Lost circulation materials for deep and ultra-deep wells: A review

The number of deep wells and ultra-deep wells drilled worldwide is gradually increasing, and the problem of deep well leakage has become one of the challenges in drilling. The high-temperature and high-pressure environment in deep formations severely test the drilling leakage control. The lost circulation material and its nature largely determine the success rate of deep well leakage control. The paper discusses the failure and instability mechanism of the lost circulation materials in deep wells and the plugging zone formed by them. The lost circulation materials are classified as physical and chemical lost circulation materials. It includes bridge plugging materials, high filtration loss plugging materials, organic gel plugging materials, expansion plugging materials, resin plugging materials, and inorganic gel plugging materials. According to the published evaluation and analysis of temperature and pressure resistance of leakage lost circulation materials, the characteristics of different types of temperature and pressure resistance leakage lost circulation materials are summarized. Based on a large number of existing researches and the practice of the team on high temperature and high-pressure leakage plugging, the research on the theory of high temperature and high-pressure leakage plugging and the research adaptability of high temperature and high-pressure resistant materials, the research on new physical and chemical temperature and pressure-resistant materials, the composite leakage plugging method and its suitability Prospects are put forward in terms of temperature and pressure plugging technology and strive to improve the success rate of loss control in deep wells.