GB2481125A

GB2481125A - Apparatus and method for containment of underwater leak

Info

Publication number: GB2481125A
Application number: GB1109542.9A
Authority: GB
Inventors: Alan Burns
Original assignee: BAHAMAS PETROLEUM Co PLC
Current assignee: BAHAMAS PETROLEUM Co PLC
Priority date: 2010-06-08
Filing date: 2011-06-08
Publication date: 2011-12-14
Also published as: WO2011154733A1; GB201009544D0; GB201109542D0

Abstract

Apparatus for containment of underwater emissions comprises a buoyant hydrocarbon containment/storage vessel 16 and a conduit 18 having a first distal end 18a in communication with the containment vessel 16 and a second distal end 18b adapted for collecting emitted matter 12. There may be a funnel / cover 20 at the second end of the conduit to capture the leaking fluid. Flow control means 17/32 regulates the flow to and from the containment vessel 16. The flow control may be a valve, pump or gas supply. There may be a baffle 18d which can laterally deflect the flow leaving the first end of the conduit. The containment vessel may have adjustable volume. The apparatus may be anchored / tethered 24 to the sea floor 22. Spacing between a leaking well and the second end of the conduit can prevent blockage of the conduit by gas crystals.

Description

Apparatus and Method for Containment of Underwater Hydrocarbon and Other Emissions The present invention relates to an apparatus and method for containment of matter, such as, but not limited thereto, underwater hydrocarbon and other emissions and particularly, but not exclusively, to an offshore apparatus and method for containment of controlled or uncontrolled emissions originating from blowouts occurring at or near the seabed or at any point between the seabed and the surface of the water.

Offshore oil and gas production presents numerous technical and logistical challenges which have long been a source of environmental concern. History has shown that an inevitable consequence of operating in harsh conditions and deep waters is that accidental leaks and spillages of varying degrees of seriousness will occur. Indeed, concerns surrounding the potential environmental impact of hydrocarbon leaks and spillages have often led to potentially lucrative offshore production being restricted or even prevented near ecologically sensitive regions.

In an effort to mitigate environmental risks, oil companies continuously invest in the development of new and improved safety and failsafe rnechanisrris. For example, it is now well established to fit subsea wellheads with Blowout Preventers (BOP) capable of automatically closing a wellbore if underground pressures exceed safe thresholds. However, despite all available precautions being taken, safety systems are not immune to mechanical failure or human error and serious oil spillages are likely to occur again in the future.

Whilst minor subsea blowouts can be controlled before causing widespread environmental damage, high flow rate blowouts occurring in relatively inaccessible deeper waters are much more difficult to control.

A notable example was the Deepwater Horizon oil spill which began in April 2010 and has been confirmed as the largest offshore oil spillage in U.S. history. Its blowout occurred after a BOP failure on the seabed at a depth of approximately 5000 feet (>1,500m) thus posing significant technical and logistical challenges for any remedial action. At such depths access difficulties mean that recovery efforts must utilise remotely operated underwater vehicles (ROV5) and other specialist equipment.

Another factor associated with blowouts occurring at such depths is that the resulting oil plume tends to separate into multiple sub-plumes which, depending on factors such as temperature and ocean currents, may radiate at different levels and directions below the water's surface. The plume spread is inherently unpredictable and therefore presents real challenges for authorities attempting to deploy clean up and containment resources to the correct areas on the surface. For this reason, blowouts occurring at greater depths may have a more serious environmental impact.

Since a BOP generally represents the last line of defence against a continuously leaking wellbore, its failure is a serious concern. Various systems have been proposed or attempted to quickly stem or control subsea spillages occurring at or near the seabed. For example, early failed attempts to contain the Deepwater Horizon spillage included the placement of a 125-tonne container dome over the ruptured pipeline. Unfortunately, the accumulation of methane hydrates blocked the dome's outlet and so this had to be abandoned. A complete shut down of the leak was then attempted using a well established "top kill" procedure whereby heavy drilling fluids are pumped into the BOP. This technique is intended to restrict and then cease the flow of oil such that it can be permanently sealed with cement. However, in view of the high flow rate involved, this attempt also failed. The drilling of relief wells to intercept the flow from the leaking wellhead is a viable long term solution but, absent any short term solution, hydrocarbons will continue to be emitted unabated resulting in increasingly serious environmental consequences.

According to a first aspect of the present invention, there is provided an apparatus for containment of underwater emissions of matter, the apparatus comprising: a buoyant containment vessel; and a conduit; the conduit having a first distal end in communication with the containment vessel, and a second distal end adapted for capturing the emitted matter; and wherein the apparatus further comprises flow control means for controlling the flow rate of the matter entering and/or leaving the containment vessel.

Such control can be maintained by the use of one or more valve mechanisms and/or pumps between the conduit and the containment vessel.

Preferably, flow metering devices are provided to estimate the rates and volumes of solids, liquids and/or gases as well as the rate of flow of the same.

The present invention has been devised for capturing hydrocarbon emissions but it will be appreciated that the invention is equally suitable for use with any fluids or solids, combustible or otherwise. The term "fluid" is intended to include gases or liquids. In addition, where the invention uses valves these may be choke valves, sliding sleeve valves, ball valves, gate valves, plug valve or any mechanism designed for shutting off or adjusting the flow of solids, liquids or gases.

In one embodiment, the containment vessel is open, in use, to the atmosphere. Alternatively, the containment vessel is sealed from the atmosphere.

Optionally, the containment vessel comprises a lower base, and the first distal end of the conduit terminates within the containment vessel above the lower base.

Preferably, a baffle member is provided at or near the first distal end of the conduit.

