FR2674608A1 - METHOD OF TRANSPORTING FLUIDS - Google Patents

Abstract

The invention relates to a method for transporting a fluid through a mass of liquid by using a collapsible pipe (7). The fluid is initially compressed to a pressure equal to or slightly higher than the ambient pressure and transported by the pipe (7) from a point (A) to a point (B) lying at a shallower depth. During transport, the pressure of the fluid is kept equal to or slightly higher than the ambient pressure as the pipe rises in the liquid. This process is particularly suitable for transporting gas in seawater.

Description

The present invention relates to a method for transporting a fluid to

  through a mass of liquid, in particular a process for transporting gas through

Seawater.

  It is often necessary to transport crude oil or gas from one facility to another, frequently over great distances On land, conventional techniques involving oil and gas pipelines can be used. Alternatively, the long-distance transport by liquefaction and LNG tanker transport is the normal process for gas, or the transport is carried out by very large crude oil carrier ( TGTB) in the case of

crude oil.

  Rigid pipelines can cause problems when the seabed is crossed by abyssal ravines The use of oil tankers for transport requires expensive facilities on land and for

boarding.

  In addition, the latest developments in offshore drilling have required the transport of gas, often extracted together with oil, from offshore deepwater facilities, creating a need for

high pressure in deep water.

  The Claimant has just found that by

  fluids in a flexible hose that can

  at pressures equal to or slightly above the ambient pressure, they could be transported

  deep over long distances in seawater.

  Accordingly, in accordance with the present invention, there is provided a method of transporting a

  fluid in a mass of liquid, said method

  both: (a> to make a compressed fluid arrive in a

  first point at equal or slight pressure

  higher than the ambient pressure of said liquid and (b) passing said fluid through a pipe capable of collapsing to a second point, located at a lesser depth than the first point, while the pipe in question rises in the mass of liquid to maintain the pressure of the fluid at a value equal to or slightly greater than the ambient pressure of the liquid. The process of the present invention is particularly suitable for the transport of gas in a mass

of seawater.

  The present invention exploits the difference in density between the fluid, for example oil, gas or their mixtures, and the liquid, for example seawater to allow the fluid to rise naturally to the

area.

  Collapsible hoses, the use of which

  the process of the present invention are pipes which have a working pressure, relative to the ambient pressure, of between 0.2 and 2.5

M Pa.

  A particularly suitable type of pipe is a pipe laying flat, for example a pipe

fire.

  The pipe may have a suitable working diameter depending on the volume of fluid to be transported, for example

example of 15 to 60 cm.

  A representative construction of the pipe would include an impermeable liner compatible with the pumped fluid, an armature, for example Kevlar, steel wire, "nylon" or polyester and an outer shell

  stubborn water-resistant, for example polyurethane.

  Alternatively, the collapsible pipe may be a series of articulated metal membranes. The fluid is initially compressed to a pressure equal to or slightly greater than the ambient pressure of the liquid and below the working pressure of the fluid.

hose can sag.

  For example, in water at a depth of 1000 m, the ambient pressure is about 10.3 M Pa and a pipe set at an internal pressure of 0.5 M Pa relative to the ambient pressure can be used to transporting a fluid at an absolute pressure of between 10.3 and

, 8 M Pa.

  The fluid can be compressed at a station equipped with a compressor installed at an intermediate depth in the water It can be at the same depth as the start of the pipe that can sag or it can preferably be at a depth of one little less, so that the compressed fluid is then discharged downwards by means of a riser leading to the

departure of the pipe.

  If the fluid to be transported is gas, you can

  use a compressor running on electricity.

  The fluid can be transported to the compressor by conventional means from a pipeline or

  offshore production facility.

  The compression station can be docked or

dynamic positioning.

  The compression station can be located normally at a depth of about 1000 m, the deformable pipe positioned between 1000 and 2000 m of water being

  connected to the station, if necessary, by a riser.

  The riser may be one piece or it may be an assembled construction, so

  to allow assembly and installation.

  In a representative case in which the fluid is a gas, the gas flows along the collapsible pipe which is connected to a second station located at a lesser depth. This station can be connected to a receiving installation or it can may be another

  compression station if another transport is desired.

  As the gas flows into the pipe, the

  pressure drops due to losses due to friction.

  Thus, on a 100 km pipeline, the internal pressure can fall to 10 M Pa To ensure the transport of gas through the pipe and to maintain the latter in equilibrium with the external pressure, the pipe must rise in the water by example of 2000 m up to a depth of 1000 m on

this distance.

