Small-size turbine drilling tools have better application prospects in small borehole drilling and so on. Based on the SST model, the influence of a Φ73 mm turbine knuckle-shape parameters on the mechanical energy output characteristics was simulated, and the vortex structure of the turbine internal flow field was analyzed to find the law. First, the influence of leading-edge radius on the turbine internal flow field is concentrated on the rotor suction surface. Second, as with the axial clearance, there is a regular effect of the trailing-edge radius on the flow field in the rotor as a whole and in the middle and rear parts of the stator. Third, the change in the installation-staggering angle does not change the turbine output performance. The output performance is optimal when the leading-edge radius of the Φ73 mm turbine blade is 0.8 mm, the trailing-edge radius is 0.4 mm, and axial clearance is 6 mm. At the same time, the effects of rotational speed, displacement, and fluid viscosity on the output performance of the turbine were simulated, and the output performance of the turbine of this size was predicted under the conditions of low rotational speed, small displacement, and high fluid viscosity. Under the working conditions of conventional drilling parameters, the output pressure drop of a single-stage turbine can be up to 0.018 MPa or less, and the torque is more than 1.6 Nm. If 100–200-stage turbines are used as the power, the output torque can reach 150–300 Nm, which can meet the demand of rock-breaking in the mine.

Summary: The cleanliness of wellbore is a key factor in the drilling speed and quality of an oil field, especially in long horizontal sections of horizontal wells. Therefore, a hydraulic-magnetic rotary hole cleaning tool has been designed that does not rely on the rotary action of the drillpipe and could be used with a downhole motor to improve hole cleaning efficiency. However, the influence of magnet shape on the transmission of magnetic torque has remained unclear, such that the magnetic shaft transmission torque needed to be optimized to ensure efficient tool operation. In this study, magnetic field control equations were established in the region of the permanent magnet and air gap, and the magnetic flux distribution and magnetic torque generated between two magnetic axes in each field were calculated. Also, the influence of various magnetic field parameters on magnetic torque conduction of a strip magnet were compared and analyzed and then confirmed by comparison with experimental results. The results showed that the magnetic torque transmitted by strip magnets varied sinusoidally with magnetic axis deviation angles and that the highest torque was generated in the 12-pole model. However, the rate of increase in magnetic torque with magnet thickness was opposite to that of tile magnets, increasing with increasing magnet thickness. Magnetic torque variation with covered area was specific in the 6-pole model, showing a tendency of increasing and then decreasing. When magnet thickness was 12 mm and magnet coverage area in the effective cross section of the tool was 80%, the highest magnetic torque/unit volume of magnet was generated for achieving economic optimization. The results led to conclusions that, by solving the regional magnetic field, the magnetic torque change characteristics during movement of the magnetic drive mechanism of the hydraulic-magnetic rotary hole cleaning tool were simulated successfully and that these results could be used as an optimization analysis method for the magnetic drive mechanism of such tools.