GB2549458A

GB2549458A - Subsea foundation

Info

Publication number: GB2549458A
Application number: GB1606129.3A
Authority: GB
Inventors: Eide Asle; Inge Yetginer-Tjelta Tor; Johannes Strøm Pål
Original assignee: Statoil Petroleum ASA
Current assignee: Equinor Energy AS
Priority date: 2016-04-11
Filing date: 2016-04-11
Publication date: 2017-10-25
Also published as: WO2017179992A1

Abstract

A method of installing a subsea foundation 1 is provided. The method comprises providing a suction anchor 2 having an inner member 6, which may be a pipe for a well, and an outer suction skirt 4 located around the inner member. The inner member protrudes from the outer suction skirt. The suction anchor is moved towards a seabed so that the inner member penetrates the seabed before the outer suction skirt. The suction anchor is then further moved towards the seabed until the outer suction skirt reaches the seabed, before the suction anchor is sucked into the sea bed. A subsea foundation (100, Fig 8) that comprises a plurality of suction anchors, at least one of which provides a foundation for a subsea device, is also disclosed.

Description

SUBSEA FOUNDATiON

The invention relates to a subsea foundation which comprises a suction anchor and a method for installing the subsea foundation. liany subsea devices, such as a well and wellhead eduipment, require a foundatlbn on which they can be located dufin| use, For exarnple, a subsea wei! assembly will generally comprise a foundation. The foundation is used to support the subsea well which extends into the seabed and the wellhead equipment such as a blowout preventer. A known type of subsea foundation is the suction anchor, A suction anchor used as a subsea foundation comprises a skirt. The suctjdn anchor is lowered onto the seabed and then sucked into the seabed by reducing the pressure inside the skirt. Once the suction anGhor has been sucked into the sea bed, a well may extend through ihessuction anchor into the sea bed Of the suction anchof may provide a foundaiion for another subsea device,

It has been found that with a suction anchor foundation, the foundation may not always be at the correct orientation, e.g. the top surface may not be horizontal (relative to the seabed), Problems have also been known tb arise with the seabed under the suction anchor being eroded/washid ^vvay, particularly when tie foundation is used for a well. This may be known as washout.

There is therefore a desire for an alternative and/or improved subsea flbundation which comprises a suction arschar.

In a first aspect the present invention provides a subSea foundation, the foundation comprising; a suction anchor, the sui^ion anchor comprising an inner member and ah outer suction skirt located arDund/about the inner member, wherein the inner member protrudes from the outer suction skitl;.

The subsea foundation may be a subsea well foundation.

The inner member may be a pipe for a weH.

The weli as referred to in the present spieeification may be an oil and/or gas well.

Thus, the present invention may provide, a subsea well foundation, the feundation comprising: a suction anchor, the suction anchor comprising an inner pipe for a vyoli and an outer suction skirtlocated around/about the Inner pipe, wherein the inner pipe protrudes from the outer suction skirt. in a second aspect, the present Invention provides a method of installing a subsea foundation, the method comprising: providing a suction anchor, the suction aiielior comprising an innerWiimber and an outer suction skirt located around the inner rnember, wherein the inner member protrudes from the outer suction skirt; moving the suction anchor towards a seabed so the inner member penetrates the seabed before the outer suction skirt; further moving the suction anchor towards th# seabed until the outer suction skirt reaches the seabed; and sucking the suction anchor into the sea bed.

The subsea fOundaiion may be a subsea well foundation.

The inner member may le a pipe for a well.

Thus, the present invention may provide a method of installing a subsea well: foundation, the method comprising; providing a suction anchor, the suction anchor comprising an Inner pipe for a weii and an outer suction skirt located around the inner pipe, wherein the inner pipe protrudes from the outer suction skirt; moving the suction anchor towards a seabed so tie inner pipe penetrates the seabed before the outer suction skirti further moving the suction anchor towards the seebed until the outer suction skirt reaches the seabed; and sucking the suction anchor into th| sea bed.

The method may comprise providing the suction anchor/subsea fiauridatipn of the first aspect. The foiiowing opiiohal features and discussipn may apply to both the first and/or second aspecl of the inveriboh;

It has been found that by having a suction anchor wherein the inner member protrudes from the outer suctiGn skii, when theiauinidation Is being installed the inner member may reach and penetifote the seabed before the outer suction skirt reaches the seabed. This means fhat fie inner member may provide guidance (eig. vertical guidance) for the subsea foundation as the suction anchor is sucked into the sea bed. For example, the orientation of the foundation may be acyusted to a desired orientation and then the inner memier may be used to help maintairii the foundation in that orientation until the outer suction skirt reaches the s|abed and/or whilst the suction anchor is sucked iritOthe sea bed.

The orientation^erticality of the SUCtipn anchor may be checked and/or adjusted before the outer suction skid starts to penetrate the seabed. This means that it is possible to reliably provide a foundation which is at a desired Orientation relative to the sea bed, such as horizontal, substantially horizontal, or horizontal Within an acceptable limits In fvis ease, the inner member fwlich may be a pipe for a well) may be vertical, substaritiaiiy vertical or vertical wfthin an acceptable limit, such as up to 1, 1.2, 1.δ Or p from vertical to be formed.

The ihher rtieniber rnay be perpendicuiar to the top sdiface bf the suqtipn anchor which may in use provlele a support surface for a subsea device.

The suction anchpr may proyide a foundation for a subsea device. The subsea device may be a subsea \^|i and opibnally the associated weiihead equipment. The subsea device may for example be any known subsea device such as a pump station, a separator, a compressor^ a manifold, a eontro! centre, a smart manifold, a control hub, power/hydraulie pp^p uhit^ power equipment; fas compressor module and/dr cooler.

The inner member may be a solid body SUcf» as a rod.

The inner member may be an elongate |i.e· its lengii miiy be significahtly more than the width) meniber.

The inner member may be a hollow body such as a pipe, it may be advantageous for the inner member to be a hotlow body as this may allow the inner member to have less resistance to penetrating the seabed.

The inner member may have a cross section which is substantially constant along its length. Alternatively, the inner member may have a cross section which is not constant along the length. For example, the inner member may have a smaller Grpss-sectional area at or towards the bottom (i.e. the end that wiit penetrate the seibed first) compared to that at or towards the top of the inner member.

The inner member may have a circular cross section or the inner member may have a non-circular cross-section.

When the inner member is a pipe (i.e. a hollow body), it may have an inner diameter which is not constant along its length. For example, the inner diameter may decrease towards the bottom of the inner member. The inner member may have an inner diameter 'which Is larger at or towards the top of the suction anchor eompared to the bottom of the suction anchor. Alternatively the inner diameter may decrease and increase along its iength.

Additionally, if the Inner member is hollow, such as a pipe, it may bf possible tb apply suction to the infer rnember so that a suction force can be created. The method may comprise rf ducing the pressure inside the inner member. This may be before or after the outer suction skirt has reached the seabed. This may reduce penetration resistance on the inner member (due to the effect it has on the mateflaf on the seabed) and/or may give additionai force to cause penetration of the inner member. Thus, suction may be applied to the inside of the inner member so as to stiOfc tho suction anchoci at least In part, into the sea bed.

