Method and System for Separating Oil Well Substances With Means for Capturing and Removing Liquid From a Gas Outlet Pipeline

Abstract

A method and system for separating oil well substances provided with means for capturing liquid in separated gas for preventing liquid carry over in separated gas as well as providing a liquid lock preventing gas carry over.

Claims

1-17. (canceled)

18. A method for separating oil well substances, comprising: providing a system that includes: (i) a slug suppression and gas removal unit (100) arranged to a well, and (ii) an inclined oil and water separator system (10) connect to the slug suppression and gas removal unit (100) via a horizontal pipeline (300), capturing liquid in a gas outlet pipeline (130) of the slug suppression and gas removal unit (100), and removing the captured liquid from the gas outlet pipeline (130).

19. The method according to claim 18, comprising using a helical liquid collector (500) interior in the gas outlet pipeline (110) to capture creeping liquid film in the gas outlet pipeline (130).

20. The method according to claim 18, comprising removing the captured liquid from the gas outlet pipeline (130) via a substantially vertically extending drainpipe (510), and adding the captured liquid to the horizontal pipeline (300).

21. The method according to claim 18, comprising providing a liquid lock to avoid free gas carry under between the slug suppression and gas removal unit (100) and the inclined oil and water separator system (10).

22. The method according to claim 21, comprising providing and maintaining the liquid lock by arranging liquid level (400) interaction between the slug suppression and gas removal unit (100) and the inclined oil and water separator system (10), and the substantially vertically extending drainpipe (510) proximate an equal height.

23. The method according to claim 22, comprising using an oil and water separator system (10) with at least two inclined tubular oil and water separators (11a-11d) formed by an elongated outer tube (50); arranging an elongated inner tube (40) in the elongated outer tube (50), wherein oil well substances are introduced into an end of the inner tube (40) via a feed section passing through the outer tube (50) and into the inner tube (40), and the inner tube (40) comprises multiple holes or slots (44) arranged in a longitudinal direction; and arranging an interface (600) between oil and water in the respective inclined tubular oil and water separator (11a-11d) at approximately 50-70% of a length (L) of the tubular oil and water separator (11a-11d), the side of the interface defining an inlet end of the respective inclined tubular oil and water separator (11a-11d).

24. The method according to claim 23, comprising arranging the location of the first hole or slots (44) toward the inlet end of the inclined tubular oil and water separator (11a-d) at least at the water side starting at a position approximately ⅓ of the overall length (L) of the inclined tubular oil and water separator (11a-11d).

25. The method according to claim 22, comprising arranging the liquid level (400) at a top of the inclined tubular oil and water separator system (10).

26. The method according to claim 18, comprising using liquid velocity in the large diameter pipeline (300) as an ejector for captured liquid and maintaining the liquid level in the vertically extending drainpipe (510).

27. A system for separating oil well substances, comprising: a slug suppression and gas removal unit (100) arranged to a well and an inclined oil and water separator system (10); wherein the slug suppression and gas removal unit (100) is connected to the inclined separator system (10) via a substantially horizontal pipeline (300), and an apparatus (500) for capturing liquid is arranged interior in a gas outlet pipeline (130) of the slug and gas removal unit (100) for capturing liquid in the gas outlet pipeline (130).

28. The system according to claim 27, wherein the apparatus (500) for capturing liquid is a helical liquid collector adapted for capturing creeping liquid film in the gas outlet pipeline (130).

29. The system according to claim 27, comprising a substantially vertically extending drainpipe (510) extending between the gas outlet pipeline (130) and the substantially horizontal pipeline (300), the substantially vertically extending drainpipe (510) being aligned with a corresponding opening (121) in a lower part of the gas outlet pipeline (130) and a corresponding opening (301) in an upper part of the horizontal large diameter pipeline (300), wherein the helical liquid collector (500) ends in the opening (121) of the lower part of the gas outlet pipeline (130).

