Mitigating clay swelling and permeability loss in thermal EOR with a quaternary ammonium clay stabilizer under high-temperature low-salinity conditions

Clay swelling and fines migration pose significant challenges to thermally enhanced oil recovery (EOR) operations, particularly in clay-rich formations. This study systematically investigates clay swelling behavior and permeability impairment under high-temperature, low-salinity (HTLS) conditions and evaluates various inhibition methods to mitigate formation damage. To ensure realistic analysis, data and materials from a field with similar issues in Kazakhstan were used. Static/dynamic swelling tests demonstrated that a quaternary ammonium-based inhibitor consistently provided superior clay stabilization through effective ion exchange and surface charge modification mechanisms. In distilled water at 100 ℃, inhibitor-treated samples maintained 48.89% of their original permeability, while untreated samples exhibited severe damage, retaining only 17.05%. Additionally, this chemical inhibitor significantly lowered the critical salt concentration (CSC), effectively stabilizing clay at 4920 ppm salinity compared to 7380 ppm required without treatment. Scanning electron microscopy (SEM) imaging corroborated these results, revealing that inhibitor-treated clay maintains a compact and coherent structure, in stark contrast to the pronounced swelling, delamination, and structural deterioration observed in untreated clay samples. Nevertheless, this quaternary ammonium-based clay stabilizer presents a robust and promising solution for reducing clay swelling-induced damage, sustaining reservoir permeability, and improving thermal EOR performance in swelling-prone formations.