U.S. patent application number 11/715214 was filed with the patent office on 2008-09-11 for sand control screen having a micro-perforated filtration layer.
Invention is credited to Eric Paul Boudreaux, Ronald Glen Dusterhoft, Carl Bismarck Ferguson, Nicholas Hubert Gardiner, Tommy Frank Grigsby, Floyd Randolph Simonds.
Application Number | 20080217002 11/715214 |
Document ID | / |
Family ID | 39740477 |
Filed Date | 2008-09-11 |
United States Patent
Application |
20080217002 |
Kind Code |
A1 |
Simonds; Floyd Randolph ; et
al. |
September 11, 2008 |
Sand control screen having a micro-perforated filtration layer
Abstract
A sand control screen (40) includes a perforated base pipe (42)
and a filter layer (50) that has micro-perforations (52) therein.
The filter layer (50) is attached to the base pipe (42) along the
entire length of the filter layer (50). Channels (46) are formed
between the base pipe (42) and the filter layer (50) to allow fluid
to flow therebetween. The sand control screen (40) is formed by
micro-perforating a length of material, such as sheet metal, to
form the filter layer (50), creating channels (46) that will allow
fluids to flow between the base pipe (42) and filter layer (50),
wrapping the filter layer (50) around the base pipe (42), attaching
the filter layer (50) to the base pipe (42) along the length of the
filter layer (50) and creating a seam between the two edges of the
filter layer (50).
Inventors: |
Simonds; Floyd Randolph;
(Dallas, TX) ; Dusterhoft; Ronald Glen; (Katy,
TX) ; Gardiner; Nicholas Hubert; (Katy, TX) ;
Ferguson; Carl Bismarck; (La Porte, TX) ; Grigsby;
Tommy Frank; (Katy, TX) ; Boudreaux; Eric Paul;
(New Iberia, LA) |
Correspondence
Address: |
LAWRENCE R. YOUST
2001 Ross Avenue, Suite 3000
DALLAS
TX
75201
US
|
Family ID: |
39740477 |
Appl. No.: |
11/715214 |
Filed: |
March 7, 2007 |
Current U.S.
Class: |
166/230 ;
166/227 |
Current CPC
Class: |
E21B 43/084
20130101 |
Class at
Publication: |
166/230 ;
166/227 |
International
Class: |
E21B 43/08 20060101
E21B043/08 |
Claims
1. A sand control screen comprising: a base pipe having at least
one opening that allows fluid flow therethrough; a filter layer
attached to the base pipe, the filter layer having a plurality of
micro-perforations; and a drainage layer formed between the base
pipe and the filter layer to allow fluid flow between the base pipe
and the filter layer.
2. The sand control screen as recited in claim 1 wherein the filter
layer has a thickness between about 1/32nd of an inch and about
1/4th of an inch.
3. The sand control screen as recited in claim 1 wherein the filter
layer is a sheet metal filter layer.
4. The sand control screen as recited in claim 1 wherein the shape
of the micro-perforations at the surface of the filter layer is
chosen from the group consisting of a circle, an ellipse and a
slot.
5. The sand control screen as recited in claim 1 wherein the shape
of the micro-perforations at the surface of the filter layer is
chosen from the group consisting of a square, a triangle and a
multi-sided polygon.
6. The sand control screen as recited in claim 1 wherein the
micro-perforations have a maximum width of 500 microns.
7. The sand control screen as recited in claim 1 wherein the
micro-perforations have a tapering cross-section through the filter
layer.
8. The sand control screen as recited in claim 1 wherein the filter
layer is attached to the base pipe by one of adhesion, a friction
fit and fusion bonding.
9. The sand control screen as recited in claim 1 wherein the
drainage layer further comprises channels.
10. The sand control screen as recited in claim 9 wherein the
channels are formed in one of the outside surface of the base pipe
and the inside surface of the filter layer.
11. The sand control screen as recited in claim 1 wherein the
drainage layer further comprises one of wire wrap and wire
mesh.
12. A sand control screen comprising: a base pipe having at least
one opening that allows fluid flow therethrough; a sheet metal
filter layer wrapped around the base pipe, the filter layer having
a plurality of micro-perforations, the filter layer being
corrugated to form channels between the filter layer and the base
pipe; and at least one connector coupling the filter layer to the
base pipe.
