Property Effect and Mechanism of Sodium Salicylate on Magnesium-based Curing Plugging Materials

Abstract Lost circulation is a common problem in drilling and completion. Magnesium-based curing material has the advantages of effective plugging and formation damage control, and controlling curing time can extend the use. In this paper, the main agent of magnesium-based curing materials is magnesium salt, the influence of sodium salicylate with different dosage on the curing time in different curing states was analyzed, the optimal addition was determined, and the curing product and hydration process were analyzed under the optimal addition to determine the retarding effect of sodium salicylate. In static curing, the optimal addition of AR grade sodium salicylate was 15-17%, and the curing time was 3-4 h. The dynamic curing time at atmospheric pressure was obviously less than the static curing time, but clear right-angle thickening could be seen. The optimal addition of industrial grade sodium salicylate was 18%, and the static curing time was about 3 h. At high temperature and high pressure, it’s proved that pressure had little effect on curing time, but the curing time decreased significantly under high temperature environment. Through SEM, XRD and TGA, it was found that sodium salicylate was more conducive to the growth of the cured product, and more 517 phases was generated, but it did not affect the acid dissolution, with the acid dissolution rate reached more than 95%, which could realize the reservoir protection. By studying the hydration process, it’s showed that sodium salicylate could delay the hydration and reduce the heat release by about 2/3, and the hydration process was controlled by the phase boundary reaction. The retarding effect of sodium salicylate for magnesium-based curing material can guide the efficient application in different environments.