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WO2003031865A1 - Installation de pipelines sous-marins - Google Patents

Installation de pipelines sous-marins Download PDF

Info

Publication number
WO2003031865A1
WO2003031865A1 PCT/EP2002/010585 EP0210585W WO03031865A1 WO 2003031865 A1 WO2003031865 A1 WO 2003031865A1 EP 0210585 W EP0210585 W EP 0210585W WO 03031865 A1 WO03031865 A1 WO 03031865A1
Authority
WO
WIPO (PCT)
Prior art keywords
pipeline
gas
pig
pressure
flooding
Prior art date
Application number
PCT/EP2002/010585
Other languages
English (en)
Inventor
Dominique Perinet Marquet
Michel Liogier
Original Assignee
Stolt Offshore Sa
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Stolt Offshore Sa filed Critical Stolt Offshore Sa
Publication of WO2003031865A1 publication Critical patent/WO2003031865A1/fr

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16L—PIPES; JOINTS OR FITTINGS FOR PIPES; SUPPORTS FOR PIPES, CABLES OR PROTECTIVE TUBING; MEANS FOR THERMAL INSULATION IN GENERAL
    • F16L55/00—Devices or appurtenances for use in, or in connection with, pipes or pipe systems
    • F16L55/26—Pigs or moles, i.e. devices movable in a pipe or conduit with or without self-contained propulsion means
    • F16L55/28—Constructional aspects
    • F16L55/30—Constructional aspects of the propulsion means, e.g. towed by cables
    • F16L55/38—Constructional aspects of the propulsion means, e.g. towed by cables driven by fluid pressure