13. The sand control screen as recited in claim 12 wherein the
filter layer has a thickness between about 1/32nd of an inch and
about 1/4th of an inch.
14. The sand control screen as recited in claim 12 wherein the
shape of the micro-perforations at the surface of the filter layer
is chosen from the group consisting of a circle, an ellipse and a
slot.
15. The sand control screen as recited in claim 12 wherein the
shape of the micro-perforations at the surface of the filter layer
is chosen from the group consisting of a square, a triangle and a
multi-sided polygon.
16. The sand control screen as recited in claim 12 wherein the
micro-perforations have a maximum width of 500 microns.
17. The sand control screen as recited in claim 12 wherein the
micro-perforations are placed at the peaks and valleys of the
corrugations.
18. The sand control screen as recited in claim 12 wherein the
micro-perforations are spaced uniformly across the filter
layer.
19. A method of making a sand control screen, the method
comprising: fabricating a plurality of openings in the wall of a
base pipe, the plurality of openings allowing fluid flow
therethrough; creating a plurality of micro-perforations in a
length of sheet metal having a first and a second edge opposite
each other to form a filter layer; forming a plurality of channels
that allow fluid flow between the filter layer and the base pipe;
shaping the filter layer to fit around the base pipe wherein the
first edge and the second edge of the filter layer are
substantially adjacent each other; attaching the filter layer to
the outer surface of the base pipe; and sealing the first edge of
the filter layer to the second edge.
20. The method of making a sand control screen as recited in claim
19, wherein the filter layer is corrugated prior to the shaping
step.
21. The method of making a sand control screen as recited in claim
19, wherein the shaping step and the attaching step are performed
at the location where the sand screen is used.
22. The method of making a sand control screen as recited in claim
19, wherein the attaching step uses an attachment method chosen
from the group of fusion bonding, friction fitting and
adhesion.
23. The method of making a sand control screen as recited in claim
19, wherein the creating step creates micro-perforations having a
tapering cross-section.
24. The method of making a sand control screen as recited in claim
23, wherein the shaping step orients a smaller opening of the
tapering cross-section on the exterior of the filter layer.
25. The method of making a sand control screen as recited in claim
19, wherein the creating step uses one of a water jet and a laser
to create the micro-perforations.
Description
TECHNICAL FIELD OF THE INVENTION
[0001] This invention relates, in general, to a sand control device
used during the production of oil, gas or water and a manufacturing
process related to the same and, in particular, to a sand control
screen having a micro-perforated filtration layer.
BACKGROUND OF THE INVENTION
[0002] Without limiting the scope of the present invention, its
background will be described with reference to producing fluid from
a subterranean formation, as an example.
[0003] After drilling each of the sections of a subterranean
wellbore, individual lengths of relatively large diameter metal
tubulars are typically secured together to form a casing string
that is positioned within each section of the wellbore and cemented
in place. This casing string is used to increase the integrity of
the wellbore by preventing the wall of the hole from collapsing and
to prevent movement of fluids from one formation to another
formation.
[0004] Once the process of drilling and installing casing is
finished, the completion process may begin. The completion process
comprises numerous steps including the creation of hydraulic
openings or perforations through the casing string, the cement and
a short distance into the desired formation or formations so that
production fluids may enter the interior of the wellbore. In
addition, the completion process may involve formation stimulation
to enhance production, installation of sand control devices to
prevent sand production and the like. The completion process also
includes installing a production tubing string within the well
casing. Unlike the casing string that forms a part of the wellbore
itself, the production tubing string is used to produce the well by
providing the conduit for formation fluids to travel from the
formation depth to the surface.
[0005] Typically, the production tubing string extends from the
surface to the formations traversed by the well and includes one or
more production packers. The purpose of the packers is to support
the production tubing and other completion equipment, such as one
or more sand control screens that may be placed adjacent to the
producing formations, and to seal the annulus between the outside
of the production tubing and the inside of the well casing to block
movement of fluids through the annulus past the packer locations.
Accordingly, once the production tubing string, including the
production packers and sand control screens are in place, all
production from the formation that enters the production tubing
must pass through a sand control screen.
