GB/T 43949-2024Drilling system of mobile offshore drilling rig - Configuration and technical requirement (English PDF)

3 Terms and definitions

The terms defined in GB/T 23505-2017 and GB/T 28911 apply together with four terms given here. A mobile offshore drilling rig (3.1) is an offshore mobile drilling platform that moves between different oil and gas fields to carry out drilling; a note says that it is used mainly for the exploration and development of offshore oil and gas resources, drilling exploration wells and production wells, and that it is divided by working water depth into shallow water and deep water drilling rigs, each fitted with the drilling system matched to that depth.

A shallow water drilling rig (3.2) is a drilling rig whose maximum operating water depth is not greater than 165 m, given in the original as 550 ft, and a note says it is mainly the jack-up rig. A deep water drilling rig (3.3) is one whose maximum operating water depth is greater than that figure, and a note says it is mainly the semi-submersible rig and the drillship. The maximum hook load (3.4) is the maximum load, static and dynamic, that the equipment can bear as determined from the material strength and a specified safety factor, that is the maximum load the hook of a drilling or workover rig can lift at the largest number of lines; the definition is taken with modification from GB/T 23505-2017, 3.1.4.

4 General

4.1 The configuration and the technical requirements shall meet the relevant rules of the classification society and shall also satisfy the requirements of offshore oil and gas exploration and development, working with the other systems of the platform for efficient and safe drilling; the fire, explosion and operating safety requirements of the platform; the environmental requirement of zero pollution from platform discharges; the requirements of single well and multi well operation for exploration and production wells; the requirement that automated drilling be efficient and coordinated with no interference between items of equipment; the platform design input conditions and the interface requirements towards the other platform systems; and the interface requirements towards third party drilling equipment, such as remotely operated vehicles, mud logging equipment, well testing equipment and cuttings handling systems.

4.2 The recommended configuration of the key systems or equipment of a shallow water drilling system is given in Table A.1 of Annex A and that of a deep water drilling system in Table A.2.

5 Configuration

5.1 The drilling system comprises the hoisting system, the rotating system, the automated tubular handling system, the heave compensation system, the riser system, the well control system, the mud circulating system, the bulk material system and the drilling control system.

5.2 A hoisting system with a conventional drawworks is made up mainly of the derrick, the drawworks, the travelling block, the crown block, the deadline anchor, the drilling line drum and the wire rope; a hoisting system with hydraulic cylinders is made up mainly of the derrick, the cylinders, the hydraulic power unit, the sheave blocks and the guide frame. The configuration shall meet GB/T 25428 and GB/T 19190. The derrick shall have a main structure strong enough for the maximum hook load, with strength and overall stability calculations based on the drilling conditions and the defined working environment; a height that suits stand handling, with at least 10 m of clear height kept between the top drive elevator and the top of the stand; a base size suited to the stand capacity of the fingerboard and to the fingerboard type, and a top size suited to the installation dimensions of the passive drill string compensator and the active crown block compensator; a main structure and outfitting able to withstand offshore corrosion, preferably galvanized; a design that allows the derrick to be lifted in panels, in sections or as a whole, with the main beams and supporting structures preferably connected by anti-fall bolts and the interior arranged for maintenance, personnel safety and comfortable operation; and a form and function suited to efficient tubular handling and tripping. The drawworks shall meet SY/T 5532 and the drilling line SY/T 5170.

5.3 The rotating system is made up mainly of the top drive and the rotary table and shall meet GB/T 31049 and SY/T 5080. The top drive shall have constant power and constant torque regulation, preferably by wide frequency alternating current variable frequency drive; hydraulic telescopic guide rails that extend to the well centre or retract for stowage; an elevator and tools for making up and breaking out tubulars; and an internal manual and remotely controlled blowout preventer whose pressure rating matches the well control equipment.

5.4 The automated tubular handling system is made up mainly of the knuckle boom crane, the catwalk machine, the iron roughneck, the pipe racking machine and the fingerboard, and shall meet GB/T 3766, GB/T 7932 and GB/T 7935. The crane shall have interchangeable boom grippers for different items; the catwalk machine shall convey tubulars and be fitted with a nose tilting device and a side loading device for automatic loading, with a dedicated riser rack and riser crane where risers are to be conveyed; the iron roughneck shall make up and break out tubulars at the well centre and the mousehole, and on a deep water rig shall also handle casing and should have a built-in mud bucket; the racking machine should be variable frequency driven and fitted with a lifting arm and a guide arm so that it can move and rotate freely between the racking area and the well centre area; and the fingerboard shall take drill pipe, drill collars and casing, its capacity matching the drilling depth of the platform.

