Gravity separator, and a method for separating a mixture containing water, oil, and gas

1. A gravity separator comprising a vessel within which a mixture containing water, oil, and gas can separate under gravity to form vertically discrete oil and water layers and a gas phase, the vessel including

an inlet duct communicating with a vessel entrance for the mixture containing water, oil, and gas;

an outlet for water;

an outlet for oil; and

an outlet for gas,

said inlet duct (i) including a gas injector spaced apart from the vessel entrance by a spacing in a range of from 0.05 to 2.00 m, and (ii) extending from above the vessel downward through the vessel to the vessel entrance.

2. The gravity separator according to claim 1 , further comprising a conduit that supplies a gaseous medium to the gas injector by recirculating gas from the gravity separator to the gas injector.

3. The gravity separator according to claim 2 , wherein the conduit supplying the recirculated gas to the gas injector is connected with an interior of the gravity separator at an upper part thereof.

4. The gravity separator according to claim 2 , wherein the conduit supplying the recirculated gas to the gas injector is a sole supply of injection gas to the gas injector.

5. The gravity separator according to claim 1 , further comprising a mixer located in the inlet duct between the gas injector and the vessel entrance.

6. The gravity separator according to claim 5 , wherein the mixer is a static mixer.

7. The gravity separator according to claim 5 , wherein the mixer is located in a section of the inlet duct extending within the vessel.

8. A method of separating a mixture containing water, oil, and gas comprising the steps of:

conducting the mixture via an inlet duct and a vessel entrance into a vessel, the inlet duct extending from above the vessel downward through the vessel to the vessel entrance;

injecting a volume of a gaseous medium in a range of from 0.01-1.9 Sm 3 of the gaseous medium per 1 m 3 of the mixture into the mixture flowing through the inlet duct, the gaseous medium being injected through a gas injector spaced apart from the vessel entrance by a distance of from 0.05 to 2.00 m;

allowing the mixture in the vessel to separate into a water phase, an oil phase, and a gas phase under gravity; and

taking out the water phase via an outlet for water, taking out the oil phase via an outlet for oil, and taking out the gas via an outlet for gas.

9. The method according to claim 8 , wherein 0.04-1.6 Sm 3 of the gaseous medium per 1 m 3 of the mixture is injected into the mixture in the inlet duct.

10. The method according to claim 9 , wherein 0.05-0.40 Sm 3 of the gaseous medium per 1 m 3 of the mixture is injected into the mixture in the inlet duct.

11. The method according to claim 9 , wherein 0.05-0.15 Sm 3 of the gaseous medium per 1 m 3 of the mixture is injected into the mixture in the inlet duct.

12. The method according to claim 9 , wherein 0.08-0.12 Sm 3 of the gaseous medium per 1 m 3 of the mixture is injected into the mixture in the inlet duct.

13. The method according to claim 9 , wherein the mixture containing water, oil, and gas is subjected to injection with one or more separation aids.

14. The method according to claim 9 , wherein the gaseous medium is a gas collected from the vessel and injected in the inlet duct.