1.College of Petroleum Engineering,China University of Petroleum(Beijing), Beijing , China; 2.Institue of Resources and Enviroment,Henan Polytechnic University,Jiaozuo,China

In order to solve the problem that conventional pipe string of T-shaped horizontal well of coalbed methane can’t be driven in and realize screen completion and well flushing operation, the feasibility of the T-shaped horizontal well flexible screen pumping process is discussed, and the technical mechanism of flexible screen pipe pumping process is emphatically studied. Based on the principle of down-hole pipe piston and the mathematical model of pipe string, the double-layer structure design of flexible pipe string is proposed to form the method of T-shaped horizontal well flexible screen pumping method. Based on the T-shaped horizontal well string mechanics and well structure characteristics, the flexible string was optimized.The parameters of flexible screen tube were designed in combination with the control mechanism of pulverized coal and the principle of coalbed methane production and the flexible screen was tested to resist the external load strength by the flat plate external load test. For the first time in the world, the special tools and process design for flexible pipe stringing were completed, and a complete flexible screen completion string pumping process was formed. The results show that with the diameter of 112 mm hole and the curvature radius of 1.8 m, the flexible completion string pumping down process can be used to push down the flexible screen pipe with the diameter of 63 mm. The double-layer flexible pipe string was kept in the stretching state during the downward drilling process.In the extended state, no spiral bending occurs, and the screen body does not undergo plastic deformation, which solves the problem of the T-shaped horizontal well screen of the coalbed methane. Through special pumping down tools and double layer pipe string structure, the integration of screen pipe down and well washing operation can be realized so that the drilling fluid damage to the reservoir can be eliminated and the single well productivity can be improved.

国家科技重大专项资助项目（2017ZX05064002）;国家自然科学基金联合基金资助项目（U1762214）