The suction anchor rnay include one or more interna! stiffeners which connect the inner member to the outer suction skirt. In the case of a plurality of stiffeners these may be spaced cireurnferentialiy, Such as |y eciua! angles, afound the inner member.

The stiffener(s) may be plates which extend in a plane parallel to the axis of the suction anchor. This is so the resistahCe of the stiffener(s) to penetration of the suction anchor into the seabed is rhihimisei.

The stiiener(s) Or at: least a portion of the stifferior(s) may be located at or towards the bottom Of the suction skirt.

The stiffener(s) may be used tp ensure that Ihe ofientation of the outer suction skirt is fixed relative to the Orieritation of the Iriner member.

Vertical may be tbe direction which is parallel to the direction of gravity.

Vertical may be the direction which is perpendiOulaF to the plane of the sea bed.

By “the Inner member protrudes from the outer suGiiOn skirt” it may be meant that the inner member extends beyond the bottom of the outer suction skirt. The bottom may be the portion of the suction anchor which penetrates the seabed first during installation. The inner member may protrude from the top of the suction anchor in addition to protruding from the bottom of the suction anchor. fhe top of the Suction anchor may be the pari, when the suction anchor is in use/instaiiel on the seabed, closest to the surface of the water. The top of the suction anchor^ or a component such as a steel beam platform on the top of the Suction anchor, may be the part which supports the subsea device. it may only be a portion of the inner member, e.g. a bottom portion of the inner member, which protrudes from the outer suctibn skirt.

The inner member may provide ah opening or channel through the suction anchor through which a well can be formed.

Trie inner member may be longer than the outer suction skirt.

The length of the inner member that protrudes from the outer suction skirt may be f to 5, or 1 to 5 times the diameter of the outer skirt.

The total length of the inner member (i,e. the length of both the protruding pprtibn and the portion within the length of the skirt) may be 1.1 to 1Θ times the diameter of the outer skirt. ffee sutef suetfon skirt t|ay have a diameter that is f t© 8 meters.

The outer suetioh skirt hej|ht/iength may be 1 to I times the diameter of the outer suction skirt

The inner member may have a diameter whieh is between ii and 60 inches. For example, when the inner member i| a pioo for a well, the inner diameter of the inner member may be 26 to 42 inches.

The inner member may be a pipe with an inner diameter which is 50 to 60 irtches. The ihrier nnember may have an inner diameter which is 50 to 60 inches for example when the inner member is for a wrell.

The inner member may be a pipe with an inner diameter which is 20 to 60.

The length of the inner member and/or outer skint may depend on the geology of the instaliatioh Site.

For exarnplev the length of the inner member may be the same as the depth at which harder soi! is ioeated in the Sea bed. This, for example in the case that the suction anchor is for a wei!, is to ensure that the inner member extends through the softer surface material so as to try to prevent washout during drilling.

The geology of the installation site may be determined before instailation by ia site survey and/or soil sampling,

The length of the portion of the Inner member which protrudes from the outer suction skirt may depend on the geology of the instaliation site. This is because the iengih may be chosen to ensure that the at least a portion of the suction skirt will pehetrate the sea bed under the weight of the suction anchor before frieibh prevents the fuction anchor penetrating any further urider action of its own weight. Thus the method may comprise selecting a length of the inner member based Oh the geology of the instailation site.

The lerigth is the dimension in the axial direction (i.e. the direction w-hoh in use rhay be approximately verticai).

The inner member may be coaxial with the outer suction skirt. The outir suction skirt may be located about the inner member. The outer suction skirt and the inner member may be concentric,

The volume between the inner member and the outer suction skirt rtia| be the volume in which the pressure is reduced to allow the suction anchor to be sucked into the Sea bed.

The inner member may be connected to the outer suction slcirt in a pressure tight manner. This is so that the pressure in tie voiume between the outer suction skirt and tie inner member can be controlled.

The suctian anehor may comprise a deyiee, such as a pump, for reducing pressure inside the voiume (for providing the sycUon fierce).

When the inner member is a hoiiow body, the suction anchor may comprise a device, such as a purnp, for reducing pressure inside the inner member.

The iiner member and outer suction skirt may be attached/connected to each other. This connection may be a rigid and/or structurai connection.

The connection bo%een the inner member and outer suction skirt may be such that the reiative orientations of the inner member and outer suction skirt are fixed reiative to each other. This means that il the inner member is maintained in a certain orientation reiative to the seabed the outer suction skirt may also be maintained in a fixed orientation reiative to the seabed. This may allow the orientaiion of the outer suction skirt relative to the seabed to be controlied/fixed during instafiation using the inner member.

For example, the outer suction skirt and the inner member may be connected by a connection portion. The outer slirl, inner member and connection portion may together form the volume in which the pressure is reduced to allow the suction anchor to be sucked into the ground. The volume may be an annular volume around the outside of the inner member.

The Connection portion may be an annular plate. The connection portion may extend between the top of the inner member and the top of the outer suction skirt

In use a well may extend through the inner member. in the case that the inner rriember is an inner pipe for a weli, the inner member may replace the function pf a conductor pipe. Therefore, a subsea well wNch comprises the subsea (well) fpundation may not comprise a conductor. Instead the inner member may act as a conductor. fhe inner member may be iritefrai with the outer suction skirt. For example, the inner member arid the outer suction Skirt may be a single pieGe, Thisisingie piece may have been formed ly welding components together.

Alternatively, the inner member, or at least part of the inner member, may be a separate piece of the subsea foundation.

The inner fiemler may comprise an upper inner member portion and a IPW/er inner member ppiipn. When the inner member is a pipe, the upper inner member portion and the lower inner member portion may eabh be pipe portions. These two portions may be separate member portions. In use, the two ihriir member portions may be rigidly connected to each other. This is so that the lower inner member portion may be rigidly fixed relative to the outer suctions sRirt.

These two separate member portions may be joined together when the components are subsea. This may be before the outer sucrtion skirt penetrates the seabed. It may be the lower inner member portion which protrudes from the outer suction skirt.

The connection between the lower ihrter member portion and the upper inner member portion may be ai/aboutthe bbiOm Of the skirt (i e. at or near the skirt opening). The connection between the tower inner member portion andlhe upper inner mernber portion may be within the length of the outer suction skirt. the method may comprise attaehinp at least the portion of the inner member which protrudes from the outer su^iOn skirt at the instailation site. This may be subsea.

The upper inner member may be referred to as a centre member and/or the lower inner member portion may be referred to as an extender. The inner member may be referred to as a guide member or guide pipe or as a centraliser. This is because the inner member may be used to guide the outer suction Skirt so that it can be sucked into the sea bed in a desired orientation.

The inner member may be for guiding the suction anchor into the sea bed in a eertairi orientation.