[0006] One purpose of the sand control screens is to prevent the
movement of unconsolidated formation particles such as sand into
the production tubing. Such particle movement commonly occurs
during production from completions in loose sandstone or following
hydraulic fracture of a formation. Production of these materials
causes numerous problems in the operation of oil, gas or water
wells. These problems include plugging of formations, tubing and
flow lines, as well as erosion of tubing, downhole equipment and
surface equipment. These problems lead to poor productivity, high
maintenance costs and unacceptable well downtime.
[0007] Existing screens typically use a wire wrap filter media or a
wire mesh filter media attached to a base pipe to achieve sand
control. Wire wrap sand screens may comprise a continuous single
wire wrapped around the base pipe. More recent versions use a
jacket that is fully formed from a single wire prior to attachment
to the base pipe, with vertical ribs providing a stand-off from the
base pipe. Variations in the gauge of wire and corresponding
variations in the spacing between wraps of the wire provide sand
screens for different conditions. Wire mesh sand screens use one or
more woven metal layers to trap particulate matter. As with wire
wrap screens, wire mesh sand screens are available in a number of
gauges having openings of various sizes.
[0008] In addition, some screen designs use prepacked sand confined
around the perforated base pipe. These prepacked screens are
constructed by fabricating the metal components, then forcing pack
sand, either resin coated or uncoated, between the perforated base
pipe and an inner wire screen or between an inner wire screen and
an outer wire screen of a multi-layer screen. Alternatively or
additionally, a gravel pack may be placed in the production
interval surrounding the installed sand control screens.
[0009] It has been found, however, that existing sand screens
continue to have a number of drawbacks. For example, variations in
the gauge of the wire or improper manufacture can result in
inconsistencies in the opening size. Larger gauges of wire become
increasingly difficult to bend, while smaller gauges are more
easily damaged in the processes of manufacture and installation or
during production. Additionally, screens that use multiple filter
layers are, by their nature, difficult or impossible to clean.
Still further, the attachment of the wire wrap screen or wire mesh
screen to the base pipe is an ongoing cause of concern. The sand
screen filters are typically attached to the base pipe with
conventional welding at both ends of the filter layer. A failure of
any portion of the weld results in an uncontrolled opening and a
loss of sand control. Therefore, a need has arisen for a sand
screen that provides the desired sand control function, is robust,
easy to clean and simple to manufacture.
SUMMARY OF THE INVENTION
[0010] The present invention disclosed herein comprises a sand
control screen having a micro-perforated filter layer for filtering
particles out of fluid produced from a wellbore and a method for
manufacturing the same. The sand screen of the present invention
allows for precise, reliably reproducible and infinitely variable
opening size, shape, density and pattern in the micro-perforated
filter layer, thereby providing the desired sand control function.
In addition, the sand control screen of the present invention is
robust, easy to clean and simple to manufacture.
[0011] The sand control screen having a micro-perforated filter
layer of the present invention includes a base pipe having a
plurality of openings that allow fluid flow therethrough and a
filter layer having a plurality of micro-perforations. The filter
layer wraps around the base pipe and is attached thereto. A
drainage layer such as channels, wire wrap or wire mesh between the
base pipe and filter layer allows production fluid to flow between
the filter layer and the base pipe.
[0012] In one embodiment of the sand control screen having a
micro-perforated filter layer, the filter layer is made of sheet
metal that is wrapped around the base pipe. The sheet metal may be
flat or corrugated. In the flat sheet metal embodiments of the sand
control screen, channels may be formed in the outside surface of
the base pipe or on the inside surface of the filter layer. In the
corrugated sheet metal embodiments of the sand control screen, the
corrugations form the channels between the filter layer and the
base pipe.
[0013] The filter layer may be attached to the base pipe using a
variety of techniques including fusion bonding, a friction fit,
adhesives or the like. Alternatively or additionally, the filter
layer may be attached to the base pipe using connectors, such as
end caps, that seal the ends of the filter layer to the base pipe.
The end caps may be attached to the base pipe using welded,
threading or similar techniques.
