OFFSHORE WELLHEAD PLATFORM

Abstract

An unmanned offshore wellhead platform 10 for use in the oil and gas industry, the platform comprising: riser hang-off equipment 13 for connection to at least one riser for flow of hydrocarbon fluids from at least one well; and process equipment 14 for processing the hydrocarbon fluids to produce processed or part processed hydrocarbon fluids for storage and/or transport to another installation, wherein all of the process equipment 14 is on a single process deck 12 of the platform 10.

Claims

1. An unmanned offshore wellhead platform for use in the oil and gas industry, the platform comprising: riser hang-off equipment for connection to at least one riser for flow of hydrocarbon fluids from at least one well; and process equipment for processing the hydrocarbon fluids to produce processed or part processed hydrocarbon fluids for storage and/or transport to another installation, wherein all of the process equipment is on a single process deck of the platform.

2. A platform as claimed in claim 1, wherein the single process deck is the main deck of the platform and there are no other decks for equipment relating to the processing or handling of hydrocarbon fluids.

3. A platform as claimed in claim 2, wherein there are no other decks aside from more decks provided for the purpose of facilitating weather protection, materials handling and/or access to the single process deck.

4. A platform as claimed in claim 1, 2 or 3, wherein the processing equipment includes equipment for processing or part processing the hydrocarbon fluids, such as equipment for water handling and separation for re-injection, hydrocarbon separation, and/or gas reinjection equipment such as via ESP.

5. A platform as claimed in any preceding claim, comprising ancillary equipment required for operation of the wellhead platform, wherein all of this ancillary equipment is located on the single process deck along with the process equipment.

6. A platform as claimed in claim 5, wherein the ancillary equipment comprises an electrical cabinet holding an electrical control system for the wellhead platform.

7. A platform as claimed in any preceding claim, wherein the single process deck is arranged to allow personnel to access the process equipment for maintenance purposes via a walkway for enabling personnel to access the process equipment, wherein the walkway also forms an evacuation route for personnel to leave the platform single process deck in the event of an emergency such as a fire.

8. A platform as claimed in any preceding claim, wherein the single process deck is arranged with the riser hang-off equipment at the centre.

9. A platform as claimed in any preceding claim, wherein the processing equipment is located at an outer part of the single process deck in one or more location spaced apart from the centre of the deck.

10. A platform as claimed in any preceding claim, wherein the single process deck includes one or more materials handling device(s) for movement of materials about the plane of the single process deck.

11. A platform as claimed in any preceding claim, comprising a weather deck for shielding the single process deck from the weather.

12. A platform as claimed in claim 11, wherein the weather deck supports a crane for lifting heavy items to and from the single process deck.

13. A platform as claimed in claim 11 or 12, wherein the weather deck and the single process deck are arranged such that there is access to certain equipment on the single process deck from above.

14. A platform as claimed in claim 13, wherein the weather deck does not fully cover the single process deck and instead the single process deck extends horizontally outward below the weather deck at the locations of said certain equipment.

15. A platform as claimed in claim 13 or 14, comprising a first crane on the single process deck for moving equipment in the plane of the single process deck; a second crane on the weather deck for lifting equipment vertically from the single process deck; and a laydown area on the single process deck that is accessible to both the first crane and the second crane.

16. A platform as claimed in any preceding claim, comprising an access level beneath the single process deck allowing for access for maintenance.

17. A platform as claimed in any preceding claim, comprising a single process deck holding all of the process equipment on the platform, a weather deck located above the single process deck, an access deck located below the single process deck, and no further decks or floor levels.

18. A platform as claimed in any preceding claim, comprising: equipment and piping associated with the oil and gas installation; a hydrocarbon inventory including hydrocarbons in the equipment and piping; and no mechanism for emergency depressurisation of a hydrocarbon inventory of the platform in the event of a fire; wherein the size of the platform is restricted such that evacuation of personnel can be achieved prior to escalation of a fire due to the lack of depressurisation; and the platform is arranged to permit a fire to escalate by combustion of the hydrocarbon inventory after evacuation of the personnel.

19. A platform as claimed in claim 18, comprising isolation valves arranged to isolate the hydrocarbon inventory of the platform from external hydrocarbons in the event of a fire.

20. A platform as claimed in claim 18 or 19, wherein the restricted size is such that evacuation of personnel can be achieved within an evacuation time that is at most 15 minutes, optionally 10 minutes or below.

