Lining boreholes through soft formation

Abstract

Method of forming a lined borehole, the method comprising steps of: - radially expanding a tubular element in a borehole by bending an unexpanded tubular section of the tubular element radially outward and in axially reverse direction so as to form an expanded tubular section extending around the unexpanded tubular section, wherein the bending occurs in a bending zone; and - increasing the length of the expanded tubular section by pushing the unexpanded tubular section in axial direction relative to the expanded tubular section further into the borehole, thereby lining the borehole with the expanded tubular section; wherein a majority of the borehole passes through soft formation, for example comprising sand, mud, clay, loam, and / or silt.

Description

[0001] Title: Lining boreholes through soft formation

[0002] TECHNICAL FIELD

[0003] The aspects and embodiments thereof relate to the field of radially expanded tubular elements in boreholes.

[0004] BACKGROUND

[0005] W02008006841 discloses a method of radially expanding a tubular element extending into a wellbore formed in an earth formation. The method comprises inducing the wall of the tubular element to bend radially outward and in axially reverse direction so as to form an expanded tubular section extending around a remaining tubular section of the tubular element, wherein said bending occurs in a bending zone of the tubular element. The method further comprises increasing the length of the expanded tubular section by inducing the bending zone to move in axial direction relative to the remaining tubular section.

[0006] WO20 14072381 discloses a method for transporting a hydrocarbon fluid, such as crude oil and / or natural gas, comprising drilling a chain of double ended U-shaped boreholes into the earth crust, such that at least one pair of the boreholes has an adjacent pair of upper ends at or near the earth surface, lining each of the boreholes with an at least partly expanded impermeable liner comprising an expandable tubular, which is circumferentially expanded after insertion into the borehole, interconnecting each pair of adjacent upper ends of the chain of lined U-shaped boreholes by a connection conduit, and transporting the hydrocarbon fluid through a transportation pipeline with one or more W-shaped sections provided by the chain of lined U-shaped boreholes and the connection conduit. Through soft formation, steel pipes may be laid. Such steel pipes may for example be coated for corrosion protection, for example with a coating comprising asphalt bitumen, concrete, PE , or a composite material.

[0007] SUMMARY

[0008] It is an object of the present disclosure to transport one or more fluids, such as one or more liquids and / or gases, through a borehole. The liquids and / or gases may for example be hydrocarbons or hydrogen. Another object of the present disclosure is to position one or more cables for transportation of electrical energy and / or electrical signals for example for telecommunication in a borehole.

[0009] Each of these objects is preferably achieved for a borehole which passes through soft formation, in particular for a borehole of which more than 25%, more than 50%, more than 75%, more than 85% or even more than 95% passes through soft formation. When more than 95% of the borehole passes through soft formation, the borehole is considered to pass essentially entirely through soft formation.

[0010] Each of these objects is preferably achieved for a borehole which is at least partially oriented at an angle relative to vertical, or even at least partially horizontally oriented.

[0011] A first aspect of the present disclosure contemplates a method of forming a lined borehole, comprising steps of radially expanding a tubular element in a borehole by bending an unexpanded tubular section of the tubular element radially outward and in axially reverse direction so as to form an expanded tubular section extending around the unexpanded tubular section, wherein the bending occurs in a bending zone; and

[0012] -increasing the length of the expanded tubular section by pushing the unexpanded tubular section in axial direction relative to the expanded tubular section further into the borehole, thereby lining the borehole with the expanded tubular section; wherein a majority of the borehole passes through soft formation, for example comprising sand, mud, clay, loam, and / or silt.

[0013] Soft formation may comprise sand, mud, clay, loam, silt, and / or any other soft formation optionally combined with water, gases, organic matter, and / or any other matter, in any combination thereof. Soft formation may comprise loose particles, the dynamic behaviour of which may resemble that of a fluid. Contrary to forming a borehole through hard formation, such as rock, a borehole through soft formation is very prone to collapse. By virtue of the borehole now being lined with the expanded tubular section, collapse of the borehole can be prevented.

[0014] Collapse of the borehole is most prone to happen when the borehole passes through soft formation, and when at least part of the borehole has a substantially horizontal section, in particular when more than 50% or even more than 80% of the borehole is substantially horizontal. It will be appreciated that in the context of the present disclosure substantially horizontal encompasses angles within 15 degrees deviation from horizontal.

