GB2628085A

GB2628085A - Connectors

Info

Publication number: GB2628085A
Application number: GB2303325.1A
Authority: GB
Inventors: Reinås Lorents; SÆTRE Stian
Original assignee: Equinor Energy AS
Current assignee: Equinor Energy AS
Priority date: 2023-03-07
Filing date: 2023-03-07
Publication date: 2024-09-18
Also published as: GB202305383D0; NO20230288A1; GB2628674B; WO2024186218A1; GB202303325D0; GB2628674A

Abstract

A connector 18 for connecting a subsea wellhead system 16 to a second component 20 is disclosed. The connector 18 comprises a locking element 38 configured to engage with a locking portion 34 of the wellhead system 16 and a locking portion 52 of the second component 20, a gripping element 40 configured to engage with a gripping portion 60 of the wellhead system 16, and a compression element 42. The gripping element 38 and the locking element 40 of the wellhead system 16 are spaced from each other, and the compression element 42 is configured to introduce compression into the wellhead system 16 at least between the locking portion 34 and the gripping portion 60.

Description

CONNECTORS

This disclosure relates to connectors suitable for connecting a subsea wellhead system and a second component.

Connectors for use in connection with subsea wellheads are typically used to connect the subsea wellhead (typically the high pressure wellhead housing) and an element of subsea riser system equipment, for example, but without limitation, a blowout preventer (BOP) -which may comprise a lower stack and a lower marine riser package (LMRP), a Christmas tree (which may also he referred to as a subsea tree), an other element of well control apparatus, or a riser string.

According to a first aspect of the present disclosure, there is provided a connector for connecting a subsea wellhead system to a second component, in which the connector comprises a locking element configured to engage with a locking portion of the wellhead system and a locking portion of the second component, a gripping element configured to engage with a gripping portion of the wellhead system, and a compression element, in hich the Gripping element and the locking element of the connector are spaced from each other, and the compression element is configured to introduce compression into the wellhead system between at least the locking portion and the gripping portion of the first component.

It is to be understood that the compression introduced into the wellhead system by the compression element is additional to any compression that is introduced into the wellhead system when the second component is connected to the wellhead system by the connector. In greater detail, it is known that wellhead systems are normally configured to extend in a vertically upwards direction, and the second component is connected to the vertically uppermost end of the wellhead system. As a result, typically the weight of the second component is exerted on the wellhead system in a vertically downward direction. The compression introduced into the -2 -wellhead system by the connector of the present disclosure is additional to any compression introduced by the second component.

It has been found that subsea wellheads that have been subsea and in use for a period of time before it is desired to connect or reconnect an element of subsea riser system equipment (such as a subsea tree, a tree system spool, a blowout preventer (BOP), a riser string, a kill spool, a tubing hanger spool, a capping stack, an in place capping stack, a kinetic blowout stopper (KBOS) standalone, a high pressure cap, a workover stack, or other element of well control apparatus) may have been exposed to or suffered from damage caused by the previous use. For example, the previous use may have included previous drilling activities and subsequent oil extraction. Such damage may include, for example, one or more fatigue induced cracks in the wellhead. Such cracks may be the result of cyclic loading. They may reduce the effective wall thickness of the wellhead and as a result lessen the strength of the wellhead and increase the risk of mechanical failure of the wellhead.

In a subsea environment it is not easy to identify fatigue induced cracks in the wellhead and, as a safety precaution it may be necessary to assume that such cracks are present. The assumed increased risk of failure of the wellhead may be sufficiently high that connection of an element of subsea riser system equipment to the wellhead, and the performance of subsequent operations through the wellhead, is not possible within the safety limits that govern the activities of drilling rig operators.

Another cause of damage to a subsea wellhead may be high load events, for example accidental impact loads from dropped objects that have hit or landed on the wellhead. Such high impact loads may be the result of direct contact of a source of the high load with the wellhead.

High load events may damage the wellhead as a result of transmission of loads into the wellhead from an element of subsea riser system equipment via the connector that connects that equipment to the wellhead. The high load may be applied to the equipment as a result of accidental impact on the equipment, position loss of riser connected vessel, loss of riser tension which is likely to result in subsequent large -3 -bending loads, loss of wave motion compensation, and subsequent accidental tension loads.

Post event investigations may conclude that the original strength of the wellhead, or parts of the wellhead such as the uppermost part, must be assumed to be reduced as a result of the accidental impact loads, high load event, or fatigue induced loading.

An advantage of the connector of the present disclosure is that the connector may be used in connection with subsea wellheads that may have been exposed to or suffer from such damage as is described above. This is because the introduction of compression into the wellhead by the compression element has the effect of closing any cracks and applying a level of compression to any cracks and the remaining material, and as a result strengthening the wellhead. This may render the wellhead safe for the connection to an element of subsea riser system equipment and make the desired well activity that necessitates the connection of the connector possible. Furthermore, the connector of the present disclosure may avoid the need to replace the wellhead. In the event of a severely damaged wellhead the use of a connector of the present disclosure may have the advantage that it can enable the well activities necessary to established safe closure of the well such that the damaged wellhead may be removed.

A further advantage of the connector of the present disclosure is that if it is used on a undamaged wellhead system the part of the wellhead system that is put in compression will be more protected from damage such as that described above than a wellhead system to which a conventional connector is connected.

In an embodiment of the above embodiment, the connector is a valve assembly connector.

In an embodiment of the above embodiment, the wellhead system comprises one or both of a high pressure casing and a high pressure housing. The one or both of the high pressure casing and a high pressure housing are referred to herein as "the wellhead". -4 -

In an alternative embodiment of the above embodiment, the wellhead system comprises a combination of (i) one or both of a high pressure casing and a high pressure housing (the one or both of the high pressure casing and a high pressure housing are referred to herein as "the wellhead") and (ii) one or both of a low pressure casing and a low pressure housing (the one or both of the low pressure casing and a low pressure housing are referred to herein as "the conductor".