Preferably, the containment vessel is adapted to allow for the containment of any type of matter, such as fluids and solids. Further preferably, the containment vessel is adapted to allow for the containment of liquid hydrocarbons. Also preferably, the gases which the containment vessel is adapted to contain include but not limited thereto, expanded air from a compressed air or nitrogen.

Optionally, the containment vessel includes a means for varying the volume of the containment vessel. For example, in one arrangement, a lower section of the containment vessel including a lower base of the containment vessel is movable with respect to an upper section of the containment vessel. This allows the distance between the lower base and upper section to be adjusted thereby adjusting the volume of the containment vessel. Such an arrangement allows the volume of the containment vessel to be regulated below sea level depending on conditions at the site and depending on the rate of flow through the conduit. Preferably, the lower section is also movable with respect to the conduit.

Optionally, a baffle member is fixed within the containment vessel and a surface thereof faces the first distal end of the conduit. Optionally, the baffle member is defined by an end cap on the conduit. Preferably, the baffle member is adapted to direct the matter laterally of the conduit.

Optionally, the flow control means comprises at least one valve provided on the conduit to regulate flow within the conduit.

Optionally, the valve is one of a sliding sleeve valve, a ball valve, a gate valve, a plug valve or a choke valve.

Optionally, the flow control means comprises a pump for removing matter from the containment vessel to an external storage and/or separation facility.

Additionally, the valve(s) may incorporate electrically wired, pneumatic, hydraulic, optical, acoustic or electromagnetic control methods.

In one embodiment, the valve(s) and/or pump(s) are dynamically adjustable manually or by automated software to optimize inflow performance at the location of emissions such that sufficient amount of emitted matter is captured while minimizing the intake of other surrounding matter, such as seawater.

Optionally, the containment vessel comprises a lower base and the pump is located proximate the base and below the first distal end of the conduit.

Optionally, the flow control means comprises a gas supply connected proximate the second open end of the conduit.

Optionally, at least one buoyancy member is attached to the conduit.

Optionally, the or each buoyancy member is attached annularly around the exterior surface of the conduit.

Optionally, the conduit is a tubular riser.

Optionally, the second distal end of the conduit has a portion having an enlarged diameter.

Optionally, the enlarged diameter portion is provided in the form of a funnel having a narrower end facing the conduit and a wider end facing away from the conduit.

Optionally, the apparatus is configured so that upon installation of the apparatus at a site, the first distal end is positioned above sea level thereby providing an overbalance to second distal end of the conduit, and thereby rendering the whole structure of the apparatus more stable yet flexible in various circumstances.

Optionally, the apparatus comprises mechanical tethers for anchoring the conduit relative to the underwater surface.

Optionally, the conduit is a reeled flexible conduit. The use of a reeled flexible conduit makes the system easier to install and to control.

Furthermore, this enables the apparatus to be compensated for during operation as the action of waves may affect the position of the second distal end relative to the seabed. The provision of a reeled flexible conduit allows the components of the apparatus located above the second distal end to flex to adjust to the movements of the second distal end.

Preferably, at least one aperture is defined in the first distal end of the conduit and the conduit extends within the containment vessel such that the aperture in the first distal end is spaced approximately 9.8 meters (approximately 32 feet) from the vessel's base.

Preferably, at least one aperture is defined in the first distal end of the conduit and the first open distal end of the conduit is positioned such that, in use, the aperture is spaced at least 9.8 meters (approximately 32 feet) below a surface of a body of fluid in which the containment vessel floats.

Preferably, the overall height of the containment vessel is greater then 19.5 meters (64 feet).

Ideally, a sub-conduit connects the containment vessel to an external storage and/or separation facility.

Advantageously, the apparatus comprises a means for suspending the second distal end above a well such that second distal end is sufficiently spaced from well components so as to prevent blockage of the conduit at the second distal end by gas crystals which may form between the well and the second distal end.

Further advantageously, the containment vessel comprises side walls and the buoyancy of the vessel is selected such that, in use the side walls project above the surface of a body of fluid in which the vessel floats.

Optionally, the apparatus can be supplied in several sections, such as, for example, a second distal end section, a conduit section and a containment vessel section and several sections can be assembled at the site. To facilitate the assembly of the sections, a guide wire system is preferably provided adapted for deployment of the sections of the apparatus.

Optionally the apparatus comprises one or more diverter lines arranged in communication with the containment vessel. Ideally, the diverter line(s) are adapted to be positioned in relation to the containment vessel so as to allow the gases to be vented from the containment vessel in the down wind direction. In this arrangement, the containment vessel is preferably sealed from the surrounding atmosphere, for example, by sealing an open top of the containment vessel.

Optionally, the diverter line(s) comprise one or more burner heads with ignition devices for burning the gases. Ideally, one or more isolation valves are provided within each diverter line.

Optionally, the apparatus comprises a cover structure at the second distal end of the conduit, the cover structure being configured to isolate the emissions from the surrounding environment. Preferably, the cover structure comprises an anchor means. The anchor means is preferably provided in the form of a suction anchor. Preferably, the cover structure comprises a caisson which in use is lowered and placed onto the seabed covering the source of the emissions. The anchor means is preferably defined by an annulus integral to the cover structure. A suction means, for example one or more vacuum pumps, is provided for creating a vacuum within the annulus, thereby creating a suction and drawing the cover structure into engagement with the seabed.

Additionally, at least one video camera surveillance device is provided at the second distal end of the conduit.

Further additionally, the apparatus can comprise one or more gas lines adapted to convey the emissions from the apparatus thereby acting as a cleaning mechanism. In such an arrangement, a closable valve is provided below the second distal end of the conduit.

