Patent Publication Number: US-9416632-B2

Title: Containment system

Description:
RELATED APPLICATIONS 
     The present application is a National Phase entry of PCT Application No. PCT/EP2013/068640, filed Sep. 9, 2013, which claims priority from U.S. Patent Application No. 61/698,250 filed Sep. 7, 2012, said applications being hereby incorporated by reference herein in their entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention concerns a containment system for recovering spilled oil that is leaking under water. 
     BACKGROUND OF THE INVENTION 
     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, 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 huge and inhibitors are also pollution for the environment. 
     The document US 2011/315233 discloses a containment system that comprises: 
     a pipe (main conduit) having a lower end positioned above and substantially near the leaking device and an upper end positioned substantially near the sea surface, said pipe conveying a input fluid that is a mix of components, said components comprising at least water, oil, gas, and hydrate, 
     a treatment facility (tank) fed with the input fluid from the pipe and separating the components of the input fluid. 
     However, the treatment facility of such containment system is a huge containment tank situated bellow the sea surface. Such tank is difficultly feasible. 
     Moreover, the flow of input fluid is so big that such simple gravity separator is inefficient. 
     Hydrates inside such containment system will accumulate inside the tank, and can not dissociate by themselves. 
     SUMMARY OF THE INVENTION 
     One object of the present invention is to provide a containment system that is improved. 
     To this effect, the containment system of present invention is characterised in that: 
     the pipe has a diameter adapted to convey the hydrate from the lower end to the upper end, and 
     the treatment facility comprises a tank connected to the pipe for receiving the input fluid, adapted for dissociation of hydrate component and adapted for providing an output fluid having a concentration in oil higher than the concentration in oil of the input fluid, and the treatment facility comprises a heater device inside the tank for heating the input fluid. 
     Thanks to these features, the hydrate component is dissociated inside the tank into a gas and water. The gas migrates to the top of the tank. The water migrates to the bottom of the tank and mixes to the water component contained inside the input fluid and coming from the sea water sucked from sea by the pipe together with the hydrocarbon fluid outputted from the leaking device. 
     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 diameter of the pipe is larger than 50 cm, and preferably larger than 1 m. 
     According to an aspect of the containment system, the pipe comprises a plurality of holes between the lower end and the upper end. 
     According to an aspect of the containment system, wherein the heater device is a heat exchanger. 
     According to an aspect of the containment system, the heat exchanger uses sea water near the sea surface as a primary fluid. 
     According to an aspect of the containment system, the tank comprises a first cavity receiving the input fluid from the pipe, a second cavity for separating liquid components of the input fluid, and a third cavity for extracting an output fluid, and wherein: 
     a first wall separates the first cavity and the second cavity said first wall comprising a plurality of lateral holes to allow transfer of input fluid to the second cavity and to cancel flow turbulences, and 
     a second wall separates the second cavity and the third cavity, said second wall having an intermediate opening for transferring oil component to the third cavity. 
     According to an aspect of the containment system, it further comprises an output separator receiving the output fluid from the tank, the output separator comprising an output heater that heats the output fluid to a temperature higher than 35° C. for separating remaining gas and water from the output fluid. 
     According to an aspect of the containment system, the output heater is an oil burner or gas burner or a hot heating medium heater or an electric heater. 
     According to an aspect of the containment system, it further comprises a dome having an upper output opening connected to the lower end of the pipe, said dome forming a cavity adapted to accumulate hydrocarbon fluid coming upwardly from the leaking device for recovering said hydrocarbon fluid. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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: 
         FIG. 1  is a schematic view of a vertical cut of containment system according to a first embodiment of the invention; 
         FIG. 2  is a schematic view of a vertical cut of containment system according to a second embodiment of the invention, said view showing only a lower portion of the system, all the other parts being identical to the first embodiment. 
     
    
    
     DETAILED DESCRIPTION OF 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. 
     As shown on  FIG. 1 , a containment system  1  according to present invention 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 seafloor  5  is for example at more than 1500 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 a subsea well  3 . The hydrocarbon fluid exiting from the subsea may be rather hot, for example above 50° C. However, the environment cold temperature and high pressure may transform a quantity of sea water and hydrocarbon fluid into hydrates having a quasi-solid or solid phase. These hydrates can fill and clog any small cavity or pipe. 
     The containment system  1  of present invention can be fixed to the seafloor by any means, such as anchoring or heavy weights  29  for stability of the containment system  1 . 
     The containment system  1  of present invention comprises at least: 
     a pipe  50  having a lower end  50   a  positioned above and substantially near the leaking device  2  and an upper end  50   b  positioned substantially near the sea surface  5 , said pipe conveying an input fluid from the lower end to the upper end, and 
     a treatment facility  70  fed with the input fluid from the pipe  50  and separating the components of the input fluid. 
