| 摘要 |
A downhole motor operated by circulating mud fluid in the wellbore is revealed. The motor has nested rotors (16, 18) and is geared (38, 48) to a bit drive. The motor is a dual-rotor pump that is operated as a motor with mud flow through the rotor housing (32) on end connections. The structures of the rotor housing (32) and the rotors (16, 18) can be made of the same material. An angular offset (86) can be incorporated between the centerline of the ouput of the motor and the bit drive. In the preferred embodiment, the motor output is through a gear (38) located within a bigger gear (48) connected to the bit so as to provide a speed reducer. The drive between the rotors (16, 18) and the bit can accommodate angular offset of a predetermined amount for directional drilling. The design is compact and can be used to drill wellbores as small as about 2 1/2'' in diameter, or even smaller.
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