METHOD OF CONTINUOUSLY RAISING AND LOWERING OILFIELD SHAFT DRILLSTRING AND DOUBLE TRAVELING SLIPS DEVICE

摘要

Disclosed is a method of continuously raising and lowering an oilfield shaft drillstring using a twin travelling slips apparatus, wherein two sets of travelling slip mechanisms form the two travelling slips apparatus, the first set of travelling slip mechanisms and the second set of travelling slip mechanisms are respectively mounted on a pithead apparatus (10) to constitute a continuous raising and lowering system. In the process of raising and lowering an oilshaft drillstring, the slips (1, 4) of each set of travelling slip mechanisms alternately clamp or release the drillstring, ensuring a continuous raising and lowering motion for the drillstring (9) from beginning to end under the clamping of the slips, and achieving uninterrupted operation. Further disclosed is a twin travelling slips apparatus. Since a twin travelling slips apparatus is used, the problem of an empty run produced by a conventional single travelling slip apparatus is overcome, eliminating, when raising and lowering the drillstring, the stoppage and waiting time of the drillstring in an empty run when the slip raises or lowers the hydraulic cylinder piston rod.