考虑附加力的大斜度井抽油杆三维力学模型

Three-Dimensional Mechanical Model of the Sucker Rod in Highly Deviated Well

根据抽油杆柱的约束条件和井斜角、方位角的变化等边界条件,充分考虑浮力、惯性力等附加作用力的影响,建立了大斜度井抽油杆的三维受力模型,研究了模型求解的边界条件及计算方法。应用VB语言编写计算程序,并在老168-斜56井进行实例计算,计算结果与实测数据的误差在10%以内,可满足工程要求。分析结果表明,在定向大斜度井中,抽油杆在井眼轨迹增斜段及狗腿处所受的支撑力、摩擦力较大,会造成局部应力集中;由于上冲程轴向力比下冲程大,轴向力分解出的支撑力、支撑力产生的摩擦力也比下冲程大,下冲程在中和点以下,抽油杆受压而可能发生弯曲失稳。因此,在增斜段、狗腿处及中和点以下需重点采取防偏磨、防弯曲失稳措施。

In light of the constraints of sucker rod as well as the boundary conditions of well inclination and azi- muth changes, the three-dimensional force model of highly deviated well＇ s sucker rod was established fully consid- ering the effects of additional forces such as buoyancy and inertial force. The boundary conditions and calculation method of the model solution were studied. The VB language was applied to compile the computing program. The ex- ample computation was carried out in Well Lao 168 - Xie 56. The calculation result falls within an error of 10%, compared with the actually measured data. It can satisfy the engineering requirement. The analysis shows that the supporting force and frictional force of sucker rod are remarkable at the hole trajectory building-up section and dog- leg angle position in highly deviated directional well. The stress concentration will arise. The axial force in the up- stroke is greater than that in the down stroke. Therefore, the supporting force derived from axial force and the fric- tional force produced by the supporting force are larger than that in the down stroke. Sucker rod may undergo ben- ding instability. Measures to prevent eccentric wear and bending instability should be taken especially at building-up section, dogleg angle position and the place below the neutral t^oint.