| 摘要 |
A rotary well-drilling bit lowered through a drill string to a special orienting, positioning and aligning sub attached to the bottom of the drill string with the aid of mud pressure with the bit approximately 90 DEG from its normal operating position. The drill bit is prepositioned before entering the drill string and utilizes a drill bit positioning means to properly orient and position the drill bit at the bottom of the borehole. Once properly positioned and oriented, a wireline attached motor turns an assembly shaft which raises the drill bit into its bit receptacle. Removal of the drill bit is accomplished by relowering the wireline attached motor and turning the assembly shaft to loosen the shaft from the drill bit and raising the wireline, wireline motor, assembly shaft and drill bit through the drill string.
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