Increasing the reliability of oil and gas well fastening with polycomponent plugging systems

Purpose. Development of effective composite plugging systems for reliable fastening of oil and gas wells in difficult mining-geological conditions of deposits of Ukraine. Methods. The proposed research is based on an analytical and industrial study of the problems of the well construction and fastening in the conditions of chemogenic deposit occurrence when applying the analysis of geophysical research materials. The research of tamponage solutions and buffer liquids was carried out using standard devices and methods that meet the set of requirements for testing cements and technological systems for well construction. Processing of research results was carried out in MATHSAD and EXCEL. Composite cement CEM V according to the European standard EN 197-1, tamponage cement 1-G, krents - high-basic C2F CaSO4 and low-basic 3(CF) CaSO4 calcium sulfoferites were used for the research. Findings. It was established that the basic plugging material, as well as technological solutions for fastening wells in difficult mining-geological conditions, do not ensure compliance of the well as an engineering structure with operational reliability indicators. As a result, violations in the fastening system are quite often recorded, which require significant time and financial costs for their elimination, and sometimes lead to well liquidation. In order to increase the reliability of fastening wells, it is necessary to use multi-component tamponade systems modified by krents. Calcium sulfoferrite admixtures have been proved to accelerate the kinetics of early strength and contribute to the formation of cement stone with improved characteristics. The need to use effective buffer systems to improve the quality of fastening is substantiated. Originality. On the basis of assessment, systematization and detailed study of geophysical material and features of well fastening under the conditions of exposure to chemogenic sediments, the necessity of using composite plugging material was established. The conducted studies have proved that to ensure reliable fastening of wells in difficult mining-geological conditions, it is necessary to use multicomponent composite plugging material modified by calcium sulfoferites with accelerated kinetics of early strength, which form cement stone with a densely packed structure. Practical implications. Based on the industrial material evaluation and detailed laboratory studies, technological solutions have been developed to increase the reliability of well fastening due to the introduction of multi-component composite plugging material modified by krents and buffer liquids.