柔性短节对静态推靠式旋导工具造斜力的影响

Influence of Flexible Sub on Deviating Force of Static Push-the-bit Rotary Steering BHA

针对目前柔性短节对静态推靠式旋转导向(SRS)工具造斜力影响的研究结论不统一问题,基于AutoTrak Curve结构特点,考虑心轴-外筒-井壁的运动约束形式,组合铁木辛柯梁单元与接触单元,建立了静态推靠式旋转导向底部钻具组合(SRSBHA)有限元模型,选取Newmark-HHT法进行数值求解,并采用纵横弯曲梁法的算例验证了所建模型的正确性。以二维定向井为例,系统地研究了柔性短节对双扶正器SRSBHA造斜力的影响。研究结果表明:两扶正器之间各跨钻柱宜采用“柔性短节紧靠上扶正器,外径较大的钻柱则靠近近钻头扶正器”的塔式组合,以最大程度发挥SRSBHA造斜能力;在不同扶正器间距条件下,造斜力随柔性短节长度变化规律有所不同;柔性短节长度优化应结合扶正器间距进行。研究结果可为静态推靠式旋转导向系统结构优化提供理论支撑。

As for the influence of flexible sub on the deviating force of static push-the-bit rotary steering(SRS)tools,divergent opinions exist.In this paper,based on the structural characteristics of AutoTrak Curve,considering the motion constraints of mandrel-outer cylinder-borehole wall,the finite element model of static push-the-bit rotary steering bottom hole assembly(SRSBHA)was established by combining Timoshenko beam element and contact element.The model was solved numerically by use of Newmark-HHT method and verified by an example of vertical and horizontal bending beam method.Taking a two-dimensional directional well as an example,the influence of flexible sub on the deviating force of SRSBHA with double centralizers was studied systematically.The results show that the tower combination of“the flexible sub close to the upper centralizer,and the drill string with larger outer diameter close to the drill bit centralizer”is suitable for each drill string between two centralizers,so as to maximize the deviating ability of SRSBHA.With different centralizer spacings,the changing rule of deviating force with the length of flexible sub is different.For the optimization of flexible sub length,centralizer spacings should be considered.The research results provide theoretical support for the structural optimization of static push-the-bit rotary steering system.