[0014] In some embodiments of the sand control screen, the filter
layer has a thickness between about 1/32nd inch and about 1/4th
inch. In other embodiments, the opening shape of the
micro-perforations at the surface of the filter layer can be a
circle, an ellipse, a slot or other similar shape having a radius.
Alternatively, the opening shape of the micro-perforations at the
surface of the filter layer may have sharp edges such as squares,
rectangles, triangles or other multi sided polygon or shape. In
certain embodiments, the micro-perforations may have a tapering
cross-section through the filter layer wherein the smaller opening
of this tapering cross-section may be oriented to either the
exterior or the interior of the filter layer.
[0015] In one embodiment of the sand control screen having a
micro-perforated filter layer, the opening size of the
micro-perforations has a maximum width of 500 microns. In other
embodiments, the maximum width of the micro-perforations is between
about 50 microns and 500 microns. In another embodiment of the sand
control screen having a micro-perforated filter layer, the opening
density of the micro-perforations is between about 100 and 200
openings per square inch. In other embodiments, the opening density
of the micro-perforations may be less than 100 openings per inch or
more than 200 openings per inch.
[0016] In one embodiment of the sand control screen having a
micro-perforated filter layer, the opening pattern of the
micro-perforations has a uniform distribution. In other
embodiments, the opening pattern may include a nonuniform or
selected distribution. For example, in the corrugated sheet metal
embodiment, the micro-perforations can be placed at the peaks and
valleys of the corrugations, in the sides of the corrugations or in
any other arrangement that is desired. The size, shape, density and
pattern of the micro-perforations are determined by the desired
flow area, the desired filtration capacity, the constituents being
separated from one another and the like.
[0017] In another aspect, the present invention is directed to a
method of making a sand control screen that includes fabricating a
plurality of openings in the wall of a base pipe and creating a
plurality of micro-perforations in a length of sheet metal having a
first and a second edge opposite each other to form a filtration
media. The method further includes forming a plurality of channels
that allow fluid flow between the filter layer and the base pipe,
shaping the filter layer to fit around the base pipe, bringing the
first edge and the second edge of the filter layer substantially
adjacent each other, attaching the filter layer to the outer
surface of the base pipe and coupling the first edge of the filter
layer to the second edge.
[0018] In some embodiments, the step of creating a plurality of
micro-perforations in a length of sheet metal may be accomplished
using a water jet, a laser or similar technique. In certain
installations, the steps of shaping the filter layer to fit around
the base pipe, bringing the first edge and the second edge of the
filter layer substantially adjacent each other, attaching the
filter layer to the outer surface of the base pipe and coupling the
first edge of the filter layer to the second edge may be performed
at the location where the sand screen will be used.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] For a more complete understanding of the features and
advantages of the present invention, references now made to the
detailed description of the invention along with the accompanying
figures in which corresponding numerals in the different figures
refer to corresponding parts and in which:
[0020] FIG. 1 is a schematic illustration of an offshore oil and
gas platform operating a sand control screen having a
micro-perforated filter layer of the present invention;
[0021] FIG. 2 is a side elevation, partially cut away, of an
embodiment of a sand control screen having a micro-perforated
filter layer of the present invention;
[0022] FIGS. 3A and 3B each show a section of the base pipe from an
embodiment of a sand control screen having a micro-perforated
filter layer of the present invention, enlarged to display knurling
on the surface;
[0023] FIG. 4 is a cross-section through one wall of the embodiment
of FIG. 2;
[0024] FIG. 5A is a side elevation of an embodiment of a sand
control screen having a micro-perforated filter layer of the
present invention;
[0025] FIG. 5B is a cross-section through a portion of the sand
control screen having a micro-perforated filter layer shown in FIG.
