Technical Field
[0001] The present disclosure relates to a separating device for the removal of solid particles
from a fluid.
Background
[0002] Such separating devices are required in many oil and gas extraction wells. Mineral
oil and natural gas are stored in naturally occurring underground reservoirs, the
oil or gas being distributed in more or less porous and permeable mineral layers.
The aim of every oil or gas drill hole is to reach the reservoir and exploit it in
such a way that, as far as possible, only saleable products such as oil and gas are
extracted, while undesired by-products are minimized or even avoided completely. The
undesired by-products in oil and gas extraction include solid particles such as sands
and other mineral particles that are entrained from the reservoir up to the borehole
by the liquid or gas flow.
[0003] Since the mineral sands are often abrasive, the influx of such solids into the production
tubing and pump cause considerable undesired abrasive and erosive wear on all of the
technical internals of the borehole. It is therefore endeavoured to free the production
flow of undesired sands directly after it leaves the reservoir, that is to say while
it is still in the borehole, by filter systems.
[0004] Problems of abrasion and erosion in the removal of solid particles from liquid and
gas flows are not confined to the oil and gas industry, but may also occur in the
extraction of water. Water may be extracted for the purpose of obtaining drinking
water or else for the obtainment of geothermal energy. The porous, often loosely layered
reservoirs of water have the tendency to introduce a considerable amount of abrasive
particles into the material that is extracted. In these applications too, there is
the need for abrasion- and erosion-resistant filters. Also in the extraction of ore
and many other minerals, there are problems of abrasion and erosion in the removal
of solid particles from liquid and gas flows.
[0005] In oil and gas extraction, the separation of undesired particles is usually achieved
today by using filters that are produced by spirally winding and welding steel forming
wires onto a perforated basepipe. Such filters are referred to as "wire wrap filters".
Another commonly used type of construction for filters in oil and gas extraction is
that of wrapping a perforated basepipe with metal screening meshes. These filters
are referred to as "metal mesh screens". Both methods provide filters with effective
screen apertures of 75 µm to 350 µm. Depending on the type of construction and the
planned intended use of both these types of filter, the filtering elements are additionally
protected from mechanical damage during transport and introduction into the borehole
by an externally fitted, coarse-mesh cage. The disadvantage of these types of filter
is that, under the effect of the abrasive particles flowing at high speed, metal structures
are subject to rapid abrasive wear, which quickly leads to destruction of the filigree
screen structures. Such high-speed abrasive flows often occur in oil and/or gas extraction
wells, which leads to considerable technical and financial maintenance expenditure
involved in changing the filters. There are even extraction wells which, for reasons
of these flows, cannot be controlled by the conventional filtering technique, and
therefore cannot be commercially exploited. Conventional metallic filters are subject
to abrasive and erosive wear, since steels, even if they are hardened, are softer
than the particles in the extraction wells, which sometimes contain quartz.
[0006] In order to counter the abrasive flows of sand with abrasion-resistant screen structures,
US 8,893,781 B2,
US 8,833,447 B2,
US 8,662,167 B2 and
WO 2016/018821 A1 propose filter structures in which the filter gaps, that is to say the functional
openings of the filter, are created by stacking specially formed densely sintered
annular discs of a brittle-hard material, preferably of a ceramic material. In this
case, spacers are arranged on the upper side of annular discs, distributed over the
circumference of the discs.
[0007] In the separating device of
WO 2016/018821 A1, a perforated pipe is located inside the stack of annular discs, onto which pipe
the brittle-hard annular discs are stacked. At the upper and lower end of the separating
device, there are end caps made of steel which are firmly connected to the perforated
pipe. Usually, separating devices such as disclosed in
WO 2016/018821 A1 consist of an arrangement of separate modules, each module comprising a stack of
brittle-hard annular discs. The modules are connected via intermediate elements made
of steel. The intermediate elements are firmly connected with the perforated pipe.
The intermediate elements are housing a compensator system which is usually made from
steel, e.g. provided as springs, and which is required to compensate the thermal mismatch
of perforated pipe and the stack of annular discs. Under operating conditions, the
intermediate parts and also the compensator system are exposed to erosive and corrosive
environment which is a risk for damage. The intermediate element and also the compensator
system made from steel may erode and may get damaged to an extent where it loses its
function, resulting in loss of sand control, and production has to be stopped.
[0008] Therefore, there is still a need to provide an improved separating device for the
removal of solid particles from fluids, in particular from oil, gas and water. Particularly,
there is a need to provide a separating device having an improved erosion and corrosion
resistance.
[0009] As used herein, "a", "an", "the", "at least one" and "one or more" are used interchangeably.
The term "comprise" shall include also the terms "consist essentially of" and "consists
of".
Summary
[0010] In a first aspect, the present disclosure relates to a separating device for removing
solid particles from fluids, comprising
a stack of at least three annular discs defining a central annular region along a
central axis, each annular disc having an upper side and an underside, wherein the
upper side of each annular disc each has two or more spacers, and wherein the spacers
of the upper side of each annular disc contact the underside of the adjacent annular
disc, and wherein the annular discs are stacked in such a way that a separating gap
for the removal of solid particles is present in each case between adjacent annular
discs, and wherein the central annular region comprises a first section and a second
section,
a supporting structure for axial bracing of the central annular region, wherein the
supporting structure is located inside the central annular region,
a tubular shroud for protection of the central annular region from mechanical damage,
and
an intermediate element which is placed between the first section and the second section
of the central annular region, wherein the intermediate element supports the shroud,
and wherein each annular disc comprises a material independently selected from the
group consisting of (i) ceramic materials; (ii) mixed materials having fractions of
ceramic or metallic hard materials and a metallic binding phase; and (iii) powder
metallurgical materials with hard material phases formed in-situ,
and wherein the intermediate element comprises a material selected from the group
consisting of (i) ceramic materials; (ii) mixed materials having fractions of ceramic
or metallic hard materials and a metallic binding phase; and (iii) powder metallurgical
materials with hard material phases formed in-situ.
[0011] In another aspect, the present disclosure also relates to a separating device for
removing solid particles from fluids, comprising
a stack of at least three annular discs defining a central annular region along a
central axis, each annular disc having an upper side and an underside, wherein the
upper side and the underside of every second annular disc in the stack each has two
or more spacers, and wherein the upper side and the underside of the respectively
adjacent annular discs do not comprise any spacers, and wherein the spacers of the
upper side of every second annular disc in the stack contact the underside of the
adjacent annular disc, and wherein the spacers of the underside of every second annular
disc in the stack contact the upper side of the adjacent annular disc, and wherein
the annular discs are stacked in such a way that a separating gap for the removal
of solid particles is present in each case between adjacent annular discs, and wherein
the central annular region comprises a first section and a second section,
a supporting structure for axial bracing of the central annular region, wherein the
supporting structure is located inside the central annular region,
a tubular shroud for protection of the central annular region from mechanical damage,
and
an intermediate element which is placed between the first section and the second section
of the central annular region, wherein the intermediate element supports the shroud,
and wherein each annular disc comprises a material independently selected from the
group consisting of (i) ceramic materials; (ii) mixed materials having fractions of
ceramic or metallic hard materials and a metallic binding phase; and (iii) powder
metallurgical materials with hard material phases formed in-situ,
and wherein the intermediate element comprises a material selected from the group
consisting of (i) ceramic materials; (ii) mixed materials having fractions of ceramic
or metallic hard materials and a metallic binding phase; and (iii) powder metallurgical
materials with hard material phases formed in-situ.
[0012] In yet a further aspect, the present disclosure relates to the use of a separating
device as disclosed herein for removing solid particles from fluids
in a process for extracting fluids from extraction wells, or
in water or in storage installations for fluids, or
in a process for extracting ores and minerals.
[0013] The separating device as disclosed herein has an improved erosion resistance. The
separating device as disclosed herein also has an improved corrosion resistance to
the media to be extracted and the media used for maintenance such as acids. More specifically,
the intermediate element of the separating device as disclosed herein has an improved
erosion resistance and an improved corrosion resistance to the media to be extracted
and the media used for maintenance such as acids.
[0014] The intermediate element of the separating device as disclosed herein is shorter
than the intermediate element of the prior art. Depending on the diameter of the stack
of annular discs, the length of the intermediate element is only from 25 to 50% of
the length of an intermediate element of the prior art. Therefore, the filter area
can be increased by adding more annular discs on the same length of a perforated pipe.
[0015] The separating device as disclosed herein can be used for harsh environments, that
is for reservoirs to be exploited with streaks having high inflow and high erosional
impact.
[0016] The intermediate element of the separating device as disclosed herein does not house
a compensator system for compensating the thermal mismatch of perforated pipe and
central annular region.
Brief description of the drawings
[0017] The present disclosure is explained in more detail on the basis of the drawings,
in which
Figure 1A schematically shows the overall view of a separating device as disclosed
herein;
Figure 1B shows a cross-sectional view of a separating device as disclosed herein;
Figures 1C and 1D show details of the cross-sectional view of Figure 1B;
Figures 2A - 2E show various details of the intermediate element of a separating device
as disclosed herein;
Figures 3A - 3L show various details of the stack of annular discs of a separating
device as disclosed herein; and
Figures 4A - 4L show various details of the stack of annular discs of a separating
device as disclosed herein.
