Research and analysis on PDM pressure loss calculation method

With the development of the deep well, ultra deep well and extended reach drilling (ERD) technologies, the Positive Displacement Motor (PDM) has been used more and more popularly. Meanwhile, the pressure loss calculation method is paid much more attention. By concluding and summarizing the present pressure loss calculation methods, the paper divided them into two categories, general methods and model methods, for comparison and analysis in detail. In addition, the Roberston-Stiff(R-S) rheological model has been selected to deduce the pressure loss calculation method in the cylindrical model. Finally, the derivation process of the complex model, one of the model methods, has been perfected. The result shows that we can choose the complex model calculation method to get a high accuracy of pressure loss.