The suction anchor may comprise an upper Inner member portion which does not protrude from the bottom of the outer suction skirt. For example, the upper inner member portion may be the same length or shorter than the iength of the outer suction skirt portion. The upper ihner member portion may be integral with the outer suction skirt. The upper inner member portion may be directty connected to the outer suction skirt by t|esoonneciion portion.

The upper end Of the inner member (©·9· upper end of the upper inner member portion) may be attached to the outer suetion skirt at or near the top Of the outer suction skirt.

The suction anchor may be arranged so thet the inner member, or at least a portion of the Inner rnember, such as the lower ih|er member portion, can be attached (directly or ihdirectty, sue! as via a connectidh portion Or apother portion of the inner member such as the upper inner member portion) to the outer suction skirt when the suction anchor is subsea.

The len|th of the lower inner member portion, and hence the length it pfclrudes frorn the outer skirt, may be chosen based on the geology of the installation site. This is to ensure that the suction anchor will penetrate the sea bed suffieieriiy under its own weight to allow the suction anchor to be sucked in bf the final action of reducing the pressure inside the suiion anchor.

The suction anchor and upper inner mernber portion (if present) may be the same length irrespecilve of the installation site ilology (or it may be the same for many different geologie# but the length of the lower inner member portion ma|r be selected accordingly.

The step of providing the suction anchor may comprise providing the inner member, or a portion of the inner member such as the lower inner member portion. The method rnay dofnprise the step Of locating the inner member, or a portion of the inner member Such as the lower inner member portion^ subsea. For example, the inner member, or a portion Ofthe inner member such as the lower inner member portion may be located on the sea bed. The mifhod may comprise providing the outer suction skirt. The method may comprise deploying the outer suctien skirt subsea. This may be after the portion of the inner member, or the inner member has been deployed subsea. the method may comprise attaching and/or securing the inner member, or a portion of the inner member such as the lower inner mernber portion, to the outer suotion skirt when both components are subsea.

The rtiethod may comprise directing a guide, such as a wire, through the sucion ahchoh anp connecting the inner member, or a portion of the inner member such as the lower inner member portion to the guide. The guide may be used to support the inner mernber (or portion of the inner membet^ arid guide Unto attachment with the i^st of the suction anchor.

The inner mernber, or a portion of the inner member such as the lower inner member portion, may then be lifted and attached to the suction anchor (such as to the connection portion which connects the inner rnember to the outer suction skirt or to the upper inner member portion)^ ©nee the inner member, or a portion of the inner mpmber such as the iower inner member portion, is connected to me suction aneilorj tHe suction anchor may then be lowered towards the Seabed for the rest of the instatlation method to be performed.

The inner member may be a telescoping member, in this case, the length # the inner member may be adjusted between a contraelted length and an extended length.

The method of attaching ahd/dr securing the inner member, or a portion of the inner member such as the lower ihnfr member portion, to the outer suction skirt may comprise inserting the inner member, Or a portion of the inner memier into me outer skirt from the top of the suction anOhOh This may be achieved by hammering the inner msmberi or portion ol the inner memier, in from the top.

When the arrangement com^ises an uppr inrier member portion and a lower inner member portion, the iowef iriner member podiOn may be Inserted into the top of the upper inner member portion and pushed through until the lower inrjer member podien protrudes from the bottom of the outer sucion skirt.

When the method comprises attaching and/or securing a portion of the inner member, such as the lower inner member portion, to the outer suction skirt, the outer suction skirt may already be connected to another portion of the inher member such as the upper inner mernber ROrtion. This eonnection between an upper inner member portion and the ditef suctipn skirt rriay have been made onshore before the suction skirt was taken to the installation location.

The upper inner member portion, if present, may not piOtrude frerrt the suction Skirt.

Thus, the outer suction skirt may be transported to the location where the subsea foundation is to be installed Without having a member protruding ftom lie outer sisrt. This can make transportation easier and irtihimiSe the risk that the suction anchor, or part of the SMRffen anchor, is damaged durtng tiansportation.

Irrespective of Whether the inner member, or a portton of the inher member, is attaGhed to the outer suction skirt subsea or Whether the suotioh anchor with the protruding inner member is ready formed before being deployed subsea, the inner member which protrudes from the outer suction skirt may be attached to the Outer suction skirt before the suction anchor starts to penetrate the sea bed. Thus, the inner member a part of which protrudes from the boiom of the outer suction skirt may be installed in the sea bed simultaneously with the outer suction skirt.

The suction anchor may be supported during installation. The suetion anchor may be supported by deployment apparatus. The deployment apparatus may eofTiprise wires, winches, buoys, chains and dummy weights for example. The suction anchor may be lowered towards the eea bed. This may be under action of its own wei|hi.

The method may comprise lowering the suction anchor towards the sea bed until the lower most portion of theinner member is just above the sea bed. The method may then comprise holding the suction anchor for a period of time so that it can level under its own wei|ht. This may be effective if the suction anchor will hang straight

The level/orientation of the suction anchor or subsea foundation may be its angle relative to the sea bed.

Additioriatly or alternatively, the method; may comprise checking the position of the suction anchor: if the suction anchor is not level, the method may comprise levelling the suction ahchor. Levelling the suction anchor may comprise adjuStihg the position of the suction anchor, Leyelliig; may be;;achieved by pitch and/or roll adjustments. This may be achieved by aii;usting the support (e.g. deployment apparatus) holding the suction anchor fsuGh as wires and winches). For example the winch, suGh as a lift winch, holding one side may be adjusted to ehange the angle of the suction anGhor relative to the sea floor.

The foundation may comprise a sensor, Such is an inclinometer, for deiermining/checking the orientation of the foundation.

The ori|ntatipn of the foundation may be checked continuousiy during instaiiation. This case, an adjustment may be made as soon as the orientation is not, or a certain angle (e.g. above a threshold angle) from, the desired orientatipn.

Atternativeiy, the orientation of the foundatiQn may be checked periodiceily during installation. This may for example be befem the inner member Contacts the seabed, when only the inner member contacts the seabed and/or when the Outer suction skirt is in contact with the sea bed but before suction of the skirt into fhe sea bed begins.

Levelling hie suction anchor may comprise using weight(s) (such as ballast or materia! taken from the sea bed). The weight(s) may be put On the suction anchor and may be moved to shift the centre of gravity in order id permit the control Of the orientation of the suction anchor relative to the sea bedL

Leveliing the suction artchor, such as adjusting the position of y#ights on the foundation, may be automatic and/or manual based on the sensed orientation of the foundation during inftaliation.

Tie weight(s) may be mo^aiie, such as by hydraulic jacks.

The weight(s) may be recks, (such as sacks Of rocks} which are for example taken from the seabed or are preTilfed gravel bags deployed from a vessel.

The weights may be movable in at least two directions, such as t^o perpehdicular directions. This is so that the roil and pitch, or the orientation in two axis, of the foundation maf be controlied by moving the wei|htSi The weight(s) may be retrievable and/or reusable.

