Patent Application
20170321524
The present invention concerns a containment system for recovering spilled oil that is leaking under water.
The present invention concerns more precisely a containment system for recovering a hydrocarbon fluid from a leaking device that is situated at the seafloor and that is leaking the hydrocarbon fluid from a well.
Recovering oil that is leaking from an under water oil device is a great problem, especially for oil device that are installed at deep sea floor.
The explosion on the “Deepwater Horizon” platform in the Gulf of Mexico demonstrated how much such a containment system is difficult to control.
One of the main problems was the formation of hydrates that clogged the used containment system.
For example, at a depth of around 1500 meters or more, the sea water is cold (for example around only 5° C.) and at a high pressure. These environment conditions may transform the sea water and hydrocarbon fluid into hydrates having a quasi-solid phase and which can fill and clogged any cavity.
Hydrates inhibitors like methanol could be injected to avoid hydrate formation. But, the needed quantity of such chemical is very large and inhibitors are also pollution for the environment.
Heating of the containment system could be used to avoid hydrate formation. But, as the volume of cavity of the containment system is great, the heating is slow and amount of heat is too important.
One object of the present invention is to provide a containment system that avoids the formation of hydrates inside the dome.
To this effect, the containment system of present invention is adapted to be landed at the seafloor corresponding to a base level of the containment system. It comprises:
Thanks to these features, the volume of the cavity can be completely isolated to the sea water during the descent of the containment system from the sea surface to the seafloor.
The cavity can be easily previously filled with an anti hydrates fluid at the sea surface.
The quantity of anti hydrates fluid is enough for preventing hydrates formation inside the cavity when the containment system is installed around the leaking device at the sea floor.
The containment system does not need additional pipes to be connected between a sea surface vessel and the containment system installed at the seafloor for injecting an anti hydrates fluid during operation.
The containment system does not need additional devices to be connected between a sea surface vessel and the containment system installed at the seafloor for feeding energy to the containment system. For example, it does not need electrical cable for supplying electrical energy to an electric heater for heating the dome.
The anti hydrates fluid can be enclosed inside the dome and may be heated, before the containment system is made to go down to the leaking device.
The containment system can be installed quickly.
The containment system is cheaper.
In various embodiments of the containment system, one and/or other of the following features may optionally be incorporated.
According to an aspect of the containment system, the lower opening is between 6 and 12 meters wide, and preferably between 8 and 10 meters wide.
According to an aspect of the containment system, the dome is thermally insulated with an insulating material for having an overall heat transfer coefficient of the dome lower than 1 W·m−2·K−1.
According to an aspect of the containment system, the dome comprises a structure that is rigid for building a shape of the dome.
According to an aspect of the containment system, the structure is composed of interconnected beams.
According to an aspect of the containment system, the dome comprises an envelope disposed substantially inside the structure and being flexible to adapt itself to the shape of the structure and to seal the cavity.
According to an aspect of the containment system, the envelope extends downwards below a lower end of the structure to form a flexible lower opening.
According to an aspect of the containment system, the dome comprises an envelope that extends downward below a lower end of the structure to form a flexible lower opening.
According to an aspect of the containment system, the lower closing assembly comprises a narrowing mechanism that is able to close up a lower end of the envelope to close the lower opening.
According to an aspect of the containment system, the lower closing assembly is a door mechanism articulated to a lower end of the dome and comprising a driving mechanism to close or open the lower opening.
According to an aspect of the containment system, the lower closing assembly is a diaphragm mechanism positioned at a lower end of the dome and comprising a driving mechanism to close or open the lower opening.
According to an aspect of the containment system, the lower closing assembly is a door mechanism attached to a lower end of the dome and comprising a driving mechanism to free the door and to open the lower opening.
According to an aspect of the containment system, the lower closing assembly comprises a flexible membrane, said flexible membrane being adapted for being penetrated by the leaking device when the containment system is moved so as the leaking device enters the cavity.