Definitions

  • This invention relates to methods and apparatus for installation of deep water pipelines, wherein a pipeline is flooded to drive a "pig" along the pipeline by the action of hydrostatic pressure acting upon it.
  • Pipelines are generally fabricated and laid on the sea bed containing air or other gas at atmospheric pressure. Before connection to other parts of the subsea installation, these pipes are flooded. A "pig" may be driven along the pipeline to expel the air in an orderly fashion. The pig may also carry a gauge plate or other devices to detect anomalies in the bore of the pipe. Pipeline pigging is conventionally achieved by pumping. Extensive on-site equipment is required to support the use of pumps, including hydraulic, power and maintenance systems; all of which are costly and inconvenient to use.
  • UK patent GB 2303895 B proposes controlled flooding with seawater using the ambient hydrostatic pressure to transport the pig unit along the pipeline. Although this reduces the equipment and expense required, the air within the pipe can only be compressed to a finite volume, at which the pressure difference between water and air will be too close to zero to overcome the substantial friction between pig and pipe. Accordingly, a boost pump is still required in the system of GB 2303895 to drive the pig unit the last part of the way, and to expel the last of the air through a small vent outlet.
  • the invention aims to provide improved methods and apparatuses for implementing flooding and pigging of subsea installations, particularly to reduce even further the cost and complexity of the equipment required.
  • the invention provides a method of flooding a length of subsea pipeline between first and second ends, wherein the pipeline in an initial state contains a gas at a pressure below the ambient hydrostatic pressure and a pig unit at the first end, wherein fluid is admitted progressively into the first end of the pipeline to drive the pig unit under the influence of said ambient pressure toward the second end, compressing said gas, and wherein an auxiliary chamber is connected to the second end of the pipeline so as to accommodate the gas in its compressed form substantially outside the pipeline itself.
  • auxiliary chamber for example a simple tank, allows the pig to travel further than in the prior art, where the pressure of the compressed gas eventually stops the pig well short of the second end.
  • the volume of the auxiliary chamber may equal or exceed the volume of the contained gas when compressed, thereby permitting the pig to travel completely to the second end of the pipeline.
  • the auxiliary chamber may be in communication with the pipeline already before flooding commences. It may be coupled to the pipeline before or after laying on the seabed.
  • the contained gas in pipeline and chamber will generally be air at atmospheric pressure, with or without protective additives.
  • auxiliary chambers there may be provided plural auxiliary chambers, all comiected at the second end or individually connected at intermediate points on the pipeline.
  • the method may further comprise recovering the pig.
  • the pig may carry instrumentation for measurement of the pipe between the first and second ends.
  • the invention further provides an apparatus for use in a method as set forth above, the apparatus comprising a pipeline having first and second ends and containing a gas at a pressure substantially below an ambient hydrostatic pressure at which the pipeline is to be installed, inlet means for causing controlled flooding of the pipeline at the first end under said ambient hydrostatic pressure, and an auxiliary chamber connectable to the second end of the pipeline to receive and hold said gas outside the pipeline when flooded under the influence of said flooding hydrostatic pressure.
  • the apparatus may further comprised a pig unit adapted to be drive from said first end to said second end within the pipeline by said flooding.
  • Figure 1 is a diagrammatic representation of a known apparatus for controlled flooding of a gas-filled underwater pipeline to enable a pig to be transported along the pipeline.
  • the apparatus is shown in an initial state, prior to flooding;
  • Figure 2 shows the apparatus of Figure 1 at the end of a free-flooding stage of operation
  • Figure 3 shows the apparatus of Figures 1 and 2 at the end of a boost pumping stage of operation
  • Figure 4 is a diagrammatic representation of an apparatus for controlled flooding of a gas-filled underwater pipeline in accordance with an embodiment of the present invention.
  • the apparatus is shown in an initial state, prior to flooding;
  • Figure 5 shows the apparatus of Figure 4 at the end of a free-flooding stage of operation, showing all gas within the pipeline effectively expelled from the pipeline into an auxiliary tank.
  • FIG. 1 is a diagrammatic representation of the apparatus known from GB 2303895.
  • a deep water pipeline 100 filled with gas 102, such as air, containing at its inlet end a pig unit 104, has connected to its inlet a means for flooding 106 the pipeline and a means for pumping liquid 108 into the pipeline.
  • Flood and Pump Valves 110, 112 are applied to each means 106, 108 so that when one is in use the other is disabled. With both valves closed there is no hydrostatic pressure acting upon the rear of the pig unit 104, so it remains motionless at the start of the pipeline.
  • FIG 2 shows the known apparatus of Figure 1, but after the Flood Valve 110 has been opened and the pipeline 100 has filled with liquid by controlled free-flooding.
  • the flow of liquid into the pipeline has been used to propel the pig unit 104 along the pipeline almost to the far (right hand) end.
  • the driving force that propels the pig unit along the pipeline is the hydrostatic pressure difference between the liquid behind the pig unit and the gas in front of it.
  • Various means are used to control the rate at which the pig unit travels along the pipeline, such as controlling the flow rate of liquid entering the pipeline.
  • the hydrostatic pressure difference reduces to a point where there is insufficient pressure to propel the pig unit when the pressure of the liquid behind the pig largely matches the pressure of the gas that has been compressed on the other side.
  • the volumetric ratio of liquid to gas in the pipeline is approximately 100:1. Therefore, as a portion of the pipeline remains filled with gas the pig unit cannot be propelled along the remaining 1% of pipeline.
  • pumping is employed to increase the hydrostatic pressure behind the pig unit and venting, such as a check valve, is incorporated to release the gas in front of the pig unit, the subsequent pressure differential propelling the pig unit further along the pipeline.
  • FIG. 3 shows the same known apparatus, but after the pig unit 104 has been propelled further along the pipeline by the use of a boost pump 108 and check valve 114.
  • the boost pump increases the pressure in the pipeline to reinstate a pressure difference between the rear and the front of the pig unit, and thus propelling the pig unit further along the pipeline.
  • the pressure in front of the pig unit is substantially maintained at deep-water pressure by check valve 114, which releases the gas from the pipeline when the pressure of the gas within the pipeline exceeds the pressure of the surrounding deep-water into which the gas is expelled.
  • the need for boost pump 108 adds substantial complexity to the apparatus, requiring complex support systems such as hydraulic, electrical and maintenance systems. In addition, the chances of failure exist, so that a parallel redundant system may also be required. Alternatively, a vessel-based pump must be brought and connected to complete the operation.
  • Figure 4 shows a novel apparatus for controlled flooding of a gas-filled underwater pipeline to transport a pig unit fully along the pipeline, but without the need for pumping. Shown in its initial state, the apparatus contains the same elements 100 to 110 as the known apparatus described earlier with reference to Figure 1, except for the boost pump 108 and associated valve 112. Connected to the far end of the pipeline, however, is an auxiliary tank 400, also containing gas at atmospheric pressure, or at least a pressure substantially less than that of the surrounding seawater.
  • FIG. 5 shows the novel apparatus after Flood Valve 110 has been opened and pipeline 100 and optionally a portion of auxiliary tank 400 have filled with liquid.
  • the pig and liquid can now be propelled to be stopped only by the end of the pipeline, before reaching any the point where the pressure difference between liquid and compressed gas within the pipeline and auxiliary tank becomes too small.
  • the flow of liquid may optionally be permitted at this point to bypass the pig beyond the end of the pipeline, to complete the flooding and to partially flood the tank 400.
  • complete flooding of the pipeline has been achieved to propel the pig unit 104 to the end of the pipeline, using only the hydrostatic pressure of the seawater and passive equipment.
  • the improved apparatus and method for flooding and pigging deep water pipelines is more reliable, more cost effective and simpler to support in service.
  • the tanks volume necessary is simply that sufficient to hold the original volume of gas, when compressed to the pressure of the water at the installation depth. With the example of 1000m depth provided earlier, this would amount to approximately 1% of the total volume of the pipeline 100 plus tank 400.
  • the skilled person will readily be able to calculate the percentage volume, and hence the volume of the auxiliary tank, for different situations, by known properties of the gas and seawater, the hydrostatic pressure at the installation depth and so forth.