The method may compriseschanging the position of the weight(s) until the foundatiOh is at the desired angle relative to the sea bed.

The method may comprise ensuring that the inner mernber is veiticai when it Starts to penetrate the sea bed.

The present invention may be used to eontrol ihe final orientationihclination of the foundaiion after installation.

In some scenarios, such in the case pf a vv#wlth a small overburden, it may be desirable to have a foundation which is not vertical. This Is because, in the case of a well with a small overburden, the direction of the well ma| need to change over a very short disiance (iue to the small overburden) and thus it may be desirable to have a foundation which is at an anile from iorizontai. e g. greater than % §, W, 15, 25 or 45 degrees from horizontai such that Ifre pipe Ipr the well may be gpaterthan 2, 5, 10, 15, 25 or 45 degrees from Veilcak

The bottom surface of the inner merhler and/or outer suctiOh skirts may be angledihclined relative to the main axis andljr top surface of the suction anchor. This may be useful if the suction anchor is intended to be located in the sea bed extendihg at an angie/incline relative to the plane of the sea floor.

If the bottom surface of the suction anchor (i.e. inner member and/or suction skift) is angled when the suction anchor is lowered towards the sea floor under the acidh of its own weight, when it reaches the sea ^oor I will naturally extend at an angle from the direction perpendicular to the sea floor. As a result, as the suction anchor penetrates and/or is suoked into the seafloor it may be in an orientaflon which is at ah angle from the direeiOn perpendicular to the sea floor.

This aspect of the invention may be independently patentable from the other feafures of the invention, i.e. the suction anchor does not necessarily n|ed to lave an inner member which protrudes from the suction anchor.

The step of moving the suction anchor towards a sea bed SO the inner member penetrates the seabed before the outer suction skirt, may involve lowering the suction anchor i(with aii inner member which protrudes frorn the outer suction skiftj until a portion of iie inrigr member which protrudes frorn the outer suction skirt penetnates the sea bed-

Qhee at least a portldn of the Inner member penetrates the sea bedi and befOie the outer suction skirt contacts the sea bed, the method rnay compise checking the position/leyel of the suction anchon If the suction anchor is net at the desired position, e.g. not ievej relatiye to the sea bed or not at the desired orientatiGn reiative to the seabed^ the method may comprise adjusting the po^^ such as ieweliing the suction ahChpr. bevelling the suciion anchor may comprise adjusting the position of the suction anchor, "ΓΙιβ adjustment of the suclon anchor may be achieved by adjusting the support {e.g. deptoymerit appratus| holding the suciion anchor (such as wires and winches). Additionally or aiternaiveiy, levelling the suction anchor may comprise using weight(s). The weight(s) may the weights diSGUSsei above in relation to the adjusting action which may occur before the inner member contacts the sea bed. The weight(s) may be put on the suction arschOr and may be moved/ have their position changed in Order to adjust the foundaiion and/Or the suction anchor into the desired angle retatiye to the sea bed. This desired angle may be the angle at which the inner member is perpendicular, or at least substantially perpendicular, to the sea floor. This is so that the resulting orientation of the foundation, when the support surface of the foundation is horizontal or at least subsiantiaily horizontai or parallel or substantially parallel to the seabed.

The position/ievel/orieniation (these terms may be used Interchangeably herein) Of the suction anchor may be checked and/or adjusted both before and after the inner m|mber has penetrated the sia; bed or it may only be checked and/or adjusted at one of these occasions;

Byichecking and/or adjusting the orientation of the suction anchor relative to the sea bed when only a portion of the inner member penetrates the sea bed means that it is possible to adjust the orientation of the suction anchor without having to use excessive force but means that there is a component whiGh acts to keep the position the suction anchor has been adjusied to.

The lowering and/or penetration of at least part of the inner member and/or outer suction skirt may be under the weight of the suction anchor itself;

Before the entire weight of the suction anchor is supported on the sea bed, i.e. dirirtg the initia! part of the penetration of the suction anchor (when part of the weight of the suction anchor may stiil be supported ly the deployment apparatus), the pethodi may comprise inducing the pressure within the suction anchor (i.e. within the inner rnember and/or outer suction skirt):, fhis may create a suction pressure which aGts to suck the suction anchor into the sea bed, at least in part. This may be done at the same time as, i.e. in coffiblhation with; adjusting the deploymeht apparatus holding of the suctio.n anchor (such as wires and winches| andlor tension in the lifting wires or performing some other ileyeiilng operation (as disedssed above). This may be done irrespective of whether the suction anchor has an inner member which protrudes from the suction anchor, i.e. this aspect of the invention may be Independently patentabie.

The method may additionaliy or alternatively comprise cycling the pressure within the suction anchor, (i.e. outer suction skirt and/or Inner member) during installation. This may comprise raising and lowering (i.e. reversing) the pressure inside the:outer suction skirt and/or inner member one or more, or a plurality of, timee. This may result in the suction anchor moving up and down relative to the sea bed. This may allow additional penetration of the suction anchor to be achieved into a sea bed.

This aspect of the invention may be ihde|endently pateriiabie from the other features of the invention, i.e. the suction anchor does pot necessarily need to have an inner membef whiqh protrudes from the suction ahohpr.

Thus in another aspect the present invention may comprise a method of installing a suction anchor, the rneilod comprising reducing the pressure inside the suction anchor to suck the suction anchor into the sea bed, and increasing the presstfre inside the suction anchor to move the suction anchor out of the sea bed before again reducing the pressure inside the suction anchor tc suck the suction anchor Into the sea bed. The cycle of Ipwehng.....raising and then lowering the pressure inside the suction anchor may be perforrned two or rnore times and may be repeated until the suction anchor fully penetrates the seabed.

Once the suction anchor is at a desired position (e.g. level within an acceptable limit, which may for example be up to 1, liS:, 1.5 or 2degrees from vertical relative tO thessea floo|, the suotiOh anchor may be lowered further until the outer suction skirt coritacts the sea floor. The method rriay comprise lowering the suction anchor under the action of its own weight. The suction anchor, i.e. the inner member and outer suction skirt, may be towered under the action of its own weight until it is fully supported by the seabed and does not penetrate the sea bed any further. The suction anchorman not penetrate the seabed any further under the action of its oyyri weight due to frictiors acting on the suction anchor.

The weight of the suction anchor miay push a portion of the inner mernber and the outer skirt into the sea bed.

If the weight of the suction anchor alone is not sufficient to push the outer suction skirt into the sea bed, the method may comprise applying additionai force to the suction anchor to cause the suction skirt into the sea bed such that the suction anchor can be sucked into the sea bed by reducing the pressure inside the suction skirt.

The additionai force may be provided by putting additionai weights, such as ba last, grave! bags or rocks, onto the suction anchor. These Weights may also be used to control/adjust the orientation of the roundation during ihstailation, i.e. these may be the above described weights.

The additional force may be provided, ih the case that the inner member is a pipe, reducing the pressure in the inner member sup that the inner member is sucked into the seabed which wii! suck the outer suction syrt into the seabed.

