Plugging technology for HTHP wells in Western South China Sea

In the Yinggehai Basin, western South China Sea, the temperature of Huangliu Fm reservoirs in HTHP (high temperature and high pressure) wells is up to 200 ℃ and the reservoir pressure coefficient is 2.27. And circulation loss occurs frequently in the process of well drilling. The lost circulation operation on HTHP wells are faced with multiple difficulties, e.g. fewer high-temperature lost circulation materials, high risk of HTHP well control, high-difficulty control on rheological property of high-density lost circulation fluid and less experience. The reasons for circulation loss of HTHP wells and the previous control experience were analyzed. Then, the HTHP dynamic lost circulation device was used to optimize HTHP lost circulation materials and formulas to reach the pressure resistance of 20 MPa. By virtue of the lost circulation control while drilling and the lost circulation control under pressure, lost circulation operation was successfully completed in the actual HTHP wells by using high-temperature elastic lost circulation additive FLEX, combined with rigid lost circulation additive BLN and pressure-bearing lost circulation additive STRH.