     The input fluid is a mix of components: sea water that is sucked by the pipe, hydrocarbon fluid (oil, gas), and hydrates that are formed at the output of the leaking device. 
     The pipe  50  has a diameter adapted for conveying the hydrate component from the lower  50   a  end to the upper end  50   b  of the pipe without clogging the pipe. Therefore, the diameter of the pipe is preferably enough wide. 
     For example, the diameter is higher than 50 cm, and preferably higher than 1 m. In use, the diameter is lower than 3 m for the ease of installation. 
     The pipe  50  may be rigid or flexible. 
     In case of a rigid pipe, it may be made of any kind of steel or polymer material. 
     In case of flexible pipe, it may be made of polymer or rubber material. It may also include reinforcing fibbers or fabric as it well known. 
     The pipe  50  may comprise a plurality of holes  51  situated between the lower end  50   a  and upper end  50   b  of said pipe  50 . These holes may be regularly spaced along the pipe. 
     An added quantity of sea water is sucked by these holes inside the pipe  50 . The hydrocarbon fluid from the leaking device  2  is therefore guided and transported by the pipe and the sea water to the upper end  50   b.    
     Thanks to these holes, the pipe  50  does not suffer from differential pressure, and will not collapse. The pipe  50  can be more easily a flexible pipe, or a rigid pipe having a lower thickness. 
     The treatment facility  70  comprises a tank  71 . A tank is a large structure having an inner cavity, said tank being adapted to be filled with a fluid. The fluid is contained hermetically inside the inner cavity. 
     The tank  71  is connected to the upper end  50   b  of the pipe for receiving the input fluid from it. The tank  71  is adapted for dissociation of the solid hydrate component into gas and water, and for providing an output fluid, the output fluid having a concentration in oil higher than the concentration in oil of the input fluid from the pipe  50 . 
     The treatment facility  70  is separating the components of the input fluid by gravity effect: the components with lower densities are accumulated upwards (positive Z direction) inside the treatment facility  70  (tank), whereas the components with higher densities are accumulated downwards (negative Z direction) inside the treatment facility  70 . 
     In case of the considered input fluid, the component will tend to sort inside the treatment facility in the following order according to the Z direction (from bottom to top): water, hydrates, oil and gas. 
     The tank  71  may be built according to the following arrangements: It is divided into three adjacent cavities (or compartments): a first cavity C 1 , a second cavity C 2  and a third cavity C 3 . A first wall  75  inside the tank  71  is the limit between the first and second cavity. A second wall  76  inside the tank  71  is the limit between the second and third cavity. 
     Both first and second walls  75 ,  76  comprise upper openings so as the gas component may be accumulated inside the upper portion of the three cavities of the tank  71 . A gas output  73  may control the extraction of gas from the tank  71 . A gas compressing facility may be provided for compressing the gas and reduce its volume (for example by liquefaction). Otherwise, the gas output  73  may be connected to a gas disposal device. an optional gas compressing facility may be provided for compressing the gas and reduce its volume (for example by liquefaction). 
     A surface S 1  may delimit the interface between the gas component inside the tank and the other components. 
     The first wall  75  comprises openings along its entire height so as all the components in the input fluid are transferred from the first cavity C 1  to the second cavity C 2 . The first cavity C 1  is an input cavity for the input fluid. The flow of input fluid is stabilised inside the first cavity, and turbulences coming from the input fluid do not interfere with the fluid contained inside the second cavity C 2 . The fluid in the cavity C 2  can separate its components according to each component density. 
     The second cavity C 2  contains the following components from the bottom to the top: water, hydrates, oil, and gas. 
     The second wall  76  comprises an intermediate opening  76   a  situated below the surface S 1  and near said surface S 1  so as the lighter liquid component (oil) is mainly transferred from the second cavity C 2  to the third cavity C 3  (i.e. oil). The height of the intermediate opening  76   a  may be predetermined or adapted to the flow of input fluid. In last case, the second wall  76  comprises means to modify the position of the intermediate opening  76   a  according to the vertical direction Z. 
     The lower portion of the third cavity C 3  therefore mainly contains the oil component (the output fluid) that can be transferred to a boat  6  via a transfer pipe and pump  80 . The output fluid is a fluid having a concentration in oil that is higher than the concentration in oil of the input fluid from the pipe  50 . 
     At the bottom of the second cavity C 2 , the water component can be extracted by a water output  74 . The extracted water may be outputted to the sea if the quality (oil content) is acceptable. Otherwise, a treatment step is necessary before disposal to the sea. 
     The first and second cavity C 1 , C 2  may includes a heater device  72  that heats the liquid components of the input fluid. The heater device  72  is positioned inside the tank  71  bellow the surface S 1  (bellow the predetermined interface level). 
     Heating the input fluid accelerates the hydrates dissociation and the separation of all the components in the input fluid. 