Another object of the invention is to provide a method for using the containment system for recovering hydrocarbon fluid from a leaking device that is situated at the seafloor and that is leaking hydrocarbon fluid from a well, said containment system being adapted to be landed at the seafloor corresponding to a base level of the containment system. The containment system comprises at least:
The method of the invention comprises the following successive steps:
a) providing a containment system at a first location near sea surface,
b) closing the upper valve and the lower closing assembly, and filling the cavity with an anti hydrates fluid,
c) making the containment system going from the first location down to a second location near the leaking device,
d) connecting a pipe to the upper opening,
e) opening the lower opening by the lower closing assembly,
f) moving the containment system so as the leaking device enters the cavity,
g) opening the upper valve for recovering the hydrocarbon fluid.
Thanks to the above method, the dome can be installed above the leaking device very quickly with a very large quantity of anti hydrates fluid. Hydrates formation inside the cavity is then prevented.
In preferred embodiments of the method proposed by the invention, one and/or the other of the following features may optionally be incorporated.
According to an aspect of the method, the anti hydrates fluid is heated before the filling step b).
According to an aspect of the method, the anti hydrates fluid comprises one or a combination of the fluid components chosen in the list of water, salted water, dead oil, an alcohol, an ethanol, a methanol, a glycol, an ethylene glycol, a diethylene glycol, and a low-dosage hydrate inhibitor (LDHI).
Other features and advantages of the invention will be apparent from the following detailed description of at least one of its embodiments given by way of non-limiting example, with reference to the accompanying drawings. In the drawings:
In the various figures, the same reference numbers indicate identical or similar elements. The direction Z is a vertical direction. A direction X or Y is a horizontal or lateral direction. These are indications for the understanding of the invention.
This containment system 1 is adapted for recovering hydrocarbon fluid from a leaking device 2 that is situated at a seafloor 5 of a deep offshore installation. The leaking device 2 is for example the well itself, a pipeline, a blow out preventer device, a wellhead or any device connected to the wellhead. The leaking device 2 is therefore usually a large device. It may be larger than 5 m. The seafloor 5 is for example at more than 1500 meters deep below the sea surface 4, and now it can be at a very deep depth at more than 2500 meters deep below the sea surface 4. At this depth, the sea water is cold, for example around only 5° C. and at high pressure.
The hydrocarbon fluid may be liquid oil, natural gas, or a mix of them.
The leaking device 2 is leaking a hydrocarbon fluid from an undersea well 3. The hydrocarbon fluid exiting from the undersea may be rather hot, for example above 50° C. However, the environment cold temperature and high pressure may transform the sea water and hydrocarbon fluid into hydrates having a quasi-solid or solid phase. These hydrates can fill and clogged any cavity.
The containment system 1 of present invention is landed and fixed to the seafloor by any means, such as anchoring or heavy weights 29 for compensating the upward Archimedes force applied on the containment system 1 by the hydrocarbon fluid that is lighter than the sea water (lower mass density), or such as piling with one or more piles for fixing the containment system to the seafloor. The seafloor corresponds in the present description to a base level of the containment system 1. The other levels are defined going upwards, in the vertical direction Z towards the sea surface 4.
The containment system 1 of present invention comprises a dome 20 intended to be secured to the seafloor around the leaking device 2 and forming a cavity 21 under said dome 20, said cavity being adapted to completely surround and include the leaking device, and to accumulate the hydrocarbon fluid coming upwardly from the leaking device.
The dome 20 comprises:
The upper opening 22 is a small opening for connecting a pipe, whereas the lower opening is a wide opening for receiving the leaking device.
The dome 20 is preferably fixed and/or sealed to the seafloor.
For example, the dome 20 comprises foot 20c having heavy weights for sealing and securing the dome 20 to the seafloor.
The term “dome” means here a general enclosure or container having a downwardly opened portion so as to be positioned above and to enclose a member. The dome has preferably a lateral portion (like a vertical cylinder) that extends substantially vertically from a base level to an upper level and an upper portion (like a cap) that extends horizontally from the upper end of the lateral portion so as to close the upper portion. The dome has an inner cavity with a volume adapted to receive the member. The lateral portion and/or upper portion may have some holes adapted for specific purposes (fluid exchange between the inner volume and the outside of the dome).
The dome 20 completely surrounds the leaking device 2. In a horizontal plane (XY), the dome 20 has a closed loop shape encompassing the leaking device 2. Said shape may be for example a circle shape, a square shape or any polygonal shape.
The dome 20 has a diameter D20. This outer diameter corresponds to a maximum distance between two internal points of the dome, taken in a horizontal plane at a level near the base level BL. The diameter D20 is for example of 6 meters or more.
