In June 2018, Vertechs ULIA wellbore strengthen material was applied to a HTHP well in Gaomo block, Sichuan. With this application, drilling operators were able to successfully penetrate the thief zone and drill 19,500 ft to the design depth with another 980ft extension.
Potassium polysulfide water-based mud system was used to drill the reservoir at downhole temperature of 285 degF. Frequent mud leakage was encountered during the drilling of offset wells in the same formation layer. Loss of circulation materials were used to treat mud loss while drilling but result was below expectation. On-site test results show ULIA is compatible with the mud system. With 3.5ppb ULIA added, the invasion depth on sand bed was decreased from 5.9” to 1.8”, the thin filter cake holds pressure up to 725 psi after ULIA added (Tested by HPIT invasion tester). To conclude, drilling operators successfully drilled thru the thief zone and reached TD 20,480ft without any losses or wellbore instability issue.