Oil-Based Drilling Fluid Technology for Ultra-Deep Extended Reach Wells in East China Sea

Difficulties such as borehole wall instability, poor hole cleaning, drag encountered frequently during tripping due to high friction and torque, and difficult reaming, have been encountered in drilling operation in the Baoyunting block and the Pinghu block in east China Sea, which seriously affect the drilling efficiency. By analyzing the characteristics of the variegated mudstone formation, a technology using sized particles to achieve strong plugging was applied and the emulsification stability of the oil-based drilling fluid was improved to solve the problem of borehole wall instability. By optimizing the 6/3 r/min reading of the drilling fluid on six-speed viscometer, efficient cuttings carrying was achieved and the problem of hole cleaning in extended-reach well drilling in the East China Sea was solved. An independently developed lubricant LUBE OB was used to reduce the friction coefficient of the drilling fluid under high loads and the wear of drill strings and casings. This oil-based drilling fluid technology was successfully applied for the first time in drilling the 8000 m ultra-deep extended-reach well KQT-N. The oil-based drilling fluid has strong plugging capacity, high cuttings carrying efficiency and high lubrication performance, the use of which has reduced the time required for reaming in extended-reach wells in the East China Sea from 16.7% to 2.0%, greatly improving the drilling efficiency and providing technical support and guarantee for the safe and efficient development of the oil and gas fields in the East China Sea.