WO2016207359A2 - Système de stockage de meg, et procédé de déploiement et de fonctionnement de système de stockage de meg - Google Patents

Système de stockage de meg, et procédé de déploiement et de fonctionnement de système de stockage de meg Download PDF

Info

Publication number
WO2016207359A2
WO2016207359A2 PCT/EP2016/064683 EP2016064683W WO2016207359A2 WO 2016207359 A2 WO2016207359 A2 WO 2016207359A2 EP 2016064683 W EP2016064683 W EP 2016064683W WO 2016207359 A2 WO2016207359 A2 WO 2016207359A2
Authority
WO
WIPO (PCT)
Prior art keywords
meg
conduit
pressure
subsea
topside
Prior art date
Application number
PCT/EP2016/064683
Other languages
English (en)
Other versions
WO2016207359A3 (fr
Inventor
Jan-Otto REIMERS
Tom Grimseth
Gudmund Roger TOTLAND
Original Assignee
Kongsberg Oil & Gas Technologies As
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 Kongsberg Oil & Gas Technologies As filed Critical Kongsberg Oil & Gas Technologies As
Publication of WO2016207359A2 publication Critical patent/WO2016207359A2/fr
Publication of WO2016207359A3 publication Critical patent/WO2016207359A3/fr

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
    • B65D88/00—Large containers
    • B65D88/54—Large containers characterised by means facilitating filling or emptying
    • 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
    • E21B43/01—Methods or apparatus for obtaining oil, gas, water, soluble or meltable materials or a slurry of minerals from wells specially adapted for obtaining from underwater installations
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
    • B65D88/00—Large containers
    • B65D88/54—Large containers characterised by means facilitating filling or emptying
    • B65D88/58—Large containers characterised by means facilitating filling or emptying by displacement of walls
    • B65D88/60—Large containers characterised by means facilitating filling or emptying by displacement of walls of internal walls
    • B65D88/62—Large containers characterised by means facilitating filling or emptying by displacement of walls of internal walls the walls being deformable
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
    • B65D88/00—Large containers
    • B65D88/78—Large containers for use in or under water
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
    • B65D90/00—Component parts, details or accessories for large containers
    • B65D90/02—Wall construction
    • B65D90/04—Linings
    • B65D90/046—Flexible liners, e.g. loosely positioned in the container
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
    • B65D90/00—Component parts, details or accessories for large containers
    • B65D90/12—Supports
    • B65D90/20—Frames or nets, e.g. for flexible containers
    • B65D90/205—Frames or nets, e.g. for flexible containers for flexible containers, i.e. the flexible container being permanently connected to the frame
    • 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
    • E21B37/00—Methods or apparatus for cleaning boreholes or wells
    • E21B37/06—Methods or apparatus for cleaning boreholes or wells using chemical means for preventing or limiting, e.g. eliminating, the deposition of paraffins or like substances
    • 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
    • E21B41/00—Equipment or details not covered by groups E21B15/00 - E21B40/00
    • E21B41/0007—Equipment or details not covered by groups E21B15/00 - E21B40/00 for underwater installations
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
    • B65D2590/00—Component parts, details or accessories for large containers
    • B65D2590/02—Wall construction
    • B65D2590/04—Linings
    • B65D2590/043—Flexible liners
    • B65D2590/046—Bladders

