METHOD AND APPARATUS FOR SUPPORTING A WELLHEAD

The present invention relates to apparatus and methods for use in supporting wellhead equipment. Aspects of the invention relate to a method and apparatus for reducing fatigue on wellheads and associated conductor and/or casing strings. Other aspects of the invention relate to methods of installing and operating a wellhead support.

Background to the Invention

A subsea wellhead is a structural and pressure-containing interface for drilling and production equipment. It provides a means to hang off and seal off casing used in drilling the well. The wellhead provides secure access to the wellbore in a pressure-controlled environment.

A typical wellhead comprises of a low-pressure housing which may provide a location point for a drilling guide base. The low-pressure housing is attached to an outer conductor.

The wellhead also comprises a high-pressure housing which provides an interface to drilling and production equipment such as a Blow Out Preventer (BOP) or Christmas Tree to the wellhead and also supports the inner casing and tubing strings. From the 1970s until the 1990s it was not common practice to perform wellhead load and fatigue analysis to determine a fatigue life expectancy of a wellhead. However, due to the use of heavier drilling and production equipment, wellhead and conductor casing fatigue is becoming an increasingly important issue in offshore operations.

Fatigue is caused by a combination of forces acting on the wellhead, upper conductor and inner casings during drilling, subsequent work over and decommissioning activities. The forces acting on the wellhead area are due to a combination of loads. These loads typically include the weight of subsea equipment supported by the wellhead and loads induced by movement of the Mobile Offshore Drilling Unit due to wind, waves and swell.

The problem has been compounded by the recent (Post BP Macondo incident) requirements for an increase in functionality of BOP equipment which has resulted in a BOP weight of over 300 tons on modern 6 ram BOPs compared to circa 200 tons for the BOPs typically used when these wells were designed and drilled.

There are a significant number of wells worldwide, for example in the North Sea there are estimated to be over 1000 wells which are still in production or require decommissioning. The majority of these wells, due to the design of the wellhead, conductor and casing strings, would not pass a stringent fatigue analysis due to either inadequate initial design or subsequent operations on the wells having used up a theoretical fatigue life.

Furthermore, there exist some wells where the integrity of the wellhead is diminished to the point where it is not believed capable of supporting the weight of a BOP which is required for plug and abandonment (P&A) operations during decommissioning of a well.

Typically, well operators attempt to stabilise the well by providing a structure or cage around the wellhead to mitigate lateral movement often caused by drift of the riser, examples are described in WO2016/085348 and US2010/0212916. However, these systems cannot be used in wells of reduced structural integrity.

In the event that a wellhead was to have a total structural failure this would be a catastrophic event as the wellhead is the sole support for the BOP, the primary device for controlling the well which prevents blow outs and the release of hydrocarbons. If such a structural failure were to occur there is a risk to the safely of personnel, risk of significant environmental damage, loss of reputation and financial impact.

Summary of the Invention

It is an object of an aspect of the present invention to obviate or at least mitigate the disadvantages of prior art wellhead support systems.

It is another object of an aspect of the present invention to provide a robust, reliable and compact support assembly suitable for deployment on subsea wellheads for a variety of drilling, production and decommissioning operations. The support assembly may provide support to a wellhead, BOP and/or workover equipment.

It is a further object of an aspect of the present invention to provide a subsea support assembly which is capable of supporting and stabilising a wellhead and/or equipment associated with a wellhead, including a Christmas tree, BOP and LRP.

Further aims of the invention will become apparent from the following description.

According to a first aspect of the invention, there is provided a system for supporting wellhead equipment, the system comprising:

a frame apparatus configured to be connected to a wellhead, and

at least one lifting mechanism configured to apply a force to the frame apparatus to reduce vertical loading forces acting on the wellhead.

Preferably, the at least one lifting mechanism configured to apply a force in an upward direction to the frame apparatus to reduce any vertical loading forces acting in a substantially downward direction on the wellhead.

Preferably, the at least one lifting mechanism is configured to extend and retract at least one base section of the frame apparatus. The at least one base section may include a support leg, an actuating rod and/or a base member. The at least one lifting mechanism may be configured to extend at least one base section of the frame apparatus such that it contacts and/or is driven into the seabed. The system may reduce, mitigate or remove vertical loading on the wellhead from the weight of the wellhead equipment such as drilling or production equipment. The system may facilitate stabilisation of the wellhead reducing cyclic loading on the wellhead.

The wellhead equipment may be a wellhead, BOP, LRP and/or Christmas tree.

Preferably, the system comprises a spool. The spool may be configured to couple the wellhead to drilling or production equipment. Preferably one end of the spool is configured to be coupled to the wellhead and the other end of the spool is configured to be coupled to drilling or production equipment. Preferably one end of the spool is configured to be coupled to a wellhead or Christmas tree attached to a wellhead and the other end of the spool is configured to be coupled to a BOP and/or Lower Riser Package (LRP).

The spool may be connectable to a BOP, LRP and/or Christmas tree. The spool may be connected to a BOP, LRP and/or Christmas tree. The spool may be integral formed as part of a BOP, LRP and/or Christmas tree.

The spool may use connectors and/or API flanges to connect to a wellhead, LRP, BOP or Christmas tree.

Preferably the frame apparatus is configured to be attachable to the spool. The frame apparatus may be configured to be attachable to a component of a BOP, LRP and/or Christmas tree in which the spool is integrally formed. The frame apparatus may be attachable to a component of a BOP, LRP and/or Christmas tree. The frame apparatus may be incorporated in the frame or a component of a BOP, LRP and/or Christmas tree.

In this context, coupling or coupled may mean a physical interaction between two components, but does not necessarily imply a direct physical attachment or engagement. An intermediate component may be located between the two components. One of the components may be integrated into another component.

The spool may have a spool body. The frame apparatus is configured to be attachable to the spool by a connector, such as a clamp. The spool body may have a profile shape configured to receive and/or connect to a clamp to facilitate the attachment of the frame to the spool. Preferably the spool is an in-line spool. Further preferably the spool is load bearing.

The spool may transfer any stress or strains applied by the drilling or production equipment to the seabed via the frame apparatus and at least one lifting mechanism.

The arrangement of the spool, frame apparatus and at least one lifting mechanism may allow the transfer of any load that the wellhead would bear from the downward weight of the drilling or production equipment to the seabed.

