Heat Sensitive Epoxy Foam for Permeability Alteration in Fractured Geothermal Fields

Geothermal energy plays a growing role in the transition to renewable and carbon free energy sources. A challenge for many geothermal fields is how to enhance water-rock heat exchange either by creation of new fractures, or by blocking short-circuiting large conduits. Here we report a novel approach for blocking large conduits (faults and large fractures) using heat sensitive epoxy resin foam designed to be transported as discrete resin droplets to specific regions that are then activated (foamed and cure) in-situ at targeted temperatures. In contrast with alternative methods for reducing geothermal rock permeability such as silicate gels or heat responsive polymer microbeads targeting small aperture fractures < 0.1 mm, the epoxy foam can reduce the permeability of fractures with apertures up to several millimeters. Results from laboratory 2-D glass fracture model provide insights by visualizing the transport phase and subsequent temperature-sensitive foaming and curing transformations with associated flow pathway blocking. Modeling results for transport and foaming in simple fracture networks considering rheological properties and foaming (volume expansion) behavior will be presented. On going activities of rheological resin characterization; tuning of the foaming-curing to different temperature ranges; and consideration of resin dispersion using small droplets for enhanced transport will be discussed.