_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper URTeC 4245311, “Designing the Record-Breaking Enhanced Geothermal System at Project Cape, ” by Ankush Singh, SPE, ResFrac, Gerame Galban, Fervo Energy, and Mark McClure, SPE, ResFrac, et al. The paper has not been peer-reviewed. _ Enhanced geothermal systems (EGS) seek to use hydraulic fracturing to achieve high flow rates from wells drilled in formations with high temperature but low permeability. Project Cape in Utah is an ongoing EGS project with a planned capacity of 400 MWe. In an initial circulation test, the first production well drilled for the project flowed at more than 100 kg/s (54, 000 B/D), a record for an EGS project. In this paper, modeling work performed to design the fracturing treatment and spacing for the wells is described. Introduction In EGS, hydraulic stimulation is used to improve the flow rate that can be achieved through geothermal wells. The potential geothermal resource base is very large, but in most places, insufficient natural permeability exists to achieve economic flow rates. By providing the ability to consistently generate high flow rates, EGS can unlock these reserves and increase the amount of geothermal energy produced dramatically. Despite this promise, EGS has not yet been adopted widely. Recent EGS-stimulation projects have adopted shale-style high-density fracturing with cemented casing, plug-and-perforation with limited-entry completion, tight cluster spacing, and large proppant volumes. These designs achieve greatly improved performance over previous conventional approaches because unpropped fracture conductivity is unreliable and often low, while propped fractures can consistently achieve high conductivity. Additionally, multiple stages with zonal isolation and perforation pressure drop are capable of creating a large number of closely spaced fractures throughout a large volume of rock. In 2024, Project Cape in Utah used three 4, 700-ft laterals to achieve production rates exceeding 100 kg/s. Dozens more wells are now being drilled at Project Cape, with a targeted field capacity of 400 MWe. In the complete paper, the authors describe the sensitivity analysis performed in early 2024, before the first Project Cape wells. These sensitivities were performed to optimize stage design and well-spacing realizations. Methodology The simulations are performed with an integrated hydraulic fracturing and reservoir simulator. The simulator fully couples mass balance on fluid components, energy, fracturing-fluid additives, and proppants; momentum balance in the wellbore; fracture-to-fracture stress shadow calculations; and porothermoelastic stress changes from depletion. The simulator accounts for perforation pressure drop and crossflow outside the casing caused by flow through the annular region or from a longitudinal fracture. The fractures are meshed as true cracks, and fracture-mechanics calculations are used to predict fracture propagation and height growth. The full well life cycle of hydraulic fracturing and long-term circulation can be simulated in a single continuous simulation. When modeling was performed before the first Project Cape wells, calibration was possible from experience at Project Red and initial results from three unpropped stimulations that had been performed at the adjacent Utah Frontier Observatory for Research in Geothermal Energy project. Since the Cape wells were tested in 2024, the model has been further updated, based on comparison with the results. This paper focuses on the Project Cape modeling performed before drilling the first wells.
Chris Carpenter (Sun,) studied this question.