with developing this resource including: (1) lack of a thorough understanding of techniques to effectively stimulate fractures in different rock types and under different stress conditions to communicate between multiple wells, (2) inability of techniques to image/monitor permeability enhancement and evolution at the reservoir scale at the resolution of individual fractures, (3) limited technologies for effective zonal isolation for multistage stimulations under elevated temperatures, (4) lack of technologies to isolate zones for controlling fast flow paths and control early thermal breakthrough, and (5) lack of scientifically-based long-term EGS reservoir sustainability and management techniques.
The EGS Collab project is utilizing readily accessible underground facilities to refine our understanding of rock mass response to stimulation at the ~10 m scale for the validation of thermal-hydrological-mechanical-chemical (THMC) modeling approaches. Additionally, we are testing and improving conventional and novel field monitoring tools. The EGS Collab project focuses on understanding and predicting permeability enhancement and evolution in crystalline rock, including how to create sustained and distributed permeability for heat extraction from the reservoir by generating new fractures that complement existing fractures.
We have planned three multi-test experiments to increase understanding of 1) hydraulic fracturing in Experiment 1 (under way), 2) shear stimulation in Experiment 2 (starting soon), and 3) other stimulation methods in Experiment 3. In each series of tests within an experiment, we perform modeling to support experiment design, and post-test modeling and analysis are performed to examine the effectiveness of our modeling tools and approaches. In so doing, we can gain confidence in and improve the array of modeling tools in use. To date in Experiment 1, we have performed several highly monitored hydraulic fracture stimulations, and will be proceeding to shear stimulation of natural fractures and fracture networks with increasing complexity.
BioTimothy Kneafsey P.E., Ph.D. is a Staff Scientist at Lawrence Berkeley National Laboratory serves as the Hydrocarbon Resources Program Lead. He has led, performed, and collaborated on numerous laboratory and field studies on processes affecting heat and mass transfer and phase change in fractured and porous rock. His fields of interest include geothermal energy including enhanced geothermal systems (EGS), CO2 sequestration, production of gas and oil from unconventional reservoirs, gas production from methane hydrate-bearing sediments, and radioactive waste disposal. He has authored or coauthored more than 50 peer-reviewed journal articles on these studies.