Center for Understanding Subsurface Signals and Permeability

The Center for Understanding Subsurface Signals and Permeability (CUSSP) is an Energy Earthshot Research Center with a multidisciplinary team that is working to develop the ability to predict and control fluid flow through fracture networks in enhanced geothermal systems, which is essential knowledge for meeting the Department of Energy’s Enhanced Geothermal Shot goals.

Graphic with Center for Understanding Subsurface Signals and Permeability (CUSSP) partner logos on the left and a generated image with data overlaid on a rock surface on the left

CUSSP is led by Pacific Northwest National Laboratory in partnership with Argonne National Laboratory, Clemson University, Colorado School of Mines, Lawrence Berkeley National Laboratory, Purdue University, University of California, Irvine, University of Illinois Urbana-Champaign, University of Maryland, and University of New Mexico.

Graphic showing the CUSSP approach to enhanced geothermal systems
CUSSP combines laboratory-based microscale to core-scale reactive fracture flow studies to inform experiments at an enhanced geothermal system testbed site, multiple time-lapse geophysical data streams collected simultaneously during chemically controlled fluid circulation experiments, and joint inversions of this data using physics-informed machine learning approaches. (Figure by Nathan Johnson | Pacific Northwest National Laboratory)

CUSSP is advancing a basic understanding of the complex chemical and physical processes that occur as fluids flow through the deep fracture networks in enhanced geothermal systems (EGS) and is developing methods to remotely sense and accurately simulate these processes across scales. In EGS, cold water pumped down a well flows through a network of fractures in hot rock and returns to the surface via another well as superheated fluid. By accessing this subsurface heat, EGS holds great promise as an abundant source of always-on energy. However, because of the high temperatures and pressures involved, the fracture networks at the center of these projects can change in ways that are currently difficult to predict, leading to loss of flow or circuit leakage. CUSSP is focused on solving the basic science problems underlying maintaining fluid flow and heat productivity in EGS for many years.

CUSSP researchers bring diverse expertise to tackle this large problem, with an approach that spans computations, laboratory-scale experiments, and a highly instrumented testbed site. The collaborations throughout the center will enable linking different phenomena across scales to observable geophysical data and characteristics at the testbed site. Combining experimental knowledge with machine learning will help enable more accurate predictions of the behavior underneath the surface in EGS. CUSSP is focused on filling the most important knowledge gaps needed to improve the accuracy of EGS reservoir simulations that are critical to minimizing long-term risks in EGS site selection, development, and maintenance.

The goals of CUSSP are only possible through an integrated team science approach. The Center is organized around two complementary scientific thrusts, which encompass detailed studies of flow processes across scales and settings.

Thrust 1: Micro- to Core-Scale Processes

Thrust 2: Field-Scale Assimilation and Validation

In addition to the two science thrusts, a cross-cutting theme runs through CUSSP research. This helps keep a focus on data integration and modeling across the center.

Cross-Cutting Theme: Modeling and Simulation

CUSSP will use an EGS testbed site at the Sanford Underground Research Facility (SURF) to conduct in-depth field studies in a controlled environment. Instrumentation at SURF can simultaneously collect multiple complementary geophysical sensing signals, enabling the team to monitor temperature, strain, and seismic activity under realistic conditions. CUSSP will also deploy innovative time-lapse 4D electrical resistivity tomography, developed by its team members, to derive insights into the different relationships between stress, porosity, and fluid chemistry.

Laboratory-based experiments will allow the CUSSP team to probe the fundamental geochemical and geophysical processes more deeply. These flow studies will use rocks from SURF to develop a precise understanding of the different chemical and physical changes that take place in EGS conditions. These details can help provide insight into the larger-scale processes and influence the development of future measurement techniques.

The data from both the laboratory and field site experiments will be used to train the deep neural networks needed for machine learning models. These models will help directly convert geophysical sensing data from the EGS site into information about the active chemical and physical processes. This represents a substantial departure from previous approaches to modeling EGS sites.

Through these efforts, the CUSSP team will help provide an innovative foundation for the development of future modeling approaches and technologies that couple high-precision observation and high-accuracy prediction of EGS reservoirs.

CUSSP is one of 11 Energy Earthshot Research Centers funded by the Department of Energy in 2023. These centers are focused on developing the solutions underlying the Energy Earthshots Initiative, aimed at spurring decarbonization efforts across the United States.