The present invention a method of installing an anchoring system, preferably within a borehole prefilled with settable material.

BACKGROUND OF INVENTION

A variety of anchoring systems are known in the art, such as driven piles, suction piles, and drag embedment. Such systems have however been found to suffer from several disadvantages. Commonly used anchoring systems are, typically, limited for use with specific seabed soil types, and/or have high associated cost and time implications.

For Floating Offshore Wind (FOW) projects, the geological conditions can vary greatly across a single site. As a result, conventional anchoring systems may not be suitable for use across the whole of the site. Furthermore, FOW projects require a large number of anchor foundations and as such there are high associated costs for using conventional anchoring systems.

Conventional anchoring systems include a tether, for example mooring line, extending from the anchor pile. Once embedded within a borehole, the tether is subjected to significant lateral loading. As a result, over time, the tether cuts through the soil structure adjacent to the upper end of the anchor. This cutting action can cause damage to the tether and can also cause the tether to slacken resulting in a less reliable anchoring system over time.

It is among the objectives of embodiments of the present invention to obviate or alleviate these and other disadvantages of known anchor piling systems.

SUMMARY OF INVENTION

According to a first aspect of the present invention, there is provided a method for installing an off-shore anchoring system comprising: drilling a borehole in a seabed, the borehole comprising a first lower portion in communication with a second upper portion, in which the cross-sectional dimensions of the first lower portion are smaller than the cross-sectional dimensions of the second upper portion, and in which an inwardly protruding abutment surface is provided at a transition point located therebetween; introducing settable locking media into the borehole; and subsequently introducing an off-shore anchoring system comprising an anchor pile and a lateral load transition member into the settable locking media within the borehole, such that the anchor pile is located within the first lower portion of the borehole, and the lateral load transition member is located within the second upper portion of the borehole and spaced apart from the anchor pile.

The method of the present invention provides a simple, reliable installation methodology.

The borehole is preferably a stepped profiled. The first lower portion may for example be drilled quickly and efficiently due to having reduced cross-sectional dimensions. The second upper portion, preferably having greater cross-sectional dimensions than the first lower portion, preferably provides for a larger contact surface area (compared to the first lower portion) to improve the transmission of lateral loads from the lateral load transition member into the surrounding borehole wall portions of the second upper portion and thereby creating improved lateral resistance to penetration of the borehole wall portions. The second upper portion is preferably configured to have greater cross-sectional dimensions in order to facilitate receiving of additional mechanical equipment, for example to connect mooring lines to the lateral load transition member.

The second elongate body of the lateral load transition member preferably comprises side portions, extending between the upper and lower ends thereof. The method preferably further comprises abutting surrounding wall portions of the second upper portion of the borehole with the side portions of the lateral load transition member to create hoop stress, when subjected to loading, within the second upper portion of the borehole wall without penetration thereof.

In one embodiment, the lateral load transition member is positioned such that the lower end thereof is spaced apart from the inwardly protruding abutment surface. As such, a flow-by area (for example an area configured to enable fluid flow therethrough) is provided between the lower end of the lateral load transition member and the inwardly protruding abutment surface. In one embodiment, the lower end of the lateral load transition member abuts the inwardly protruding abutment surface provided at the transition point between the upper and lower portions of the borehole.

The settable locking media may be introduced into and located within the first lower portion of the borehole. The settable locking media may be located within the first lower portion of the borehole and may not extend beyond the transition point between the first and second portions of the borehole. Such an arrangement provides for free movement of for example at least one connectors and/or mooring tethers in communication with the upper end of the lateral load transition member.

The settable locking media may be introduced into and located within the first lower portion and second upper portion of the borehole. The settable locking media may be introduced into the borehole so as to extend from a lower end of the first lower portion, beyond the transition point into the second upper portion. For example, in one embodiment, the locking media may be introduced into the borehole to extend from the first lower portion into the second upper portion of the borehole in order to secure at least a portion of the lateral load transition member in position within the upper portion of the borehole.

Preferably, the locking media is introduced into the borehole to not extend beyond the upper end of the lateral load transition member.

The settable locking media may be introduced to extend and towards, for example adjacent, an upper end of the second upper portion of the borehole. The settable locking media may be introduced into the borehole to substantially fill the first lower and second upper portion of the borehole.

The locking media may for example comprise cement or grout.

The method of the present invention can be used to reliably and effectively install an anchor to provide a taut mooring solution with reduced risk of damage and/or failure of the tether over time. The method of the present invention may be compatible for use with a wide range of geological formations.

The method of the present invention may be used to install an anchoring system capable of resisting high loads, for example in excess of 1000 tonnes.

The method of the present invention may be used to install an anchoring system of the present invention for resisting high angle mooring through to vertically loaded tension leg systems.

The method of the present invention may be used to install an onshore or offshore anchoring system. Preferably, the method of the present invention is used to install an offshore anchoring system.

