GB2511716A

GB2511716A - A sleeve for collecting contaminants

Info

Publication number: GB2511716A
Application number: GB1111674.6A
Authority: GB
Inventors: Michael Lawson
Original assignee: Individual
Current assignee: Individual
Priority date: 2011-07-08
Filing date: 2011-07-08
Publication date: 2014-09-17
Also published as: GB201111674D0

Abstract

A sleeve for collecting contaminants issued from a submarine source (eg. a submerged leakage or sunken oil tanker). The sleeve comprises a concertina section 10, allowing the length of the sleeve to vary with tidal motion and other changes in the height of the water level. Sections of the sleeve which receive contaminants are slidably mounted to lines 2 extended upwardly from anchoring elements 1 on the sea floor. Frame 8 acts to retain the bottom tube section 5 in a preferred shape. Concertina sections 10 and tube sections 5 may be coupled together by means of coupling sections 9 having cooperating interlocking features, such as Velcro. Tank 11 floats on the surface supported by bouys and may have gas pressure valves 13 and oil valves 16.

Description

A SLEEVE FOR COLLECTING CONTAMINANTS

Field of the Invention

The present invention relates to an apparatus for capturing contaminants released in a submarine environment. In particular, but not exclusively, the present invention relates to a sleeve for capturing oil leaks from a damaged wellhead.

Background to the Invention

Today, offshore drilling accounts for a large proportion of oil and gas production.

As these resources become scarcer, the incentive to drill in deeper water and in harsher environments increases, Despite significant resources invested to ensure the safety and reliability of these operations, no such process is without risk. When difficulties do arise, one consequence is often a leak from the wellhead on the sea floor.

The environmental and economic impact of an oil or gas leak of this kind can be immense. For example, during the Deepwater horizon oil spill in the Gulf of Mexico in 2010 it is estimated that 205.8 million gallons of oil was spilt into the surrounding area. The economic cost is not limited to the expense of the operation to clean up a spill of this magnitude but extends to the damage to local economies, such as fishing and tourism, that rely on the marine environment.

The environmental cost is self-evident and devastating.

Today, a range of techniques are used to try to mitigate these costs while a wellhead is repaired. These include skimming oil from the water's surface, the burning of oil on the surface, and attempts to manage the spread of oil slicks across the water. All these approaches fail to address the issue at source, waiting until the oil becomes apparent at the surface and thus until the scale of the problem is too large to be effectively dealt with.

An alternative approach is suggested in US patent US 4,531,860. In the system described in this document, a large flexible sleeve is provided with an opening which is submerged in a position above the wellhead. A pressurised ring is used retain the shape of the opening while the sleeve is anchored via anchor chains which extend from both its top and bottom corners, The upper end of the sleeve is prevented from sinking by being coupled to a tank which is pumped full of air.

In use, the opening of the sleeve is placed over a wellhead, and oil and gas escaping from the welihead is captured by the sleeve and passed through a range of pipes which extend from the sleeve through the tank to the surface, This can then be collected, preventing damage to the local environment.

There are a number of problems with the system described in US 4,531,860, not east of which is the difficulty in deploying a system of this type. The wellhead can be extremely deep (approximately iSOOm in the case of the Deepwater Horizon disaster) leading to significant difficulty in anchoring the upper and lower ends of the sleeve in the manner described in US 4,531,860. For example, the relative distance between the anchors attached to the upper and lower ends of the sleeve needs to be controlled to within a small tolerance if the sleeve is to take the desired shape. This is a non-trivial feat of anchor handling at any depth, let alone at depths of greater than 1,000m.

Moreover, in tidal conditions, or where there is variation in the depth of water for any reason, correct deployment of the sleeve is a moving target. The approach described in US 4,531,860 fails to take account of this and is subject to strains and tensions and conditions change, leading to unreliability.

Another flaw in the system of US 4,531,860 is the complexity of the design.