Definitions

  • the present invention regards subsea storage of chemicals such as hydrate inhibitor Mono Ethylene Glycol (MEG).
  • MEG Mono Ethylene Glycol
  • the invention regards in particular a MEG storage system comprising a buffer bag or tank arranged at the seabed for storage of MEG and a plurality of conduits for providing the flow of MEG.
  • the invention also regards to a method for deployment and operation of the MEG storage system.
  • MEG mono ethylene glycol
  • DEG di-ethylene glycol
  • TEG tri-ethylene glycol
  • MEG mono ethylene glycol
  • Natural gas pipelines deep below sea level are subject to such conditions as low temperatures and high pressure, a combination prone to formation of hydrates.
  • a hydrate inhibitor such as MEG is, among other things, added to the well stream comprising natural gas.
  • MEG glycol based inhibitors and /or methanol are used for hydrate inhibition on cold start conditions, and also for depressurizing and pressure testing of safety barriers.
  • MEG used for hydrate inhibition of unprocessed gas in flow lines is often regenerated and reused. Some MEG will be lost in the process and has to be replaced. Thus, it is common to find on a production platform receiving
  • unprocessed oil and gas from subsea producers at least two MEG tanks, one lean MEG tank (unused MEG or regenerated MEG) and one rich MEG tank (MEG from the process due for entry into the regeneration plant).
  • Publication WO 02/42182 Al describes a method for separating two fluids in a storage tank.
  • the method concerns a method for separating two fluids in a tank by interposition of a psuedo membrane between the two fluids.
  • the method comprises the step of; making a stable emulsion from at least two immiscible liquids; placing said emulsion at the interface between the two fluids so as to constitute said membrane.
  • the invention also concerns a tank comprising a separating membrane.
  • the publication also describes, in an embodiment, the storage of water combined with a higher density fluid.
  • the water with lower density is arranged on top with a pseudo membrane between the water and the higher density fluid.
  • a filling line of the higher density fluid is located in the bottom of the tank, while a filling line of water is arranged on top of the tank.
  • Publication GB 1122975 B l describes a method and apparatus for the storage of petroleum under water, employing hydraulic displacement principles.
  • the hydraulic displacement storage apparatus contains varying quantities of petroleum and displacement water, separated by a membrane.
  • the displacement water is located at the bottom of the tank and has a filling line arranged at the same end.
  • a pump is arranged for filling of water and control the pressure inside the tank for discharging of petroleum.
  • the prior art publications do not disclose a system or method for subsea storage of hydrate inhibitor such as MEG. There exist several differences using the MEG as the stored fluid, compared to traditional storage of oil/petroleum in combination with seawater.
  • MEG has a typical density of 1113 kg/m at 20 degrees C and atmospheric conditions as compared to the specific gravity of seawater at typically 1025- 1030 kg/m depending on temperature and salinity. MEG has therefore a higher density than seawater, making the MEG to be positioned at the bottom section of a storage tank. This requires increased tank pressure in order to extract the MEG form the bottom of the tank.
  • prior art do not teach of a system that contains a buffer storage located subsea coordinating with a topside storage tank, and wherein the buffer storage is arranged to refill or extract the MEG volumes in the topside storage tank. Further, the prior art do not teach a MEG storage system that is easily deployable from a relatively small vessel and using standard deployment techniques and rigging.
  • the invention addresses a system organized to provide seabed based storage of MEG without compromising on availability and thus on production regularity, further the subsea storage system has the potential to increase the amount of available MEG and reduce risk for production stops due to lack of MEG.
  • One objective is to use only such components as already have been extensively employed in subsea production systems and are of proven reliability in operation. This approach alleviates the need for research and qualification programs with all their inherent potential costs and/or problems. Combined with good maintainability of key components and redundancy schemes the regularity will not be reduced. To the contrary it may even be improved by allowing more MEG available as a buffer.
  • An object of the invention is to provide seabed based storage of MEG without compromising on availability and thus on production regularity.
  • Another object of the invention is to free up space on the platform.
  • Another object of the invention is to increase the amount of available MEG and reduce risk for production stops due to lack of MEG.
  • Another object of the invention is to build a MEG storage system by using common components that have been extensively employed in subsea production systems and are of proven reliability in operation.
  • Yet another object of the invention is to have a compact riser solution and only require one or a few riser slots at the platform.
  • the intention according to the invention is also based on the economical aspect, by building a redundancy for the supply of MEG and avoiding the risk of production stops.
  • MEG mono ethylene glycol
  • DEG di- ethylene glycol
  • TEG tri-ethylene glycol
  • topside is in the following used for a structure or an apparatus or the part of a structure or an apparatus that is located above sea level or floating at sea level.
  • substrate is in the following referred to a structure or an apparatus being under water or below the sea level.
  • production site is in the following referred to subsea production facility of oil and gas.
  • the present invention relates to a MEG storage system for subsea storage of MEG in an immediate vicinity of a subsea production site.
  • the system comprising a collapsible flexible bag and;
  • At least one charge conduit providing a MEG conduit path between a topside position and the collapsible flexible bag
  • At least one discharge conduit providing a MEG conduit path between the collapsible flexible bag and the subsea production site.
  • the collapsible flexible bag is arranged within an open mechanical structure, wherein the flexible bag when in use is forming a single barrier between MEG and ambient water.
  • At least one booster pump is arranged on the discharge conduit for raising the MEG pressure to a level permitting injection of MEG into the production site and, wherein the at least one charge conduit has a conduit diameter of at least 50% smaller than the diameter of the at least one discharge conduit.
  • the level of MEG pressure is typically between 70 and 690 bar for permitting injection of the MEG into the production line.
  • sea water compensates for the drawn volume such as to maintain pressure balance at all times.
  • At least one discharge conduit is arranged between the MEG storage system and the production site, providing a MEG conduit path between the collapsible flexible bag and the subsea production site.
  • the dimension of the discharge conduit is bigger than the charge conduit allowing a greater amount of MEG to be injected into the production site at a certain time.
  • the smaller dimensions of the at least one charge conduit allows the collapsible flexible bag to be trickle charged, i.e. charged at a continuous low rate to keep the bag fully charged.
