A progressive cavity type volumetric hole bottom power machine, referred to as Tapered Bit. The screw drill, which uses mud and clean water as the power medium, is transported to the bottom of the hole through the center hole of the drill rod, and is essentially an energy conversion device that converts the pressure energy of the liquid into mechanical energy. When drilling, the screw drilling tool directly drives the core tube and the drill bit connected to the drive shaft at the bottom of the hole to rotate. The entire drill string is only used as a channel for conveying high-pressure working medium and a rod supporting the counter torque of the drill bit, and does not rotate. Compared with conventional drilling, screw drilling has many advantages, such as drastically reduced drill rod wear and high drilling speed. It is the main tool for drilling directional holes and has played a role in the field of drilling.

       In 1955, the United States Christensen Mine Drilling Products Company began research based on the Moinuo principle, and it was the first to succeed in 1964, named "Dana Drill"; the Soviet Union successfully studied the "convex" screw drill in the early 1970s; China The Exploration Technology Research Institute of the Ministry of Mines successfully developed screw drills in the early 1980s. So far, screw drills are produced in the United States, Russia, China, Germany and so on.

       Screw drilling tools were first used to drill vertical holes, mainly used to drill various directional holes and special engineering holes (such as mine freezing holes). The greater drilling depth is 9023 meters. At present, the smallest diameter of the screw drill in the world is 44.5 mm, and the larger diameter is 304.8 mm. When using a screw drill for core drilling, a core tube should be added between the drive shaft and the bit to take the core.

       The screw drilling tool is composed of bypass valve, screw motor (rotor and stator), universal joint, bearing and drive shaft. Its core is screw motor. In the screw motor rotor and stator transmission pair, the number of stator teeth Z1 is one more than the number of rotor teeth Z2: that is, Z1=Z2+1. Their gear ratios are usually called transmission ratios, which can be selected arbitrarily (1:2, 2:3,..., 9:10) during design. Screw drills designed for high speeds should use screw motors with small gear ratios, while screw drills designed for low speeds and large torques should use screw motors with high gear ratios. With the increase of the rotor-to-stator gear ratio, its efficiency gradually tends to decrease; the output torque of the screw drill depends on the working pressure drop through the motor, and the output speed depends on the flow of the working medium through the screw motor.

        When drilling, conventional drilling equipment such as drilling rigs, mud pumps, Drill pipe and rigs are still needed. When constructing directional drilling, it is necessary to use an orienting instrument to orient the tilting tool. The tilting tools used with the screw drill include bent joints, bent outer pipes and eccentric blocks. The use of screw drills to construct directional holes can improve drilling quality, provide geological data, save footage, reduce costs, and solve many engineering problems that cannot be constructed. Therefore, it is a special tool for drilling engineering.

       The service life of screw drilling tools is generally 150 to 200 hours. The weak link is the low temperature resistance of the stator rubber and the easy damage to the bearings. Intensify the research and development of wear-resistant and high-temperature resistant elastic materials and reliable bearing systems for the manufacture of stators, so that the working life of the screw drill has been significantly improved. And developed a low-speed high-torque screw to be suitable for drilling deep holes and ultra-deep holes.

        working principle

       Drill pipe is a positive displacement downhole power drilling tool that uses drilling fluid as power and converts fluid pressure energy into mechanical energy. When the mud pumped by the mud pump enters the motor through the bypass valve, a certain pressure difference is formed at the inlet and outlet of the motor, which pushes the rotor to rotate around the axis of the stator, and transmits the speed and torque to the drill bit through the cardan shaft and the drive shaft. So as to realize the drilling operation.