Given the necessarily huge scale of a system of this kind, this also has a negative impact on reliability, particularly as a result of the failure of interfaces between different elements. Thus, simplicity is a virtue and the complexity of the system of US 4531,860 is a weakness. For example, each of the interfaces between the various extraction pipes, the air tank, and the sleeve itself represent possible failure points.

Summary of the Invention

According to a first aspect of the present invention, there is provided a. sleeve for collecting contaminants being expelled from a sea floor, the sleeve comprising a concertina section of variable length.

The provision of a concertina section which is of variable length allows the effective length of the sleeve to vary. This can accommodate changes in the water level, due to ttdes for example, and thus ensure reliable collection of contaminants, such as oil, that may be issuing from a submarine source, such as a broken wellhead. The concertina section is typically substantially hollow, such that contaminants may pass therethrough, from the source to a position where they can be managed.

Preferably, the sleeve further comprises: one or more anchoring elements for disposal on the sea floor when in use; and one or more lines extending upwardly from the anchoring elements when in use, wherein the concertina section is slidably mounted to the one or more lines. This is an efficient, reliable and easy to operate method of securing the concertina section in place.

In preferred embodiments, stop clamps are disposed on the one or more lines at a predetermined distance from the anchoring elements. This ensures that a region next to the sea floor is substantially open, allowing access to the source of contaminants in order that it can be worked upon. For example, this allows robotic repair of a broken wellhead.

Preferably, the sleeve further comprises one or more tube sections, wherein the concertina section is arranged to receive contaminants that have passed through the one or more tube sections, In this manner, contaminants can initially be collected by relatively simple tube sections, and need not be secured in the first instance by a concertina section. Moreover, the concertina section need not extend the entire distance between the point at which it is desired to capture the contaminants and the point at which the contaminants are to be managed.

S Preferably, the one or mare tube sections are slidably mounted to one or more lines extending upwardly from anchoring elements disposed on the sea floor.

This is a simple and effective means of forming the sleeve including tube sections, allowing flexibility in their exact mounting positions.

In preferred embodiment. the sleeve further comprises a tank for receiving contaminants that have passed through the concertina sleeve. Preferably, the tank is slidably mounted to one or more lines extending upwardly from anchoring elements disposed on the sea floor. In this way, a tank that collects the contaminants can be provided upstream of the concertina section.

Preferably, the tank comprises a gas release valve. For example, the gas release valve may be arranged to release gas when the pressure in the tank reaches a predetermined level. Alternatively or additionally, the tank may comprise an oil release valve. The oil release valve may be arranged to prevent the flow of oil when an extraction pipe is not connected to the oil release valve.

In preferred embodiments, the concertina section is resiliently biased to a predetermined length. This means that the concertina section returns to a predetermined length after being stretched or compressed, ensuring the overall structure of the sleeve is resilient.

According to a second aspect of the present invention, there is provided a method of collecting containments being issued from submarine source, comprising: placing a sleeve over the source, the sleeve comprising a concertina section of variable length.

Preferred features of the first aspect may equally be applied to the second aspect.

According to a third aspect of the present invention, there is provided a sleeve comprising one or more anchoring elements for disposal on the sea floor; one or more tines extending upwardly from the anchoring elements when in use, and one or more sections for receiving contaminants from the sea floor which are slidably mounted to the lines.

Mounting sections slidably to the lines provides an efficient and reliable method of constructing a sleeve. The sections may be, for example, concertina sections, tube sections or tanks. Preferred features of the first embodiment may apply equally to the second embodiment. The invention also extends to a method of using the third aspect to collect contaminants being issued from a submarine source.

Brief Description of the figures

A preferred embodiment of the present invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 shows a side view of a sleeve according to the preferred embodiment; Figure 2 shows a side view of the lower haff of the sleeve of Figure 1; Figure 3 shows a side view of the upper half of the sleeve of Figure 1; and Figure 4 shows further detail of a double clip for use with the preferred embodiment.