Detailed Description
[0018] Preferred embodiments and details of the separating device of the present disclosure
are explained in more detail below with reference to the drawings.
[0019] Figure 1A shows the overall view of a separating device according to the present
disclosure. Figure 1B shows a cross-sectional view of a separating device according
to the present disclosure. The separating device according to the present disclosure
comprises a stack of at least three annular discs defining a central annular region
1, 13 along a central axis. The separating device comprises a supporting structure
for axial bracing of the central annular region. The supporting structure is located
inside the central annular region 1, 13. The supporting structure may comprise a perforated
pipe 7, on which the annular discs are stacked. The perforated pipe 7 with perforations
23 is located inside the stack 1, 13 of annular discs and is also referred to hereinafter
as the base pipe. In other embodiments which are not shown in the drawings, the supporting
structure of the separating device comprises one or more rods arranged within the
central annular region. Usually provided at both ends of the perforated pipe 7 are
threads 24, by way of which the separating device can be connected to further components,
either to further separating devices or to further components of the extraction equipment.
For connection to further components, a coupling 30 with inner threads on both sides
may be screwed onto the thread 24.
[0020] If the supporting structure of the separating device comprises a perforated pipe,
the supporting structure further comprises an end cap 8 at the upper end of the central
annular region and an end cap 9 at the lower end of the central annular region 1,
13, the end caps being firmly connected to the base pipe 7.
[0021] The separating device further comprises a tubular shroud 22 (see Figure 1A) for protection
of the central annular region 1, 13 from mechanical damage. The shroud 22 can be freely
passed through by a flow. The shroud 22 protects the central annular region from mechanical
damage during handling and fitting into the borehole.
[0022] For better understanding, and since the separating device according to the present
disclosure is generally introduced into an extraction borehole in vertical alignment,
the terms "upper" and "lower" are used here, but the separating device may also be
positioned in horizontal orientation in the extraction borehole (in which case, upper
typically would refer to the most upstream portion and lower would refer to the most
downstream portion of the separating device, when in service).
[0023] The separating device according to the present disclosure comprises a stack of at
least three annular discs defining a central annular region 1, 13 (see Figures 1B,
3H, 4H) along a central axis. The annular discs 2, 14, 15 (see Figures 3A - 3F and
4A - 4J) have an upper side 3, 16, 18 and an underside 4, 17, 19 (see Figures 3B,
4B, 4I - 4J).
[0024] In some embodiments, the upper side 3 of each annular disc 2 of the central annular
region 1 each has two or more spacers 5 (see Figure 3A), and the underside 4 of each
annular disc does not comprise any spacers (see Figure 3B). The spacers 5 of the upper
side 3 of each annular disc 2 contact the underside 4 of the adjacent annular disc.
The annular discs 2 are stacked in such a way that a separating gap 6 for the removal
of solid particles is present in each case between adjacent annular discs (see Figures
3H - 3J).
[0025] The contact area 25 of the spacers 5 may be planar, so that the spacers 5 have a
planar contact area with the adjacent annular disc (see Figures 3C and 3E). The planar
contact area 25 is in contact with the adjacent underside 4 of the adjacent annular
disc.
[0026] The upper side 3 of each annular disc 2 may have only two spacers 5. Typically, the
upper side 3 of each annular disc 2 has three or more spacers 5 which are distributed
over the circumference of the upper side 3 of the annular discs 2.
[0027] The underside 4 of each annular disc 2 may be formed at right angles to the central
axis.
[0028] Each annular disc 2 comprises a material independently selected from the group consisting
of (i) ceramic materials; (ii) mixed materials having fractions of ceramic or metallic
hard materials and a metallic binding phase; and (iii) powder metallurgical materials
with hard material phases formed in-situ.
[0029] In some further embodiments, the upper side 16 and the underside 17 of every second
annular disc 14 of the central annular region 13 each has two or more spacers 5 (see
Figures 4A - 4F). The upper side 18 and the underside 19 of the respectively adjacent
annular discs 15 do not comprise any spacers (see Figures 4H - 4J). The spacers 5
of the upper side 16 of every second annular disc 14 in the stack contact the underside
19 of the adjacent annular disc 15, and the spacers 5 of the underside 17 of every
second annular disc 14 in the stack contact the upper side 18 of the adjacent annular
disc 15. The annular discs are stacked in such a way that a separating gap 6 for the
removal of solid particles is present in each case between adjacent annular discs
(see Figures 4H - 4J).
[0030] The upper side 16 and the underside 17 of each annular disc 14 each may have only
two spacers 5. Typically, the upper side 16 and the underside 17 of each annular disc
14 each has three or more spacers 5 which are distributed over the circumference of
the upper side 16 and the underside 17 of the annular discs 14.
[0031] The contact area 25 of the spacers 5 may be planar, so that the spacers 5 have a
planar contact area with the adjacent annular disc (see Figures 4C, 4E). The planar
contact area 25 of the spacers 5 of the upper side 16 of an annular disc 14 is in
contact with the underside 19 of the adjacent annular disc 15, and the planar contact
area 25 of the spacers 5 of the underside 17 of an annular disc 14 is in contact with
the upper side 18 of the adjacent annular disc 15.
[0032] Every upper side 18 of an annular disc 15 which does not comprise any spacers may
be formed at right angles to the central axis, and every underside 19 of an annular
disc 15 which does not comprise any spacers may be formed at right angles to the central
axis.
[0033] Each annular disc 14, 15 comprises a material independently selected from the group
consisting of (i) ceramic materials; (ii) mixed materials having fractions of ceramic
or metallic hard materials and a metallic binding phase; and (iii) powder metallurgical
materials with hard material phases formed in-situ.
[0034] The separating device as disclosed herein may comprise a supporting structure comprising
a perforated pipe 7 located in the central annular region 1, 13 (see Figures 1A -
1C) and two end caps 8, 9 (see Figures 1A and 1B) at the upper and lower ends of the
central annular region 1, 13.
[0035] The perforated pipe or base pipe is co-centric with the central annular region. The
base pipe is perforated, i.e. provided with holes, in the region of the central annular
region; it is not perforated outside the region of the central annular region. The
perforation 23 serves the purpose of directing the filtered fluid, i.e. the fluid
flow freed of the solid particles, such as for example gas, oil or mixtures thereof,
into the interior of the base pipe, from where it can be transported or pumped away.
[0036] Threads 24 are usually cut at both ends of the base pipe 7 and can be used for screwing
the base pipes together into long strings, for example with a coupling 30.
[0037] The base pipe can consist of a metallic material, a polymer or ceramic material.
The base pipe may consist of a metallic material such as steel, for example steel
L80. Steel L80 refers to steel that has a yield strength of 80 000 psi (corresponding
to about 550 MPa). As an alternative to steel L80, steels that are referred to in
the oil and gas industry as J55, N80, C90, T95, P110 and L80Cr13 (see
Drilling Data Handbook, 8th Edition, IFP Publications, Editions Technip, Paris, France) may also be used. Other steels, in particular corrosion-resistant alloy and high-alloy
steels, may also be used as the material for the base pipe. For special applications
in corrosive conditions, base pipes of nickel-based alloys or Duplex stainless steels
may also be used. It is also possible to use aluminum materials as the material for
the base pipe, in order to save weight. Furthermore, base pipes of titanium or titanium
alloys may also be used.
[0038] The inside diameter of the annular discs must be greater than the outside diameter
of the base pipe. This is necessary on account of the differences with regard to the
thermal expansion between the metallic base pipe and the material from which the annular
discs are made and also for technical reasons relating to flow. It has been found
to be favorable in this respect that the inside diameter of the annular discs is at
least 0.5 mm and at most 10 mm greater than the outside diameter of the base pipe.
In particular embodiments, the inside diameter of the annular discs is at least 1.5
mm and at most 5 mm greater than the outside diameter of the base pipe.
[0039] The outside diameter of the base pipe is typically from 2.54 cm to 25.4 cm (1 inch
to 10 inches).
[0040] The end caps are produced from metal, usually steel and typically from the same material
as the base pipe. The end caps 8, 9 may be firmly connected to the base pipe 7. The
end caps may be fastened to the base pipe by means of welding, clamping, riveting
or screwing. During assembly, the end caps are pushed onto the base pipe after the
central annular region and are subsequently fastened on the base pipe. In the embodiment
of the separating device as disclosed herein that is shown in Figures 1A - 1D, the
end caps are fastened by means of welding.
[0041] The central annular region 1, 13 of the separating device as disclosed herein comprises
a first section 11 and a second section 12.
[0042] The separating device as disclosed herein further comprises an intermediate element
10 which is placed between the first section 11 and the second section 12 of the central
annular region 1, 13. For embodiments of the separating device with the supporting
structure comprising a perforated pipe, the intermediate element 10 is co-centric
with the perforated pipe 7. The intermediate element 10 supports the shroud 22.
