| 摘要 |
A method and apparatus for changing the speed of a drill bit down hole in a fluid-actuated motor, including a positive displacement motor and a hydraulic motor, is disclosed. The apparatus comprises a bypass valve installed in the motor for controlling flow through and around the power section of the motor. When closed, the bypass valve forces all fluid to flow through the power section of the motor, imparting maximum speed to the drill bit. When opened, a portion of the fluid flow is allowed to flow around the power section of the motor, thereby reducing the speed of the drill bit. The bypass valve may be opened or closed mechanically, electrically, hydraulically, pneumatically, or by any other means, including a removable plug.
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