Note: Descriptions are shown in the official language in which they were submitted.
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A COLLECTION DEVICE AND METHOD OF USING SAME
The present invention relates to a collection device and a
method for using same. More particularly it concerns a col-
lection device for solids and fluid directed from a first lo-
cation on a seabed, on an offshore installation or onshore,
and to a second location, where the fluid directs the solids
material in through an inlet portion in a solids collection
device provided with one or more permeable portions arranged
to retain solids material exceeding a predetermined size.
lo When excavating or drilling in the ground or on a seabed or
onshore, masses, which must be removed from the excavating or
drilling area, are released. The released masses may in hand-
ling represent a drawback as they may spread to the surround-
ing environment.
When drilling a top hole section in a petroleum well on the
seabed, there is known from Norwegian Patent NO 320113, which
owner is the same as the applicant for the present invention,
a method and collection device for removal of water laden
drill cuttings being returned from the top section of a bore-
hole. The drill cuttings is pumped into a collection device,
which thereafter is lifted to the sea surface and onboard a
vessel. The collection device is provided with drainage prop-
erties such that fluid is drained from the collection device
when it is lifted onboard the vessel
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Even though the collection device and the method have proven
themselves to function satisfactorily, they have certain
drawbacks. One of these drawbacks is that during lifting of
the collection device from the seabed and up to the vessel,
fines present in the collection device together with the
drill cuttings, may be drained from the collection device
together with the liquid. The fines and the liquid being
drained out may represent a pollution problem. Another draw-
back relates to the capacity of the collection device. Due to
theLcollection device being lifted onboard a vessel, its size
is limited to typically 25 m3. The collection device must
thus relatively often be connected to and disconnected from
the pumping device and the lifting device bringing the col-
lection device up to the surface. Such handling at the seabed
is is usually carried out by means of a so-called ROV (Remote
Operated Vehicle), which is relatively costly in use. In ad-
dition it is costly to transport the drill cuttings to shore
for further processing and depositing.
At such as dredging of such as a seabed, there is sometimes
no need for, or there may be a requirement for the masses to
be removed from the seabed. It is however in the nature of
the case that the mass need to be moved from a first area and
to a second area on the seabed. It is known to carry out this
transfer of mass by pumping the mass away from the area
wherefrom the mass is being removed. An essential drawback
with this type of dredging operation is that large areas
downstream of the dredging operation are covered by the mass.
This mass may harm the seabed fauna. In some locations there
are therefore requirements that dredged mass or mass having
to be removed in other ways, to be pumped to shore for possi-
ble cleaning and depositing in special approved landfills.
This is a very costly operation.
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When depositing residual waste from the mining or process in-
dustry, it is known to place this in open disposal sites on
land or in the sea. In those cases where such residual waste
includes fines, it turns out to be problematic to avoid
spreading of the residual waste to surrounding areas. The
problem is particularly great during transfer of the mass.
From Norwegian Patent Application NO 20076546 appurtenant to
the present applicant, and which is wholly incorporated in
the present application, there is known a collection device
lo for solids material which by means of a fluid is transferred
from a first location on a seabed, on an offshore installa-
tion or onshore and to a second location, and where the fluid
directs the solids material in through an inlet portion to
the collection device, and where the collection device is
provided with one or more permeable portions provided to hold
back solids material exceeding a predetermined particle size.
The collection device according to N020076546 has shown it-
Self to function very satisfactorily regarding collecting of
solids material and solves to a great extent the problems
zo pointed out in prior art represented by said Norwegian Patent
NO 320113.
The applicant has however experienced that in some cases
there is a need or a desire to be able to clean at least a
portion of the fluid being used to direct the solids parti-
cles into the collection devices according to the above prior
art, before it is released to the surroundings. The need for
cleaning may for example be due to the fluid itself contain-
ing chemical additives or other components added to the fluid
as this directs the solids particles into the collection de-
vice and/or the need for cleaning may for example be due to
the fluid in itself having added components believed to be
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pollutive or that it is being polluted by matter being re-
leased to the fluid from the solids.
From the publication NO 173521 is known a subsea storage con-
struction for handling and storage of drill cuttings from
drilling operations in a seabed. The structure includes a
generally closed tank adapted to be placed on the seabed near
the drilling site. The tank is provided with an upper inlet
for supply of drill cuttings, and an outlet to the surround-
ing sea for water displaced during supply of drill cuttings.
lo The tank contains means for cleaning of the drill cuttings,
and for storage of accumulated separated oil, fluids and
other constituents separated out from the drill cuttings. The
structure further includes means for carrying off accumulated
oil, fluids and other constituents that are lighter than wa-
ter and that will gradually be released from the deposited
drill cuttings.