According to a second aspect of the present invention, there is provided a method of containing underwater emissions of matter, the method comprising the steps of: (i) providing a buoyant containment vessel on the water's surface which may or may not be open to the atmosphere; (ii) providing a conduit having a first distal end in fluid communication with the containment vessel, and a second open distal end adapted to capture the emitted; (iii) positioning the containment vessel and the second open distal end of the conduit such that the matter is captured within the second open distal end; (iv) conveying the captured matter from the site of the emissions to the containment vessel; and (v) removing the captured matter from the containment vessel in a controlled manner; wherein the step of conveying and/or removing the captured matter is regulated by control means for controlling the flow rate of the matter entering and/or leaving the containment vessel.

Optionally, the step of positioning the containment vessel and the second distal end of the conduit involves anchoring the apparatus to the underwater surface.

Additionally or alternatively, the step of positioning the containment vessel and the second open distal end of the conduit involves stabilising the apparatus by attaching one or more buoyancy members to the conduit.

Optionally, the step of conveying the captured matter from the site of the emissions to the containment vessel is assisted by supplying gas from an external source into the conduit.

Optionally, the step of removing the captured matter from the containment vessel in a controlled manner involves pumping the matter to an external storage and/or separation facility.

Additionally or alternatively, the step of removing the captured matter from the containment vessel in a controlled manner involves combusting the matter.

Additionally or alternatively, the step of removing the captured matter from the containment vessel in a controlled manner involves providing a baffle member at or near the second distal end of the conduit to prevent pressurised matter being expelled from the containment vessel.

Optionally, the step of controlling the flow rate of matter entering and/or leaving the containment vessel involves monitoring the level of matter within the containment vessel and providing a valve on the conduit actuatable to maintain the level of matter within selected thresholds.

Ideally, the step of providing a conduit having a first distal end in fluid communication with the containment vessel includes the step or positioning the first distal end of the conduit upwardly spaced from a lower base of the vessel.

Optionally, the method comprises the step of spacing the first distal end of the conduit from the lower base by approximately 9.8 meters (approximately 32 feet).

Optionally, the method comprises the step of positioning the first distal end or the conduit at least 9.8 meters (approximately 32 feet) below the water's surface.

Optionally, the step of positioning the second distal end involves suspending the second distal end above a well such that the second distal end is sufficiently spaced from well components so as to prevent blockage or the conduit at the second distal end by gas crystals which may form between the well and the second distal end.

Optionally, the method comprises the step of varying the volume of the containment vessel. In one variation, the step of varying the volume of the containment vessel includes moving a lower section of the containment vessel including a lower base of the containment vessel with respect to an upper section of the containment vessel thereby varying the distance between the lower base and upper section and thereby adjusting the volume of the containment vessel.

Advantageously, the method comprises the step of selecting the buoyancy of the vessel such that, in use, side walls of the containment vessel project above the surface of a body of fluid in which the vessel floats.

Optionally, the method comprises the step of configuring the apparatus so that upon installation of the apparatus at a site, the first distal end is positioned above sea level thereby providing an overbalance to the second distal end of the conduit, and thereby rendering the whole structure of the apparatus more stable yet flexible in various circumstances.

Optionally, the method comprises the step of providing mechanical tethers for anchoring the conduit relative to the underwater surface.

Optionally, the method comprises the step of providing the conduit in the form of a reeled flexible conduit.

Ideally, the method comprises the step of connecting the containment vessel to an external storage and/or separation facility with a sub-conduit.

Optionally, the method comprises the step of supplying the apparatus in several sections, such as, for example, a second distal end section, a conduit section and a containment vessel section and assembling several sections at the site.

Advantageously, the method comprises the steps providing a guide wire system and deploying the sections of the apparatus using the guidewire system.

Optionally, the method comprises the step of providing one or more diverter lines and arranging the diverter lines in communication with the containment vessel. Ideally, the method includes the step of positioning the diverter lines in relation to the containment vessel so as to allow the gases to be vented from the containment vessel in the down wind direction.

Preferably, the method comprises the step of sealing the containment vessel from the surrounding atmosphere, for example, by sealing an open top of the containment vessel.

Optionally, the method includes the step of equipping the diverter line(s) with one or more burner heads having ignition devices and burning the gases. Ideally, the method includes providing each diverter line with one or more isolation valves.

Optionally, the method comprises the steps of providing a cover structure at the second distal end of the conduit and configuring the cover structure to isolate the emitted matter from the environment surrounding the cover structure. Preferably, the method comprises the steps of providing the cover structure with an anchor means, preferably, in the form of a suction anchor. Preferably, the method comprises the steps of providing the cover structure with a caisson, lowering the caisson and placing the caisson onto the seabed covering the source of the emissions. Preferably, the method comprises the steps of providing a suction means, for example one or more vacuum pumps, creating a vacuum within the annulus, thereby creating a suction; and drawing the cover structure into engagement with the seabed.

Preferably, the method comprises the steps of providing at least one video camera surveillance device at the second distal end of the conduit.

Preferably, the method comprises the steps of providing one or more gas lines adapted to convey the emissions from the apparatus thereby acting as a cleaning mechanism. Conveniently, the method comprises the step of providing a closable valve is below the second distal end of the conduit.

Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a schematic representation of apparatus for containment of subsea emissions; Fig. 2 is a schematic representation showing the containment vessel of Fig. 1; Fig. 3 is a schematic representation showing an alternative embodiment for increasing emissions drawn into the apparatus; Fig. 4 is a schematic representation showing a further alternative embodiment for avoiding blockages in the apparatus; Fig. 5 is a schematic representation showing a yet further alternative embodiment; Fig. 6 is a schematic representation showing an adjustable containment vessel.

