Development of Fluid Flow Control Technology Using Thermoresponsive Gel

Abstract

In geothermal development, localized fluid flow within reservoirs leads to heterogeneous temperature distributions and uncurtains extraction of geothermal resources. This reduces overall heat extraction efficiency and hinders stable steam production. To address issue of localized fluid flow, we propose a novel flow control approach using a thermoresponsive fluid whose properties change with temperature. This functional fluid responds to local temperature of reservoir, promoting uniform flow distribution, homogenizing the temperature field, and enabling stable steam production. A thermoresponsive gel that shows a remarkable increase in hardness upon heating has recently been developed. Its Young’s modulus rises to 1800-fold before and after the transition. At the injection of this functional fluid as slurry to reservoir, the gel remains soft near the low-temperature region around the injection well. In contrast, under higher temperature conditions, the gel hardens. This causes flow paths plugging through bridging and interlocking of solid particles. Consequently, the flow can be redirected toward low-permeability zones. This redirection leads to a more uniform temperature distribution. Such fluid flow control is expected to improve heat extraction efficiency and stabilize steam production. This study experimentally evaluates the feasibility of this idea. To evaluate the plugging performance under different gel hardness states at room and elevated temperatures, we conducted flow tests in an artificial fracture under confining pressure with a slurry containing thermoresponsive gel particles, which particle size satisfied bridging conditions. The slurry was injected into flow model while injection pressure and cumulative discharge were measured. At elevated temperature, an early pressure rise was observed, while at room temperature, the pressure increase was slower. These results indicate that the hardened gel plugged flow paths more rapidly and resisted fluid pressure better than the soft state. In summary, the thermoresponsive gel shows potential for reservoir flow control. Future work will include flow tests involving multiple flow paths with different permeabilities to evaluate the feasibility of fluid flow control.