[0043] Of course, as described herein, "co-centric", "planar", "plane-parallel" and "at
right angles" (and similar terms) mean substantially so, within, for instance, relevant
manufacturing, assembly and/or operational tolerances.
[0044] The upper side of the intermediate element 10 in axial direction contacts the underside
of the last annular disc at the lower end of the first section 11 of the central annular
region 1, 13. The underside of the intermediate element 10 in axial direction contacts
the upper side of the first annular disc at the upper end of the second section 12
of the central annular region 1, 13.
[0045] The intermediate element 10 comprises a material selected from the group consisting
of (i) ceramic materials; (ii) mixed materials having fractions of ceramic or metallic
hard materials and a metallic binding phase; and (iii) powder metallurgical materials
with hard material phases formed in-situ. In some embodiments, the intermediate element
10 is made from a material selected from the group consisting of (i) ceramic materials;
(ii) mixed materials having fractions of ceramic or metallic hard materials and a
metallic binding phase; and (iii) powder metallurgical materials with hard material
phases formed in-situ.
[0046] These materials are erosion resistant to abrasive fluid flows and also corrosion
resistant to the media to be extracted and the media used for maintenance such as
acids.
[0047] The outer diameter of the intermediate element 10 is larger than the outer diameter
of the central annular region 1, 13. The outer diameter of the intermediate element
10 is larger than the outer diameter of the first section 11 and of the second section
12 of the central annular region 1, 13. The intermediate element 10 being supported
by the shroud 22 and having an outer diameter being larger than the outer diameter
of the central annular region ensures that there is a distance between the shroud
22 and the central annular region 1, 13 during deployment of the separating device,
and also in case of bending if the separating device needs to be introduced in curved
boreholes.
[0048] In some embodiments of the separating device as disclosed herein, the intermediate
element 10 comprises an intermediate core element 26 and a protective bush 20 which
is co-centric with the intermediate core element 26.
[0049] The intermediate core element 26 comprises a material selected from the group consisting
of (i) ceramic materials; (ii) mixed materials having fractions of ceramic or metallic
hard materials and a metallic binding phase; and (iii) powder metallurgical materials
with hard material phases formed in-situ. In some embodiments, the intermediate core
element 26 is made from a material selected from the group consisting of (i) ceramic
materials; (ii) mixed materials having fractions of ceramic or metallic hard materials
and a metallic binding phase; and (iii) powder metallurgical materials with hard material
phases formed in-situ.
[0050] The protective bush 20 protects the intermediate core element 26 from mechanical
damage. Mechanical damage of the intermediate element may occur during installation
of the separating device in the borehole.
[0051] The protective bush 20 may comprise a metallic material or a polymeric material.
The protective bush 20 may be made from a metallic material or from a polymeric material.
The metallic material of the protective bush may be steel. The polymeric material
of the protective bush may be, for example, polytetrafluoroethylene (PTFE) or a polyaramide
such as poly(p-phenylene terephthalamide) (PPTA; trade names: Kevlar, Twaron).
[0052] The protective bush 20 is located outside of the intermediate core element 26 (see
Figures 1C, 2E, 2F).
[0053] If the protective bush 20 is eroded by the abrasive fluid flows under operating conditions
of the separating device, the intermediate core element 26 of the intermediate element
10 ensures that the intermediate element 10 remains erosion and corrosion resistant
during the whole service life of the separating device.
[0054] In some embodiments of the separating device as disclosed herein, the protective
bush 20 is firmly connected to the intermediate core element 26. For example, if the
protective bush is made from a metallic material, the protective bush 20 may be shrunk
onto the intermediate core element 26. In some other embodiments, the protective bush
20 may also be only pushed on the intermediate core element 26 and may be not firmly
connected to the intermediate core element 26.
[0055] The outer diameter of the protective bush 20 is larger than the outer diameter of
the central annular region 1, 13. The outer diameter of the protective bush 20 is
smaller than the inner diameter of the shroud 22 at the position of the intermediate
element 10. The inner diameter of the protective bush 20 may be larger or smaller
than or equal to the outer diameter of the first and second section 11, 12 of the
central annular region 1, 13. Preferably, the inner diameter of the protective bush
20 is equal to or larger than the diameter of the circle circumscribed around the
planar contact areas 25 of the spacers 5 of the annular discs 2, 14, so that the complete
planar contact areas 25 of the spacers 5 have planar contact with the intermediate
core element 26. The inner diameter of the protective bush 20 may also be smaller,
in this case an annular disc having a rectangular cross-sectional area and no spacers
is placed next to the upper and lower end of the intermediate element 10. The area
of the upper side and underside of this annular disc having a rectangular cross-sectional
area and no spacers may be at least as large as the sum of the planar contact areas
25 of all spacers 5 of the adjacent annular disc 2, 14.
[0056] The outer lateral surface of the protective bush 20 may be cylindrical. It is also
possible that the cross-sectional area of the protective bush in axial direction is
T-shaped and the outer lateral surface of the protective bush 20 has a recess at the
upper axial end and a recess at the lower axial end of the protective bush. These
recesses accommodate the shroud 22 for the first and second section 11, 12 of the
central annular region 1, 13. In this case, the outer diameter of the protective bush
is the largest outer diameter of the protective bush at the central position.
[0057] Figure 1C shows a detail of Figure 1B at the position of the intermediate element
10. The intermediate element 10 is placed between the first section 11 and the second
section 12 of the central annular region 1, 13. The intermediate element 10 is co-centric
with the perforated pipe 7. The outer diameter of the intermediate element 10 is larger
than the outer diameter of the central annular region 1, 13. The outer diameter of
the intermediate element 10 is larger than the outer diameter of the first section
11 and of the second section 12 of the central annular region 1, 13. The intermediate
element 10 may comprise an intermediate core element 26 and a protective bush 20.
The protective bush 20 is co-centric with the intermediate core element 26. The protective
bush 20 is located outside of the intermediate core element 26. The protective bush
20 protects the intermediate core element 26 from mechanical damage. The intermediate
core element 26 is made from a material selected from the group consisting of (i)
ceramic materials; (ii) mixed materials having fractions of ceramic or metallic hard
materials and a metallic binding phase; and (iii) powder metallurgical materials with
hard material phases formed in-situ. The protective bush may be made from steel. The
protective bush may also be made from other metallic materials or from a polymeric
material. The protective bush 20 may be shrunk onto the intermediate core element
26. The outer diameter of the protective bush 20 is larger than the outer diameter
of the central annular region 1, 13. The outer diameter of the protective bush 20
is larger than the outer diameter of the first section 11 and of the second section
12 of the central annular region 1, 13. The outer diameter of the protective bush
20 is smaller than the inner diameter of the shroud 22 at the position of the intermediate
element 10. The inner diameter of the protective bush 20 may be smaller than the outer
diameter of the first and second section 11, 12 of the central annular region 1, 13.
The inner diameter of the protective bush 20 may be equal to the diameter of the circle
circumscribed around the planar contact areas 25 of the spacers 5 of the annular discs
2, 14. The intermediate element 10 supports the shroud 22.
[0058] Figure 1D shows a detail of Figure 1B at the position of the end cap 8 at the upper
end of the separating device. At the upper end of the central annular region 1, 13
and of the first section 11 of the central annular region 1,13, an end element 32
may be provided which forms the end-side, lateral termination of the central annular
region. The end element 32 is an annular element which is co-centric with the perforated
pipe 7. The end element 32 may be produced from the same material as the annular discs
2, 14, 15. Alternatively, however, corrosion-resistant steels and polymers, such as
for example fluoroelastomers or polyether ether ketone (PEEK), may also be used. At
the upper end of the central annular region 1, 13 and of the first section 11 of the
central annular region 1, 13, a sealing bush 33 may be provided. The sealing bush
has the task of preventing the ingress of fluids that are under pressure, into structural
cavities, such as for example bevels and gaps, between the end cap and the base pipe.
Otherwise, the fluid under pressure could exert a strong axial force on the central
annular region over the hydraulically effective annular surface of the uppermost annular
disc, which would lead to rupturing of the annular discs. An O-ring 34 is incorporated
in the sealing bush 33 on its outer circumferential surface. An O-ring may likewise
be incorporated on the inner circumferential surface of the sealing bush. The sealing
bush with the O-ring seals has the effect of preventing that fluids under pressure
can get into regions of the separating device that have nothing to do with the filtering
function. A wear and corrosion resistant material, for example a metallic or ceramic
material or else a hard material, is used as the material for the sealing bush. Steel
may be used as material for the sealing bush.
[0059] The region of the lower end of the separating device is usually symmetrical to the
region of the upper end of the separating device. At the lower end of the separating
device, also an end element 32 and a sealing bush 33 may be provided.
[0060] In Figures 1B, 1C and 1D, only a few annular discs of the central annular region
1, 13 are shown for ease of drawing. In reality, of course, the stack of annular discs
of the first section 11 of the central annular region 1, 13 is extending from the
upper end of the separating device, i.e. from the end element 32 at the upper end
of the separating device, to the intermediate element 10, and the stack of annular
discs of the second section 12 of the central annular region 1, 13 is extending from
the intermediate element 10 to the lower end of the separating device, i.e. to the
end element 32 at the lower end of the separating device.
