Rheology and Flow Visualization of Temperature-Responsive Microgels and Their Potential for Geothermal Reservoir Management

Abstract

Geothermal energy remains a largely untapped natural resource for nations across the globe to increase their energy security and simultaneously reduce their carbon footprint. Enhanced geothermal systems have particularly amplified the potential for geothermal extraction in previously overlooked regions, but also present significant uncertainty with the inherent risk of premature thermal breakthrough. Previous reservoir simulations within our group have suggested a temperature-responsive change in fracture aperture to redirect flow around flow paths which are prematurely drained of their thermal energy can significantly boost system efficiency and life expectancy. Volume-phase transition microgels present a real-world implementation of this change in aperture through their ability to reversibly swell and shrink in response to temperature changes. A variety of synthesis inputs provide a control framework for particle mechanical properties, swelling ratio, and the volume-phase transition temperature. Here, rheometry combined with visualization techniques are performed to evaluate the potential for microgel usage in geothermal reservoirs by understanding the microstructure, macro-rheological properties, and velocity distribution of these microgel suspensions. In particular, we will demonstrate the ability of these microgel suspensions to reversibly form a yield stress fluid which can effectively plug and redirect flow through a change in the suspension’s solid volume fraction, which is inherently coupled with temperature.