螺杆钻具等壁厚衬套的设计及仿真分析

DESIGN AND PERFORMANCE ANALYSIS FOR EQUIDISTANT LINING 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、高密度钻井液井以及小曲率半径的水平井。常规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,设计了一种等壁厚螺杆钻具衬套,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 lining 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 its efficiency will descend continually.Therefore,the development and application of PDM with the short,high-power,high pressure drop and low rotation speed has become an important tache to improve the drilling efficiency and save drilling cost.In this paper,the equidistant rubber lining of PDM was designed,the mechanics experiments of NBR were carried out,the FEA models of equidistant lining and the conventional one were established for calculating.The results indicated,under the same mud pressure when comparing with the conventional one,the equidistant lining has less deformation;with the same magnitude of interference,it has a better seal capability.The equidistant PDM can gain the same torque with less length than the conventional one.