EXPANDABLE WELL SCREEN

FILTRE EXPANSIF DESTINE A UN PUITS

English Abstract

An expandable well screen for preventing migration of sand or other solid
particles into a hydrocarbon fluid production well comprises
a number of filter sheets (3) with circumferential slots (6), which sheets (3)
are secured in an iris-shaped configuration and co-axial to an
expandable slotted carrier tube (1) such that as result of expansion of the
tube (1) the amount of overlap between adjacent filter sheets (3)
is reduced. The circumferential slot pattern of the slots (6) enables the
filter sheets (3) to slide easily relative to each other and to avoid
buckling and/or tearing of the filler sheets during the expansion process.

French Abstract

Ce filtre expansif, destiné à un puits et servant à empêcher la migration de sable ou autres particules solides dans un puits de production d'un fluide hydrocarbure, comprend un certain nombre de feuilles filtrantes (3), lesquelles sont pourvues de fentes périphériques (6), sont fixées selon un agencement en forme d'iris et sont coaxiales avec un tube porteur (1) fendu et expansif, de façon que par suite de l'expansion du tube (1), l'importance du chevauchement entre les feuilles filtrantes adjacentes (3) soit diminué. Le motif de fente périphérique des fentes (6) permet aux feuilles filtrantes (3) de coulisser relativement facilement l'une par rapport à l'autre et d'éviter que ces feuilles ne se gondolent et/ou ne se déchirent pendant le processus d'expansion.

Claims

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CLAIMS
1. An expandable well screen for preventing migration of
solid particles into a hydrocarbon fluid production well,
which screen comprises a number of filter sheets which
are secured in an iris-shaped configuration and co-axial
to an expandable slotted carrier tube such that as a
result of expansion of the tube the amount of overlap
between adjacent filter sheets is reduced, wherein the
filter sheets comprise slots which are oriented in a
substantially circumferential orientation with respect to
the carrier tube.
2. The well screen of claim 1, wherein the filter sheets
consist of elongate strips with staggered rows of slots
in a transversal direction with respect to a longitudinal
axis of each strip.
3. The well screen of claim 2, wherein the pattern of
slots is such that alternate rows are displaced up to
half a slot pitch in the transverse direction, the length
of the slots is greater than half the transverse slot
pitch, and the pattern of slots is continued through the
longitudinal edges of the strips.
4. The well screen of claim 3, wherein each strip is
secured at regularly spaced attachment points along its
length to the expandable slotted carrier tube.
5. The well screen of claim 4, wherein each strip is
secured to the expandable slotted carrier tube at said
attachment points by either spot welding, brazing,
soldering, gluing, riveting or screwing the strip to the
tube at each of said points.
6. The well screen of claim 5, wherein the regularly
spaced attachment points are located on the nodes between

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the ends of the slots of the expandable slotted carrier
tube.
7. The well screen of claim 6, wherein the longitudinal
axis of each strip is substantially parallel to a central
axis of the carrier tube both before and after expansion
of the carrier tube.

Description

CA 02284865 1999-09-24
WO 98/49423 PCT/EP98/02577
EXPANDABLE WELL SCREEN
The invention relates to an expandable well screen
for preventing migration of solid particles into a
hydrocarbon fluid production well.
More particularly, the invention relates to an
expandable well screen which comprises a number of filter
sheets which are secured in an iris-shaped configuration
and co-axial to an expandable slotted carrier tube such
that as a result of expansion of the tube the amount of
overlap between adjacent filter sheets is reduced.
Such an expandable well screen is disclosed in
applicant's co-pending international patent application
PCT/EP96/04887.
Figure 3 of this prior art reference discloses that
the filter sheets consist of plates in which a series of
circular perforations are present. The size of these
perforations is chosen such that solid particles larger
than the size of the hole are prevented from flowing into
the well.
A suitable expandable slotted carrier tube for use
with the screen is disclosed in international patent
application PCT/EP93/01460.
It has been found that filter sheets which are
secured to an expandable slotted carrier tube are
deformed considerably during the process of expanding the
carrier tube by moving an expansion mandrel therethrough.
The carrier tube normally shortens during the expansion
process as a result of opening of the axial slots towards
a diamond shape.
This may cause the filter sheets to buckle to
accommodate the carrier tube shortening and friction