In an embodiment of any of the above embodiments, the wellhead is longitudinally extending with a central axis and an upper end. The upper end of the wellhead has an end face. The end face of the wellhead typically faces toward the surface of the sea. In this context, the upper end is the end that is vertically uppermost when the wellhead is positioned for use and at least partially extending out of the seabed.

In an embodiment of any of the above embodiments, the locking element is configured to engage with a helical thread, a flange, or other known arrangement suitable for connecting the end of the wellhead with a connector. In such embodiments the radially outer surface of the wellhead at the upper end is the wellhead system locking portion, and that locking portion includes a helical thread, a flange, or other known arrangement suitable for connecting the end of a wellhead with a connector.

In an embodiment of any of the above embodiments, the locking element is configured to engage with the upper face of the wellhead or a seal element supported on the upper face of the wellhead. In such an embodiment the locking portion is the upper face of the wellhead or a seal element supported on the upper face of the wellhead.

An advantage of this embodiment of the connector of the present disclosure is that it can be used if the conventionally present means for the connection of the wellhead to a connector is sufficiently damaged that use of the connecting mechanism of a typical connector is not possible. In such circumstances, the connector of the present disclosure can effectively replace the loss of the conventionally present means for the connecting of the wellhead to a connector and allow use of the wellhead without needing to mend or replace the wellhead. Where a sealing element is present on the upper face of the wellhead the sealing element -5 -may be preloaded in compression. This is a prerequisite for the sealing element to work as intended, and thus makes it possible to connect an element of subsea riser system equipment valve assembly to the wellhead despite the damage to the conventionally present means for the connecting of the wellhead to a connector.

An further advantage of this embodiment of the connector of the present disclosure is that in the event that the result of a high load event is that the wellhead is damaged in such a way that the wellhead longitudinal axis deviates from vertical and the longitudinal axis of the upper end of the wellhead is curved, that is the wellhead has been bent due to material distortion under high load and the wellhead shape and form is altered, the connector may still be able to obtain a grip on the wellhead with the gripping element and then apply compression to the wellhead and the sealing element. In such case the connector of the present disclosure will enable the necessary operations to salvage and close the well safely. A conventional connector could not do this to the same extent.

In an embodiment of any of the above embodiments, the locking portion of the second component may include a helical thread, a H4 connector, or other known arrangement suitable for engagement with a connector.

In an embodiment of any of the above embodiments, the locking portions of the wellhead system and the second component are differently configured.

In an embodiment of any of the above embodiments, the locking element comprises a first portion configured to engage with the locking portion of the wellhead system, and a second portion configured to engage with the locking portion of the second component.

In an embodiment of any of the above embodiments, the grip element and the locking element are spaced from each other in the axial direction.

In an embodiment of any of the above embodiments, the compression element is so configured that on activation the compression element introduces tension within the compression element and compression in at least the portion of the wellhead system that extends between the position at which the locking element engages -6 -with the locking portion of the wellhead system, and the position at which the gripping element engages with the gripping portion of the wellhead system.

In an embodiment of any of the above embodiments, the compression element is so configured that on activation the compression element introduces tension within the compression element and compression in at least the portion of the wellhead system that extends between the end face of the wellhead, and the position at which the gripping element engages with the gripping portion of the wellhead system.

In an embodiment of any of the above embodiments, the compression element is so configured that on activation the compression element introduces tension within the compression element and compression in a portion of the connector. In some embodiments the part of the connector in compression is adjacent the end face of the wellhead.

Where the locking portion of the wellhead system includes a thread or other locking profile it is has been found that fatigue induced cracks may be formed extending from a part of the thread or locking profile. For example if the thread or locking profile has a V or U shaped cross-section in a plane that includes the longitudinal axis of the wellhead system, it has been found that cracks may propagate from the vertex (the junction of the arms) of the V or U. In such circumstances, the connector extends both sides of the crack in the axial direction and strengthens the body of the wellhead system.

In addition to thread or other locking profiles, wellheads are known to have profiles for other purposes, such as locking and landing profiles for receiving and holding objects on the inside, for example for casing hangers and bore protectors. Those profiles may be positioned in an axial direction between the gripping portion and the locking portion and, in a similar manner, have fatigue induced cracks formed from / extending from the profile. In such circumstances the connector will also strengthen the wellhead system.

In an embodiment of any of the above embodiments, the connector comprises a housing, and the housing supports the locking element and the gripping element. -7 -

In an embodiment of any of the above embodiments, one of the locking element and the gripping element are loosely supported by the housing. In such embodiments the other of the locking element and gripping element is rigidly supported in the housing.

The loose support of one of the locking element and gripping element and rigid support of the other has the effect that the loosely supported element may move a lithe relative to the housing and the rigidly supported element.

In an embodiment of any of the above embodiments, the housing at least pa ly supports the compression element.

In an embodiment of any of the above embodiments, the housing comprises first and second housing elements, the first and second housing elements are loosely connected to each other, the first housing element supports the locking element, and the second housing element supports the gripping element. In such an embodiment the first and second housing elements may move relative to each other, at least to a certain degree, the locking element is rigidly connected to the first housing element, and the gripping element is rigidly connected to the second housing element.

In an embodiment of any of the above embodiments, the connector is configured to allow the compression element to cause relative movement between the locking element and the gripping element. This allows any slack in the connector to be removed and the compression element to develop tension within itself and to introduce compression into the portion of the wellhead system that extends between the position at which the locking element engages with the locking portion of the wellhead system, and the position at which the gripping element engages with the gripping portion of the wellhead system.

In an embodiment of any of the above embodiments, the connection between the housing and one or both of the locking element and the gripping element is such that when the connector is not in use, or when it is being put into position for use, the locking element and / or the gripping element are loosely held in position. -8 -

In an embodiment of any of the above embodiments, the housing is configured to transmit loads from the second component to the at least one gripping element at least when the compression element is introducing compression into the wellhead system between at least the locking portion and the gripping portion.