  The gas pressure is balanced against the external ambient pressure and is therefore maintained at a value equal to or slightly greater than the pressure

  ambient, for this balance to remain.

  The hose can operate fully or partially inflated on part or all of its length As the pressure in the hose decreases with respect to the ambient pressure, the hose flattens and its cross-section is reduced The pressure of the gas

  therefore climbs into the pipe and the cross-section

dirty of the latter is restored.

  As the pipe reaches smaller depths and the pressure inside the pipe

  decreases, a gas or a multi-phase fluid relaxes.

  In such circumstances, it may be advantageous

  to increase the nominal diameter of the pipe.

  To maintain the pipe in position, it can be added buoys and ballast in a predetermined form For example, we can use buoys connected to each other by means of a

catenary structure.

  The pipe may also be partially suspended from a cable which serves to absorb a portion of the tensile loads. When filled with gas, the pipe and weights can be arranged in such a way that the buoyancy

  of the set is approximately neutral.

  Alternatively, the pipe may be suspended or

  attached to a conventional pipe system.

  During commissioning, the hose sinks due to high external pressures. It may be necessary for some buoyancy and suspension on the surface to hold the hose in position. In case of damage, the pipe collapses due to the pressure drop When the compressors are stopped, the pipe collapses and no further leakage occurs, so that the risk of pollution of

the environment is reduced.

  If the fluid to be transported is crude oil, the compressors can be replaced by electric pumps. The method of the present invention can also be used offshore to transport drilling fluids, for example oil, gas and water to a production facility that can be a platform.

  on stretched cable legs or a moored ship.

  For example, at a depth of the 2000 m wellhead, the produced drilling fluids would be pressurized to approximately 20.5 M Pa and transported by a collapsible pipe to

  near the surface for further processing.

  Several subsea wells can thus be connected to the surface by collapsible pipes. For example, at a depth of about 50 m below the surface, drilling fluids can enter a vertical separator that can make part of a system of

associated floating production.

  In this case, the possibility of operating, in accordance with the process of the present invention, a range of 10 to 20 km in diameter is envisaged by using collapsible pipes. Fluid can also be transported from the bottom to a shore facility by the use of the mainly upward sea-bottom gradient to guide and support the pipe so as to maintain it in position at a suitable depth, the fluids can be routed to facilities at

  earth by a conventional rigid pipe.

  Normally, oil extracted from submarine deposits flows to the surface facility by means of conventional towers or risers.

  oil is transported by an oil tanker

  shuttle or pipeline The associated gas is compressed and taken to the seabed by a rigid riser. The gas then flows into a collapsible pipe according to the method of the present invention. The pipe may be wholly or partially inflated. and placed along the rising gradient of the seabed At a suitable depth, the collapsible pipe can join a conventional rigid pipeline which

  can be part of an existing platform.

  The collapsible pipe operates at a low pressure relative to the ambient pressure, allowing a relatively inexpensive flat pipe to be

  instead of a pipeline resistant to high pressures.

  The use of a collapsible pipe offers a significant advantage over conventional steel pipework because it can be laid easily and quickly in deep water, for example by unreeling

  pipe and ballast a chain from a barge.

  The method of the present invention can also be used to transport fluids over

great distances.

  Accordingly, in another of its aspects, the present invention provides a method for transporting a fluid through a body of liquid, which method comprises (a) delivering a compressed fluid to a fluid

  first point at equal or slight pressure

  higher than the ambient pressure of said liquid, (b) transferring the fluid through a pipe that can collapse to a second point, located at a shallower depth than the first point, while the pipe rises in the mass of liquid to maintain fluid pressure at or slightly above the ambient liquid pressure, (c) recompressing the fluid at a pressure equal to or slightly greater than the ambient pressure of said liquid at a third point at a further great depth as the second point, (d) to send the fluid to this third point, and (e) to repeat steps (b), (c) and (d) as necessary to accomplish the transport of the

fluid.

  The fluid transport system can be suspended between two bodies of water and therefore does not have to withstand the crushing loads of pipelines in very deep water. The system can be used at any water depth and, therefore, abyss pits inaccessible to rigid pipelines can be crossed. Further details of the present invention will be apparent from the accompanying drawings which are schematic representations of gas transport in seawater, with

  use of the process of the present invention.