The object of the invention is to remedy or reduce at least
one of the prior art drawbacks.
The object is achieved by features stated in the below de-
scription an in the following Claims.
In a first aspect of the present invention, there is provided
a collection device for solids material and fluid directed
from a first location on a seabed, on an offshore installa-
tion or onshore, and to a second location, where the fluid
directs the solids material in through an inlet portion in a
solids collection device provided with one or more permeable
portions arranged to hold back solids material particles in
excess of a predetermined size, characterised in that the
collection device is further provided with a fluid collection
device provided to be able to collect at least a portion of
the fluid flowing out through the solids collection device,
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and that the fluid collection device is connected to a fluid
processing plant.
By offshore installation is in this document meant a fixed or
floating installation such as a rig or a floating vessel such
5 as a ship or a barge.
The fluid processing plant may, for example, but not limited
to, consist of one of or a combination of a fluid sampling
and analysis plant, a cleaning plant or a storage plant. By
sampling the fluid contained in the fluid collection device,
lo it may be decided if the fluid is clean enough to be returned
to the surroundings, which may be such as the sea, or if the
fluid must be directed to a cleaning plant to undergo clean-
ing before perhaps being returned to the surroundings. It may
be relevant, in cases where for example the fluid is polluted
to a particularly high degree, to lead the fluid into storage
containers, which in turn may be brought to suitable cleaning
plants.
The fluid processing plant, or at least a part of it, is in
one embodiment positioned adjacent to the collection device.
In one embodiment the whole or parts of the fluid processing
plant is positioned a distance apart from the collection de-
vice. The fluid, in the latter embodiment, is lead between
the collection device and the fluid processing plant by means
of a conduit.
The fluid collection device is in one embodiment made of an
elastic material so that the fluid collection device will be
able to undergo a volume change as fluid flows into it.
Advantageously, the fluid collection device is made from a
decomposable material.
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The fluid collection device is preferably made of a material
which is fluid tight, even if it for some uses may be accept-
able if some of the fluid may seep through the fluid collec-
tion device. Use of the fluid collection device in areas
where there is a desire or a requirement for so-called "zero
discharge", such as for the oil exploitation industry off-
shore in particularly vulnerable areas, a fluid tight collec-
tion device might be necessary.
The solids collection device may be any device suitable for
lo retaining solids being supplied, but is preferably of a sort
as shown in said Norwegian Patent Publication N0320113 and
preferably of the sort described in said Norwegian Patent Ap-
plication NO 20076546.
In a preferred embodiment, the solids collection device is a
container. The container is preferably closed, at least at
start, in the sense that it provides at least one compartment
arranged to be able to retain solids material above a prede-
termined size from the surroundings outside the container.
In one embodiment, the at least one permeable portion of the
solids collection device has an increasing degree of perme-
ability in a direction from the inlet portion and toward one
or more portions spaced from the inlet portion of the collec-
tion device.
The increasing degree of permeability is in one embodiment
provided by means of changing the size of openings in the
wall portion of the collection device. As an alternative or
in addition to said changed sizes, increasing the size of the
permeable wall portions may provide the increasing degree of
permeability.
In one embodiment, the at least one permeable portion of the
solids collection device is provided with openings having a
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first size, where at a distance from the inlet portion is
provided at least one outlet opening having an opening of a
second size, the first size being smaller than the second
size. In one embodiment, an open portion arranged to be able
to evacuate or flow substantially the same rate of fluid that
is being pumped into the solids collection device constitutes
the outlet opening. The fluid flowing out through the solids
collection device, through the outlet opening and/or the per-
meable portions, flows into the fluid collection device.
lo In one embodiment, at least one of the at least one permeable
portions is provided with openings 100 pm or less, preferably
50 pm or less.
The above mentioned increasing degree of permeability and/or
increase in outlet opening size(s), has the effect that the
fluid carrying the solids material in through the inlet por-
tion of the solids collection device, will encounter less and
less resistance to evacuation or flow out of the solids col-
lection device, the further away from the inlet portion the
fluid is. Thus, the fluid carrying the solids particles into
the solids collection device, may flow a furthest possible
distance inside the solids collection device before being
evacuated. Therefore, also substantially all of the fines may
settle out in the solids collection device before the fluid
flows out of it and into the fluid collection device.
Another important consequence of providing the above men-
tioned increasing degree of permeability and/or outlet
openings, is that the collection device might be placed
packed together, such as folded or rolled up at the location
where it shall receive the solids material. Such a rolling up
presupposes that the solids collection device is made from
such as a fabric like material or is designed such that it
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may be unfolded from a rolled up condition and to a fully
raised condition.
