Flow Measurements and Transport of Temperature-Responsive Hydrogel Microspheres for Use in Subsurface Flow Management

Abstract

Enhanced Geothermal Systems (EGS) offer a globally scalable option to increase the energy production from Earth’s internal heat. Their growth potential, however, is limited by financial risks imposed by uncertain subsurface reservoir conditions, especially the spatial distribution of fluid flow paths in fracture-dominated reservoirs. Recent work by the co-authors suggests that flow paths can be hydraulically controlled by introducing an “active” tracer that selectively swells and jams cooled regions of the reservoir thus redirecting fluids to hot regions and increasing production well temperatures. Here, we investigate the behaviour of these novel, micron-sized hydrogel microspheres passing through channels with temperature below the volume-phase-transition temperature. Specially, we were interested in seeing if they can be used to reduce short-circuited flow paths when microgel volume fractions are below and at the conditions necessary for jamming. Flow resistance effects were observed by injecting microgels into a bench-scale microfluidic setup simulating an EGS reservoir. Measurements of the pressure drop, fluid density, and mass flow rate at specified temperatures and microgel volume fractions were performed to estimate the resulting frictional power loss after a volume of the microgel injectate had migrated into the system. The data acquisition over time allows us to see if the injection conditions yield jamming. If jamming was not observed, the estimated friction power loss can be correlated with microgel volume fraction and temperature to evaluate the effectiveness of the microgels in resisting flow.