| 摘要 |
Entry sub for small conduit operations within the bore of a drill string. The entry sub comprises a central body having upper and lower collars, adapted for in-line attachment to a drill string. Each of the collars has a bore therethrough. The upper and lower collars are joined by dual connecting arms, the connecting arms separated so as to provide a cut-out section between the upper and lower collars. Fluid passages are contained within each connecting arm, connecting with the bores of the collars and providing a fluid flowpath through the length of the entry sub. A seal assembly is positioned in the bottom of the cut-out section, permitting a wireline or other small diameter conduit to pass therethrough into the bore of the lower collar and then into the bore of the drill string. A sheave is connected to the entry sub and positioned such that a wireline passing over the sheave enters the seal assembly substantially coincident with the axis of the drill string and positioned away from the wall of the bore of the lower collar and the drill string, thereby minimizing wear on the wireline and the entry sub. The axes of the collars being coincident with the axis of the drill string, no torque or bending moment is created between the entry sub and the drill string when the drill string is picked up with the entry sub connected in-line with the drill string.
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