[0015] When the borehole enters the Earth’s surface at an entry point, and exits the Earth’s surface at an exit point at a distance from the entry point, the borehole can be used to transport fluid and / or cables from the entry point to the exit point. Any distance may be present between the entry point and the exit point, for example in the order of tens of metres, kilometres, tens of kilometres, or even hundreds of kilometres or more.

[0016] In any lined borehole disclosed herein, one or more cables may be positioned. The cables may for example be used for transporting electrical energy and / or telecommunication signals through. The one or more cables are in particular positioned in the tubular element, surrounded by the expanded tubular section. When the tubular element comprises an unexpanded tubular section, the one or more cables can be positioned in the unexpanded tubular section. It will be appreciated that the unexpanded tubular section may be removed, for example after the entire borehole has been lined with the expanded tubular section. The material used to form the unexpanded tubular section can then or example be re-used or recycled, while the expanded tubular section remains lining the borehole and preventing the borehole from collapsing.

[0017] In any embodiment of the methods disclosed herein, a maximum depth of the borehole may not exceed 500 metres, preferably does not exceed 200 metres. The maximum depth may be defined relative to ground level, or water level in case the borehole passes underneath a body of water, or relative to the sedimentary bed, such as a sea bed, of the body of water. As a result of the maximum depth, the tubular element is still buried beneath the soft formation, but an unnecessarily high depth may be avoided.

[0018] In any method disclosed herein, the borehole may enter the Earth’s surface at an entry point below a body of water, such as a lake, sea or ocean. Typically, a sedimentary bed below such a body of water is formed by soft formation. The method according to the first aspect may as such be an alternative to using jetting to bury cables and / or conduits in the sedimentary bed.

[0019] In any method disclosed herein, the entire or part of the borehole may pass below a body of water. The body of water may in particular be subject to tidal influences.

[0020] It is envisioned that the tubular element may be supplied into the borehole either from land, but also from water. As such, in methods disclosed herein, the unexpanded tubular section is supplied from and / or anchored to a floating vessel or a vessel supported on the bottom of the body of water, such as a jack-up vessel. Alternatively, the unexpanded tubular section may be supplied from and / or anchored to an off-shore structure, such as a monopile of a wind turbine. When the unexpanded tubular section is supplied from and / or anchored to the off-shore structure, the unexpanded tubular section may pass through the off-shore structure. As such, for example, the use of a J-tube external from the off-shore structure may be avoided.

[0021] In particular when the unexpanded tubular section passes through the off-shore structure, the tubular element can pass below scour protection of the off-shore structure. As such, for example, it may be avoided that part of the scour protection has to be temporarily moved away to accommodate one or more conduits and / or one or more cables.

[0022] It may be preferred to dimension the tubular element such that the expanded tubular section has a larger diameter than the drilled borehole. In use, the expanded tubular section may thus increase the diameter of the borehole that has previously been drilled.

[0023] In a second aspect of the present disclosure, different uses are envisioned of a lined borehole formed using any method according to the first aspect.

[0024] For example, CO2 may be transported through the lined borehole. In particular, CO2 may be transported from a location on land to a location on a body of water, for example to an offshore well where the CO2 can be stored for carbon sequestration.

[0025] In another example, hydrogen gas may be transported through the lined borehole. For example, hydrogen gas may be transported from a location on a body of water to a location on land.

[0026] In yet another example, water, such as salt water, may be transported through the lined borehole.

[0027] A third aspect provides a structure arranged to be used as an offshore structure, such as a monopile, the structure comprising a support frame, arranged to be driven into or supported onto a sedimentary bed, such as a seabed, and arranged to support an offshore element such as a wind turbine, a passage passing through the support frame, and a tubular element, comprising an expanded tubular section connected to the support frame and an unexpanded tubular section arranged to be pushed into the passage, which expanded tubular section and unexpanded tubular section are connected via a bending zone.

[0028] The support frame may comprise a single body, or may be formed by multiple connected bodies. The support frame may be at least partially formed by a monopile, tripod, jacket, or any other offshore structure.

[0029] The tubular element is preferably already connected to the support frame on-shore where the structure has been manufactured.

[0030] When the passage runs from a top side of the support frame to a bottom side of the support frame, the tubular element may run through the support frame, and subsequently into a sedimentary bed into which or onto which the support frame is positioned. At the top side of the support frame, for any offshore structure disclosed herein, a device may be provided for pushing the unexpanded tubular section further into the passage.