The suction anchor may be lowered Until it is supported entirely by the sea bed. At this point the suction anchor may be sucked into the Sea bed or additional fore may be applied to the section anchor until the outer suction skirt can be sucked into the sea bed.

Once the suction anchor is supported entirely by its own weight and/or additional downward force is applied to the su^ion anchori the outer suction skirt may have penetrated the sea bed sufficiently such that the method may comppe removing fluid (thisfltild may for example be sea water or aif| from inside the suction skirt. The removal of this fluid may reduce the pressure inside the suctidri skirt such that the supon anchor may be sucked into the sedbed so as to form the subsea foundation.

The method may coraprlse installing the suctiOn anchor with the long inner member in the sea bed without first removing soil for the inner member.

In the case Of a subsea well foundation, the inner member (which may be a pipe for a well) may have the fljnction of preventing or minimising washout which occurs around the weiL

The inner member may have the function Of apng as a dentratiser’ to help erasure that the foundation, and hence device supported by the foundation, are at a disiFed orientation suei> as, in tiFte ease of a v«ell \rertieai or within an accepfaife limit (such as .jp to % 1,2, 1,5 or2 degreesj from vertical.

The inner nember/subsea (vvel| foundation raaf have the function of providing lateral support for a well which extends ther^hrough.

The Inner rnember/subsea (Vv'eii) foundation may have the functiOil of providing bearing capacity tor a well which extends therethrou|h.

The subsea foundation may comprise a plurality of suction ahohors.

This feature may be independently patentable of the above described features, iheluding the optional features, of the subsea foundation and its methcc! of installation or may be provided in combination with one or more of the fdatureSi or optional features. (ine or more of the plurality of suction anchors may comprise one or more of the above described features. For example, one or more (but not necessarily a!!) of the plurality of suction anchors may have an inner member which protrudes from the outer suction skirt,

In a third aspect, the present invention may provide a subsea foundation, the foundation Gompfisihg: a: plurality of suctipn anchors, wherein at least one of the suction anchors is for prOVidihg a foundation for a subsea device..

The subsea foundatioti may be a subsea well foundation. The subsea device may be a subsea well. At least one the anGhors may be for having a well extend therethrpdgh.

Thus the present invention may provide a subsea vveil foundation, the foundation cornphsing· a plurality of suction anchors, wherein at ieasrt one of the suctibh anchors is for having a well extend therethrough. in a third aspeeti the present invention may provide a method of installing a subsea foundation the method comprising; providing a plurality of suction anchors, wherein at least one of the suiiion anchors is for providing a foundation for a subsea device, and sucking at least one of the suction anchors into a seabed·

The subsea foundation may be a subsea wetl foundation.

At least one of the suction anchors may for laving a well extend therethrough.

Thus, the present invention may provide a method of installing a subsea well foundation, the method comprising: providing a plurality of suction anchors, wherein at least one of the suction anchors is for having a wetl extend thereihroigh, and sucking at least one of the suction anchors ihto: a seabed.

One or more of the suction anchors of the plurality of suction anehofb may he the above described suction anchor; However, this is not essential and for example, none of the suction anchors may have an inner member vvhich protrudes from the suction skirt. The method of ihstaltihg the subsea ioundatldh may comprise one or rnore features of the above described installaiion method·

The foiiowing discussion of optional featufes applies to both the invention« of the first and second aspects (in the case that the subsea foundation compriSGs a plurality of suction anchors) in addition to the third and fourth aspects of the invention. A suction anchor may be referred to as, and may encompass a euctidn catSson, a suction pile, a suction bucket and/dr a suction can.

Each of the suction anchors may be for providing a foundation for a subsea device. Aiternatively only one, or some of the plurality of suction anchors may be for providing a foundation for a subsea device. The dther of the plurality of suction anchors rpay be for helping to level the suction anchor(s) which in use wii! provide a foundation for a subsea device, as discussed below.

Each of the suction anchors may be for having a well extend iherethrough, Alternativeiy only one, or some of the plurality of suction anchors may be fdr having a well extend therethrough. The other of the plurality of suction anchors may be for heipihg to level the suction anchor(s) which in use will have a %eii|heretirough, as discussed below.

Each suction anchor which is for having a well extend themShFoush may be for having only onesWeil extend therethrough. VVhen the foundation comprises a Rlurallty of suction anohofS, only one of the suction anchors may have an inner member,

The inner member may not necessaily lave a channel therethrough and may be an inner member which acts to allow the orientaiion of lhe foundation to be controlled as discussed above in detail.

Each suction anchor may comprise a suction skirt. The suction skirt may define a volume, which in use......the pressure can be reduced in sueh that the suction anchor may be sucked into the ground.

The method may comprise reducing the pressure in ohe or more of the suction anclors so as to suck the suction anchors into the ground.

The suction anchors may be connected tqgeiher. For example the suction anchors may be rigidly connected to each other.

Tile connection between the suclibn enehprB may be at a location whiob, when the suction anchor is installed in the #a bed, the connection, or at least a portion of the connection, is in the sea bed. th other words; as the suction anchor is lowered and|or suctioned into the seabed, the cOhhection portion may also penetrate the sea bed.

The connection may be at the bottom, or towards the bottom; of the suction anchors connected by the connection.

This means that the foundation may be stlffer such that forces can be eieGtively transferred between the suction anchors,

The connection may act as a spacer to hold the suction anchors at a fixed distance from each other, eWn as the suction anchors are penetrating the seabed.

The connection may have a relatively small dimension i.n a direciion which is parallel to the plane of the seabed. This i| so that the: connection, if it itself penetrates the sea bed, may provide only i rolatiyely small resistance to the penetration of the suction anchors into the Sea bed.

The connection may for example be Ohi Or rnop plate(s) between the two suction anchors. The plane of the plate(s) maf be berpOhdicular to the piane of the sea bed.

Each suction anchor may have, or be arranged to be connected to, a separate device, such as a pump, for reducing pressure inside the suction anchor (for providing the suction forpe)· Each pressure reducini device may be independently controifabie, %ernativeiy, the foundalion rrtay have a plurality of independently controllable vaives that allow the pressure in each of the suction anphois to be controlled independently. Thus, theloundatidh may be arranged so that the pressure in each of the suction anchors is independentiy controllable. This means that it may be possible to ieve! the subsea fouridation using the independently controllable suction anchors.

One or more of the suction anchors may be controlled so as to cycle the pressure or reduce the pressure before the full weight pf the feundation is on the sea bed (as is discussed above In raore detail).

For example, the method may comprise putting the suction anchors on the seabed and allowing the suction anchors to penetrate the seafloor by action of their own weight. The suction anchors may then be sueired into the seabed by removing fluii from iHSide the suction skirt of the suction an#ier;

The level Of the subsea foundation (i.e. angle of the top/support surface relative to the sea bed), or at least part Of i| suoh as suction anchors which are for providing a foundation for a subsea device, such as having a well extend therethrough, may be cheoked. If the level needs to be adjusted, this may be achieved by reducirig the pressure in one suction anchor compared to another Of the sUGtion anchors. The method may comprise independently controlling and/or adjusting the pressure in each of the suction anchors.