In some embodiments the housing is configured to transmit loads from the second component to the at least one gripping element without the compression element introducing compression into the wellhead system between at least the locking portion and the gripping portion, in such embodiments the housing is unitary and rigid in nature.

In an embodiment of any of the above embodiments, the housing is configured to transmit loads from the second component to the at least one gripping element only when the compression element is introducing or has introduced compression into the wellhead system between at least the locking portion and the gripping portion. In such embodiments the housing is riot rigid when the compression element is not introducing compression into the wellhead system between at least the locking portion and the gripping portion, for example the housing is comprised of first and second housing elements that are loosely connected, and the actuation of the compression element introduces rigidity into the housing.

The transmission of the loads from the second component is through the housing to the gripping portion of the wellhead system and lessens the effect that external loadings applied to or experienced by the second component, for example bending moments from tide or current interaction with a riser string extending from the second component to a surface vessel (for example a platform or ship), have on the wellhead system, in particular the potentially fatigued or damaged portion of the wellhead at or adjacent the upper end of the wellhead system.

In an embodiment of any of the above embodiments, the housing is so configured that the housing wholly, substantially, or at least partially surrounds the upper end of the wellhead system when the connector is connected to the upper end of the wellhead system. -9 -

In an embodiment of any of the above embodiments, the housing is configured as a frame.

In an embodiment of any of the above embodiments, the housing includes a frame.

In an embodiment of any of the above embodiments, the connector is configured to connect a substantially tubular upper end of the wellhead system to the second component. In some embodiments the upper end of the wellhead system is a cylindrical tube.

In an embodiment of any of the above embodiments, the connector has a length in the axial direction of 0.1 to 2 times the outer diameter of the wellhead system.

In an embodiment of any of the above embodiments, the locking element is configured to reversibly move between an unlocked configuration and a locked configuration. The locked configuration is such that the wellhead system and second component are connected to each other by the connector.

In an embodiment of any of the above embodiments, the locking element is configured to draw the wellhead system and second component towards each other when the locking element moves from the unlocked to the locked configuration. In such embodiments the locking element or at least part of the locking element is in tension when in the locked configuration.

In an embodiment of any of the above embodiments, the connector comprises a plurality of locking elements. In some embodiments, the plurality of locking elements are equally spaced around the outer parameter of the upper end of the wellhead system.

In an embodiment of any of the above embodiments, the gripping element is configured to reversibly move between a non-gripping configuration and a gripping configuration. A non-gripping configuration is one in which no part of the gripping element is in contact with the gripping zone of the wellhead system. A gripping configuration is one in which a part of the gripping element is in contact with the gripping zone of the wellhead system An advantage of the configuration of the gripping element being such that the gripping element can be in the non grippingconfiguration is that it allows the connector to be connected to the upper end of the wellhead system with the gripping element in the non-gripping configuration. As a result the gripping element does not, in this embodiment, have any effect on the making of the connection between the connector and the upper end of the wellhead system.

A further advantage of the configuration of the gripping element is that the movement of the gripper element into the gripping configuration allows transmission of forces from the connector to the gripping portion of the 'wellhead system without any initial relative movement between the connector and the wellhead system at the gripping portion of the wellhead system.

A further advantage of the configuration of the gripping element that installation and use may not be prevented if the wellhead system is bent or n other ways geometrically altered after installation.

In an embodiment of any of the above embodiments, when the gripping element is in the gripping configuration a preload is introduced into the gripping element. The introduction of the preload has the effect that loads transmitted from the second component, through the connector, and into the wellhead system at the gripping portion will need to overcome that preload before there is any possible movement of the gripping portion relative to the wellhead system.

The preload to be introduced may be calculated on the basis of the maximum anticipated load that will be transmitted through the connector and / or wellhead system. The maximum possible preload may be found from anticipating the preload capability of the preload mechanism. The maximum permissible preload may be found from anticipating the preload level that would damage the wellhead gripping portion. The use of the preload has the effect of minimising fatigue induced damage to the connector and / or the upper end of the wellhead system and arrest or limit further crack propagation. Similarly, it may prevent or reduce the risk of an accidental load or high load event causing damage to the wellhead system.

In an embodiment of any of the above embodiments, the gripping element comprises at least one gripper pad. The gripper pad is sometimes known as a die.

In an embodiment of any of the above embodiments, the gripper pad comprises a gripper face adapted to maximise the contact area with the wellhead system so as to maximise the force or load that can be applied between the gripper pad and the wellhead system. This maximises the resulting friction force between the gripper pad and the area on the wellhead system with which the gripper pad is in contact.

In an embodiment of any of the above embodiments, the gripping element is configured to engage with a mechanical interface formed in the wellhead system.

In some embodiments the mechanical interface comprises at least one indentation formed in the surface of the wellhead system, and the gripping element is so configured that part of the gripping element enters at least one indentation when the gripping element is in the gripping configuration.

In some embodiments the mechanical interface comprises at least one channel formed in the surface of the wellhead system and the gripping element is so configured that part of the gripping element enters at least one channel when the gripping element is in the gripping configuration.

In some embodiments the mechanical interface comprises a flange extending radially outwardly from the gripping zone of the wellhead system and the gripping element is so configured that part of the gripping element partially surrounds or otherwise engages with the flange when the gripping element is in the gripping configuration.

The mechanical interface may be introduced into the wellhead system before the wellhead system is deployed subsea or during the deployment of the wellhead system. Alternatively, the mechanical interface may be formed on the wellhead system in preparation for the connection of a connector according to the present disclosure to the wellhead system.

-12 -In an embodiment of any of the above embodiments, the wellhead system comprises the wellhead and the conductor pipe, and the gripping zone is positioned on the conductor pipe.

In an embodiment of any of the above embodiments, the connector comprises a plurality of gripping elements. In some embodiments the plurality of gripping elements are equally spaced around the outer parameter of the gripping portion of the wellhead system.

In an embodiment of any of the above embodiments, the compression element extends directly between the locking element and the gripping element. In such an embodiment the locking element and gripping element each include a locking element and gripping element body respectively. The compression element is engaged with the locking element and gripping element bodies.

