Method of installing pin piles into a seabed

Abstract

A method of installing a plurality of pin piles into a seabed including at least the steps of: (a) lowering a pin pile apparatus comprising a first pin pile and an attached clump weight towards the seabed; (b) allowing the first pin pile to self-penetrate the seabed based on self-weight of the pin pile apparatus and the momentum from step (a) until the clump weight reaches the sea bed; (c) disconnecting the clump weight from the first pin pile; and (d) recovering the clump weight for use with a second pin pile and repeating steps (a)-(c). In this way, the pin piles are easily installed from their descent to the seabed with the clump weight, which can then be removed and applied to the next pin pile in an easy and repeatable operation without requiring a suction apparatus or hammer or drill.

Claims

1. A method of installing a plurality of pin piles into a seabed comprising at least the steps of: (a) lowering a pin pile apparatus comprising a first pin pile and an attached clump weight towards the seabed, wherein a momentum is generated by the lowering step; (b) allowing the first pin pile to self-penetrate the seabed based on self-weight of the pin pile apparatus and the momentum from step (a) until the clump weight reaches the sea bed; (c) disconnecting the clump weight from the first pin pile; and (d) recovering the clump weight for use with a second pin pile and repeating steps (a)-(c).

2. A method as claimed in claim 1 wherein the pin pile apparatus is lowered towards the sea bed based on one or more winches and gravity.

3. A method as claimed in claim 1 wherein the clump weight is recovered to a sea surface prior to repeating steps (a)-(c).

4. A method as claimed in claim 1 wherein the clump weight is attached to the pin pile comprising a collar and one or more lateral bolts, and wherein step (c) comprises moving the one or more bolts from an attachment position to a release position.

5. A method of providing pipeline route curve stability for a pipeline on or near a seabed comprising at least the steps of: (i) installing a plurality of pin piles using the method as described in claim 1 along the defined route; and (ii) connecting the pipeline to the pin piles.

6. A method of providing a mudmat on a seabed comprising at least the steps of: (i) providing a mudmat on the seabed; and (ii) installing a plurality of pin piles using the method as described in claim 1 through the mudmat.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the present invention will now be described by way of example only and with reference to the accompanying drawings in which

(2) FIG. 1 is a schematic side view of a first step in a method of installing a plurality of pin piles into a seabed according to one embodiment of the present invention;

(3) FIGS. 2-4 are schematic side views of subsequent steps in the method of FIG. 1;

(4) FIG. 5 is schematic perspective view of a pin pile apparatus according to another embodiment of the present invention; and

(5) FIG. 6 is perspective schematic view of a plurality of installed pin piles on a seabed, and a pipeline thereinbetween.

DESCRIPTION OF PREFERRED EMBODIMENTS

(6) Referring to the drawings, FIG. 1 shows an installation vessel 10 on a sea surface 12 having a winch 14 from which extends a winch line 16.

(7) FIG. 1 also shows a pin pile apparatus 20, is shown in more detail in FIG. 5.

(8) FIG. 5 shows the pin pile apparatus 20 comprising a pin pile 22 and separable clump weight 24. The pin pile 22 is approximately 3 m in length and generally cylindrical. It is generally formed from a steel, concrete, or combinations of metals and concrete.

(9) The clump weight 24 may be formed from concrete, or a concrete based material, or steel, and has a central bore to allow passage of the shape of the pile pin 22 therethrough. Upstanding from the top surface of the clump weight 24 is a hollow collar 28 having the same inner diameter as the bore 26 and being co-axial therewith. In the collar 28 is at least one aperture 30 into and through which a complementary bolt or pin 32 can be inserted for lateral movement through the collar 28.

(10) The aperture 30 may be directly formed in the collar 28, or formed in one or more housings (not shown) fitted within the collar 28. Optionally, the inner surface of the aperture 30 has a complementary shape to a fastening surface of the pin 32, such that the pin 32 can be tightened as it moves laterally inwardly through the collar 28.