30. The system according to claim 29, wherein the helical liquid collector (500) is fixed to an interior surface of the gas outlet pipeline (130), extends a distance (D) in a longitudinal direction of the gas outlet pipeline (130) and protrudes interior to the gas outlet pipeline (110) at a height (H) from the interior surface of the gas outlet pipeline (110).

31. The system according to claim 27, wherein the helical liquid collector (500) is fixed to an interior surface of the gas outlet pipeline (130), extends a distance (D) in a longitudinal direction of the gas outlet pipeline (130) and protrudes interior to the gas outlet pipeline (110) at a height (H) from the interior surface of the gas outlet pipeline (110).

32. The system according to claim 30, wherein the helical liquid collector (500) extends at least 360 degrees in a circumferential direction of the gas outlet pipeline (130) over the distance (D).

33. The system according to claim 32, wherein the helical liquid collector (500) extends within a range of 500-600 degrees in a circumferential direction of the gas outlet pipeline (130) over the distance (D).

34. The system according to claim 29, wherein the slug suppression and gas removal unit (100), the inclined oil and water separator system (10) and the vertically extending drainpipe (510) are arranged such that a liquid level (400) interaction between them is at a substantially equal height, thereby providing a liquid lock avoiding free gas carry under between the gas removal unit (100), inclined oil and water separator system (10) and vertically extending drainpipe (510).

35. The system according to claim 30, wherein the slug suppression and gas removal unit (100), the inclined oil and water separator system (10) and the vertically extending drainpipe (510) are arranged such that a liquid level (400) interaction between them is at a substantially equal height, thereby providing a liquid lock avoiding free gas carry under between the gas removal unit (100), inclined oil and water separator system (10) and vertically extending drainpipe (510).

36. The system according to claim 27, wherein the oil and water separator system (10) comprises at least two inclined tubular oil and water separators (11a-11d) formed by an elongated outer tube (50) with an elongated inner tube (40) arranged therein, and oil well substances are introduced into an end of the inner tube (40) via a feed section passing through the outer tube (50) and into the inner tube (40), the inner tube (40) comprising multiple holes or slots (44) arranged in a longitudinal direction, an interface (600) between oil and water in the respective inclined tubular oil and water separator (11a-11d) is located at a position approximately 50-70% of overall length (L) of the inclined tubular oil and water separator (11a-11d), the side of the interface defining an inlet end of the respective inclined tubular oil and water separator (11a-11d).

37. The system according to claim 36, wherein the location of the first hole or slots (44) toward the inlet end of the inclined tubular oil and water separator (11a-d) at least at the water side start at a position approximately ⅓ of the overall length (L) of the inclined tubular oil and water separator (11a-11d).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The present invention will below be described in further detail with references to the attached drawings, where:

[0052] FIG. 1 is a principle drawing of an inclined separator system according to prior art,

[0053] FIG. 2 is principle drawing showing the interior of an inclined tubular separator of the inclined separator system in FIG. 1,

[0054] FIG. 3 is a principle drawing of an inclined oil and water separator system according to prior art,

[0055] FIG. 4 is a principle drawing of a system according to the disclosure,

[0056] FIG. 5 is a principle drawing of an apparatus for capturing liquid according to the disclosure,

[0057] FIG. 6 is a principle drawing of the described effects in a horizontal pipe/pipeline according to prior art, and

[0058] FIG. 7 is a principle drawing of an inclined tubular oil and water separator according to prior art showing details of holes or slots, and oil and water interface.

DETAILED DESCRIPTION

[0059] Reference is first made to FIGS. 1 and 2 which are principle drawings of a separator system according to prior art, as described in EP2981341 and EP2934714, both in the name of the applicant, the disclosure of this incorporated herein by reference, illustrated by a separator system comprising four interconnected inclined tubular separators 11a-d using gravity as the separating force.

[0060] Each inclined tubular separator 11a-d has a respective inlet 12a-d in a lower section of the inclined tubular separator 11a-d, and a respective outlet 13a-d also located in the lower/bottom section of the inclined tubular separator 11a-d. A respective outlet 14a-d is located in an upper section of the inclined tubular separator 11a-d.

