Drilling module.

© Patent holder (s):

Heerema Marine Contractors Netherlands SE in Leiden.

© Patent granted:

22.12.2014 © Patent issued:

31.12.2014

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Inventor (s):

Erik van Hattem in Leiden.

Frank Antonio Koopman in Leiden.

© Authorized representative:

Ir. HV Mertens et al. In Rijswijk.

© Drilling module.

© The invention relates to a method of developing a hydrocarbon field in a marine environment, comprising:

• providing a bearing structure (30) which extends above the water (11), the bearing structure comprising bearing supports (206) for supporting a platform (60; 50), the bearing structure being free of any drilling device (212), production equipment (23), lifesaving equipment (222), or living quarters (22) for the crew, • positioning an integral, self-sufficient drilling module (60) on the bearing structure, the drilling module comprising a base (200) having mating module supports (204) which mate with the bearing supports, • drilling with the drilling module, • at completion of the drilling stage, removing the drilling module in a single lifting operation by lifting the drilling module from the bearing structure with a heavy lift vessel (100), leaving the bearing structure once again without any drilling device (212), production equipment (23), lifesaving equipment (222), or living quarters (22) for the crew.

LC 2011002

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This patent has been granted regardless of the enclosed result of the prior art research and written opinion. The patent corresponds to the documents originally filed.

P31663NL00 / WHA

Title: Drilling module

FIELD OF THE INVENTION

The present invention relates to the field of hydrocarbon production in a marine environment. The present invention relates to a new method a combination of a bearing structure, a drilling unit and a production unit.

BACKGROUND OF THE INVENTION

Hydrocarbon drilling and production operations are used to search for and retrieve subterranean hydrocarbon deposits. Many subterranean hydrocarbon deposits are located beneath the sea, and therefore production platforms are often located offshore. In shallow and medium water depths, oil &amp; gas fields are generally developed from a platform which is supported by the seabed and which extends above the water surface.

Prior to hydrocarbon production, drilling operations are conducted. Drilling operations include the drilling of one or more wells in the seabed, from an offshore platform in order to retrieve the hydrocarbons to the surface. Offshore platforms generally comprise a bearing structure, and an upper part which is commonly known as a 'topside'. The bearing structure may be fixed to the seabed and is commonly known as a 'jacket' for water depths up to approx. 150m.

In the invention, it was recognized that current configurations of platforms are not ideal. Platforms typically need to be suitable for two stages of the process, ie a development stage (or drilling stage), in which the holes of the wells are drilled, and a subsequent production stage, in which the hydrocarbons flow from the wells and are prepared for further transport or are partially or fully processed on the platform itself.

It was recognized that the two stage process brings with it specific challenges which until now have not been fully understood, and which have not been resolved in a satisfactory manner.

One known alternative for handling the two stage process is to provide a platform which comprises all technical functionalities, ie all equipment to carry out the required tasks

-2for both the development stage and the production stage. This alternative implies a fully functional drilling rig and a fully functional production platform on a single bearing structure.

In the invention, it was recognized that this is not ideal, because it requires a rather large platform and matching bearing structure. Space on offshore platforms is expensive, which makes this alternative not very cost-effective. Moreover, because the platform needs to be installed when the development stage begins, the production equipment may sit idle on the platform for a considerable period of time. In terms of critical path, the platform can only start drilling once the complete platform is ready and installed.

Another known solution is to provide a separate drilling rig and a separate production platform. The production platform may be supported by the seabed by a fixed structure which extends to above the water line, and which does not comprise a drilling unit. In the development stage, a jack-up drilling rig is positioned alongside the production platform. The jack-up drilling rig performs the drilling work and associated activities. After the drilling stage is completed, the jack-up drilling rig is removed and the production platform takes over.

This method works, but it requires two separate bearing structures which rest on the seabed, at least during the drilling stage. Also, two fully operational units are required, each having its own accommodation, lifesaving equipment and associated equipment. Moreover, a jack up rig can operate only until about 150 m water depth, so this method is quite limited in terms of areas where it can be used.

. The same principle may be applied with floating platforms, a separate floating drilling platform and a separate floating production platform. This has a disadvantage that two fully functional units are required, each having its own hull, or in general buoyancy.

