| Abstract |
This paper will discuss the simulation and possible deployment of the three-component Vertical ElectroMagnetic Profiling (VEMP) borehole magnetic field measurement tool at the Utah FORGE site with the goal of characterizing the size and porosity of the stimulated geothermal reservoir. The VEMP tool contains a three-component magnetic field sensor with primary sensitivity between 1 and 128 Hz, and was specifically designed for high temperature borehole deployment and subsurface imaging in geothermal wells. The first high temperature test involved a successful deployment in a geothermal well in Kakkonda, Japan ( Miura et al., 1996), before being deployed in a well at Dixie Valley, Nevada (Wilt et al., 1997). LBNL recently received funding as part of the Utah FORGE project to refurbish the tool and if modeling proves sensitivity to the stimulated volume is sufficient, deploy it at the FORGE site just prior to and after the main stimulation / flow test in mid-to-late 2023. The VEMP tool was shipped from a GERD storage facility to LBNL in early 2022 where the sensors and high temperature vacuum dewar that protects the tool electronics were determined to be working, and an interim analogue acquisition system designed and implemented. In parallel to this tool refurbishment, an electromagnetic numerical modeling study was initiated to determine if there is enough sensitivity to the stimulated zone to warrant deployment at FORGE. The resistivity model uses a 3D MT inversion result (Wannmaker et al. 2020) as the base model, and an estimated 1% porosity increase within a 400m wide by 500m high stimulated reservoir zone as determined from discreet fracture network modeling by Xing et al (2022). Though a number of source-receiver configurations will be examined in the modeling study, the most promising configuration involves electrically energizing the steel well casing of the deviated injection and/or production wells, and deploying the VEMP tool towards the bottom of two nearby monitoring wells. This talk will provide an synopsis of the original VEMP construction and testing, recent modifications to and testing of the tool, and an overview of the numerical EM acquisition design study. REFERENCES Miura, Y., Osato, K., Takasugi, S., Muraoka, H., and Yasukawa, K., 1996, Development of the Vertical Electro Magnetic Profiling (VEMP) Method; Journal of Applied Geophysics, 35, 191-197. Wannamaker1 P, Simmons, S Miller, J., Hardwick, C., Erickson, B., Bowman, S., Kirby, S., Feigl K and Moore, J., 2020, Geophysical Activities over the Utah FORGE Site at the Outset of Project Phase 3. PROCEEDINGS, 45th Workshop on Geothermal Reservoir Engineering Stanford University, Stanford, California, February 10-12, 2020 SGP-TR-216 Wilt, M., Takasugi, S., Uchida, T., Kasameyer, P.,Lee, K., and Lippmann, M., 1997, Fracture Mapping in Geothermal Fields with Long-Offset Induction Logging, Proceedings: Twenty-Second Workshop on Geothermal Reservoir Engineering, Stanford University, Stanford, California, January 27-29,1997. Xing, P., Damjanac, B., Radakovic-Guzina, Z., Torres, M., Finnila,A., Podgorney, R., More, J., and McLennan, J., 2022, Numerical simulation of stimulations at the Utah FORGE site using the designed pumping schedules; Proceedings of the Geothermal Rising Conference, Reno, Nevada, August 29-31, 2022, pp 618-628. |