  • the at least one charge conduit has a conduit diameter of at least 60% smaller than the diameter of the at least one discharge conduit. Most preferably the at least one charge conduit diameter is 70% smaller than the diameter of the at least one discharge conduit.
  • This favorable embodiment allows the flexible bag to be charged by MEG continuously, i.e. trickle charge by a small line from the topside to the flexible bag for storage of MEG in the flexible bag.
  • the collapsible flexible bag is being used as storage bag and/or buffer bag. Due to the bigger diameter of the discharge conduit, the system allows a greater amount of MEG to be injected into the production site at a certain time. This is favorable during startup or shutdown of the production site, or other situations when greater amount of MEG is required.
  • the immediate vicinity of the collapsible flexible bag to the subsea production site has also a not negligible cost impact, by demanding less length of discharge conduit to be laid between the bag and the production site.
  • the charge conduit can be sized for average MEG consumption and not peak consumption thereby allowing a smaller diameter (less expensive) charge conduits to be arranged from the bag to the topside.
  • the diameter of the charge conduit is between 1 ⁇ 2 in to 1 in. and the diameter of the discharge conduit is 2 in.
  • other appropriate diameter size can also be used, according to local conditions and
  • the term "immediate vicinity” is a distance in the interval from 50-500 meters from the MEG storage system to the production site.
  • the collapsible flexible bag is made from rubber.
  • the bag can have different sizes according to the application, requirement, local conditions, operational needs, etc.
  • the bag comprises at least one charge conduit providing a MEG conduit path between a topside position and the collapsible flexible bag, but the bag can also be charged by retrieval of the entire MEG storage system and recharged on the deck of an Inspection Maintenance and Repair (IMR) vessel, or by means of a recharge hose deployed from an IMR vessel.
  • IMR Inspection Maintenance and Repair
  • the recharge of the MEG storage bag is conducted by a trickle line included in a control/power cable/umbilical.
  • the MEG storage bag may in a favorable embodiment be made up of a long and slender rubber bag, similar to shapes used for make shift storage of fuel. Such a tank shape will in its deflated form and supported by a well flooded structure, be easily installable by means of a standard installation crane, and typically over boarded over the side of an
  • the flexible bag is favorable arranged in an inclined position allowing MEG to be collected at one side, wherein said discharge conduit is connected to the flexible bag at said one side.
  • the size of the collapsible flexible bag is approx. 10-100 m .
  • the collapsible flexible bag is arranged within an open mechanical structure, wherein the flexible bag when in use is forming a single barrier between MEG and ambient water.
  • the open mechanical structure is made lightweight (for example, made of steel or GRP) and open to the surroundings, i.e. a well flooded structure.
  • the open mechanical structure is a frame support structure having an elongate shape. The force acting on the open mechanical structure and the collapsible flexible bag during deployment, are correspondingly small.
  • the collapsible flexible bag is installed deflated from a floating vessel.
  • the bag is arranged within an open mechanical structure which easily penetrates the water surface when being deployed.
  • the system is designed for fast flooding of water to facilitate easy penetration of the splash zone with a minimum of structural mass and added mass.
  • This method and system requires smaller dimensions of installing equipment such as smaller vessel and smaller lifting cranes. I.e. facilitating installation of a large tank and supporting structure from a relatively small ship and using a relatively small crane. The installation cost is often a dominant cost for these projects, and the present invention requires the use of less cost-driving equipment.
  • the collapsible flexible bag is protected by a protection structure.
  • the protection structure surrounds at least a part of the collapsible flexible bag and being adapted to be fitted within the open mechanical structure.
  • the protection structure has an elongate tubular shape with opening at each side.
  • the protection structure acts as a protection shield to the collapsible flexible bag, facilitates an interface for inplace stability and it may keep the desired shape of the flexible bag.
  • the purpose of such a local MEG storage system according to the present invention is to provide buffer storage for high temporary/instantaneous requirements for MEG consumption, especially such requirements as associated with start-up or shutdown of production.
  • the MEG storage system can be adapted for individual systems and different operational modus.
  • One preferred operational modus of the MEG storage system is a system arranged for oil production without continuous injection of MEG to the production site.
  • This system requires that MEG is only injected during start up and shut down.
  • a small bag can be prefilled before installation or a large bag is advantageously installed in a deflated condition within an open mechanical structure.
  • the charge conduit has to be dimensioned for the average (annual) MEG consumption and not peak consumption during start up or shut down.
  • the MEG storage is safely refilled between transient events.
  • the buffer bag can be used for a gas field with continuous injection of MEG.
  • the buffer bag can be trickle charged by a small line (charge conduit) from a topside platform, and injection of large amount of
  • the charge conduit can be dimensioned for average consumption (annual) and not peak consumption allowing for a more economical charge conduit, lower design pressure, reduced size (amount of material) and previously not allowed/feasible materials
  • the buffer bag allows handling transient events during production so that a short line (discharge conduit) is used for continuous injection and it can be dimensioned for normal use. Typical the discharge line is 2 in and trickle line is 3 ⁇ 4 in.
  • at least one acoustic sensor is arranged on the mechanical structure above the collapsible flexible bag for measuring the amount of MEG inside the bag.
  • the operational level meter volume measurement is in acoustic, i.e. an acoustic sensor measures suggests how much MEG that is available for administrative purposes, like ordering more MEG.
  • An acoustic sensor (presumably more) is placed above the bag in the roof of the open mechanical structure or at the upper part of the structure.
  • the discharge pump when discharging the MEG from the flexible storage bag, the discharge pump may "over-empty" the flexible bag; this may lead to the pressure being lower inside the bag than ambient and cause extrusion of the bag through the suction line of the pump, and subsequent cause total failure of the bag.
  • critical delta p for bag internal overpressure is approximately (less than) 0.1 bar and that the bag is protected from being extruded through the suction side of the discharge pump. It means that mechanical devices to protect bag against internal overpressure will not be sensitive enough.
  • a signal is all that needs to stop the pump when appropriate (be it charge or discharge).
  • At least one first differential pressure gauge is arranged between the inside of the collapsible flexible bag and ambient to protect the bag against internal overpressure.