Fig. 7 is a schematic representation showing a sliding sleeve valve device on a conduit of the apparatus; Fig. 8 is a schematic representation showing a first distal end of the conduit positioned above sea level; Fig. 9 -9b are schematic representations showing stages of deployment of an embodiment of the apparatus comprising a reeled conduit; Fig. 10 is a schematic representation showing optional combustion of emissions diverted from a sealed from the atmosphere containment vessel; and Fig. 11 is a schematic representation showing a cover structure including a suction anchor and a video surveillance device.

Fig. 1 shows a leaking well 10 emitting hydrocarbons 12 into a body of water 14 in an uncontrolled manner. For offshore oil and gas production, the body of water will be the sea. However, it is to be understood that the invention is equally applicable to lakes, rivers and other in-land bodies of water.

A buoyant containment vessel 16, provided with side walls 16a and a lower base 16b floats on the surface of the water 14 such that its side walls 16a lie above the surface of the body of water 14. The upper end 16c of the containment vessel 16 may be open to the atmosphere. A conduit in the form of a riser 18 passes through the vessel's lower base 16b in a sealed manner. A first open distal end 18a of the riser 18 is located within the containment vessel 16 and is positioned to lie above the vessel's base 16b.

The riser 18 extends downwardly from the containment vessel 16 such that its opposite (second) open distal end 18b lies proximate, but spaced from, the leaking well 10. Valves 17 are provided proximate opposite ends of the riser 18 and are actuatable to regulate the flow of hydrocarbon emissions therein.

The second distal end 18b terminates with a funnel 20 serving to increase the cross-sectional area presented to the leaking well 10, and thus maximise the volume of hydrocarbon emissions 12 captured by the apparatus. The funnel 20 is anchored to the seabed 22 by means of chains 24 or other suitable tethers. If necessary, and depending upon the length and weight of the riser 18, the apparatus may be further stabilised by attaching buoyant collars 26 distributed along the length of the riser 18.

Fig. 2 shows the containment vessel 16 in more detail. The containment vessel 16 is generally cylindrical so as to minimise the surface contact area with the surrounding sea water regardless of the direction of the currents. A buoyant collar 28 fits annularly around the side walls 16a so as to enable the containment vessel 16 to float. The buoyancy of the collar 28 is selected such that, in use, the side walls 1 6a project above the surface of the body of water 14. If the containment vessel 16 is to be used in open seas then its height h between the lower base 16b and the open end 16c is chosen such that the side walls 16a will extend significantly above the water's surface so as to avoid ingress of sea water during rough seas.

The containment vessel's volume V = ir.r2.h (where r = radius of the vessel).

Accordingly, it will be appreciated that dimensions of the containment vessel 16 and the buoyancy of the collar 28 can each be varied depending upon the expected flow rate of hydrocarbon emissions to be contained.

As noted above, the first open distal end 1 8a of the riser 18 is located within the containment vessel 16 and is positioned to lie above the vessel's lower base 16b. The riser 18 is provided with an end cap 18d so as to prevent hydrocarbons being emitted vertically. Alternatively, although not shown in the drawings, one or more apertures are provided in the side wall of the riser 18 proximate its first open distal end 18a so as to allow hydrocarbons to be emitted in a radial direction.

In the examples shown in Figures 1,2,6,7,9 and 10, ,the riser 18 extends vertically within the containment vessel 16 such that the aperture(s) in its first open distal end 18a is positioned approximately 32 feet (approximately 9.8 metres) above the vessel's base 16b. This height can be adjusted to suit different circumstances. This provides an annular volume around the riser 18 into which liquid hydrocarbon emissions 12 are collected after exiting the first open distal end 18a. For reasons described in more detail below, the first open distal end 18a of the riser 18 is also positioned such that, in use, its aperture(s) lies at least 32 feet (approximately 9.8 metres) below the surface of the body of water 14. Accordingly, the overall height h of the illustrated containment vessel 16 is greater than 64 feet (19.5 metres).

A sub-conduit 30 connects the base 16b of the containment vessel 16 to an external storage and/or separation facility, such as a floating barge 34. A pump 32 is provided proximate the junction of the base 16b and the sub-conduit 30 for pumping the emitted hydrocarbons 12 from the containment vessel 16 into the floating barge 34.

In use, the containment vessel 16 is manoeuvred into position directly above the leaking well 10. The precise positioning of the containment vessel 16 may be assisted and maintained by use of GPS equipment. If required, the containment vessel 16 may be tethered to vessels or rigs on the surface of the body of water 14. The full length of the riser 18 may be pre-attached to the containment vessel such that its second distal end 18b will inevitably be positioned over the leaking well 10. However, if the apparatus is provided in kit form (see Fig. 5), it will be necessary to build the riser up to the required length from multiple individual sections until the second distal end 18b is positioned at an appropriate height above the leaking well 10.

Once the second distal end 18b is correctly positioned, its funnel 20 is suspended above the leaking well lOso as to capture emitted hydrocarbons 12. In order to maintain the funnel 20 in the optimum position over the leaking well 10, it is anchored to the sea bed 22 by chains 24 or other appropriate tethers. Appropriate tensioning of the chains 24 will prevent unwanted movement of the funnel 20 caused by, for example, ocean currents or the volatility of the hydrocarbon emissions 12. If required, the riser 18 may be further stabilised by attaching buoyant collars 26 along its length.

The increased cross sectional area of the funnel 20 relative to the riser 18 serves to partially envelope the hydrocarbon emissions 12 without requiring any physical contact to be made between the apparatus and the leaking well 10. By eliminating any requirement for physical contact between the riser 18 and the leaking well 10, the present invention can be quickly deployed to contain leaks irrespective of the technical characteristics of the well head, or the type of damage suffered.

