Clay stabilization in sandstone reservoirs and the perspectives for shale reservoirs

This study presents a comprehensive review of clay stabilizers and updated understandings of their mechanisms on stabilizing clay minerals in improved and enhanced oil recovery (IOR and EOR) applications. First, formation damage mechanisms related to clays in conventional sandstone and shale reservoirs are briefly introduced. Then existing clay stabilizers, including simple inorganic salts, inorganic polymers, acids, alkalis, simple organic salts, organic polymers, oligomers, nanoparticles, cationic surfactants, and organosilanes, as well as their characteristics, are summarized. In addition, we elucidated the common experimental techniques used for clay stabilization evaluation. Each category of clay stabilizers, experimental studies, field practices, and lessons learned in the past few decades are then critically reviewed and assessed in-depth, based on which advantages and disadvantages of all these clay stabilizers are explicated and compared as instructive guidelines for proper stabilizer selection and future applications. Finally, we discussed clay stabilization involved in shale reservoir development that recently came into view and pointed out directions deserving future studies. Identification of clay induced formation damage as well as clarification of reservoir rock and fluid properties is the prerequisite for screening and developing clay stabilizers. To select clay stabilizers and optimize project design, it is necessary to evaluate their performance by experiments on preserved reservoir cores. This will allow for treatment upscaling and effectiveness prediction.