The spool and/or frame may be designed for individual requirements, including but not limited to monobore completion, dual bore completion, 13 5/8 inch nominal re-entry connector size, 18 ¾ inch nominal re-entry connector size.

Preferably the at least one lifting mechanism is configured to apply an upward vertical force to the frame apparatus to reduce vertical loading forces from the weight of production or drilling equipment acting on the wellhead.

The at least one lifting mechanism may be integrated into the frame apparatus. The frame apparatus may comprise a frame body. The apparatus may comprise at least one support leg or rods. The at least one support leg or rod may be configured to be movable relative to the frame body. The at least one support leg or rod may be moved relative to the frame body by the at least one lifting mechanism. Preferably the apparatus has at least two support legs.

Preferably the at least one support leg or rod has a base member or foot at one end. The base member or foot is configured to engage the seabed or a support structure. The base member may be selected based on seabed/mudline conditions.

The at least one lifting mechanism may be located between the frame body and the at least one support leg or rod. The at least one lifting mechanism may be located between the at least one support leg or rod and the base member.

The base member may be selected from plate type, hollow can, screw, suction or even umbrella type piles. The base member may be configured to be driven into or bear on the sea bed via the at least one lifting mechanism moving the support leg or rod. The at least one lifting mechanism may be a jacking mechanism. The at least one lifting mechanism may be a hydraulic, electrical or mechanically actuated jacking mechanism. The at least one lifting mechanism maybe telescopic. The jacking mechanism may be a screw jack mechanism.

The at least one support leg may be adjustable in length. The apparatus may comprise a leg housing attached to the load frame configured to adjust the length of the at least one support leg. Each support leg may be connected to a leg housing. Each leg may be adjustable in length relative to the frame body.

The support system is designed to be reusable on different wellhead sites. The support rods and attached base supports can be retracted at the completion of operations on the well.

Components of the support system may be integrated into components of a BOP or LRP. Components of the support system may be integrated into components of the lower BOP.

According to a second aspect of the invention, there is provided a system for supporting a subsea wellhead, the system comprising:

a frame apparatus configured to be connected to the wellhead or equipment mounted on the wellhead, and

at least one lifting mechanism configured to apply a force to the frame apparatus to reduce vertical loading forces acting on the wellhead.

Preferably the frame apparatus is configured to be connected to a spool. The spool may be attached to the wellhead. The spool may be attached to a Christmas tree attached to the wellhead.

Embodiments of the second aspect of the invention may include one or more features of the first aspect of the invention or its embodiments, or vice versa.

According to a third aspect of the invention, there is provided a method for installing a supporting system on a subsea wellhead, the method comprising

providing a support system comprising

a frame apparatus configured to be connected to the wellhead, and at least one lifting mechanism configured to extend and retract at least one base section of the frame apparatus;

lowering the support system from a rig or vessel; and

connecting the support system to the wellhead.

The method may comprise attaching the support system to a wellhead running tool prior to lowering the support system from a rig or vessel. The method may comprise connecting the support system to the high-pressure housing on the wellhead.

The method may comprise performing a pressure test or over-pull operation to confirm the integrity of the connection between the wellhead and the support system.

The method may comprise actuating the at least one lifting mechanism to extend the at one base section of the frame apparatus into the seabed.

The method may comprise preloading the support system by applying an upward force to the support system. The method may comprise locking the support system in a preloaded state.

The method may comprise actuating the at least one lifting mechanism until a

predetermined upward force is applied to the wellhead. The predetermined force may be equal to the weight of drilling or production equipment to be attached to the wellhead.

The method may comprise lowering a piece of drilling or production equipment from a vessel or rig. The piece of drilling or production equipment may be landed on and/or connected to the support system. The method may comprise connecting the piece of drilling or production equipment to a spool in the support system.

The method may comprise connecting a piece of drilling or production equipment to the support system prior to lowering the support system from a rig or vessel. The method may comprise landing support system and connected piece of drilling or production equipment onto the seabed and/or wellhead.

The method may comprise actuating the at least one lifting mechanism after the piece of drilling or production equipment is connected to the support system. The method may comprise actuating the at least one lifting mechanism until a predetermined upward force is applied which produced a neutral point when the downward force of the weight of the drilling or production equipment is balanced by the upward force of the at least one lifting mechanism.

By providing a support system for a wellhead, the wellhead is protected from vertical loading forces from the downward weight of drilling or production equipment either directly or through cyclic loading.

The above invention may provide a robust, reliable and sturdy support system for a wellhead to mitigate fatigue. The use of a frame apparatus and at least one lifting mechanism may facilitate vertical loads applied to the wellhead to be transferred to the seabed allowing the wellhead to withstanding heavy production and drilling equipment weights and sideways forces.

This may allow a BOP or work-over package to be landed on a wellhead without subjecting the wellhead to additional weight of the equipment (BOP or Work-over package). It may also assist in removing bending loads which would otherwise be transferred into the wellhead or conductor casing, and reduce lateral deflection.

The invention may be utilised on any well, even one which is known to be of reduced structural integrity, to significantly reduce risk of wellhead failure through fatigue and through static loads caused by the weight of the BOP or work-over package.

The support system may be raised and recovered from the seabed.

Embodiments of the third aspect of the invention may include one or more features of the first or second aspects of the invention or its embodiments, or vice versa.

According to a fourth aspect of the invention, there is provided a method of operating a supporting system on a subsea wellhead, the method comprising

providing a support system connected to a wellhead the support system comprising a frame apparatus, and

at least one lifting mechanism configured to extend and retract at least one base section of the frame apparatus; actuate the at least one lifting mechanism to extend the at least one base section of the frame apparatus to engage the seabed and provide an upward force on the support system and attached wellhead;

de-actuate the at least one lifting mechanism when a predetermined upward force is reached.

The method may comprise attaching drilling or production equipment such as a BOP or LRP to the support system.

The method may comprise actuating the at least one lifting mechanism to provide an upward force which may be equal to a downward force acting on the wellhead by the weight of the drilling or production equipment such as a BOP or LRP.

The method may comprise re-actuating the least one lifting mechanism to provide an upward force which equals the exact weight bearing of the drilling or production equipment once it been landed and attached to the support assembly.

The method may comprise actuating the at least one lifting mechanism such that a neutral point of zero vertical load is reached when the drilling or production equipment is attached to the support assembly.

Embodiments of the fourth aspect of the invention may include one or more features of any of the first to third aspects of the invention or their embodiments, or vice versa.

