The present invention relates to a subsea wellhead foundation and methods for installing a subsea wellhead foundation, for example for use with a petroleum well. BACKGROUND

Wellhead systems for subsea wells are traditionally known to comprise a wellhead having a wellhead housing secured to a well casing. It also generally has a valve stack, such as a blow out preventer (hereinafter referred to as BOP) or valve tree, located permanently or temporarily on the wellhead, for example during drilling, work-over operations and various phases of the operation. Such subsea wells can be used, for example, for petroleum exploration and/or for injection of fluids (such as water or C02) into a subterranean reservoir, as well as for extraction/production of hydrocarbons.

Installation of such subsea wellhead systems is typically carried out by an installation vessel, such as a ship or drilling rig. The process is demanding, with high requirements to installation accuracy while maintaining strict safety standards to avoid risk to personnel or equipment. For example, it is commonly a requirement that a foundation for supporting the subsea wellhead be installed substantially vertically, within strict limits for permitted deviation from the vertical (typically a few degrees). Vessels used for such offshore installation processes are typically highly specialized units which are costly to operate, and efficiency is thus also a key concern for operators.

Publications which may be useful to understand the field of technology include WO 2017/179992 A2, WO 2017/091084 A1 and WO 2021/091397 A1. There is a continuous need for improved technology for such wellhead foundations. The present disclosure has the objective to provide such improvements, or at least alternatives to known solutions and techniques. SUMMARY

It is an object of the present disclosure to mitigate, alleviate or eliminate one or more of the above-identified deficiencies and disadvantages in the prior art and solve at least the above mentioned problem. According to a first example there is provided a subsea foundation for installation on a sea floor, the subsea foundation comprising: a receptacle configured for receiving a wellhead housing, a conductor pipe extending from the receptacle and configured for receiving a well pipe therethrough, the conductor pipe comprising a first section being connected to the receptacle at one end thereof and being pivotably connected to a second section at a second end thereof, such that the connector pipe is configurable between a compact configuration in which the conductor pipe comprises a bend therein, and an extended configuration, in which the conductor pipe is substantially straight.

According to a second example, the subsea foundation may comprise a suction anchor base. According to a third example, the suction anchor base may be substantially cylindrical and the first section of the conductor pipe may be arranged concentrically inside the suction anchor base.

According to a fourth example, the first section of the conductor pipe may be fully located within the suction anchor base. According to a fifth example, the suction anchor base may be cylindrical and the second section of the conductor pipe may be shorter than the radius of the suction anchor base such that in the compact configuration, the second section of the conductor pipe may be located inside the suction anchor base.

According to a sixth example, the second section of the conductor pipe may be longer than the radius of the suction anchor base, and the suction anchor base may comprise a recess therein for locating the second section with the conductor pipe in the compact configuration.

According to a seventh example, in the extended configuration the conductor pipe protrudes outside the suction anchor base. According to an eighth example, the subsea foundation may comprise a hinge joint between the first and second sections of the conductor pipe, enabling the pivotal connection therebetween.

According to a ninth example, the hinge joint may comprise a disengaged configuration in which an end of the second section may be held distal to the second end of the first section and pivotal movement therebetween may be enabled, and an engaged configuration in which the second end of the first section may be engaged with an end of the second section and the conductor pipe may be in the extended configuration. BRIEF DESCRIPTION OF THE DRAWINGS

These and other characteristics will become clear from the following description of illustrative embodiments, given as non-restrictive examples, with reference to the attached drawings, in which

Fig. 1 is a schematic view of a subsea wellhead assembly. Figs 2a and 2b are cross-sectional views of a subsea well assembly.

Figs 3a and 3b are cross-sectional views of the subsea well assembly of Figs 2a and 2b, in a different configuration.

Fig. 4 illustrates the operation of a hinge joint.

Figs 5 and 6 illustrate configurations of a hinge joint in the subsea wellhead assembly.