Detailed Description

A sleeve according to a preferred embodiment of the present invention is shown from the side in Figure 1. The sleeve has an approximately square profile from above, and is symmetrical such that the side view of any face would be approximately the same. Figures 2 and 3 show the lower and upper half of the sleeve in more detail respectively.

The sleeve comprises using weights 1 which are disposed at each corner. The weights 1 act as anchoring elements, securing the sleeve to the sea floor. As mentioned above, the profile of the preferred embodiment is approximately square from above, Thus there are four weights 1 disposed on the sea floor. In place of weights, other type of anchoring elements may be used, such as anchors which engage with the sea floor physically.

The sleeve further comprises cables 2 extending upwards from the weights 1.

The cables 2 are suspended at a top end so that they extend substantially vertically. Although the preferred embodiment uses cables 2, the skilled person will appreciate that any type of line may be used in place of cables, such as chains, ropes or wires. A line in this context may be considered as any linearly extending flexible member.

A number of rigid spacers 3 are provided to maintain the appropriate separation between the weights 1. The spacers 3 may be formed of steel or another suitable rigid material. The spacers 3 are coupled to the weights 1, and in the preferred embodiment are coupled to the weights 1 at the same coupling point as the cables 2 are coupled to the weights 1.

So, in the preferred embodiment the weights 1 form the corners of a square profile on the sea floor while the spacers 3 form the sides between these corners. This is a rigid and secure shape which benefits from relative simplicity.

However, it is recognised that alternative arrangements may be used. For example, a substantially triangular profile may be achieved using three weight 1 with three spacers 3 disposed between them, In other examples more complex profiles may be adopted. In general, preferred embodiments of the sleeve comprise at least three weights 1.

As mentioned previously, the cables 2 extend upwardly from the weights 1 to the surface of the water. At a predetermined distance along the cables 2 in this direction, i.e. at a predetermined distance from the end of the cables 2 that are secured to the weights 1, stop clamps 4 are provided on each cable 2. The stop clamps 4 may be any mechanism that inhibits passage of a feature couples to the cable 2 from one side of the clamp 4 to the other. In one simple example.

the stop clamps 4 are physically protruding members which protrude outwardly from the cable 2. These may be permanently or adjustably mounted to the cable 2 by any appropriate mechanism, such as clamping.

The sleeve further comprises one or more tube sections 5. The length of the tube sections 5 may be chosen as appropriate, for example as 500 metres, 200 metres, 100 metres, 50 metres, 20 metres or 10 metres, Where a plurality of tube sections 5 are used they may have the same or different lengths. The tube sections 5 are mounted to the cables 2 using double clips 6. The double clips 6 will be described in more detail with reference to Figure 4 below. The double clips 6 are coupled to the tube sections 5 via loops 7 (best seen in Figure 2) provided at intervals along the sides of the tube sections 5. In preferred embodiments, the intervals are regular, and may be around 10 metres. In Figure 2, the tube sections 5 are shown in a separated configuration as they might be before the sleeve has been fully deployed.

The double clips 6 are slidably mounted on to the cables 2. The clamp stops 4 on the cables prevent the double clips 6, and thus the tube sections 5, from coming within a certain distance from the weights 1. There is provided on the bottom end of the lowest tube section 5 a frame 8, which acts to retain the bottom end of the tube in a preferred profile and to weight the lowest tube section 5 down towards the clamp stops 4, The frame may be formed of steel or any other suitable material, particularly materials that are substantially rigid and have a greater density than sea water.

The ends of each tube section 5 has a coupling section 9, which may, for example, be formed of a two foot (approximately 60cm) wide layer of Velcro.

The coupling section 9 of a tube section 5 may engage with a coupling section 9 of adjacent features. For example, if the coupling section 9 is a two foot (approximately 60cm) wide layer of Velcro disposed on the outer surface of a first tube section 5, this may engage with a corresponding layer of Velcro on the inner surface of a second tube section 5. In this manner, each tube section 5 may be coupled together using the Velcro 9 and coupled to the cables 2 using the double clips 6.