  • the differential pressure gauge is measuring the pressure in order to stop filling of the bag when the pressure exceeds a predetermined level. It can also be used to trigger/isolate the trickle charger conduits by use of a valve.
  • At least one second differential pressure gauge is arranged on the pump suction line upstream the booster pump for measuring the suction pressure and thereby controlling the emptying of the bag, and providing protection against external overpressure for the bag.
  • a delta P, pressure gauge in the pump suction line gives protection against low suction pressure and shuts the pump down if necessary.
  • a delta P pressure gauge senses the internal pressure against ambient and closes the pump down if necessary.
  • Critical delta p is approximately (less than) 0.1 bar for internal overpressure and approximately 1 bar for external overpressure.
  • the acoustic sensor is a control/operational instrument.
  • Delta P pressure gauges corresponds to a Process Shut Down (PSD) instrument, i.e. respectively operative measurement and production shutdown, the last one is the protection of the plant against self-destruction.
  • PSD Process Shut Down
  • the system further comprises a power source for the booster pump and the power source is a rechargeable electrical battery, trickle charged from a power line in an umbilical.
  • the MEG buffer bag is located in an immediate vicinity of a subsea production site and is used in conjunction with a system of valves and a booster pump to facilitate injection of MEG by remote control.
  • the system of valves also prevents unintended ingress of hydrocarbons from the production facilities into the MEG bag.
  • the at least one safety valve is arranged on the discharge conduit in order to avoid ingress of fluids from the production site into the collapsible flexible bag.
  • valves on/off valves and check valves
  • a system of valves, on/off valves and check valves can be organized to as per fig 2 to eliminate the risk.
  • a common approach to the task is to install check valves as shown. However, check valves (non-return valves) are not accepted in all cases as sufficient isolation.
  • a valve arrangement known as double block and bleed with vent to ambient of minor accumulations of gas, is implemented. This valve arrangement, in combination with pressure sensors which detect any bulid-up of pressure, facilitates active bleeding of gas to ambient to protect the storage facility.
  • the invention also discloses a method of deploying and operating the MEG storage system.
  • the collapsible flexible bag is deployed from a floating vessel in a collapsible condition within an open mechanical structure, wherein the structure is designed for fast flooding with sea-water to facilitate penetration of the sea water surface.
  • At least one charge conduit providing a MEG conduit path between a topside position and the collapsible flexible bag
  • At least one discharge conduit providing a MEG conduit path between the collapsible flexible bag and the subsea production site
  • the at least one charge conduit has a conduit diameter of at least 50% smaller than the diameter of the at least one discharge conduit
  • the present invention also relates to a MEG storage tank system.
  • the tank system comprises;
  • At least one subsea pressure retaining tank comprising a bottom section for holding MEG and a top section for holding a control fluid for controlling the fluid level of the MEG in the at least one subsea pressure retaining tank, which control fluid displays a density which is less than the density of MEG;
  • At least one first conduit providing a fluid conduit path between the top section of the at least one subsea pressure retaining tank, and a topside pressure controlling means for controlling the pressure of the control fluid in the at least one subsea pressure retaining tank; and at least one second conduit providing a fluid conduit path between the topside intermediate feed tank and the bottom section of the at least one subsea pressure retaining tank.
  • the at least one subsea pressure retaining tank is arranged at the seabed, comprising a bottom section for holding the MEG fluid, and a top section for holding a control fluid.
  • the control fluid displays a density which is less than the density of MEG.
  • Suitable control fluid is freshwater, seawater, purge gas, etc., any fluid with a density less than the density of MEG.
  • Purge gas can be natural gas (e.g. sales quality), or Nitrogen N2, depending on platform specifics.
  • the control fluid is seawater. The seawater being free and easily accessible and displays a density which is less than the density of MEG.
  • the MEG and the control fluid are stored inside the at least one subsea pressure retaining tank separated by a flexible membrane.
  • the membrane is a physical membrane made from rubber, plastic, textiles, fibers or other flexible fabric and any combinations thereof.
  • the edge or the outer circumference of the membrane is attached to the inner wall along an inner
  • the membrane is flexible and has a tensile surface (when the membrane is stretched) allowing for either one of the fluids to cover substantially the volume of the at least one subsea pressure retaining tank.
  • the flexible membrane being able to depress the MEG located at the bottom section of the tank, in order to extract the MEG from the tank.
  • the edge of the membrane is attached to the top section of the at least one subsea pressure retaining tank, giving more space to the MEG to be stored.
  • At least one first conduit comprises a fluid conduit path between the top section of the at least one subsea pressure retaining tank and a topside pressure controlling means for controlling the pressure of the control fluid in the at least one subsea pressure retaining tank.
  • the at least one second conduit comprises a fluid conduit path between the topside intermediate feed tank and the bottom section of the at least one subsea pressure retaining tank.
  • the conduit is a riser conduit for filling and discharge of MEG.
  • MEG fluid has only a little higher density than seawater.
  • the MEG storage system comprises a topside intermediate feed tank and at least one subsea pressure retaining tank for the buffer storage.
  • the topside intermediate feed tank being placed on a floating unit, a floating structure or a platform.
  • the at least one subsea pressure retaining tank which is a seabed storage facility, is designed to be constantly fluid filled and thereby withstand ambient pressure at the intended subsea level.
  • the at least one subsea pressure retaining tank is designed to withstand a predetermined internal overpressure.
  • the predetermined pressure for the subsea pressure retaining tank is a pressure in the range from 5 barg to 15 barg over the surrounding sea.
  • barg is the pressure reading relative to current atmospheric pressure. The deeper the storage is arranged, the higher pressure is required for the pressure to be sufficient to force the MEG up into the topside intermediate feed tank.
  • the pressure can be typically 1-5 barg, at 1000 meters depth the pressure can be from 10-20 barg.
  • an elastic membrane is arranged for separating the MEG from the seawater.
  • the seawater of the at least one subsea pressure retaining tank is connected to the topside by means of a first riser conduit arranged with a pressure controlling means in order to fill or extract seawater.
  • seawater will be filled into the top section of the at least one subsea pressure retaining tank. Opposite, by extracting seawater the pressure will be decreased.