Another known alternative is to provide a drilling module which can be added onto a platform comprising production equipment. This alternative is proposed by Archer, who offer a modular drilling unit that may be placed upon a topside and perform drilling operations. This solution is offered as an alternative to upgrading an existing topside. The drilling module is basically an add-on to a production platform. The drilling module can be removed once the development stage is complete. This solution has an advantage that the drilling module can be re-used in another location after the work is complete.

However, in the present invention it was recognized that this solution does not solve the problem of expensive space on the platform, because the platform still needs to be large

-3enough to accommodate both the drilling rig and the production equipment. This solution also does not solve the problem that the production equipment needs to be installed very early in the process, and sits idle for a considerable period of time. This alternative further does not solve the problem of the critical path, ie that drilling can only commence once the production platform is ready and installed.

Another known alternative in this field is to convert a platform from a drilling platform to a production platform once the development stage is complete. US patent number 4666340 discloses such an alternative. This process provides an advantage that the drilling rig can be reused in another location if properly disassembled from the bearing structure. This process also provides an advantage that the idle time of the production equipment can be substantially reduced.

However, in the present invention it was recognized that that the conversion is difficult and prone to delays as a result of adverse weather conditions. The solution requires multiple installation operations and the connection of many interfaces offshore, thereby increasing the complexity of the required offshore installation operation.

SUMMARY OF THE INVENTION

In order to provide a better way of dealing with the dual stage character of production of hydrocarbons at sea, the invention provides a method of developing a hydrocarbon field in a marine environment, the method comprising:

• providing a bearing structure which extends above the water surface, the bearing structure comprising bearing supports for supporting a platform, the bearing structure being free of any drilling device, production equipment, power supply, water supply, lifesaving equipment, or living quarters for the crew, • positioning an integral, self-sufficient drilling module on the bearing structure in a single lifting operation, the drilling module comprising a base having mating module supports which mate with the bearing supports, • drilling with the drilling module, • at completion of the drilling stage, removing the drilling module in a single lifting operation by lifting the drilling module from the bearing structure with a heavy lift vessel, leaving the bearing structure once again without any drilling device, production equipment, power supply, water supply, lifesaving equipment, or living quarters for the crew, • positioning a self-sufficient production module on the bearing structure, and

-4 • producing hydrocarbons with the production module.

The present invention provides the benefits of a smaller required platform. This results in the possibility to create fixed structures in deeper water than is possible until now. The bearing structure does not need to support both the drilling rig and the production rig, so it can be lighter and / or taller. A jack-up rig is also not required, taking away an important limitation. It is envisaged that the present method can be used in a range of water depths

The present invention may also be used with non fixed bearing structures, ie floating bearing structures.

Another benefit of the present invention is the reduced critical path. With respect to the known alternative of converting a drilling platform into a production rig, a time gain is achieved. The single heavy lift operation according to the invention can be carried out in a single day, whereas a conversion operation typically takes several weeks or several months. This means that with the present invention the production of hydrocarbons can start sooner.

The drilling module can be positioned on the bearing structure and be put in operation before the production module is complete. The required facilities for the drilling phase are thus supplied independently of the production phase. In the overall field development, this will extend the time available for fabrication, integration and onshore testing of the production modules with the duration of the drilling phase. This provides the advantage of additional time to build the production module, possibly taking this activity off the critical path and reduction of the risk of delay in the schedule of the field development.

Most of the fabrication of both the drilling module and the production module can be carried out on land or in a sheltered port. This results in a safer work and better work environment. Also, testing of the drilling module can be carried out on land or in a sheltered environment. A further advantage includes that the module can be optimized for each project. Before it is installed, The number and location of module supports can be adjusted to the number of mating supports on the bearing structure. The capacity of the accommodation can be adjusted to the maximum number of people envisaged to be on the module at one time, and the same goes for the capacity of the drilling equipment, pipe storage or other equipment. Finally the layout of the different elements (accommodation, well bay, etc.) relative to each other on the base frame can be optimized to best fit the layout of the specific support structure the module will be installed on.

-5 The present invention further has a benefit of a lower average day rate over the whole period of development and production, because there is never an idle drilling unit or an idle production unit.

The lower average day rate also results from the easy reusability of the drilling module. The drilling module may be used multiple times in multiple locations ..