(11) In use, the pin pile 22 is located within the bore 26 and collar 28 such that it extends from the lower surface of the clump weight 24 by the desired installation depth of the pin pile 22. The one or more pins 32 can then be moved from a disengaged position, optionally separate from the collar 28, to an attachment position, wherein the ends of the pins 32 engage the surface of the pin pile 22 and attach the pin pile 22 to the clump weight 24, optionally based on tightening or other constriction thereinbetween.

(12) As shown in FIG. 1, the pin pile arrangement 20 can then be attached to the winch line 16. Preferably, the winch line 16 is only connected to the clump weight 24 via one or more suitable attachment points and devices (not shown) able to provide the desired controlled lowering of the pin pile apparatus 20 from the sea surface 12 to a seabed 40.

(13) FIG. 2 shows the step of the pin pile 22 penetrating the seabed 40 based on its own self-weight and its momentum from the lowering of the pin pile apparatus 20 as shown in FIG. 1, until the clump weight 24 reaches the seabed 40. In this way, the installer is ensured of the correct and desired installation of the pin pile 22 into the seabed, whilst not having to provide any additional installation apparatus, units or devices, such as hammers or suction apparatus.

(14) FIG. 3 shows the step of an ROV 42 having an arm 44 able to reach the pin 32 and move the pin 32 from an attachment position to a release position, optionally being separable from the collar 28. In this way, the clump weight is then disconnected from the pin pile 22, i.e. detached therefrom and able to move independently.

(15) FIG. 4 shows the step of recovering the clump weight 24 for use with a second pin pile (not shown). The clump weight 24 can simply be recovered by the winch 14 lifting the clump weight 24 back on to the installation vessel 10. Once the second pin pile is attached to the clump weight 24, the operational steps shown in FIGS. 1-3 can be repeated to install the second pin pile, and so forth repeatedly.

(16) As shown by the steps of FIGS. 1-4, a plurality of pin piles can be installed into a seabed in a rapid and easy manner, using the same methodology to install each pin pile, and involving the single lowering of the pin pile apparatus and the single recovery step of the clump weight in a repeatable manner.

(17) FIG. 6 shows a representative area 50 of a seabed having a plurality of pin piles 52 installed thereacross along an unstraight route, so as to provide control of the direction of a pipeline 54 connected thereto, i.e. pipeline route curve stability therealong. This is useful for seabed developments where there may be significant geohazards close to or surrounding the area 50 which have an impact on the selection of the route of a new pipeline thereacross. Conventionally, the practice is to make large deviations in the pipeline route to avoid crossing such geohazards. The use of a number of pin piles for route curve stability and/or pipeline hold backs, enables the pipeline installer to have better control during the pipeline lay, and therefore be in a position to more gently route around and through geohazards, allowing the selection of more direct, shorter economically attractive routes.

(18) Where soil conditions of the seabed permit, and initiation loads are less than 10 tonnes pin piles, in particular, where the pin piles have a fin or cruciform arrangement, installed pin piles could be used as the starting point of laying small products like umbilical and flexible pipelines on to the seabed. This can also be termed initiation, where the product end is held back by a fixed point.

(19) The use of a reusable clump weight and relatively small pin piles may also offer significant savings and deck space on an installation vessel or accompanying barge, over the use of conventional clump weights as turning points. This is particularly where there are a number of turning points to install and transit to the site of use is significantly long.

(20) Incorporation of pin piles as part of a PLEN/PLET mudmat could also increase the lateral resistance of the mudmat foundation by approximately 10% to 20%, depending on soil conditions and pile size. By using pin piles, the mudmat size could therefor be reduced and/or optimized, and would therefor help with the deployment of mudmat through vessel moon pools during pipe lay.

(21) Various modifications and variations to the described embodiments of the invention will be apparent to those skilled in the art without departing from the scope of the invention as defined herein. Although the invention has been described in connection with specific preferred embodiments it should be understood that the invention as defined herein should not be unduly limited to such specific embodiments.