[0031] BRIEF DESCRIPTION OF THE FIGURES

[0032] In the figures,

[0033] Fig. 1 schematically shows a section view of a borehole;

[0034] Fig. 2 A schematically shows a monopile;

[0035] Fig. 2B depicts the monopile of Fig. 2A, wherein a tubular element 200 has been passed through the conduit;

[0036] Fig. 3 A schematically depicts two separate monopiles;

[0037] Fig. 3B shows the situation of Fig. 3A after a connection has been formed;

[0038] Figs. 4A and 4B depict another example of an offshore structure;

[0039] Fig. 5A schematically shows a general example of a situation wherein a borehole is being lined with a tubular element;

[0040] Fig. 5B shows the completed borehole, fully lined with the tubular element; Fig. 5C shows a detailed view of the process of lining the borehole;

[0041] Figs. 6A and 6B show two offshore structures; and

[0042] Figs. 7A-7C schematically depict an example of a method in which a single tubular element forming station is used in conjunction with multiple off-shore structures.

[0043] DETAILED DESCRIPTION OF THE FIGURES

[0044] Fig. 1 schematically shows a section view of a borehole 102 which is being lined with a tubular element 200. The tubular element 200 comprises an expanded tubular section 202 formed by radially expanding an unexpanded tubular section 204 inside the borehole 102. Shown as dotted lines in the shape of tubular element 200’ after further inserting the unexpanded tubular section 204’ into the borehole. As the unexpanded tubular section 204’ is moved further into the borehole 102, part of the unexpanded tubular section is expanded to form part of the expanded tubular section 202’. The radial expansion takes place in a bending zone 206. As the unexpanded tubular section 204’ is moved further into the borehole 102, the bending zone 206’ is also moved further into the borehole 102. By radially expanding the tubular element 200, the borehole 102 can be lined with the expanded tubular section 202.

[0045] Although not depicted in Fig. 1, it will be appreciated that a drill string may pass through the unexpanded tubular section. At a distal end of the drill string, a drill can be connected which can be supplied with torque and / or fluid via the drill string. The drill is typically positioned downstream of the bending zone 206.

[0046] Although Fig. 1 shows a straight and vertically oriented borehole 102, the same method of lining the borehole 102 can be readily applied to a curved borehole section and / or to a borehole section which is oriented at an angle relative to vertical, in particular even horizontal. Fig. 2A schematically shows a monopile 300 as an example of an offshore structure. In use, the monopile 300 may for example support a nacelle of a wind turbine. The monopile 300 typically partially extends above a water level 306 of a body of water, such as a lake, sea, or ocean. A base 302 of the monopile 300 is typically driven into the lake bed, seabed, ocean bed, or other body of sedimentary material 308 below the body of water. The top of this body is depicted by a dashed line in Fig. 2 A. Typically, the body of sedimentary material 308 comprises soft formation such as sand, silt and / or mud accumulated over time.

[0047] Typically, the base 302 of the monopile 300 is surrounded with scour protection 304. The scour protection 304 is typically designed to protect the base 302 of the monopile 300, for example from erosion. The scour protection 304 comprises hard materials such as rock, gravel, and / or concrete. In the prior art, typically an external J-tube is provided alongside the monopile, to feed one or more cables through. Alternatively, part of the scour protection is temporarily removed to positioned one or more cables below the scour protection.

[0048] The present disclosure contemplates passing a tubular element 200 through at least part of the monopile 300, and subsequently underneath the scour protection 304, as depicted schematically in Fig. 2B.

[0049] To this end, a conduit 310 can be provided through the monopile 300. Preferably, but not necessarily, an entry into the conduit 310 is provided above the water level 306, for example at or near a platform 312 of the monopile 300. The conduit 310 runs down the monopile 300 towards a location in the seabed 308.

[0050] The conduit is an example of a passage through the monopile. Any other passage may also be used, and the passage is not necessarily lined with the expanded tubular section, for example when the diameter of the expanded tubular section is smaller than the inner diameter or any inner dimension of the passage. Fig. 2B depicts the monopile 300 of Fig. 2A, wherein a tubular element 200 has been passed through the conduit 310. The conduit 310 has been lined with the expanded tubular section 202 in a manner similar to that shown in Fig. 1 - where the borehole 102 is substituted for the conduit 310. Preferably, the conduit 310 passes through the scour protection 304.

