Research on the Suitability of High-Density Leakage Plugging in Offshore High Temperature and High Pressure Wells

A large number of fractured formations are developed in the high-temperature and high-pressure formations of the Yingqiong Basin in the South China Sea. During drilling, the risk of lost circulation is ex-tremely high, which will cause complex downhole accidents and seri-ously affect the drilling speed.In order to realize safe and efficient plugging of HPHT Wells, the following studies are carried out in this paper: Firstly, the characteristics of leakage, types of leakage and plug-ging and prevention mechanism of HPHT formation in Yingqiong Ba-sin are clarified based on core and indoor rock mechanics experiments. Secondly, a simulated plugging evaluation device with high tempera-ture resistance of 180 °C and high pressure resistance of 20Mpa was in-vented and applied to accurately evaluate the reservoir leakage behav-ior in Yingqiong Basin. Finally, a series of anti-high temperature plug-ging agents adapted to different loss types are systematically selected for the first time for different formation fracture types and the plugging effect is evaluated. In this study, through mechanism research, device research and development, accurate evaluation, the shaft wall pressure equivalent increased to 0.1g/cm3 without leakage. It provides technical support for the subsequent ultra-high temperature and high pressure stratum with weak leakage and narrow pressure window.