A heave compensation system has a housing (12), an over tension accumulator OTA (32) and an under tension accumulator UTA (34). The housing contains a piston (18) and piston rod (20) connected to the piston and extending from one end (14) of the housing. The housing defines a working fluid region (30) holding a variable volume of a non-compressible fluid W. Tension T applied across the piston and an opposite end of the housing pressurises the fluid W to a pressure Pf. Each of the OTA (32) and UTA (34) having a respective first region (48, 60) in fluid communication with the working fluid region (30) and have respective pistons (42, 54) movable between a topped out position where the respective first regions have a minimum volume and a bottomed out position where the respective first regions have a maximum volume. The OTA piston (42) is also under the influence of a compressed gas at a pressure Po, and the UTA piston (54) is also under the influence of a compressed gas at a pressure Pu. The system (10) has a dead band where the piston rod (20) is held stationary in an intermediate position within the housing while Tu
E21B 19/09 - Apparatus for feeding the rods or cablesApparatus for increasing or decreasing the pressure on the drilling toolApparatus for counterbalancing the weight of the rods specially adapted for drilling underwater formations from a floating support using heave compensators supporting the drill string
B66D 1/50 - Control devices automatic for maintaining predetermined rope, cable, or chain tension, e.g. in ropes or cables for towing craft, in chains for anchorsWarping or mooring winch-cable tension control
B66C 13/10 - Auxiliary devices for controlling movements of suspended loads, or for preventing cable slack for preventing cable slack
2.
A FIXED TO BOTTOM JACKET SYSTEM AND METHOD OF INSTALLATION FOR AN OFFSHORE STRUCTURE
A jacket system (10) enables construction and installation of multiple jackets Ji utilising a small number of modularised jacket portions. A method is also disclosed for installing a jacket provided with suction piles using a jack up rig where the jacket has a footprint greater than a drillable area of the jack up. A method of delivering the jacket with suction piles to an installation location involves holding a volume of their in the suction piles to provide buoyancy and wet towing the jacket to the installation location.
E21B 15/02 - Supports for the drilling machine, e.g. derricks or masts specially adapted for underwater drilling
E02B 17/02 - Artificial islands mounted on piles or like supports, e.g. platforms on raisable legsConstruction methods therefor placed by lowering the supporting construction to the bottom, e.g. with subsequent fixing thereto
B63B 35/44 - Floating buildings, stores, drilling platforms, or workshops, e.g. carrying water-oil separating devices
E04H 12/34 - Arrangements for erecting or lowering towers, masts, poles, chimney stacks, or the like
A coiled tubing lift frame assembly for use as a back-up heave compensator on a floating vessel is described. The assembly includes a frame having an upper frame section adapted for attachment to a top drive system and a lower frame section adapted to interface with a flowhead assembly. The assembly also includes a pair of hydraulic cylinders spaced apart from one another, the hydraulic cylinders having a respective cylinder barrel and a piston rod translatable therein with free end of the piston rods being fixed to the upper frame section. The assembly also includes a piston accumulator disposed adjacent to a first of the hydraulic cylinders and in fluid communication therewith via a hydraulic fluid line and an air accumulator disposed adjacent to a second of the hydraulic cylinders and in fluid communication with the piston accumulator via a pneumatic fluid line.
E21B 29/12 - Cutting or destroying pipes, packers, plugs or wire lines, located in boreholes or wells, e.g. cutting of damaged pipes, of windowsDeforming of pipes in boreholes or wellsReconditioning of well casings while in the ground specially adapted for underwater installations
E21B 19/00 - Handling rods, casings, tubes or the like outside the borehole, e.g. in the derrickApparatus for feeding the rods or cables
E21B 17/20 - Flexible or articulated drilling pipes
E21B 43/01 - Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells specially adapted for obtaining from underwater installations
E21B 19/09 - Apparatus for feeding the rods or cablesApparatus for increasing or decreasing the pressure on the drilling toolApparatus for counterbalancing the weight of the rods specially adapted for drilling underwater formations from a floating support using heave compensators supporting the drill string
4.
Heave compensation and tensioning apparatus, and method of use thereof
A heave compensation and tensioning apparatus for use on a floating vessel during “locked-to-bottom” operations is provided. The apparatus includes a pair of hydraulic cylinders that are fixed to a lower section of a frame. Respective free ends of piston rods of the hydraulic cylinders are operatively associated with an upper section of the frame. A pair of accumulators are in communication with pressure vessels and the cylinders using a pneumatic fluid line and a primary hydraulic fluid line, respectively. A control valve assembly allows the piston rods to retract or extend in response to, and to compensate for, heave of the floating vessel. An isolation valve can hydraulically lock the piston rods. In this way, the heave compensation and tensioning apparatus forms a rigid link and can be employed as a secondary or back-up heave compensator for a primary heave compensator.
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