Research on a multifunctional downhole mud motor generator

In directional drilling, conventional bottomhole assemblies (BHA) typically consist of a mud motor, an independent turbine generator, and measurement instruments. This configuration increases the overall tool length and limits its ability to pass through high-build-rate well sections. This paper proposes a multifunctional generator that integrates the power-generation function into the mud motor. The device directly converts the rotational motion of the drilling tool into electrical energy while simultaneously measuring rotational speed. In addition, tool sticking and stick-slip vibration can be identified by analyzing the speed signal. Experimental results show that the generator operates effectively over a speed range of 270–350 rpm, provides a DC output voltage of 24 V, and achieves a maximum power output of 52 W. The system efficiency is optimal near 300 rpm. The device operates at temperatures from 20°C to 180°C and is designed for an ambient pressure of up to 80 MPa. It also enables rotational speed measurement from 50 to 350 rpm with an error below 3%. By reusing structural components, this design shortens the BHA and provides a new approach for improving build-section passability and enabling self-sensing of drilling-tool status.