The method of the third aspect and its embodiments, or certain selected steps thereof, may be reversed.

A fifth aspect of the invention therefore relates to a method of removing a support system from a wellhead, the method comprising:

providing a wellhead support system connected to wellhead;

wherein the wellhead support system comprises a frame apparatus connected to the wellhead, and

at least one lifting mechanism;

actuating the at least one lifting mechanism to retract at least one base section of the frame apparatus in a direction away from the seabed; and

disconnecting the frame apparatus from the wellhead. The method may comprise the step of disconnecting drilling or production equipment from the support system prior to actuating the at least one lifting mechanism to retract at least one base section of the frame apparatus in a direction away from the seabed.

The method may comprise disconnecting the support system from the wellhead.

The method may comprise using a vessel or rig to retrieve the disconnected piece of drilling or production equipment. The method may comprise using a vessel or rig to retrieve the disconnected piece of drilling or production equipment

Embodiments of the fifth aspect of the invention may include one or more features of any of the first to fourth aspects of the invention or their embodiments, or vice versa.

According to a sixth aspect of the invention, there is provided a method of supporting a subsea wellhead for decommissioning or workover operations, the method comprising providing a support system comprising

a frame apparatus configured to be connected to the wellhead, and

at least one lifting mechanism configured to extend and retract at least one base section of the frame apparatus;

lowering the support system from a rig or vessel; and

connecting the support system to the wellhead.

Embodiments of the sixth aspect of the invention may include one or more features of any of the first to fifth aspects of the invention or their embodiments, or vice versa.

According to a seventh aspect of the invention, there is provided a kit of parts for supporting a subsea wellhead, the kit of parts including:

a frame apparatus configured to be connected to the wellhead or a component attached to a wellhead, and

at least one lifting mechanism.

Preferably, the frame apparatus has a frame body. The frame apparatus may have at least one support leg or rod. Preferably the frame apparatus has a plurality of support legs or rods. Preferably the kit of parts comprises a spool. Preferably the spool is an in-line spool. Further preferably the spool is load bearing.

Each at least one support leg or rod may have a base member configured to engage the seabed or a structure such as an over trawl structure.

Embodiments of the seventh aspect of the invention may include one or more features of any of the first to sixth aspects of the invention or their embodiments, or vice versa.

According to an eighth aspect of the invention, there is provided a modular system for supporting wellhead equipment, the modular system comprising:

a frame apparatus configured to be connected to a wellhead, and

at least one lifting mechanism configured to apply a force to the frame apparatus to reduce vertical loading forces acting on the wellhead.

The wellhead equipment may be a wellhead, BOP, LRP and/or Christmas tree.

Embodiments of the eighth aspect of the invention may include one or more features of any of the first to seventh aspects of the invention or their embodiments, or vice versa.

Brief Description of the Drawings

There will now be described, by way of example only, various embodiments of the invention with reference to the drawings, of which:

Figure 1 is a schematic side view of a support assembly showing a support apparatus in accordance with a first embodiment of the invention connected to a wellhead and a BOP assembly;

Figure 2 is a schematic plan view showing the support apparatus of Figure 1 in accordance with an embodiment of the invention with the BOP assembly removed for clarity; Figure 3 is a schematic side view of a support assembly showing a support apparatus in in accordance with an embodiment of the invention connected to a Christmas tree mounted on a wellhead and a LRP assembly;

Figure 4 is a schematic side view of a support assembly showing a support apparatus in accordance with an embodiment of the invention connected to a wellhead, Christmas tree and a BOP assembly and mounted on Over Trawl Structure (OTS);

Figure 5 is a schematic side view of a support assembly showing a support apparatus in accordance with an embodiment of the invention connected to a wellhead and a BOP assembly by BOP integrated inline spool.

Figure 6 is a schematic side view of a support assembly showing a support apparatus in accordance with an embodiment of the invention with lifting mechanisms located on the base of the support legs;

Figure 7 is a schematic side view of a support assembly of Figure 6 connected to a wellhead and a BOP assembly;

Figure 8 is a schematic side view of a support assembly of Figure 6 connected to a Christmas tree mounted on a wellhead and a LRP assembly;

Figure 9 is a schematic side view of a support assembly of Figure 6 connected to a wellhead, Christmas tree and a BOP assembly and mounted on Over Trawl Structure (OTS);

Figure 10 is a schematic side view of a support assembly of Figure 6 connected to a wellhead and a BOP assembly by BOP integrated inline spool; and

Figure 11 is a schematic side view of a support apparatus in accordance with an embodiment of the invention with a load frame attached directly to a wellhead connector via a wellhead connector housing. Detailed Description

Referring firstly to Figure 1 , there is shown an apparatus 10 for mitigating or removing downward load acting on a wellhead. In the examples described, the invention is applied to a subsea wellhead in which the loads acting on the wellhead include the weight of subsea equipment and cyclic loading from wind, waves and swell acting on a rig.

In Figure 1 , the support assembly is used to support a Blow Out Preventer (BOP)

Assembly. The BOP is used during workover and drilling operations to control flow and seal the well in the event of an uncontrolled kick.

The support assembly 10 comprises a frame 12 and a spool 14. The spool 14 has a body 16 configured to connect to an upper mandrel 18 at one end and a lower connector 20 at the other end. The upper mandrel 18 is configured to connect to a BOP assembly 22. The BOP assembly connects to the upper mandrel 18 via a BOP-wellhead connector 24.

The lower connector 20 is configured to connect to a wellhead 26. The upper mandrel 18 and lower connector 20 are attached to the spool via standard API connections such as flange/spool and clamp in order that different models of BOP/wellhead connectors can be accommodated. Alternatively, the spool 14 and upper mandrel 18 may be manufactured as a single unit. The spool 14 and upper mandrel 18 may be integrally formed.

As shown in Figures 1 and 2, the frame 12 comprises a load frame 30. The load frame 30 is attached to the spool 14. The load frame 30 is supported by support rods 32. An upper end 32a of the support rods 32 are connected to the load frame 30 via lifting mechanisms 34. The lower end 32b of the support rod 32 is connected to a base member (foot) 36 which is designed to engage the seabed. The base member 36 may be detachable from the support rod 32, in order that base member types specific to the seabed conditions may be fitted to the lower end 32a of the support rods 32.