In this way, dlflireht forces can be applied on each of the suction anchors so that the angle: of the: foundation relative to the sea bed can be adjusted.

Thu|, thessuetlon anchors may be controlled so that the foundation can be levelled.

The subsea foundation may comprise at least three suction anchors.

When the subsea foundation comprises at least three suction anchors the suction anchors may be arranged so that they are not in a line. For example, the suction members may be in a triangle, square or L-shaped arrangement. This is so that the orieniation of the foundation can be controlled into two different dimensions, i.e. both the roil and pitch of the foundation may be controlled.

The suction anchors may be arranged so that both the roll and pitch of the subsea foundation may be controlled. The suction anchors may be arranged so that the orientation can be cohtfolled in two orthogonal directions (\Vhich may both be paraliel to the surface of the seabed).

The method of Installation of the subsea foundation of any aspect of the inwention may comprise providing :ohe or more of the features of the subsea founiation. the suction anchor may be a tall steel cylindrical structure t|at is open at the bottom and dosed at the top. The suction anchor may have ah internal stiffener system and may be used to support subsea structures. The suction anchor may be instaiied by first lowering it into the Soil to self-penetration depth (i.e. penetration due to submerged anchor weight). The remainder of the .required penetration may be achieved by pumping out the water trapped inside the suction anchor.

Any features, including optional features, of an aspect of the invention may be applied to any other aspect of the invention.

Certain preferred embsiimentS of the present invention will now be described by way of example ohiy with reference to the apppmpanying drawings, in which·

Figure 1 shows a subsea welt foundation;

Figure 2 shows another subsea well foundation;

Figure 3 shows the subsea well foundation of Figure 2 in side view;

Figure 4 shows the subsea well foundation of Figure 2 in side view in lottam perspective view;

Figure 5 shows another subsea well foundation;

Figures 6 to 9 show an instaiiation itiethod; and

Figure 10 shows a subsea well foundation with ffiovable weights thereon.

Figure 1 shows a subsea foundation: 1. In this ease the subsea foundation is a wei! foundation. However, the sape coneept could equally be used as a fGundatlon for a different subsea device sueh a® ^ pupp station. the foundation 1 comprises a suction anchor % through which a well (not shown in this figure) can extend. The suition anchor 2 comprises an outer suction sitirt 4 and an inner pipe 6. The inner pipe 6 extends beyond the bottom of the suction skirt 6. in use, the well extends through the inner pipe 6. ©h top of tie suction anchor 2 is protection and support equipment 8. Once the foundation is fuliy installed production equipment such as a BOP may be mounted on the protection equipment 8.

The suction anchor 2 is arranged so that when it is piaced on the sea bed the inner pipe 6 will contact and penetrate the sea bed before the outer suction skirt 4. This means that a part of the suction anchor 2 can be in the sea ped whilst ievellihg operations are carried out·

Figures 2 to 4 show an alternative subsea weit feondatiDn 1Θ0·. This alternative foundation 100 Colnppes a plurality of suction anchors 2. Each of these suction anchors 2 is the same as the above described suction anchor 2 which is shewn in figure 1. ii\s can be seen most clearly in Figure 4, the inner pipe 6 comprises an upper inner pipe portion 6a and a lower Inner pipe portion 6b. The upper inner pipe portion 6a is tooaied within the outer suction skirt 4 and does not protrude therefrom. This makes iransportation of the suction anchor 2 more straighddrward. Alternatively the inner pipe 6 may be a single piece which is attached to the suction skirt 4 either before deployment subsea or after deployment subsps.

The lower inner pipe portion 6b (when the inner pipe i is In rnuitipie parts) can be conneGted to the upper inner pipe portion 6a to form the inner pipe i which protrudes from the outer suction skirt; The lower inner pipe portion 6b may be

Gonne|teM|| to the suction anehor t when the eonpipDfients are subsea but before any part has started to penetrate the seabed.

In the foundation 100 shown in Figures 2 to 4, the right harid inner pipe 6 is shown in its configuration for being penetrated into the sea bed ti e. with the inner pipe 6 connected to the stietion skirt 4) and the left hand inner pipe 6 shows the lower inner pipe portion la in a position ready to be connected to the upper inner pipe portion 6a.

The suction anchor(s) may comprise a piurality of stiffener plates 7 which exiend between the outer suction sKirt 4 and the inner member 6. This can be seen for exarnpie in Figure 4. 4 sihile protection ©pipmehi 8 is used for the plurality of suction anchors 2, i.e: there iS one protection equiprhent S for the eritire subsea well foundation 100. The protection equipment 8 may thus be used to connect the suction anchors 4.

The suction anchors 2 are (perhaps also) connecied by a connector 10.

Connection 10 is provided in a location which, when the suction anchors are installed subsea, will be in the sea bed. The connection 10 is provided towards the bottom of the suction skirts 4. The conneGtioh 10 will be submerged in the sea bed when the foundation 100 is inslaited.

Figure 5 shows an aiternatiye subsea well fouridatipn 200 which comprises a plurality of suction anchors 2 but in which the inner pipe 6 does not pt^Fude frorn the bottom of the outer Suction sy;rt; 5,

Figures 6 to i show an exerriplary installation method.

In an example installation rnethoct, first the inner pipe 6, or a portion of the inner pipe 6a is deployed subsea and put on the sea bed as shown in figure 6. The rest of the foundation 100 is then deployed subsea. During insialiatioii the ijundation 100 is supported by a vessel 12 by deployment apparatus 14 vvhioh Gomphses guide yyires 15, winOhes 17 and support lines 19,

The foundation 100 is supported subsea and a guide wire 15 is fed through the suGtion anchor 2 of the foundation 100 and connected to the inner pipe 6 (or portion of inner pipe 6a) The guile vyire 15 is used to lift t|e inner pipe 6 off the sea bed and guide it to the bottom of the suction anchor | Adhere it will be attached:

The inner pipe 6 is attached to the suction anchor Sp that the inner pipe 6 pfotfudes from the bottom of the outer suetion skirt 4. An inner pipe 6 which is attached is shown on the right hand side qff the foundatioh 100 infigup 6 and on the left hahd side is fhewn a pipe 6 lying of the sea bed and an inner pipe 6 about to be connected to the bottom of the suction anchor 2,

Figure 7 shovvs the foundation 100 with the inner pipes 6 attached and protruding from the bottom of the outer suction skirts 4. The foundation 100 is lowered towards the sea floor. The foundation 100 may optionally be held for a period of time jUSt above the sea floor to give time for the foundation 100 to level under its own weight andlor the orientation of the foundation 1p may be controlled by mpying weights 12 positioned on the foundatibh 100 (see figure 10) or adjusting the support lines 19.