     The heater device  72  is preferably a heat exchanger immerged inside the liquid components of the tank  71  (bellow the surface S 1 ). It may comprise a first part inside the first cavity C 1  and a second part inside the second cavity C 2 . It is for example composed of a circuit of tubes canalising a hot primary fluid (heating fluid medium) inside the tank  71 , the input fluid being the secondary fluid that must be heated. It is also for example composed of large plates for exchanging heat between the heat exchanger and the input fluid. The heater device  72  is very large. It occupies lots of space inside the first and second cavity. Even if pressure and temperature conditions are adequate, hydrates can not dissociate into gas and water without heating as this dissociation is an endothermic reaction. 
     The heater device  72  may use sea water near the sea surface  4  a relatively hot primary fluid (between 15° C. and 25° C.) to dissociate hydrates into gas and water at atmospheric pressure. The sea water at sea surface is an inexpensive source of heat for hydrates dissociation at atmospheric pressure. 
     The treatment facility  70  may preferably comprise an output separator  81  connected to the transfer pipe  80 , and therefore fed with the output fluid from the tank  71 . 
     This output separator  81  comprises an output heater that heats the output fluid to a temperature higher than 30° C., so as remaining gas and water contained inside the output fluid can be evacuated. For example, remained gas is extracted via a gas output  82 , and remained water is extracted via a water output  83 . 
     The output heater is for example an oil burner or a gas burner or a hot heating medium heater or an electric heater. 
     A quantity of gas or oil (output fluid) extracted by the tank  71  may be used by the output heater for heating the output heater and the output fluid. 
     The recovering fluid (degassed and dehydrated) can be then transferred to a boat  6  via a transfer pipe  90 . The recovering fluid is a fluid having a concentration in oil that is higher than the concentration in oil of the output fluid in the transfer pipe  80 . 
     The containment system  1  of present invention operates as follows. 
     The pipe  50  is sucking the hydrocarbon fluid leaking from the leaking device  2 . This fluid is going up to the treatment facility  70  by gravity effect and differential pressure effect. The pipe  50  is sucking a huge quantity of cold sea water, the hydrocarbon fluid and the hydrates that are formed at the sea depth. The sea water may represent more than 95% of the volume of fluid transported inside the pipe  50 . There is no clogging problem. Only a difficulty of separating the huge quantity of input fluid in the tank at the flow rate as the leaking device  2  may leak up to 100,000 barrels per day. 
     The dissociation of hydrates is an endothermic reaction. The hydrates can not be dissociated inside the pipe, nor inside the tank  71  without the heating from the heater device  72 . The heater device  72  situated inside the tank  71  allows an efficient dissociation of hydrates. 
     Hydrates are dissociated inside the first and second cavity C 1 , C 2  of the tank  71 . The upper portion of the tank  71  recovers the light gas component. The third cavity C 3  recovers the light liquid component: the oil component. The water component is extracted back to see at the lower portion of the second cavity C 2 . 
     In  FIG. 2 , a second embodiment is shown. In this embodiment, the containment system  1  further comprises a dome  20  under the lower end  50   a  of the pipe  50 . 
     The dome  20  comprises an upper output opening  22  connected to the lower end of the pipe to extract an input fluid comprising the hydrocarbon fluid for recovering and, unfortunately, a quantity of sea water and hydrates. 
     The dome  20  is preferably fixed to the seafloor. 
     For example, the dome  20  comprises foot  20   c  having heavy weights for maintaining and securing the dome  20  to the seafloor. 
     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 an diameter D 20 . This outer diameter corresponds to a maximum distance between two internal points of the dome, taken in a horizontal plane. The diameter D 20  is for example of 6 meters or more. The typical size of a wellhead (a wellhead that might be included inside the cavity of the dome in case of accident) are for example: a length between 5 and 7 m, a width between 4 and 6 m, and a height between 5 and 7 m. 
     The dome  20  may be 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 . 
     The dome  20  defines an inner dome volume, called the cavity  21 . 
     The dome  20  is a hollow structure having: 
     an upper portion  24  extending in a radial direction to an outer peripheral end  24   a , said radial direction being perpendicular to the vertical direction AX (equal to direction Z on the figure), and 
     a lateral portion  25  extending from the upper portion  24  downwardly between an upper end  25   a  and a lower end  25   b , said lower end  25   b  comprising for example the foot  20   c.    
     The lateral portion  25  has said diameter D 20 . 
     The lateral portion  25  of the dome is downwardly opened so as to surround the leaking device  2 . 
     The upper output opening  22  having a small diameter compared to the dome diameter. Said upper output opening is connected to the pipe  50  by any means for extracting the hydrocarbon fluid. Advantageously, fast and automatic and self centering means are used. The dome  20  can be installed on the seafloor  5  before the installation of the pipe  50 . 
     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 output 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 in relation to a base level of the seafloor  5 . 
     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.