The dome 20 is higher than a total height of the leaking device 2. It has a height H20 of approximately 3 meters or more. It completely includes the leaking device 2 (i.e. the part above the base level. All that is under the seafloor is not taken into account as the dome is sealed to the seafloor).
The dome 20 defines an inner dome volume, called the cavity 21. This volume is isolated (not in communication) with the environment sea water. The thermal exchange between the cold sea water and the hydrocarbon fluid is reduced. This first effect reduces the hydrate formation.
The dome 20 is a hollow structure.
The dome 20 according to the invention also comprises:
Advantageously, the lower closing assembly 40 is controlled so as:
For example (first example):
For example (second example), the leaking device is bigger (e.g. when it is a Christmas tree having a blowout preventer):
The dome 20 is landed on the seafloor and contains the leaking device 2. It is a hollow structure having:
The lateral portion 25 has said diameter D20. Its inner diameter is wider than a total wide of the leaking device 2. For example, the inner diameter is of 6 meters or more.
The lateral portion 25 of the dome is downwardly opened so as to surround the leaking device 2.
The dome 20 comprises downwardly a lower opening 26 so as the dome can be landed around the leaking device 2. The lower opening 26 has a size adapted to the size of the leaking device 2 (it must be larger than the leaking device). The dome 20 is then usually between 6 and 12 meters wide. Eventually, the lower opening 26 is between 8 to 10 meters wide. The size of the lower opening 26 is usually adapted (equal) to the diameter D20 of the dome 20.
The upper portion of the dome 20 comprises the upper opening 22 and is adapted to be connected to a pipe 50 for extracting the hydrocarbon fluid from the containment system 1 to a recovery boat 6 at the sea surface 4, so as the hydrocarbon fluid is recovered.
In a vertical plane (XZ), the upper portion 24 of the dome 20 may have a convergent shape from the lateral portion 25 up to the upper opening 22. The dome 20 is a cover that can have advantageously an inverted funnel shape.
The hollow structure of the dome 20 forms a largely opened cavity 21 in the direction to the seafloor. It is positioned above and around the leaking device 2 so as to accumulate the light hydrocarbon fluid.
The cavity 21 accumulates hydrocarbon fluid coming upwardly from the leaking device 2, i.e. oil and/or natural gas. The hydrocarbon fluid fills the upper volume of the cavity, down to an interface level IL.
The dome 20 according to the first embodiment comprises:
The structure 20a is for example composed of rigid interconnected beams. These beams may be may of steel, or any rigid material.
The envelope 20b is sealed to the upper portion 24 of the structure 20a along its periphery end 24a. The envelope 20b is a tube inside the structure 20a that can be compressed by control means 42 or that can be freed to be applied on the inner face of the structure 20a.
The upper portion 24 advantageously comprises the additional outputs and/or valves needed for the operations of the containment system 1.
The envelope 20b advantageously extends downwardly from the upper portion 24, inside the structure 20a and below a lower end 25b of said structure 20a.
A lower end of the envelope 20a is either closed by the lower closing assembly 40 (as seen on left view of
The lower closing assembly 40 is for example a narrowing mechanism that closes up a lower end of the envelope 20b to close it (to close the lower opening 26).
This narrowing mechanism may comprise any driving mechanism to switch the narrowing mechanism from a narrow state wherein the envelope 20b is closed up and an enlarged state wherein the envelope 20b is opened.
Eventually the lower closing assembly 40 is completely disconnected from the envelope and falls down to the seafloor as soon as it is switched to the enlarged state.
The driving mechanism may be controlled by an wire or wireless link, or by a remote operated vehicle (ROV).
An example of the first embodiment is also illustrated on
The modules are for example automatically secured one to the other by fastening means 27 that automatically lock themselves when a second module 202 is set down above a first module 201. The fastening means may be a locking collet, a twist lock system or any known self fastening device.
On these figures, the dome 20 comprises three modules:
Moreover, the dome 20 may comprises thermal insulating material, so as to thermally insulate the cavity 21 from the cold environment of sea water. Ideally, the dome 20 may be manufactured with at least a thermally insulating material, said thermally insulating material preferably having a thermal conductivity lower than 0.1 W·m−1·K−1. The dome 20 may have an overall heat transfer coefficient lower than 2 W·m−2·K−1, and more preferably lower than 1 W·m−2·K−1 based on the overall internal dome wall surface.