[0051] A drill 400 is schematically indicated in Fig. 2B. In use, the drill 400 can be used to form the borehole 102, and the drill 400 is typically positioned in front of the bending zone 206. A drill string (not depicted) may run through the unexpanded tubular section 204 to the drill 400, to supply fluid and / or torque to the drill. Preferably, the drill 400 can be steered in a particular direction to form a desired borehole trajectory which often will be at least partially curved.

[0052] As schematically indicated in Fig. 2B, an anchor 320 may be used to connect the expanded tubular section 202 to the monopile 300. Not depicted in the figures is that a tubular section forming module may be present to form the unexpanded tubular section. Furthermore, optionally, a drill rig may present to supply fluid and / or torque to the drill 400 via a drill string

[0053] Fig. 3A schematically depicts two separate monopiles 300, 300’, which conceivably could also be two of any other off-shore structure. A tubular element 200, 200’ has been ran through each of the respective monopiles 300, 300’. The tubular elements 200, 200’ pass into the sedimentary bed 308 of the body of water into which the off-shore structures have been positioned. In particular, the tubular elements 200, 200’ run into the sedimentary bed 308 via a base of the monopiles 300, 300’ which has been driven into the sedimentary bed 308.

[0054] In the situation depicted in Fig. 3A, it is objective to connect the tubular elements 200, 200’ of the monopile 300, 300’. When connected, a fluid communication can be established between the two monopiles via the connected tubular elements 200, 200’ and / or one or more cables can pass from one monopile to the other through the connected tubular elements. For connecting the tubular elements 200, 200’, distal ends 250, 250’ of the tubular elements have to be connected. As a particular option, it is envisioned to lift the distal ends 250, 250’ up towards the water level 306, for example to a floating vessel schematically indicated with square 330. On board of the floating vessel 330, the connection 332 between the tubular elements 200, 200’, in particular a liquid-tight connection, can be made.

[0055] Fig. 3B shows the situation of Fig. 3A after the connection 332 has been formed, and the connection 332 has been sunk into the body of water. As an option, the connection 332 may be jetted into the sedimentary bed 308.

[0056] It will be appreciated that as with all of the other figures, Figs. 3A and 3B are not drawn to scale and are schematic drawings indicating particular parts of the present disclosure. For example, in real-life, different radiuses may be used for the curved section of the tubular element.

[0057] As an alternative to the method depicted in Figs. 3A-3B, the tubular element 200 passing through the first monopile 300 may be guided such that it enters the second monopile 300’. As such, there is no need for the connection 332.

[0058] Figs. 4A and 4B depict another example of an offshore structure, in particular a jacket 340. The jacket 340 forms a support frame on which for example a wind turbine can be supported. A passage 310 runs through the jacket, preferably from a top side of the jacket where a platform 312 may be present to a bottom side of the jacket, preferably embedded into the sedimentary bed 308.

[0059] As schematically depicted in Fig. 4A, part of the passage 310 of the jacket 340 may already be lined with a tubular element 200, or at least an expanded tubular section may already be connected to the jacket 340 when the jacket 340 is positioned into or onto the sedimentary bed. Fig. 4B shows the jacket 340 after the entire passage 310 has been lined with the tubular element 200, and the tubular element 200 passes through the sedimentary bed, for example towards land or towards a further offshore structure. Fig. 5A schematically shows a general example of a situation wherein a borehole 102 is being lined with a tubular element 200 - in particular by bending an unexpanded tubular section of the tubular element radially outward and in axially reverse direction so as to form an expanded tubular section extending around the unexpanded tubular section, wherein the bending occurs in a bending zone. The length of the expanded tubular section is increased by pushing the unexpanded tubular section in axial direction relative to the expanded tubular section further into the borehole. For clarity of Figs. 5A-5B, the expanded tubular section and the unexpanded tubular section are not shown as such. In detailed view Fig. 5C, the expanded tubular section 202 and the unexpanded tubular section 204 are shown as comprised by the tubular section 200.

