EP0238535B1 - Slug-catcher that can be pigged - Google Patents
Slug-catcher that can be pigged Download PDFInfo
- Publication number
- EP0238535B1 EP0238535B1 EP86905447A EP86905447A EP0238535B1 EP 0238535 B1 EP0238535 B1 EP 0238535B1 EP 86905447 A EP86905447 A EP 86905447A EP 86905447 A EP86905447 A EP 86905447A EP 0238535 B1 EP0238535 B1 EP 0238535B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- slug
- catcher
- riser
- pipeline
- liquid
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000007788 liquid Substances 0.000 claims abstract description 27
- 241000237858 Gastropoda Species 0.000 claims abstract description 11
- 230000001105 regulatory effect Effects 0.000 claims abstract description 6
- 238000011084 recovery Methods 0.000 claims abstract 2
- 238000000926 separation method Methods 0.000 claims description 12
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 abstract description 6
- 241000282887 Suidae Species 0.000 description 2
- 238000009825 accumulation Methods 0.000 description 2
- 230000035508 accumulation Effects 0.000 description 2
- 238000012423 maintenance Methods 0.000 description 2
- 238000000034 method Methods 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
Images
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F17—STORING OR DISTRIBUTING GASES OR LIQUIDS
- F17D—PIPE-LINE SYSTEMS; PIPE-LINES
- F17D3/00—Arrangements for supervising or controlling working operations
- F17D3/14—Arrangements for supervising or controlling working operations for eliminating water
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B43/00—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells
- E21B43/34—Arrangements for separating materials produced by the well
Definitions
- the invention concerns a slug-catcher of the type described in the introduction to patent claim 1.
- a slug is an accumulation of liquid which blocks the cross-section of a pipeline that is mainly filled with gas. Slugs are propelled by the difference in gas pressure at the two edges. Given specific conditions, slugs can contain a large amount of liquid and/or reach high velocities.
- Slug-catchers have been developed to prevent slugs entering intake units such as processing plants. These devices are designed to divide the liquid and the gas so that only the gas is permitted to enter the intake unit directly. In addition, the slug has to be retarded to prevent a liquid impact which can cause mechanical stress. A further consideration is that it is desirable to maintain a constant flow of gas into the intake unit.
- Slug-catchers are known which are based on the so-called « finger principle (e. g. US-A-4 519 815) where gas and liquid are divided by directing them into a number of parallel branch pipes.
- « finger principle e. g. US-A-4 519 815
- This type of device requires a great deal of space and is unsatisfactory for subsea operations.
- Another difficulty is that it is impossible to clean the unit using pigs, i. e. bodies which are led along a pipe.
- a second type of slug-catcher exists, this is based on separation in a tank (e. g. US-A-4 160 652) where the capacity of the tank is dimensioned so as to accomodate the largest slug volume that can be expected.
- slug-catchers takes the form of relief piping, i.e. an extra loop of pipe. These are frequently used with pigs and assume that incoming slugs are led into the relief pipe by means of a valve.
- the main object of the invention is to provide a slug-catcher that functions satisfactorily under water, too and that can be installed under water using normal pipe-laying techniques.
- a specific object is providing a slug-catcher which can be mounted on the seabed in connection with an intake unit placed above the water, such as on a platform. Such a slug-catcher should have no moveable parts under water, as well as being reliable and easy to maintain.
- the invention can be realized by designing the slug-catcher in accordance with the characterizing part of patent claim 1.
- a slug-catcher is constructed in a straight forward manner and can be situated on the seabed and connected to a pipeline from the platform or well. Increasing the size to accomodate large slugs is not problematic and maintenance can be done easily.
- the slug-catcher according to this invention can be pigged, i. e. cleaned by a pig.
- the slug-catcher according to the invention operates as follows :
- a platform 11 is located in an offshore area with a foundation on the seabed.
- the main pipeline 12 from a remote platform or wellhead (not illustrated) is designed to carry gas to an intake unit on the platform.
- the riser 14, which will be called the secondary riser, could for instance have a cross-section which is only 1/4 of that of the main pipeline.
