| 摘要 |
A flexible lateral drilling shaft is disclosed, having a concentrically nest ed arrangement of two or more coil springs of which the winding direction of at least one of the springs is opposite to another of the springs. The shaft is included within a lateral drilling tool which includes a deflection assembly having roller bearings to assist the deflection of the flexible shaft. Once inserted into a wellbore, increasing pressure applied t o the shaft will cause the opposing springs to stiffen against each other, providing sufficie nt strength to support the drilling of a lateral drainhole within the wellbore. Further, th e spring is wound from a steel wire having a specific noncircular profile to improve the strength characteristics of the shaft without increasing the bending stress during deflection.</ SDOAB>
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