Classifications

• • E—FIXED CONSTRUCTIONS
  • E21—EARTH OR ROCK DRILLING; MINING
  • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
  • E21B33/00—Sealing or packing boreholes or wells
  • E21B33/02—Surface sealing or packing
  • E21B33/03—Well heads; Setting-up thereof
  • E21B33/035—Well heads; Setting-up thereof specially adapted for underwater installations
  • E21B33/0355—Control systems, e.g. hydraulic, pneumatic, electric, acoustic, for submerged well heads
• • E—FIXED CONSTRUCTIONS
  • E21—EARTH OR ROCK DRILLING; MINING
  • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
  • E21B41/00—Equipment or details not covered by groups E21B15/00 - E21B40/00
  • E21B41/0007—Equipment or details not covered by groups E21B15/00 - E21B40/00 for underwater installations

Definitions

• This invention relates to workover of wells. It is particularly, but not exclusively, related to installation of and intervention into subsea wells, for example subsea production wells.
• An oil or gas well hereinafter referred to as a well, is constructed by drilling a borehole
• the wellhead well accessible at the surface, for example on land or on the seabed, is referred to as the wellhead.
• run means to install the equipment in a well (even if only
• surface means the subsea wellhead.
• a conduit for carrying extracted fluids from a lower region of the well to the surface
• a completion is inserted into the casing and extends from the surface to the
• tubing or a tubing string.
• the completion is supported from an upper end by a tubing
• hanger which rests on, and is locked into place on, the wellhead.
• This process may also include testing seals and joints between the wellhead and the
• tubing hanger the tubing hanger and the completion and between the Christmas tree and the wellhead.
• the Christmas tree is locked into place on the wellhead and controls operation of the well.
• the completion is placed in the wellhead
• a horizontal Christmas tree or a spool or lateral tree
• a Christmas tree can weigh more than twenty
• intervention to take place. This requires production of
• This includes running sensing apparatus to monitor well temperature and
• a workover control system comprising a hydraulic power unit an electrical control unit an electrohydraulic umbilical
• electrohydraulic switch means is also provided which switches hydraulic power to
• a plurality of workover devices are controlled by the electrohydraulic switch.
• the same umbilical is used to
• control at least one workover device during an installation operation and an intervention
• the electrohydraulic umbilical Whilst it is convenient for the electrohydraulic umbilical to be a single umbilical, it may
• the electrical signal control unit receives a control instruction from control
• each workover device provides a function which enables workover to
• the or each workover device is selected from a retainer valve, a subsea test tree, a tubing hanger running tool, a tubing hanger, and a lower marine riser package.
• the electrohydraulic umbilical controls at least one valve
• the switch receives hydraulic power through a single hydraulic supply line.
• supply line may supply hydraulic fluid at low pressure and the other line may supply
• the system is used to workover a horizontal Christmas tree.
• it is
• the system is used to workover wells which have subsea wellheads.
• the electrohydraulic switch contains an electrical module.
• the electrohydraulic switch contains an electrical module.
• electrical module receives an electrical control signal to operate a particular workover
• valves to route hydraulic power to operate one or more workover devices.
• Figure 1 shows a workover control system
• Figure 2 shows a completion being installed in a well
• Figure 3 shows a well intervention
• Figure 4 shows detail of a Christmas tree during well intervention
• Figure 5 shows an exploded view of a riser control module
• Figure 6 shows a perspective view of the module of Figure 5;
• Figure 7 shows a hydraulic schematic of the module of Figures 5 and 6;
• Figure 8 show an electronic schematic of the module of Figures 5 and 6;
• Figure 9 shows an alternative electronic schematic of the module of Figures 5 and 6.
• Figure 1 shows a workover control system 10 being used in the installation of a
