A Continuous Through-Flow Settling Vessel, and a Method of Adaptive Separation of a Mixture from Gas and/or Oil Exploration

Abstract

A continuous through-flow settling vessel for adaptive separation of a mixture from gas and/or oil exploration or production, said mixture comprising a varying mixture of liquid and gaseous phases, wherein the vessel is provided with: an inlet for a mixture, and a gas outlet, a water outlet and an oil outlet, the outlets being provided distant from the inlet, and the oil outlet being downstream of the water outlet, a weir downstream of the water outlet and upstream of the oil outlet, which weir functions as a barrier to a free through-flow in the vessel of the liquid phase which comprises a water phase and an oil phase, which phases are separated from each other by settling, the weir having a height lower than the gas outlet, and wherein the vessel is additionally provided with:—an oil draining means capable of controllably draining oil phase from the vessel upstream of the weir, said means being provided at a level below the weir height and above the water phase that is present during operation of the vessel. Method of adaptive separation of a mixture from gas and/or oil exploration or production, said mixture comprising a varying mixture of liquid and gaseous phases, wherein the mixture is introduced into a continuous through-flow settling vessel.

Claims

1-15. (canceled)

16. A Method for adaptive separation of a mixture from gas and/or oil exploration or production, said mixture comprising a varying mixture of liquid and gaseous phases, wherein the mixture is introduced into a continuous through-flow settling vessel, said vessel provided with: an inlet for the mixture, and a gas outlet, a water outlet and an oil outlet, the outlets being provided distant from the inlet, and the oil outlet being downstream of the water outlet, a weir downstream of the water outlet and upstream of the oil outlet, which weir functions as a barrier to a free through-flow in the vessel of the liquid phase which comprises a water phase and an oil phase, which phases are separated from each other by settling, the weir having a height lower than the gas outlet, and wherein the normal method of separation involves the continuous controlling of the velocity of flow through the inlet and outlets of the vessel, so that a liquid level of the liquid phase in the vessel is maintained during operation at or below a threshold value between the height of the weir and the height of the gas outlet, and wherein the adaptive separation comprises the steps of: determining the presence in a pipeline of an inhomogeneity in the mixture which is mainly liquid, also referred to as a slug flow, before it enters the inlet of the vessel; during a phase A which precedes the slug flow entering the vessel: lowering the liquid level of the liquid phase in the vessel upstream of the weir to or below an adapted height lower than the threshold value; and during a subsequent phase B which includes the slug flow entering the vessel: allowing the liquid level to rise above the adapted height in the vessel upstream of the weir, and subsequently maintaining the liquid level at or below the threshold value.

17. The method according to claim 16, wherein during phase A, the volume of oil phase in the vessel upstream of the weir is reduced.

18. The method according to claim 16, including the use of an oil draining means capable of draining liquid phase from the vessel upstream of the weir and below the weir height.

19. The method according to claims 16, wherein during phase A, the volume of water phase upstream of the weir is reduced.

20. The method according to one of the claims 16, wherein the normal method of separation additionally involves the water level of the water phase in the vessel upstream of the weir to be maintained during operation at or below a water threshold value.

21. The method according to claim 20, wherein during phase A, the water level of the water phase in the vessel upstream of the weir is maintained at or below value which is lower than the water threshold value.

22. The method according to claim 16, wherein the continuous through-flow settling vessel for adaptive separation of a mixture from gas and/or oil exploration or production is additionally provided with: an oil draining means capable of controllably draining oil phase from the vessel upstream of the weir, said means being provided at a level below the weir height and above the water phase that is present during operation of the vessel, wherein in phase A the oil draining means are in an active mode for draining, and in phase B these means are not in an active mode for draining.

23. The method according to claim 22, wherein the oil draining means of the continuous through-flow settling vessel comprises at least one duct with a controllable valve that is in fluid communication with the upstream side of the weir.

24. The method according to claim 23, wherein the duct extends through the weir and is in fluid communication with the upstream and downstream side of the weir.

25. The method according to claim 23, wherein the entry side of the duct is provided in the vessel at a height between 0.10 and 0.75 of the weir height.

26. The method according to claim 23, wherein the duct merges with the oil outlet outside of the vessel, or alternatively, is in fluid communication with the vessel downstream of the weir.

27. The method according to claim 26, wherein the controlling means are adaptable to allow the liquid level upstream of the weir to decline to or below an adaptive height which is lower than the threshold value.

28. The method according to claim 23, which comprises controlling means for controlling the velocity of flow through the inlet and outlets of the vessel, so that a liquid level of the liquid phase in the vessel is maintained at or below a threshold value between the height of the weir and the height of the gas outlet.

