井眼摩擦系数影响因素及规律实验研究OA

Friction coefficient is a key parameter in calculating the drag force when drilling and is obtained by back-calculation based on the data such as weight on bit and hook load,enabling studies on torque and drag.However,few studies have deeply investigated the influencing factors and variation patterns of the friction coefficient between the drillstring and borehole from the perspectives of friction mechanism,microstructure,and the mixed lubricating medium.To address this issue,a friction experimental platform is built and the studies on the influences of drilling technologies(gas drilling and mud drilling),borehole condition(casing and rock borehole)and the diameter,characteristic and distribution pattern of cuttings are made.The research shows that the geometric irregularity of cuttings becomes more pronounced with increasing particle size,serving as the primary factor controlling friction coefficient variations.Compared to the rough surface of borehole rock,the friction coefficient of casing is much lower,suggesting that improving open-hole quality can reduce drag.Additionally,the envelop effect of cuttings bed significantly increases the friction coefficient.The friction coefficient value is within the range of 0.44∼0.58 when gas drilling and it is 0.25∼0.45 in casing,0.35∼0.55 in borehole rock when mud drilling.