• the workover control system 10 is used to control
• the well 14 has a wellhead 16 on which is located a horizontal Christmas tree (XT) 18.
• XT horizontal Christmas tree
• BOP blow-out preventer system
• LMRP marine riser package
• the BOP riser 24 extends from a vessel, such as a ship or an oil rig, (not shown) to a vessel, such as a ship or an oil rig, (not shown) to a vessel, such as a ship or an oil rig, (not shown) to a vessel, such as a ship or an oil rig, (not shown) to a vessel, such as a ship or an oil rig, (not shown) to a vessel, such as a ship or an oil rig, (not shown) to
• the completion riser 26 is
• completion string installation assembly 25 and the completion riser 26 is called a completion string.
• the installation assembly 25 comprises a plurality of individual workover devices, or
• workover devices devices which are discussed below.
• workover devices devices which are discussed below.
• the devices are controlled by a workover control station 28 and a hydraulic
• HPU power unit
• an umbilical 32 extending from a reel 34 on the vessel.
• the installation assembly 25 has a continuous bore through which fluid can pass, from the completion 12 to the
• completion riser 26 and thence to a surface test tree. It is usual to perform a well test
• the installation assembly 25 has a completion riser control module (RCM) 36, a retainer
• RV right valve
• SSTT subsea test tree
• THRT tubing hanger running tool
• TH tubing hanger
• the RCM has been assembled and joined together to form the installation assembly 25.
• the RCM has been assembled and joined together to form the installation assembly 25.
• the RV 38 is a
• connection between the RV 38 and the SSTT 40 is broken. This may occur if the
• RV right
• Installation occurs as follows.
• the XT 18 is carried down into place on the wellhead 16
• TRT tree running tool
• riser 24 (incorporating the BOP 20 and LMRP 22) is placed on the XT 18 and then the
• completion string (comprising the completion 12, the installation assembly 25 and the
• completion riser 26 is lowered so as to run the completion 12 through the BOP riser 24 and then the XT 18 and then into the well 14. Operation of the XT 18 is controlled by a workover subsea control module (SCM) 66.
• SCM workover subsea control module
• the TH 44 is locked onto the THRT 42 and carried by it into the wellhead 16.
• T ⁇ 44 is located and locked into place in the wellhead 16, the THRT 42 is unlocked from
• the TH 44 When in place, the TH 44 supports the completion 12 in the well 14. It also allows for access by wireline services into the completion 12.
• the umbilical 32 provides a hydraulic supply 70 and an electrical supply 72 to the RCM
• the RCM 36 provides hydraulic supplies 70a, 70b and 70c to the RV 38, SSTT 40
• the RCM 36 also sends an electronic signal to the surface which indicates whether the hydraulic supply has reached the required pressure to operate completion
• Hydraulic and electrical supplies 70d and 72b travel from the TH 44 downhole to
• SCSSV surface controlled sub-surface safety valve
• LV lubrication valve
• a surface test tree (not shown) is located on the vessel, above the LV. When the completion 12 is correctiy located in the well 14, the well is tested to make sure
• THRT 42 is disconnected from the TH 44 and the completion riser 26 is retrieved
• the TH 44 is then sealed with a crown plug and internal tree cap to prevent hydrocarbons from flowing out of the well.
• hydrocarbon oil or gas
• Figure 2 is another illustration of installation of a completion 12 into a horizontal well.
• the LV 48 is controlled via an umbilical 54 supplied by a reel 56.
• signals from the HPU 30 pass down an umbilical 50 and are used to
• the umbilical 50 is supplied by a reel 52. Commands
• umbilical 50 is also removed and replaced by a production jumper. This operates a production subsea control module (SCM) 46 (shown in Figure 4) which controls the XT 18 during production.
• SCM production subsea control module
• Figure 3 shows an intervention into the well after production has been occurring.
• SCSSV (not shown) is closed. This stops production, by preventing hydrocarbons
• the completion riser 26 is used to lower an intervention
• the intervention assembly 58 onto the XT 18.
• the intervention assembly 58 comprises, in order from top
