| Title | Study of Foam Fracturing for Enhanced Geothermal Systems Using Model Material |
|---|---|
| Authors | Hong WANG, Jy-An John WANG, Yarom POLSKY, Fei REN, Haoqi LI, Virensinh THAKORE, Jiaxin XI |
| Year | 2020 |
| Conference | Stanford Geothermal Workshop |
| Keywords | foam fracturing, pulsed injection, waterless, EGS stimulation, cement |
| Abstract | Foam fracturing has been considered as a potential technical approach to address water concerns with hydraulic fracturing in the development of enhanced geothermal systems (EGS). In many EGS sites, the water required for the hydraulic fracturing is either unavailable, extremely costly or environmentally undesirable. This paper presents work performed in the first year of a project sponsored by the U.S. DOE GTO Waterless Stimulation Initiative that investigates the foam fracturing as an alternative approach to the hydraulic fracturing. One element of this work explores foam formulations that are suitable for EGS conditions. A separate paper submitted to this workshop covers this work. This paper describes the development of an experimental setup for studying the potential application of foam fluids for hydraulic fracturing along with enhanced fracture efficiency through cyclic pressurization. The system is equipped with pulse rate automation, dual pulse valves for enhanced pulsation amplitudes, and other functions. It can perform static injection at a pressure rate, and pulsed injection at specified pulse size and rate. Both single-phase and foamed fluids can be used. Initial experimental results of foam fracturing using cement as a model material will be reported. Cement material was fabricated with a water to cement ratio 1:1 in various sizes of cylinders. The cylindrical specimens were cured to a pre-determined age and then prepared with a central blind borehole drilled along the axis of the cylinder. The blind borehole specimens were tested without axial loading and confining pressure at room temperature. Water and N2-in-water foam were studied as the fracturing fluids. The foam had 52 to 70% quality and used 0.4 wt. % alfa olefin sulfonate (AOS) as a surfactant. The observations from the experimental work will be presented and discussed. |