Since the specific gravity of hydrocarbon emissions 12 is less than that of the body of water 14, the hydrocarbon emissions 12 will tend to rise away from the sea bed 22. However, it is preferable that the flow rate through the riser 18 be optimised so as to avoid any overspill of hydrocarbon emissions 12 around the exterior of the funnel 20. There are a number of ways in which the flow rate through the riser 18 can be regulated. In the examples shown in Figures 1, 2, 6, 7, 9 and 10, by positioning the first open distal end 18a of the riser 18 at least 32 feet (approximately 9.8 metres) below the surface of the body of water 14 -as described above -the hydrostatic pressure differential between the interior and exterior of the riser will be maximised, thus serving to maximise the flow rate up through the riser 18.

The pressure differential between the funnel 20 and the first distal end 18a of the riser 18 can be very significant depending upon the depth at which the funnel 20 is situated. Therefore, as the hydrocarbon emissions 12 travel up through the riser 18 the progressive reduction in pressure will cause gasification to occur. The expanding gas creates a large pressure differential within the riser 18 serving to draw hydrocarbon emission 12 into the funnel 20 at high pressure. The combined effect of these actions is that hydrocarbon emissions 12 may be expelled violently from the first distal end 1 8a of the riser 18 within the containment vessel 16.

Depending upon how violently the hydrocarbon emissions 12 are expelled, there is a danger that the reaction force would overcome the buoyancy of the containment vessel 16 forcing its open end 1 6c below the surface of the body of water 14 and causing the vessel to sink. However, by closing off the upper end of the riser 18 with an end cap 18a, the hydrocarbon emissions 12 impact against the end cap and are re-directed in a radial direction thus helping to cancel the action/reaction forces.

As the hydrocarbon emissions 12 are emitted from the first distal end 18a of the riser, hydrocarbon liquids are collected within the containment vessel 16.

Hydrocarbon gases may be combusted within the containment vessel. Pump 32 is used to drain the liquid hydrocarbon emissions 12 from the containment vessel 16 and pump them onto a floating barge 34. Additional pumps (not shown) may be required depending upon the depth through which the hydrocarbons are to be pumped. The volume of liquid within the containment vessel 16 may be monitored by appropriate means to ensure that the liquid level is maintained within acceptable thresholds.

Figure 6 shows a containment vessel having an adjustable lower section 1 6d movable with respect to an upper section 16e of the containment vessel 16 and with respect to the riser 18 SO as to vary the volume of the containment vessel 16. The lower section 16d may be dynamically adjustable in-situ or the lower section 16d can be fixed at a required level prior to deployment. In Figure 6, a telescopically extendable/retractable lower section 16d is shown.

It is envisaged that the extendable/retractable lower section 16d can be provided in various forms, such as, for example, by additional flanged sections.

Fig. 7 shows an embodiment utilising a sliding sleeve valve 41. The valve 41 is dynamically adjustable hydraulically, pneumatically, manually or electrically, thereby enabling hydraulic communication between the inside of the riser 18 to the containment vessel 16.

In a further embodiment, the first distal end 18a of the riser 16 is positioned above the sea level as shown in Fig. 8. The so positioned first distal end 18a of the riser 18 overbalances the second distal end 18b, thereby providing for greater stability and flexibility of the assembled structure of the apparatus.

It is important for the liquid level to be kept below the height of the opening(s) in first distal end 1 8a of the riser 18. If the liquid level is found to be rising too quickly then the pumping rate of pump 32 may be increased to compensate; and/or the valve(s) 17 may be actuated to temporarily reduce or prevent any further intake of hydrocarbon emissions 12 into the containment vessel 16.

However, if insufficient volumes of fluid are being introduced into the containment vessel 16 then the flow rate may be artificially increased by providing a compressed gas supply 36 from an external source and introducing it into the riser 18 at or near the funnel 20. Such an arrangement is shown in Fig. 3 and Fig. 4. The rising gas will serve to decrease the pressure gradient within the riser 18 and thus draw additional hydrocarbon emissions 12 into the funnel 20.

Some previously attempted hydrocarbon containment systems have failed because the in-take of their conical end pieces have been blocked by methane hydrate crystals formed by entrained gas combining with very cold sea water. However, the apparatus of present invention is adapted to avoid any formation of methane hydrate crystals on its inner surfaces. Firstly, as noted above, the funnel 20 is suspended above the leaking well 10 such that physical contact between the two is avoided. By maintaining an appropriate spacing between the narrow end of the funnel 20, i.e. the end nearer the interior of the of the riser 18 and remote the wider end of the funnel 20 which faces the well 1O,and the source of the leaking well 10, it is less likely that methane hydrate crystals will block the funnel 20. This is because the density of methane hydrate crystals is higher than that of sea water such that any crystals should sink to the seabed 22 before reaching the funnel entrance.

However, the apparatus of the present invention may optionally be provided with further features to tackle the potential problem of methane hydrate crystal formation. For example, as shown in Fig. 4, by providing a methanol supply 38 from an external source and introducing it into the riser 18 proximate the funnel 20 the formation of methane hydrate crystals can be counteracted. Similarly, by heating the hydrocarbon emissions 12 at the point of entry into the funnel 20 then the formation of methane hydrate crystals can be avoided. This can be achieved by igniting the hydrocarbon emissions 12 by using, for example, compressed air and/or liquid oxygen and/or propane. An ignition system 40 is shown schematically in Fig. 4.