• stress joint 60 is simply a joint provided to accommodate relative movement between the
• An LV 48 is located at the top of the completion
• the intervention assembly 58 is analogous to the installation assembly 25 as
• the installation assembly 25 additionally has the function of supporting the completion during installation. Intervention equipment, such as wireline tools and
• umbilical 32 can be used both in installation and intervention.
• LMRP 22 Located on the XT 18 is the LMRP 22. Located on the LMRP 22 is an emergency
• RCM 36 is not used in this configuration.
• the umbilical is connected direcdy to the EDP
• the umbilical 32 from the reel 34 is universal and is used both in installation, as shown in Figure 4a, and intervention, as shown in Figure 4b. Therefore, a single umbilical is
• the HPU 30 receives pneumatic and electrical supplies from the workover vessel and
• the power and control signals are combined into an umbilical jumper 64 which runs to
• the reel 34 is powered and is used to deploy and retrieve the workover umbilical 32 and
• tubing hanger running tool umbilical as required, in a controlled and safe manner
• the reel 34 receives pneumatic power from an external source via the
• An electrical control circuit controlled by a THRT control unit 62 monitors the status of
• control modules one being the production SCM 46 on the XT 18 which controls all of
• SCM 66 which controls additional functions associated with the EDP 63 and LMRP 22 such as connections between the XT 18 and the wellhead and the EDP 63 and the XT 18.
• ROV remotely operated vehicle
• LMRP 22 both to the production SCM 46 and the workover SCM 66. They are used to
• the XT 18 can be controlled by a hydraulic supply from the production SCM 46 or a hydraulic supply from the workover umbilical 32.
• valve located on the XT 18 switches between each of these hydraulic supplies.
• the RCM 36 is shown in Figure 5 in exploded view. It is a discrete section of the
• installation assembly 25 adjacent to the RV 38. It is an electrohydraulic package,
• LP pressure (LP) hydraulic supplies are connected to connectors 80 in a manifold block 88
• HP hydraulic supplies are connected to connectors 82 in the manifold block 88 where
• 80 and 82 are l A" female JIC fittings. They are located at the top of the RCM 36. Two
• electrical connectors 84 and 86 respectively. Electrical conduits run from the electrical
• the RCM 36 has a steel casing comprising a pair of steel covers 90 and a baseplate 92.
• the covers 90 and the baseplate 92 are bolted onto the manifold block 88 to protect
• the manifold block 88 itself provides a support on which to
• the covers 90 and the baseplate 92 are
• compensator is a rubber bladder located and covering a port in the casing.
• bladder is a barrier between the dielectric oil on the inside of the casing and production
• RCM passes down the BOP riser 24 static pressure in the production fluid increases. This acts on the dielectric fluid through the bladder and thus pressure is equalised.
• a pressure valve is installed in the casing at its lower end to vent dielectric fluid in the
• Suitable inlet and outlet ports for the dielectric fluid are provided in the casing.
• Cathodic protection in the form of sacrificial anodes is provided within the casing to
• Threaded connections at the top of the RCM 36 provide attachment to the completion
• the baseplate 92 is deep enough to provide protection for eighteen V " female JIC
• sixteen are for LP hydraulic supply lines and two are for HP hydraulic supply lines.
• the manifold block 88 comprises a machined gallery carrying eighteen directional
• DCVs control valves 95, sixteen of which are LP function and two of which are HP function.
• the RCM 36 also contains an electrical or electronics module which is described further below with reference to Figures 8 and 9.
• the assembled RCM 36 is shown in Figure 6. It is generally cylindrical in shape having
• the single bore is appropriate for use with a monobore completion riser. Two bores would be provided if a dual bore completion riser was used. The purpose of the
• the RCM 36 is provided with pairs of LP and HP hydraulic supplies. These are shown on Figure 7 as two LP hydraulic supplies from the connectors
• Pressure transducers 93 are
• a pressure transducer can be provided for each line controlled by a DCV.
