螺杆钻具输出特性分析

Output performance analysis of positive displacement motor

马立 付建红 罗飞 马胜吉 谢洪顺 尚立

西南石油大学油气藏地质及开发工程国家重点实验室，四川 成都 610500 西南油气分公司工程技术研究院，四川 德阳 618000 四川石油管理局井下作业公司，四川 成都 610051

分析影响螺杆钻具压降和输出特性的主要因素及造成螺杆钻具实际输出扭矩和转速低于理论值的原因，从螺杆钻具的结构参数入手，考虑钻井液性能和钻压等外部因素的影响，建立螺杆钻具容积效率和机械效率的计算模型，从而求出在施加不同钻压情况下螺杆钻具的输出特性。从螺杆钻具工作效率、输出扭矩和输出转速与钻压的关系图,可以得出螺杆钻具输出特性的变化规律：在一定排量下，随钻压的增大，螺杆钻具的实际输出扭矩增大，实际输出转速降低，这主要是由漏失引起的。该研究成果为现场螺杆钻具选型提供了理论依据。

This paper analyzes the main factors that have great effect on pressure drop and output performance of positive displacement motor (PDM) and the reason that causes the output torque and rotate speed lower than theoretic parameters. From analyzing the structural parameters of PDM, combined with considering the affection of drilling fluids performance and pressures, mathematic model of volumetric efficiency and mechanical efficiency of PDM has been established. By using this model, the output results of PDM can be calculated along weight on bit (WOB). The changing rules have been drawn out from the working efficiency, and the relationship between the output torque and output rotate speed. At a given flow rate, as WOB goes up the real output torque increases and the real output rotate speed decreases. This is mainly caused by the leakage loss. The results of this paper offer a basis for properly selecting the type of PDM.