GB2066095A

GB2066095A - A device for recovery of fluids from a subaqueous leak

Info

Publication number: GB2066095A
Application number: GB8032521A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1979-10-11
Filing date: 1980-10-08
Publication date: 1981-07-08
Also published as: NL8005648A; NO803032L; DK431380A

Abstract

A device for the recovery of fluids from underwater leaks 17 comprises a container 18 into which a mixture of crude oil, water and natural gas can be charged for settling into three distinct layers. The gas fraction is discharged from the top of the tank by outlet 28. The crude oil is withdrawn through a conduit 22, communicating with the container at an intermediate level. The container is preferably bottomless but could have a bottom in which case a lower discharging system is provided for the water. The container is placed directly over the leak 17 or, as an alternative, a collecting bell is employed which communicates with the container by a riser discharging into an upper section of the container to reduce disturbance of settled layers within the container. The riser opens into the container tangentially to induce centrifugal separation (Figs. 2,3 not shown). <IMAGE>

Description

SPECIFICATION A device for recovery of fluid minerals from a subaqueous leak The invention relates to a device for recovery of fluid minerals, particularly of crude oil discharged from a pipeline leakage or from a well underneath water surface, of the type having a container in which water separates from the crude oil due to its greater density, and with a first conduit for removal of the crude oil from the container.

It is known to provide a tank or bell-shaped container above an oil well or pipeline leak from which an uncontrolled flow of crude oil discharges. The container is normally open at the bottom. Within the tank, the crude oil can separate from water because of the difference in specific weight of the two materials. The lighter crude oil is then removed from top of the container.

In practice, an arrangement of this type is to be found unsatisfactory at least on the grounds that it often happens that a gaseous phase or fraction of the minerals discharges also. The gaseous phase makes it difficultforthe liquid phases to settle into distinct layers. It is further of disadvantage that the phase suspension of crude oil and natural gas removed from the container does not possess any practical utility until subjected to separation of the two phases. It is further very difficult, on use of the known containers, to control in satisfactory fashion pressure conditions within the interior of the container which, among other things, is desirable due to the fact that the gaseous phase has a considerable influence on the overall operation of the container.It is also disadvantageous that the phase mixture charged into the container from below constantly disturbs the already partly settled phases within the container. The desirable settling process is thus severely disturbed. Also, the separation of crude oil from natural gas within the container is not possible since the removal takes place from the top of the container and thus the liquid phase and the gaseous phases are removed simultaneously by the same conduit.

It is therefore an object of the invention to provide an arrangement of the type mentioned at the outset with simple means such that the separation of the gaseous phase from the liquid phase can be effected still within the interior of the container in an effective way. In order to solve the above object, it is proposed by the invention that a first conduit be arranged to communicate with the container at an intermediate level thereof and that a second conduit for removal of natural gas be connected to the container at an upper level thereof.

By such arrangement, the separation of all three phases is made possible within the interior of the container, so that the phases discharged upwards, at least the liquid oil phase, can be conveyed directly to a further processing as the phases are already in a generally pure form, ready for subsequent treatment.

The separation of the individal phases can be considerably improved and, above all, expedited when, in accordance with a further feature of the invention, the feeding of at least a substantial portion of the still unsettled phases of water, crude oil and natural gas is effected into the container by an upright conduit or riser which discharges into the container above the top level of the eventually formed crude oil phase.

The three-phase mixture flowing into the container under high pressure thus passes through the liquid phases already contained within the container, via a riser without disturbing the settled phases, so that the liquid phases are not intermixed. The three-phase suspension discharged at the upper end of the riser expands within the upper region of the container such that the two liquid phases quickly fall down due to the force of gravity while the gaseous phase remains in the upper section of the container.

According to another feature of the present invention, a collection bell is provided for placement over the leak, with the lower end of the riser communicating with the collection bell, while the container is disposed at a region of a smaller water depth or on the surface.

