下部钻具组合稳定器的径向位置判断方法

A method for determining boundary conditions at stabilizers in bottom hole assembly analysis

在应用下部钻具组合上切点位置确定方法的基础上,给出了描述稳定器在井眼中位置的方法,并提出了可在三维力学问题中用于判断稳定器在井眼中径向位置的方法。首先忽略井眼约束并计算下部钻具组合的变形,再施加井眼约束条件,按某种顺序逐一计算稳定器在井眼中的位置,最终依据井壁对稳定器支撑反力的大小及方向筛选出最合理的结果。理论计算结果表明:无论采用何种装置角,相比假设稳定器与上切点均在井眼低边,采用本文方法计算得到的最小钻头弯矩更小,这意味着下部钻具组合所具有的势能更小,更趋于达到稳定状态;计算得到的钻头方位力方向与现场实践所取得的认识保持一致。本文研究可为下部钻具组合的优化设计提供理论依据。

To determine the upper boundary condition at the tangential point in BHA analysis,a method on how to describe the positions of stabilizers in wellbore is established firstly,and then a method about how to determine boundary conditions at stabilizers in BHA 3 D analysis is developed.In this method,wellbore constraint is ignored and BHA deformation is computed.Subsequently,wellbore constraint is taken into account and the position of stabilizers in wellbore is judged in some order.Finally,the value and direction of the force that wellbore wall supports stabilizers are computed,and according to which,the most reasonable boundary conditions at stabilizers can be obtained.The theoretical results show that,regardless of the device angle,compared with assuming stabilizers and upper tangential point are always lying on the low side of wellbore,the minimum bending moment at bit is much closer to zero if the method presented in this paper is applied.It means that the potential energy possessed by BHA is much closer to zero,and BHA is much steadier.In addition,the computed direction of bit azimuth side force agrees with field practice.The method provides a theoretical base for BHA design.