The following thermal insulating materials may be used: synthetic material such as Polyurethane (PU) or polystyrene material, or a fibre textile with Polyvinyl chloride (PVC) coating or PU coating, or Alcryn®. The thermal insulating material may be foam, or a gel contained inside a double wall structure.
The thermal insulating material may be inside the structure 20a and/or the envelope 20b. Advantageously, the envelope 20b is the insulating material of the dome 20.
The cavity 21 of the dome 20 (volume inside the envelope 20b in case of present first embodiment) is initially filed by an anti hydrates fluid AHF.
The anti hydrates fluid AHF may be sea water pumped near the sea surface 4 via a pump. The pumped sea water may be used as it, i.e. at the temperature of sea water at the sea surface 4, or heated by additional means.
The anti hydrates fluid AHF may be water, salted water, sea water, oil, gas oil, dead oil, or crude oil.
The anti hydrates fluid AHF may be an alcohol, an ethanol, a methanol, a glycol, an ethylene glycol, a diethylene glycol, or a low-dosage hydrate inhibitor (LDHI).
The anti hydrates fluid AHF may be additionally heated by a fluid heater or not, for preventing to form hydrates. In case of use water, the anti hydrates fluid AHF is preferably heated. The fluid heater may by on a vessel at sea surface.
The term “heated” means having a temperature increase enough to obtain the anti hydrates effect (no formation or no adhesion). For example, the temperature may be increased of at least 10° C., and preferably between 10° C. and 15° C. above a hydrate formation temperature. The hydrate formation temperature is determined by hydrocarbon fluid and the pressure near the leaking device 2 (i.e. the depth). Temperature-pressure curves for every hydrocarbon fluid are known, these curves identifying the phase changes, and more particularly conditions for hydrates formation.
The containment system 1 additionally comprises an output valve 62 connected to the upper output opening 22 and/or pipe 50 for outputting the recovered hydrocarbon fluid to the recovery boat 6. The output valve 62 is located in a vessel or just above the dome 20 or integrated in the dome at the upper output opening 22 (as illustrated on
The containment system 1 may also comprise a exhaust output valve 64 for example situated above the dome 20 near the upper output opening 22. The exhaust output valve 64 is adapted for opening and/or closing the cavity to the sea environment.
The sea output valve 64 is advantageously operated opposite to the output valve 62: the output valve 62 is closed when the exhaust output valve is opened, and the output valve 62 is opened when the exhaust output valve is closed.
The containment system 1 may comprise other output openings and/or pipes for feeding additionally fluids, or for extracting other fluids, liquid or gases from the cavity.
For example, the containment system 1 may comprise a drain valve for purging or limiting the quantity of water inside the cavity 21. Said drain valve might be positioned proximal to the base level BL (seafloor).
Advantageously, the cavity 21 can be used as a phase separator for separating the water and the hydrocarbon fluid, and for separating each phase of the hydrocarbon fluid (oil, gas) so as to extract them separately.
The cavity 21 is a volume storing a quantity of hydrocarbon fluid and absorbing the fluctuations of hydrocarbon fluid flows.
The dome 20 comprises an over pressure valve 23 that extract fluid out of the cavity and into the environment if a pressure difference between the cavity 21 and the environment exceeds a predetermined pressure limit.
The predetermined pressure limit is for example of 10 bars, 20 bars, or 50 bars. This limit has to be determined accordingly with the cavity size and the leaking device flow.
The over pressure valve is for example a ball check valve. The ball check valve comprises a support element, a ball, and a spring that loads the ball to the support element so as to close an opening. The tuning of the spring load is adapted to the predetermined pressure limit.
When installed around the leaking device (right view of
The over pressure valve 23 insures that the pressure inside the cavity is not increasing, and then insuring that the containment system is not destroyed.
The predetermined pressure limit may insure that hydrates formation is prevented.