In an embodiment of any of the above embodiments, the compression element extends indirectly between one or both of the locking element and the gripping elements. In such an embodiment the locking element and gripping element each include a locking element and gripping element body respectively, and one or more intermediate elements are connected between the compression element and one or both of the locking element and gripping element bodies.

In an embodiment of any of the above embodiments, the compression element extends directly between the housing and the locking element. In such an embodiment the locking element includes a locking element body. The compression element is engaged with the housing and the locking element body.

In an embodiment of any of the above embodiments, the compression element extends indirectly between one or both of the housing and the locking element. In such an embodiment the locking element includes a locking element body, and one or more intermediate elements are connected between the compression element and one or both of the housing and the locking element body.

In an altemative embodiment of any of the above embodiments, the compression element extends directly between the housing and the gripping element. In such an embodiment the gripping element includes a gripping element body. The compression element is engaged with the housing and the gripping element body.

In an embodiment of any of the above embodiments, the compression element extends indirectly between one or both of the housing and the gripping element. In such an embodiment the gripping element includes a gripping element body, and one or more intermediate elements are connected between the compression element and one or both of the housing and the gripping element body.

In an embodiment of any of the above embodiments, the connector comp plurality of compression elements.

In an embodiment of any of the above embodiments, the connector comprises an equal non-zero number of locking elements and gripping elements.

In an embodiment of any of the above embodiments, the connector comprises an equal non-zero number of locking elements, gripping elements, and compression elements.

In an embodiment of any of the above embodiments, the connector comprises an unequal non-zero number of locking elements and gripping elements.

In an embodiment of any of the above embodiments, the connector comprises an unequal non-zero number of locking elements and gripping elements, and a non-zero number of compression elements that is different from one or both of the numbers of locking elements and gripping elements.

In an embodiment of any of the above embodiments, the locking element is actuated by rotation of a screw thread. The rotation of the screw tread may be caused by a remote operating vehicle (ROV), electromechanical actuator, or other

rotation introduction means.

Actuation of the locking element is the causing of the lockingelement to move between the unlocked and locked configurations.

In an embodiment of any of the above embodiments the gripping element is actuated by rotation of a screw thread. The rotation of the screw tread may be caused by a remote operating vehicle (ROV), electromechanical actuator, or other rotation introduction means.

Actuation of thegripping element is the causing of that gripping tiler between the non-gripping and gripping configurations and, optional!y introdu preload into the gripping element.

In an embodiment of any of the above embodiments the compression element is actuated by rotation of a screw thread. The rotation of the screw tread may be caused by a remote operating vehicle (ROV), electromechanical actuator, or other rotation introduction means.

Actuation of the compression element causes the compression element to introduce compression into the portion of the wellhead system between the locking portion and the gripping portion.

In an embodiment of any of the above embodiments, the locking element is actuated by a hydraulic piston.

In an embodiment of any of the above embodiments, the locking element cornpr at least one actuator.

In some embodiments the actuator is hydraulically powered.

In some embodiments each actuator is a two way actuator. That is, the actuator can function to cause actuation in two opposite directions, for example to increase or decrease in length, or to rotate in one direction or to rotate in the opposite direction.

In some embodiments, the actuator comprises a hydraulic piston.

In some embodiments the actuator comprises lore hydraulic pistons.

In an embodiment of any of the above embodiments, the gripping eleme i actuated by a hydraulic piston.

In an embodiment of any of the above embodiments, the gripping element comprises at least one actuator.

In some embodiments the actuator s hydraulically powered.

In some embodiments each actuator s a two way actuator.

In some embodiments, he actuator comprises a hydraulic piston.

In some embodiments le actuator comprises two or more hydraulic pistons.

In an embodiment of any of the above embodiments, the compression element is actuated by a hydraulic piston.

In an embodiment of any of the above embodiments, the compression element comprises at least one actuator.

In some embodiments the actuator is hydraulically powered.

In some embodiments each actuator Jo way actuator.

In some embodiments, the actuator comprises a hydraulic piston.

In some embodiments the actuator comprises two or more hydraulic pistons.

In an embodiment of any of the above embodiments, the connector comprises a hydraulic system, and at least one hydraulic piston or actuator is actuated by the hydraulic system.

In an embodiment of any of the above embodiments, the hydraulic system includes one or more hydraulic power lines that are configured to be easy accessible to an ROV, and that may be cut by the ROV. In some embodiments the ROV can cut the one or more hydraulic power lines using a cutting tool. An advantage of this embodiment is that the ability to cut the one or more hydraulic power lines lessens the risk of not being able to release the connector from the wellhead system after the operations that required the connection of the second component have ended.

In an embodiment of any of the above embodiments, the hydraulic system comprises a controller and one or more sensors.

In an embodiment of any of the above embodiments, at least one sensor measures one of load experienced by one or more of the connector, the wellhead system, or the second component, or pressure within one or more of the wellhead system and second component.

The controller and sensors may be used to actively control one or more of the gripping element and compression element to seek to minimise loads and load variations on the wellhead system. The gripping element and compression element may be actively controlled to react loads acting on the second component so as to reduce variations in the loads experienced by the wellhead system.

The second component, for example subsea riser system equipment (such as a BOP or another valve arrangement adapted to be connected to the upper end of the subsea wellhead system) is connected (directly or indirectly) both to the wellhead system and a riser extending significantly (upright) in the water column. Typically, the bending moments horizontal shear force at the top of the subsea riser system equipment will be cyclic, meaning that the magnitude and direction of force will vary with time. This cyclic variation may have a static mean value other than zero. As a result, the upper part of the wellhead system will experience cyclic bending moments and perhaps a static mean bending moment.

To achieve active control of the loads; the control system may allow i cause continuous and active control (i.e. adjustment) of the compression element and thus the compression in the wellhead system between the locking portion and the gripping portion.