[0061] The separator system is supplied with fluid from an oil well (not shown) by a pipe 15 and via an input manifold 16 which distributes the fluid to the respective inclined tubular separators 11a-d and interconnecting the inclined tubular separators 11a-d in a parallel fashion, or in series, or in a combination of parallel and serial configurations. There is further arranged a first output manifold section 17 interconnecting the outlets 13a-d in a parallel fashion, or in series, or in a combination of parallel and serial configurations to an outlet pipe 18.

[0062] There is further arranged a second output manifold section 19 interconnecting the outlets 14a-d from the inclined tubular separators 11a-d, in a parallel fashion, or in series, or in a combination of parallel and serial configurations to an outlet pipe 20, with respect to the number of phases the separator system is adapted and manufactured to separate.

[0063] In this illustrated example, three of the inclined tubular separators 11b-d are interconnected such that the three outlet openings 14b-d of these in the upper section of the inclined separator system from the three respective tubular separators 11b-d are connected together to a common outlet pipe 20, while one outlet 14a in the upper section from a fourth inclined tubular separator 11a is connected to an outlet pipe 21.

[0064] The lower outlet 12b-d of the inclined tubular separators 11b-d are connected together to the outlet pipe 18, while the lower outlet 12a of the inclined tubular separators 11a is connected to the respective inlets 12a-d of the inclined tubular separators 11b-d.

[0065] The fluid streaming through the pipe 15 passes a first tubular separator 11a wherein the gas is separated from the fluid because the density of the gas is lower than other fluid phases present in the incoming fluid. The gas phase is transported out through the outlet 14a in the upper section of the inclined tubular separator 14 to the outlet pipe 21.

[0066] The outlet 13a of the first inclined tubular separator 14a is connected in parallel to inlets 12b-d of the respective inclined tubular separators 11b-d thereby providing a sufficient separator capacity for separating oil from water and sand, for example. The oil phase is transported out of the separator system via the respective outlets 14b-d of the respective inclined separators 11b-d, and in the output manifold section 19 these outlets are connected together and are connected to the outlet pipe 20 of the separator system. The water and sand phase is transported out of each respective inclined tubular separators 14b-d being configured to separate oil from water and sand via the outlets 13b-d being located in the bottom section of the inclined separator system first outlet manifold 17 an to the outlet pipe 18.

[0067] The interconnection pattern provided for with pipe connections in the input manifold section 17, is reflected in the output manifold section 19. The pattern of interconnecting pipes reflects the properties of the incoming fluids from an oil well, while the interconnection pattern in the output manifold section 19 reflects how many fluid phases that are to be separated and how different fluid phases will still be combined. Therefore, there is a functional relationship between the interconnecting pattern of pipes in the input manifold section 17 and the output manifold section 19, but not necessary as a one to one mapping of the configuration of the respective pipes in each respective manifold section.

[0068] Reference is now made to FIG. 2, showing details of the interior of the inclined tubular separators 11a-d. The inclined tubular separators 11a-d have an inner elongated tube 40 located centred inside an outer elongated tube 50, wherein the inner tube 40 is in fluid communication with the input manifold 17 or pipe 15 via the respective inlets 12a-d and via a curved pipe 41 extending out of the outer tube 50 via an opening 42 in a side wall of the outer tube 50 at a lower section of the inclined tubular separator 11a-d. The inner tube 40 exhibits a conical shaped part 43 at the lower/inlet part thereof expanding in width from the curved pipe 41 to a final width of the inner tube 40. The walls of the inner tube 40 are further perforated with a plurality of holes or slots 44, and the inner tube 40 is terminated and closed at upper end thereof. The outer tube 50 has a first outlet opening 51 arranged at upper end thereof connected to the outlet 14a-d and a second outlet opening 52 at lower end thereof connected to the outlet 13a-d. The curved pipe 41 provides a small cyclone effect separating oil and water in two layers before the mixed fluid enters the conical shaped part 43. The conical shape will reduce the speed of the fluid before passing the inner tube holes or slots 44.

