Controlled Retardation of Sorel Cement Using Sodium Salicylate for Lost Circulation Control in Naturally Fractured Reservoirs

Summary Sorel cement has emerged as an effective solution for controlling severe leakage during drilling in fractured formations. However, it can thicken prematurely under high-temperature and high-pressure (HTHP) conditions in the wellbore, leading to operational risks, such as pipe sticking and pressure trapping. Sodium salicylate (SS) has been identified as a potential retarder for Sorel cement, but its effectiveness and retardation mechanism remain unclear. In this study, we investigate the effects of SS on the physicochemical properties, hydration process, and microstructure evolution of Sorel cement, with particular emphasis on its retardation mechanism. The results show that SS effectively prolonged the setting time and shortened the interval between initial and final setting. At an optimal dosage of 17%, the atmospheric and HTHP thickening times were extended to 200 minutes and 237 minutes, respectively. The consolidated cement exhibited a plugging pressure resistance of more than 18 MPa (fracture widths of 4–10 mm) and an acid dissolution rate above 95%. SS also reduced the temperature peak and heat release rate, altered the hydration kinetic model from the nucleation and crystal growth (NG), phase boundary reaction (I), and diffusion (D) stages to the NG-D model, and modified the morphology and composition of hydration products. The retardation mechanism was attributed to the adsorption and complexation of SS, forming platy magnesium salicylate crystals that temporarily hinder hydration. These findings provide mechanistic insight into the retardation behavior of SS, which helps improve the formulation of Sorel cement for extended safe drilling operations.