螺杆钻具等壁厚衬套性能分析

PERFORMANCE ANALYSIS FOR UNIFORM WALL THICKNESS BUSHING OF PDM

螺杆钻具以其独特的优势在定向钻井生产中得到青睐,但仍不能广泛应用于深井、高密度泥浆井以及小曲率半径的水平井。目前,常规螺杆钻具衬套的内表面是螺旋曲面,橡胶衬套厚薄不均,衬套抗变形能力低,单级承压小,泄漏沿程长,机械特性软,热膨胀不均、磨损速度快,故导致效率持续降低。因此,长度短、大功率、高压降、低转速螺杆钻具的开发与应用,已成为提高钻井效率、节约钻井成本的重要环节。为此,进行了螺杆钻具橡胶衬套力学性能实验,建立了螺杆钻具等壁厚衬套和常规衬套的力学计算模型。结果表明,在相同压力下,等壁厚衬套比常规衬套有更好的抗形变能力;在相同的过盈量下,等壁厚衬套有更好的密封能力。在同等扭矩下,等壁厚定子螺杆钻具的定子长度可以得到缩短。

PDM(Positive displacement motor) is suitable for drilling directional wells because of its advantages,But it still could not be used for deep wells,high-density mud wells and small-curvature wells widely.The PDM′s conventional bushing is a screw surface,it is a variable-thickness elastomer stator.It has poor capability to withstand the high mud pressure and a soft mechanism characteristic,is easy to leak,wear and tear,and expand unevenly,its efficiency descends continually.Therefore,the short,high-power,high-pressure-drop and low-rotate-speed PDM are developed and applied to improve the drilling efficiency and save cost.In this paper,the mechanics experiment of NBR is carried out,the FEA models of uniform wall thickness and the conventional one are established for calculating.The results indicates,under the same mud pressure when compared with the conventional one,the uniform wall thickness is of less deformation,with the same interference,it has a better seal capability.The equidistant PDM can gain the same torque with less length than the he conventional one.