5.5 The heave compensation system is made up mainly of the passive drill string compensator, the active crown block compensator, the travelling block compensator, the riser tensioner and the casing tensioner, and shall meet GB/T 30217.1, SY/T 6913 and SY/T 7460. Its capacity and cylinder stroke shall match the platform type and the working environment; it shall have dedicated cylinders, a hydraulic power unit, accumulator bottle banks, an air system, a control panel and gas bottles; the hydraulic fluid shall be a fire resistant or water based fluid, preferably an environmentally friendly water based fluid; and the riser tensioner shall be of the wire rope type or the direct acting cylinder type.

5.6 The riser system is made up mainly of the riser spider, the gimbal, the telescopic joint, the tension ring, the flex joint, the riser, the riser pup joint, the riser fill valve, the buoyancy modules and the running and pressure testing tools, and shall meet GB/T 30217.1 and SY/T 6913. The telescopic joint shall use two different power sources, pneumatic and hydraulic, with automatic changeover on failure; risers may be stored horizontally or vertically; handling equipment and maintenance arrangements shall be provided as needed; the outside of the riser shall carry the kill line, the choke line, the booster line and the hydraulic line; risers and buoyancy modules shall suit the working water depth and environment of the platform; riser lifting gear shall have anti-swing capability in horizontal or vertical lifting; and the riser connector should be of the large angle unlocking type, with high strength large angle alignment devices on the riser connector and the wellhead connector.

5.7 The well control system is made up mainly of the diverter, the blowout preventer, the choke and kill manifold, the mud gas separator, the blowout preventer control equipment and the diverter control equipment, and shall meet SY/T 5053.2, SY/T 5323 and SY/T 6868. It shall suit the well fluid and the wellhead pressure. The diverter shall have two emergency discharge lines interlocked with the mud return line. Blowout preventers are divided by working environment into surface and subsea; a surface stack should have four rams and a subsea stack should have not fewer than five, of which one shall be a drill pipe shear ram, one a casing shear ram and one a variable bore ram, and a deep water stack shall have an emergency disconnect function. Each side of the stack shall have not fewer than two choke and kill line outlets, one kill line outlet being on the lowest ram preventer. The choke and kill manifold shall have an antifreeze injection device, and both the choke side and the kill side shall have at least two glycol injection ports and two pressure test connections. The valve material of the manifold shall match the blowout preventer, resist corrosion by hydrogen sulfide and similar media, and be of material class EE or better. Subsea blowout preventer control equipment shall also have a control umbilical and reel, a subsea control pod and a remotely operated vehicle control panel, and the diverter control system shall have a hydraulic power unit, hydraulic control valves and instruments, accumulator banks and a diverter control unit.

5.8 The mud circulating system is made up mainly of the high pressure mud pumps, the high pressure manifold, the fill pump, the mixing pump, the mixing hopper, the big bag machine, the bag cutting machine, the liquid additive skid, the chemical addition tank, the high shear mixer, the mud scraper, the distributor, the shale shakers or mud cleaners, the return mud handling equipment, the desilter, the desander and the degasser, and shall meet SY/T 5612. The low pressure part shall have handling, mixing and conveying equipment for bulk material and additives so that mud can be batch mixed to a set density automatically, and return mud handling equipment sized for the maximum design return flow and for the handling and discharge of drilling fluid solids, with collection or export of the solids. The high pressure part shall have pumps, lines and manifolds suited to the design pressure and the mud flow rate; the pumps should be wide frequency alternating current variable frequency driven, their pressure and displacement matching the drilling capacity of the platform; equipment redundancy should be considered with one pump preferably kept as a spare; pulsation dampeners and safety relief valves shall be fitted on the suction and discharge sides; and the pump motors should drive through chains or gears with the corresponding cooling equipment.

5.9 The bulk material system is made up mainly of the cement tanks, the weighing units, the surge tanks, the dust collecting tanks, the make-up unit, the transfer lines and the transfer control system. It shall be able to store, convey, transfer between tanks and vent bulk materials such as barite, bentonite and cement; the line systems for barite and bentonite shall be independent of those for cement; transfer between tanks of the same function and conveying should be controlled automatically; the cement tanks, surge tanks and dust collecting tanks are pressure vessels and shall meet GB/T 150.3; and a loading station for conveying and venting bulk material should be fitted on each side of the vessel.

