Containment system and a method for using such containment system

1. A 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, wherein the containment system is adapted to be landed at the seafloor corresponding to a base level of the containment system, and

wherein the containment system comprises a dome forming a cavity under said dome, said cavity being adapted to completely surround and include the leaking device, and to accumulate hydrocarbon fluid coming upwardly from the leaking device, said dome comprising at least one upper output opening adapted to extract the hydrocarbon fluid for recovery, and

wherein the containment system is characterised in that it further comprises:

a sensor for measuring an interface level of a fluid interface between hydrocarbon fluid and any other fluid inside the dome,

an output valve connected to the upper output opening for outputting hydrocarbon fluid from the cavity, said output valve being controlled on the basis of the interface level measured by the sensor, and

a control unit that implements a level control law so as to keep the interface level lower or equal to a level of output of the hydrocarbon fluid from the leaking device.

2. The containment system according to claim 1 , wherein the dome comprises:

a first valve for extracting a gas component from the cavity, said first valve being positioned on the dome at a level proximal to a highest level of the dome, and

a second valve for extracting a liquid component from the cavity, said second valve being positioned on the dome at an intermediate level intermediate between the base level and the highest level of the dome.

3. The containment system according to claim 2 , further comprising a control unit that implements a separation control law that controls the first valve so as a gas interface level is lower than the highest level of the dome, and so as a liquid interface level is lower than the intermediate level.

4. The containment system according to claim 1 , wherein the dome comprises an over pressure valve that extract fluid out from the cavity to the environment if a pressure difference between the cavity and the environment exceeds a predetermined pressure limit.

5. The containment system according to claim 1 , wherein the dome comprises an injection device that inputs an injection fluid into the cavity.

6. The containment system according to claim 5 , wherein the injection device comprises a plurality of output ports inside the cavity, said output ports being fed with the injection fluid.

7. The containment system according to claim 5 , wherein the injection fluid comprises one or a combination of the fluid components chosen in the list of an alcohol, an ethanol, a methanol, a glycol, an ethylene glycol, a diethylene glycol, and a low-dosage hydrate inhibitor.

8. A method for using a 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, and

wherein the containment system comprises:

a dome forming a cavity under said dome, said cavity being adapted to completely surround and include the leaking device, and to accumulate hydrocarbon fluid coming upwardly from the leaking device, said dome comprising at least one upper output opening,

a sensor,

an output valve connected to the upper output opening, and

a control unit implementing a level control law,

wherein the method comprises the following successive steps:

a) measuring by the sensor an interface level of a fluid interface between hydrocarbon fluid and any other fluid inside the dome,

b) controlling by the level control law of the control unit the output valve on the basis of the interface level measured by the sensor for outputting hydrocarbon fluid from the cavity

so as to keep the interface level lower or equal to a level of output of the hydrocarbon fluid from the leaking device.

9. The method according to claim 8 , wherein the dome further comprises an injection device that is able to input an injection fluid into the cavity, and

wherein, after landing the containment system at the seafloor and surrounding the leaking device, the method comprises the following steps:

measuring by the sensor a first interface level of a fluid interface between hydrocarbon fluid and injection fluid inside the dome,

controlling the output valve on the basis of the first interface level measured by the sensor for outputting hydrocarbon fluid from the cavity,

measuring by the sensor a second interface level of a fluid interface between injection fluid and water inside the dome, and

controlling the injection device on the basis of the second interface level measured by the sensor for adding injection fluid inside the cavity.

10. The method according to claim 9 , wherein at the upper output opening is controlled so as to keep the first interface level at a level higher than a first predetermined level, said first predetermined level being preferably proximal to the upper output opening.

11. The method according to claim 9 , wherein the injection device is controlled so as to keep the second interface level at a level lower than a second predetermined level, said second predetermined level being preferably proximal to the base level.