The fluid being directed into the above-mentioned solids col-
lection device made from such as a fabric like material will
initially flow out through the one or more permeable portions
being closest to the inlet portion. Some of the solids parti-
cles being retained by the permeable portion will gradually
clog the openings therein. Consequently the fluid will move
further away from the closest but now clogged portions. The
lo result is that the fluid causes an inflation or extension of
the collection device as fluid and solids particles are lead
in through the inlet portion.
In one embodiment the solids collection device is provided
with at least one internal flow restrictive device. The at
least one internal flow restrictive device contributes among
other things to reduce the flow rate inside the solids col-
lection device and contributes thereby to an increased degree
of settling out of the solids particles in the fluid. The at
least one flow restrictive device may also contribute to in-
crease the stability of shape and the mechanical strength of
the solids collection device.
In one embodiment at least portions of the material of the
solids collection device, which also the material of the
fluid collection container may be, are made of a biologically
decomposable material. This has the effect that the mass lead
into the solids collection device will after some time be
laid bare, and a natural fauna may develop on a seabed or on-
shore.
In a second aspect of the present invention a method is pro-
vided for collection of solids material and fluid being di-
rected from a first location on a seabed or onshore to a sec-
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ond location, the method including placing a collection de-
vice that includes a solids collection device and a fluid
collection device in said second location, where the solids
collection device is provided with one or more permeable par-
s tions arranged to retain solids material larger than a prede-
termined size, and where the fluid collection device is ar-
ranged to collect at least a fraction of the fluid flowing
out through the solids collection device, and where the fluid
collected in the fluid collection device is lead to a fluid
lo processing plant.
In the following an example of a preferred embodiment illus-
trated in the accompanying drawing is described.
Fig. 1 shows a dredging operation taking place on a seabed,
where the mud mass is pumped via a conduit from a dredging
15 machine and into a collection device, where the collection
device comprises a solids collection device enclosed by a
fluid collection device.
In the figure the reference number 1 indicates a collection
device according to the present invention where the collec-
20 tion device 1 is made up of a solids collection device 1' be-
ing enclosed by a fluid collection device 1". The fluid col-
lection device 1" encloses the whole of the solids
collection device 1'. It shall however be understood that the
fluid collection device 1" in alternative embodiments only
25 encloses portions of the solids collection device 1'. The
fluid collection device 1" need not for example, but may
readily, enclose possible closed portions of the solids col-
lection device or portions bearing against the ground.
A line 3 extends between an inlet portion 7 positioned on an
30 upper portion of the solids collection device 1', and a
dredging machine 5 known per se. The line 3 extends in the
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embodiment shown through the wall portion of the fluid col-
lection device 1" and down to the inlet portion 7.
The dredging machine 5 is provided with a suction line 5'
sucking mud mass and water, where the mud mass and the water
5 is pumped via the line 3 and into the solids collection de-
ice 1' of the collection device 1. A person skilled in the
art will recognise that one or more pumping units (not shown)
may be connected to the line 3.
The solids collection device 1' shown is of a sort shown in
lo said patent application NO 20076546 by the applicant, which
is fully incorporated in this document, and will therefore
not be discussed in any greater detail in this embodiment ex-
ample.
When the fluid from the dredging machine 5 is supplied to the
collection device 1, the water driving the mud mass may
evacuate or flow out through the permeable wall portions of
the solids collection device 1' and into the fluid collection
device 1".
In the embodiment shown the solids collection device 1' is in
an end portion distal or spaced from the inlet portion 7 pro-
vided with an outlet opening 11 as shown in an embodiment
where a portion of the wall of the solids collection device
1' is provided with a hole. In an alternative embodiment (not
shown) the outlet opening may be provided by one or more por-
tions having higher permeability than the whole or parts of
the rest of the solids collection device 1'.
A collection device 1 of the invention may, according to
needs, material strength and any statutory limitations such
as limitations in height for so-called overtrawlability, be
produced in very many different sizes. In seabed operations
tests have shown that a collection device 1 having a length
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of 30 - 50 m, and a width or diameter of 10 - 20 m has turned
out to be suitable.
As a person skilled in the art will recognise, the coarsest
material settles out under or close to the inlet portion 7 in
the solids collection device 1', while the material carried
inside the solids collection device 1', will become finer and
finer in the direction toward the outlet opening 11.
The fluid flowing out through the outlet opening 11 and/or
through the permeable wall portions of the solids collection
lo device 1', will flow into the surrounding fluid collection
device 1".
From an outlet 18 in the fluid collection device 1" a line
19, 20 extends up to a surface. The line 19, 20 is arranged
to be able to lead fluid to a not shown fluid processing
plant. The fluid processing plant may for example be one of
or a combination of a fluid sampling and analysis plant, a
cleaning plant, or a storage plant. One or more transport
containers may for example constitute the storage plant.