  • the MEG is at one end in fluid communication with the bottom section of the at least one subsea pressure retaining tank, and the opposite end with the topside intermediate feed tank by means of at least one second riser conduit for filling and discharging of MEG.
  • a topside pump is arranged for controlling the pressure of the MEG in the at least one second riser conduit.
  • a pressure controlling means in form of a purge pump is located topside and arranged to pump seawater through the at least one first riser conduit and into the top section of the at least one subsea pressure retaining tank.
  • the pressure controlling means is advantageously a purge pump arranged topside on a floating unit, a structure or a platform.
  • the pump is arranged to pump seawater into the at least one first riser conduit.
  • the benefit for arranging a pump topside is that it is easy to install, easy replaceable and allows easy access for maintenance.
  • the at least one first riser conduit is a seawater intake/outlet.
  • the predetermined pressure in the at least one pressure retaining tank and the pressure controlling means displays enough pressure to lift the MEG from the at least one subsea pressure retaining tank to the topside intermediate feed tank. This system avoids the many drawbacks of installing a subsea pump for pumping of the MEG fluid.
  • the topside intermediate feed tank is a tank for storage of MEG fluid ready for use.
  • the tank receives MEG in batches from the at least one subsea pressure retaining tank on a need to basis.
  • From the topside intermediate feed tank the MEG is piped to the MEG booster pumps for transmission to the subsea production site in the normal way.
  • This beneficial system still uses MEG tank arranged topside, but this tank is now reduced in size to a small fraction of the size required if all the
  • MEG were to be stored topsides. For some cases, this may save up to 1500 tons of weight (steel plus MEG volume).
  • the at least one subsea pressure retaining tank will typically have buffer functions, i.e. the steady state flow of MEG is essentially in balance between the lean tank, process, regeneration plant and rich MEG tanks, all of which are located topsides.
  • the buffer volumes subsea is required to fill up the MEG volumes lost regularly in the process and provide the supply of MEG in case of process anomalies, such as downtime of the regeneration plant.
  • the rich MEG tank can also be a buffer type and placed subsea in order to store bigger amount of rich MEG.
  • intermediate feed tank is communicating with the pressure controlling means.
  • the pressure controlling means is a purge pump located topside and arranged to pump the seawater through the at least one first riser conduit and into the seawater at the top section of the at least one pressure retaining tank.
  • the topside intermediate tank is designed with a predetermined amount/volume of MEG stored inside the tank. In case when the volume is less than the predetermined volume, the pump will start to pump seawater into the at least one subsea pressure retaining tank, in order to lift the additional MEG needed from the at least one subsea pressure retaining tank to the topside intermediate feed tank.
  • the pump will extract seawater or allow sea water to flow out from the at least one pressure retaining tank, giving a reverse flow of MEG from the topside intermediate feed tank and into the at least one subsea pressure retaining tank.
  • the reverse flow of MEG does not depend on the pump to be active. By opening the pump/valve the MEG will automatically have a reverse flow.
  • This last method is also applicable when filling of MEG from the topside intermediate feed tank, to the at least one seabed pressure retaining tank.
  • riser is also of particular interest.
  • the subject invention would typically be of interest to floating production platforms using flexible risers for tie-back of production wells.
  • Flexible risers are invariably significant cost items.
  • a riser slot is a valuable asset. It is imperative that riser functionality is kept to a minimum and that the functionality required can be supplied by a single riser.
  • Riser slots can also be a limitation on platforms and the present invention will have a compact riser solution and will only require one or a few riser slots.
  • An acoustic sensor is arranged at the top of the subsea pressure retaining tank in order to detect the MEG level in the tank.
  • a content sensor can also be arranged at the second riser conduit to measure the % water in MEG content.
  • the MEG storage system comprises four subsea pressure retaining tanks located on the same base structure and sharing foundation.
  • a purge pump is arranged to control the pressure and flow of seawater in the at least one first riser conduits.
  • Each individual subsea pressure retaining tank is arranged with an individual first riser conduit and a second riser conduit according to the invention, giving a redundant system.
  • This system with a plurality of subsea pressure retaining tanks is also beneficial in case of maintenance and repair, and also by means of modularization. The last is referred to the simple operation when adding or removing individual tanks.
  • the at least first riser conduit and the at least one second riser conduit can be arranged with required valves and stab connectors.
  • the valves can be intervention valves in order to remove or isolate a tank without disturbing the others; they are ROV operated and affect the system design in minimal extent. This is subsea standard and will be recognized by everyone in the industry as it is, namely RFO (ready for operation, ie commissioning) or maintenance valves.
  • an Umbilical Termination Assembly (UTA) is arranged to the system.
  • the UTA is an interface between the umbilical and the jumpers connecting to the pressure tanks.
  • the UTA and its use and purpose are known to the person skilled in the art.
  • the invention also discloses a method for operating a MEG storage system.
  • the method of operating a MEG storage system comprising:
  • At least one subsea pressure retaining tank comprising a bottom section for holding MEG and a top section for holding a control fluid for controlling the fluid level of the MEG in the at least one subsea pressure retaining tank, which control fluid displays a density which is less than the density of MEG;
  • At least one first conduit providing a fluid conduit path between the top section of the at least one subsea pressure retaining tank and a topside pressure controlling means for controlling the pressure of the control fluid in the at least one subsea pressure retaining tank;
  • At least one second conduit providing a fluid conduit path between the topside intermediate feed tank and the bottom section of the at least one subsea pressure retaining tank; which method comprises the step of;
  • the intermediate feed tank is in communication with the pressure controlling means in order to control and regulate the amount of MEG in the topside intermediate feed tank, which method further comprises the steps of:
  • a topside pump for controlling the pressure of the MEG in the at least one second conduit.
  • the at least one subsea storage tank comprises a flexible membrane separating the bottom section from the top section of the subsea pressure retaining tank.
  • the control fluid is preferably seawater and the pressure controlling means is preferably a purge pump.
  • the at least one subsea pressure retaining tank is designed to withstand an internal pressure in the range from 1 barg to 20 barg.
  • the MEG storage system comprises of four individual subsea pressure retaining tanks, each with individual first and second riser conduits.