The apparatus may comprise a leg housing (not shown) attached to the load frame. The leg housing may be configured to adjust the length of support rods or legs 32 In this example, the load frame 30 is a four-armed girder frame. However, it will be appreciated that the design of the load frame 30 can be varied to suit well site-specific access requirements.

The base member 36 may be used to secure the support assembly to the seabed. The design of the base members 36 can be varied to suit the site-specific seabed/mudline conditions and may take the form of simple plates if the seabed is hard or either cans or piles in the event of a soft seabed. The base may be selected from plate type, hollow can, screw, suction or even umbrella type piles. Irrespective which type of base member is employed, the base member is driven into or bears on the sea bed, via the lifting mechanism 34 and support rod 32.

The lifting mechanism 34 is a hydraulic jacking mechanism controlled remotely from the surface. It will be appreciated that other types of lifting mechanisms may be used including but not limited to electrical or mechanical jacking mechanisms. The lifting mechanism 34 may alternatively or optionally be operated via a Remote Operated Vehicle (ROV) or umbilical remotely from the surface.

Each lifting mechanism 34 is configured to act independently of each other should the seabed have different elevations/soil conditions. Alternatively, each lifting mechanism 34 is configured to act simultaneously with each other.

The lifting mechanism 34 is configured to move the support rod relative to the load frame 30. The lifting mechanism 34 is configured to raise and/or lower the support rods 32 relative to the load frame 30.

In use, the support assembly 10 is deployed from either a rig or a vessel (not shown). The support assembly 10 is run on drill pipe and a standard wellhead running tool maybe used to connect the support assembly to the drill pipe. Alternatively, the support apparatus 110 may be run on a line or wire. Once landed onto the wellhead 26 the lower connector 20 is actuated to lock the support assembly 10 to the wellhead 26. The lower connector 20 is pressure tested/over-pull tested to confirm integrity. On the lower end of the support rods 32 are attached base members 36 which are driven into the seabed by actuating the lifting mechanism 34 to move the support rods 32 and attached base members 36 in a downward direction shown as arrow‘X’ in Figure 1.

The support rods 32 may include a telescopic extending mechanism to reduce their overall length.

Once the support assembly is anchored on the seabed, the lifting mechanism is operated to move the support rods 32 and attached base members 36 in a downward direction until the required upward force is applied to the assembly 10 and attached wellhead, shown as arrow Ύ’ in Figure 1.

Instrumentation (not shown) on the support assembly 10 provides accurate indication of the upward force applied to the support assembly 10 and wellhead. The upward force is gradually increased until a predetermined upward force equivalent to the downward loading of the BOP equipment is reached. This upward force should be equal to the weight (in water) of the BOP assembly 22 to be used on the well.

Once the predetermined upward force has been applied to the support assembly 10 and attached wellhead, the running tool is released from the support assembly and the BOP is deployed.

The BOP assembly 22 is landed and connected to upper mandrel 18 on the support assembly 10 and locked in place. The jacking mechanism 34 may require further actuation to re-adjust the upward force applied to the support assembly 10 and wellhead 26 to adjust to the exact weight of the BOP and optionally take account of sea conditions.

The jacking mechanism 34 is actuated to achieve as closely as possible a‘neutral’ point of zero vertical load acting on the wellhead in an upward or downward direction when the BOP equipment is in place on the wellhead.

On conclusion of drilling/production operations on the well and removal of the BOP assembly, the jacking mechanism is actuated to withdraw the support member from the seabed. The support assembly is then recovered to surface and reused. In one example, a shear pin mechanism holds the base member to the support rods. In the event that the base member cannot be withdrawn from the seabed, the base member may thus be released from the support rod.

The support apparatus will now be described in alternative modes of operation.

Figure 3 shows the support assembly 100 used on a wellhead which has a Christmas tree installed. Christmas trees are used for well production (hydrocarbon out) or injection (water or gas in) operations to regulate the flow.

The Christmas tree assembly 102 comprises an upper Christmas tree mandrel 104, and Christmas tree master valve block 106 and a lower Christmas tree connector 108.

Typically, the types of Christmas tree deployed on wells varies considerably both in terms of design and size. They are either of a horizontal or spool design or are conventional with either mono-bore or dual bores through a master valve block.

Typically a Lower Riser Package 160 is used to connected a floating drilling rig or vessel (not shown) to a subsea Christmas tree 102. The LRP 160 consists of an emergency disconnect package (EDP) 162, LRP main valve block 164 and LRP lower connector 166.

The support apparatus 110 is configured to restrict the downward weight of the LRP 160 acting on the Christmas tree and wellhead.

The apparatus 110 comprises a frame 112 and a spool 114.

The spool 114 has a body 116 configured to connect to an upper mandrel 118 at one end and a lower connector 120 at the other end. The upper mandrel 118 is configured to connect to a LRP assembly 160. The LRP assembly 160 connects to the upper mandrel 118 via a LRP lower connector 166. The inline spool 114 is configured to suit the type of Christmas tree it is deployed onto. The inline spool 114 may have dual bore, single production bore or be‘full bore’ with typically 13 5/8” connectors & mandrels or 18 3/4” connectors & mandrels.

The lower connector 120 is configured to connect to an upper Christmas tree mandrel 104 of a Christmas tree assembly 102. The Christmas tree assembly 102 is installed on a wellhead 126 by coupling the wellhead upper mandrel 126a to Christmas tree lower connector 108.

The frame 112 comprises a load frame 130, support rods 132 and base members 136.

The load frame 130 is attached to the inline spool 114. In this example, the load frame 130 is a four-armed girder frame. However, it will be appreciated that the design of the load frame 130 can be varied to suit well site-specific access requirements.

The load frame 130 is supported by support rods 132. Each upper end 132a of the support rods 132 are connected to the load frame 130 via a lifting mechanism 134. The lower end 132b of the support rod 132 is connected to a support base 136 which is designed to engage the seabed.

Each support base 136 may be detachable, in order that support bases specific to the seabed conditions may be fitted to the lower end 132b of the support rods. The feet 136 may be standard plate type, hollow can, screw or even load-actuated‘umbrella type piles. The design of the feet is site specific.

The support apparatus 110 is deployed from either a rig or a vessel. The support apparatus 110 is run on drill pipe and a standard wellhead running tool may be used to connect the support apparatus to the drill pipe. Alternatively, the support apparatus 110 may be run on a line or wire. Once landed onto the Christmas tree 102, the lower connector 120 is actuated to lock the support apparatus 110 to upper Christmas tree mandrel 104 of a Christmas tree assembly 102.