Some benefits are already reached in a number of known alternatives, and some other benefits are already reached in other known alternatives. However, there is no known alternative in prior art that reaches all the benefits of the present invention:

1) A single fixed bearing structure on the seabed, or in case of a floating configuration, a single floating bearing structure.

2) Increased water depth (for fixed structures).

3) Reduced idle time of expensive drilling components and / or production components.

4) Reduction of the critical path, ie earlier production.

5) Safer and better work environment.

6) Easy reusability of expensive drilling components.

7) Lower average day rate.

The bearing structure may be a jacket. Alternatively the bearing structure may be floating and is known as a 'SPAR' or 'TLP'. Other types of floating bearing structures may also be possible.

In an embodiment, the drilling module includes a drilling device, a power supply, a water supply, living quarters for the crew, lifesaving equipment, and any other fixed facilities and fixed equipment required to operate as a drilling rig. The drilling module may also include a helicopter deck.

In an embodiment, the production module comprises a base having mating module supports which mate with the bearing supports, the production module further comprising production equipment for producing hydrocarbons, a power supply, a water supply, living quarters for the crew, lifesaving equipment, and any other fixed facilities and fixed equipment required to operate as a production rig.

-6 In an embodiment, the development stage wells are pre-drilled for a large portion, but not completed yet, wherein no fluid connection between reservoirs (14A, 14B) and the drilling module is established yet.

In an embodiment, the wells are completely drilled and temporarily closed before removal of the drilling module.

In an embodiment, the bearing structure is supported by the seabed.

In an embodiment, the drilling module and production module share the same bearing supports on the bearing structure.

In an embodiment, the equipment to control the flow of the well is located above the waterline.

The present invention further relates to a combination of a bearing structure, an integral, self-sufficient drilling module and an integral, self-sufficient production module, • the bearing structure comprising bearing supports for supporting a modular platform, the bearing structure being free of any drilling device, production equipment, power supply, water supply, lifesaving equipment, or living quarters for the crew, • the drilling module comprising a base having mating module supports which mate with the bearing supports, the drilling module including a drilling device, a power supply, a water supply, living quarters for the crew, lifesaving equipment, and any other fixed facilities and fixed equipment required to operate as a drilling rig, the drilling module being constructed and arranged to be positioned on the bearing structure prior to the production module, • the production module comprising a base having mating module supports which mate with the bearing supports, the production module further comprising production equipment for producing hydrocarbons, a power supply, a water supply, living quarters for the crew, lifesaving equipment, and any other fixed facilities and fixed equipment required to operate as a production rig, the production module being arranged and constructed to be positioned on the bearing structure once the drilling module is removed.

-7The present invention further relates to an integral, self-sufficient drilling module comprising a base having mating module supports which mate with bearing supports of a bearing structure, the drilling module including a drilling device, a power supply, a water supply, living quarters for the crew, lifesaving equipment, a helideck, and any other fixed facilities and fixed equipment required to operate as a drilling rig, the drilling module being constructed and arranged to be positioned on the bearing structure prior to the production module.

The present invention further relates to a drilling derrick comprising at least two firing lines which are positioned on the outside of the tower, and are positioned on the same side of a tower.

In an embodiment the drilling derrick comprises carousels for supplying pipes, the carousels being positioned on opposite sides of a tower.

LETTER DESCRIPTION OF THE DRAWINGS

Embodiments of the method and drill module according to the invention will be described by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

Figure 1 schematically shows the known method of drilling wells for a production platform with a jack up drill rig.

Figures 2 - 8 schematically show an embodiment of the method for installation of a hydrocarbon production platform at sea according to the invention.

Figure 2 schematically shows the installation of a bearing structure.

Figures 3 and 4 schematically show the installation of the drill module.

Figure 5 schematically shows the pre-drilling of the wells.

Figures 6 and 7 schematically show the removal of the drill module and replacing it with the upper part.

Figure 8 schematically shows the completion of the wells from the upper part.

Figure 9 shows an exploded view of the configuration.

Figure 10 shows a view of a drilling derrick of the prior art.

Figure 11 shows a view of an improved drilling derrick.

