Permeability reduction in fractured geothermal field using heat-activated epoxy resin droplets: resolving droplet transport and adhesion dynamics

The performance of enhanced geothermal systems (EGS) depends critically on effective water–rock heat exchange. This often requires creation of new fractures, however, for certain scenarios, occluding short-circuiting high flow fractures is needed. Here we introduce an approach for reducing the permeability of large fractures using heat-activated epoxy resin foam. The resin is transported as discrete droplets that become thermally activates (foam, expand and cure) in-situ at a prescribed temperature range. We present modelling and experiments for the transport and adhesion characteristics of resin droplets that result in gradual permeability reduction in large aperture fractures (mm-cm scale). The coupled transport and adhesion of resin droplets is represented in a 2-D numerical model enabling quantification of changes in pressure distribution, flow pathways, and effective permeability. Droplet adhesion considers velocity perturbations coupled with Hertz–Mindlin contact mechanics for thermally activated chemical reaction kinetics. Model predictions show good agreement with laboratory-scale fracture experiments, demonstrating the capability of the proposed approach to capture key mechanisms governing resin sticking and permeability alteration in fractured rock.