The sleeve further comprises a concertina section 10. This is secured to an adjacent tube section 5 using a coupling section 9 and coupling part as described above. For example, Velcro may be used to secure the concertina section 10 to the adjacent tube section 5. The concertina section 10 comprises loops 7 similar to the tube sections 5 in order to allow it to be slidably coupled to the cables 2 using double clips 6. The concertina section 10 is flexible and may expand and contract in a vertical direction. For example, in some preferred embodiments, the concertina section 10 may have a vertical length which varies by an amount between 1 and 8 metres. Each part of the concertina section 10 may contain a number of flat steel bars in order to create a spring effect. This spring effect may resiliently bias the concertina section 10 towards a preferred position, ensuring that the coherence of the structure of the sleeve can be maintained.

A tank or sump 11 is provided coupled to an upper end of the concertina section 10 via a seam 17. Details of the tank 11 are best viewed in Figure 3.

The tank 11 floats on the surface of the water and is supported by buoys or floats (not shown), suspension cables 15 extending from each upper corner, and, via double clips 6, the cables 2 that extend to the sea floor, It will be appreciated that alternative methods of maintaining the tank 11 in position may be adopted as appropriate, and that, for example, it some circumstances the use of either buoys/floats or extension cables 15, instead of both as in the preferred embodiment, may be considered.

The tank 11 has an opening on its bottom surface and is secured to the concertina section 10 by means of a seam 17. For example, the tank 11 may be bolted to the concertina section 10 at the seam 17. In particular, the concertina section 10 may be secured to the base of the tank in the following way: a first rubber strip is disposed around the base of the tank; the top of the concertina section 10 is disposed around the first rubber strip; a second rubber strip is disposed around the top of the concertina section 10; a rigid bar, made for example of steel, is disposed on top of the second rubber strip; and these layers are then bolted together and onto the base of the tank 11 through parallel holes provided in each layer.

The tank ills preferably formed of a rigid, durable material, such as a metal. In the preferred embodiment, the tank ii is formed of steel. In the preferred embodiment, the tank 11 has a capacity of 64 cubic metres, although the size of the tank 11 can be varied according to requirements.

The tank comprises an oil depth gauge 12 which includes a floating section which floats on liquid within the tank 11 and an indicator which extends through the upper surface of the tank. The amount of liquid within the tank can be gauged by visual inspection of the proportion of the indicator which extends through the upper surface of the tank ii.

The tank ii further comprises a gas pressure valve 13. In the preferred embodiment, the gas pressure valve 13 is provided at or near the top of the tank ii. The gas pressure valve 13 is arranged to release gas from within the tank ii once the pressure within the tank ii reaches a predetermined value. If desired, a pipe can be coupled to the gas pressure valve 13 to harness gas that is released in this way.

Welded rings 14 are provided on an upper surface of the tank 11. The welded rings 14 can be used to launch the tank 11 and stabilise it against vertical motion. As part of these benefits or in addition, the welded rings 14 can be coupled to the suspension cable 15 which can keep the tank 11 in a fixed position and depth within the water and add extra security to the sleeve in general.

The tank 11 further comprises an oil valve 16 placed near the bottom of the tank 11. The oil valve 16 allows oil in the tank 11 to be removed when an oil pipe is engaged with the outer part of the oil valve 16. In the preferred embodiment, when the oil pipe is removed from the oil valve 16, the oil valve 16 automatically stops the flow of oil.

As mentioned above, Figure 4 shows an exemplary double clip 6 in more detail.

As can be seen from Figure 4, the double clip 6 forms of figure of eight type profile, comprising two through holes. The perimeter of each through hole includes a rotatably mounted opening portion, the movement of which is indicated by the arrows in Figure 4. The double clip 6 can be mounted to features, such as the cables 2, by opening the rotatably mounted opening portion, placing the feature in the associated through hole, and the then closing the opening portion. In the preferred embodiment! the opening portions of the double clips 6 are disposed on sides of the double clip which are substantially parallel. This provides a secure connection under tension.