[0061] The separating device as disclosed herein may further comprise one or more bands
29 which are provided on the lateral surface of the perforated pipe 7 and which are
inside the central annular region 1, 13 and inside the intermediate element 10 (see
Figures 2E, 2F). The annular discs are placed around the one or more bands, whereby
the annular discs are centered by the one or more bands on the perforated pipe. Also
the intermediate element 10 is placed around the one or more bands 29 and is centered
by the one or more bands. The one or more bands are also referred to as centering
bands.
[0062] The one or more bands or centering bands 29 may be provided axially parallelly on
the lateral surface of the perforated pipe. The centering bands may also be provided
helically in axial direction on the lateral surface of the perforated pipe. The centering
bands may be provided uniformly spaced apart or with different distances from one
another.
[0063] The length of the centering bands 29 corresponds at least to the length of the annular
stack, which ensures that all of the annular discs of the annular stack including
the first and last annular disc are centered.
[0064] The centering bands 29 may have elastic properties in a direction perpendicular to
the central axis of the central annular region. Due to the elastic properties, the
centering bands are elastically deformable in radial direction. In some embodiments,
the centering bands may have a hollow compressible structure. In some embodiments,
the centering bands may have a fibrous compressible structure. In some embodiments,
the centering bands may have a compact compressible structure. In some embodiments,
the centering bands may have a compressible profiled structure.
[0065] The centering bands 29 may have a planar configuration. The centering bands may also
have a profiled configuration in axial direction of the bands.
[0066] If the centering bands 29 have a profiled configuration, the profiled configuration
may be a curvature having an outwardly curved side. The outwardly curved side of the
curvature may be oriented towards the perforated pipe, i.e. inwards, or towards the
central annular region, i.e. outwards. Preferably, the outwardly curved side of the
curvature is oriented towards the central annular region, i.e. outwards.
[0067] The material of the centering bands should preferably be chosen such that it does
not corrode under operating conditions and it must be oil- water- and temperature-resistant.
Metal or plastic is suitable as the material for the centering bands, preferably metal
alloys on the basis of iron, nickel and cobalt, more preferably steel, more preferably
spring strip steel. For example, spring strip steel with the material number 1.4310,
of a spring-hard configuration, may be used as the material for the centering bands.
The width of the centering bands may be for example 2 to 30 mm and the thickness may
be for example 0.1 to 0.5 mm.
[0068] If steel is used as the material for the centering bands, it must be ensured when
selecting the material that undesired electrochemical reactions do not occur on contact
with other metallic structural elements of the separating device.
[0069] In some embodiments, the centering bands are fixed on the outer surface of the perforated
pipe. The centering bands may be fixed onto the outer surface of the perforated pipe
by welding, brazing or gluing.
[0070] In some embodiments, the centering bands are not permanently fixed on the outer surface
of the perforated pipe.
[0071] The thickness and width of the centering bands should be chosen such that the annular
discs can be axially displaced on the base pipe with a "sliding fit". This means that,
in the vertical position, the annular discs are not axially displaced under their
own weight. This is generally the case if the force for displacing the annular discs
on the base pipe in the horizontal direction, that is to say without the influence
of gravitational force, lies between 0.1 N and 10 N, preferably between 0.5 N and
5 N.
[0072] Preferably, the intermediate element 10 is movable in axial direction. Also the annular
discs of the central annular region are movable in axial direction. The intermediate
element needs to be freely movable in axial direction and may not be firmly connected
to the perforated pipe or the supporting structure. The free movability of the intermediate
element and the central annular region is required for compensating the differences
in thermal expansion of the central annular region and the intermediate element on
the one hand and of the perforated pipe or the supporting structure on the other hand.
The intermediate element 10 is able to absorb mechanical shock loads in axial direction
due to its free movability in axial direction. If more than one intermediate element
is present in the separating device, the intermediate elements need to be movable
in axial direction.
[0073] The intermediate element 10 may further comprise an annular element 27 which is co-centric
with the intermediate core element 26 and which is located inside the intermediate
core element 26. The annular element 27 protects the intermediate core element 26
from mechanical damage by radial load.
[0074] The annular element 27 may be firmly connected to the intermediate core element 26.
The outer diameter of the annular element 27 corresponds to the inner diameter of
the intermediate core element 26. For embodiments of the separating device disclosed
herein having a perforated pipe, between the annular element 27 and the base pipe
7 there is a gap which is large enough to ensure the free movability of the annular
element 27, and therefore the free movability of the intermediate element 10, in axial
direction.
[0075] The annular element 27 may be provided with one or more recesses 28 in axial direction
distributed along the circumference of the annular element 27. The recesses 28 are
on the inner circumference of the annular element 27. The number of recesses 28 may
correspond to or may be larger than the number of bands 29 which are provided on the
lateral surface of the perforated pipe 7, and each of the bands 29 is placed in one
of the recesses 28 of the annular element 27. The annular element 27 may also be provided
with no recesses and around the bands 29.
[0076] The radial thickness of the annular element 27 at the position of the recesses 28
is smaller than the radial thickness of the annular element 27 outside of the recesses
28.
[0077] For annular elements 27 with no recesses on the inner circumference, the inner diameter
of the annular element 27 for embodiments with bands 29 corresponds to the diameter
of the circumscribed circle around the bands 29. For annular elements 27 with recesses
28, the inner diameter of the annular element 27 for embodiments with bands 29 corresponds
to the diameter of the circumscribed circle around the bands 29, at the positions
of the recesses 28.
[0078] The recesses 28 may be provided axially parallelly to the central axis of the separating
device, or may be provided axially not parallelly to the central axis of the separating
device. The recesses may extend from the lower end of the annular element the upper
end of the annular element. The annular element 27 may also have openings 31. The
openings 31 do not extend from the lower to the upper end of the annular element.
The openings are cut through the complete radial thickness of the annular element
(see Fig. 2D). The openings do not have a specific form, they may be quadratic, rectangular,
circular or have any other form. Preferably, the openings are in the region of the
recesses 28.
[0079] The recesses 28 which are provided in axial direction distributed along the circumference
of the annular element 27 may be formed in such a way that their depth corresponds
to the radial thickness of the annular element 27, thereby dividing the annular element
27 in different segments. The number of segments may correspond to the number of recesses
28. It is also possible that one or more of the recesses 28 of the annular element
27 have a depth corresponding to the radial thickness of the annular element 27 and
dividing the annular element in one or more segments, and one or more further recesses
28 have a depth which is smaller than the radial thickness of the annular element
27. For example, an annular element having one recess with a depth corresponding to
the radial thickness of the annular element and further recesses with a depth which
is smaller than the radial thickness of the annular element, may be easily pushed
around the base pipe during assembly of the separating device.
[0080] In some embodiments of the separating device disclosed herein, the supporting structure
for axial bracing of the central annular region 1, 13 comprises a perforated pipe
7 which is co-centric with and located inside the central annular region 1, and an
end cap 8 at the upper end and an end cap 9 at the lower end of the central annular
region 1, the end cap 8, 9 being co-centric with the perforated pipe 7 and being firmly
connected to the perforated pipe 7. The intermediate element 10 is co-centric with
the perforated pipe 7. The separating device further comprises one or more bands which
are provided on the lateral surface of the perforated pipe 7 and which are inside
the central annular region 1, 13 and inside the intermediate element 10, the annular
discs being centered by the one or more bands 29 on the perforated pipe 7. The intermediate
element 10 may further comprise an annular element 27 which is co-centric with the
intermediate core element 26 and which is located inside the intermediate core element
26 and between the intermediate core element 26 and the perforated pipe 7. The annular
element 27 may be provided with one or more recesses 28 in axial direction distributed
along the circumference of the annular element 27. The number of recesses 28 is equal
to or larger than the number of bands 29 which are provided on the lateral surface
of the perforated pipe 7, and each of the bands 29 is placed in one of the recesses
28 of the annular element 27.
[0081] The material from which the annular element 27 is made should be resistant to compression
and suitable for load transfer from the intermediate core element 26 to the perforated
pipe 7 or to the supporting structure. The material from which the annular element
27 is made should further have a good chemical resistance to the treatment fluids
usually used for flushing out the separating device and stimulating the borehole,
such as acids, for example HCI or bases, for example NaOH. Furthermore, the material
of the annular element 27 should be temperature-resistant in the temperature range
of the application.
[0082] The annular element 27 may comprise a polymer, preferably polytetrafluoroethylene
(PTFE). In some embodiments, the annular element 27 consists of a polymer, preferably
polytetrafluoroethylene (PTFE). PTFE is highly resistant to compression, has an excellent
chemical resistance and good temperature-resistance, and can easily be machined.