The anchor pile preferably comprises a first elongate body having an upper end and a lower end.

The lateral load transition member preferably comprises a second elongate body having an upper end configured in use to be in communication with a laterally loaded mooring tether, and an opposed lower end positioned adjacent and spaced apart from the upper end of the first elongate body of the anchor pile. Side portions preferably extend between the upper and lower ends thereof. Preferably, the cross-sectional dimensions of the second elongate body of the lateral load transition member are greater than the cross-sectional dimensions of the first elongate body of the anchor pile.

The anchoring system preferably further comprises an intermediate portion connecting the lower end of the second elongate body of the lateral load transition member to the upper end of the first elongate body of the anchor pile. The intermediate portion is preferably rigid. The intermediate portion preferably comprises an elongate tensile member, for example a wire or tubing. The intermediate portion is preferably free from contact with the borehole wall portions. The cross-sectional dimensions of the intermediate portion are preferably less than the cross-sectional dimensions of the first and second elongate bodies. The second elongate body of the lateral load transition member is preferably continuous and does not define or provide any fluid pathway extending therethrough.

The lateral load transition member is configured to remove the lateral forces of the loading from a tether, for example mooring tether (i.e. to transmit the lateral forces of the loading into the surrounding borehole wall portions). In one embodiment, the method comprises positioning the lateral load transition member within the second upper portion of the borehole at a location which has sufficient lateral resistance to prevent penetration of the borehole wall portions by the lateral load transition member. Preferably, the method comprises positioning the lateral load transition member at the highest point within the borehole at which the lateral load transition member will remain stable (i.e. will not penetrate the borehole wall).

The second upper portion of the borehole is preferably dimensioned to provide a tight fit with the second elongate body of the lateral load transition member in order to provide, in use, increased frictional resistance and/or to effectively transmit lateral forces to create hoop stress within adjacent portions of the borehole.

The side portions of the second elongate body of the lateral load transition member may comprise ribbed portions. The ribbed portions may each define a longitudinal axis. The longitudinal axes of the ribbed portions may be aligned with, and spaced apart from, each other. The ribbed portions preferably extend substantially parallel to a longitudinal axis of the second elongate body of the lateral load transition member.

In one embodiment, the lower end of the second elongate body of the lateral load transition member is tapered. For example, the lower end of the lateral load transition member may be cone shaped.

The method may further comprise positioning the second elongate body of the lateral load transition member such that the lower end (for example tapered lower end) of the second elongate body extends into the first lower portion of the borehole, for example beyond the abutment surface provided between the first and second portions of the borehole.

The method may further comprising providing a first lower portion of the borehole having a cross-sectional dimension of at least 300 mm, preferably about 310 mm. The method may further comprising providing a first lower portion of the borehole having a cross-sectional dimension of no more than 500 mm, preferably no more than 450 mm. The method may further comprising providing a first lower portion of the borehole having a cross-sectional dimension of between 300 mm and 500 mm, and preferably between 310 mm and 450 mm.

The second upper portion of the borehole may have a cross-sectional dimension which is at least 10%, preferably at least 20%, preferably at least 30% greater than the cross-sectional dimension of the first lower portion. The second upper portion may for example have a cross- sectional dimension which is 100% greater than the cross-sectional dimension of the first lower portion.

The method may comprise installing the anchor pile at a depth within the bore hole adjacent high strength geological formations to provide for increased resistance. For example, the method may comprise installing the anchor pile at a depth of at least 50 m below the surface of the seabed. Preferably, the method comprises installing the anchor pile at a depth of between 50 m and 80 m below the surface of the seabed. The method preferably comprises installing the anchor pile such that the anchor pile is configured to receive the vertical loading from a mooring.

The method may further comprise attaching a tetherto the upper end of the second elongate body of the lateral load transition member. The method may further comprise attaching a first end of a tetherto the upper end of the second elongate body of the lateral load transition member, and a second opposed end of a tether to a tether termination. The tether termination is preferably configured to be a connection point for a main mooring line. The tether is preferably flexible. The tether may be enclosed within a protective outer layer to protect the tether from frictional forces arising as a result of lateral loading forces from the main mooring line causing the tether to move (or cut) through the surrounding geological formation. The second elongate body of the lateral load transition member is preferably shaped, dimensioned and located within the second upper portion of the borehole to reduce and preferably remove the lateral forces from the tether.

In one embodiment, the method further comprises abutting (for example embedding) the side portions of the second elongate body of the lateral load transition member against surrounding wall portions of the second upper portion of the borehole.

BRIEF DESCRIPTION OF FIGURES

Figure 1 is a schematic illustration of an anchoring system being inserted into a borehole according to one embodiment of the present invention;

Figure 2 is a schematic illustration of a view from below of an anchor system being inserted into a borehole, and subsequently in use, according to the embodiment of Figure 1; and

Figure 3 is a schematic illustration of a view from above of an anchor system being inserted into a borehole, and subsequently in use, according to the embodiment of Figure 1.