Modifications and improvements may be made to the foregoing without departing from the scope of the present invention. For example, instead of providing the first distal end 18a of the riser 18 with an integral end cap 18d, a separate baffle member 18g (Fig. 6 and Fig. 7) may be provided. The baffle member 18g formed, for example, from toughened steel is attached to the inner surface of the containment vessel 16 and/or the riser so as to intercept the hydrocarbon emissions 12 being expelled from the first distal end 18a of the riser 18. The invention need not be restricted to the use of particular types of valves 17 and any suitable valve arrangement may be employed. As well as anchoring the funnel 20 to the seabed 22 by tethers 24, it may be necessary or desirable to also attach tethers 24 along the length of the riser 18 for added stability. The containment vessel 16 need not be cylindrical and could be any other shape which is stable when floating.

It is anticipated that the apparatus of the present invention could be provided in kit form and stored on, for example, an offshore oil platform for rapid deployment during an emergency. The kit would comprise a number of individual pipe lengths sufficient to reach the seabed under any given platform. Each pipe section could be provided with flanged ends and sealing gaskets to facilitate quick connection by means of bolts or other suitable connectors. Such a pipe arrangement is shown in Fig. 5 whereby the riser sections 18 are provided with flanged ends 19 which can be bolted or otherwise fastened together. Alternatively, a standard oil well drill pipe in which the individual lengths are screwed together could be employed. The funnel 20 could be attached by means of a screw connection. Such an arrangement could dispense with any buoyancy members along the length of the riser 18 and rely solely on the buoyancy collar 28 provided around the containment vessel 16.

Alternatively, a reeled riser system 42 and 42a mounted in or on a buoyant vessel 44 could be deployed. Figures 9, 9a and 9b show an apparatus of the invention being assembled from three sections using a guide wire system 43.

As shown in Fig. 9, the funnel section 20 is installed first. Next, the flexible riser section 42a is unwound from a reel 42 on the guide wire 43 to couple with the funnel 20. Finally, the containment vessel 16 together with a riser section containing a first distal end 42b is coupled with the flexible riser portion 42a. In practice, the apparatus can be assembled from any number of sections.

It may be beneficial to vent or combust gases away from the containment vessel 16. This would protect the apparatus from the potentially explosive nature of the emissions. Fig. 10 shows an example of diverter lines 45 incorporating valves 46 and a commercial burner system 47. The example of Fig. 10 shows two diverter lines 45, but in practice one or more can be provided. The diverter lines 45 are preferably adapted to be positioned with respect to the containment vessel 16 so that the gases are vented in a down wind direction. In this embodiment, the containment vessel 16 is sealed from the atmosphere. The diverter lines 45 are in communication with the interior of the containment vessel 16 to enable the venting of the gases frorri the containment vessel 16. A burner system 47 is provided for combusting the gases diverted into the diverter lines 45.

It is advantageous to completely seal the emissions from the body of water 14. Fig. 11 a cover structure a caisson 49 and a suction anchor device 48.

Monitoring devices, potentially video camera(s) 55 may be included in the caisson 49.

The suction anchor 48 includes an annulus 48a and a pump 50. Liquid is pumped out from within the annulus 48a via the pump 50, thereby decreasing the pressure within the annulus 48a and, thereby sucking the caisson 49 down into the sea bottom 22.

It will be appreciated that the invention not limited to the examples described above. Variations are possible within the scope of the invention as defined in the appended claims.