DETAILED DESCRIPTION

The following description may use terms such as “horizontal”, “vertical”, “lateral”, “back and forth”, “up and down”, ’’upper”, “lower”, “inner”, “outer”, “forward”, “rear”, etc. These terms generally refer to the views and orientations as shown in the drawings and that are associated with a normal use of the invention. The terms are used for the reader’s convenience only and shall not be limiting.

Figure 1 shows a subsea foundation 1 for installation of the sea floor (not illustrated). The subsea foundation 1 may be described as a suction anchor foundation. The subsea foundation 1 of Figure 1 is illustrated in a configuration similar to that in which it may be installed. That is, the Figure 1 illustrates the subsea foundation 1 in an upright configuration.

The subsea foundation 1 comprises a receptacle 2, which may be used to receive a wellhead housing 3. The receptacle 2 is located on an upper component 10 of the subsea foundation 1 , which in this case is in the form of a circular plate or platform, and the receptacle 2 defines an aperture therethrough for the receipt of a wellhead housing 3. From the upper component 10 extends a lower component 12, which in this example is in the form of a hollow cylinder and together the upper and lower components 10, 12 define an anchor recess. The lower component 12 may be considered to be a suction anchor base. In addition, the upper component 10 may comprise a valve that may be used to operate the suction anchor, by permitting water to be removed from the anchor recess, and thereby anchoring the subsea foundation 1 on the seabed by means of suction. The upper component 10 may additionally comprise stiffening and/or reinforcement members, as is the case in Figure 1 , as well as connection points for various equipment.

In Figures 2a and 2b, the subsea foundation 1 is illustrated in cross-section. Figure 2a illustrates a perspective cross-section, while Figure 2b illustrates an elevation cross-sectional view. From Figures 2a and 2b, it can be seen that the lower component 12 is a hollow cylinder, and may therefore be considered to be in the form of a skirt.

As previously indicated, the receptacle 2 defines an aperture in the upper component 10, and may be located concentrically with the upper component 10 and/or the lower component 12. From the upper component 10, in a downwards direction, extends a conductor pipe 5, comprising a first section 5a and a second section 5b. The conductor pipe 5 may act as a guide for, for example, any pipes, casings, tubings or the like that extend from the wellhead e.g. into a well. The conductor pipe 5 extends within the lower component 12 (e.g. extends within the skirt) and may be either partially or fully located within anchor recess defined by the upper and lower components 10, 12, depending on the geometry of the conductor pipe 5 and the upper and lower components 10, 12.

As illustrated in Figures 2a and 2b, the first section 5a is connected (e.g. rigidly connected) to the receptacle 2 of the upper component 10 at one end thereof, and at a second end thereof comprises a pivotal connection to the second section 5b. To facilitate the connection between the first section 5a and the upper component 10, the lower component 12 may comprise a support member 16, such as a bracket or a tie, which connects the first section 5a to the lower component 12. The pivotal connection may be any connection that enables pivotal movement between the first and second sections 5a, 5b. In this example, the first and second sections 5a, 5b are connection by a hinge joint 14, which will be described in further detail in relation to the following figures.

In Figures 2a and 2b, the conductor pipe 5 is illustrated in a compact configuration, in which the conductor pipe 5 comprises a bend therein. While the first section 5a is connected (e.g. rigidly connected) to the upper component 10 such that relative movement therebetween is not expected, the pivotal connection enables relative movement of the second section 5b and both the first section 5a and the upper and lower components 10, 12. As such, the pivotal connection between the first section 5a and the second section 5b enables the conductor pipe 5 to be configured between the compact configuration as shown in Figures 2a and 2b, and an extended configuration as will be described in relation to the following Figures.