5.10 The drilling control system consists of hardware and software, the hardware being mainly the driller's cabin and the electrical and instrument equipment rooms and the software the automated drilling control software; the equipment rooms hold mainly the driller's chair, the human machine interface, the intercom system, the closed circuit surveillance system, the uninterruptible power supply and the control cabinets. The driller's cabin shall have laminated windows that screen strong light, with impact protection steelwork and a glass washing system; shall be kept at positive pressure with a low pressure alarm; shall have two interchangeable driller's consoles; and shall have a degree of protection suited to the hazardous area. The electrical and instrument rooms shall have explosion proof lights connected to the platform emergency power system and shall have smoke detectors and manual alarm buttons. The control system shall have an anti-collision system that keeps the drilling equipment coordinated and a power distribution function module that allocates the power the platform provides.

6 Technical requirements

6.1 The technical parameters of the drilling systems and equipment shall guarantee safe operation, and a hazard analysis shall be made of the well control system and the drilling control system. Materials shall suit the use; the driller's cabin, the rotary table and other important equipment shall be laid out so that a falling object cannot destroy them; key drilling components and systems such as cables, intake and exhaust pipes, control and shutdown systems and safety systems shall be designed with adequate protection during platform operation; the main line of the hydraulic control system shall suit the system design pressure, the maximum system flow and the recommended flow velocity in the hydraulic hose, and each branch line shall suit the flow of the equipment on that branch, the printed text repeating the words for each branch; the rig floor area shall have not fewer than two escape routes leading directly to a safe area and the derrick or mast shall have an emergency escape device; and the equipment on the rig floor shall be laid out so that the driller can see the rig floor and the work inside the derrick, directly or through reliable auxiliary equipment.

6.2 The maximum hook load of the hoisting system shall meet 7.2.2.1 of GB/T 29549.1-2023. The rated power of the drawworks is calculated by formula (1), whose legend names the rated power of the drawworks in kilowatts, the upper limit of the nominal drilling depth in metres and a drawworks power calculation coefficient between 0.4 and 0.8, for which 0.5 is recommended.

6.3 The maximum continuous working torque of the top drive shall satisfy formula (2), whose legend names that torque in kilonewton metres and the upper limit of the nominal drilling depth in metres. The rated load of the top drive shall meet 7.2.2.3 of GB/T 29549.1-2023 and shall match the maximum hoisting capacity of the platform.

6.4 The pipe racking machine should be able to handle drill pipe and drill collars from 88.9 mm to 247.65 mm and casing from 177.8 mm to 508 mm; the fingerboard should have racking space for a certain number of 244.47 mm casing joints; the knuckle boom crane should have two sizes of pipe gripper, one for 73 mm to 508 mm and one for 85.72 mm to 762 mm; the stand storage area shall bear the load of the maximum design tubular racking and should withstand the impact of a 247.65 mm drill collar falling 1 m; and when the power source fails, equipment holding tubulars shall keep them held safely for not less than 10 min and shall be able to lower them to a safe position in an emergency. The inch equivalents printed beside these millimetre figures use fraction glyphs that the extraction did not preserve and are therefore not reproduced.

6.5 The pressure and flow of the tension compensation hydraulic system shall be confirmed from the compensation equipment parameters and the required compensation capacity of the platform. Where the platform has several compensation systems, such as passive drill string compensation, active crown block compensation, riser tensioning and casing tensioning, the pressure and flow of each shall be confirmed separately. The pressure of the high pressure air or nitrogen system for compensation and the number and individual capacity of the air or nitrogen bottles shall be confirmed from the accumulator design requirements. Where a long stroke direct acting cylinder riser tensioner is used, the cylinders shall be suitably fixed. A failure mode and effects analysis of the compensation device shall be carried out according to GB/T 7826.

6.6 The dimensions of the riser main pipe and connectors shall be compatible with the blowout preventer size, and the pairing of preventer size with riser size should follow Table 1, which has two columns and five rows and matches each of five preventer bore sizes with one or two riser sizes in millimetres, with the inch equivalents alongside. The riser fill valve pup joint shall have both automatic and manual control. The telescopic joint shall have not fewer than two inner and outer barrel packing sets, shall use pneumatic and hydraulic power sources with automatic changeover on failure, and should have drilling fluid recovery facilities. The lower flex joint shall deflect by not less than 10° and the upper flex joint by not less than 15°.

6.7 The working pressure and temperature class of the well control system shall be confirmed from the working environment of the platform, the temperature class preferably being chosen from Table 2. Table 2 has three columns and five rows and, in degrees Celsius, pairs each operating environment class with a maximum and a minimum temperature: tropical 60 and 0, temperate 50 and -13, cold 50 and -20, extremely cold 50 and -30, polar 50 and -40. The well control hydraulic pipework shall suit the closing time and flow required by the blowout preventer and shall reserve a connection for a rotating preventer. The vent line of the mud gas separator shall end 4 m above the derrick and the line shall suit the vent back pressure.