5A;
[0026] FIG. 6 is a side elevation of an embodiment of a sand
control screen having a micro-perforated filter layer of the
present invention;
[0027] FIGS. 7A and 7B respectively display a cross-section through
a corrugated filter layer of a sand control screen having a
micro-perforated filter layer and an associated pattern of
micro-perforations in the filter layer;
[0028] FIGS. 8A and 8B respectively display a cross-section through
a corrugated filter layer of a sand control screen having a
micro-perforated filter layer and an associated pattern of
micro-perforations in the filter layer;
[0029] FIGS. 9A and 9B respectively display a cross-section through
a corrugated filter layer of a sand control screen having a
micro-perforated filter layer and an associated pattern of
micro-perforations in the filter layer;
[0030] FIGS. 10A and 10B display possible orientations of the
micro-perforations in the filter layer of a sand control screen
having a micro-perforated filter layer of the present invention;
and
[0031] FIG. 11 is a flowchart showing the manufacture of the sand
control screen having a micro-perforated filter layer of the
present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0032] While the making and using of various embodiments of the
present invention are discussed in detail below, it should be
appreciated that the present invention provides many applicable
inventive concepts which can be embodied in a wide variety of
specific contexts. The specific embodiments discussed herein are
merely illustrative of specific ways to make and use the invention,
and do not delimit the scope of the invention.
[0033] Referring now to FIG. 1, a sand control screen having a
micro-perforated filtration layer in use with an offshore oil and
gas production platform is schematically illustrated and generally
designated 10. A semi-submersible platform 12 is centered over a
submerged oil and gas formation 14 located below sea floor 16.
Wellhead 18 is located on deck 20 of platform 12. Well 22 extends
through the sea 24 and penetrates the various earth strata
including formation 14 to form wellbore 26. Disposed within
wellbore 26 is casing 28. Disposed within casing 28 and extending
from wellhead 18 is production tubing 30. A pair of seal assemblies
32, 34 provide a seal between tubing 30 and casing 28 to prevent
the flow of production fluids therebetween. During production,
formation fluids enter wellbore 26 through perforations of casing
28 and travel into tubing 30 to wellhead 18. As part of the final
bottom hole assembly, a sand control screen 38 having a
micro-perforated filtration layer is included in tubing 30. Sand
control screen 38 filters the particles out of the formation fluids
as the formation fluids are produced.
[0034] Even though FIG. 1 depicts a cased vertical well, it should
be noted by one skilled in the art that the sand control screen
having a micro-perforated filtration layer of the present invention
is equally well-suited for use in uncased wells, deviated wells or
horizontal wells. In fact, in certain well configurations, the sand
control screen having a micro-perforated filtration layer of the
present invention may be used in conjunction with expandable tubing
such that the tubing and the sand control screen are expandable
downhole after installation. Also, even through FIG. 1 depicts an
offshore operation, it should be noted by one skilled in the art
that the sand control screen having a micro-perforated filtration
layer of the present invention is equally well-suited for use in
onshore operations. In addition, even though a single sand control
screen is depicted, it should be noted by one skilled in the art
that any number of sand control screens of the present invention
may be coupled together to form one or more sand control screen
strings.
[0035] Referring to FIGS. 2-4, one embodiment of a sand control
screen having a micro-perforated filtration layer is depicted and
generally designated 40. Sand control screen 40 includes a base
pipe 42 that is depicted as having a plurality of openings 44 which
allow the flow of production fluids into the production tubing. One
skilled in the art will recognize that the number, size and shape
of openings 44 are not critical to the present invention, so long
as sufficient area is provided for fluid production and pipe
integrity is maintained. For example, the base pipe could have a
few as one opening. Alternatively, the base pipe could have a
plurality of micro-perforations similar to those described below.
Filter layer 50 is tightly attached to base pipe 42 and contains a
plurality of micro-perforations 52. The size, shape, density and
pattern of the micro-perforations 52 are determined by the desired
flow area, the desired filtration capacity, the constituents being
separated from one another and the like as well as the size of any
packing sand used in association with an installation of sand
control screen 40. In the illustrated embodiment, end caps 48 cover
the ends of filter layer 50. In certain embodiments, however, these
end caps 48 can optionally be omitted, as filter layer 50 may be
tightly fused to base pipe 42.
[0036] The typical opening sizes in existing sand screens, e.g.,
100-300 microns, can be reproduced in the micro-perforated filter
layer 50. Additionally, both larger and smaller opening sizes can
be provided in the disclosed micro-perforated filter layer 50
without the manufacturing difficulties encountered when these sizes
are manufactured in either wire wrap or wire mesh sand control
screens. A wide variety of intermediate size openings can also be
easily produced. Micro-perforated opening sizes for the disclosed
micro-perforated filter layer can range between 50 and 500 microns,
providing opening sizes that are not currently available from any
manufacturer.
