20150267484 | METHOD OF CONTINUOUSLY RAISING AND LOWERING OILFIELD SAFT DRILLSTRING AND TWIN TRAVELLING SLIPS APPARATUS - Disclosed is a method of continuously raising and lowering an oilfield shaft drillstring using a double traveling slips device, wherein two sets of traveling slip mechanism form the two traveling slip mechanisms to form the two traveling slips device, the first set of traveling slip mechanisms and the second set of traveling mechanisms are respectively mounted on a pithead apparatus ( | 09-24-2015 |