[0083] The annular element 27 protects the intermediate core element 26 from mechanical
damage by radial loads. Radial loads may arise from side impact, or from bending which
occurs when the separating device is introduced in curved boreholes. The annular element
27 improves the resistance of the intermediate part against radial loads. The run-in-hole
procedure requires robustness of the separating device against radial loads. Radial
loads are mainly introduced through the shroud 22 which is supported by the intermediate
element 10 or the protective bush 20, respectively. The annular element 27 impedes
that radial loads cause a radial movement of the intermediate element 10 or the intermediate
core element 26, respectively, which would press the intermediate core element 26
against the base pipe and could mechanically damage the intermediate core element
26. The annular element 27 avoids that point loads can develop on surface or edges
of the intermediate core element 26 during impact.
[0084] Another advantageous property of the annular element 27 is related to the elastic
centering bands 29 provided on the lateral surface of the perforated pipe 7 which
are bearing the intermediate element 10. The elastic centering bands allow radial
movement of the intermediate element 10 under radial load. Under radial load, large
radial movement of the intermediate element which would consume the clearance of the
shroud protecting the central annular region, i.e. the clearance between shroud and
central annular region, can be largely prevented by the annular element 27.
[0085] Furthermore, by the recesses 28 of the annular element 27 it is assured that the
centering bands 29 cannot move in tangential direction on the lateral surface of the
base pipe. If the centering bands would move in tangential direction, they could lose
their centering function which could in turn adversely affect the proper filtering
function of the separating device.
[0086] The outer diameter of the annular element 27 may correspond to the inner diameter
of the intermediate core element 26.
[0087] Advantageously, the inner diameter of the annular element 27 may be adjusted as close
as possible to the outer diameter of the perforated pipe 7. With adjusting the inner
diameter to that of the perforated pipe, radial load can be directly transferred to
the perforated pipe without considerable movement. The recesses avoid deformation
of the centering bands. The radial movement can be kept at a minimum with accurate
machining. The minimum is mainly defined by manufacturing tolerances required for
assembly and easy axial movement on the perforated pipe. The anti-adhesive properties
of PTFE are particularly advantageous and enable to move the intermediate part lined
with the annular element with low frictional forces on the perforated pipe in axial
direction during assembly and also in operation for purposes of thermal compensation.
[0088] PTFE is a material with large thermal expansion coefficient. During thermal cycling
such as under operation of the separating device, the annular element tends to expand.
The recesses and openings provided in the annular element enable relaxation of thermal
stresses and therefore can reduce the risk of rupture of the intermediate core element.
[0089] Figure 2A shows a cross-sectional view in radial direction of an annular element
27. Figure 2B shows a 3D view of the annular element of Figure 2A. The annular element
27 has three recesses 28 which are provided in axial direction distributed along the
circumference of the annular element 27. The recesses 28 are provided axially parallelly
to the central axis of the separating device. The recesses are formed in such a way
that their depth corresponds to the radial thickness of the annular element 27, thereby
dividing the annular element 27 in three different segments. The number of segments
corresponds to the number of recesses 28.
[0090] Figure 2C shows a cross-sectional view in radial direction of a further annular element
27. Figure 2D shows a 3D view of the annular element of Figure 2C. The annular element
27 has three recesses 28 which are provided in axial direction distributed along the
inner circumference of the annular element 27. The recesses are provided axially parallelly
to the central axis of the separating device. The radial thickness of the annular
element 27 at the position of the recesses 28 is smaller than the radial thickness
of the annular element 27 at the positions outside of the recesses. The annular element
27 at the position of the recesses 28 should be thick enough to ensure the mechanical
stability of the annular element as one part. The annular element 27 further may have
openings 31. In the example of Figure 2D, two openings 31 with rectangular shape are
provided in each of the three recesses 28.
[0091] Figure 2E shows a detail of a cross-sectional view in axial direction of a separating
device as disclosed herein. The detail of Figure 2E is at the position of the intermediate
element 10 of the separating device.
[0092] Figure 2F shows the cross-sectional view in radial direction of the separating device
of Figure 2E. The cross-sectional view of Figure 2F is at the position of the intermediate
element 10 of the separating device.
[0093] The intermediate element 10 comprises an intermediate core element 26, a protective
bush 20 and an annular element 27. The intermediate core element 26 is produced from
a material selected from the group consisting of (i) ceramic materials; (ii) mixed
materials having fractions of ceramic or metallic hard materials and a metallic binding
phase; and (iii) powder metallurgical materials with hard material phases formed in-situ.
[0094] The intermediate element 10 is placed between the first section 11 and the second
section 12 of the central annular region 1, 13. The intermediate element 10 is co-centric
with the perforated pipe 7. The outer diameter of the intermediate element 10, i.e.
the outer diameter of the protective bush 20, is larger than the outer diameter of
the central annular region 1, 13. The protective bush 20 is co-centric with the intermediate
core element 26. The protective bush is located outside of the intermediate core element
26. The protective bush 20 protects the intermediate core element 26 from mechanical
damage. The protective bush 20 may be made from steel and may be shrunk onto the intermediate
core element 26.
[0095] The separating device with the details of Figures 2E and 2F further comprises three
bands 29 provided on the lateral surface of the perforated pipe and which are inside
the central annular region 1, 13 and inside the intermediate element 10. The three
bands 29 may be made from spring strip steel and are elastically deformable in radial
direction. The three bands have a profiled configuration with a curvatures having
an outwardly curved side oriented towards the central annular region 1, 13 and the
intermediate element 10, i.e. outwards.
[0096] The annular element 27 is co-centric with the intermediate core element 26 and is
located inside the intermediate core element 26. The annular element 27 protects the
intermediate core element 26 from mechanical damage by radial load. The annular element
27 has three recesses 28 in axial direction distributed along the circumference of
the annular element 27. The radial thickness of the annular element 27 at the position
of the recesses is smaller than the radial thickness of the annular element 27 at
the position outside of the recesses. Each of the three bands 29 is placed in one
of the recesses 28. The annular element 27 may be made from polytetrafluoroethylene
(PTFE). The outer diameter of the annular element 27 corresponds to the inner diameter
of the intermediate core element 26. The inner diameter of the annular element 27
corresponds as close as possible to the outer diameter of the perforated pipe 7, while
the intermediate element 10 with the annular element 27 inside is movable in axial
direction. Under radial load, large radial movement of the intermediate element 10
which would consume the clearance of the shroud 22 protecting the central annular
region, i.e. the clearance between shroud and central annular region, can be largely
prevented by the annular element 27.
[0097] The annular element 27 shown in Figures 2E and 2F corresponds to the annular element
of Figures 2C and 2D. The cross-sectional view in axial direction of Figure 2E is
at the sectional line designated by "2E" in Figure 2F. The cross-sectional view of
the intermediate element 10 at the upper part of Figure 2E is at a position outside
of the recesses 28 of the annular element 27, and the cross-sectional view of the
intermediate element 10 at the lower part of Figure 2E is at a position of one of
the three recesses 28 of the annular element 27. The radial thickness of the annular
element 27 at the position of one of the three recesses 28 as shown in the lower part
of Figure 2E is smaller than the radial thickness of the annular element 27 at the
position outside of the recesses 28 as shown in the upper part of Figure 2E. In the
lower part of Figure 2E, also the openings 31 are shown.
[0098] The intermediate element 10 and the protective bush 20, respectively, support the
shroud 22. The inner diameter of the shroud 22 at the position of the intermediate
element 10 is larger than the outer diameter of the central annular region 1, 13.
[0099] Each annular disc 2, 14, 15 of the separating device as disclosed herein comprises
a material independently selected from the group consisting of (i) ceramic materials;
(ii) mixed materials having fractions of ceramic or metallic hard materials and a
metallic binding phase; and (iii) powder metallurgical materials with hard material
phases formed in-situ.
[0100] The intermediate element 10 of the separating device as disclosed herein comprises
a material selected from the group consisting of (i) ceramic materials; (ii) mixed
materials having fractions of ceramic or metallic hard materials and a metallic binding
phase; and (iii) powder metallurgical materials with hard material phases formed in-situ.
[0101] The intermediate core element 26 of the separating device as disclosed herein comprises
a material selected from the group consisting of (i) ceramic materials; (ii) mixed
materials having fractions of ceramic or metallic hard materials and a metallic binding
phase; and (iii) powder metallurgical materials with hard material phases formed in-situ.
[0102] In some embodiments, the annular discs 2, 14, 15 are produced from, i.e. consists
of a material which is independently selected from the group consisting of (i) ceramic
materials; (ii) mixed materials having fractions of ceramic or metallic hard materials
and a metallic binding phase; and (iii) powder metallurgical materials with hard material
phases formed in-situ.
[0103] In some embodiments, the intermediate element 10 is produced from, i.e. consists
of a material selected from the group consisting of (i) ceramic materials; (ii) mixed
materials having fractions of ceramic or metallic hard materials and a metallic binding
phase; and (iii) powder metallurgical materials with hard material phases formed in-situ.
[0104] In some embodiments, the intermediate core element 26 is produced from, i.e. consists
of a material selected from the group consisting of (i) ceramic materials; (ii) mixed
materials having fractions of ceramic or metallic hard materials and a metallic binding
phase; and (iii) powder metallurgical materials with hard material phases formed in-situ.
