Screw Drill Output Performance Analysis And Field Applications

Positive displacement motor (PDM) is a kind of the most widely used downhole drilling motors in oil and gas drilling . With PDM performance and life improvement , PDM is applied extensively in vertical wells besides using to drill special technology wells ( such as directional wells , high angle wells , horizontal wells , extended reach wells, lateral wells , cluster wells, slim holes wells and so on) . In deep well, ultra-deep well drilling and high dip angle formation for drilling vertically and quickly operations, using compounding drilling technology of PDM matching high-performance PDC bit not only increases ROP , but also improves the footage of a single bit, so as to improve drilling efficiency .This paper presents the pressure drop calculation model of PDM by study the relationship of geometry formation , displacement and WOB , in the meantime, influence of WOB and displacement on the actual pressure drop of PDM is analysed . The results have grate significance for understanding of the actual output speed and torque .This paper presents a mathematical model of theoretical and practical output speed and torque of positive displacement motors (Moineu type) for incompressible fluids , and also induces influence of the cross sectional area between shaft and housing and volume on output performance of PDM . By consideration leakage and other factors , this paper calculates volumetric efficiency of PDM . Considering the friction between shaft and housing , this paper establishes mechanical efficiency model . By volumetric efficiency and mechanical efficiency models , the total efficiency of PDM is calculated . On this basis, a quantitative relationship between theoretical and actual output performance of PDM is established . The results provide a theoretical basis for selecting type of PDM matching formation.On the basis of the theoretical study , this paper analyses the test result that uses compounding drilling technology of PDM matching high effective PDC bit in three deep wells in western Sichuan province . The result shows that the compounding drilling technology can enhance ROP effectively, in the meantime, it is a useful method for high steep formation to drill effectively and prevent drilling slope .