It depends on the local wind and motion of the sea conditions whether the container should be arranged immediately above or immediately below the sea surface and whether the collecting bell should be placed directly over the well or the leakage orwhetherthe container is to be brought into an immediate communication with same, without the use of a collecting bell. The additional use of a collecting bell will certainly be of advantage particularly under rough operational conditions.

In a further embodiment of the invention, the interior of the container or of the collecting bell is arranged to communicate with a by-pass conduit terminating in the surrounding water which, on floating of the arrangement over the well or the leakage, stays open and, eventually, can be closed by a valve.

The open by-pass conduit facilitates the transport of the arrangement through water up to the proposed operation site as the buoyancy or pressure forces building inside of the container or of the collecting bell can be removed by flooding the interior thereof.

It is further of advantage if the collecting bell is convergent upwardly in a funnel-like fashion and when the funnel-shaped taper is provided with an insert extending across the flow in a Venturi-nozzle fashion. The insert acts against the crude oil accumulation on its entry into the collecting bell and enables the lifting of even small crude oil droplets due to the Venturi effect.

Both in the two conduits and in the riser, valves can be arranged by which the respective flow crosssections can be changed and the pressure and flow velocity controlled. If desired, such valves can be also used to fully close the respective conduit. A control valve disposed in the first conduit can preferably form a part of a control circuit by which the level of the crude oil phase within the container can be checked. Similarly, a control valve disposed in the same conduit can form a part of a control circuit by which the pressure and/or level of the interface between the crude oil and the natural gas layers within the container can be controlled. Corresponding measuring instruments can be used at suitable places without difficulties.

In a further embodiment of the invention, a gener ally vertical partition is provided between the first conduit and the interior of the container to provide a settling zone separated from but communicating with the remaining section of the interior. The most advantageous arrangement of such partition wall or walls depends from case to case on the particular application of the arrangement. A further improve ment of the separation process can be obtained such that approximately at the level of the upper end of the riser be provided generally horizontal breaker surfaces. Such surfaces have the effect that the kinetic energy of the liquid phases falling down within the container dissipates before the phases reach the already settled and at least partly separated fractions.The breaker plates are arranged at an inclination securing the outflow of the liquid phases in such a way that the settled and already separated layers are disturbed as little as possible.

Furthermore, it is of advantage in this connection to provide that the breaker plates form a part of a spiral-shaped flow channel having an approximately upright axis, and forming the flow channel such that the liquid phase mixture flowing down the spiral is accelerated. The thus developed centrifugal force is effective to provide a first separation effect between the liquid phases.

It depends on the particular application in which way the arrangement produced according to the present invention is to be secured with respect to the well or the leakage. At least in some cases, the anchoring to sea bed will have to be considered. In such case, it is suitable, according to a furtherfeature of the invention, if the container and/or the collecting bell is anchored to the sea bed in a resiliently yieldable fashion. For this purpose, tension springs are particularly suitable for use in the corresponding holding assemblies.

In general, it will be suitable not to provide the container and/or the collecting bell with float chambers. On the contrary, separate float members can be attached to the container or to the collecting bell such as to secure that the floating state of same is as stable as possible.

It is further within the scope of the invention to provide a platform and supporting columns extending from same down to the sea bed with the container and/or the collecting bell movably secured to the columns for selective displacement in vertical direction, so that the respective desired level of the devices can be achieved.

In view of the fact that the natural gas-air mixture is relatively strongly flammable or explosive, it is preferred that the device also comprise means for filling the interior of the container with inert gas for the time period of its placement into operational position and during its assembly at such sire.

The conduits can be produced either from rigid tube sections or, according to another feature of the invention, they also can be formed, at least partly, by generally self-supporting, resiliently yieldable hoses.

By such arrangement, relative movements between the individual elements of the device can be compensated for in a particularly simple way. Also, on use of such hoses, the inner flow cross-section can be adjusted to the respective hydrostatic pressure.