  • Fig 1 a shows a typical design of a MEG buffer tank according to the remote storage embodiment of the invention. shows another embodiment of the present invention with buffer bag together with the charge and discharge conduit. shows schematically a MEG buffer storage, pressure isolation system and booster/injection facilities for the remote (on the production site) MEG storage embodiment. shows an embodiment of the present invention where the subsea pressure retaining tank is arranged with a membrane separating MEG and seawater.
  • Fig. 4 shows a schematic diagram of the MEG storage system with four
  • FIG. 1 shows an embodiment of a MEG storage system, according to the present invention.
  • the MEG storage system is designed for subsea storage of MEG in an immediate vicinity of a subsea production site.
  • the system comprising a collapsible flexible bag 31 with at least one charge conduit line 32 and at least discharge conduit line 33.
  • the at least one charge conduit 32 providing a MEG conduit path between a topside position and the collapsible flexible bag 31, and at least one discharge conduit 33 providing a MEG conduit path between the collapsible flexible bag 31 and the subsea production site.
  • the collapsible flexible bag 31, preferably made of rubber, is arranged within an open mechanical structure 35.
  • the open mechanical structure 35 being a well flooded frame structure 35.
  • the flexible bag 31 when in use is forming a single barrier between MEG and ambient water.
  • At least one booster pump 36 is arranged on the discharge conduit 33 for raising the MEG pressure to a level permitting injection of MEG into the production site.
  • the at least one charge conduit 32 has a conduit diameter smaller than the diameter of the at least one discharge conduit 33, allowing the bag 31 to be trickle charged from the topside.
  • Figure la also shows a protection structure 34 adapted to be fitted around the collapsible flexible bag 31.
  • the protection structure 34 in figure la has perforated holes at the top section.
  • Figure lb shows a more detailed overview of the present invention.
  • the collapsible flexible bag 31 is arranged within an open mechanical structure 35.
  • the bag 31 is arranged in an inclined position allowing MEG to be collected at one side, wherein said discharge conduit 33 is connected to the bag 31 at said one side.
  • a pressor sensor 38 or pressure gauge 38 is arranged on the pump suction line upstream the booster pump 36 for measuring the suction pressure and thereby controlling emptying of the bag 31, and protection against external overpressure for the bag 31.
  • At least one first differential pressure gauge 38 is arranged between the bag 31 inside and ambient to protect the bag 31 against internal over pressure.
  • At least one acoustic level sensor 13 is arranged on the open mechanical structure 35 above the collapsible flexible bag 31 for measuring the amount of MEG inside the collapsible flexible bag 31.
  • Figure lb also shows a safety valve 39 is arranged on the discharge conduit 33 in order to avoid ingress of fluids from the production site into the collapsible flexible bag 31.
  • FIG. 2 shows schematically a MEG buffer storage, pressure isolation system and booster/injection facilities for the remote (on the production site) MEG storage embodiment.
  • Figure 3 shows an embodiment of a MEG storage system, according to the present invention.
  • the system comprises a topside pump 5 arranged to control pressure and flow of a control fluid 3.
  • the control fluid 3 is preferably seawater.
  • Seawater 3 is led through a first riser conduit 9 to a subsea pressure retaining tank 1.
  • the first riser conduit 9 has an intake/outlet connection 20 for intake and extraction of seawater 3.
  • the subsea pressure retaining tank 1 is arranged at the seabed for storage of MEG 2.
  • the subsea pressure retaining tank 1 comprises a flexible membrane 12 arranged internally for separating the MEG 2 from the seawater 3.
  • the content of the pressure tank 1 can be divided into a top section with seawater, a flexible membrane 12 separating the two fluids, and a bottom section 2 with MEG 2.
  • the subsea pressure retaining tank 1, which is a seabed storage facility, is designed to be constantly fluid filled and thereby withstand ambient pressure at the intended subsea level. Additionally the subsea pressure retaining tank 1 is designed to withstand a predetermined overpressure on the inside tank 1.
  • the predetermined pressure for the subsea pressure retaining tank 1 is a pressure in the range from 1 barg to 20 barg over the surrounding sea, depending on the depth. The deeper the storage is arranged, the higher pressure is required for the pressure to be sufficient to force the MEG 2 up into the topside intermediate feed tank 1 1.
  • the top section of the subsea pressure retaining tank 1 containing seawater 3, is connected by means of a first riser conduit 9 to a topside purge pump 5.
  • the MEG 2 at the bottom section of the subsea pressure retaining tank 1 is connected to a topside intermediate feed tank 11 by means of a second riser conduit 10 for filling and discharging of MEG.
  • the purge pump 5 located topside is arranged to pump the seawater 3 into the pressure retaining tank 1.
  • the pressurized seawater 3 is entering the top section and pushing the elastic membrane 12 towards the MEG 2 in the bottom section, in order to extract and lift the MEG 2 from the subsea pressure retaining tank 1 to the topside intermediate feed tank 11.
  • An acoustic sensor 13 is arranged at the top of the pressure retaining tank 1 in order to detect the MEG 2 level in the tank 1.
  • a content sensor 14 is also arranged to measure the water 3 in MEG 2 content.
  • the Fig. 3 also shows the first riser conduit 9 and the second riser conduit 10 is connected each to a connection point 7, 8 for respectively seawater line and MEG 2 line.
  • a level control 22 is arranged at the topside intermediate feed tank 11 in order to control and measure the desired level of MEG 2 in the tank.
  • An inlet pipe 21 is arranged for the external supply of MEG 2, accordingly a feed line 15 is also located in the intermediate feed tank 15 for the MEG 2 injection system.
  • FIG. 4 shows the MEG storage system with four subsea pressure retaining tanks 1.
  • the system comprises four individually pressure retaining tanks 1, each individually connected to a first riser conduit 9 and a second riser conduit 10, thus providing a system robust against single failures. This means that by a fault in one subsea pressure retaining tank 1, the other tanks 1 still in god condition, can continue operation without the cost and time delays of a subsea intervention.
  • a purge pump 5 is arranged to control the pressure and flow of seawater 3 in the at least one first riser conduit 9.
  • a topside pump (not shown) can also be arranged for controlling the pressure of the MEG 2 in the at least one second riser conduit 10.
  • the at least one second riser conduit 10 is connected to the bottom section of each individual subsea pressure retaining tank 1, providing individual MEG fluid conduit paths to the topside intermediate feed tank 11.
  • the at least first riser conduit 9 and the at least one second riser 10 conduit can be arranged with required valves and stab connectors as shown in figure 2.
  • the valves can be intervention valves in order to remove or isolate a tank without disturbing the others; they are ROV operated and affect the system design in minimal extent.
  • an Umbilical Termination Assembly (UTA) is arranged to the system.
  • the UTA is an interface facility for connection of umbilical conduits to the jumpers.

