Analysis of factors affecting drilling friction and investigation of the friction reduction tool in horizontal wells in Sichuan

摘要

Based on field data and the related theories, the effects of drill string length, rotation speed, trajectory, and drilling fluiddensity on the friction during horizontal well drilling are analyzed in Sichuan. With increasing the length of drill string inthe horizontal section, the friction grows. The drill pipe rotates faster and the torque decreases. Large undulation ofborehole deviation and the ‘‘W’’ shape of the horizontal section lead to excessive friction. A higher fluid density causeshigher torque and drag. Moreover, a friction reduction tool is designed to reduce friction, decrease the wear betweenthe casing and the drill pipe joint, and prevent the differential pressure sticking, which improves the rate of penetration,and the specially designed spiral diversion channels improve the efficiency of borehole cleaning. The field experimentalresults have shown that the accumulated operational time of the friction reduction tool is more than 130 h and its fatiguelife reaches up to 3 3 105 cycles. A plan of improving the tool structure is proposed to reduce the mud balling after theexperiment. Finally, the mathematical model of calculating the spacing of the friction reduction tools is established, whichprovides technical support for investigating the friction in horizontal well drilling.