Figure 12 shows a view of a configuration of multiple movable drilling derricks according to the invention

-8 DETAILED DESCRIPTION OF EMBODIMENTS

Figure 1 shows a known hydrocarbon production platform 10 at sea in its operational stage. The production platform 10 comprises a bearing structure 28. The bearing structure 28 comprises a lattice structure known as a jacket, but other structures are possible as well. An upper part 20 (or topside) is located on top of the bearing structure 28. The upper part 20 comprises production equipment 23 required for obtaining and / or processing hydrocarbons, living quarters 22, and a helicopter landing platform 21. Under normal operating conditions, no or only limited drilling and workover equipment is provided on the upper part 20.

During the drilling stage, an assisting platform, more specifically a jack up platform 40, is positioned alongside the production platform 10 to carry out the drilling of the wells. The following systems are essential to drilling operations:

Power system, to provide power for the operations, these are usually diesel generators, with all subsequent systems using electrical motors

Hoisting system, also known as the Draw works, used to pick up and lower pipe or equipment into the well

Circulation system, used to circulate mud. Mud cools, and lubricates the drill bit, circulates drilled cuttings to surface and provides hydrostatic head against the formation Rotary system, using either a Top Drive or Kelly System to rotate the drill pipe Well control system, or BOP (blow our preventers)

The drill rig can be in the form of a Jack Up platform, which is rigidly connected to the seabed; or floating rigs such as Tension Leg, Compliant Tower, Mono Hull Ship, SemiSubmersible or the like. Jack-up rigs are used for water depths up to approximately 150m. At water depths greater than 150m, floating support structures are used.

A problem encountered with drilling with floating support structures is the downtime (or idle time) during bad weather. The day rate of drill rigs is known to be high, and therefore it is a requirement that down time is avoided. Another common problem is the redundancy of drilling equipment offshore, and therefore the lack of efficiency of the use of equipment this needs to be addressed in order to bring down the high day rates.

-9The jack up platform 40 comprises a hull 42 which can float on water. The hull 42 can sail or be towed across the sea. At the desired location, legs 43 are lowered onto the seabed 12 and the hull 42 can be raised above the waterline 11. In said situation, the hull 42 provides a stable working platform from which drilling operations can be performed. The jack up vessel 40 may contain an extendable cantilever 41 which can be maneuvered over the upper part 20 of the production platform 10 in order to reach a specific location where operations are to be performed. Various kinds of equipment, for instance drilling equipment or a multi purpose tower can be provided by the jack up vessel 40, if not available on the production platform.

During operations, the jack up vessel 40 can furthermore provide additional living accommodation and crane capacity if required.

Hydrocarbons are harvested from reservoirs 14 located in or under soil layer 81 - 83. To this end, one or more holes are drilled with a drill string 36 from the upper part 20 into the soil layers 81 - 83 until a reservoir 14 is reached. Such a drilled hole is often referred to as a hydrocarbon well 1. A fluid connection is created between the reservoir 14 and the upper part 20. The fluid connection comprises a riser 31 which spans between the sea bed 12 and the upper part 20, and a wellbore 32, which is in general lined with a string of casings that crosses the various soil layers 81 - 83 until the end 33 of the wellbore 32 enters the reservoir

14. The end 33 of the wellbore 32 contains openings to allow the hydrocarbon fluids of the reservoir 14 to enter the wellbore 32. The production platform 10 is connected to a first well 1A and a second well 1B. Equipment to control the flow of the wells 1 may be located at the platform 10, known in the art as dry tree wells.

The figures 2 - 8 show an embodiment of a method for installing a hydrocarbon production platform at sea according to the invention.

In fig. 2 it is schematically shown that a bearing structure 30 is installed on the seabed 12. The bearing structure is installed with a heavy lift vessel 100 having a crane 101. Hydrocarbon reservoirs 14A, 14B are located sufficiently close to the bearing structure for being reached with a drill string from this location.

In its installed position, the upper end 15 of the bearing structure 30 is located at a certain distance above sea level 11 to ensure that the upper part (or topside which is to be positioned on top of the upper end 15 is sufficiently high above the waves.The lower end 16 is connected to the sea bed 12 via a foundation structure 35.

- 10 The bearing structure 30 comprises bearing supports 206 for supporting a module.

Figures 3 and 4 schematically show the installation of the drilling module 60 on top of the upper end 15 of bearing structure 30. In an embodiment, the drilling module 60 is transported to the installation site on a transportation barge 51. Subsequently, it is lifted in place by an installation vessel 100 using a crane 101.

