GB1165719A - Improvements in or relating to Automatic Positioning Devices - Google Patents

Abstract

1,165,719. Sub-aqueous drilling. INSTITUT FRANCAIS DU PRETROLE DES CARBURANTS ET LUBRIFIANTS. 8 Dec., 1966, No. 55043/66. Heading E1F. .[Also in Division G3] An object, e.g. a drilling tool, is lowered from a floating vessel to a submerged structure along two guide wires the attitudes of which relative to the submerged structure are detected relative to two reference planes by means producing electrical signals which control the vessel to ensure that the object approaches the submerged structure at the desired attitude. In Fig. 1, parallel guide wires 11, 12, under tension, interconnect a drilling vessel N and a base plate 9 which is lowered on .to the sea bed by means of the wires and has a hole 10 constituting the entrance to a well 8. A drilling tool (motor 5, bit 6) is mounted on spacers 17, 18, which slide down guide wires 11, 12 as the tool is lowered by means of a flexible tube 28 unwound from a drum 29 by a motor-driven winch 41 and passing through a well 7 in the hull of the vessel. When spacers 17, 18 reach hole 10, the drilling tool passes on through collars on the spacers and into the well. Spacers 17, 18 serve to maintain guide wires 11, 12 parallel in the vicinity of the well. The guide wires are attached to base plate 9 by universal pivotted joints associated with potentiometers or selsyns (not shown) which produce signals corresponding to the attitude of the guide wires relative to the base. plate in mutually perpendicular, planes. These signals supplied through a cable 27, and a signal from a compass (not shown) indicating the attitude of the vessel, are applied together with their differential coefficients, to a computer CALC which controls units S 1 , S 2 adjusting the magnitude and direction of thrust of horizontal propellers H 1 , H 2 to move the vessel into such a position that guide wires 11, 12 produce accurate alignment of the drilling tool with the axis of hole 10. Application to the lowering of successive elements to extend the depth of drilling or the lowering of tools for cleaning, the well, is referred to. The position of the vessel, may alternatively be corrected by winches associated with anchored ropes.