The lower connector 120 is pressure tested/over-pull tested to confirm integrity.

The lifting mechanism 134 is operated to move the support rods 132 in a downward direction shown as arrow‘X’ in Figure 3 to push the support members into the seabed 140.

Once the support members 136 have engaged and are anchored on the seabed 140, a further downward force is applied to the support rods 132 by the lifting mechanism 134 to produces an upward force on the support apparatus 110, Christmas tree 102 and wellhead 126, shown as arrow Ύ’ in Figure 3. Instrumentation (not shown) on the support assembly 110 provides accurate indication of the upward force applied to the support apparatus 110, Christmas tree 102 and wellhead 126. The upward force is gradually increased until a predetermined upward force is reached. In this example, the predetermined upward force is equivalent to the weight of the LRP equipment. The predetermined upward force may be equivalent to the weight of the LRP equipment and the Christmas tree. Once the predetermined upward force has been applied the running tool attached to the support apparatus 110 is released and the LRP assembly is deployed.

The LRP assembly 160 is landed and connected to upper mandrel 118 on the support assembly 110 and locked in place. The lifting mechanism 134 may require further actuation to re-adjust the upward force to adjust to the exact weight bearing of the LRP and optionally take account of sea conditions.

The lifting mechanism 134 is actuated to achieve as closely as possible a‘neutral’ point of zero load in an upward or downward when the LRP equipment 160 is in place on the wellhead. The lifting mechanism 134 may be actuated via a surface umbilical or via ROV intervention.

In the event that the Christmas Tree 102 has an Over Trawl Structure (OTS) or Wellhead Protection Structure (WPS) installed to protect the Christmas Tree from fishing activities, the support assembly may be designed to span the OTS or WPS such that the support members can engage the seabed.

The support apparatus is capable supporting drilling/production equipment.

Figure 4 shows support assembly 210 used to support a wellhead 226 which has a Christmas tree 202 installed and an Over Trawl Structure (OTS) 280. The support assembly 210 is configured to restrict the downward weight of the LRP 260 acting on the Christmas tree and wellhead.

The connections between the LRP 260, support apparatus 210, Christmas Tree 202 and wellhead 226 are the same as described in relation to Figure 3 above. However, in this case an OTS 280 is present which is capable of being used as a‘load bearing’ platform. The support assembly 210 has specially shaped base members 236 which are configured to engage the OTS 280 and mount the support assembly 210 directly onto the OTS 280.

By anchoring the support assembly 210 directly onto the OTS 280 rather than the seabed the weight of the drilling, production or workover equipment is transferred to the seabed through the OTS rather than into the seabed directly.

The lifting mechanism 234 is configured to move the support rods 232 and base members 236 in a downward direction shown as arrow‘X’ in Figure 4. The downward force exerted against the anchored OTS structure produces a resistive upward force on the support assembly 210 and connected Christmas tree 202 and wellhead 226, shown as arrow Ύ’ in Figure 4.

The upward force is gradually increased until a predetermined upward force is reached. In this example, the predetermined upward force is equivalent to the weight of the LRP equipment. The predetermined upward force may be equivalent to the weight of the LRP equipment and the Christmas tree. Once the predetermined upward force has been applied the running tool attached to the support assembly 210 is released and the LRP assembly is deployed.

Figure 5 shows a schematic side view of a support assembly for a drilling rig blowout preventer (BOP) assembly. The support assembly 310 is similar to the support assembly 10 described in Figure 1 and will be understood from the description of Figure 1 above. However, the inline spool of the support assembly 310 is incorporated into, and is integral with, the BOP assembly 322.

The spool is incorporated between the wellhead connector 324 and lower BOP ram body 315 of the BOP assembly 322. The wellhead connector 324 is attached directly to the spool. The wellhead connector may be attached to the BOP integrated spool by connectors and/or API flanges.

The load frame 330 is connected to the lower BOP frame 322a. Alternatively, the load frame may be incorporated in the lower BOP frame 322a. The spool is attached to the load frame 330 by a connector, such as a clamp. The spool may have a profile shape configured to receive and/or connect to a clamp to facilitate the attachment of the load frame to the spool.

The BOP assembly 322 and support assembly 310 are connected to one another on the surface and are lowered as one unit to be connected to the wellhead 326. Alternatively, the support assembly 310 may be installed on the wellhead 326 prior to the BOP assembly 322 being lowered and connected to the support assembly.

By providing a support assembly which is incorporated into, and is integral with the BOP assembly separate operations to install/remove the support assembly and the BOP are avoided.

In the above embodiments, the lifting mechanism is located at an upper end of the support rods or legs. The lifting mechanism is described as connecting the support legs to the load frame.

Figures 6 to 11 describe alternative embodiments of the support apparatus where the lifting mechanism is located at a lower end of the support rods or legs. In these

embodiments the lifting mechanism connects the support legs to actuating rods which are connected to base members.

As shown in Figure 6, the support apparatus 410 comprises a frame 412 and a spool 414. The spool 414 has a body 416 configured to connect to an upper mandrel 418 at one end and a lower connector 420 at the other end. The upper mandrel 418 is configured to connect to a BOP.

The frame 412 comprises a load frame 430. The load frame 430 is attached to the spool 414 via a mandrel 414a. The load frame 430 is supported by support legs or rods 432. In this example the apparatus has four legs. The legs 432 may have a fixed length or adjustable in length via a leg length adjustment housing 433. An upper end 432a of the support rods 432 are connected to the load frame 430. The lower end 432b of the support rod 432 is connected to a base member (foot) 436 via a lifting mechanism 434 and an actuating rod 437. The base member 436 is designed to engage the seabed. The base member 436 may be detachable from the support rod 432 or actuating rod 437, in order that base member types specific to the seabed conditions may be fitted to the lower end 432b of the support rods 432.

The load frame 430 is a four-armed girder frame. However, it will be appreciated that the design of the load frame 430 can be varied to suit well site-specific access requirements.

The base member 436 may be used to secure the support assembly to the seabed. The design of the base members 436 can be varied to suit the site-specific seabed/mudline conditions and may take the form of simple plates if the seabed is hard or either cans or piles in the event of a soft seabed. The base may be selected from plate type, hollow can, screw, suction or even umbrella type piles. Irrespective which type of base member is employed, the base member is driven into or bears on the sea bed, via the lifting mechanism 434 and support rod 432.