[0060] Fig. 5A shows the borehole 102 halfway lined with the tubular element 200, with a section of the borehole yet to be lined indicated with dashed line 102’. Fig. 5B shows the completed borehole 102, fully lined with the tubular element 200. In completed state, the borehole 102 may extend between an entry point 108 and an exit point 110. As such, through the borehole 102, in particular through the tubular element 200, one or more fluids and / or cables may be transported.

[0061] Fig. 5C shows a detailed view of the process of lining the borehole 102. Two subsequent situations in time are depicted. At a first instance in time, the tubular element is indicated with solid lines, and the location and shape of the tubular element at a second instance in time is indicated with dotted lines.

[0062] Between the first instance and second instance, the bending zone 206 has moved to a new location for the bending zone 206’. In particular, the bending zone 206 has moved by a distance d, and an additional distance d of expanded tubular section 202’ is formed. In order to form the distance d of expanded tubular section 202’, the unexpanded tubular section 204 has to be moved further into the borehole 102 for a distance 2d. This also forms an additional distance d of unexpanded tubular section 204’.

[0063] The fact that the unexpanded tubular section 204’ moves twice as fast than the expanded tubular section 204’ can be used as follows. Approximately when half of the length of the borehole 102 has been lined - as shown in Fig. 5A - it is possible to connect one or more elements to the unexpanded tubular section 204 at or near the entry point 108. As the rest of the borehole 102 is lined, these one or more elements move with the unexpanded tubular section 204 through the expanded tubular section 202 and end up at the exit point 110 of the borehole 102.

[0064] In an example, one or more cables and / or wires may be connected to move with the unexpanded tubular section 204 when the borehole 102 is halfway lined. The one or more cables and / or wires then end up at the exit point 108 after the entire borehole 102 has been lined with the expanded tubular section 202.

[0065] Figs. 6A and 6B show two offshore structures, for example two monopiles 300, 300’, which are positioned at a distance from each other. In the situation depicted in Fig. 6A, a tubular element 200 is being formed and passes through a first of the two monopiles 300 into the sedimentary bed 308 into which the monopiles 300, 300’ are positioned.

[0066] As an example, depicted in Figs. 6A and 6B, a scour hole 360 has formed adjacent the first monopile 300, for example to due to water movement around the first monopile 300. Preferably, for any method and structure disclosed herein, the tubular element 200 passes below the scour hole 360, to prevent the tubular element 200 from being directly exposed to the moving water. A minimum depth d of the tubular element 200 in the sediment bed 308 may 5 metres or more, 10 metres of more, or conceivably any other depth.

[0067] Between the situations depicted in Fig. 6A and Fig. 6B, the borehole 102 is extended towards the second monopile 300’, and the tubular element 200 passes into the second monopile 300’ at a bottom end of the second monopile 300’. Preferably, a subsection of the tubular element 200’” which is positioned outside the monopiles 300, 300’ is entirely embedded underground, in particular in the sediment bed 308, and is as such protected from the water movements in the body of water 301.

[0068] It will be appreciated that in general, for any offshore structure disclosed herein, more than one tubular element may pass through said offshore structure, for example through the passage passing through the support frame. For example, a first tubular element passing through a first offshore structure can extend towards a second offshore structure, while a second tubular element passing through the offshore structure can extend towards a third off shore structure. The first offshore structure can be generally positioned between the second offshore structure and the third offshore structure. Conceivably, as such, any number of offshore structures can be interconnected using tubular elements with a method according to the present disclosure.

[0069] Whenever one or more cables pass through any tubular element disclosed herein, for example cables for transporting electric energy, the tubular element can be used to protect the one or more cables from outside influences, such as impacts, water ingress, and / or water currents. Typically, to protect cables from one or more of these outside influences, armoured offshore cable is used, which is relatively expensive, stiff, and heavy, compared to for example unarmoured non-offshore cable. Whenever the tubular element surrounds a cable, there may no longer be a need for the offshore cables, and less expensive and / or heave cables can be advantageously used. This in particular applies in case the one or more cables can be laid through the tubular element when the tubular element extends from one offshore structure to another offshore structure, without the tubular element being directly exposed to currents in the body of water.

[0070] For positioning one or more cables for transporting electrical energy and / or telecommunication signals in the tubular element, the one or more cables may be connected to the unexpanded tubular section when the borehole is approximately at half of its ultimate length. In particular, the one or more cable may be connected to an outer wall of the unexpanded tubular section and / or an inner wall of the unexpanded tubular section.