Landscapes

  • Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Mining & Mineral Resources (AREA)
  • Geology (AREA)
  • Mechanical Engineering (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Physics & Mathematics (AREA)
  • Environmental & Geological Engineering (AREA)
  • Fluid Mechanics (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • General Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Chemical & Material Sciences (AREA)
  • Pharmaceuticals Containing Other Organic And Inorganic Compounds (AREA)
  • Nitrogen Condensed Heterocyclic Rings (AREA)
  • Other Liquid Machine Or Engine Such As Wave Power Use (AREA)
  • Packages (AREA)

Abstract

La présente invention concerne un stockage sous-marin de MEG dans un voisinage immédiat d'un site de production sous-marin, le système comprenant un sac flexible repliable ; et - au moins un conduit de charge fournissant un trajet de conduit de MEG entre une position supérieure et le sac flexible repliable, - au moins un conduit d'évacuation fournissant un trajet de conduit de MEG entre le sac flexible repliable et le site de production sous-marin. Le sac flexible repliable est disposé dans une structure mécanique ouverte, le sac flexible, en utilisation, formant une barrière unique entre MEG et l'eau ambiante, et au moins une pompe de surpression étant disposée sur le conduit d'évacuation pour élever la pression de MEG à un niveau permettant l'injection de MEG dans le site de production, et l'au moins un conduit de charge ayant un diamètre de conduit au moins 50 % plus petit que le diamètre de l'au moins un conduit d'évacuation.
PCT/EP2016/064683 2015-06-26 2016-06-24 Système de stockage de meg, et procédé de déploiement et de fonctionnement de système de stockage de meg WO2016207359A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
NO20150842A NO340075B1 (en) 2015-06-26 2015-06-26 A MEG storage system and a method for storing MEG
NO20150842 2015-06-26

Publications (2)

Publication Number Publication Date
WO2016207359A2 true WO2016207359A2 (fr) 2016-12-29
WO2016207359A3 WO2016207359A3 (fr) 2017-02-02

Family

ID=56363819

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/EP2016/064683 WO2016207359A2 (fr) 2015-06-26 2016-06-24 Système de stockage de meg, et procédé de déploiement et de fonctionnement de système de stockage de meg

Country Status (2)