-17 -To achieve active control of the loads, the control system may allow / cause continuous and active control (i.e. adjustment) of the gripping element and thus the force with which the gripping element grips the gripping portion of the wellhead system. This is because the maximum load that can be transmitted via the gripper to the wellhead system is a function of the force which the gripping element applies to the gripping portion.

Additionally, one or more sensors may be provided so that the forces acting on the second component, e.g. cyclic and mean load, can be determined. The sensor(s) may sense loads andlor movements of the second component, and the gripping element and / or compression element may be adjusted in response. For example, the gripping element and / or compression element may be adjusted in response in an attempt to minimise variations in the loads experienced by the wellhead system. This is because load variations acting on a wellhead system can in fact be more detrimental to the integrity of the wellhead system than large static loads and hence an aim of the controller may be to reduce load variations on the wellhead system, which could for example lead to fatigue in the wellhead system.

Additionally, the sensor may be providing information on the gripping force and compression force level to a user, ensuring that forces are according to operational criteria. The sensors may also trigger an alarm to warn a user if those forces are below a predetermined criteria for safe operation, for example, an alarm may be triggered to warn a user if the compression in the wellhead assembly is no longer present to the extent needed for safe operations.

If the gripping element and / or compression element contain hydraulic actuators, it may be possible for a piston pressure reading to be used as a sensor. This is because the hydraulic piston may be subjected to the forces acting on the second component / wellhead system. This may be experienced as a tension or compression change that leads to a change in hydraulic oil pressure inside the piston cavity. If the piston area is Known and the hydraulic cavity pressure is measured it can be possible to determine either the applied tension or compression. Thus the gripping element and / or compression element may constitute a load sensing measurement device.

-18 -Additionally or alternatively other sensors may be used. Other sensors may include motion sensors. The motion sensors may for example be positioned on the lower end of the riser, above the lower flex joint and/or on the second component second component in a position below the lower flex joint. Other sensors that may be used include riser tension sensors; e.g. at the rig (surface vessel); load sensors in the second component frame, e.g. strain sensors, and/or strain gauges on the second component that, for example, can determine the applied load using Hooks law.

Data from the sensor(s) may be provided to the control system. The control system may be configured to use the data from the sensors to predict future loads soon to be transferred to the wellhead system via the gripping element and / or compression element. This computational function may be achieved using intermittent and high frequency calculation of a preprogrammed mathematical function that accurately predicts the expected load using the measured data as input. Additionally or alternatively, the computational function can be equipped with a self-learning routine (i.e. machine learning/artificial intelligence) that is able to improve its predictability of loads experience by the wellhead load relief system with time from accurately modelling the system response.

Once the predicted loads that will be experienced by the connector / wellhead system are determined, the control system can send a control signal to the gripping element and / or compression element so the forces generated by the gripping element and / or compression element can be adjusted in response.

The control system may adjust the gripping element and 1 or compression element to achieve a certain objective. This objective can comprise one or more or all of the following (but are not limited to): Minimizing the cyclic load experienced by the wellhead system; Minimizing the accidental load experienced by the wellhead system; Minimizing the second component movements, Obtaining and/or maintaining a predetermined mean flex joint angle.

Preventing a maximum flex joint angle; Releasing the gripping element and compression element during certain events: -19 -Preventina over tensioning / compression of the wellhead system and / or the connector; and/or Providing a predetermined second component stack angle relative to the vertical axis of the wellhead system.

As an example., how to minimise the cyclic load experienced at the wellhead system is explained: This may be achieved by the controller beina arranged to actively counteract applied bending moments to the second component using adjustment of the gripping element and / or compression element. This may be achieved using the same principle as noise cancellation systems as seen in everyday headphones or car audio systems.

As an example, if the riser above the second component (e.g. a BOP) moves to the right, this will generate a horizontal sideload that acts to urge the second component to the right, resulting in a reaction bending moment to be established almost instantaneously at the connection at the bottom end of the second component to the wellhead system. In this case a preioaded gripping element and/ or compression element to the left side of the second component will experience an increase in force, from the already established preload force. Using data from sensors the controller can predict when and at what magnitude this force change will be and can send signals that cause the forces within the gripping element and or compression element about the second component to be adjusted so that the applied force acts to counteract the incoming force change. The result is that the wellhead system is subjected to less force change compared to a system without active force control.

According to a second aspect of the present disclosure there is provided a system comprising a connector according to the first aspect, a wellhead system, and a second component, in which the wellhead system is connected to the second component by the connector, and ioading or external forces experienced by the second component is transferred to the wellhead system via the connector.

In an embodiment of any of the above embodiments, the wellhead system is the upper end of a subsea wellhead or the upper end of a subsea conductor pipe and the upper end of a subsea wellhead, and the second component is one of a subsea tree; a tree system spool, a blowout preventer, or a riser string.

According to a third aspect of the present disclosure there is provided a method of connecting a second component to a wellhead system in which the second component is connected to the 'wellhead system by a connector according to the first aspect, in which the method comprises connecting one or more locking elements to one of the wellhead system and second component, connecting the one or more locking elements to the other of the wellhead system and second component, engaging one or more gripping elements with a gripping portion of the wellhead system, and causing one or more compression elements to pull the one or more locking elements and e one or more gripping elements towards each other.

The apparatus of the first, and second aspects of the present disclosure can include one or more, or all, of the features described above, as appropriate. The method of the third aspect of the present disclosure can include one or more, or all, of the features described in association with the first and second aspects as appropriate.

The present disclosure will be further described and explained by way of example with reference to the accompanying drawings in which Figure 1 shows a schematic view of an embodiment of a system including an embodiment of a connector according to the present disclosure; Figure 2 shows a schematic sectional view of a part of the system of Figure 1 including a first embodiment of the connector according to the present disclosure; Figure 3 shows a schematic view of a detail of a first part of the first embodiment of the connector of Figure 2; Figure 4 shows a schematic sectional view of an alternative, third, embodiment of the gripper pad of the first embodiment of the connector of Figure 2; and Figure 5 shows a schematic sectional view of a part of the system of Figure 1 including a second embodiment of the connector according to the present disclosure.

