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

ResFrac shows how buoyancy-driven convection and thermoelastic stresses can surprisingly improve thermal longevity.

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

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

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., 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.

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

Recent Recorded Talks on EGS and DFIT

Below are links to watch two recently recorded talks. The first was a presentation with ThinkGeoEnergy discussing the impressive results from Fervo Energy’s recent Project Red pilot. The second was a presentation with whitson summarizing the URTeC-2019-123 compliance method procedure for interpreting DFITs. If you are interested in either topic, please check them out!

Figure 1: Example of Scenario C-A: Clear contact point

Practical guidelines for DFIT interpretation using the ‘compliance method’ procedure from URTeC-2019-123

This blog post provides practical tips for interpreting Diagnostic Fracture Injection Tests (DFITs) using the ‘compliance method’ procedure initially developed by McClure et al. (2016) and refined in the paper URTeC-2019-123, which summarized results from a joint industry study performed with a consortium of operators. The results from McClure et al. (2016) demonstrated that common practices for stress estimation often underestimate the true magnitude of the minimum principal stress, a finding that has been subsequently been confirmed by direct in-situ measurements and laboratory experiments, as well as in the field measurements reviewed by McClure et al. (2016).

Figure 3: Flow distribution during long-term circulation with porothermoelastic stresses ‘turned on’

Thermoelastic fracturing and buoyancy-driven convection – Surprising sources of longevity for EGS circulation

To maximize value from an EGS system, we need to optimize flow rate, well spacing, and well configuration. These engineering decisions will make the difference between a money loser and a cash cow. I’ve recently run ResFrac simulations of long-term EGS circulation and observed some surprising and intriguing results.