Several preferred embodiments of the invention will now be described with reference to the accom panying drawings, in which: Figure 1 is a diagrammatic vertical section of a first embodiment of the device with the container dis posed immediately above a well; Figure 2 isa diagrammatic representation similar to fig. 1, of a further embodiment utilizing a collect ing bell; Figure 3 is a section Ill-Ill of Fig. 2; and Figure 4 is a diagrammatic representation similar to Fig. 1, of a further embodiment of the device.

Even though several embodiments are shown, they are provided with certain parts which serve the same purpose and are therefore referred to with identical reference numerals.

The embodiment according to Figure 1 will be described first. A platform 10 floats due to float elements 11 such that the platform protrudes slightly above the sea level 12. The float elements 11 are secured by cables 13 to the sea bed 14 by secure ment to foundations 15. Integrated in the cables 13 are tension springs 16 shown only in a diagrammatic way, which produce a certain resiliency of the anchorage.

Above a well 17 in the sea bed 14 is arranged a container 18 open at the bottom and tapering in its upper region in a funnel-like fashion. Secured to the container abouts its periphery at an equidistant spacing are floats 19 which are also anchored to the foundations 15 by cables 20. In the cables 20 are integrated tension springs 21 so that the anchorage of the container also has a certain resiliency.

A first conduit 22, shown in diagrammatic way only, communicates side-wise with the container 18 approximately at its intermediate level and leads upwards up to the platform 10. At the platform, a valve23 is interposed in the conduit 22 and is controlled by a level controller24. The latter, in turn, operates in common with two sensors25, each disposed in the container 18 at such a level as to provide spacing between the sensors corresponding to the expected thickness of the separated crude oil layer. Underneath the interface 26 is water. The oil level extends from the interface 26 up to the interface27 disposed at a higher level.

A second conduit28 communicates with the top of the container 18 and extends likewise up to the platform 10. Above the container 18, two by-pass conduits 29 communicate with the conduit 28, a valve 30 being arranged in each of the two by-pass conduits.

The free ends of the by-pass conduits 29 open into the surrounding water. Furthermore, in the lower region ofthe conduit 28 is provided a main valve and a controlvalve32. The latter is operated by a pressure controller33 which cooperates with a sensor 34. The control valve 32 is thus actuated in dependence on pressure existing in the top section of the container 18, to adjust the flow-through crosssection ofthe conduit 28 accordingly. Afurther control valve 35 is disposed at the upper end of the conduit 28 and forms a part of a control circuit in which is arranged a pressure controller36 and a sensor37.

The arrangement is first brought over the well 17 as shown by the position in Figure 1, with the valves 30 open and the main valve 31 closed. In order to obtain an operative state, the valves 30 are closed and the pilot valve 31 open. During the placement of the container 18 overthe leak, the container is filled with inert gas which eventually becomes expelled by the incoming mixture filling the container from bottom to top at a high pressure. Inside the container 18, the three-phase mixture of water, crude oil and natural gas are separated from each other because of different specific weight. The natural gas is directly removed upwards through the conduit 28.

The natural gas provides direct actuation, on entry into the container 18, of the automatically operating pressure controllers 33 and 36. Since the crude oil portion is restrained by the walls of the container 18, a layer of crude oil develops between the interfaces 26 and 27. It can be removed upwards by the conduit 22.

The retention period of the liquid mineral phase can be controlled such as to assure a good separation of same from water particles.

In the embodiment of Figure 2, the container 18 is disposed immediately underneath the platform 10 and is generally integral with same. The platform 10 floats again on its float elements 11 which are held by cables 13 in their position above the well 17.

On one side of the container 18 is disposed an upright metal sheet partition wall 38 whose shape will become apparent on review of Figure 3, which limits a settling zone before transfer into a shaft 39, the settling zone being separate from the remainder of the container but communicating with same. A pumping system 40 is shown only in a diagrammatic way and serves the purpose of removal of the crude oil through a first conduit 22 communicating with the shaft 39. In this embodiment, a collection bell 41 is disposed above the well 17, the bell being provided with float elements 42 disposed equidistantly about its periphery. To the float members are secured cables 43, in which are disposed tension springs 44. The cables 43 secure the collecting bell 41 to foundations 15.