-21 -In the following description the use of the terms upper, lower and similar terms in connection with an element are to be understood to be references to the vertical position of the part of the referenced element relative to the remainder of the referenced element when the referenced element is in use in normal conditions such as those illustrated in Figure 1. The term upwards is to be understood to be reference to a direction from a vertically lower to a vertically higher position. The term downwards is to be understood to be the opposite direction to that indicated by the term upwards.

In the following discussions of the accompanying drawings, where the same element is present in a more than one embodiment the same reference numeral is used for that element throughout, where there are similar elements similar reference numerals (the same numeral plus a multiple of 100) are used.

With reference to Figure 1, an offshore oil production system 2 includes a wellbore 4 within a surface casing 6. The surface casing 6 extends through a conductor pipe 8. The surface casing 6 and conductor pipe 8 extend into the earth from the seafloor 10.

Extending upwards out of the seafloor 10 the upper end of the surface casing 6 forms a subsea wellhead 12. The upper end of the conductor pipe 8 likewise extends upwards out of the seafloor. The subsea wellhead 12 and the upper end 14 of the conductor pipe 8 collectively form a wellhead system 16.

Connected to the wellhead system 16 via a valve system connector 18, hereafter termed "the connector 18", is a second component 20 in the form of a blowout preventer (BOP). The second component 20 is in fluid communication with a surface vessel 22 via a riser string 24. The surface vessel 22 partially extends upwards from the surface 26 of the sea 28. The surface vessel 22 may be a ship, drilling platform, or other appropriate structure.

In other non-illustrated embodiments the second component 20 may be one of a subsea tree, a tree system spool, a blowout preventer, a riser string, a kill spool, a tubing hanger spool, a capping stack, an in place capping stack, a kinetic blowout -22 -stopper (KBOS) standalone, a high pressure cap, a workover stack, or other element of well control apparatus.

Mounted on the second component 20 is a hydraulic system 56 which is connected to elements of the connector 18 by one or more hydraulic lines 58 (which are collective shown as a single line for clarity). The hydraulic system 56 includes a controller and may be remotely operable, or operated by an ROV. The hydraulic system may further include sensors and the controller may be used to actively control the hydraulic system 56 in the fashion described above.

With reference to Figures 2 and 3, the connector 18 is configured to connect the upper end 30 of the subsea wellhead 12 and the lower end 32 of the second component 20. The subsea wellhead 12 and second component 20 are co-axial with a central axis A. The upper end 30 of the subsea wellhead 12 and the lower end 32 of the second component 20 both have cylindrical cross-sections in the plane perpendicular to the central axis A. The upper end 30 of the subsea wellhead 12 includes a locking portion 34 which is configured as a helical screw thread on the radially outer face of the subsea wellhead 12.

The lower end 32 of the second component 20 includes a locking portion 52 which is configured as a shoulder extending around the radially outer face of the lower end of the second component 20.

The wellbore 4 and associated surface casing 6 and conductor pipe 8 have, in the present embodiment, been in place for an extended period of time and drilling and subsequent oil extraction operations have been performed through the wellbore 4. As a result of cyclic loading experienced by the subsea wellhead 12, and in particular the locking portion 34, a blind crack 36 may have developed in the wellhead 12 (see Figure 3). Positive identification or detection of such cracks may be very difficult in the subsea environment and, to be safe, an assumption that there is a crack may need to be made for safety reasons. If it is desired to perform subsequent operations on or to continue using the wellbore 4, then unless the wellhead 12 is to be replaced, the wellhead 12 needs to be strengthened to seek to avoid potential structural failure due to the assumed crack. Replacement of the wellhead 12 is a difficult, time consuming and expensive operation if that is possible at all.

The connector 18 of the present disclosure provides the required strengthening of the wellhead 12.

The connector 18 includes a plurality of locking elements 38, a plurality of gripping elements 40, and a plurality of compression elements 42. All of those elements are supported (directly or indirectly) in a housing 44. Not all of these elements are shown in schematic Figure 3.

The housing 44 is configured to surround the upper end 30 of the subsea wellhead 12 and the lower end 32 of the second component 20. The housing 44 is of a diameter larger than the outside diameter of the upper end 30 of the subsea wellhead 12 and the lower end 32 of the second component 20 with the result that the housing 44 does not interfere with the wellhead 12 and second component 20 during the connection of the upper end 30 of the subsea wellhead 12 and the lower end 32 of the second component 20.

The locking elements 38 are four in number and located in the housing 44 so as to be equally spaced around the upper end 30 of the subsea wellhead 12 and the lower end 32 of the second component 20 (only two are shown in Figures 2 and 3 because of the sectional nature of those Figures). The equal spacing has the result that each locking element is diametrically opposite another locking element. In other, non-illustrated embodiments of the present disclosure there may be more than four or between one and three locking elements.

Each locking element 38 is rigidly fixed in the housing 44 with the result that the locking element 38 as a whole cannot move relative to the housing 44.

Each locking element 38 is configured so that a first engagement part 48 of the locking element 38 adjacent the locking portion 34 of the wellhead 12 is configured to engage with the thread of locking portion 34, and a second engagement part 50 of the locking element 38 adjacent the locking portion 52 of the second component 20 is configured to engage with the shoulder of locking portion 52.

Each locking element 38 is also so configured that the locking element 38 may be reconfigured between an unlocked configuration and a locked configuration. In the unlocked configuration the first and second engagement parts 48, 50 of the locking element 38 are not engaged with locking portions 34, 52 of the subsea wellhead 12 and second component 20 respectively. In the locked configuration the first and second engagement parts 48, 50 of the locking element 38 are engaged with locking portions 34, 52 of the subsea wellhead 12 and second component 20 respectively.

Each locking element 38 is further configured that movement of each locking element 38 from the unlocked configuration to the locked configuration causes the upper end 30 of the subsea wellhead 12 and the lower end 32 of the second component 20 to be pulled towards each other.

