Study on the Mechanism of Salt Crystallization in the Wellbore During the Lifting Process of High-Mineralization Oil Wells

Salt precipitation and wellbore blockage have been observed during well testing and production in certain wells of the Mahu Fengcheng Formation reservoir in Xinjiang Oilfield, significantly impairing normal production and hindering cost-effective development. To address the unclear composition and scaling mechanisms of salt deposits, an integrated analytical approach incorporating oilfield water chemistry analysis, X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS) was employed. The results confirmed that sodium bicarbonate (NaHCO3) constitutes the primary component of the scale, originating from both the high-salinity formation fluids and abundant alkaline minerals characteristic of the Fengcheng Formation. During production operations, continuous decreases in wellbore temperature and pressure substantially reduce sodium bicarbonate solubility, ultimately inducing its crystallization and progressive accumulation that leads to wellbore obstruction. Based on comprehensive scaling mechanism studies, targeted mitigation strategies including wellbore thermal insulation and hot water dilution were developed. These technical solutions provide critical support for optimizing production efficiency in the Mahu Fengcheng Formation reservoir.