In this example, the second section 5b of the conductor pipe 5 is longer than the radius of the cylindrical lower component or skirt 12. As such, the movement of the second section 5b may be limited by the presence of the second section 5b, and in both compact and extended configurations, the conductor pipe 5 partially protrudes from the lower part 12. Although not illustrated in this example, the lower part 12 may comprise a recess for receiving the second section 5b of the conductor pipe 5, thereby enabling the conductor pipe 5, in the compact configuration, to be held at a level above the lower rim 18 of the second component 12. Additionally or alternatively, the conductor pipe 5 may comprise a third section which is pivotably connected to the second section 5b (e.g. via a further hinge joint similar or identical to the one described herein), and which may enable the conductor pipe 5 to be folded in a U- or J-shape inside the lower component 12, also enabling the conductor pipe 5 to be held at a level above the lower rim 18 of the lower component s.

In some other examples, the length of the second section 5b may be shorter than the radius of the second part 12 (or the width, in the case where the second part may be in the form of an extruded polygon, rather than a cylinder). In such cases, it may be possible to contain both the first and second sections 5a, 5b of the conductor pipe 5 completely inside the lower component 12. It should also be noted that the length of the first section 5a of the conductor pipe 5 is shorter than the length of the lower component 12, and as such in the compact configuration, the conductor pipe 5 is able to be completely contained within the lower component 12. In some other examples, the length of the first section 5a of the conductor pipe 5 may be longer than the length of the lower component 12, in which case in the compact configuration, there will remain a section of the conductor pipe 5 that protrudes from the lower component 12.

With the conductor pipe 5 in the compact configuration, the subsea foundation 1 may be more easily transported that would otherwise be possible. For example, in cases where the conductor pipe 5 is able to be completely contained within the anchor recess, and/or is able to be held completely above the lower rim 18 of the second component 12, the subsea foundation 1 may be able to be transported in the upright orientation (e.g. the orientation as shows in Figure 1). The subsea foundation 1 may, for example, be positioned on the deck of a transport vessel upright, and with subsea foundation 1 resting via the rim 18 on the deck. In cases, such as that illustrated in Figures 2a and 2b and in cases where the lower component 12 comprises a recess, where the second section 5b is longer than the radius of the lower component 12, the laterally protruding section of the second section 5b may be rested e.g. on the deck of a vessel, or may be rested on or in a support structure on a vessel, during transport. As such, the second section 5b may be positionable during transport so as to provide the subsea foundation 5 a stable base 5 during transport, and additional support may be provided to the second section 5b where required, thereby assisting to stabilise the entire subsea foundation 1 .Such a support system may not be found in other examples of subsea foundations 1 .

In cases where the first section 5a is longer than the length of the lower component 12, or in cases where movement of the second section 5b is limited by the lower component 12, thereby requiring at least a part of the conductor pipe 5 to protrude from the anchor recess, the subsea foundation 1 may still be transported in the upright position, but on a raised platform, for example. Such means of transport may be preferable to, for example, having to transport the subsea foundation on its side, which would then require adequate anchoring of the subsea foundation 1 to a vessel during transport, and subsequent reorientation of the subsea foundation 1 from a horizontal to a vertical position before installation.

Figures 3a and 3b illustrate the subsea foundation 1 of Figures 2a and 2b, respectively, with the conductor pipe 5 in the extended configuration. As can be seen, in the extended configuration, the conductor pipe 5 is straight, and the first and second sections 5a, 5b are axially aligned. In the extended configuration, the conductor pipe 5 protrudes from the lower component 12, e.g. protrudes below the lower rim 18 of the lower component. The subsea foundation 1 may be installed in the expanded configuration, and may be configured to the expanded configuration prior to installation, and after being suspended from a vessel, for example by a crane. Movement of the second section 5b to the expanded configuration may be at least partially possible under its own weight.

In Figures 4 to 6, further detail of the hinge joint 14 is illustrated. As previously described, the hinge joint 14 is located at the interface between the first section 5a and the second section 5b. Figure 4 illustrates the steps involved in configuring the connector pipe 5 from the compact configuration to the expanded configuration.