A seal element 46 is located between the upper end 30 of the wellhead 12 and the lower end 32 of the second component 20 as illustrated in Figure 2 and the pulling of the upper end 30 of the subsea wellhead 12 and the lower end 32 of the second component 20 towards each other and into contact with seal element 46 makes a fluid tight seal.

Each locking element 38 is associated with an actuator 54 mounted between the locking element 38 and the housing 44. Actuation of the actuator 54 causes the reconfiguration of the locking element 38 between the unlocked and locked configurations.

Each actuator 54 is a hydraulically powered actuator and comprises at least one hydraulic piston (not shown) which is in fluid communication with the hydraulic system 56 via the hydraulic lines 58.

When there is only one hydraulic piston associated with a locking element 38, the hydraulic piston may be configured to be a two way piston. A two way piston can reconfigure the locking element 38 in both directions between the unlocked and locked configurations, that is from unlocked to locked and from locked to unlocked.

Alternatively, where there are two or more hydraulic pistons at least one hydraulic piston may be configured to reconfigure the locking element 38 from the unlocked to the locked configuration, and at least one hydraulic piston may be configured to reconfigure the locking element 38 from the locked to the unlocked configuration.

The gripping elements 40 are four in number and located in the housing 44 so as to be equally spaced around the subsea wellhead 12. In other, non-illustrated embodiments of the present disclosure there may be more than four or between one and three gripping elements.

Each gripping element 40 is loosely mounted within the housing 44 with the result that the compression elements 42 (discussed further below) can, on actuation, pull each gripping element 40 towards the locking elements 38 and the housing 44 does not resist any movement that follows from the actuation of the compression elements 42.

Each gripping element 40 includes a gripper pad 62. The gripper pad 62 of the gripping element 40 is located in a position adjacent a gripping portion 60 of the wellhead 12. The gripper pad 62 has a gripper face 64 which is configured to engage with the gripping portion 60.

With reference to Figure 4, a schematic sectional view of an alternative configuration of the gripping portion 260 of the wellhead 6 and an alternative gripper pad 262 is shown. The gripping portion 260 of the wellhead 6 includes a circumferential slot 272. The gripper face 264 includes a engagement member 274 which is configured to extend into the circumferential slot 272 when the gripper face 264 is in contact with the gripping portion 260. The circumferential slot 272 and engagement member 274 each include a bearing face 276, 278 respectively. The bearing faces 276, 278 extend in a direction approximately perpendicular to the axis A of the wellhead 12 and are located on the side of the circumferential slot 272 and engagement member 274 that is closest to the upper end 30 of the wellhead 12. An advantage of the configuration shown in Figure 4 is that the interaction of the bearing faces 276, 278 will assist in preventing gripper pads 262 sliding over the surface of the wellhead 12 when the compression elements 42 are actuated and the compression elements 42 are placed into tension.

With reference to Figures 2 and 3, each gripping element 40 is so configured that each gripping element 40 may be reconfigured between a non-gripping configuration and a gripping configuration. In the non-gripping configuration the gripper face 64 of each gripping element 40 is not in contact with gripping portion 60 of the subsea wellhead 12. In the gripping configuration the gripper face 64 of each gripping element 40 is engaged with a gripping portion 60 of the subsea wellhead 12.

Each gripping element 40 is associated with an actuator 70 mounted between the gripping element 40 and the housing 44. The actuator is so mounted that it will move with the gripping element 40 when the compression element 42 is actuated.

Actuation of the actuator 70 causes the reconfiguration of the gripping element 40 between the non-gripping and gripping configurations.

Each actuator 70 is a hydraulically powered actuator and comprises at least one hydraulic piston (not shown) which is in fluid communication with the hydraulic system 56 via the hydraulic lines 58.

When there is only one hydraulic piston associated with a gripping element 40, the hydraulic piston may be configured to be a two way piston. A two way piston can reconfigure the gripping element 40 in both directions between the non-gripping and gripping configurations.

Alternatively, where there are two or more hydraulic pistons at least one hydraulic piston may be configured to reconfigure the gripping element 40 from the non-gripping to the gripping configuration, and at least one hydraulic piston may be configured to reconfigure the gripping element 40 from the gripping to the non-gripping configuration.

The compression elements 42 are four in number and located in between the locking elements 38 and gripping elements 40. In other, non-illustrated embodiments of the present disclosure there may be more than four or between one and three compression elements.

Each compression element 42 includes an actuator 80 and a first and second engagement end 82, 84. The engagement end 82 is engaged with the locking element 38 via an engagement means suitable for use in tensioned connections. The engagement end 84 is engaged with the gripping element 40 via an engagement means suitable for use in tensioned connections. An example of an engagement means suitable for use in tensioned connections is a padeye attached to the locking element 38 or the gripping element 40 and a shackle engaged with the engagement end 82 or 84 respectively, the shackle is engaged with the padeye.

Actuation of the actuator 80 causes the actuator 80 to pull the locking element 38 and gripping element 40 towards each other. This induces tension in the compression element 42 and, as a result of the transmission of forces through the locking element 38 and gripping element 40 into the wellhead 12, compression in the portion of the well head 12 between the locking portion 34 and gripping portion 60.

Each actuator 80 is a hydraulically powered actuator and comprises at least one hydraulic piston (not shown) which is in fluid communication with the hydraulic system 56 via the hydraulic lines 58. The hydraulic piston may be a two way piston.

With reference to Figure 5, a second embodiment of a connector according to the present disclosure. The connector 118 is configured and functions in a similar way to the connector 18 described above in connection with Figures 2 to 6. The differences between the configuration of connector 18 and connection 118 are as follows: In the connector 118 the housing 144 is comprised of first and second sub-housings 114A, 1148. The locking element 38 is rigidly fixed to housing element 144A, and the gripping element 40 is rigidly fixed to the housing element 144B.

The compression elements 142 are four in number and located in between the first and second housing elements 144A and 144B. In other, non-illustrated -28 -embodiments of the present disclosure there may be more than four or between one and three compression elements.