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between the overlapping filter sheets and the carrier
tube or tubes may cause the filter sheets to tear.
An object of the present invention is to provide a
well screen comprising an iris-shaped configuration of
filter sheets which do not buckle and which slide easily
relative to each other and relative to the carrier tube
during the process of expanding the carrier tube.
The well screen according to the invention thereto
comprises filter sheets having slots which are oriented
in a substantially circumferential orientation with
respect to the carrier tube.
When.used in this specification the reference to a
circumferential arrangement of slots means that the slots
each are directed in a substantially tangential
orientation with respect to the carrier tube and such the
slots are oriented substantially transversal to the
central axis and any axial slots of the carrier tube.
Preferably the filter sheets consist of elongate
strips with staggered rows of slots in a transversal
direction with respect to a longitudinal axis of each
strip.
The pattern of slots is preferably such that
alternate rows are displaced up to half a slot pitch in
the transverse direction, the length of the slots is
greater than half the transverse slot pitch, and the
pattern of slots is continued through the longitudinal
edges of the strips.
It is also preferred that each strip is secured at
regularly spaced points along its length to the
expandable slotted carrier tube and that each strip is
secured to the expandable slotted carrier tube at said
points by either spot welding, brazing, soldering,
gluing, riveting or screwing the strip to the tube at
each of said points.

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These and further aspects, features and advantages of-
the well screen according to the present invention will
become apparent from the accompanying claims, abstract
and the following-detailed description with reference to
the drawings.
In the drawings:
Fig. 1 is a cross-sectional view of a well-screen
comprising an iris-shaped configuration of filter sheets
according to the invention;
Fig. 2 is a longitudinal sectional view of the well
screen of Fig. 1;
Fig. 3 is a side view of the well screen of Fig. 1
and 2 in which the protective surrounding tube has been
omitted; and
Fig. 4 and Fig. 4A, B, C and D show the original
shape and deformation of the circumferential slots near a
longitudinal edge of the filter sheets before, during and
after the expansion process.
Referring now to Fig. 1 there is shown an expandable
slotted carrier tube 1 which is surrounded by a well
screen 2 which comprises a series of filter sheets 3
which are arranged in an iris-shaped configuration around
the carrier tube 1. As shown in Fig. 2 and 3 the filter
sheets 3 consist of elongate rectangular strips which are
each, as shown in Fig. 1 secured to the carrier tube 1 at
attachment points 4 located on or close to the
longitudinal centreline of the filter sheet 3 by for
example spot welding, brazing, soldering, gluing,
riveting or screwing at regularly spaced points along the
. 30 length of the carrier tube 1. The attachment points are
located on the nodes between the ends of the slots of the
carrier tube 1.
The filter sheets 3 overlap each other in both axial
and circumferential direction such that during and after
the expansion process which is illustrated in Fig. 4 at

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least some overlap remains between adjacent filter
sheets 3.
In Fig. 3 the protective surrounding tube 5 which is
shown in Figs. 1 and 2 has been omitted to show that the
filter sheets 3 each comprise a series of staggered rows
of circumferential slots 6 which are oriented in a
substantially tangential direction with respect to the
carrier tube 1 and substantially transversal to the axial
slots 7 of the carrier tube 1 and to the central axis 8
of the carrier tube 1.
As shown in Fig. 4 the carrier tube 1 is expanded by
an expansion cone 9 during the expansion process such
that the axial slots 7 deform into a diamond shape.
The expansion causes the carrier tube 1 to shorten
and as illustrated in Figs. 4A-D the circumferential
slots 6 at and near the longitudinal edges of the filter
sheets 3 will initially open up to the diamond shape
shown in Fig. 4B, then close to the X-shape shown in
Fig. 4C and then partly re-open again to the key-hole
shape shown in Fig. 4D.
The illustrated sequential opening and closing of the
circumferential slots 6 provides axial flexibility to the
filter sheets 3 which prevents buckling or tearing of the
fragile sheets 3 during expansion of the carrier tube 2.
The circumferential slots 6 also allow the
overlapping sheets 3 to slide easily relative to each
other during the expansion process.
It is observed that instead of arranging the filter
sheets 3 in a longitudinal direction around the carrier
tube 1 as illustrated in Fig. 3, the filter sheets 3 may
also be arranged in a shallow helix around the carrier
tube 1. In such case the helix angle should be selected
small enough so that the deviation of the slots 6 from
the tangential direction of the carrier tube 1 is less
than 20 degrees.
r , _ _ . _..... _.. . ,~ ..

Representative Drawing