[0037] Due to the manufacturing processes used to create filter
layer 50, the shape of micro-perforations 52 is precisely
controllable and reliably reproducible. In the illustrated
embodiment, micro-perforations 52 are depicted as circular,
however, micro-perforations 52 may also be formed in the shape of
an ellipse, a slot or other similar shape having a radius.
Alternatively, micro-perforations 52 may have sharp edges such as
squares, rectangles, triangles or other multi sided polygon or
shape.
[0038] Due to the tight tolerances available in the manufacturing
process used to create filter layer 50, the density and pattern of
micro-perforations 52 are precisely controllable and reliably
reproducible. For example, the opening density of
micro-perforations 52 may be between about 100 and 200 openings per
square inch. Opening densities both less than 100 openings per inch
and more than 200 openings per inch are also contemplated by the
present invention. The opening pattern of micro-perforations 52 can
have a uniform distribution or a nonuniform distribution. With the
infinitely variable opening size, shape, density and pattern in the
micro-perforated filter layer available with the present invention,
certain embodiments of the micro-perforated filter layer not only
allow for filtration of particles from production fluids but also
allow for separation of fluid constituents from one another. For
example, the micro-perforations may be configured to allow the
production of hydrocarbon fluids therethrough but prevent the
production of water therethrough. Likewise, the micro-perforations
may be configured to allow the production of liquid hydrocarbons
therethrough but prevent the production of hydrocarbon gases
therethrough.
[0039] As best seen in FIGS. 3A, 3B and 4, the surface of base pipe
42 is knurled or machined to create channels 46 that form a
drainage layer between base pipe 42 and filter layer 50 through
which production fluid can flow. FIG. 3A depicts a helical channel
pattern wherein channels 46 do not intersect. FIG. 3B depicts a
helical channel pattern wherein channels 46 intersect one another.
In FIG. 4, channels 46 are depicted as notches in the outer surface
of base pipe 42. Alternatively, the drainage layer of sand control
screen 40 could involve channels in the inner surface of filter
layer 50. As another alternative, the drainage layer of sand
control screen 40 could involve the use of a wire mesh or wire wrap
between base pipe 42 and filter layer 50.
[0040] Filter layer 50 is a surface-type filter, which removes
particles that are entrained in the production fluid at the surface
of the filter. Because the particles remain on the surface, filter
layer 50 is inherently easy to clean as particles can be washed
away by a back-flow of fluid. This ability contrasts with depth
filters, which trap the particles within the filter and are
inherently difficult or impossible to clean.
[0041] Referring now to FIGS. 5A-5B, an alternate embodiment of a
sand control screen having a micro-perforated filtration layer is
depicted in elevation and in cross-section respectively and
generally designated 140. Sand control screen 140 includes a base
pipe 142 that has a plurality of openings 144 which allow the flow
of production fluids into the production tubing. Filter layer 150
contains a plurality of micro-perforations 152. Filter layer 150 is
corrugated prior to attachment to base pipe 142. end caps 148
prevent fluids from entering base pipe 142 without passing through
filter layer 150 and provide an additional means of attachment. The
corrugations in filter layer 150 form large channels 146 between
filter layer 150 and base pipe 142 through which production fluid
flows to reach production tubing 30.
[0042] With reference now to FIG. 6, a further alternate embodiment
of a sand control screen having a micro-perforated filtration layer
is depicted in elevation and generally designated 240. Sand control
screen 240 includes base pipe 242 with a plurality of openings (not
shown) to allow the flow of production fluids into the production
tubing. Filter layer 250 contains micro-perforations 252. Filter
layer 250, like filter layer 150 of FIG. 5A, is corrugated prior to
attachment to base pipe 242. However, the corrugations of filter
layer 250 run circumferentially with respect to base pipe 242,
rather than longitudinally, as in filter layer 150. End caps 248
protect and seal the ends of filter layer 250 to base pipe 242. The
corrugations in filter layer 250 form large channels between filter
layer 250 and base pipe 242 through which production fluid flows to
reach production tubing 30.
