Speaker
Description
Geothermal energy is a critical application of subsurface utilization, offering a sustainable and renewable energy source. However, its widespread development faces significant challenges, particularly related to the high permeability of subsurface reservoirs. This characteristic often leads to non-ideal flow zones that hinder efficient heat extraction and reservoir performance. To address this issue, we are investigating using thermally degradable microcapsules to deliver high temperature nano-modified polymers to modify the permeability of larger, problematic fractures. For these materials to be effective, their transport behavior and tunable properties must be demonstrated experimentally and validated numerically before field-scale implementation.
We have developed a high-temperature high-pressure flow loop for injecting microcapsules into a porous network for 3 days at ~100 ˚C. We injected fluorescent polyethylene microcapsules into gravel matrices - simulating subsurface porous structures - while varying parameters during testing such as injection fluid viscosity, gravel size, and microcapsule properties. The results indicate that the microcapsule dimensions and densities allow for them to both flow into permeable zones and become trapped at certain points in the rock matrices. We observed that carrier fluid viscosity, microcapsule size, and gravel size all had effects on the quantity of microcapsules that became trapped in our samples versus flowing through the sample without trapping. We also used CT scanning to show that in most cases the microcapsules either completely passed through the gravel sample or sealed the near-entrance pore spaces. These tests complement ongoing tests using fractures to determine the relationship between the transport of microcapsules and fracture characteristics (aperture size, roughness, etc.). In addition, numerical models were developed to simulate how the physical properties of the microcapsules resulted in bridging and trapping and expand upon the microcapsule transport and trapping in alternate scenarios, such as fractured zones or more tortuous pore networks.
Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA-0003525. This presentation describes objective technical results and analysis. Any subjective views or opinions that might be expressed in the paper do not necessarily represent the views of the U.S. Department of Energy or the United States Government. SAND2025-00007A
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