Enhanced Geothermal Systems

Multistage fracturing is a breakthrough for EGS - dramatically improving energy production per well

ResFrac's fully-coupled fracturing and reservoir simulator is ideal for simulating hydraulic fracturing and long-term circulation in multistage EGS designs

Fracture propagation

3D fracture initiation and propagation, interaction between wells, stress shadowing, proppant transport, complex fluid additives and non-Newtonian flow, diverters, and wellbore dynamics.

Fracture reopening during circulation

Ability to simulate the mechanical opening of fractures, and the associated increases in fracture conductivity, induced by cooling during long-term fluid circulation.

Decision support tools

NPV maximization using ResFrac's economics engine and cloud-based optimization tools.

The ResFrac team offers authentic, deep expertise in multistage fracture design optimization and Enhanced Geothermal Systems

Fervo Energy engineers use ResFrac to develop breakthrough EGS stimulation designs, enabling Project Cape record-breaking flow rates exceeding 100 kg/s per well, a 3x improvement on the previous ‘best ever.

What are Enhanced Geothermal Systems?

Source: SMU Dedman College of Humanities & Sciences Geothermal Lab

Enhanced Geothermal Systems use hydraulic stimulation to produce from high-temperature, low permeability resources

Geothermal production potential is huge across the United States and globally. However, production is limited by insufficient natural permeability in most resources. Analogous to the shale revolution, EGS promises to unlock these resources by enabling much higher flow rates and low power costs.

Multistage stimulation resolves the problems that have historically limited EGS performance

Traditional EGS designs have been performed in a single stage, without proppant. These designs suffer from flow localization, where the fluid flows into a relatively small number of flowing pathways. In formations lacking large, naturally conductive faults, these designs have suffered from insufficient unpropped conductivity. Shale-style ‘plug and perf’ limited-entry completions with resolve both of these problems.

Key technical references

Almarri, M., M.J. AlTammar, G. Fowler, and K. Alruwaili. Utilizing Thermally Controlled Fluid to Improve Cluster Uniformity and Efficiency. SPE Unconventionals Conference in the Middle East.

Fowler, G., and M. McClure. 2021. A Feasibility Study on Three Geothermal Designs: Deep Closed-Loop (with and without Conductive Fractures) and Open-Loop Circulation Between Multifractured Laterals. GRC Transactions.

Li, T., S. Shiozawa, and M. McClure. 2016. Thermal breakthrough calculations to optimize design of a multiple-stage Enhanced Geothermal System. Geothermics.

McClure, M. 2023. Technical Barriers for Deep Closed-Loop Geothermal. This article was originally posted as a ResFrac blog post, and published on arXiv in March 2023.

McClure, M. 2023. Thermoelastic fracturing and bouyancy-driven convection- Surprising sources of longevity for EGS circulation. This article was originally posted as a ResFrac blog post, and published on ArXiv in August 2023.

McClure, M. 2023. Calibration Parameters Required to Match the Utah FORGE 16A(78)-32 Stage 3 Stimulation with a Planar Fracturing Model. Fourty-Eigth Workshop on Geothermal Reservoir Engineering, Stanford, CA.

McClure, M. 2021. Guest Editorial: Why Multistage Stimulation Could Transform the Geothermal Industry. Journal of Petroleum Technology.

McClure, M. 2012. Modeling and characterization of hydraulic stimulation and induced seismicity in geothermal and shale gas reservoirs. PhD Thesis, Stanford University.

McClure, M., and R. Horne. 2011. Investigation of injection-induced seismicity using a coupled fluid flow and rate/state friction model. Geophysics.

McClure, M., and R. Horne. 2014. An investigation of stimulation mechanisms in Enhanced Geothermal Systems. International Journal for Rock Mechanics and Mining Sciences.

McClure, M., R. Irvin, K. England, and J. McLennan. 2024. Numerical Modeling of Hydraulic Stimulation and Long-Term Fluid Circulation at the Utah FORGE Project. Fourty-Ninth Workshop on Geothermal Reservoir Engineering, Stanford, CA.

McClure, M., C. Kang, and G. Fowler. 2022. Optimization and Design of Next-Generation Geothermal Systems Created by Multistage Hydraulic Fracturing. SPE Hydraulic Fracturing Technology Conference and Exhibition.

Norbeck, J., M. McClure, and R. Horne. 2018. Field observations at the Fenton Hill enhanced geothermal system test site support mixed-mechanism stimulation. Geothermics.

Shiozawa, S., and M. McClure. 2014. EGS designs with horizontal wells, multiple stages, and proppant. Thirty-Ninth Workshop on Geothermal Reservoir Engineering, Stanford, CA.

Singh, A., G. Galban, M. Mcclure, K. Briggs, J. Norbeck. 2025. Designing the Record-Breaking Enhanced Geothermal System at Project Cape. Unconventional Resources Technology Conference.

Wang, Z., M. McClure, and R. Horne. 2009. A single-well EGS configuration using a thermosiphon. Thirty-Fourth Workshop on Geothermal Reservoir Engineering, Stanford University.

Recent content from the ResFrac blog

Production impact of horizontal fractures

At the 2025 SPE International Hydraulic Fracturing Technology Conference, we (Dontsov, Zoback, McClure, and Fowler) presented “Hydraulic Fracture Propagation Along Bedding Planes Might Be More Prevalent Than We Think” (SPE-226637). The paper reviewed case studies with evidence of horizontal or bedding plane fractures from microseismic, fiber optics, core observations, and casing deformation.

Testing the new Kryvenko model for proppant washout

What controls proppant placement during hydraulic fracturing? As described in Chapter 8 from McClure et al. (2025), ResFrac incorporates a variety of physical processes – viscous drag, gravitational settling, hindered settling, clustered settling, bed slumping, and more. In addition, ResFrac accounts for the complex physics associated with proppant flowing out of the wellbore (Dontsov, 2023; Ponners et al., 2025).

$Horizontal fracture initiated along weak bedding plane or frictional interface in ResFrac$

Horizontal hydraulic fractures in ResFrac

Horizontal hydraulic fracture propagation is believed to be widespread in shale plays where the frac gradient approaches the overburden – such as the Vaca Muerta, Utica, and Montney. However, horizontal propagation is nearly always ignored in hydraulic fracture modeling. In ResFrac, we are obsessed with ‘getting the physics right’, and so naturally, we extended our simulator to handle horizontal fracturing. The first version of this new capability was released earlier this year. We are eager to start collecting feedback from users, which will help us to fine tune the algorithm and workflow.