[0069] Reference is now made to FIG. 3 which is a principle drawing of a prior art system as disclosed in NO341580 B1, in the name of the applicant, the disclosure of this incorporated herein by reference, illustrating the principle of establishing and maintaining a water-wetted surface. The system establish and maintain a water-wetted inlet pipe surface in conjunction with a slug suppression and gas removal unit 100 (SSGR), horizontal large diameter pipeline 300 and multiple inclined tubular oil and water separators 11a-d, based on the principles described above. E.g. the horizontal large diameter pipeline 300 can have a diameter between 10″ and 20″.

[0070] In an inclined oil and water separator system 10 like this, a unit 100 designed to suppress slug flow and remove free gas (SSGR unit), also known as gas harp, will be arranged between a well and the inclined oil and water separator system 10. The inclined oil and water separator system 10 will further be connected to the SSGR unit 100 via a large diameter pipeline 300 extending mainly horizontally from the SSGR unit 100 to the inclined oil and water separator system 10.

[0071] Oil and water outlet 110 of the production SSGR 100 is connected to the inclined tubular separator system 10, via the input manifold section 16, by the horizontal large diameter pipeline 300. The production SSGR 100 will further provide a gas output 120 for gas export via a gas outlet pipeline 130. The gas outlet pipeline 130 may also be connected to an oil and gas output of the inclined separator system 10, which is well known for a skilled person and requires no further description herein.

[0072] Reference is now made to FIGS. 4-5 which are a principle drawing of an embodiment of a system for separating oil well substances. The system further comprises an apparatus 500 for capturing liquid arranged interior in the gas outlet pipeline 130 from the slug and gas removal unit 100 capturing liquid in the gas outlet pipeline 130, and thus liquid in the separated gas from the slug suppression and gas removal unit 100.

[0073] According to one embodiment the apparatus 500 is formed by a helical liquid collector adapted for capturing creeping liquid film in the gas outlet pipeline 130.

[0074] The system further comprises a vertically extending drainpipe 510 extending between the gas outlet pipeline 130 and the horizontal large diameter pipeline 300, which vertically extending drainpipe 510 is aligned with corresponding openings 121, 301 in lower part of the gas outlet pipeline 130 and upper part of the horizontal large diameter pipeline 300, respectively.

[0075] The helical liquid collector 500 extends in longitudinal direction of the gas outlet pipeline 130 and ends in the opening 121 of the lower part of the gas outlet pipeline 130, as shown in FIG. 5.

[0076] The helical liquid collector 500 is fixed, e.g. by welding, to interior surface of the gas outlet pipeline 130, and extends a distance D in longitudinal direction of the gas outlet pipeline 130. The distance D will typically be minimum 1.5× pipeline diameter and maximum 3× pipeline diameter. There will preferably be a distance Di in the range 1-3× pipeline diameter, more preferably approximately 1.5× pipeline diameter, between each turn of the helical liquid collector 500. Pipeline diameter referred to above is the diameter of the gas outlet pipeline 130.

[0077] The helical liquid collector 500 is protruding interior in the gas outlet pipeline 130 with a height H from the interior surface of the gas outlet pipeline 130. The height H will e.g. be at least 1 cm, but not higher than 2 cm, such that it will not restrict the flow of gas in the gas outlet pipeline 130.

[0078] According to an embodiment the helical liquid collector 500 extends at least 360 degrees, more preferably in the range 500-600 degrees, in circumferential direction of the gas outlet pipeline 130 over the distance D.

[0079] An important parameter when combined with an inclined oil and water separator system 10 is the liquid level 400 interaction between the SSGR unit 100 and the inclined tubular oil and water separators 11a-d of the inclined oil and water separator system 10, as well as the drainpipe 510. This liquid level 400 shall be close to equal height providing a liquid lock avoiding free gas carry under between the units. Associated gas (dispersed in the liquids) will be transported in the large diameter pipeline 300, but further gas release will be minimal and not interfere with the operation or function of the inclined oil and water separator system 10.

