Stanford Geothermal WorkshopFebruary 9-11, 2026

Market demand for geothermal energy is rapidly escalating globally, largely due to the need for 24/7 electrification of power grids as well as policy changes toward decarbonization and GHG (greenhouse gas) reduction. An example feasibility study is presented that focuses on viability for heat and power generation. The study applies a streamlined workflow for evaluating the feasibility of repurposing late-phase or abandoned oil and gas sites for geothermal energy production to a case study in the southern United States. The initial phase of the workflow is Site Screening where Play Fairway Analysis (PFA) is used to down se1ect from five areas of interest to two based on: 1) lowest risk geology; 2) highest potential heat; 3) data rich areas; 4) existing grid connections; and 5) market demand. This initial project phase includes the development of site geomodels consisting of a structural and stratigraphic model, geomechanical model, temperature model, natural fracture assessment, and geochemistry. The initial phase incorporates the conceptual design of optimal well trajectories and stimulation zones to access the target heat source. Steps in the second phase of the study, Pre-Feasibility, were then applied to the two down-selected sites. In the second phase steps 1) fracture data are used to generate numerical Discrete Fracture Network (DFN) models; 2) hydraulic stimulations designs are developed to model hydraulic fracturing of intact rock or Enhanced Geothermal Systems (EGS) and alternatively hydroshearing of preexisting natural fractures; 3) the EGS and DFN models are upscaled to a gridded 3D permeability field; 4) resource potential and production forecasting of heat and minerals is performed using Reservoir Dynamic Modeling including sensitivity scenario testing of model uncertainty space; and 5) a preliminary Economic Analysis is performed which includes surface plant conceptual design, data requirements for the Basis of Design for drilling and completing the wells, drilling engineering design with risk analysis, well design time and cost estimate of DFN/EGS/AGS options, and a preliminary economic assessment for the Levelized Cost of Electricity (LCOE). In the final study phase, Feasibility, further down selection is performed to choose the site with the highest performance capacity and lowest LCOE. The base geomodel, DFN models, and well designs, are used to conduct full-physics 3D multistage EGS stimulation modeling. In this step we simulate coupled thermo-hydro-mechanical behavior of the fracture networks with 1) hydraulic fracture stimulation with no preexisting fracture network, and 2) hydraulic fracture stimulation through preexisting fracture networks to simulate reservoir injection, production and thermal output over 30 years. The results of the full-physics based refined Reservoir Dynamic Modeling is then used to update the techno-economic analyses. This study presents the full link between subsurface characterization and dynamic modeling of natural and induced fracture networks to assess geothermal potential at a prospective site. We show the potential of EGS locating sites in South Texas by drilling to ~5 KM and that their relative LCOE is highly dependent on subsurface conditions. Key findings are 1) production wells must be positioned above stimulated injector to exploit the vertical growth of hydraulic fracture into regions of lower stress magnitude. 2) preexisting natural fracture networks enhance thermal output; 3) well separation has a significant impact on thermal output with respect to hydraulic fracture length distribution (or stimulation zone for natural fracture scenarios) and 4) zonal isolation (flow conformance) significantly improves thermal output for hydraulic fracture cases.

Topic: Modeling