[0105] These materials are typically chosen based upon their relative abrasion- and erosion-resistance
to solid particles such as sands and other mineral particles and also corrosion-resistance
to the extraction media and the media used for maintenance, such as for example acids.
[0106] The material which the annular discs comprise can be independently selected from
this group of materials, which means that each annular disc could be made from a different
material. But for simplicity of design and manufacturing, of course, all annular discs
of the separating device could be made from the same material.
[0107] The intermediate element can comprise or can be made from a different material as
the annular discs. Typically, the intermediate element comprises or is made from the
same material as the annular discs. The intermediate core element can comprise or
can be made from a different material as the annular discs. Typically, the intermediate
core element comprises or is made from the same material as the annular discs.
[0108] The ceramic materials which the annular discs, the intermediate element and the intermediate
core element can comprise or from which the annular discs, the intermediate element
and the intermediate core element are made can be selected from the group consisting
of (i) oxidic ceramic materials; (ii) non-oxidic ceramic materials; (iii) mixed ceramics
of oxidic and non-oxidic ceramic materials; (iv) ceramic materials having a secondary
phase; and (v) long- and/or short fiber-reinforced ceramic materials.
[0109] Examples of oxidic ceramic materials are materials chosen from Al
2O
3, ZrO
2, mullite, spinel and mixed oxides. Examples of non-oxidic ceramic materials are SiC,
B
4C, TiB
2 and Si
3N
4. Ceramic hard materials are, for example, carbides and borides. Examples of mixed
materials with a metallic binding phase are WC-Co, TiC-Fe and TiB2-FeNiCr. Examples
of hard material phases formed in situ are chromium carbides. An example of fiber-reinforced
ceramic materials is C/SiC. The material group of fiber-reinforced ceramic materials
has the advantage that it leads to still greater internal and external pressure resistance
of the separating devices on account of its greater strength in comparison with monolithic
ceramic.
[0110] The aforementioned materials are distinguished by being harder than the typically
occurring hard particles, such as for example sand and rock particles, that is to
say the HV (Vickers) or HRC (Rockwell method C) hardness values of these materials
lie above the corresponding values of the surrounding rock. Materials suitable for
the annular discs of the separating device according to the present disclosure have
HV hardness values greater than 11 GPa, or even greater than 20 GPa.
[0111] All these materials are at the same time distinguished by having greater brittleness
than typical unhardened steel alloys. In this sense, these materials are referred
to herein as "brittle-hard".
[0112] Materials suitable for the annular discs, for the intermediate element and for the
intermediate core element, respectively, of the separating device according to the
present disclosure have moduli of elasticity greater than 200 GPa, or even greater
than 350 GPa.
[0113] Materials with a density of at least 90%, more specifically at least 95%, of the
theoretical density may be used, in order to achieve the highest possible hardness
values and high abrasion and erosion resistances. Sintered silicon carbide (SSiC)
or boron carbide may be used as the material for the annular discs, the intermediate
element and the intermediate core element, respectively. These materials are not only
abrasion-resistant but also corrosion-resistant to the treatment fluids usually used
for flushing out the separating device and stimulating the borehole, such as acids,
for example HCI, bases, for example NaOH, or else steam.
[0114] Particularly suitable are, for example, SSiC materials with a fine-grained microstructure
(mean grain size ≤ 5 µm), such as those sold for example under the names 3M™ silicon
carbide type F and 3M™ silicon carbide type F plus from 3M Technical Ceramics, Kempten,
Germany. Furthermore, however, coarse-grained SSiC materials may also be used, for
example with a bimodal microstructure. In one embodiment, 50 to 90% by volume of the
grain size distribution consisting of prismatic, platelet-shaped SiC crystallites
of a length of from 100 to 1500 µm and 10 to 50% by volume consisting of prismatic,
platelet-shaped SiC crystallites of a length of from 5 to less than 100 µm (3M™ silicon
carbide type C from 3M Technical Ceramics, Kempten, Germany).
[0115] Apart from these single-phase sintered SSiC materials, liquid-phase-sintered silicon
carbide (LPS-SiC) can also be used as the material for the annular discs, the intermediate
element and the intermediate core element, respectively. An example of such a material
is 3M™ silicon carbide type T from 3M Technical Ceramics, Kempten, Germany. In the
case of LPS-SiC, a mixture of silicon carbide and metal oxides is used as the starting
material. LPS-SiC has a higher bending resistance and greater toughness, measured
as a Klc value, than single-phase sintered silicon carbide (SSiC).
[0116] In some embodiments, the material of each annular disc (2, 14, 15) is sintered silicon
carbide (SSiC).
[0117] In some embodiments, the material of the intermediate element (10) is sintered silicon
carbide (SSiC).
[0118] In some embodiments, the material of the intermediate core element (26) is sintered
silicon carbide (SSiC).
[0119] The separating device as disclosed herein may further comprise a thermal compensator
21 at the upper end or at the lower end or at both ends of the central annular region
(see Figure 1D). The thermal compensator 21 serves to compensate for the different
thermal expansions of the base pipe and the central annular region, from ambient temperature
to operation temperature. The thermal compensator may for example comprise one or
more springs, for example made from a metallic material such as steel, or a compensating
bush consisting of a material on the basis of polytetrafluoroethylene (PTFE), or a
tubular double-walled liquid-filled container, the outer walls of which are corrugated
in the axial direction.
[0120] Preferably, the separating device as disclosed herein does not comprise a thermal
compensator located near or incorporated in the intermediate element, i.e. the intermediate
element does not comprise a thermal compensator. The thermal compensator 21 is located
at the upper end of the first section 11 of the central annular region 1, 13 and at
the lower end of the second section 12 of the central annular region 1, 13, i.e. the
thermal compensator 21 is located near the end caps 8, 9. Preferably, the thermal
compensator is not located at the lower end of the first section 11 of the central
annular region 1, 13, and the thermal compensator is not located at the upper end
of the second section 12 of the central annular region 1, 13, i.e. the thermal compensator
is not located near or incorporated in the intermediate element 10.
[0121] A thermal compensator is not needed located near or incorporated in the intermediate
element of the separating device as disclosed herein, as the intermediate element
is movable in axial direction and differences in thermal expansion between the central
annular region and the base pipe can be compensated by the thermal compensator at
the end caps and by axial movement of the intermediate element and the first and second
section of the central annular region over the whole length of the central annular
region.
[0122] With the thermal compensator not being located near or incorporated in the intermediate
element, the filter area of the separating device can be increased by adding more
annular discs on the same length of the separating device and thus increasing inflow
area for fluid. The inflow area of fluid is essentially not disturbed by the intermediate
element of the separating device as disclosed herein. In separating devices of the
prior art, the intermediate element has thermal compensators and additional sealing
bushes for the thermal compensators which are both located at the upper end and lower
end of the intermediate element, and which consume a significantly larger length of
the separating device which cannot be used for filtering purposes and which interrupts
and disturbs the inflow of fluid, thereby dividing the inflow of fluid in two separate
parts.
[0123] The intermediate element 10 of the separating device as disclosed herein is erosion
resistant to the abrasive fluid flows and corrosion resistant to the media to be extracted
and the media used for maintenance such as acids. As the thermal compensator 21 is
not located near or incorporated in the intermediate element 10, and as the intermediate
element 10 as well as the central annular region 1, 13 are erosion and corrosion resistant,
the complete annular stack composed of central annular region 1, 13 and intermediate
element 10, or intermediate core element 26, respectively, is erosion resistant and
corrosion resistant. The complete annular stack composed of central annular region
1, 13 and intermediate element 10, or intermediate core element 26, respectively,
is not interrupted by any metallic or other parts not being erosion and corrosion
resistant. The inflow of fluid is not divided into two separate parts, and the separating
device as disclosed herein can be used for harsh environments, that is for reservoirs
to be exploited with streaks having high inflow and high erosional impact. The service
life of the separating device as disclosed herein is increased for harsh environments,
that is for reservoirs to be exploited with streaks having high inflow and high erosional
impact. Thus a separating device with a larger filter length can be deployed, irrespective
of length of zones with high inflow and high erosional impact.
[0124] The protective bush 20 may have a radial thickness of from 1 to 20 mm. The intermediate
core element 26 may have a radial thickness of from 8 to 20 mm. The annular element
27 may have a radial thickness of from 0.5 to 6 mm. The axial length of the intermediate
element 10 may be from 10 to 140 mm and typically is from 40 to 70 mm.
[0125] The separating device as disclosed herein may further comprise a number of n further
intermediate elements 10, wherein n is an integer from 1 to 10. If a number of n further
intermediate elements 10 are present, the central annular region 1, 13 further comprises
a number of n further sections, and each further intermediate element 10 is placed
between two adjacent sections of the central annular region.
[0126] To protect the brittle-hard annular discs from mechanical damage during handling
and fitting into the borehole, the separating device is surrounded by a tubular shroud
22 (see Figures 1A, 2E, 2F) that can be freely passed through by a flow. The shroud
is protecting each section of the central annular region.