[0071] Alternatively, or additionally, a temporary pulling member may be connected to move with the unexpanded tubular section when the borehole is approximately at half of its ultimate length, such that when the tubular element is entirely formed, the temporary pulling member may extend from the proximal end of the tubular element to the distal end of the tubular element. One or more cables can subsequently be connected to a proximal end or a distal end of the temporary pulling member, and by pulling the temporary pulling member out of the tubular element, the one or more cables are passed through the tubular element.

[0072] Although not depicted in figures 1-6B, the present disclosure contemplates a tubular element forming station, which can be temporarily connected to any structure disclosed herein, for example any monopile or jacket, for example disclosed in conjunction with any of the Figs. 2A-4B, 6A- 6B. The tubular element forming station can for example be positioned on a platform 312, or can generally be temporarily coupled at or neat a top side of the offshore structure.

[0073] The tubular element forming station may comprise a supply of material used to form the tubular element, for example to form additional length of the unexpanded section. A tubular element forming module of the tubular element forming station is arranged for forming the unexpanded tubular section from the supply of material, for example in a generally continuous forming process, for example using extrusion and / or injection moulding, or in a discontinuous process.

[0074] The tubular element forming station further comprises a moving module for moving the newly formed unexpanded tubular section further into the passage through the structure. When the tubular element forming station is releasably coupled to the offshore structure, the tubular element forming station can be removed and coupled to a further offshore structure after the tubular element, of which part extends through the offshore structure, has been formed. Between the offshore structure and the further offshore structure, the tubular element forming station can be transported using a ship or boat.

[0075] It will thus be understood that the present disclosure contemplates an assembly of an offshore structure and a tubular element forming station wherein the offshore structure is according to the third aspect, and the tubular element forming station is temporarily coupled to the offshore structure. The tubular element forming station is arranged for forming at least part of the tubular element, comprising an expanded tubular section connected to the support frame and an unexpanded tubular section, and the tubular element forming station is arranged for pushing the unexpanded tubular section into the passage through the structure.

[0076] Any off-shore structure disclosed herein, for example in the form of a monopile or jacket, may be permanently supported into or onto a sedimentary bed, such as a seabed - contrary to for example a jack-up vessel which is only temporarily supported onto a sedimentary bed. To be permanently supported into or onto a sedimentary bed thus implies that the structure remains in place over the course of months, years or even decades.

[0077] Figs. 7A-7C schematically depict an example of a method in which a single tubular element forming station 700 is used in conjunction with multiple off-shore structures 300, 300’, 300”. In Fig. 7 A, the tubular element forming station 700 is temporarily connected to a first off-shore structure 300, and used to form a first tubular element 200 which extends to a second offshore structure 300”. For any tubular element forming station 700, a slip joint may be used to form the temporary connection with the off-shore structure.

[0078] As an option step applicable for any tubular element forming station 700, in Fig. 7B with respect to Fig. 7A, the tubular element forming station 700 has been rotated along an essentially vertical axis. As such, a further tubular element 200 may be formed through the same off-shore structure 300, in particular to a third off-shore structure 300’, for example in another direction compared to the direction at which the first tubular element 200 extends from the first off-shore structure 300.

[0079] In Fig. 7C, the tubular element forming station 700 has been disconnected from the first off-shore structure 300 and has been temporarily connected to a fourth offshore structure 300’” through which no tubular element extends yet. As such, two tubular elements may be formed through this fourth offshore structure 300’”, of which one tubular element can for example extend to the first off-shore structure 300. Alternatively, although less preferred, the tubular element forming station 700 may be connected to an offshore structure through which already one or more tubular elements extend.

[0080] Features disclosed herein, for example in conjunction with Figs. 1- 6B or in the summary, may be generally applied to the method of Figs. 7A- 7C, for example relating to the tubular element, unexpanded tubular section, expanded tubular section, use of the tubular element, formation of the borehole, the drill, and / or any other feature, in any combination thereof.

[0081] In any method of the present disclosure, as an alternative to passing through the off-shore structure, at least part of or the entire tubular element may extend alongside the off-shore structure.

[0082] The methods and devices disclosed herein may also be used through hard formation, for example rock or shale.

