| Title | High-Temperature Stability of Aqueous Foams as Potential Waterless Hydrofracking Fluid for Geothermal Reservoir Stimulation |
|---|---|
| Authors | Virensinh THAKORE, Fei REN, Haoqi LI, Josh VOYTEK, Jiaxin XI, Hong WANG, Ji-An WANG, Yarom POLSKY |
| Year | 2020 |
| Conference | Stanford Geothermal Workshop |
| Keywords | Foam fluid, high temperature, stability, cross-linker, nanoparticles |
| Abstract | Hydraulic fracturing is a process of fracturing rock formation with water based fracturing fluids. In Enhanced Geothermal System (EGS) hydraulic fracturing is carried out by injecting high pressure cold water into the Hot Dry Rocks (HDR) under carefully controlled conditions. The fracturing fluid used for fracturing is an important component for EGS, not only concerning the technical characteristics but also environmental impact. Recent research has been carried out to develop waterless fracturing technologies for EGS, including foam-based hydrofracking. Foam fracturing fluids have potential benefits over water-based fluids in consideration of water consumption, less damage in water sensitive formations and less liquid to recover and handle after fracturing process. One task of implementing foam fracturing in EGS is to achieve foam stability at high temperatures, which is known to decay with increasing temperature. This research is focused on the stability of foam-based fluid at high temperature. A laboratory apparatus has been constructed for measuring foam stability at a temperature range from 23°C to 200°C. The apparatus is equipped with a foam generator, pressure tank, gas cylinders (N2 or CO2) or compressed air, flow meters, high temperature view cell, and portable microscope. The foam stability was evaluated with respect to the foam drainage, where foam height was measured as a function of time. The half-life of each testing condition was calculated as the indicator of stability. Four commercial surfactants with various concentrations in water (0.1 to 1wt. %) were investigated including alfa olefin sulfonate (AOS-40), sodium dodecyl sulfate (SDS), tergitol (NP-40) and cetyltrimethylammonium chloride (CTAC). Two different gelling agents, guar gum and bentonite clay (0.25 to 0.36% wt. %), were also studied respectively. Effect of silica nanoparticles (size 60 nm to 150 nm, 0.01 to 0.5 wt. %) and graphene oxide (GO) dispersion (0.4 wt. %) on foam stability were also tested. Finally, borate cross-linked fracturing fluid solutions were prepared and tested at high temperature. Preliminary results on the effect of the foam composition and temperature will be explained and discussed. |