[0043] When the micro-perforated filter layer is corrugated, the
placement of the micro-perforations can be varied as necessary or
desirable to prevent long term plugging of the filter and to
maintain the desired flow area. With reference now to FIGS. 7A-9B,
three embodiments of micro-perforations in a corrugated filter
layer are displayed. In these illustrations, only the filter layer,
such as filter layer 150 of FIG. 5, is shown. FIGS. 7A-7B contain
filter layer 300 having micro-perforations 302 shaped to form
slots. These slots 302 are created only in the peaks and valleys of
the corrugations. In order to promote bridging of sand particles
across slots 302, the width of the slots as measured across their
narrowest surface dimension is sized according to conditions in the
producing formation and the desired filtering characteristics. In
an alternate embodiment, shown in FIGS. 8A-8B, filter layer 310
contains micro-perforations 312 that form ellipses at the surface
of the filter layer. The ellipses 312 are formed in the sides of
the corrugations, but are eliminated from the peaks and valleys.
Removing the micro-perforations from the peaks may prevent plugging
while the sand control filter is installed. As in slots 302, the
width of ellipses 312 as measured across their narrowest surface
dimension is sized as dictated by the producing formation and the
desired filtering characteristics. A further alternate embodiment
is shown in FIGS. 9A-9B, which contain filter layer 320 having
micro-perforations 322 that form circles at the surface of the
filter layer. In this example, circles 322 are formed only on the
sides of the corrugations, but not in the peaks or valleys. The
diameter of the circle at the surface of the filter is sized
appropriately for the producing formation and the desired filtering
characteristics. One of ordinary skill in the art will understand
that these arrangements are exemplary and do not limit the shape or
distribution of the micro-perforations. In some embodiments, a
shroud may be placed to the exterior of the corrugated filter layer
to prevent damage during installation, but this is not necessary to
the operation of the sand control screen.
[0044] The use of a corrugated filter layer with the sand control
screen of the present invention provides certain advantages over
the non-corrugated embodiments. For example, the addition of
corrugations to the filter layer provides an increased flow area
over the non-corrugated version. Additionally, the corrugated
configuration reduces thermal effects relative to the bond between
the filter layer and the base pipe.
[0045] With reference now to FIGS. 10A-10B, in at least some
embodiments, the micro-perforations are formed using a water jet or
laser cutting process. When these methods are used, the
micro-perforations may have slightly tapering walls. For example,
when the surface shape is a circle, the micro-perforation may have
the shape of a truncated cone. Consequently, a slightly larger
opening is found on one side of the filter layer than on the other
side. If we consider the top of the figure to be the outside
surface of the filter layer, FIG. 10A shows micro-perforations 332
containing a larger opening to the outside of filter layer 330.
FIG. 10B shows micro-perforations 342 containing a smaller opening
to the outside of filter layer 340.
[0046] Referring now to FIG. 11, a method of making the sand screen
of the present invention will now be discussed. In step 400, a
section of base pipe is perforated to create openings. This step
can be performed by the same methods used to create openings for
wire wrap and wire mesh type sand control screens. In step 402, a
length of sheet metal is micro-perforated using any available
micro-perforation technique, such as water jetting or laser
cutting. The thickness of the sheet metal is preferably in the
range of 1/32nd inch to 1/4th inch, and preferably 3/16th inch
thick. The configuration of the micro-perforations for a given
installation can be determined based upon formation condition and
the desired filtering characteristics. In situations in which the
desired sizes and/or shapes for the micro-perforations are not
normally stocked, custom filter layers are feasible using the
disclosed method. The specifications for the filter layer can be
transmitted to a manufacturer of micro-perforated sheet metal for
implementation. As will be shown, once the filter layer is
micro-perforated, the actual assembly of the sand control screen is
not technically difficult.
[0047] Micro-perforating results in more reliably shaped and sized
openings than either wire wrapping or wire mesh screen methods,
while tolerances for spacing of openings can be more easily
controlled. Virtually infinitely variable screen ratings can be
provided by varying the size, shape, density and pattern of the
micro-perforations. Very small micron ratings can be produced by
micro-perforation without loss of strength in the filter material.
Similarly, large micron ratings formed by micro-perforation do not
require the manipulations of large gauge wire and can be produced
in sizes previously impossible to manufacture.