21. A platform as claimed in any preceding claim, wherein the unmanned platform has no provision of facilities for personnel to stay on the platform, for example there may be no shelters for personnel, no toilet facilities, no drinking water, no personnel operated communications equipment, no heli-deck and/or no lifeboat; and/or wherein the unmanned platform is arranged such that personnel are required to be present for fewer than 10,000 maintenance hours per year.

22. A platform as claimed in any preceding claim, comprising a gangway and/or a bridge for connecting the platform to a vessel and/or another platform.

23. A platform as claimed in claim 22, wherein the platform includes passive fire protection for at least some of the equipment on the platform; wherein the platform is arranged to have an evacuation time of at most 15 minutes or less using one or more evacuation route(s) via the gangway or bridge allowing personnel to escape to a vessel or to another platform; and wherein the passive fire protection is installed on the equipment and/or piping in order to prevent escalation of the fire that would create a risk to personnel on the evacuation route(s) during a determined maximum evacuation time.

Description

[0044] Certain embodiments of the present invention will now be described in greater detail by way of example only and with reference to the accompanying drawings in which:

[0045] FIG. 1 is a view of a 3D model of an example unmanned wellhead platform with a single deck for process equipment; and

[0046] FIG. 2 shows the process equipment deck of the example platform with the weather deck omitted so that the layout of single process deck can be seen.

[0047] The proposed unmanned wellhead platform can be used in a field development comprising one or more wellhead platforms along with associated processing platforms, which may advantageously also be unmanned in the same way as the wellhead platform. In some examples the proposed unmanned wellhead platform is implemented as a part of an unmanned field development similar to that described in GB 1615681.2, GB 1615683.8, GB 1615686.1 or GB 1615687.9 and the unmanned wellhead platform described herein may replace one or more of the wellhead platforms described in those applications.

[0048] The platform is shown in in FIGS. 1 and 2 with an example layout. The example offshore wellhead platform 10 is an unmanned platform and hence personnel are not permanently present. The platform 10 also omits features that would be required for permanent personnel, such as a heli-deck, accommodation and toilet facilities and so on. A single process deck 12 is the main deck of the platform 10. This single process deck 12 holds riser hang-off equipment 13 at a central part of the deck 12 and it also holds all of the process equipment 14 for the platform 12. Thus, there is no process equipment 14 on the platform 10 aside from the process equipment 14 on the single process deck 12. The process equipment 14 may include water removal equipment, separators and so on. In most cases the process equipment 14 will only carry out partial processing of hydrocarbons received at the platform 10 via risers attached to the riser hang-off equipment 13, for example processing to remove water for reinjection and/or other processing to allow for more efficient transport of hydrocarbons to other installations for further processing. The riser hang-off equipment 13 may include connections to multiple risers as well as associated manifolds and the like.

[0049] In addition to the process equipment 14 the single process deck 12 also holds ancillary equipment needed for operation of the unmanned wellhead platform 10, such as an electrical cabinet 16 that holds an electrical control system and other electrical sub-systems for the unmanned wellhead platform 10. The single process deck 12 further includes a walkway 15 for use by personnel when they are present, i.e. for access to the equipment 14, 16 for maintenance or inspection and for use in evacuating the platform 10 when needed.

[0050] It will be appreciated that the layout of the equipment on the single process deck 12 could be varied compared to that shown whilst still obtaining the advantages of having all of the process equipment on a single floor.

[0051] The platform 10 further includes a weather deck 20 above parts of the single process deck 12 and an access level 24 below the single process deck 12. The weather deck 20 protects the single process deck 12 from weather and the access level 24 allows for personnel access below the single process deck 12 for maintenance and the like. The access level 24 can hold ESVs and also provide a riser pull-in level for use when the platform is first commissioned and risers are connected.

[0052] Handling of materials such as component parts and the like is enabled via a gantry crane 18 for moving items around the plane of the single process deck 12 and a jib crane 22 on the weather deck 20 for lifting items off the process deck 12. Local handling for each item may involve the use of permanently installed pad eyes and monorails and/or temporary equipment in addition to the two cranes. The single process deck 12 is designed for internal horizontal transport handling from laydown areas to and from the location where the items are needed. The weather deck 20 does not extend across the full extent of the single process deck 12 in order to allow for vertical access to heavier equipment such as the process equipment 14 and the electrical cabinet 16. Thus, the jib crane 22 can have access to vertically lift such equipment from the single process deck 12.