- the main pipeline 12 continues from the junction 13 to a pipe loop 15 on the seabed.
- the pipe loop 15 ensures that there is enough volume to gather liquid from a slug.
- This loop 15 continues into a riser 16 at the foundations of the platform.
- This riser 16 which henceforth is referred to as the main riser is led up to the intake unit on the platform.
- Fig. 2 is a schematic presentation of the design of the intake unit on the platform 11.
- the two risers, 14 and 16, are led into a separation tank 17.
- the separation tank has a liquid drainage tube 18, the drainage being controlled by a valve 19.
- At the top edge of the separation tank 17 there is an outlet pipe 20 for gas.
- the pressure in the separation tank 17 is maintained by a valve 21 to regulate pressure in the outlet pipe 20.
- the main pipe loop 15 can be emptied of any liquid accumulations by regulating the throttle valve 22 so that there will be enough pressure to drive the liquid up along the main riser 16 into the separation tank 17.
- the throttle valve 22 can be regulated so that the pressure it creates compensates for the loss of pressure due to friction in the pipe loop 15 and the main riser 16. This means that the loop 15 will be self- emptying.
- a float in the separation tank 17 controls the opening of the valve 19 so that a reasonably constant liquid level is retained in the tank 17.
- the length of the pipe loop 15 is selected so that apart from accomodating the dimensions of the slugs, sufficient retardation of the said slug is achieved when pressure is equalized.
- the height of the risers 14, 16 is determined by the height of the platform above the seabed. A height of 150 m will be adequate with almost all conceivable slug sizes. Should this height not be enough, the counter-pressure to limit the entry of liquid in the secondary riser 14 can be increased by adjusting the throttle valve 22.
Landscapes
- Engineering & Computer Science (AREA)
- Geology (AREA)
- Life Sciences & Earth Sciences (AREA)
- Mining & Mineral Resources (AREA)
- Environmental & Geological Engineering (AREA)
- Fluid Mechanics (AREA)
- Physics & Mathematics (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Pipeline Systems (AREA)
- Earth Drilling (AREA)
- Sampling And Sample Adjustment (AREA)
Abstract
Description
- The invention concerns a slug-catcher of the type described in the introduction to patent claim 1.
- A slug is an accumulation of liquid which blocks the cross-section of a pipeline that is mainly filled with gas. Slugs are propelled by the difference in gas pressure at the two edges. Given specific conditions, slugs can contain a large amount of liquid and/or reach high velocities.
- Slug-catchers have been developed to prevent slugs entering intake units such as processing plants. These devices are designed to divide the liquid and the gas so that only the gas is permitted to enter the intake unit directly. In addition, the slug has to be retarded to prevent a liquid impact which can cause mechanical stress. A further consideration is that it is desirable to maintain a constant flow of gas into the intake unit.
- Slug-catchers are known which are based on the so-called « finger principle (e. g. US-A-4 519 815) where gas and liquid are divided by directing them into a number of parallel branch pipes. This type of device requires a great deal of space and is unsatisfactory for subsea operations. Another difficulty is that it is impossible to clean the unit using pigs, i. e. bodies which are led along a pipe. A second type of slug-catcher exists, this is based on separation in a tank (e. g. US-A-4 160 652) where the capacity of the tank is dimensioned so as to accomodate the largest slug volume that can be expected.
- Though this type of slug-catcher requires less space than the first type, regulating the liquid level is an extremely demanding task.
- Yet another design for slug-catchers takes the form of relief piping, i.e. an extra loop of pipe. These are frequently used with pigs and assume that incoming slugs are led into the relief pipe by means of a valve.
- All existing slug-catchers have one thing in common, the volume must be larger than the slug volume which is the basis for the dimensions. If larger slugs are expected, the slug-catchers must be commensurately larger. This can represent a problem on platforms with limitations upon weight and size. It is therefore desirable to be able to place slug-catchers on the seabed. However, problems with installing the equipment and servicing the valves and regulatory units underwater make this difficult. Internal maintenance work such as the removal of solids also becomes difficult when the equipment is located in deep water.