The collection bell 41 has an upwardly tapering, funnel-like cross-section and merges into a riser45.

In the funnel-shaped portion of the collection bell 41 is provided an insert46 which is also of a funnelshaped configuration and operates in the fashion of a Venturi nozzle, so that even small oil droplets contained in water can be taken away. In this embodiment, the by-pass conduits 29 communicate with the riser 45. A main valve47 is disposed within the riser 45 above the merger with by-pass conduits 29.

The riser 45 reaches into the interior of the container 18, namely to a level which is disposed above the interface 27 designating the upper limit of the liquid phase. About the discharge end of the riser 45 is arranged a co-axial spiral-shaped flow channel 48 which extends to a level underneath the interface 27.

As shown in Figure 3, the liquid phases falling from top into the flow channel 48 are accelerated by the spiral shape of the flow channel 48 in radially outward direction so that a first separation between the two liquid phases due to the differences between their respective densities takes place already at this point. The cross-section of the flow channel 48 can, if desired, increase in radial direction, in order to extend over and to cover the surface of the already separated liquid phases. After the arrangement is placed in a location shown in Fig. 2, the valves 30 are closed and the main valve 47 of the riser 45 open.

The three-phase mixture can now enter into the container 18, in a gas space disposed above the interface 27, wherein the gaseous phase separates first and can be removed upwards through the conduit 28.

The embodiment shown in Fig. 4 differs from that of Figs. 2 and 3 only in that columns49 are provided, which extend from the platform 10 down to the sea bed 14 and are disposed on footings 50. The collecting bell 41 is joined with columns 49 by a radial link age51 with couplings 52 each of which is movably disposed on a respective column 51 and can be driven by a motor 53. The transmission of this drive can be effected by a rack-and-pinion drive or the like.

The container 18 is correspondingly connected with the columns 49 by a radial linkage, such that a drive can also be provided which contains drive couplings 52 and motors 53. Finally, on the platform 10 are also provided drive couplings 52 and motors 53 by which the columns 49 can be raised or lowered in vertical direction. After the columns 49 have been lowered down to the footings 50, the collecting bell 41 and the container 18 can be brought to the desired respective level.

It is further conceivable within the embodiments described herein to provide a container 18 which is closed at its bottom. This is of advantage when it is to be expected that the crude oil portion contained in water flowing back into the sea may be too great. In such case, the pumping system 40 for removal of crude oil can be provided with an additional seawater pumping system co-operating with a subsequent device for fine separation of crude oil.

It also falls within the scope of the present invention to provide, if required, the platform 10 and the container 18 as an integral part of a ship hull such that the arrangement according to the invention forms a part of a seagoing vessel. In such a modification, the arrangement can be simply and quickly placed over a leakage in a pipeline or the like.

Those skilled in the art will readily appreciate that many modifications of the described embodiments may exist, without departing from the scope of the present invention as set forth in the accompanying

Claims

claims. CLAIMS

1. A device for the recovery of fluid minerals discharging from subaqueous leaks, wells or the like with water, said device comprising, in combination: (a) a container for separating the minerals from water due to different specific weight thereof; (b) feed means communicating with said container for feeding into the container aqueous suspension of said fluid minerals; (c) first conduit means within a first horizontal zone of the container for removing from said container liquid fraction of said minerals, said first conduit means communicating with said container at an intermediate level thereof; (d) second conduit means for removal from said container of gaseous fraction of said minerals, said second conduit means communicating with said container at an upper level disposed above said intermediate level.

2. A device as claimed in Claim 1, wherein said intermediate level is disposed within the first horizontal zone of the container, said first horizontal zone having a top level and a bottom level, each generally coincident in the levels of interface between separated liquid and gaseous fractions and between water and the liquid fraction, respectively, said feed means including a riser whose upper discharge end is disposed above said top level.

