Development of Multi-Stage Fracturing System and Wellbore Tractor for Zonal Isolation During Stimulation Processes in Horizontal Wells Intended for EGS Operations – Lessons Learned for Development of Next Generation Fracturing Systems

This paper describes lessons learned from the $5.3 million, three-year DOE funded project to develop a novel array of multi-stage hydraulic fracturing tools for zonal isolation for construction and control of a subsurface heat exchanger addressing Enhanced Geothermal Systems (EGS) at the Utah-FORGE site. The lessons learned from the Utah-FORGE project provide a basis for the development of second-generation stimulation and conformance control systems. The development and testing of the sleeve component with separate Seal Drag and Collet Test Fixtures were successful. The Collet testing for the sleeve actuation and ball pass system was in good agreement with finite element analysis, mechanical pull testing, and a 4-day flow testing at numerous rates and pressures. The seal drag testing was performed with a variety of seal configurations with a drag goal of less than 500 pound axial force at 440°F, with 2,000 psi differential pressure. However, the final System Integration Test (SIT) ultimately failed prior to reaching stimulation pressure of 8,500 psi. The failure was due to conflicting demands on the elastomeric seals during actuation (i.e., dynamic seal movement) and static pressure loading of stimulation pressure. In the paper, we will also present the results of tractor assembly and testing—consisting of the first package drive section, pressure balance and temperature/pressure sub sections, latch and sleeve actuator, load testing of anchor assembly, tool electronics section, final System Integration Test (SIT), and demonstration at geothermal conditions. Despite shortcomings in the project results, the lessons learned from this project led to the development of a much simpler sleeve and actuation system that will be presented. An economic model (Mays et al, 2024) was developed and used to quantify the value of conformance control which considerably improves total power generation. Our model was applied to published field data from Project Red using Gringarten's model. The model indicated that lack of conformance control would lead to short-circuiting and a premature thermal decline, generating 35% less power during the projected 30-year plant life with similar results at superhot conditions. In addition, we conducted reservoir analysis and modeling which led to great insight into Utah-FORGE and Project Red EGS projects. In essence, this paper will describe improvements in the tools, implementation, and heat extraction methods that will be needed to achieve an economically successful EGS. The second-generation tools addressed in the paper will provide a viable alternative to "Plug-and-Perf" to achieve a cost-effective subsurface heat exchanger.