Horizontal liquid/gas separation device, and separation method, in particular for the liquid and gaseous phases of a crude oil

A method of separating liquid and gaseous phases of a fluid using a structure resting on the sea bottom and supporting

• a) a plurality of first separator pipes extending from a horizontally-extending cylindrical first tank of elongate shape and circular section, the first separator pipes being connected thereto at their upstream ends, said first separator pipes being inclined at an angle α lying in the range 1° to 5° relative to the horizontal with a gentle downward slope from said first tank towards a substantially horizontal first cylindrical manifold to which said first pipes are connected downstream, said first tank being fed by at least one fluid feed pipe, and said first manifold being connected to a first liquid evacuation pipe of downward slope;
• b) a plurality of second separator pipes disposed above said first pipes from and above said first tank with a gentle rising slope from said first tank towards a substantially horizontal second cylindrical manifold, said second separator pipes being inclined relative to the horizontal at an angle β greater than α, said second manifold connected to a first gas evacuation pipe;
• c) a plurality of vertical link third pipes between each said first separator pipe and each said second separator pipe;
• and
• d) a system of actuators enabling the inclination of said first and second separator pipes to be adjusted accurately and enabling said first tank and said first and second manifolds to be positioned horizontally;
• wherein the following steps are performed:
• 1) sending the fluid via a fluid feed pipe to said first tank;
• 2) allowing the at least partially degassed liquid to flow from said first tank via said first separator pipe in order to be further degassed and to move down towards said first manifold, and then to said first liquid evacuation pipe;
• 3) allowing the gaseous phase to rise and flow via said second separator pipes towards said second manifold, and then towards said first gas evacuation pipe in order to allow additional separation of any residual liquid contained in the gaseous phase prior to being evacuated via a second evacuation pipe;
• 4) allowing the gas phase from the first separator pipe to rise through said vertical link third pipes and flow via said second separator pipes towards said second manifold and then towards said first gas evacuation pipe and a second gas evacuation pipe;
• 5) allowing the liquid coming from gas separation in said second separator pipes, said second manifold, and said first gas evacuation pipe to flow towards said first manifold by passing via said first tank or said vertical link third pipes prior to rejoining said first liquid evacuation pipe;
• 6) recovering the substantially degassed liquid phase from the bottom end of said first liquid evacuation pipe and taking it via a second liquid evacuation pipe that is taken to the surface or sent to a liquid separator device in order to separate the different liquids possibly contained therein;
• and
• 7) recovering the gas phase substantially separated from said liquid from the bottom end of said second gas evacuation pipe.

A method of placing a separator device on the sea bottom, the device for separating liquid and gaseous phases of a fluid, wherein the device comprises a structure resting on the sea bottom and supporting:

• a) a plurality of first separator pipes extending from a horizontally-extending cylindrical first tank of elongate shape and circular section, the first separator pipes being connected thereto at their upstream ends, said first separator pipes being inclined at an angle α lying in the range 1° to 5° relative to the horizontal with a gentle downward slope from said first tank towards a substantially horizontal first cylindrical manifold to which said first pipes are connected downstream, said first tank being fed by at least one fluid feed pipe, and said first manifold being connected to a first liquid evacuation pipe of downward slope;
• b) a plurality of second separator pipes disposed above said first pipes from and above said first tank with a gentle rising slope from said first tank towards a substantially horizontal second cylindrical manifold, said second separator pipes being inclined relative to the horizontal at an angle β greater than α, said second manifold being connected to a first gas evacuation pipe;
• c) a plurality of vertical link third pipes between each said first separator pipe and each said second separator pipe;
• and
• d) a system of actuators enabling the inclination of said first and second separator pipes to be adjusted accurately and enabling said first tank and said first and second manifolds to be positioned horizontally;
• wherein the following steps are performed:
• 1) lowering said separator device from the surface and placing it on the sea bottom;
• and
• 2) adjusting the horizontality of said first tank and of said first and second manifolds, and the inclination of said first and second separator pipes by actuating said system of actuators.