[0053] Since all the main equipment, including all of the process equipment 14, is on the single process deck 12 and hence is in a single plane then the proposed platform 10 allows for greater automation and the use of robotics to augment the materials handling solutions that are used. Thus, the platform 10 may be arranged for remote and/or automated operation of the gantry crane 18 and/or the jib crane 22, as well as optionally including further automated systems for materials handling and/or for monitoring or maintaining the platform equipment, amongst other things. There are advantages to be gained from minimising the need for active human intervention and allowing for maximised unmanned operation of the platform.

[0054] The platform 10 will allow for various evacuation routes from differing locations using the walkway 15 about the single process deck 12 and the stairways/ladders shown in the Figures. The evacuation routes need to be established with the slowest evacuations being used as the basis for a maximum evacuation time, which can then be used in determining what fire protection should be included in some examples, i.e. to allow for optimised (minimised) fire protection. The platform 10 is provided with passive fire protection (PFP) in order to ensure that a fire will not escalate until after any personnel that are on the platform have been safely evacuated. The platform 10 has no hot flare and in this example there is no mechanism of any sort for emergency depressurisation. It should be noted that the absence of a flare can increase the risk of a dangerous escalation of a fire, since there is no depressurisation. However, the absence of the flare contributes to allowing for the size of the platform 10 to be reduced and the evacuation time to be minimised. Moreover since the platform 10 is an unmanned platform then personnel will only be present with a connection via a bridge (not shown in this example) or a gangway to a service vessel being present as well, which means that the evacuation process can be very quick. It is estimated that personnel can escape to the stair tower within 1 minute after the initial incident, and a conservative assumption is that personnel will be on the service vessel within 10 minutes.

[0055] The evacuation time and/or the length of the route is assessed for various evacuation routes, or at least for the longest routes, in order to identify the evacuation route with the longest evacuation time. The evacuation time is calculated based on assessing the nature of each part of the evacuation route, allocating a time required for a person to traverse each part of the evacuation route, and summing the times. The time required for a person to traverse each part of a route is based on the length/distance for the route and on a set speed for different types of route. Preferably the speed is based on evacuation of an injured person. Optionally the speed may be based on favourable weather conditions. In the case of an unmanned platform personnel would not board the platform during adverse weather and therefore it may not be necessary for the speed during evacuation to take account of adverse weather. The speeds can be based on past experience and/or empirical calculations for speed of movement of a person.

[0056] By way of example, the speed of movement may be set as follows:

[0057] Evacuation of uninjured person: 1.0 m/s for corridors (flat decks), 0.6 m/s for stairs and 0.3 m/s for ladders.

[0058] Evacuation of injured person: 0.5 m/s for corridors, 0.2 m/s for stairs and 0.3 m/s for ladders.

[0059] The example platform above is about 20 m by 20 m. The longest evacuation route is determined to be from the far corner of the access level 24 or the far corner of the single process deck 12 to the stairway for access to a service vessel. Conservatively, the distance around the outer periphery across the deck is used. The escape route is hence as follows: walk around deck (about 40 m) and then walk via stairs to service vessel (about 30 m, partially stepped).

[0060] Using the speeds set out above, the evacuation time for non-injured and injured personnel can then be found. For a non-injured person the timings are: walk around deck40 s, walk via stairs to service vessel50 s (using the slower stair speed for the whole distance to get a conservative time), with a total time of 90 s. For evacuating an injured person the timings are: walk diagonal across deck80 s, walk via stairs to service vessel150 s, with a total time of 230 s.

[0061] The evacuation time is used in assessing the risk and determining the required passive fire protection. Passive fire protection is provided to equipment and/or piping on the platform in order to prevent escalation of the fire that would create a risk to personnel on the evacuation route(s) during the determined evacuation time. For minimum fire protection this includes providing passive fire protection only to the extent required to remove the risk to personnel on the evacuation route(s) during evacuation. Thus, if there is a risk of escalation within the maximum evacuation time due to rupture of certain pipework in the vicinity of an escape route, or liable to affect an escape route then passive fire protection is provided to restrict the increase in temperature of the pipework during a fire and/or to increase the strength of the pipework to make it more resistant to rupturing. Alternatively or additionally, if there is a risk of escalation within the maximum evacuation time due to hydrocarbons present in certain equipment in the vicinity of an escape route, or liable to affect an escape route then passive fire protection is provided to restrict the increase in temperature of the equipment during a fire and/or to protect the equipment from to make it more resistant to ignition of the hydrocarbons and/or explosion of the equipment. Such equipment may include compressors, scrubbers, coolers, metering devices, valves and so on.