Claims

Claims: 1. An apparatus for containment of underwater emissions of matter, the apparatus comprising: a buoyant containment vessel; and a conduit; the conduit having a first distal end in communication with the containment vessel, and a second distal end adapted for capturing the emitted matter; and wherein the apparatus further comprises flow control means for controlling the flow rate of the matter entering and/or leaving the containment vessel.
2. An apparatus as claimed in claim 1, wherein the containment vessel comprises a lower base, and the first distal end of the conduit terminates within the containment vessel above the base.
3. An apparatus as claimed in claim 1 or claim 2, wherein a baffle member is provided at or near the first distal end of the conduit.
4. An apparatus as claimed in claim 3, wherein the baffle member is fixed within the containment vessel and a surface thereof faces the first distal end of the conduit.
5. An apparatus as claimed in claim 3, wherein the baffle member is defined by an end cap on the conduit.
6. An apparatus as claimed in any one of claims 3 to 5, wherein the baffle member is adapted to direct the matter laterally of the conduit.
7. An apparatus as claimed in any preceding claim, wherein the flow control means comprises at least one valve provided on the conduit to regulate flow within the conduit.
8. An apparatus as claimed in claim 7, wherein the valve is one of a sliding sleeve valve, a ball valve, a gate valve, a plug valve or a choke valve.
9. An apparatus as claimed in any preceding claim, wherein the flow control means comprises a pump for removing matter from the containment vessel to an external storage and/or separation facility.
10. An apparatus as claimed in any preceding claim, wherein the containment vessel comprises a lower base and the pump is located proximate the base and below the first distal end of the conduit.
11. An apparatus as claimed in any preceding claim, wherein the flow control means comprises a gas supply connected proximate the second open end of the conduit.
12. An apparatus as clairried in any preceding claim, wherein at east one buoyancy member is attached to the conduit.
13. An apparatus as claimed in claim 12, wherein the or each buoyancy member is attached annularly around the exterior surface of the conduit.
14. An apparatus as claimed in any preceding claim, wherein the conduit is provided in the form of a tubular riser.
15. An apparatus as claimed in any preceding claim, wherein the second open distal end of the conduit has a portion having an enlarged diameter.
16. An apparatus as claimed in claim 15, wherein the enlarged diameter portion is provided in the form of a funnel having a narrower end facing the conduit and a wider end facing away from the conduit.
17. An apparatus as claimed in any preceding claim, wherein the apparatus comprises mechanical tethers for anchoring the conduit relative to the underwater surface.
18. An apparatus as claimed in claim 2 and in any one of claims 3 to 17, wherein at least one aperture is defined in the first distal end of the conduit and the conduit extends within the containment vessel such that the aperture in the first distal end is spaced approximately 9.8 meters (approximately 32 feet) from the vessel's base.
19. An apparatus as claimed in any preceding claim, wherein at least one aperture is defined in the first distal end of the conduit and the first open distal end of the conduit is positioned such that, in use, the aperture is spaced at least 9.8 meters (approximately 32 feet) below a surface of a body of fluid in which the containment vessel floats.
20. An apparatus as claimed in claim 18 and claim 19, wherein the overall height of the containment vessel is greater then 19.5 meters (64 feet).
21. An apparatus as claimed in any preceding claim, wherein a sub-conduit connects the containment vessel to an external storage and/or separation facility.
22. An apparatus as claimed in any preceding claim, wherein the apparatus comprises a means for suspending the second distal end above a well such that second distal end is sufficiently spaced from well components so as to prevent blockage of the conduit at the second distal end by gas crystals which may form between the well and the second distal end.
23. An apparatus as claimed in any preceding claim wherein the containment vessel comprises side walls and the buoyancy of the vessel is selected such that, in use the side walls project above the surface of a body of fluid in which the vessel floats.
24. An apparatus as claimed in any preceding claim, wherein the conduit is provided in the form of a reeled flexible conduit.
25. An apparatus as claimed in any preceding claim, wherein the apparatus is supplied in several sections suitable for assembly at the site.
26. An apparatus as claimed in claim 25, wherein a guide wire system is provided adapted for deployment of the sections of the apparatus.
27. An apparatus as claimed in any preceding claim, wherein the apparatus comprises one or more diverter lines arranged in communication with the containment vessel.
28. An apparatus as claimed in claim 27, wherein the diverter line(s) is adapted to be positioned in relation to the containment vessel so as to allow the gases to be vented from the containment vessel in the down wind direction.
29. An apparatus as claimed in claim 27 or claim 28, wherein the containment vessel is sealed from the surrounding atmosphere.
30. An apparatus as claimed in any one of claims 27 to 29, wherein the diverter line(s) comprises one or more burner heads with ignition devices for burning the gases.
31. An apparatus as claimed in any one of claims 27 to 30, wherein one or more isolation valves are provided within the or each diverter line.
32. An apparatus as claimed in any preceding claim, wherein the apparatus comprises a cover structure at the second distal end of the conduit, the cover structure being configured to isolate the emissions from the surrounding environment.
33. An apparatus as claimed in claim 32, wherein the cover structure comprises an anchor means.
34. An apparatus as claimed in claim 33, wherein the anchor means is defined by an annulus integral to the cover structure.
35. An apparatus as claimed in claim 34, wherein a suction means is provided for creating a vacuum within the annulus, thereby, in use, creating suction and drawing the cover structure into engagement with the seabed.
36. An apparatus as claimed in claim 34 or claim 35, wherein the anchor means is provided in the form of a suction anchor.
37. An apparatus as claimed in any one of claims 33 to 36, wherein the cover structure comprises a caisson which in use is lowered and placed onto the seabed covering the source of the emissions.
38. An apparatus as claimed in any preceding claim, wherein at least one video camera surveillance device is provided at the second distal end of the conduit.
39. An apparatus as claimed in any preceding claim, wherein the apparatus comprises one or more gas lines adapted to convey the emissions from the apparatus thereby acting as a cleaning mechanism.
40. An apparatus as claimed in claim 39, wherein a closable valve is provided below the second distal end of the conduit.
41. An apparatus as claimed in any one of claims 1 to 27 and 30 to 40, wherein the containment vessel is open, in use, to the atmosphere.
42. An apparatus as claimed in claims 1 to 40, wherein the containment vessel is sealed from the atmosphere.
43. An apparatus as claimed in any preceding claim, wherein the containment vessel is adapted to allow for the containment of any type of matter.
44. An apparatus as claimed in any preceding claim, wherein the containment vessel is adapted to allow for the containment of liquid hydrocarbons.
45. An apparatus as claimed in any preceding claim, wherein vessel is adapted to contain expanded air from a compressed air or nitrogen.
46. An apparatus as claimed in any preceding claim, wherein the containment vessel includes a means for varying the volume of the containment vessel.
47. An apparatus as claimed in claim 46, wherein a lower section of the containment vessel including a lower base of the containment vessel is movable with respect to an upper section of the containment vessel thereby allowing the distance between the lower base and upper section to be adjusted thereby adjusting the volume of the containment vessel.