3. A device as claimed in Claim 2, further comprising a collecting bell open at bottom and adapted to be placed over a source of discharge of the minerals, said collecting bell having an upper discharge end communicating with a lower end of said riser, said container being disposed at a vertical spacing above the discharge end of the bell.

4. A device as claimed in Claim 1, wherein the container is a bottomless container adapted to be placed over a source of discharge of the minerals, said container communicating with one end of a by-pass conduit, the other end of the by-pass conduit being adapted to communicate with water surrounding the container, said by-pass conduit comprising valve means for selective closing or opening of the by-pass conduit, to facilitate the positioning of the container over the source by flooding the interior thereof with water.

5. A device as claimed in Claim 3, wherein said bell communicates with one end of a by-pass con duit, the other end ofthe by-pass conduit being adapted to communicate with water surrounding the bell, said by-pass conduit comprising valve means for selective closing or opening of the by-pass conduit to facilitate the positioning of the bell over the source by flooding the interior thereof with water.

6. A device according to any of Claims 2, 3, or 5, wherein the bell has an upwardly tapering funnellike top section with an insert of the type of a Venturi-type nozzle disposed therein.

7. A device according to any of claims 2, 3, 5 or 6, wherein the riser is provided with a valve for selective opening or closing of the communication between the container and the bell.

8. A device according to any of the preceding claims, wherein the first conduit means includes first check valve means for closing or opening discharge of said liquid fraction from said container, said check valve means being operatively associated with a first control circuit for maintaining the level of the liquid fraction at a predetermined elevation.

9. A device according to any of the preceding claims, wherein said second conduit means is provided with second check valve means for closing or opening discharge of said gaseous fraction from said container, said second check valve means being operatively associated with a second control circuit governed by gas pressure within the container and being disposed at a section thereof coincident with a point of communication with said second conduit means.

10. A device according to any of the preceding claims further comprising a generally upright partition wall spanning said first horizontal zone and separating a relatively small settling zone adjacent to an inlet of said first conduit frorn the remainder of the interior of the container, said settling zone communicating with the remainder of the interior.

11. A device according to claims 3-10, further comprising generally horizontal breaker plates disposed in proximity of and below the discharge end of the risen

12. A device according to Claim 11, wherein said breaker plates form a portion of a spiral-shaped channel generally co-axial with the riser and arranged to direct the liquid discharged from the riser to an accelerating downward spiral flow.

13. A device according to any of the preceding claims, further comprising anchoring means for anchoring said container to sea bed in a resiliently yieldable fashion.

14. A device according to any of claims 3 and 5 through 13, further comprising anchoring means for anchoring said bell to sea bed in a resiliently yieldable fashion.

15. A device according to any ofthe preceding claims, further comprising float means operatively secured to said container.

16. A device according to any of claims 3 and 5 through 15, further comprising float means operatively secured to said bell.

17. A device according to any of the preceding claims further comprising a platform adapted to be disposed at the sea surface level; a plurality of generally vertical support columns extending downwardly from said platform and adapted to be anchored to sea bed; and securement means for securing said container to said columns for vertical movement along the same.

18. A device according to any of claims 3 and 5 through 16, further comprising a platform adapted to be disposed at the sea surface level; a plurality of generally vertical support columns extending downwardly from said platform and adapted to be anchored to sea bed; and securement means for securing said bell to said columns for vertical movement along the columns.

19. A device according to any of the preceding claims further comprising inert gas feed means for filling at least a portion of the interior of the container with an inert gas during the placement thereof into operative position.

20. A device according to any of the preceding claims wherein at least a portion of said first and second conduit means is formed by a generally self-supporting, resiliently deformable house.

21. A device for the recovery of fluid materials discharging frorn subaqueous leaks substantially as hereinbefore described with reference to and as illustrated in any of the accompanying drawings.