The lifting mechanism 434 is a hydraulic jacking mechanism controlled remotely from the surface. It will be appreciated that other types of lifting mechanisms may be used including but not limited to electrical and/or mechanical jacking mechanisms. The lifting mechanism 434 may alternatively or optionally be operated via a Remote Operated Vehicle (ROV) or umbilical remotely from the surface.

In this example the lifting mechanisms are located between the base members 436 and actuating rods 437. The actuating rods 437 are connected to the support legs or rods 432. It will be appreciated that other types of lifting mechanisms may be used including but not limited to electrical or mechanical jacking mechanisms

Each lifting mechanism 434 is configured to act independently of each other should the seabed have different elevations/soil conditions. Alternatively, each lifting mechanism 434 is configured to act simultaneously with each other.

The lifting mechanism 434 is configured to move the support rod and the load frame 430. The lifting mechanism 434 is configured to extend or retract the actuating rods 437 to move the load frame 430 and support legs 432 relative to the base members 436.

The load frame 430 and support rods 432 are configured to move together relative to the base members. The leg housing 433 provides a‘coarse’ length adjustment to the support rod 432. The leg housing 433 is configured to reversibly engage the support rod to clamp it in an extended or retracted position and to release it to allow the length of the support rod to be extended or retracted. The clamp may be mechanical pin. It will be appreciated that other types of clamping mechanisms may be used including but not limited to mechanical, electrical and/or hydraulically operated clamp arrangements.

In operation should the full travel of the lifting mechanism and actuating rod 437 be reached before the required upward force is attained, the lifting mechanism can be reversed and the actuating rod 437 retracted. The support rod 432 can then be extended via the leg (length adjustment) housing 433. The lifting mechanism may then be operated to again extend actuating rod 437 and lower the base member 436 until the required upwards force is achieved.

The support apparatus will now be described in alternative modes of operation.

Figure 7 shows the support assembly 500 used to support a Blow Out Preventer (BOP) Assembly. The BOP is used during workover and drilling operations to control flow and seal the well in the event of an uncontrolled kick.

The components and operation of the support assembly 500 are similar to the support assembly 10 of Figure 1. Figure 7 and will be understood from the description of Figure 1. However, the support assembly 500 has lifting mechanisms 534 located at a lower end of the support rods or legs 532.

The support assembly 510 comprises a support apparatus 510 comprising a frame 512 and a spool 514. The spool 514 has a body 516 configured to connect to an upper mandrel 518 at one end and a lower connector 520 at the other end. The upper mandrel 518 is configured to connect to a BOP assembly 522. The BOP assembly connects to the upper mandrel 518 via a BOP-wellhead connector 524.

The lower connector 520 is configured to connect to wellhead 526. The upper mandrel 518 and lower connector 520 are attached to the spool via standard API connections such as flange/spool and clamp in order that different models of BOP/wellhead connectors can be accommodated. Alternatively, the spool 514 and upper mandrel 518 may be manufactured as a single unit. The spool 514 and upper mandrel 518 may be integrally formed. As shown in Figures 7, the frame 512 comprises a load frame 530. The load frame 530 is attached to the spool 514. The load frame 530 is supported by support rods 532. An upper end 532a of the support rods 532 are connected to the load frame 530 via a leg housing 535. The lower end 532b of the support rod 532 is connected to a base member (foot) 536 via a lifting mechanism 534. The base member 536 is designed to engage the seabed.

The base member 536 may be detachable from the support rod 532, in order that base member types specific to the seabed conditions may be fitted to the lower end 532a of the support rods 532.

In this example, the load frame 530 is a four-armed girder frame. However, it will be appreciated that the design of the load frame 530 can be varied to suit well site-specific access requirements.

The base member 536 may be used to secure the support assembly to the seabed. The design of the base members 536 can be varied to suit the site-specific seabed/mudline conditions and may take the form of simple plates if the seabed is hard or either cans or piles in the event of a soft seabed. The base may be selected from plate type, hollow can, screw, suction or even umbrella type piles. Irrespective which type of base member is employed, the base member is driven into or bears on the sea bed, via the lifting mechanism 534 and support rod 532.

The lifting mechanism 534 is a hydraulic screw jack mechanism controlled remotely from the surface. It will be appreciated that other types of lifting mechanisms may be used including but not limited to electrical or mechanical jacking mechanisms. The lifting mechanism 534 may alternatively or optionally be operated via a Remote Operated Vehicle (ROV) or umbilical remotely from the surface.

Each lifting mechanism 534 is configured to act independently of each other should the seabed have different elevations/soil conditions. Alternatively, each lifting mechanism 534 is configured to act simultaneously with each other.

The lifting mechanism 534 is configured to extend or retract the actuating rods 537 to move the load frame 530 and support legs 532 relative to the base members 536.

In use, the support assembly 510 is deployed from either a rig or a vessel (not shown).

The support assembly 510 is run on drill pipe and a standard wellhead running tool maybe used to connect the support assembly to the drill pipe. Once landed onto the wellhead 526 the lower connector 520 is actuated to lock the support assembly 510 to the wellhead 526. The lower connector 520 is pressure tested/over-pull tested to confirm integrity.

On the lower end of the support rods 532 are attached the lifting mechanisms 534, actuating rods 537 and base members 536. The base members are driven into the seabed by actuating the lifting mechanism 534 to move the actuating rods 537 and attached base members 536 in a downward direction shown as arrow‘X’ in Figure 7. The support rods 532 or actuating rods 537 may include a telescopic extending mechanism to reduce their overall length.

Once the support apparatus is anchored on the seabed, the lifting mechanism is operated to move the actuating rods 537 and attached base members 536 in a downward direction until the required upward force is applied to the assembly 510 and attached wellhead, shown as arrow Ύ’ in Figure 1.

Instrumentation (not shown) on the support assembly 510 provides accurate indication of the upward force applied to the support assembly 510 and wellhead. The upward force is gradually increased until a predetermined upward force equivalent to the downward loading of the BOP equipment is reached. This upward force should be equal to the weight (in water) of the BOP assembly 522 to be used on the well.

Once the predetermined upward force has been applied to the support apparatus 510 and attached wellhead, the running tool is released from the support assembly and the BOP is deployed.

The BOP assembly 522 is landed and connected to upper mandrel 518 on the support assembly 510 and locked in place. The jacking mechanism 534 may require further actuation to re-adjust the upward force applied to the support assembly 510 and wellhead 526 to adjust to the exact weight of the BOP and optionally take account of sea conditions.

