Description:

Coupled Processes Modeling in Energy Geosciences

Coupled thermal-hydro-mechanical (THM) processes modeling is indispensable for the design and performance assessment of energy geosciences activities, including nuclear waste disposal, hydrocarbon and geothermal energy exploitation, carbon sequestration, and subsurface storage. Coupled THM numerical models are most useful if can be validated against field observations at relevant spatial and temporal scales for the problem at hand. In this presentation, three examples of such large-scale model validations are presented. The model simulations were conducted with the TOUGH-FLAC simulator that was first developed and applied in the early 2000s associated with previous plans for a nuclear waste repository at Yucca Mountain, Nevada, U.S.A. At Yucca Mountain, coupled processes model validation was conducted against several underground experiments, culminating with the Yucca Mountain Drift Scale test, which still to date is the largest underground heating experiment in the world. Modeling of this experiment provided validation of the coupled THM model that was then applied for predicting the long-term (10,000 years) performance of the repository host rock. The processes modeling has also been extensively applied associated with geologic carbon sequestration. Here coupled THM modeling is important for evaluating the potential for leakage of CO2 through sealing rock formations and for evaluating the potential for induced seismicity. In this context, pioneering work was done associated with the In Salah CO2 storage project in Algeria. At In Salah, a TOUGH-FLAC coupled THM model was validated against field observations of ground surface deformation monitoring by satellite (InSAR) technology. Ground surface uplift could be detected from the underground CO2 injection taking place at 2 km depth and the magnitude and spatial extent of the surface uplift were correlated with reservoir pressure changes. However, detailed modeling of the observed ground surface uplift also revealed the development of a large scale fracture zone, about 5 km long, in the lower part of the caprock, which eventually lead to the termination of the project. The final example involves the Northwest Geysers Enhanced Geothermal Systems (EGS) Demonstration Project. This EGS demonstration project is located at the margin of The Geysers geothermal field, California; the largest geothermal energy producer in the world. The Northwest Geysers EGS Demonstration Project involved hydraulic simulation of a cubic kilometer sized rock volume during a one-year massive cold-water injection into the very hot >250°C steam field. The TOUGH-FLAC modeling of observed ground surface deformations and seismicity releveled a network of faults that is important to consider for evaluating the long-term production and sustainability of such an EGS. These three examples, along with numerous other studies, demonstrate the great benefits of effective coupled THM modeling that will be crucial for resolving the challenges of a fast growing demand for subsurface energy and storage.    

Bio

 Dr. Jonny Rutqvist is a Senior Scientist and Head of Hydrogeology Department, Energy Geosciences Division, at the Lawrence Berkeley National Laboratory (LBNL). He holds a PhD degree in Engineering Geology from the Royal Institute of Technology, Sweden. For over 30 years, Dr. Rutqvist’s research has been focused on geomechanics and modeling of coupled thermal, hydraulic, mechanical, and chemical (THMC) processes in geological media for a wide range of geoscientific and geoengineering applications, including geologic carbon sequestration, nuclear waste disposal, geothermal energy extraction, unconventional oil and gas, and underground energy storage. Dr. Rutqvist has authored over 200 peer-reviewed journal papers, and is a four-time recipient of the American Rock Mechanics Association (ARMA) Awards.