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • Mechanical Engineering (AREA)
  • Pipeline Systems (AREA)

Abstract

L'invention concerne un procédé et un appareil améliorés qui permettent d'installer de pipelines sous-marins pour eaux profondes. Un pipeline (100) est alimenté par une extrémité afin d'entraîner un racleur (104) à l'intérieur dudit pipeline, sur toute la longueur de ce dernier, sous l'effet d'une pression hydrostatique agissant sur le racleur, tout en faisant l'économie de matériel supplémentaire. A un état initial, une longueur du pipeline contient un gaz (102) à une pression inférieure à la pression hydrostatique ambiante et un racleur logé à une extrémité pourvue d'un point d'entrée (106) pour l'eau d'alimentation. Le pipeline est alimenté entre ses deux extrémités, ce qui permet d'admettre progressivement le fluide dans le pipeline au moyen d'une soupape d'alimentation (110) afin d'entraîner le racleur, sous l'effet de la pression ambiante, vers l'extrémité distante, en comprimant le gaz dans le pipeline. Une chambre auxiliaire (400) est reliée à l'extrémité distante du pipeline de façon qu'elle reçoive le gaz (102) sous forme comprimée sensiblement à l'extérieur du pipeline.
PCT/EP2002/010585 2001-10-02 2002-09-26 Installation de pipelines sous-marins WO2003031865A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GBGB0123627.2A GB0123627D0 (en) 2001-10-02 2001-10-02 Installation of subsea pipelines
GB0123627.2 2001-10-02

Publications (1)

Publication Number Publication Date
WO2003031865A1 true WO2003031865A1 (fr) 2003-04-17

Family

ID=9923089

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/EP2002/010585 WO2003031865A1 (fr) 2001-10-02 2002-09-26 Installation de pipelines sous-marins

Country Status (2)

Country Link
GB (1) GB0123627D0 (fr)
WO (1) WO2003031865A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2875889A1 (fr) * 2004-09-30 2006-03-31 Technip France Sa Installation et methode d'entrainement d'un racleur de conduite sous-marine

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2303895B (en) 1995-07-28 1998-11-04 Copipe Systems Ltd Improvements in or relating to underwater pipeline apparatus for delivering a pig unit through a sea-bed pipeline
GB2325293A (en) * 1997-05-15 1998-11-18 George Charles Bruce Method for propelling a pig along a pipeline

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2303895B (en) 1995-07-28 1998-11-04 Copipe Systems Ltd Improvements in or relating to underwater pipeline apparatus for delivering a pig unit through a sea-bed pipeline
GB2325293A (en) * 1997-05-15 1998-11-18 George Charles Bruce Method for propelling a pig along a pipeline

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2875889A1 (fr) * 2004-09-30 2006-03-31 Technip France Sa Installation et methode d'entrainement d'un racleur de conduite sous-marine
WO2006035158A1 (fr) * 2004-09-30 2006-04-06 Technip France Installation et methode d'entrainement d'un racleur de conduite sous-marine
US7964041B2 (en) 2004-09-30 2011-06-21 Technip France Installation and method for driving a submarine pipeline scraper

Also Published As

Publication number Publication date
GB0123627D0 (en) 2001-11-21

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