Key Technology and Industrial Application of HPHT Drilling and Completion in South China Sea

South China Sea is one of the offshore HPHT region, with the maximum 2.38 pressure coefficient, 480 degF bottom temperature and 50% CO2. The drilling and completion are challenging problems. This paper reviews the past 20 years' researches and practices in South China Sea HPHT area. Based on theoretical study, laboratory tests and site experiments, the project team has been working on solving problems of formation pressure prediction, wellbore integrity, testing and operation technology. The understanding and achievements are abundant. First, an accurate prediction method of multi-source abnormal pressure was built and a quantitative control drilling technique was developed, which helps relize continuous circulation in 0.01∼0.02 g/cm3 density window. Second, the "self-repair" HPHT cement slurry systems have been created and the multi-barrier wellbore integrity protection technology has been constructed to implement normal pressure in casing annulus. Third, an intrinsically safe testing system, which includes 7 major factors, was created. The safety of offshore HPHT testing can be guaranteed. Fourth, a water-based high temperature resistant drilling fluid and series acceleration tools were created, realizing the high-quality and efficient HPHT field operation. This series of technology has helped build China's first HPHT gas field and can be a reference for similar area.