The drilling module comprises a base 201 which supports the other components. The base 201 has module supports 204 which are configured to mate with bearing supports 206 on the bearing structure 30. The drilling module comprises a drilling derrick 212, lifesaving equipment 222, a helicopter deck 220, a power supply 214, a water supply 214, a hoisting system and a circulation system.

After installation of the drilling module 60 on the bearing structure 30, drilling operations can commence.

In an embodiment of the method, wells are pre-drilled for a large portion, but not completed yet. This means no fluid connection between the reservoirs 14 and the drilling module is established yet. This means that the end of the drill string 33 does not reach the hydrocarbon reservoir 14, a distance 77 will remain between them.

Alternatively, the well can be drilled until the end of the drill string does reach the reservoir 14, and a temporary barrier can be made to stop fluid flowing from the reservoir towards the sea bed. Temporary barriers can include for instance valves or cement plugs. Temporary barriers may be located in the wellhead, on the seabed, in the riser, or in the wellbore.

Figure 6 schematically shows the removal of the drilling module 60 after well drilling has been completed to the desired depth. By removing the drilling module, space on top of the bearing structure 30 becomes available to install the production module 50.

The production module 50 is generally larger than the drilling module 60. The production module may be transported to location on a barge 52. The production module 50 comprises different elements which may be integrally connected and supported by a base 210. The different elements may also be separate and be installed separately on the bearing structure.

- 11 The production module 50 comprises production equipment 23 required for obtaining and / or processing hydrocarbons, living quarters 22, and a helicopter landing platform 21. The production module 50 also comprises a small drill module or workover module 25. In case the wells have not been completed into the reservoir 14, the small drill rig 25 can be used to complete the wells to the desired depth. The production module comprises a power supply 214, a water supply 216, lifesaving equipment 222. The base 210 comprises module supports 204 which mate with the bearing supports 206 on the bearing structure.

In the case the wells were completely drilled, a workover unit may suffice to remove the temporary barriers that are cement plugs that were installed before the drilling module was removed.

A benefit of the method is that a much smaller drill or workover unit can be installed on the production module 50. This saves valuable space. On the other hand, drilling operations may be somewhat slower than when using a larger, more powerful rig, but this is only a limited disadvantage effect as the largest part of the drilling operations have already been performed in the previous steps.

Figure 7 shows the production module 50 installed on top of the bearing structure 30. Drilling or workover element 25 is positioned above the well area.

Figure 8 shows the final situation, where a fluid connection between the reservoirs 14 and the production module 50 is established by either completing the wells such that the end 33 of the well bore extends into the hydrocarbon reservoirs 14A, 14B, or by removing temporary barriers that prevented the fluid connection to be established.

Turning to figure 9 an exploded view of the configuration according to the invention is shown. Multiple components are placed on the base 201 of the drilling module 60. This may be performed on shore, or at least in a sheltered environment. A crane 215 may be included, as well as a helideck 21, accommodation 22, power supply 214, water supply 215, a circulation system 218, and other components. In a next step, the complete drilling module is positioned on the bearing structure.

Turning to figure 10 a known drilling derrick having two firing lines 300A, 300B is shown. The firing lines are located outside the drilling derrick. Turning to figure 11, in another aspect the invention provides a drilling derrick 212 comprising at least two firing lines 300 which are positioned on the outside of the tower, and are positioned on the same

- 12 side of the tower 302. This is an improvement over the known derrick of figure 10 in which the firing lines are on opposite sides of the tower. In the improved drilling derrick, the carousels 306 for supplying pipes are on opposite sides of the tower.

Turning to figure 12, the drilling module 60 may comprise two drilling derricks 212 which are movable over tracks 213 independently from one another. The drilling derricks 212 may each have one firing line or two firing lines and may be configured according to figure 11. This allows the two derricks to perform operations simultaneously over two different wells, thereby making operations more efficient ..

As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which can be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. Further, the terms and phrases used herein are not intended to be limiting, but rather, to provide an understandable description of the invention.

The terms a or an, as used herein, are defined as one or more than one. The term plurality, as used herein, is defined as two or more than two. The term another, as used herein, is defined as at least a second or more. The terms including and / or having, as used herein, are defined as comprising (ie, open language, not excluding other elements or steps). Any reference signs in the claims should not be construed as limiting the scope of the claims or the invention.

The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.