- The main object of the invention is to provide a slug-catcher that functions satisfactorily under water, too and that can be installed under water using normal pipe-laying techniques. A specific object is providing a slug-catcher which can be mounted on the seabed in connection with an intake unit placed above the water, such as on a platform. Such a slug-catcher should have no moveable parts under water, as well as being reliable and easy to maintain.
- The invention can be realized by designing the slug-catcher in accordance with the characterizing part of patent claim 1. Such a slug-catcher is constructed in a straight forward manner and can be situated on the seabed and connected to a pipeline from the platform or well. Increasing the size to accomodate large slugs is not problematic and maintenance can be done easily. The slug-catcher according to this invention can be pigged, i. e. cleaned by a pig.
- The slug-catcher according to the invention operates as follows :
- When a slug passes the secondary riser, a small amount of the liquid will be pressed upwards whilst most will continue along the main loop. After the slug has passed this branching point or junction, the secondary riser will be emptied in that some of the liquid will fall back into the main pipeline and the rest will be forced up into the tank. When there is an open secondary riser, the gas pressure behind the slug is released, this will lead to the slug being retarded by the flow friction in the main loop.
- Other advantageous features in the invention are stated in the subclaims.
- The invention will now be described more closely by reference to the drawings, where :
- Fig. 1 shows a schematic perspective view of an offshore platform which is linked to a slug-catcher designed in accordance with the invention whilst
- Fig. 2 is a side view showing the principle of the slug-catcher designed in accordance with the invention.
- In fig. 1 a
platform 11 is located in an offshore area with a foundation on the seabed. Themain pipeline 12 from a remote platform or wellhead (not illustrated) is designed to carry gas to an intake unit on the platform. There is ajunction 13 on the main pipe with the outlet of ariser 14 which can have a considerably smaller diameter than the main pipe. Theriser 14, which will be called the secondary riser, could for instance have a cross-section which is only 1/4 of that of the main pipeline. - The
main pipeline 12 continues from thejunction 13 to apipe loop 15 on the seabed. Thepipe loop 15 ensures that there is enough volume to gather liquid from a slug. Thisloop 15 continues into ariser 16 at the foundations of the platform. Thisriser 16 which henceforth is referred to as the main riser is led up to the intake unit on the platform. - Fig. 2 is a schematic presentation of the design of the intake unit on the
platform 11. The two risers, 14 and 16, are led into aseparation tank 17. The separation tank has aliquid drainage tube 18, the drainage being controlled by avalve 19. At the top edge of theseparation tank 17 there is anoutlet pipe 20 for gas. The pressure in theseparation tank 17 is maintained by avalve 21 to regulate pressure in theoutlet pipe 20. - When a slug goes past the
junction 13, the liquid from the slug will rise up thesecondary riser 14. This creates a height potential that prevents anymore liquid entering the secondary riser. The height in the riser will depend on the pressure conditions, the size of the slug and the flow velocity of the slug. The height of slow slugs (3m/s) will be insignificant. Rapid slugs (10 m/s or faster) can produce heights which are 20-30 % of the length of the slug. The amount of liquid which is drawn off equals the product of the height risen and the cross-sectional area of the secondary riser. This can be reduced by reducing the diameter of the latter. - Once the slug has passed the
junction 13 the liquid volume which has entered thesecondary riser 14 will be emptied, partly by its running back into the main pipeline and also by being pressed through athrottle valve 22 which links thesecondary riser 14 to theseparation tank 17. - When the
secondary riser 14 is emptied of liquids, the difference between the pressure at the front and back of the slug will be evened out by means of theseparation tank 17. The kinetic energy of the slug will be reduced by the flow friction until the slug is halted. Themain pipe loop 15 can be emptied of any liquid accumulations by regulating thethrottle valve 22 so that there will be enough pressure to drive the liquid up along themain riser 16 into theseparation tank 17. Under normal conditions, thethrottle valve 22 can be regulated so that the pressure it creates compensates for the loss of pressure due to friction in thepipe loop 15 and themain riser 16. This means that theloop 15 will be self- emptying. - A float in the
separation tank 17 controls the opening of thevalve 19 so that a reasonably constant liquid level is retained in thetank 17. The length of thepipe loop 15 is selected so that apart from accomodating the dimensions of the slugs, sufficient retardation of the said slug is achieved when pressure is equalized. The height of therisers secondary riser 14 can be increased by adjusting thethrottle valve 22.
