Challenges and Practice of Key Technologies for Ultra-Deepwater Drilling with Very Narrow Pressure Window in South China Sea

Abstract Qiongdongnan Basin has deep water and narrow pressure window in South China Sea. In the process of drilling, it is often accompanied by complicated conditions, such as gas invasion, well leakage and breath effect during drilling. Therefore, we have carried out long-term research and practice. According to SPP, dc index, drilling fluid displacement and density and so on, we established a real-time gas invasion early warning neural network model. We formed multi factor measures to prevent lost circulation during drilling. We have drilled more than 20 deep-water narrow pressure wells, and the success rate of drilling reached 100%. Key words: Ultra-deepwater drilling; Narrow pressure window; Gas invasion; Well leakage; Breathing effect