In Figure 4, the conductor pipe 5 is show in the left-hand figure in the compact configuration, and in this case the first section 5a is axially offset approximately 90 degrees from the second section 5b. In the central figure of Figure 4, the first and second sections 5a, 5b of the conductor pipe 5 have been moved to the extended configuration, such that the first and second sections 5a, 5b are axially aligned and the conductor pipe 5 is now straight. In Figure 4, a hinge pin mechanism 20 can also be seen. With the hinge pin mechanism 20 holding the hinge joint 14 in a disengaged configuration, as is the case in the left-hand and central figures of Figure 4, the end of the first section 5a is held distal to the end of the second section 5b, and movement of the second section 5b relative to the first section 5a is possible. In the right-hand figure of Figure 4, which also shows the conductor pipe 5 in the extended configuration, the hinge pin mechanism 20 may be moved (in this example moved in an upwards direction towards the first section 5a to the position illustrated by arrow A) to reconfigure the hinge joint 14 to the engaged configuration. In the engaged configuration, the hinge joint 14 may hold the end of the second section 5b proximate to the second section 5a, and in some examples, the end of the first section 5a may engage or abut the end of the second section 5b. The hinge pin mechanism 20 may be located on, or defined by, the second section 5b, and therefore movement of the hinge pin 20 towards the first part 5a may also have the effect of moving the second section 5b in the direction of the first section 5a, as illustrated by arrow B in Figure 4. In the engaged configuration, movement of the second section 5b relative to the first section 5a may no longer be possible. Once the conductor pipe 5 is in the expanded configuration and the hinge joint 5 is in the engaged configuration, the subsea foundation 1 may be ready to be installed in a subsea location. Having the conductor pipe 5 protruding from the lower component 12 may assist to ensure an accurate and efficient installation of the subsea formation 1 in a desired position, and may assist to prevent washout during installation and subsequent drilling operations. For example, having a longer conductor pipe 5 may permit the conductor pipe to reach a greater depth in a seabed, ocean floor, lakebed, or the like, where the earth may be harder and less prone to erosion, thereby preventing washout.

Further detail of the hinge joint 14 and the geometry of the first and second parts 5a, 5b are shown in Figures 5 and 6. With the conductor pipe 5 in the compact configuration, as in Figure 5, the hinge pin mechanism 20 can be seen to be in a lower position, and the ends of the first and second sections 5a, 5b are held distal to one another. With the hinge pin mechanism 20 in this position, movement of the second part 5b relative to the first part is possible without the end of the second part 5b coming into contact with the first part 5a.

In the illustration of Figure 6, the hinge pin mechanism 20 is in an upper position. Here, it can be seen that the end of the first section 5a has been brought proximate to the end of the second section 5b, such that the ends of the first and second sections 5a, 5b are in contact. Bringing the second section 5b into contact with the first section 5a may be achieved by using a lifting wire, or by compression of the second section 5b towards the first section 5a through use of the seabed. Although not illustrated, the hinge joint 14 may comprise a seal or sealing arrangement to facilitate fluid flow through the hinge joint without leakage thereof. By holding the first and second sections 5a, 5b in contact, relative movement of the sections 5a, 5b is now restricted, or possibly completely prevented. With the hinge pin mechanism 20 in this position, the first section 5a may be considered to be locked in position relative to the second position. Having such a subsea foundation 1 , with a conductor pipe 5 comprising a first and second section 5a, 5b, the section 5b being pivotably connected to the first section 5a may allow a conductor pipe that is longer, and with a greater possible diameter than other solutions. For example, the diameter of the conductor pipe 5 may be able to be wider than in cases where the conductor pipe is telescopic, thereby requiring a smaller diameter with each telescopic section. Further, having a pivotal connection may be a simpler solution that is less prone to problems (e.g. sticking or excessive wear) than known solutions which may comprise many and/or complex moving parts. The invention is not limited by the embodiments described above; reference should be had to the appended claims.