  In Figure 1, gas from an offshore generation facility is transported by pipeline (1) to a station (2) equipped with a compressor located at a depth of approximately 500 m. riser (4) to a motor unit (3) floating at the surface The power unit comprises a gas turbine or other gas driven power generator, which operates a generator, the fuel of the gas turbine from the gas contained in the pipeline The group may also contain a battery safety power supply and control, control and transmission equipment The riser (4) contains an electrical power cable, a gas supply pipe and

  a control transmission cable.

  The compressor station (2) comprises a

  compressor and a control group with electric motor.

  The gas from the pipeline (1) is compressed at a pressure of about 10.5 Pa and descends through the rigid riser (5) to a position A at a depth of about 1000 m. The riser (5) can be of one piece or its structure can be

  made by doubling to facilitate assembly.

  The set comprising the compressor station and the ascending column can be positioned if necessary

  by anchoring in (6) or we can proceed to a position-

dynamically.

  The gas flows from position A to position B in the collapsible pipe (7). The pipe can be held in position by a series of cables (8) attached to floating buoys (9). in addition to being provided by the weights (10), or the pipe can be suspended from a cable (11) Alternatively, the pipe can be held in position by cables (15) attached to the

bottom of the sea.

  The gas arrives in position B with a pressure of approximately 5.5 M Pa. If a subsequent transport is desired, the gas is recompressed at B by means of the compressor station (12), transferred downwards by the riser ( 13) in position (C) and transported to the

high through the pipe (14).

  Repetition of the cycle allows the transport of gas over long distances, regardless of the water depth. In Figure 2, the gas is transported from a seabed position (20) to an installation (21) on the ground by means of a collapsible pipe (22).

  as well as a rigid pipeline (23).

  The gas is introduced at a pressure slightly above the seafloor pressure at point (20) by a rigid riser (24) connected to a compressor station (25) positioned on the surface. 'collapse, which can be ballasted at the bottom of the sea to prevent its rise under the ascensional effect of gas It can be ballasted by means of bags (26) filled with sand or, alternatively, we can use a cable or

a heavy steel chain.

  The natural gradient of the seabed supports the pipe and helps to hold it in position The pipe generally tends to ascend, allowing small profiles or ravines (28) to descend when a suitable position is reached (27). ) has been

  the gas can be transported to

  on the ground by way of the rigid pipeline (23) which can

  be part of an existing pipeline system.

  Alternatively, the gas can be delivered to a

  existing offshore installation, for example at a platform

  form (29) where it can be processed and / or further compressed before being introduced into the pipeline system (23)

existing.

Claims (7)

  A method of transporting a fluid through a mass of liquid by means of a pipe which can be   characterized in that it consists of: (a) delivering a compressed fluid into a   first point (A) at equal or slight pressure   higher than the ambient pressure of said liquid and (b) passing said fluid through a pipe (7) capable of collapsing to a second point (B) located at a lesser depth than the first point (A), while that the pipe (7) in question rises in the mass of liquid to maintain the pressure of the fluid at a value equal to or slightly greater than the pressure ambient of the liquid.   Process according to Claim 1, characterized in that the fluid is compressed to a lower depth than the first point and is sent   down towards this first point.   Process according to Claim 1 or 2, characterized in that the hose can settle at a working pressure with respect to the ambient pressure in the range of 0.2 to 2.5 M Pa.   Process according to Claim 3, characterized in that the collapsible pipe is a flat pipe.   Process according to any one of   preceding claims, characterized in that the pipe   collapsible is totally or partially inflated   on part or all of its length.   6 Process according to any one of   preceding claims, characterized in that the pipe   collapsible is held in position by means External.   Process according to Claim 6, characterized in that the external means consist of   buoys, chains or cables.   Process according to Claim 6, characterized in that the external means are offered by   the mainly ascending gradient of a seabed.   9 A method of transporting a fluid through a body of liquid, characterized in that it consists of: (a) causing a compressed fluid to arrive in a   first point at equal or slight pressure   higher than the ambient pressure of said liquid, (b) transferring the fluid through a pipe that can collapse to a second point, located at a shallower depth than the first point, while the pipe rises in the mass of liquid to maintain fluid pressure at or slightly above the ambient liquid pressure, (c) recompressing the fluid at a pressure equal to or slightly greater than the ambient pressure of said liquid at a third point at a further great depth as the second point, (d) sending the compressed fluid to this third point, and (e) repeating steps (b), (c) and (d) as necessary to accomplish the fluid transport. Process according to any one of   preceding claims, characterized in that the fluid   is a gas and the liquid is seawater.