The jacking mechanism 534 is actuated to achieve as closely as possible a‘neutral’ point of zero vertical load acting on the wellhead in an upward or downward direction when the BOP equipment is in place on the wellhead. On conclusion of drilling/production operations on the well and removal of the BOP assembly, the jacking mechanism is actuated to withdraw the support member from the seabed. The support assembly is then recovered to surface and reused.

In one example, a shear pin mechanism holds the support member to the support rods. In the event that the support member cannot be withdrawn from the seabed, the support member may thus be released from the support rod.

Figure 8 shows the support assembly 600 used on a wellhead which has a Christmas tree installed. Christmas trees are used for well production or injection (water or gas in) operations to regulate the flow.

The components and operation of the support assembly 600 are similar to the support assembly 100 of Figure 3. Figure 8 and will be understood from the description of Figure 3. However, the support assembly 600 has lifting mechanisms 634 located at a lower end of the support rods or legs 632.

Figure 8 shows the support assembly 600 used on a wellhead which has a Christmas tree installed. Christmas trees are used for well production or injection (water or gas in) operations to regulate the flow.

The Christmas tree assembly 602 comprises an upper Christmas tree mandrel 604, and Christmas tree master valve block 606 and a lower Christmas tree connector 608.

Typically, the types of Christmas tree deployed on wells varies considerably both in terms of design and size. They are either of a horizontal or spool design or are conventional with either mono-bore or dual bores through a master valve block.

Typically a Lower Riser Package 660 is used to connect a floating drilling rig or vessel (not shown) to a subsea Christmas tree 602. The LRP 660 consists of an emergency disconnect package (EDP) 662, LRP main valve block 664 and LRP lower connector 666.

The support apparatus 610 is configured to restrict the downward weight of the LRP 660 acting on the Christmas tree and wellhead. The apparatus 610 comprises a frame 612 and a spool 614.

The spool 614 has a body 616 configured to connect to an upper mandrel 618 at one end and a lower connector 620 at the other end. The upper mandrel 618 is configured to connect to a LRP assembly 660. The LRP assembly 660 connects to the upper mandrel 618 via a LRP lower connector 666. The inline spool 614 is configured to suit the type of Christmas tree it is deployed onto. The inline spool 614 may have dual bore, single production bore or be‘full bore’ with typically 13 5/8” connectors & mandrels or 18 3/4” connectors & mandrels.

The lower connector 620 is configured to connect to an upper Christmas tree mandrel 604 of a Christmas tree assembly 602. The Christmas tree assembly 602 is installed on a wellhead 626 by coupling the wellhead upper mandrel 626a to Christmas tree lower connector 608.

The frame 612 comprises a load frame 630, support legs (rods) 632 and leg adjustment housing 635. The load frame 630 is attached to the inline spool 614. In this example, the load frame 630 is a four-armed girder frame. However, it will be appreciated that the design of the load frame 630 can be varied to suit well site-specific access requirements.

The load frame 630 is supported by support legs 632. Each upper end 632a of the support leg 632 are connected to the load frame 630 via leg adjustment housing 635 configured to adjust the length of the leg. The lower end 632b of the support rod 632 is connected to a lifting mechanism 634. The lifting mechanism 634 is attached to actuating rod 637 which is connected a base member 636.

Each support base member 636 may be detachable, in order that base members specific to the seabed conditions may be fitted to the lower end 632b of the support legs and actuating rod 637. The base member (feet) 636 may be standard plate type, hollow can, screw or even load-actuated‘umbrella type piles. The design of the base member is site specific.

The support apparatus 610 is deployed from either a rig or a vessel. The support apparatus 610 is run on drill pipe and a standard wellhead running tool may be used to connect the support apparatus to the drill pipe. Alternatively, the support apparatus 610 may be run on a line or wire. Once landed onto the Christmas tree 602, the lower connector 620 is actuated to lock the support apparatus 610 to upper Christmas tree mandrel 604 of a Christmas tree assembly 602.

The lower connector 620 is pressure tested/over-pull tested to confirm integrity.

The lifting mechanism 634 is operated to extend the actuating rods 637 in a downward direction shown as arrow‘X’ in Figure 8 to push the base members into the seabed 640.

Once the base members 636 have engaged and are anchored on the seabed 640, a further downward force is applied to the actuating rods 637 by the lifting mechanism 634 to produces an upward force on the support apparatus 610, Christmas tree 602 and wellhead 626, shown as arrow Ύ’ in Figure 8.

Instrumentation (not shown) on the support assembly 610 provides accurate indication of the upward force applied to the support apparatus 610, Christmas tree 602 and wellhead 626. The upward force is gradually increased until a predetermined upward force is reached. In this example, the predetermined upward force is equivalent to the weight of the LRP equipment. The predetermined upward force may be equivalent to the weight of the LRP equipment and the Christmas tree. Once the predetermined upward force has been applied the running tool attached to the support apparatus 610 is released and the LRP assembly is deployed.

The LRP assembly 660 is landed and connected to upper mandrel 618 on the support assembly 610 and locked in place. The lifting mechanism 634 may require further actuation to re-adjust the upward force to adjust to the exact weight bearing of the LRP and optionally take account of sea conditions.

The lifting mechanism 634 is actuated to achieve as closely as possible a‘neutral’ point of zero load in an upward or downward when the LRP equipment 660 is in place on the wellhead. The lifting mechanism 634 may be actuated via a surface umbilical or via ROV intervention.

In the event that the Christmas Tree 602 has an Over Trawl Structure (OTS) or Wellhead Protection Structure (WPS) installed to protect the Christmas Tree from fishing activities, the support assembly may be designed to span the OTS or WPS such that the support members can engage the seabed.

The support apparatus is capable supporting drilling/production equipment.

Figure 9 shows support assembly 700 used to support a wellhead 726 which has a Christmas tree 702 installed and an Over Trawl Structure (OTS) 780. The support assembly 700 is configured to restrict the downward weight of the LRP 760 acting on the Christmas tree and wellhead.

The components and operation of the support assembly 700 are similar to the support assembly 200 of Figure 4. Figure 9 and will be understood from the description of Figure 4. However, the support assembly 700 has lifting mechanisms 734 connected to the load frame 730. Alternatively, the apparatus may comprise support legs and the lifting mechanisms 734 may connect the support legs to the base members 736.