48. A method of containing underwater emissions of matter, the method comprising the steps of: (I) providing a buoyant containment vessel on the water's surface which may or may not be open to the atmosphere; (ii) providing a conduit having a first distal end in fluid communication with the containment vessel, and a second open distal end adapted to capture the emitted matter; (iii) positioning the containment vessel and the second open distal end of the conduit such that the matter is captured within the second open distal end; (iv) conveying the captured rriatter from the site of the emissions to the containment vessel; and (v) revolving the captured matter from the containment vessel in a controlled manner; wherein the step of conveying and/or removing the captured matter is regulated by control means for controlling the flow rate of the matter entering and/or leaving the containment vessel.
49. A method as claimed in claim 48, wherein the step of positioning the containment vessel and the second open distal end of the conduit involves anchoring the apparatus to the underwater surface.
50. A method as claimed in claims 48 or claim 49 wherein, the step of positioning the containment vessel and the second open distal end of the conduit involves anchoring the apparatus to the underwater surface.
51. A method as claimed in any one of claims 48 to 50, wherein, the step of conveying the captured matter from the site of the emissions to the containment vessel is assisted by supplying gas from an external source into the conduit.
52. A method as claimed in any one of claims 48 to 51, wherein the step of removing the captured matter from the containment vessel in a controlled manner involves pumping the matter to an external storage and/or separation facility.
53 A method as claimed in any of claims 48 to 52, wherein the step of removing the captured hydrocarbons emissions from the containment vessel in a controlled manner involves combusting the emissions.
54. A method as claimed in any of claims 48 to 53, wherein the step of removing the captured matter from the containment vessel in a controlled manner involves providing a baffle member at or near the first distal end of the conduit to prevent pressurised matter being expelled from the containment vessel.
55. A method as claimed in any of claims 48 to 54, wherein the step of controlling the flow rate of fluid entering and/or leaving the containment vessel involves monitoring the level of matter within the containment vessel and providing a valve on the conduit actuatable to maintain the level of hydrocarbon emissions within selected thresholds.
56. A method as claimed in any of claims 48 to 55, wherein the step of providing a conduit having a first distal end is fluid communication with the containment vessel includes the step or positioning the first distal end of the conduit upwardly spaced from a lower base of the vessel.
57. A method as claimed in claim 56, wherein the method comprises the step of spacing the first distal end of the conduit from the lower base by approximately 9.8 meters (approximately 32 feet).
58. A method as claimed in any of claims 48 to 57, wherein the method comprises the step of positioning the first distal end or the conduit at least 9.8 meters (approximately 32 feet) below the water's surface.
59. A method as claimed in any of claims 48 to 58, wherein the step of positioning the second distal end involves suspending the second distal end above a well such that the second distal end is sufficiently spaced from well components so as to prevent blockage or the conduit at the second distal end by gas crystals which may form between the well and the second distal end.
60. A method as claimed in any of claims 48 to 59, wherein the method comprises the step of varying the volume of the containment vessel.
61. A method as claimed in claim 60, wherein the step of varying the volume of the containment vessel includes moving a lower section of the containment vessel including a lower base of the containment vessel with respect to an upper section of the containment vessel thereby varying the distance between the lower base and upper section and thereby adjusting the volume of the containment vessel.
62. A method as claimed in any of claims 48 to 61, wherein the method comprises the step of selecting the buoyancy of the vessel such that, in use, side walls of the containment vessel project above the surface of a body of fluid in which the vessel floats.
63. A method as claimed in any of claims 48 to 62, wherein the method comprises the step of configuring the apparatus so that upon installation of the apparatus at a site, the first distal end is positioned above sea level thereby providing an overbalance to the second distal end of the conduit, and thereby rendering the whole structure of the apparatus more stable yet flexible in various circumstances.
64. A method as claimed in any of claims 48 to 63, wherein the method comprises the step of providing mechanical tethers for anchoring the conduit relative to the underwater surface.
65. A method as claimed in any of claims 48 to 64, wherein the method comprises the step of providing the conduit in the form of a reeled flexible conduit.
66. A method as claimed in any of claims 48 to 65, wherein the method comprises the step of connecting the containment vessel to an external storage and/or separation facility with a sub-conduit.
67. A method as claimed in any of claims 48 to 66, wherein the method comprises the step of supplying the apparatus in several sections and assembling several sections at the site.
68. A method as claimed in claim 67, wherein the method comprises the steps providing a guide wire system and deploying the sections of the apparatus using the guidewire system.
69. A method as claimed in any of claims 48 to 68, wherein the method comprises the step of providing one or more diverter lines and arranging the diverter lines in communication with the containment vessel.
70. A method as claimed in any of claims 48 to 69, wherein the method includes the step of positioning the diverter lines in relation to the containment vessel so as to allow the gases to be vented from the containment vessel in the down wind direction.
71. A method as claimed in claim 70, wherein the method comprises the step of sealing the containment vessel from the surrounding atmosphere, for example, by sealing an open top of the containment vessel.
72. A method as claimed in claim 70 or claim 71, wherein the method includes the step of equipping the diverter line(s) with one or more burner heads having ignition devices and burning the gases.
73. A method as claimed in any one of claims 70 to 72, wherein the method includes providing each diverter line with one or more isolation valves.
74. A method as claimed in any of claims 48 to 73, wherein the method comprises the steps of providing a cover structure at the second distal end of the conduit and configuring the cover structure to isolate the emitted matter from the environment surrounding the cover structure.
75. A method as claimed in claim 74, wherein the method comprises the steps of providing the cover structure with an anchor means, preferably, in the form of a suction anchor.
76. A method as claimed in claim 74 or claim 75, wherein the method comprises the steps of providing the cover structure with a caisson, lowering the caisson and placing the caisson onto the seabed covering the source of the emissions.
77. A method as claimed in any one of claims 74 to 76, wherein the method comprises the steps of providing a suction means, for example one or more vacuum pumps, creating a vacuum within the annulus, thereby creating a suction; and drawing the cover structure into engagement with the seabed.
78. A method as claimed in any of claims 48 to 77, wherein the method comprises the steps of providing at least one video camera surveillance device at the second distal end of the conduit.
79. A method as claimed in any of claims 48 to 78, wherein the method comprises the steps of providing one or more gas lines adapted to convey the emissions from the apparatus thereby acting as a cleaning mechanism.
80. A method as claimed in any of claims 48 to 79, wherein the method comprises the step of providing a closable valve below the second distal end of the conduit.
81. An apparatus for containment of under water hydrocarbon emission substantially as herein described with reference to and/or as shown in the accompanying drawings.
82. A method of containing underwater hydrocarbon emissions substantially as herein described.