Limit analysis of extended reach drilling in South China Sea

Extended reach wells (ERWs), especially horizontal extended reach well with a high HD (horizontal displacement) to TVD (true vertical depth) ratio, represent a frontier technology and challenge the drilling limitations. Oil and gas reservoir in beaches or lakes and offshore can be effectively exploited by using extended reach drilling (ERD) technology. This paper focuses on the difficult technological problems encountered during exploiting the Liuhua 11-1 oil field in the South China Sea, China. Emphasis is on investigating the key subjects including prediction and control of open hole limit extension in offshore ERD, prediction of casing wear and its prevention and torque reduction, ϕ244.5mm casing running with floating collars to control drag force, and steerable drilling modes. The basic concept of limit extension in ERD is presented and the prediction method for open hole limit extension is given in this paper. A set of advanced drilling mechanics and control technology has been established and its practical results are verified by field cases. All those efforts may be significant for further investigating and practicing ERD limit theory and control technology in the future.