Developing High Resistant Cement Systems for High-pressure, Hightemperature Applications

Abstract

Abstract Worldwide growing in hydrocarbon demand is driving the oil and gas companies to explore areas with more hostile conditions, such as high-pressure, high-temperature conditions. By increasing the number of projects in these conditions improved technology, material selection and testing procedures are required to overcome the challenges. One of the main reasons, causing the cement systems to fail in these environments, is concentration of stresses inside the wellbore induced by downhole changes of temperature and pressure. Therefore the objective of this work is to develop a high resistant cement system. The stress resistant cement systems in this study are produced by adding silica sands and silica flour to the dry cements. To study the effect of temperature and pressure on strength properties of set cements all samples are cured at elevated temperatures and pressures. Also the effect of curing time on the strength properties are investigated. The results show that the developed cement systems with silica flour show more strength properties, due to its microstructure properties. In these cement systems, the number of cracks and micro fracture are less than the systems with silica sand due to the fine particles size of silica flour. The cracks and fractures inside the failed set cement systems serve as pathways for formation fluids to the surface, and thus reducing the life of the well. Increasing the concentration of silica sand and silica flour will increase the strength properties but at the same time it strongly affects the other properties of cement slurry. So additives have been used to adjust other essential properties of cement systems.