Stanford Geothermal WorkshopFebruary 9-11, 2026

Multistage hydraulic fracturing in horizontal wells is a commonly used technique to enhance the permeability of unconventional reservoirs and enhanced geothermal systems (EGS). The U.S. Department of Energy’s FORGE (Frontier Observatory for Geothermal Energy) initiative is an EGS field laboratory in which multistage hydraulic fracturing is applied in horizontal wells with the objective of improving connectivity between injection and production wells. Several fracturing stages have already been carried out with satisfactory results. This paper presents a design and implementation of a new multi fracture stimulation concept for Utah FORGE. In the first section, a new stimulation stage is proposed in well 16A(78)-32 above the previously fractured Stage 9, at a measured depth (MD) of 8950ft. The stage includes three closely spaced clusters (3.5 m spacing), stimulated sequentially for 70, 80, and 90 minutes, respectively. The simulated fractures are oval-shaped and propagate primarily toward well 16B(78)-32, attributed to the prevailing stress gradient. Because of the tight spacing, significant shear deformation develops near the injection point and at fracture tips. This shear deformation is expected to increase fracture conductivity and promote wing-crack development, thereby improving fracture connectivity. Next, a sensitivity analysis is performed by circulating cold water through a three-fracture cluster to identify an optimal cluster spacing. Results indicate that thermal performance improves as fracture spacing increases; however, the injectivity index increases up to a spacing of 4 m and then decreases at 6 m. These findings highlight the need to balance thermal performance with injectivity when selecting the cluster spacing for the proposed stimulation design.

Topic: Enhanced Geothermal Systems