29. The method according to claim 28, wherein the controlling means allow temporarily the increase of outflow using the water outlet, the oil outlet, and/or the oil draining means in order to decline the liquid level to or below the adaptive height upstream of the weir.

Description

[0059] The invention is further explained with reference to the appended drawings, wherein:

[0060] FIG. 1 is a schematic representation of a preferred embodiment of the continuous through-flow settling vessel according to the invention, in cross-section and during normal operation;

[0061] FIGS. 2A and 2B show the same vessel as FIG. 1, during different phases of operation;

[0062] FIGS. 3A and 3B show two preferred embodiments of an additional duct according to the invention;

[0063] FIG. 3C shows a third preferred embodiment of an additional duct according to the invention.

[0064] FIG. 1 shows a continuous through-flow settling vessel 1, made out of a closed cylindrical wall 2, having an inlet 3 for a mixture, a gas outlet 5, a water outlet 7 and an oil outlet 8. The outlets are all provided with a controllable valve (not shown). The direction of the mixture inside the vessel is from left to right. A weir 10 is placed inside the vessel the top of which is below the high liquid level 14 which is the upper threshold value for liquid inside the vessel. Upstream of the weir 10, a volume of separated liquid is present consisting of an oil phase 16 and a water phase 20. The interface 18 marks the water level upstream of the weir. The surface 12 marks the liquid level inside the vessel which is the same at the upstream side and the downstream side of the weir 10. FIG. 1 shows the vessel during normal operation, wherein controlling means (not pictured) coordinate the exit flow through the outlets 5, 7, 8 by virtue of the respective valves, so as to accomplish a steady state wherein a large volume of liquid upstream of the weir is allowed to settle and separate into an oil and a water fraction.

[0065] FIG. 2A shows the same vessel 1, during a phase A which precedes the slug flow entering the vessel, wherein the liquid level 12 of the liquid phase in the vessel upstream of the weir is lowered to or below an adapted height 22 which is lower than the threshold value 14. The lowering is accomplished by increasing the exit flow via the water and oil outlets 7,8, and also via an additional duct which is in fluid communication with the upstream side of the weir. The additional duct is provided at the adapted height 22, and is shown in various forms in FIG. 3A-C. In phase A, also the water level 18 is lowered in comparison to the normal operation shown in FIG. 1.

[0066] FIG. 2B shows the phase B, which follows after phase A, wherein the slug flow has fully entered the vessel. The liquid level 12 is allowed to rise above the adapted height 22 in the vessel upstream of the weir, and is subsequently maintained at or below the threshold value 14. In this phase B, the additional duct is closed off. In the situation shown, there is not yet an overflow of liquid from the slug flow that spills over the weir 10 and reaches the side downstream of the weir. Therefore the liquid level of the oil volume 30 at the downstream side of the weir is lower in comparison to the upstream side.

[0067] FIG. 3A shows the vessel 1 corresponding to the vessel of FIG. 2A, which is provided with a first type of an additional duct 50, which is a bypass channel outside the vessel which is in fluid communication with the upstream and downstream side of the weir 10. The additional duct is provided with a controllable valve 9. All other outlets 5, 7, 8 are also provided with valves 9. The height of the liquid phase 12 corresponds with the height of the entry side 52 of the additional duct 50, which is the adapted height according to the invention.

[0068] FIG. 3B shows the vessel 1 corresponding to the vessel of FIG. 2A, which is provided with a second type of an additional duct 60, which is an auxiliary outlet from the vessel which is in fluid communication with the upstream side of the weir 10. The auxiliary outlet is provided with a controllable valve 9. The height of the liquid phase 12 corresponds with the height of the entry side 62 of the additional duct 60, which is the adapted height according to the invention. The auxiliary outlet merges with the oil outlet 8 downstream of the valves 9.

[0069] FIG. 3C shows schematically the right hand side of the vessel as shown in FIG. 2AB, which is provided with a third type of an additional duct. The weir 10 is provided with a an additional duct 40 through the weir which is in fluid communication with the upstream and downstream side of the weir, and is provided with a controllable valve 42.

[0070] The additional duct 40 is provided at an adapted height 22.

[0071] The valve 42 is closed off, so that a rise of the liquid level upstream of the weir is accomplished.

[0072] For all the above three types of additional ducts 40, 50 and 60, it is possible by opening of the respective valve 9 or 42, respectively of the additional duct, to achieve a lowering of the liquid level upstream of the weir, in anticipation of a slug flow having a substantially larger volume of liquid, which is accommodated for by the invention.