Induced Microseismicity in Geothermal and CO2-EOR Fields

TitleInduced Microseismicity in Geothermal and CO2-EOR Fields
Publication TypeConference Proceedings
Year of Conference2019
AuthorsHuang, L, Chen, Y, Fehler, M, Schoenball, M, Ajo-Franklin, J, Fu, P, Cladouhous, T, Czsoki, P, Kneafsey, T, Team, EGSCollab
Conference NameSociety of Exploration Geophysicists - Postconvention Workshop
Date Published09/2019
Conference LocationSan Antonio

Fracture stimulation in enhanced geothermal systems (EGS) and fluid injection/migration in geothermal or CO2-enhanced oil recovery (EOR) fields could induce microseismicity, which in turn can help image and characterize fracture/fault zones. We present some microseismic imaging results from geothermal fields, including the EGS Collab project site and a conventional geothermal field. The EGS Collab project is developing intermediate scale (~10-20 m) field test beds for fracture stimulation at the Sanford Underground Research Facility in Lead, South Dakota. The fracture stimulation methods and fracture monitoring and modeling tools developed during the EGS Collab project will be further evaluated at DOE’s Frontier Observatory for Research in Geothermal Energy (FORGE) project site located near the town of Milford in Beaver County, Utah. We detect and locate microseismic events recorded during fracture stimulations at the EGS Collab testbed in metamorphic, crystalline rock outside a drift at the depth of the 4850 ft at the Sanford Underground Research Facility. The microseismic imaging result helps constrain a more accurate geomechanics model. In a hydrogeothermal field, we find that seismicity increases dramatically when the reservoir is shut in (both injection and production). The events accompanying shutin occur preferentially in the producing portion of the reservoir. In addition, we present some microseismic imaging results from the CO2-EOR field at Aneth, Utah and Farnsworth, TX. We perform adaptive moment-tensor joint inversion of clustered microseismic events recorded using a single-borehole geophone array to improve the inversion accuracy, and directly image fracture zones around locations where microseismic events occurred. We find that CO2-injection-induced microseismicity can occurr either within, beneath or above the injection reservoir layer. These microseismic imaging results can help characterize the state of stress and predict the reliability of CO2 storage reservoirs.