DETAILED DESCRIPTION

With reference to the Figures, the off-shore anchoring system 1 comprises an anchor pile 2, an intermediate portion 3 and a lateral transition assembly 4.

The anchor pile 2 comprises a first elongate body 6 having an upper end 7 and a lower end 8.

The lateral load transition member 4 is spaced apart, by the intermediate portion 3, from the upper end 7 of the first elongate body 6 of the anchor pile 2.

The lateral load transition member 4 comprises a second elongate body 9 having an upper end 10 configured in use to be in communication with a laterally loaded mooring tether 12, and an opposed lower end 11. The second elongate body 9 is substantially cylindrical in shape.

The tether 12 has a first end connectable to the upper end 10 of the second elongate body 9 of the lateral load transition member 4, and a second opposed end 13 for connection to a tether termination (not shown) which may for example be a connection point for a main mooring line. The tether 12 is flexible and may be enclosed within a protective outer layer to protect the tether 12 from frictional forces arising as a result of lateral loading forces from the main mooring line causing the tether to move (or cut) through the surrounding geological formation.

The intermediate portion 3 connects the lower end 11 of the second elongate body 9 of the lateral load transition member 4 to the upper end 7 of the first elongate body 6 of the anchor pile 2. The intermediate portion 3 is rigid and provides the spacing between the upper end 7 of the first elongate body 6 of the anchor pile 2 and lower end 11 of the second elongate body 9 of the lateral load transition member 4.

The offshore anchoring system 1 is installed by drilling a borehole 5 in a seabed. The borehole 5 comprises a first lower portion 14 in communication with a second upper portion 15. The cross-sectional dimensions of the first lower portion 14 are smaller than the cross-sectional dimensions of the second upper portion 15. An inwardly protruding abutment surface 16 is provided at a transition point located therebetween.

Settable locking media is introduced into the borehole 5. The settable locking media is introduced into the first lower portion 14 to extend from the lower end 17 thereof towards (preferably up to) the transition point.

The anchor pile 2 is then introduced into the borehole 5. The anchor pile 2 is received within the first lower portion 14 of the borehole 5 containing the settable locking media. The anchoring system 1 continues to be introduced so that the lateral load transition member 4 is introduced into the second upper portion 15. The lateral load transition member 4 is positioned within the second upper portion 15 of the borehole 5 and abuts the inwardly protruding abutment surface 16 provided at the transition point. The cross-sectional dimensions of the second elongate body 9 of the lateral load transition member 4 are greater than the cross-sectional dimensions of the first elongate body 6 of the anchor pile 2. The cross-sectional dimensions of the second elongate body 9 are slightly smaller than the cross-section dimensions of the upper portion 15 of the borehole 5 to ensure a tight fit to enable efficient transmission of lateral forces from the lateral load transition member 6 into the surrounding portions of the borehole.

The second elongate body 9 of the lateral load transition member 4 comprises side portions 18 extending between the upper and lower ends 10, 11 thereof, configured in use to abut surrounding wall portions of the second upper portion 15 of the borehole 5 to create, in use, hoop stress within the second upper portion 15 of the borehole wall 5 without penetration thereof.

The method of the present invention provides a simple, reliable installation methodology.

The anchoring system of the present invention can be used to effectively and reliably anchor a tether, for example mooring line, to provide a taut mooring solution over time. The anchoring system of the present invention may be compatible with a wide range of geological formations.

The lateral load transition member is located to resist the lateral forces of the loading from a mooring and to transmit the lateral forces of the loading into the surrounding borehole wall portions. In one embodiment, the lateral load transition member is configured to be positioned within the second upper portion of the borehole at a location which has sufficient lateral resistance to prevent penetration of the borehole wall portions by the lateral load transition member. Preferably, the lateral load transition member is configured to be positioned at the highest point within the borehole at which the lateral load transition member will remain stable (i.e. will not penetrate the borehole wall).

The anchoring system of the present invention may be capable of resisting high loads, for example in excess of 1000 tonnes. The anchoring system of the present invention may be used for resisting high angle mooring through to vertically loaded tension leg systems.

The anchoring system of the present invention enables the lateral forces exerted by the tether to be resisted and transmitted directly into the geological surfaces surrounding the borehole. As a result, the anchoring system of the present invention reduces the forces exerted on the tether, thereby reducing the cutting motion of the tether through the geological surfaces which occurs with conventional anchoring systems. The anchoring system of the present invention therefore reduces the length of tether required and thereby reduces the cost of materials, reduces the potential for damage to occur to the tether as a result of the cutting motion and therefore reduces labour and costs associated with repair and/or replacement of the tether overtime. The anchoring system of the present invention reduces the risk of failure of the anchor pile as a result of damage to the tether and thereby provides a more reliable anchoring system.