[0048] Once the sheet metal is micro-perforated to create the
filter layer, channels are provided in step 404 to allow fluid flow
between the filter layer and the base pipe. For corrugated
embodiments of the micro-perforated filter layer, the corrugations
of the filter layer are designed to form channels between the
filter layer and the base pipe when the filter layer and base pipe
are attached. For non-corrugated embodiments, channels are formed
in either the outer surface of the base pipe or in the surface that
will be the interior surface of the filter layer. In a preferred
embodiment, the base pipe is placed in a knurling machine and
knurls are created while the pipe is rotated, creating a spiral
pattern of channels down the length of the base pipe that will lie
under the filter layer. Cross-connections between adjacent channels
can also be formed to increase available cross-flow. FIGS. 3A-3B
have shown exemplary embodiments of knurling in the surface of the
base pipe. In still another embodiment, the base pipe is treated to
create an uneven, pebble-like surface. After the filter layer is
attached to the base pipe of this embodiment, the uneven surface
creates interconnected channels between the base pipe and the
filter layer.
[0049] The filter layer is shaped to fit around the base pipe in
step 406 and the filter layer and base pipe are attached to each
other in step 408. In one embodiment, the filter layer is fusion
bonded to the base pipe to form a direct metal-to-metal attachment.
In fusion bonding, the filter layer and the base pipe are placed in
close contact with each other. A high current is run through the
adjacent filter layer and base pipe, causing the two pieces to
fuse. With this technique, the filter layer can be attached to the
base pipe along the entire length of the filter layer, providing an
extremely strong attachment. End caps, if necessary or desired, can
be added as part of this step. Once the filter layer is attached to
the base pipe, the edges of the filter layer are sealed to each
other. In at least one embodiment, a seam weld is applied down the
full length of the filter layer, sealing the edges of the filter
layer together and forming a true one-piece, 360.degree.
filter.
[0050] In another embodiment of the attachment method, a friction
fit is used to join the filter layer to the base pipe. The filter
layer is first joined to itself to create an open-ended cylindrical
shape that is sized to fit snugly over the base pipe. The
cylindrical filter layer is then heated to increase the diameter
across the filter and slipped over the base pipe. When sized
properly, the cooled filter layer forms a tight fit to the base
pipe.
[0051] One of ordinary skill in the art will realize that other
methods of attachment can also be used without deviating from the
scope of the invention. For example, a glue or other bond-inducing
chemical means can be used. Additionally, a variety of connections,
such as threads, screws or welds provide another means of
attachment.
[0052] The disclosed method of manufacturing a sand control screen
provides a number of advantages over current manufacturing methods
for sand screens. The most critical step in the production of the
present sand control screen is micro-perforating the sheet metal.
This step can be performed under controlled conditions to produce
reliable opening sizes and shapes with close tolerances in the
spacing. The later steps of shaping the sheet metal and attaching
the shaped filter layer to the base pipe can be performed in less
controlled conditions without adversely affecting the quality of
the sand control screen. Final assembly can be performed closer to
the point of use, such as at the well site. Overhead can also be
reduced by stocking only the micro-perforated sheet metal and
assembling the sand control screens on user-provided base pipe.
Specific configurations of micro-perforations can be produced
quickly and shipped to the site to provide a custom-made filter
that more closely meets the need of the user's than the stock sizes
currently available.
[0053] The disclosed sand control screen having a micro-perforated
filter layer also provides additional advantages over existing sand
control screens. The use of a micro-perforated filter layer can
result in a sand control screen having a reduced outside diameter
for a given base pipe size. The decreased outside diameter and
strong attachment can make installation easier and may allow an
increased base pipe size for a given hole diameter. Additionally,
the attachment of the filter layer and base pipe along the entire
length of the filter layer provides a strong attachment with a
lower incidence of detachment. Manufacturing costs are decreased,
while the quality and durability of the filter are increased.
[0054] While this invention has been described with a reference to
illustrative embodiments, this description is not intended to be
construed in a limiting sense. Various modifications and
combinations of the illustrative embodiments as well as other
embodiments of the invention, will be apparent to persons skilled
in the art upon reference to the description. It is, therefore,
intended that the appended claims encompass any such modifications
or embodiments.
* * * * *