岩石力学性质对井眼轨迹走向的影响机理

为了提高在极软、极硬地层中钻井时的井眼轨迹预测与控制能力，研究了岩石力学性质对井眼轨迹的影响机理和相应的控制措施。基于纵横弯曲连续梁理论，分析了地层力学性质对下部钻具组合导向性能的影响，在此基础上，建立了考虑地层力学性质的钻头导向模型，利用钻头导向模型定量描述钻压、造斜力、地层可钻性和钻头各向异性对井眼轨迹的影响。对于Φ215.9 mm井眼，井眼瞬时扩径率小于3%时，宜采用弯壳体螺杆钻具，井眼扩径率大于3%时，弯接头配合直螺杆导向能力更强；地层可钻性级值由1增大为10时，趋势角从6.00°降为1.00°。软地层和侧钻井眼推荐使用弯接头配合直螺杆钻具，硬地层推荐使用侧切能力强的钻头配合单弯螺杆钻具。 

Affecting Mechanism of Rock Mechanical Property on Well Trajectory

To improve the prediction and control ability of well trajectory in very soft and very hard formations,the effect of rock mechanical property on well trajectory and related control measures has been studied.According to beam theory,the effect of rock mechanical property on bottom hole assembly(BHA)property was analyzed,on this basis,a bit steering model was developed considering rock mechanical properties;then the model was used to describe the effect of weight on bit,building force,rock drillability and bit anisotropy on well trajectory quantitatively.For Φ215.9 mm well bore,if the instant expending ratio of well bore diameter is less than 3%,bending house PDM is suitable,if expending ratio is more than 3%,bending sub matched with straight PDM has stronger steering ability.With rock drillability increasing from 1 to 10,well trajectory trending angle decreases from 6.00°to 1.00°.Bending sub matched with straight PDM is recommended for the drilling of soft formation and sidetracking.Bit with more side cutting ability matched with bending house PDM is more effective when drilling hard formations.