[0080] This liquid lock can also be arranged in other ways, such as e.g. by using a gas harp, as well known in prior art, e.g. WO 2006/098637, upstream the inclined oil and water separators 11a-d, where the gas harp will function as a Slug Suppressor Gas Removal (SSGR) unit 100.

[0081] Downstream the SSGR unit 100 the fluids will be transported in the large diameter pipeline 300 entering the inclined oil and water separators 11a-d of the inclined oil and water separator system 10. The liquid level (elevation) 400 of the SSGR unit 100 located at a slope part of the gas Harp/SSGR unit 100, at the top of inclined oil and water separators 11a-d and in lower part of the drainpipe 510 will provide and maintain the liquid lock upstream the inclined tubular oil and water separators 11a-d preventing gas carry under.

[0082] Accordingly, the liquid level 400 in the drainpipe 510 will function as a gas lock avoiding gas carry under into the large diameter pipeline 300.

[0083] As mentioned, the inclined oil and water separator system 10 will preferably consist of multiple inclined tubular oil and water separators 11a-d, as described above, the number of inclined tubular oil and water separators 11a-d will depend on the flow rate and separability of oil/water.

[0084] In FIG. 6 is schematically the principle of promoting separation of oil and water prior to entering the inclined oil and water separator system 10 by a longitudinal cross-sectional view of the large diameter pipeline 300, with exploded views showing details. Along the extension of the large diameter pipeline 300 separation between water and oil occurs due to gravity forces. Along the extension of the large diameter pipe 300 this will result in increased oil velocity and dispersion band 700 which make the sedimentation distance for water droplets in oil to move towards the interface between oil and water shorter. This increase of velocity difference between oil and water will enhance separation by breaking the dispersion band 700.

[0085] Further, the embodiments use the liquid velocity in the large diameter pipeline 300 as an ejector for captured liquid and maintaining the liquid level in the vertically extending drainpipe 510.

[0086] The inner tube 40 further also includes perforations in the form of holes or slots 44. The location of the holes or slots 44 and the interface 600 between oil and water in the inclined tubular separator 11a-d, provide an oil and water separator system that establish and maintain a lower part that is always water-wetted, as shown in FIG. 7.

[0087] Further, the location of the first hole or slot 44, referred to inlet end of the inclined tubular oil and water separator 11a-d, at least at the waterside, start approx. ⅓ of the overall length L of the inclined tubular oil and water separator 11a-d, i.e. after the conical part 43.

[0088] It should be mentioned that the number and size of holes or slots 44 at the oil and water side, respectively, can be different. Also the location of the first hole or slot 44 on the oil side (upper side) can be further from the inlet end of the inclined tubular oil and water separator 11a-d than the first hole or slot 11a-d at the water side (the lower side).

[0089] The interface 600 between oil and water is located at approx. 50-70% of the overall length L of the inclined tubular oil and water separator 11a-d, referred to inlet end of the inclined tubular oil and water separator 11a-d. This combination, location of holes or slots 44, and oil/water interface 600, secures a constant presence of water in the lower part of the inclined tubular oil and water separator 11a-d. Achieved by this is improved coalescence, hence better separation of oil and water.

[0090] In the disclosed embodiments, where the inner tube 40 has a slot or hole 44 located at a position ⅓ L, at least at the water side, from inlet of the inclined tubular oil and water separator 11a-d, and an interphase between oil and water at 50-70% of the overall length L from inlet of the inclined tubular oil and water separator 11a-d, ensures that the inlet of the inclined tubular oil and water separators 11a-d will be water-wetted even in the cases where pure oil with little dispersed water enters the separator system. This water lock function will always create the velocity difference between the phases (oil and water); hence promote separation by reducing the dispersion band 700 normally present between oil and water.

[0091] Accordingly, the inventive embodiments provide an inlet arrangement for an oil and water separator system designed to prevent liquid carry over in separated gas by capturing and removing liquid from separated gas, as well as establishing and maintaining a water lock preventing gas carry under between the slug suppression and gas removal unit (SSGR) and the inclined oil and water separator system, as well as drainpipe.