Claims (8)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AT86905447T ATE42602T1 (en) | 1985-09-18 | 1986-09-17 | PIG CLEANABLE COLLECTOR FOR LIQUID PLUG. |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
NO853656A NO157467C (en) | 1985-09-18 | 1985-09-18 | DEVICE FOR COLLECTION OF LIQUID CONNECTORS IN A GAS-LEADING PIPELINE. |
NO853656 | 1985-09-18 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0238535A1 EP0238535A1 (en) | 1987-09-30 |
EP0238535B1 true EP0238535B1 (en) | 1989-04-26 |
Family
ID=19888485
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP86905447A Expired EP0238535B1 (en) | 1985-09-18 | 1986-09-17 | Slug-catcher that can be pigged |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP0238535B1 (en) |
DE (1) | DE3663054D1 (en) |
NO (1) | NO157467C (en) |
WO (1) | WO1987001759A1 (en) |
Families Citing this family (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
NO870910L (en) * | 1987-03-05 | 1988-09-06 | Norske Stats Oljeselskap | DEVICE FOR PROCESS EQUIPMENT SYSTEM FOR PROCESSING EQUIPMENT FOR SEA. |
NO163424C (en) * | 1988-02-03 | 1991-11-28 | Norsk Hydro As | INTEGRATED FLOW TRANSMISSION TRANSMISSION SYSTEM. |
US5232475A (en) * | 1992-08-24 | 1993-08-03 | Ohio University | Slug flow eliminator and separator |
US5507858A (en) * | 1994-09-26 | 1996-04-16 | Ohio University | Liquid/gas separator and slug flow eliminator and process for use |
EP1409834A2 (en) * | 2000-01-17 | 2004-04-21 | Lattice Intellectual Property Limited | Slugging control |
GB0000945D0 (en) * | 2000-01-17 | 2000-03-08 | Bg Intellectual Pty Ltd | Control of slugging in a riser |
NO320414B1 (en) * | 2002-02-04 | 2005-12-05 | Statoil Asa | Underwater multiphase conduction |
EA012384B1 (en) * | 2005-09-19 | 2009-10-30 | Бп Эксплорейшн Оперейтинг Компани Лимитед | Device for controlling slugging |
AU2008251130B2 (en) | 2007-05-16 | 2013-10-24 | Equinor Energy As | Method for liquid control in multiphase fluid pipelines |
Family Cites Families (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US3705626A (en) * | 1970-11-19 | 1972-12-12 | Mobil Oil Corp | Oil well flow control method |
BE790646A (en) * | 1971-10-29 | 1973-02-15 | Erap | PLANT FOR THE BOTTOM SEPARATION OF EFFLUENT FROM PRODUCT WELLS OF A MARINE OIL FIELD |
US4160652A (en) * | 1977-08-26 | 1979-07-10 | Texas Eastern Engineering, Ltd. | Method and apparatus for handling the fluids in a two-phase flow pipeline system |
US4519815A (en) * | 1983-12-15 | 1985-05-28 | Texas Eastern Engineering Ltd. | Slug-catching method and apparatus |
-
1985
- 1985-09-18 NO NO853656A patent/NO157467C/en unknown
-
1986
- 1986-09-17 EP EP86905447A patent/EP0238535B1/en not_active Expired
- 1986-09-17 WO PCT/NO1986/000065 patent/WO1987001759A1/en active IP Right Grant
- 1986-09-17 DE DE8686905447T patent/DE3663054D1/en not_active Expired
Also Published As
Publication number | Publication date |
---|---|
EP0238535A1 (en) | 1987-09-30 |
DE3663054D1 (en) | 1989-06-01 |
NO157467C (en) | 1988-03-23 |
NO157467B (en) | 1987-12-14 |
WO1987001759A1 (en) | 1987-03-26 |
NO853656L (en) | 1987-03-19 |
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