Figure 9 shows support assembly 710 used to support a wellhead 726 which has a Christmas tree 702 installed and an Over Trawl Structure (OTS) 780. The support assembly 710 is configured to restrict the downward weight of the LRP 760 acting on the Christmas tree and wellhead.

The connections between the LRP 760, support apparatus 710, Christmas Tree 702 and wellhead 726 are the same as described in relation to Figure 8 above. However, in this case an OTS 780 is present which is capable of being used as a‘load bearing’ platform.

The support assembly 710 has specially shaped base members 736 which are configured to engage the OTS 780 and mount the support assembly 710 directly onto the OTS 780.

By anchoring the support assembly 710 directly onto the OTS 780 rather than the seabed the weight of the drilling, production or workover equipment is transferred to the seabed through the OTS rather than into the seabed directly.

The lifting mechanism 734 is configured to extend the actuating rods 737 and move the base members 736 in a downward direction shown as arrow‘X’ in Figure 9. The downward force exerted against the anchored OTS structure produces a resistive upward force on the support assembly 710 and connected Christmas tree 702 and wellhead 726, shown as arrow Ύ’ in Figure 9.

The upward force is gradually increased until a predetermined upward force is reached. In this example, the predetermined upward force is equivalent to the weight of the LRP equipment. The predetermined upward force may be equivalent to the weight of the LRP equipment and the Christmas tree. Once the predetermined upward force has been applied the running tool attached to the support assembly 710 is released and the LRP assembly is deployed.

Figure 10 shows a schematic side view of a support assembly 800 for a drilling rig blowout preventer (BOP) assembly where the inline spool of the support apparatus 810 is incorporated into, and is integral with, the BOP assembly 822.

The components and operation of the support assembly 800 are similar to the support assembly 300 of Figure 5. Figure 10 will be understood from the description of Figure 5. However, the support assembly 800 has lifting mechanisms 834 located at a lower end of the support rods or legs 832.

The inline spool is incorporated between the wellhead connector 824 and lower BOP ram body 815 of the BOP assembly 822. The wellhead connector 824 is attached directly to the spool. The wellhead connector may be attached to the BOP integrated spool by connectors and/or API flanges.

The load frame 830 is connected to the lower BOP frame 822a. Alternatively, the load frame may be incorporated in the lower BOP frame 822a.

The spool is attached to the load frame 830 by a connector, such as a clamp. The spool may have a profile shape configured to receive and/or connect to a clamp to facilitate the attachment of the load frame to the spool.

The BOP assembly 822 and support assembly 810 are connected to one another on the surface and are lowered as one unit to be connected to the wellhead 826. Alternatively, the support assembly 810 may be installed on the wellhead 826 prior to the BOP assembly 822 being lowered and connected to the support assembly. By providing a support assembly which is incorporated into, and is integral with the BOP assembly separate operations to install/remove the support assembly and the BOP are avoided.

In the above embodiments, the lifting mechanism is located at an upper end of the support rods or legs. The lifting mechanism is described as connecting the support legs to the load frame.

Figure 11 shows support apparatus 910 where the load frame 930 is incorporated in a wellhead connector housing 944. This reduces the height of the support apparatus 910 when mounted or connected to the wellhead. The remaining components and operation of the support assembly 910 are similar to the support assembly 410 of Figure 6. The load frame 930 is attachable directly to a wellhead connector via a wellhead connector housing 944.

By providing a support assembly which is incorporated into, and is integral with the BOP assembly separate operations to install/remove the support assembly and the BOP are avoided.

Throughout the specification, unless the context demands otherwise, the terms 'comprise' or 'include', or variations such as 'comprises' or 'comprising', 'includes' or 'including' will be understood to imply the inclusion of a stated integer or group of integers, but not the exclusion of any other integer or group of integers.

Furthermore, relative terms such as”,“lower”,“upper”,“up”,“down”,“downwar d”,“upward”, “above”,“below” and the like are used herein to indicate directions and locations as they apply to the appended drawings and will not be construed as limiting the invention and features thereof to particular arrangements or orientations.

The invention provides a system for supporting wellhead equipment. The system comprises a frame apparatus configured to be connected to a wellhead or equipment mounted on a wellhead and at least one lifting mechanism configured to apply a force to the frame apparatus to reduce vertical loading forces acting on the wellhead. Embodiments of the present invention deliver several advantages over the wellhead supports described in the prior art.

The invention may reduce, remove or mitigate vertical loads applied to a subsea wellhead and/or Christmas Tree equipment by providing a support apparatus which connects to the wellhead and/or Christmas Tree by a load bearing inline spool piece. The load bearing inline spool piece may connect and support a BOP or work-over equipment.

By providing a wellhead support assembly, the invention may eliminate or minimise risk of wellhead failure and mitigate the resultant risk to personnel and the environment.

The invention may be used on old, existing and new subsea wellheads.

On old and existing wellheads, the invention may allow well re-entry operations on subsea wellheads which have limited or no fatigue life remaining, or are known to be structurally compromised. It may allow re-entry of wells which due to structural/fatigue issues in the wellhead/upper conductor are presently not able to be decommissioned. It may also allow re-entry of wells which due to structural/fatigue issues in the wellhead/upper conductor are presently not able to be worked over.

On new wellheads, the invention may provide protection against fatigue of the wellhead and wellhead components throughout operations during the well life. The invention may facilitate an extension of the well life.

The support assembly may be used in different applications on new or existing wells. The support assembly may be used on a wellhead without a guide base or Christmas tree.

It may also be used on a well which has a guide base/structure attached to the wellhead outer conductor LP housing. The support assembly may also be used on a well which has a Christmas Tree and/or an WPS/OTS structure installed.

The support assembly may nullify any downward vertical load acting on a wellhead even when the wellhead is located on an uneven or irregular seabed. The support assembly may be configured with different type of base support members (feet) including piled options to allow for differing seabed conditions including hard or soft soil conditions, cemented and mudline surfaces. The foregoing description of the invention has been presented for the purposes of illustration and description and is not intended to be exhaustive or to limit the invention to the precise form disclosed. The described embodiments were chosen and described in order to best explain the principles of the invention and its practical application to thereby enable others skilled in the art to best utilise the invention in various embodiments and with various modifications as are suited to the particular use contemplated. Therefore, further modifications or improvements may be incorporated without departing from the scope of the invention herein intended.