Samples of the fluid present in the fluid collection device
1" may thus, by means known per se be lead to the fluid
processing plant for analysis.
The fluid processing plant, or parts of it, may in an alter-
native embodiment (not shown) be located at the collection
device 1. In such an embodiment the results from the analysis
may in ways known per se be communicated to such as a control
room on an offshore installation, wherefrom further handling
of the fluid present in the fluid collection device 1", is
controlled.
If the analyses show that the fluid present in the fluid col-
lection device 1" is sufficiently clean to be drained out
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into the water outside the collection device 1, such drainage
is done through an outlet line 22 placed in connection with
the fluid collection device 1".
If the analyses of the samples show that the fluid is not
sufficiently clean to be drained out into the water, e.g. be-
cause the fluid contains too much fines, or that other condi-
tions requires that the fluid can not be drained out into the
water, the fluid may be re-circulated by means of a pumping
device 20' from the outlet portion 18 of the fluid collection
lo device 1" via line 19, 24 and 3 and back to the solids col-
lection device 1' so that a further portion of the fines may
be settled out in the solids collection device 1'.
It is to be understood that the fluid flow to the lines 19,
20, 22, 24 is controlled by valves known per se which are not
shown in the figure for clarity.
To increase the precipitation of fines, there may be added to
the fluid a binding agent or precipitation agent contributing
to particulate matter appearing dispersed in the liquid phase
to flocculate so that the particles are gathered to larger
and heavier particles thereby causing a quicker and more ef-
ficient separation and settling of the solids. The binding
agent is preferably an environmentally friendly chemical of a
sort known per se. Most preferably is the binding agent an
organic binding agent.
The binding agent is injected via a line 17 into the supply
line 3 upstream of the inlet opening 7. A person skilled in
the art will recognise that the binding agent may also be in-
jected in the line 24.
If the analyses of the samples show that the fluid is not
sufficiently clean to be drained out into the water, e.g. due
to a content of an unacceptable level of environmentally un-
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friendly matter, the fluid may be lead in the lines 19, 20 by
means of the pump 20' to a not shown cleaning plant located
for example on an offshore installation. After cleaning on an
offshore installation, the fluid may be returned to the sea.
It may also be considered that the fluid is lead from the
fluid collection device 1" to containers (not shown) wherein
the fluid is brought to a fluid processing plant onshore.
Samples of the fluid in the fluid collection device 1", may
for example be collected continuously or at predetermined
intervals.
When the solids collection device 1' is sufficiently filled,
the lines 3 and 19 are removed, for example by means of an
ROV, from the inlet portion 7 and the outlet portion 18 re-
spectively, and possibly be connected to a new collection de-
vice in the way this is described in said Norwegian Patent
Application N020076546.
In the figure is shown an embodiment of a solids collection
device 1' where two transverse walls 13, 13', are provided
internally in the collection device 1 and transverse of its
longitudinal direction between the inlet portion 7 and the
outlet opening 11. The transverse wall 13 which is nearest
the inlet portion 7, extends from the bottom portion of the
solids collection device 1' and about half way up toward the
top portion. The transverse wall 13' nearest the outlet open-
ing 11 covers the whole of the internal cross-section of the
= solids collection device 1'.
It shall be understood that any number of transverse walls
13, 13' may be installed internally in the solids collection
device 1', even if two are shown in Figure 1. It shall fur-
ther be understood that the transverse walls 13, 13' may be
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located in any desired angle relative to said longitudinal
direction.
The transverse walls 13, 13' have two objectives. Firstly,
the transverse walls 13, 13' will act as bracing elements re-
inforing the wall portions of the solids collection device
1'. Secondly the transverse walls 13, 13' may, depending on
their permeability, act as a flow restriction and thereby de-
fine chambers in the solids collection device 1'. The cham-
bers may simplify inflation of the collection device 1 and at
lo the same time cause a reduced fluid throughput rate. A re-
duced fluid throughput rate will result in further increased
retention time for the fluid in the solids collection device
1' and thereby settling of fines closer to the inlet opening
7 as compared to a collection device 1 without transverse
walls 13, 13'.
It is to be understood that the transverse walls 13, 13' may
cover all or only portions of a cross-sectional area of the
solids collection device 1'.
It is to be understood that the collection device 1 may be
connected to already existing systems (not shown) provided to
separate sand from well production, a so-called "Sub sea sand
separator".
The present invention thus provides a collection device 1 ar-
ranged both to filter solids particles from a fluid, at the
same time as the fluid is collected and before it is released
to the surrounding environment, possibly after a cleaning
process.
