Structural Optimization Design of Modular Double Drill Pipe

Abstract

Aiming at many drilling blocks with pore pressure coefficient ≦1.05 in China (shale gas surface layers in Tarim Basin and Sichuan Basin, depletion of reservoirs and gas reservoirs in developed oil and gas fields in China), the narrow window of drilling fluid density in such blocks will directly lead to wellbore instability, difficulty in carrying rock debris and serious formation losses. In order to control the fluctuation range of formation pressure, on the basis of conventional managed pressure drilling technology, gas lift positive circulation drilling technology and Marine double gradient drilling technology are integrated to form gas lift positive circulation drilling technology. The double drill pipe is one of the key equipment to realize the above drilling technology. Under this background, a double drill pipe for gas lift positive circulation drilling technology is designed. In this paper, the key equipment of gas lift positive circulation drilling technology is analyzed and its structure is optimized.