The second embodiment of the containment system 1 differs in that the dome 20 does not comprise an inner envelope that extends below the structure. The structure of the dome is sealing itself the cavity 21. This containment system 1 comprises a lower closing assembly 40 that is a lower lid or a door mechanism. It also comprises a driving mechanism 41 to disconnect or free the lower closing assembly 40 from the dome 20. The driving mechanism 41 is of any type. As soon as the driving mechanism 41 is activated (arrow F1), the lower closing assembly 40 is separated from the dome 20 and falls for example by gravity effect as shown by the arrow F2.
This example comprises a dome 20 build with three modules 201, 202, and 203.
The third embodiment of the containment system 1 differs in that the lower closing assembly 40 is composed of a door mechanism, comprising one or more doors articulated at a lower end of the dome 20. It comprises a driving mechanism 41 that can be activated (arrow F1) to move the door(s) from closed position to opened position as shown by the arrow F2. The doors opens towards the outside of the containment system as represented on the figure, i.e. the plurality of doors opens as flower petals.
According to a forth embodiment of a containment system 1 of the invention (not shown), similar to the second embodiment as it comprises a cavity 21 that can be completely closed and therefore isolated, the lower closing assembly 40 is composed of a diaphragm mechanism to open and/or close the lower opening 26.
According to a fifth embodiment of a containment system 1 of the invention (not shown), similar to the second embodiment as it comprises a cavity 21 that can be completely closed and therefore isolated. This embodiment differs in that the lower closing assembly 40 is composed of a flexible membrane closing the lower opening. The flexible membrane can be penetrated by the leaking device itself when the containment system 1 is moved so as the leaking device 2 enters the cavity. The membrane is rip apart. However, as the membrane is flexible and expandable, the cavity can be kept substantially sealed.
The method for using or installing the containment system 1 according to the invention is now explained in regards of
Therefore, the containment system 1 according to the invention comprises:
The method according to the invention for using or installing the containment system 1 comprises the following successive preparation steps, illustrated on left view:
a) providing a containment system 1 at sea surface,
b) closing the upper valve 62 and the lower closing assembly 40, and filling the cavity 21 with an anti hydrates fluid.
During step b), the sub-steps may be operated in any order. Preferably, the upper valve 62 and lower closing assembly 40 are closed before filling the cavity 21 with anti hydrates fluid. The heat of this fluid is more protected and preserved from environment.
The method further comprises the following successive opening steps, illustrated on central view:
c) making the containment system 1 going down to the sea floor near the leaking device,
d) connecting a pipe 50 to the upper opening,
e) opening the lower closing assembly 40.
The method further comprises the following successive landing steps, illustrated on right view:
f) moving the containment system so as the leaking device enters the cavity and landing the containment system on the seafloor,
g) opening the upper valve 62 for recovering the hydrocarbon fluid.
Thanks to the above method, the anti hydrates fluid AHF is in contact with the sea water (cold) only during the last landing steps. The entire quantity of anti hydrates fluid AHF can be efficiently prevent hydrates formation.
The time delay for installing the dome 20 above the leaking device 2 can be very short, and the risk of hydrates formation is reduced.
The containment system 1 is advantageously thermally insulated and the anti hydrates fluid AHF is advantageously heated before step b) of filling the cavity 21.
Then, the method can bring a very large quantity of relatively hot anti hydrates fluid AHF just when landing the containment system 1 above the leaking device 2. Such method can be much more efficient than previously known techniques.
After landing, the jet of hydrocarbon fluid from the leaking device 2 is itself heating the mix of fluids contained inside the cavity 21, and hydrates formation is therefore naturally prevented.
The embodiments above are intended to be illustrative and not limiting. Additional embodiments may be within the claims. Although the present invention has been described with reference to particular embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.
Various modifications to the invention may be apparent to one of skill in the art upon reading this disclosure. For example, persons of ordinary skill in the relevant art will recognize that the various features described for the different embodiments of the invention can be suitably combined, un-combined, and re-combined with other features, alone, or in different combinations, within the spirit of the invention. Likewise, the various features described above should all be regarded as example embodiments, rather than limitations to the scope or spirit of the invention. Therefore, the above is not contemplated to limit the scope of the present invention.
The present application is a National Phase entry of PCT Application No. PCT/IB2014/002203, filed Jun. 16, 2014, said application being hereby incorporated by reference herein in its entirety.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2014/002203 | 6/16/2014 | WO | 00 |
