Abstract: An improved valve for sealing a wellbore and method of use, in particular for prevention of well blow outs. In one embodiment, the apparatus is designed to seal a well through rotation of rams. The rams may be actuated to seal the well without having to work against full well pressure as fluid volumes in the apparatus housing, which also contains the rams, are preserved. This functionality allows the apparatus to be constructed with smaller dimensions than existing prior art blow out prevention valves aiding handling and manoeuvrability. The improved valve according to one embodiment also has a mechanism that guides a wireline or a pipeline being run in the wellbore to the centre of the bore and allows a seal to be formed around the wireline or pipeline.

Abstract: A roller sub system for reducing friction between a tool string and a wall in a well bore for use in the oil and gas industry. The apparatus has a roller body and wheel sub system, which is configured to have removably mounted wheels of variable diameters. A plurality of different diameter wheel sets are described for mounting on the roller sub axles and orientating the system in the well bore. The wheels are fixed to the roller sub axles through a quick-release mechanism. A single apparatus can thus be employed with different diameter wheels to operate in well bores of variable diameters.