Each compression element 142 includes an actuator 180 and a first and second engagement end 182, 184. The engagement end 182 is engaged with the first housing element 144A via an engagement means suitable for use in tensioned connections. The engagement end 184 is engaged with the second housing element 1446 via an engagement means suitable for use in tensioned connections. An example of an engagement means suitable for use in tensioned connections is a padeye attached to the first housing element 144A or the second housing element 144B and a shackle engaged with the engagement end 182 or 184 respectively, the shackle is engaged with the padeye.

Actuation of the actuator 180 causes the actuator 180 to pull the first and second housing elements 144A, 144B towards each other. This induces tension in the compression element 142 and, as a result of the transmission of forces through the locking element 38 and gripping element 40 into the wellhead 12, compression in the portion of the well head 12 between the locking portion 34 and gripping portion 60.

Each actuator 180 is a hydraulically powered actuator and comprises at least one hydraulic piston (not shown) which is in fluid communication with the hydraulic system 56 via the hydraulic lines 58. The hydraulic piston may be a two way piston.

The above description is meant to be exemplary only, and one skilled in the art will recognize that changes may be made to the embodiments described without departing from the scope of the disclosure. Still other modifications which fall within the scope of the present disclosure will be apparent to those skilled in the art, in light of a review of this disclosure.

Various aspects of the apparatus disclosed in the various embodiments may be used alone, in combination, or in a variety of arrangements not specifically discussed in the embodiments described above. This disclosure is therefore not limited in its application to the details and arrangement of components set forth in the foregoing description or illustrated in the drawings. For example, aspects -29 -described in one embodiment may be combined in any manner with aspects described in other embodiments. Although particular embodiments have been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from this invention in its broader aspects. The scope of the following claims should not be limited by the embodiments set forth in the examples, but should be given the broadest reasonable interpretation consistent with the description as a whole.

Claims

-30 -CLAIMS1 A connector for connecting a subsea wellhead system to a second component, in which the connector comprises a locking element configured to engage with a locking portion of the wellhead system and a locking portion of the second component, a gripping element configured to engage with a gripping portion of the wellhead system, and a compression element, in which the gripping element and the locking element of the connector are spaced from each other, and the compression element is configured to introduce compression into the 'wellhead system at least between the locking portion and the gripping portion.
2 A connector according to claim 1 in which the connector comprises a housing, and the housing supports the locking element and the gripping element.
3 A connector according to claim 2 in which one of the Jacking element and the gripping element are loosely supported by the housing.
4 A connector according to claim 2 in which the housing comprises first and second housing elements, the first and second housing elements are loosely connected to each other, the first housing element supports the locking element, and the second housing element supports the gripping element.

A connector according to any of claims 2 to 4 in which the housing is configured to transmit loads from the second component to the gripping element at least when the compression element is introducing compression into the wellhead system between the locking portion and the gripping portion.

A connector according to any of claims 1 to 5 in which the connector is configured to connect a substantially tubular upper end of the wellhead system to the second component.

-31 - 7 A connector according to any of claims 1 to 6 in which the locking element is configured to reversibly move between an unlocked configuration and a locked configuration.

8 A connector according to any of claims 1 to 7 in which the locking element is configured to draw the wellhead system and second component towards each other when the locking element moves from the unlocked to the locked configuration; and when the locking element is engaged with the locking portions of the wellhead system and second component.

9 A connector according to any of claims 1 to 8 in which the connector comprises a plurality of locking elements.

A connector according to any of claims 1 to 9 in which the gripping element is configured to reversibly move between a non-dripping configuration and a gripping configuration.

11 A connector according to any of claims 1 to 1C) in which the gripping element comprises at least one gripper pad.

12 A connector according to claim 11 in which the gripper pad comprises a gripper face adapted to contact the wellhead system, and the gripper face is configured to displace organic or inorganic material built up on the surface of the gripping portion of the wellhead system.

13 A connector according to any of claims 1 to 12 in which the gripping element is configured to engage with a mechanical intedace formed in the wellhead system.

14 A connector according to any of claims 1 to 13 in which the connector comprises a plurality of griping elements.

A connector according to any of claims 1 to 14 in which the compression element extends between the locking element and the gripping element.

-32 - 16 A connector according to any of claims 1 to 14 in which the compression element extends between the housing and one of the locking element and the gripping element.

17 A connector according to any of claims 1 to 16 in which the connector comprises a plurality of compression elements.

18 A connector according to any of claims 1 to 17 in which one or more of the locking element, gripping element, and compression element is actuated by one or more of rotation of a screw thread, and an electric actuation element 19 A connector according to any of claims 1 to 18 in which one or more of the locking element, gripping element, and compression element is actuated by a hydraulic piston.A connector according to claim 19 in which the connector comprises a hydraulic system, and each hydraulic piston is actuated by the hydraulic system.21 A connector according to claim 20 in which the hydraulic system comprises a controller and one or more sensors.22 A connector according to claim 21 in which at least one sensor measures one of load experienced by one or more of the connector, the wellhead system, or the second component, or the pressure within one or more of the wellhead system and second component.23 A system comprising a connector according to any of claims 1 to 22, a wellhead system, and a second component, in which the wellhead system is connected to the second component by the connector, and loading experienced by the second component is transferred to the wellhead system via the connector.24 A system according to claim 23 in which the wellhead system is the upper end of a subsea wellhead or the upper end of a subsea conductor pipe and the upper end of a subsea wellhead, and the second component is one of a subsea tree, a tree system spool, a blowout preventer, or a riser string.-33 -A method of connecting a second component to a wellhead system in which the second component is connected to the wellhead system by a connector according to any of claims 1 to 22, in which the method comprises connecting one or more locking elements to one of the wellhead system and second component, connecting the one or more locking elements to the other of the wellhead system and second component, engaging one or more gripping elements with a gripping portion of the wellhead system, and causing one or more compression elements to introduce compression into the wellhead system between the locking portion and the gripping portion.