Development and research of the properties of sealing grease for threaded connections of casing pipes

The tightness of threaded connections in casing is a critical issue, as it directly affects the reliability of well casing and, consequently, their trouble-free and long-term operation. Given that the oil and gas industry is tasked with maximising the energy demand by its own production, this problem remains relevant. The aim of this study was to investigate the properties of a newly developed sealing grease for threaded connections in casing pipes and to confirm its effectiveness compared to other commercially available products. Analytical and experimental methods were used to conduct the research. Industrial material was analysed for the quality of well casing and it was revealed that numerous wells exhibited defects in their casing associated with the leaks of threaded connections of casing pipes. The causes of threaded connection failure were classified and the main factors affecting their tightness were identified. A sealing grease was developed, consisting of carbamide resin, organophilic aerosil, graphite, fumed silica and ammonium chloride. The following indicators were determined to evaluate the effectiveness of the developed grease: friction coefficient on the steel-steel surface, adhesion strength, grease shear resistance, tightness of the threaded connection during internal pressure testing, and coefficient of performance. It was established that the proposed grease has a higher initial adhesion force than others, and it also increases steadily during the polymerisation process and reaches its maximum value after fifteen hours of curing; the grease has a lower coefficient of friction, higher shear resistance and a significantly higher efficiency factor. The studies confirmed an increase in the performance of threaded connections of casing pipes using the developed lubricant