Claims

Claims1. Method of forming a lined borehole, the method comprising steps of: radially expanding a tubular element in a borehole by bending an unexpanded tubular section of the tubular element radially outward and in axially reverse direction so as to form an expanded tubular section extending around the unexpanded tubular section, wherein the bending occurs in a bending zone; and increasing the length of the expanded tubular section by pushing the unexpanded tubular section in axial direction relative to the expanded tubular section further into the borehole, thereby lining the borehole with the expanded tubular section; wherein a majority of the borehole passes through soft formation, for example comprising sand, mud, clay, loam, and / or silt.

2. Method according to claim 1, wherein the borehole passes essentially entirely through soft formation.

3. Method according to claim 1 or 2, wherein at least part of the borehole has a substantially horizontal section.

4. Method according to any of the preceding claims, wherein more than 50% of the borehole is substantially horizontal.

5. Method according to any of the preceding claims, wherein the borehole enters the Earth’s surface at an entry point, and exits the Earth’s surface at an exit point at a distance from the entry point.

6. Method according to any of the preceding claims, further comprising positioning one or more cables for transporting electrical energy and / or telecommunication signals in the tubular element.

7. Method according to claim 6, wherein the one or more cables are connected to move with the unexpanded tubular section when the borehole is approximately at half of its ultimate length.

8. Method according to any of the preceding claims, further comprising removing the unexpanded tubular section from the borehole after the borehole is completed.

9. Method according to any of the preceding claims, wherein a maximum depth of the borehole does not exceed 500 metres, preferably does not exceed 200 metres.

10. Method according to any of the preceding claims, wherein the borehole enters the Earth’s surface at an entry point below a body of water, such as a lake, sea or ocean.

11. Method according to any of the preceding claims, wherein the borehole passes below a body of water subject to tidal influences.

12. Method according to any of the preceding claims, wherein the unexpanded tubular section is supplied from and / or anchored to a floating vessel or a vessel supported on the bottom of a body of water, such as a jackup vessel.

13. Method according to any of the preceding claims, wherein the unexpanded tubular section is supplied from and / or anchored to an off-shore structure, such as a monopile or a jacket.

14. Method according to claim 13, wherein the unexpanded tubular section passes through the off-shore structure.

15. Method according to claim 13 or 14, wherein the tubular element passes below scour protection of the off-shore structure.

16. Method according to claim 13 or 14, wherein the tubular element passes below a scour hole adjacent the off-shore structure.

17. Method according to any of the claims 13-16, wherein the tubular element enters a second off-shore structure after passing through the borehole.

18. Method according to any of the claims 13-17, wherein the unexpanded tubular section extends from the off-shore structure to a further off-shore structure.

19. Method according to any of the preceding claims, wherein the drill is a steerable drill, and the method comprises steering the drill to form a borehole with a pre-determined trajectory.

20. Method according to any of the preceding claims, wherein during forming of the expanded tubular section, the expanded tubular section has a larger diameter than a section of the borehole downstream of the bending zone.

21. Use of a lined borehole formed using a method according to any of the preceding claims for transporting CO2 through.

22. Use of a lined borehole formed using a method according to any of the claims 1-20 for transporting hydrogen gas through.

23. Use of a lined borehole formed using a method according to any of the claims 1-20 for transporting water, in particular salt water, through.

24. Structure to be used as an offshore structure, such as a monopile or jacket, the structure comprising: a support frame, arranged to be driven into or supported onto a sedimentary bed, such as a seabed, and arranged to support an offshore element such as a wind turbine; a passage passing through the support frame; and a tubular element, comprising an expanded tubular section connected to the support frame and an unexpanded tubular section arranged to be pushed into the passage, which expanded tubular section and unexpanded tubular section are connected via a bending zone.

25. Structure according to claim 24, wherein the passage runs from a top side of the support frame to a bottom side of the support frame.

26. Structure according to claim 24 or 25, wherein the structure is a monopile or a jacket.

27. Method according to any of the claims 13-18, wherein the off-shore structure is a monopile or a jacket.

28. Method according to any of the claims 13-20, wherein a tubular element forming station (700) is temporarily connected to the off-shore structure, and the tubular element forming station is used to form the tubular element (200).

29. Method according to claim 28, further temporarily connecting the tubular element forming station to a further off-shore structure.

30. Method according to claim 28, further comprising rotating the tubular element forming station relative to the off-shore structure, and using the tubular element forming station to form a further tubular element (200’).

Images