Mixing‐Induced Mineral Precipitation in Porous Media

Abstract

Injectivity decline during brine reinjection poses a significant challenge in the geothermal industry, with reported cases of substantial injectivity reduction and in severe cases, complete well shutdown. Among the reasons behind these issues, chemical processes play a key role due to potential changes in the fluid properties throughout the operation cycle. When reinjected, the fluid with altered chemical composition mixes with in situ fluids, potentially triggering mineral precipitation, which can obstruct flow and reduce injectivity. To better characterize the mechanisms behind the mixing-induced mineral precipitation processes, we performed a series of core-flooding experiments combined with high-resolution imaging techniques. Our study focuses on the direct visualization of barite precipitation fronts in Berea sandstone and characterizes their spatial and temporal evolution under varying flow conditions. Pressure response and time-resolved 2D scanning were analyzed to capture real-time changes in the system, whereas post-experiment micro-CT scanning, electron microprobe analysis, and mass spectrometry were employed to examine the morphology and distribution of the mineral deposits. Our results highlight the critical role of flow velocities on the kinetics of mixing-induced precipitation and demonstrate how mineral accumulation may significantly reduce permeability. These findings provide valuable insights into the dynamics of mineral precipitation in porous media, highlighting the impact of flow conditions on formation damage in geothermal systems.