6.7 continues with the response times: a surface ram preventer shall close in not more than 30 s, a surface annular preventer smaller than 476.25 mm in not more than 30 s and one larger than that in not more than 45 s; a subsea ram preventer shall close in not more than 45 s and a subsea annular preventer in not more than 60 s, and the disconnect time of the subsea riser assembly shall be not more than 45 s. When the main power fails the control system shall change over automatically to the standby supply, which shall provide at least 2 h of control time through an uninterruptible power supply or batteries. The choke and kill manifold shall be connected to the drilling fluid manifold and the cementing manifold, the choke side and the kill side preferably being connectable to the standpipe manifold and the cementing manifold respectively. The bore of the choke and kill lines of the preventer stack shall be not less than 76.2 mm, and not less than 101.6 mm on ultra deep water rigs working below 3 657 m. A telescopic pressure test stump should be fitted below the storage position of the stack so that the steel rings can be changed and the ring faces inspected, and the frame of the stack shall match the transfer equipment.

6.8 The low pressure mud system shall be fitted with mud circulating pumps and similar equipment chosen for the type and density of the mud used. The high pressure mud line size and material shall be confirmed from the high pressure mud pump parameters of the platform. The size and slope of the mud return line shall be confirmed from the mud return flow and the well control equipment size, so that the mud flows into the mud pits after treatment. The pump group power and the mud pit volume shall be chosen according to 7.3.2 of GB/T 29549.1-2023.

6.9 The bulk transfer line size and bend radius shall be confirmed from the bulk conveying capacity required by the platform, through a solids pneumatic conveying pressure drop calculation. The maximum continuous cement supply capacity should reach 120 t/h, and shall be not less than 80 t/h when a single item of equipment fails. Connecting lines should use quick release clamps, long transfer lines should have several compressed air assist lines near the bends and along the run, and bends should be of more than 120° or of a radius of curvature more than five times the pipe diameter. The compressed air used shall be filtered and dried to a dew point 7 °C below the lowest ambient air temperature. A shallow water rig may take the compressed air from the engine room main compressor, whereas a deep water rig shall have a dedicated bulk blowing compressor. The dust collecting tank shall have a working pressure of not less than 0.5 MPa and the dust collected shall be returned to the surge tank.

6.10 The driller's cabin shall be designed and arranged so that the field of view of the operator covers the rig floor and the whole travel of the top drive; its degree of protection shall suit the hazardous area and the air conditioning intake shall be in a safe area; and the control panels shall allow the driller to work quickly. The drilling control system is driven hydraulically, pneumatically, electrically or electrohydraulically, and its voltage shall not exceed 250 V. The software shall be able to control the control systems of the key drilling equipment and the associated pumps and valves; the key software functions shall have a manual override so that control is still possible if a logic circuit fails; the software should provide not fewer than four terminals, the master terminal being in the driller's cabin and a display terminal in the operator's office, with control possible from only one terminal at a time; the software shall pass a third party security assessment; and interfaces shall be reserved towards third party equipment and towards the general platform systems, such as the fire and gas and emergency shutdown systems.

A Annex A (informative) Recommended configuration of drilling systems

Table A.1 gives the recommended configuration of shallow water drilling systems in two columns, one for each of two jack-up rigs distinguished by drilling depth, and Table A.2 gives the recommended configuration of deep water drilling systems in three columns, for two semi-submersible rigs and one drillship. The rows of both tables run through the rig type, the drilling depth, the operating water depth, the derrick type, the maximum hook load and the base dimensions; then the drawworks with its maximum hook load, number of travelling lines and number and power of units; the top drive with its maximum hook load, continuous working torque and number of units; the rotary table size and number; the iron roughneck number and position; the blowout preventer number of stacks and rams, size and pressure; the choke and kill manifold size and pressure; the high pressure mud pumps number and power and pressure; and the high pressure mud manifold, high pressure cementing manifold and mud circulating system medium. Table A.2 adds rows for the tensioners, covering passive drill string compensation, active compensation and riser compensation, and for the riser outside diameter, length and stored quantity.

The cells of both tables carry metric and United States customary values side by side and the extraction merged several row labels with the values that follow them, so the figures are not reproduced here. Two points can nevertheless be seen in the printed text: in the row for the number and power of the high pressure mud pumps the two figures are run together in a form that does not resolve into a pump count times a unit power, and the same manifold size of 103.1 mm is annotated with a three inch nominal size in Table A.1 and with a four inch nominal size in Table A.2.