Country Link
NO (1) NO340075B1 (fr)
WO (1) WO2016207359A2 (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2018172497A1 (fr) * 2017-03-24 2018-09-27 Nov Subsea Products As Système et procédé pour séparation sous-marine d'eau produite
WO2020049232A1 (fr) * 2018-09-07 2020-03-12 Saipem S.A. Procédé et dispositif de détermination du volume de liquide restant a l'intérieur d'une poche souple de distribution de liquide
WO2020226507A1 (fr) * 2019-05-07 2020-11-12 Equinor Energy As Stockage immergé de fluides hydrocarbures

Family Cites Families (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR96543E (fr) * 1967-12-28 1972-10-20 Bethlehem Steel Corp Procédé et appareil pour le magasinage de pétrole sous l'eau.
DE1807295A1 (de) * 1968-11-06 1970-05-21 Hermanns Wilhelm Verfahren und Vorrichtung zum Entleeren von mit Schuettgut,Fluessigkeiten oder Pasten gefuellten Containern
NL8002206A (nl) * 1980-04-16 1981-11-16 Beene Frankema Inrichting voor opslag onderwater of ondergronds van aardolie, brandstof en dergelijke vloeistoffen.
GB2225755A (en) * 1988-10-29 1990-06-13 Stanley Ball An intergrated offshore safety system
AU2003259820A1 (en) * 2002-08-14 2004-03-03 Baker Hughes Incorporated Subsea chemical injection unit for additive injection and monitoring system for oilfield operations
NO20101793A1 (no) * 2010-12-21 2012-01-16 Seabox As Teknisk system, fremgangsmåte og anvendelser for dosering av minst ett flytende behandlingsmiddel i injeksjonsvann til en injeksjonsbrønn
GB2499804A (en) * 2012-02-28 2013-09-04 Monobuoy Company Ltd Collapsible fluid receptacle weighted to overcome buoyancy of contents
US20150246770A1 (en) * 2012-10-18 2015-09-03 Korea Advanced Institute Of Science And Technology Large scale subsea storage tank and method for constructing and installing the same
US9079639B2 (en) * 2013-04-06 2015-07-14 Safe Marine Transfer, LLC Large volume subsea chemical storage and metering system

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2018172497A1 (fr) * 2017-03-24 2018-09-27 Nov Subsea Products As Système et procédé pour séparation sous-marine d'eau produite
WO2020049232A1 (fr) * 2018-09-07 2020-03-12 Saipem S.A. Procédé et dispositif de détermination du volume de liquide restant a l'intérieur d'une poche souple de distribution de liquide
FR3085750A1 (fr) * 2018-09-07 2020-03-13 Saipem S.A. Procede et dispositif de determination du volume de liquide restant a l'interieur d'une poche souple de distribution de liquide
US11874151B2 (en) 2018-09-07 2024-01-16 Saipem S.A. Method and device for determining the volume of liquid remaining inside a flexible liquid-dispensing pouch
WO2020226507A1 (fr) * 2019-05-07 2020-11-12 Equinor Energy As Stockage immergé de fluides hydrocarbures

Also Published As

Publication number Publication date
NO340075B1 (en) 2017-03-06
NO20150842A1 (en) 2016-12-27
WO2016207359A3 (fr) 2017-02-02

Similar Documents

Publication Publication Date Title
AU2020203153B2 (en) Subsea storage tank, method of installing and recovering such a tank, system, method to retrofit a storage tank and method of refilling a subsea storage tank
US9079639B2 (en) Large volume subsea chemical storage and metering system
US6230809B1 (en) Method and apparatus for producing and shipping hydrocarbons offshore
US20060000615A1 (en) Infrastructure-independent deepwater oil field development concept
US3292695A (en) Method and apparatus for producing underwater oil fields
AU2010273447B2 (en) Production riser
US9878761B2 (en) Large subsea package deployment methods and devices
US6817809B2 (en) Seabed oil storage and tanker offtake system
WO2016207359A2 (fr) Système de stockage de meg, et procédé de déploiement et de fonctionnement de système de stockage de meg
US20220099253A1 (en) Gas storage system
DK201670065A1 (en) Deepwater production system
US6019174A (en) Method and apparatus for producing and shipping hydrocarbons offshore
MX2013015210A (es) Sistema modular de exploracion y produccion que incluye una embarcacion extendida para servicio de prueba de pozo.
KR20080070412A (ko) Ｌｎｇ 재기화 선박용 모의 부이
US20180257117A1 (en) Method of Emptying an Undersea Fluid Transport Pipe That Is Submerged and Full of Water
ITMI20131753A1 (it) Procedimento per trasportare fluidi di estrazione quali per esempio gas naturale, petrolio o acqua, e veicolo sommergibile per attuare tale metodo.
IT201800002120A1 (it) Sistema e metodo per collegare in modo temporaneo una stazione subacquea ad un servizio di superficie
KR101488273B1 (ko) 아이솔레이션밸브
AU735485B2 (en) Method and apparatus for producing and shipping hydrocarbons offshore
WO2024136668A1 (fr) Manipulation de fluide en mer
Davison et al. Fast-Track Development of Deepwater Kuito Field, Offshore Angola
KR101462580B1 (ko) 해양구조물의 히브컴펜세이터 제어시스템
Carneiro Barracuda Field: New Records for Turret Moored FPSO's
GB2356183A (en) Method and apparatus for producing and storing hydrocarbons offshore

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 16735837

Country of ref document: EP

Kind code of ref document: A2

NENP Non-entry into the national phase in:

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 16735837

Country of ref document: EP

Kind code of ref document: A2