LONG OBLIQUE HOLE RECTILINEAR DRILLING METHOD AND DRILLING ASSEMBLY

摘要

PURPOSE:To enable a long hole to be drilled by guiding a down-hole drill so that the drill advance direction coincides with an oblique hole drilled by the drill, and rotating the drill and drill string with a specified rotational frequency to set a load at a specified value for drilling. CONSTITUTION:A down hole drill 2 is guided so that the drilling advance direction coincides with the direction of an oblique hole drilled by the drill 2, the rotational frequency of the down hole drill 2 is set to 200-350rpm, a load is set at 2t per 1 inch of bit 3 diameter or less and if necessary a drill string is rotated with 30-100rpm of low speed to drill a rectilinear oblique hole. Next, the inclination and orientation of the drilling direction are detected, and when the detecting value deviates over an allowable value from a predetermined oblique hole direction line 11, correction declination is given to the drilling direction of the down hole drill 2 to hold the drilling center within a predetermined displacement. The existing oblique hole is used for a guide hole so that the outer periphery is drilled expandedly by a hole expanding bit.