[0127] This shroud may be configured for example as a coarse-mesh screen and preferably
as a perforated plate. The shroud may be produced from a metallic material, such as
from steel, particularly from corrosion-resistant steel. The shroud may be produced
from the same material as that used for producing the base pipe.
[0128] The shroud can be held on both sides by the end caps, it may also be firmly connected
to the end caps. This fixing is possible for example by way of adhesive bonding, screwing
or pinning, the shroud may be welded to the end caps after assembly.
[0129] The inner diameter of the shroud must be greater than the outer diameter of the annular
discs. For mechanical protection of the annular discs of the central annular region,
the inner diameter of the shroud should be at least 0.5 mm larger than the outer diameter
of the central annular region. Typically, the inner diameter of the shroud is at most
15 mm larger than the outer diameter of the central annular region. The radial distance
between shroud and central annular region can be selected depending on the radial
thickness of the shroud and on the radial loads that need to be withstand. The radial
thickness of the shroud usually is from 1 to 20 mm, preferably 1 to 8 mm.
[0130] The inner diameter of the shroud being greater than the outer diameter of the annular
discs is also necessary for technical reasons relating to flow. It has been found
to be favorable in this respect that the inner diameter of the shroud is at least
0.5 mm and at most 15 mm greater than the outer diameter of the annular discs. The
inner diameter of the shroud may be at least 1.5 mm and at most 8 mm greater than
the outer diameter of the annular discs.
[0131] The inner diameter of the shroud at the position of the intermediate element is such
that it fits to the outer diameter of the intermediate element 10. If the intermediate
element comprises a protective bush 20, the inner diameter of the shroud at the position
of the intermediate element is such that it fits to the outer diameter of the protective
bush 20.
[0132] The shroud 22 may be provided in one single part. The shroud may also be provided
in two or more separate parts. On the interface between two adjacent parts of the
shroud, an intermediate element 10 must be placed as support for the shroud. During
assembly, the shroud 22 is placed on the end caps 8, 9 and on the intermediate element
10, and the end caps 8, 9 and the intermediate element 10 support the shroud 22. If
the shroud is provided in more than one part, each part of the shroud can be assembled
separately. If the intermediate element 10 comprises a protective bush 20, the shroud
22 is placed on the protective bush 20, and the end caps 8, 9 and the protective bush
support the shroud 22. The shroud may or may not be firmly connected to the intermediate
element.
[0133] The distance of the intermediate elements 10 to one another may be selected depending
on the radial loads which need to be withstand and on the thickness of the shroud,
without consuming the radial distance between shroud and central annular region.
[0134] The intermediate element 10 has the function of a spacer for the shroud 22. By the
intermediate element 10, the shroud is positioned at a distance from the annular discs.
A distance between shroud and annular discs is maintained even if the separating device
is bended or loaded during installation or operation. If the shroud would touch the
annular discs during bending or loading, the annular discs might be damaged which
might lead to loss of sand control.
[0135] The central annular region of the separating device disclosed herein can, and typically
does, comprise more than 3 annular discs. The number of annular discs in the central
annular region can be from 3 to 500, but also larger numbers of annular discs are
possible. For example, the central annular region can comprise 50, 100, 250 or 500
annular discs.
[0136] The annular discs 2 and the annular discs 14, 15, respectively, of the central annular
region 1, 13 are stacked on top of each other, resulting in a stack of annular discs.
The annular discs 2 and the annular discs 14, 15, respectively, are stacked in such
a way that a separating gap 6 for the removal of solid particles is present in each
case between adjacent annular discs.
[0137] Every upper side 3, 16 of an annular disc 2, 14 which has one or more spacers may
be inwardly or outwardly sloping, preferably inwardly sloping, in the regions between
the spacers (see Figures 3D, 4D), and every underside 17 of an annular disc 14 which
has one or more spacers may be inwardly or outwardly sloping, preferably inwardly
sloping, in the regions between the spacers (see Figure 4D).
[0138] If the upper side, or the upper side and underside, respectively, of the annular
discs which have one or more spacers, is inwardly or outwardly sloping in the regions
between the spacers, in the simplest case, the sectional line on the upper side of
the ring cross-section of the annular discs is straight and the ring cross-section
of the annular discs in the portions between the spacers is trapezoidal (see Figures
3D, 4D), the thicker side of the ring cross-section having to lie on the respective
inlet side of the flow to be filtered. If the flow to be filtered comes from the direction
of the outer circumferential surface of the central annular region, the thickest point
of the trapezoidal cross-section must lie on the outside and the upper side of the
annular discs is inwardly sloping. If the flow to be filtered comes from the direction
of the inner circumferential surface of the annular disc, the thickest point of the
trapezoidal cross-section must lie on the inside and the upper side of the annular
discs is outwardly sloping. The forming of the ring cross-section in a trapezoidal
shape, and consequently the forming of a separating gap that diverges in the direction
of flow, has the advantage that, after passing the narrowest point of the filter gap,
irregularly shaped particles, i.e. non-spherical particles, tend much less to get
stuck in the filter gap, for example due to rotation of the particles as a result
of the flow in the gap. Consequently, a separating device with a divergent filter
gap formed in such a way is less likely to become plugged and clogged than a separating
device in which the separating gaps have a filter opening that is constant over the
ring cross-section.
[0139] The height of the separating gap, i.e. the filter width, may be from 50 to 1000 µm.
The height of the separating gap is measured at the position of the smallest distance
between two adjacent annular discs.
[0140] The annular discs 2, 14, 15 may have a height of 1 to 12 mm. More specifically, the
height of the annular discs may be from 2 to 7 mm. The height of the annular discs
is the thickness of the annular discs in axial direction.
[0141] In some embodiments, the annular discs 14 having one or more spacers on the upper
side 16 and the underside 17 have a height of 1 to 12 mm, and the annular discs 15
which do not comprise any spacers may have the same height as the annular discs 14
with spacers, or may be thinner than the annular discs 14 with spacers. The annular
discs 15 may have a height of 2 to 7 mm, for example. With the reduced height of the
annular discs 15 which do not comprise any spacers, the open flow area can be increased.
[0142] The base thickness of the annular discs is measured in the region between the spacers
and, in the case of a trapezoidal cross-section, on the thicker side in the region
between the spacers. The axial thickness or height of the annular discs in the region
of the spacers corresponds to the sum of the base thickness and the filter width.
[0143] The height of the spacers determines the filter width of the separating device, that
is to say the height of the separating gap between the individual annular discs. The
filter width additionally determines which particle sizes of the solid particles to
be removed, such as for example sand and rock particles, are allowed to pass through
by the separating device and which particle sizes are not allowed to pass through.
The height of the spacers is specifically set in the production of the annular discs.
[0144] For any particular separating device, the annular discs may have uniform base thickness
and filter width, or the base thickness and/or filter width may vary along the length
of the separating device (e.g., to account for varying pressures, temperatures, geometries,
particle sizes, materials, and the like).
[0145] The outer contours of the annular discs may be configured with a bevel 35, as illustrated
in Figures 3C - 3D and 4C - 4D. It is also possible to configure the annular discs
with rounded edges. This may, for some applications, represent even better protection
of the edges (versus straight edged) from the edge loading that is critical for the
materials from which the annular discs are produced.
[0146] The circumferential surfaces (lateral surfaces) of the annular discs may be cylindrical.
However, it is also possible to form the circumferential surfaces as outwardly convex,
in order to achieve a better incident flow.
[0147] In practice, it is expected that the annular discs are produced with an outer diameter
that is adapted to the borehole of the extraction well provided in the application
concerned, so that the separating device according to the present disclosure can be
introduced into the borehole with little play, in order to make best possible use
of the cross-section of the extraction well for achieving a high delivery output.
The outer diameter of the annular discs may be 20 - 250 mm, but outer diameters greater
than 250 mm are also possible, as the application demands.
[0148] The radial ring width of the annular discs may lie in the range of 8 - 20 mm. These
ring widths are suitable for separating devices with base pipe diameters in the range
of 6 cm to 14 cm (2⅜ to 5½ inches).
[0149] The spacers arranged on the upper side, or on the upper side and the underside, respectively,
of the annular discs have planiform contact with the adjacent annular disc. The spacers
make a radial throughflow possible and therefore may be arranged radially aligned
on the first major surface of the annular discs, or on the second major surface of
the annular discs, respectively. The spacers may, however, also be aligned at an angle
to the radial direction.
[0150] The transitions between the surface of the annular discs, i.e. the upper side, or
the upper side and the underside of the annular discs, and the spacers are typically
not formed in a step-shaped or sharp-edged manner. Rather, the transitions between
the surface of the annular discs and the spacers are typically configured appropriately
for the material from which the annular discs are made, i.e. the transitions are made
with radii that are gently rounded. This is illustrated in Figures 3E and 4E.
[0151] The contact area of the spacers, that is to say the planar area with which the spacers
are in contact with the adjacent annular disc are not particularly limited, and may
be, for instance, rectangular, round, rhomboidal, elliptical, trapezoidal or else
triangular, while the shaping of the corners and edges should always be appropriate
for the material from which the annular discs are made, e.g. rounded.