Whilst both suction anehors 2 are shown having inner pipes f which protrude from the bottom of the sucidn skirt 4, it may be that dniy ine of the suction anchors 2 has an inner pipe 6 which protrudes from the bottom of the suction anchor 2, Of in the case that the fbuFidation 100 comprises more than two suction anchors 2, some, but hot all of the suction anchors 2 may Gomprise an inner pipe 6 which protrudes from the bottom of the suction skirt;

The foundation 100 may be lowered further until a pofiod of the idner pipe(s) 6 has penetrated the seabed as shown in figure 8. At this ροίπΤ the angle of the foundation 100 relative to the seabed may be checked and adjusted Again, the orientation of the foundation 100 may be Controiled by moving weights 12 positioned on the foundation 100 (see figure 10) or adjusting support lines 1|. The position of the foundation 100 may be adjusted until the Inner pipes 6 are yerticai relative to the seabed, at least substanlially vertical or vertical within an accepiable limit.....such as up to 1, 1.2i T5 or 2 degrees ibm vertical.

The adjustment may be achieved |y adjusting the deployment apparatus 14 so as to adjust the angle of the foundation 100 and/or by adding weight(s) (such as ballast, pre^filled gravel bags or rocks or other material form the sea floor) to the top of the foundation which can be moved to ailow the angle of the foundation 100 relative tb the seafloor to be adjusted.

As shown in Figure 10, weights 12, suchsas ballasl weights, may be provided on the fOundaiion 100. The weights are each supported on a support frame 13. The weights 14 and their respective support frame 11 may be removable after installation.

The viieights 12 may be movable during installation of the foundation 100 so as to allow control of the prientalion of the foundation 100 during instaiiatidn. This movement of the weights 14 may be achieved by using hydraulic jacks 14. A plurality Q|]aGks 14 may be provided so that the weight 14 can be moved in at least two different direciions. this is so that the pitch and rol| pf the fbunetation 100 can be adjusted as required.

Each of the movable weights 14 may be associated with a control panel and inclinometer 16. The orientation of the foundation 100 may be checked during Installation by the inclinometer and the weights 14 may be moved automatically in lesponse to the sensed orientation of the foundation 100.

Due to the fact that the inner pipes 6, and only the inner pipes 6, are in the sea bed when the angle of the foundation 100 is adjusted, it is relatively easy to adjust the angle of the foundation 100 (as the inner pipes 6, compared to the suction skirts 4| provide a relatively small resistance to a change of angle of the foundation 100). ¥et, because the inner pipes 6 ap submerged they provide some resistance to rnotion so as to help retain the foundatldi: |00 in the desired orientation as it is further lowered towards the se|bed·

Once in the desired position, e.g. with the inner pipes vertical or substantially vertical the foundation 100 is lowered fdrther under the action of its own weight until the outer suction skirt 4 reaches and starts to penetrate the sea bed.

Once the foundation 100 is fully supported on the seabed (and prevented from penetrating any further by action of friction) and at least the bottom portion of the suction skirts 4 are in the sea bed, the pressure in the suction anchors 2 may be reduced so as to cause the suction anchors | to; suck ihtP the seabed. The pressure In the sut^ion anchor 2 may be reduced by pumping fluid out of the volume creatediwilhih; the suction skirt 4. Fluid is pumped dui until the suction Skirt is sucked into the sea bed by a sufficient arhbunt, for exarnpie as shown in Figure 9. The deployment apparatus 14 may then be removed and then further well operations (such as the addition of production equipment) required on the foundation 100 may b© performed.

When the foundation 100 comprises a plurality of suction anchors 2, the presstiis in each suction anchor 2 may be independently controllable. This independent control may be used to adjust the level of itte foundation reiative to the sea bed to ensure that the foundation is fixed into the sea bed in a position in whicl the wells running through the suction anchors 2 wili be at least substantiaiiy vertical. Thus, when the foundation 1Q0 comprises a piuplity of suction anchors it is not essential that the inner pipe 6 protrudes from the bottom of the suction skirt 4 ip allow the wei!(s) to be made vertical. This is because independent control of the pressure Inside each of the suction anchors 2 may instead be used to ensure that the resulting wells are at least substantially vertical.

Claims

CLAIMS;