• the signals from the pressure transducers 93 are multiplexed in the electrical module of
• Each hydraulic supply is filtered by its own supply line filter 94 each of which is a 20
• filter manifold which is a sub-assembly bolted to the manifold block 88.
• This filter manifold is integral with the internal structure of the manifold block 88 of the RCM 36.
• the filters 94 are part of a valve sub-assembly comprising check valves to prevent
• flow valve is provided to allow forward flow in the event of the filter becoming clogged.
• Each pair of the LP and HP hydraulic supplies (from connectors 80 and 82) is
• FIG 7 shows a schematic of the hydraulic system of an RCM 36. It should be noted that its functionality is dependent on its particular purpose.
• the system is of an open loop design with returned hydraulic fluid being vented to the
• HP hydraulic supply is provided to two HP DCVs 104 and 106 which control the operation of the SCSSV.
• LP hydraulic supply provides LP pilot pressure to all of the
• DCV outputs pass through the hydraulic connectors in the baseplate 92 to take place.
• the DCV outputs may open and close the RV
• FIG. 8 illustrates schematically part of the electronics module of the RCM 36. This
• module receives incoming electrical control signals by means of, for example, modem
• Microprocessor 122 translates the serial messages from the modem as simple shut
• the microprocessor 122 directs these commands
• solenoid driver boards such as board 123 (only one solenoid driver
• the DCVs 95 are solenoid operated three-way, two-position valves. Energising the
• solenoid directs hydraulic fluid to the function line and thence to the associated workover
• the output of DCV 95 is arranged to activate an actuator 126 to
• signals are sent to the microprocessor 122 via a 4-20 milliamp board 125. Signals from
• Figure 9 illustrates an alternative electronic configuration to that shown in Figure 8.
• the microprocessor 122 is arranged merely to process signals from the
• the PLA 128 decodes the modem output commands and routes them to the
• the PLA is an array of
• a solenoid must be continuously energised to maintain the hydraulic supply to its
• Actuators which are provided with return springs, for example the SSTT valves, close
• the RCM 36 connects and disconnects connections between workover devices. It also connects and disconnects connections between workover devices. It also connects and disconnects connections between workover devices. It also connects and disconnects connections between workover devices. It also connects and disconnects connections between workover devices. It also connects and disconnects connections between workover devices. It also connects and disconnects connections between workover devices. It also connects and disconnects connections between workover devices. It also connects and disconnects connections between workover devices. It also
• RCM which uses a single low pressure supply and a single
• the RCM 36 is a
• the RCM 36 operates the appropriate workover device.

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• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Geology (AREA)
• Mining & Mineral Resources (AREA)
• Physics & Mathematics (AREA)
• Environmental & Geological Engineering (AREA)
• Fluid Mechanics (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Geochemistry & Mineralogy (AREA)
• Fluid-Pressure Circuits (AREA)
• Earth Drilling (AREA)

Applications Claiming Priority (3)

Publications (2)

Family

ID=10834655

Family Applications (1)

Country Status (6)

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Family Cites Families (9)

• 1998
  • 1998-07-01 GB GBGB9814114.6A patent/GB9814114D0/en not_active Ceased
• 1999
  • 1999-07-01 GB GB9915409A patent/GB2338971A/en not_active Withdrawn
  • 1999-07-01 BR BR9911630-8A patent/BR9911630A/pt not_active Application Discontinuation
  • 1999-07-01 WO PCT/GB1999/002088 patent/WO2000001915A2/en not_active Ceased
  • 1999-07-01 AU AU45270/99A patent/AU4527099A/en not_active Abandoned
  • 1999-07-01 EP EP99928157A patent/EP1144794A3/de not_active Withdrawn
• 2000
  • 2000-12-28 NO NO20006688A patent/NO20006688L/no not_active Application Discontinuation

Non-Patent Citations (1)

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