[0152] Depending on the size of the annular discs, the contact area 25 of the individual
spacers is typically between 4 and 100 mm
2.
[0153] The spacers 5 may be distributed over the circumference of the annular discs (see
Figures 3A and 4A). The spacers 5 may be distributed homogeneously or non-homogeneously
over the circumference of the annular discs. The number of spacers may be even or
odd.
[0154] The annular discs of the separating device disclosed herein may be prepared by the
methods that are customary in technical ceramics or powder metallurgy, that is to
say by die pressing of pressable starting powders and subsequent sintering. The annular
discs may be formed on mechanical or hydraulic presses in accordance with the principles
of "near-net shaping", debindered and subsequently sintered to densities > 90% of
the theoretical density. The annular discs may be subjected to 2-sided facing on their
upper side and underside.
[0155] In Figures 3A - 3L, one embodiment of a central annular region of a separating device
as disclosed herein is represented. Figures 3A - 3F show various details of an individual
annular disc 2 of the central annular region 1. Figures 3G - 3L show the central annular
region 1 constructed from annular discs 2 of Figures 3A - 3F, representing various
details of the stack of annular discs. Figure 3A shows a plan view of the upper side
3 of the annular disc 2, Figure 3B shows a cross-sectional view along the sectional
line denoted in Figure 3A by "3B", Figures 3C - 3D show enlarged details of the cross-sectional
view of Figure 3B. The enlarged detail of Figure 3C is in the region of a spacer,
the enlarged detail of Figure 3D is in the region between two spacers. Figure 3F shows
a 3D view of the annular disc 2, and Figure 3E shows a 3D representation along the
sectional line denoted in Figure 3A by "3E". Figure 3G shows a plan view of the central
annular region 1 constructed from annular discs 2 of Figures 3A - 3F, Figure 3H shows
a cross-sectional view along the sectional line denoted in Figure 3G by "3H", Figures
3I - 3J show enlarged details of the cross-sectional view of Figure 3H. The enlarged
detail of Figure 3I is in the region of a spacer, the enlarged detail of Figure 3J
is in the region between two spacers. Figure 3K shows a 3D view of the central annular
region 1, and Figure 3L shows a 3D representation along the sectional line denoted
in Figure 3G by "3L".
[0156] The removal of the solid particles takes place at the inlet opening of a separating
gap 6, which may be divergent, i.e. opening, in the direction of flow (see Figures
3D and 3J) and is formed between two annular discs lying one over the other. The annular
discs are designed appropriately for the materials from which the annular discs are
produced and the operational environment intended for the devices made with such annular
discs, e.g., materials may be chosen for given pressure, temperature and corrosive
operating conditions, and so that cross-sectional transitions may be configured without
notches so that the occurrence of flexural stresses is largely avoided by the structural
design.
[0157] The upper side 3 of each annular disc 2 has fifteen spacers 5 distributed over its
circumference. The underside 4 does not comprise any spacers. The spacers 5 are of
a defined height, with the aid of which the height of the separating gap 6 (gap width
of the filter gap, filter width) is set. The spacers are not separately applied or
subsequently welded-on spacers, they are formed directly in production, during the
shaping of the annular discs.
[0158] The contact area 25 of the spacers 5 is planar (see Figures 3C, 3E), so that the
spacers 5 have a planar contact area with the underside 4 of the adjacent annular
disc. The upper side 3 of the annular discs is plane-parallel with the underside 4
of the annular discs in the region of the contact area 25 of the spacers 5, i.e. in
the region of contact with the adjacent annular disc. The underside 4 of the annular
discs is formed as smooth and planar and at right angles to the disc axis and the
central axis of the central annular region. At the planar contact area of the spacers,
the annular discs contact the respective adjacent annular disc.
[0159] The upper side 3 of an annular disc 2 having fifteen spacers 5 is inwardly sloping,
in the regions between the spacers. The ring cross-section of the annular discs in
the portions between the spacers is trapezoidal (see Figure 3D), the thicker side
of the ring cross-section lying on the outside, i.e. on the inlet side of the flow
to be filtered.
[0160] In Figures 4A - 4L, a further embodiment of a central annular region of a separating
device as disclosed herein is represented. Figures 4A - 4F show various details of
individual annular discs 14 of the central annular region 13. Figures 4G - 4L show
the central annular region 13 constructed from annular discs 14 and 15, representing
various details of the stack of annular discs. Figure 4A shows a plan view of the
upper side 16 and of the underside 17 of the annular disc 14, Figure 4B shows a cross-sectional
view along the sectional line denoted in Figure 4A by "4B", Figures 4C - 4D show enlarged
details of the cross-sectional view of Figure 4B. The enlarged detail of Figure 4C
is in the region of the spacers, the enlarged detail of Figure 4D is in the region
between the spacers. Figure 4F shows a 3D view of the annular disc 14, and Figure
4E shows a 3D representation along the sectional line denoted in Figure 4A by "4E".
Figure 4G shows a plan view of the central annular region 13 constructed from annular
discs 14 and 15, Figure 4H shows a cross-sectional view along the sectional line denoted
in Figure 4G by "4H", Figures 4I - 4J show enlarged details of the cross-sectional
view of Figure 4H. The enlarged detail of Figure 4I is in the region of a spacer,
the enlarged detail of Figure 4J is in the region between the spacers. Figure 4K shows
a 3D view of the central annular region 13, and Figure 4L shows a 3D representation
along the sectional line denoted in Figure 4G by "4L".
[0161] The stack of annular discs 13 is composed of annular discs 14 and 15 which are stacked
in an alternating manner. Every second annular disc in the stack is an annular disc
14 having fifteen spacers 5 on the upper side 16 of the annular disc 14 distributed
over its circumference (see Figure 4A) and fifteen spacers 5 on the underside 17 of
the annular disc 14 distributed over its circumference. The plan view of the upper
side 16 of Figure 4A is identical to the plan view of the underside 17. The spacers
5 of the annular discs 14 are of a defined height, with the aid of which the height
of the separating gap 6 (gap width of the filter gap, filter width) is set. The spacers
are not separately applied or subsequently welded-on spacers, they are formed directly
in production, during the shaping of the annular discs.
[0162] The respectively adjacent annular discs of the annular discs 14 in the stack of annular
discs 13 are annular discs 15 as shown in Figures 4H - 4J. The upper side 18 and the
underside 19 of the annular discs 15 do not comprise any spacers.
[0163] The removal of the solid particles takes place at the inlet opening of a separating
gap 6, which may be divergent, i.e. opening, in the direction of flow (see Figures
4D and 4J) and is formed between two adjacent annular discs lying one over the other.
The annular discs are designed appropriately for the materials from which the annular
discs are produced and the operational environment intended for the devices made with
such annular discs, e.g., materials may be chosen for given pressure, temperature
and corrosive operating conditions, and so that cross-sectional transitions may be
configured without notches so that the occurrence of flexural stresses is largely
avoided by the structural design.
[0164] The contact area 25 of the spacers 5 is planar (see Figures 4C, 4E), so that the
spacers 5 have a planar contact area with the underside 19 or upper side 18 of the
adjacent annular disc 15. The upper side 16 of the annular discs 14 is plane-parallel
with the underside 17 of the annular discs 14 in the region of the contact area 258
of the spacers 5, i.e. in the region of contact with the adjacent annular disc. At
the planar contact area of the spacers, the annular discs contact the respective adjacent
annular disc 15.
[0165] The upper side 18 and the underside 19 of the annular discs 15 is formed as smooth
and planar and at right angles to the disc axis and the central axis of the central
annular region.
[0166] The upper side 16 and the underside 17 of an annular disc 14 having fifteen spacers
5 is inwardly sloping, in the regions between the spacers 5. The ring cross-section
of the annular discs in the portions between the spacers is trapezoidal (see Figure
4D), the thicker side of the ring cross-section lying on the outside, i.e. on the
inlet side of the flow to be filtered.
[0167] The separating device according to the present disclosure may be used for removing
solid particles from a fluid. A fluid as used herein means a liquid or a gas or combinations
of liquids and gases.
[0168] The separating device according to the present disclosure may be used in extraction
wells in oil and/or gas reservoirs for separating solid particles from volumetric
flows of mineral oil and/or natural gas. The separating device may also be used for
other filtering processes for removing solid particles from fluids outside of extraction
wells, processes in which a great abrasion resistance and a long lifetime of the separating
device are required, such as for example for filtering processes in mobile and stationary
storage installations for fluids or for filtering processes in naturally occurring
bodies of water, such as for instance in the filtering of seawater. The separating
device disclosed herein can also be used in a process for extracting ores and minerals.
In the extraction of ore and many other minerals, there are problems of abrasion and
erosion in the removal of solid particles from fluid flows. The separating device
according to the present disclosure is particularly suitable for the separation of
solid particles from fluids, in particular from mineral oil, natural gas and water,
in extraction wells in which high and extremely high rates of flow and delivery volumes
occur.