1. A method of ihStalling a subsea foundation, the method Comprisin|; providing a suction anchor, the suetion anchor comprising an inner member and an outer suction skirt located around the inner membe| wherein the inner member protrudes from the outer suction skirt; moving the suction anehOF towards a seabed so the inner memher penetrates the seabed before the outer suction skirt; further moving the suetion anchor towards the seabed uhttl the outer suction skirt reaches the seabed; and sucking the suction anchor into the sea bed,
2. A method according to claim 1, wherein the method compfises: attaching at least the portion of the inner member which protrudes from the outer suetion skirt at the installatioin site. 3; A method aGCordihg to claim 1 or 2, Wherein the m#hod comprises; attaching at least the portion of the inner member which protrudes from thp outer suction skirts to the outer suction skirt «men both eamponents are sUbS|a.
4, A meihod according to claim 1,2 or 3, wherein the method comprises: selecting the length of the inner member that protrudes from the outer suction skirt based on the geology of the instaliation Site.
5. A method according to any preceding claim, wherein once at least a portipn of the inner member penetrates the sea bed, and before the outer suction skirt contacts the sea bed, the meihod comprises checking the angle of the suciioi: anchor relative to the sea bed. 6; A method according to any preceding claim^ wherein once at least a portion of the inner member penetrates the sea bed, and before the outer suction skirt contacts the sea bed, the method comprises adjusting the angle of the suction anchor relative to the sea bed.
7. A rnethijd according to ciaim 6, whei^in adjusting the angle of the suction anchor is achieved hy adjusting a support holding the subsea foundation.
8. A method according to claim 6 or 7, therein adjusting the angle of the suction anchor is achieved using weight|$| which are added tO the subsea foundation. A method according to ciaim 8, wherein the method comprises raowng the weight(s) to adjust the angle of the suction anchor. 1Θ. A method acccrding to any preceding ciaim, wherein onoe the suction anehor is at a desired angle relative to the sea floor, the suction anchor is lowered iirther until the outer suction stdrt contacts the sea floor:
11. A method according to any preceding claim, wherein the inner member is a loliow body and the method comprises reducing the pressure inside the inner member. 12^ A method according to any preceding ciaim, wherein the method comprises reducing the pressure inside the suction anchor before the full weight of the suction anchor is supported by the seabed.
13. A method according to any preceding ciaim, wherein the method comprises cyciing the pressure within the suction anchor.
14. A method according to any preceding ciaim, wherein the method comprises providihg at ieast one additional suction anchor such that a plurality of suction anchors is provided.
15. A method according to claim 14, wherein the plurality of suction anchors are connected and wherein the connection is at a location WhiGh is ih the f ea bed when the suction anchors have been sucked into the sea bed. If. A method according to claim 14 or 15, wherein the method comprises independehtiy controlling the pressure in each of the suction anchors. 17 A method aeeording to ariy preceding claim, wherein tie siibsea fouida|On is a subsea; well foundaion and the inner member is an inner pipe for a well.
18. A subsea foundation, the ifeundation eomprisihg: a suction anohor, the suction anchor comprising an inner member and an outer suction skirt located around the inner member, wherein the inner member protrudes from the outer suction skirt.
19. A subsea foundation according to claim 18, wherein the length of th©: inner member protruding from the suction skirt is 0.1 to 5 times the diameter of the outer suction skirt, io. A subsea foundation according to claim 18 or 19, wherein the inner member eomprises an upper inner member portion and a lower inner rnember portion.
21. A subsea foihdatipn according to claim 20. wherein the upper inner member portion does not protrude from the outer suction skirt.
22. A subsea foundatiDh according to any of claims 18 to 21, wherein the sybsea well foundation comprises a plurality of suction anchors.
23. A subsea foundation according to claim 22. wherein only one of the suction anchors has an inner member that protrudes from the outer suction skirt.
24. A subsea foundation according to claim 21 or 23, wherein the plurality of suction anchors are connected together by a connection and wherein the connection between the suction anchors is at a location which, when the suCtidh anchor is installed in the sea bed, the eonnectioni or at least a portion Of the Gonneciion, Is bed.
25. A subsea foundation according to claim 21, 22 or 23, wherein the connection between the plurality of suctidh members is a ptate between two suction anchors. 2i. Jk subsea foundatibh aspording to arp Df Plaiibs 21 tp iS, wfienein each suctido anchor has a separate indedendehtiy eehtroiSable device for reducing pressure iriSide the suction anchor.
27. A subsea foundation ac^Fding to any of claims 18 to 26, wherein the sufcisea foundation is a subsea well foundation and the Inner member is an inner pipe fer a well.
28. A rheihod according to any of claims 1 to 17, wherein the subsea foundation is a subsea foundation according to any of diaims 18 to 27. |9. A subsea foundation, the foundation comprising; a plurality of suction anchors, wherein at least one Of the suqtipn anchors is for providing a foundation for a subsea device. 3|, A subsea foundation according to ciaim 26, Wherein the plurality of suction anchors are Gonneetld together by a connection and wherein the connection between the suction anchors is at a ioeation which, when the Suction anchor is installed in the sea bed, the POnnePtion, or at least a portion of the connection, is in the sea bed> Jl . A subsea foundation according tO claim 29 or 30, wherein the connection between the plurality of suction rnembers is a piate beiweeh two suction anchors. W. A subsea foundation aPQOFding to any of Pialms 29, 30 or 31, Wherein each suction anchor has a separate independently controllable device for reducing pressure inside the suction anchor.
33. A subsea foundation according to any of claims i9 to 32, wherein at least one of the suction anPhors comprises an inner mernber and an outer suctidn stcid located around the inner rnember, wherein the inner member protrudes from the outer suction skirt, 3^. Ά sibsea loundaiion according to claim 33, wherein only one of the suction anchors has ari ihrier member that protrudes from the outer suction sliirt.
35. A subsea foundation according to claim 33 or 34, wherein for each suction anchor that cohhpnsee an ihner member, the iehgth of the inner member protruding froth the buter swction shiii: is 0.1 to 5 times the diameter of the outer suction skirt.
36. A subsea foundatioh aecohdihg to claim 33, 34 or 35, wherein for each suction anchor flat eomprises an inner member, the inner member comprises an upper inner member portion and a lower inner member portion.
37. A subsea foundation accerdirtg to claim 36, whemin the upper inner member portion does nd prcrtrude from the Outer suction skirt,
38. A subsda foundatiori according to any of ciairns 21 to 37, wherein the subsea foundation is a subsea well foundation, and wherein at least one of the suction anchors i| for hawini a well extend therethrough.
39. A subsea foundation accordingto claim 3|, when dependent on any of claims 30 to 34, wherein each inner member is an inner ptpe for a well.
40. A method of installing a subsea foundation, the rf|eihod compfisihg: providing a plurality Of suction anchors, wherein at least one of the suction anchors is for proyidini a foundation for a subsea device; and sucking at least one of the suction anchors into a seabed. 41 A method according to Claim 40, wherein the plurality of suction anchors are connected and wherein the connection is at a location Which is in the sea bed When the suclon anchors have been sucked into I* o sea bed, 42 A method according to Claim 40 or 41, wherein each suction anchor has a separate, independently controllable device for reducing pressure inside the suGti^ii itiehor and wherein the rhethdd comprises independently cdhirolli^ the pressure in each of the suction anchors.
43. A method according to claim 4i, 41 or 42, wherein at least one of the suction anchors comprises an inner member and an outer suction skirt located around the inner mernfeer, wherein the inner member protrudes trorn the outer suction skirt; and wherein the method eohipriSeS: moving the suction anchor towards a seabed so the inner member penetrates the sealed before the outer suction skirt; further moving the suction anchor towards fie seabed until the outer suction skirt reaches the seabed; and sucking the suciiOn anchor into the sea bed, 44 A method according to claim 43, wherein the method comprises: attaching at least the portion of the inner member vsihieh potrudeS from the outer suction skirt at tie thi^allaticn site;
45. A rnethod according to ciairn 43 or 44, wherein the method comprises; altaching at least the portion of the inner member which protrudes from the outer suction skirt, to the outer suction sldrt when both components are subsea,
46. A method according to claim 43, 44 or 45, wherein the method comprises; seiecting the length of the inner member that protrudes from the outer suction Skirt based on the geology of the instatiatidn Site.
47. A method according to any of claims 43 to 46, 'herein once at least a portion of the inner member penetrates the sea bed, and before the outer suction skirt contacts the sea bed, the; method comprises checking the angle of the suction anchor relative tp the sea bed.
48. A method according to any of Gfaims 43 to 47, wherein once at least a portion ofthe inner member pehetrates the sea bed, and before the outer Stietion skirt contacts ttie sea bed the method comprises adjostlhg the angle of the syction anchor relative to the spa bed;:
49. A method acbording to claim 41, wherein adjusting the angle of the suction ancbOf is achieved by ac^usting a support holding the foundation.
60. A method according to claim 48 or 41; wherein adjustihg the an§!e of the suchbn anchor is achieved using weighttsl which ai^ added to the fpurrdation.

51. A method aGCording to Glairh 50, wherein the weighttl) are movable.

52. A method according to any of claims 43 to 51, wherein once the suction anchor is at a: desired angle relative to the sea floor, the suction anchor is lowered fuiher until theputer suction skirt contacts the sea floor.

53. A method according tp any of claims 40 to 62, Wherein the subsea foundaiion is a subsea well foundation, and wherein at least one of the suction arKtsors is for having a wet! extend therethrough.

54. A subsea fbundation aceording tp claim 53, when dependent on any of claims 43 to 62, wherein each inner rnember is an inner pipe for a well.
65. A rhithod according to any of claims 40 to 54, wherein the subsea foundation is a subsea foundation according to any ofcfaims 29 to 39;