In use, the sleeve of the preferred embodiment may be operated as follows.

Firstly, the weights 1 connected to cables 2 are lowered to the sea floor around a broken wellhead or other source of contamination, The tube sections 5, concertina section 101 and tank 11 are then towered in that order along the cables 2 to which there are secured using double clips 6. The sleeve is thus formed with relative ease.

Once the sleeve is in place, oil, gas or other contaminants being released from the well head or other source are released firstly into the lowest tube section 5, these then pass through the tube sections 5, through the concertina section 10, and into the tank 11. From here, gas can be released from the gas pressure valve 13 while liquid such as oil can be released from the oil valve 16. Thus the so sleeve captures oil, gas and other contaminants being discharged from the sea floor in a secure and reliable manner.

During use, there may be changes in the sea level due to tidal or wave effects, or due to large volumes of contaminants being released. The flexibility of the concertina section 10 allows the sleeve to adjust for these effects without subjecting excessive tension to the rest of the sleeve. Moreover, because the concertina sleeve 10 is flexible in this way, an increase in the sea level will not cause the lowest tube section 5 to move away from the broken well head. Thus, the sleeve can reliably capture contaminants regardless of such effects.

The use of the stop clamps 4 means that the sleeve does not drop all the way to the sea floor during use. This can be advantageous, allowing, for example, robotic attempts to repair a broken well head.

Variations and modifications will be apparent to the skilled person. Such variations and modifications may involve equivalent and other features which are already known and which may be used instead of, or in addition to, features described herein. Features that are described in the context of separate embodiments may be provided in combination in a single embodiment.

Conversely, features which are described in the context of a single embodiment may also be provided separately or in any suitable sub-combination.

It should be noted that the term "comprising" does not exclude other elements or steps, the term a" or "an" does not exclude a plurality, a single feature may fulfil the functions of several features recited in the claims and reference signs ri the claims shall not be construed as limiting the scope of the claims, It should also be noted that the Figures are not necessarily to scale; emphasis instead generally being placed upon illustrating the principles of the present invention.

Claims

Claims 1, A sleeve for collecting contaminants being expelled from a sea floor, the sleeve comprising a concertina section of variable length.
2. A sleeve according to claim 1, further comprising: one or more anchoring elements for disposal on the sea floor when in use; and one or more lines extending upwardly from the anchoring elements when in use, wherein the concertina section is slidably mounted to the one or more lines.
3. A sleeve according to claim 2, wherein stop clamps are disposed on the one or more lines at a predetermined distance from the anchoring elements.
4. A sleeve according to any one of the preceding claims, further comprising one or more tube sections, wherein the concertina section is arranged to receive contaminants that have passed through the one or more tube sections.
& A sleeve according to claim 4, wherein the one or more tube sections are slidably mounted to one or more lines extending upwardly from anchoring elements disposed on the sea floor.
6. A sleeve according to any one of the preceding claims, further comprising a tank for receiving contaminants that have passed through the concertina sleeve.
7. A sleeve according to claim 6, wherein the tank is slidably mounted to one or more lines extending upwardly from anchoring elements disposed on the sea floor.
8. A sleeve according to claim 6 or claim 7, wherein the tank comprises a gas ref ease valve.
9, A sleeve according to any one of claim 6 to 8, wherein the tank comprises an oil release valve.
10. A sleeve according to any one of the preceding claims, wherein the concertina section is resiliently biased to a predetermined length.
11. A method of collecting containments being issued from a submarine source, comprising: placing a sleeve over the source, the sleeve comprising a concertina section of variable length.IS
12. A sleeve for collecting contaminants being expelled from a sea floor comprising: one or more anchoring elements for disposal on the sea floor; one or more lines extending upwardly from the anchoring elements when in use, and one or more sections for receiving contaminants from the sea floor which are slidably mounted to the lines.