OA11211A

OA11211A - Expandable well screen

Info

Publication number: OA11211A
Application number: OA9900238A
Authority: OA
Inventors: Martin Donnelly
Original assignee: Shell Int Research
Priority date: 1997-04-28
Filing date: 1999-10-28
Publication date: 2003-07-18
Also published as: DK0980462T3; CA2284865A1; NZ337859A; EP0980462B1; RU2197600C2; DE69810610T2; MY119637A; AU7651798A; CA2284865C; DE69810610D1; AU717503B2; EP0980462A1; NO995248D0; ID22839A; NO317766B1; WO1998049423A1; UA57785C2; BR9809005A; NO995248L

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.

Description

1 011211

EXPANDABLE WELL SCREEN

The invention relates to an expandable well screenfor preventing migration of solid particles into ahydrocarbon fluid production well.

More particularly, the invention relates to anexpandable well screen which comprises a number of filtersheets which are secured in an iris-shaped configurationand co-axial to an expandable slotted carrier tube suchthat as a resuit of expansion of the tube the amount ofoverlap between adjacent filter sheets is reduced.

Such an expandable well screen is disclosed inapplicant's co-pending international patent applicationPCT/EP96/04887.

Figure 3 of this prior art reference discloses thatthe filter sheets consist of plates in which a sériés ofcircular perforations are présent. The size of theseperforations is chosen such that solid particles largerthan the size of the hole are prevented from flowing intothe well. A suitable expandable slotted carrier tube for usewith the screen is disclosed in international patentapplication PCT/EP93/01460.

It has been found that filter sheets which aresecured to an expandable slotted carrier tube .aredefôrmed considerably during the process of expanding thecarrier tube by moving an expansion mandrel therethrough.The carrier tube normally shortens during the expansionprocess as a resuit of opening of the axial slots towardsa diamond shape.

This may cause the filter sheets to buckle toaccommodate the carrier tube shortening and friction 2 011211 between the overlapping filter sheets and the carriertube or tubes may cause the filter sheets to tear.

An object of the présent invention is to provide awell screen comprising an iris-shaped configuration offilter sheets which do not buckle and which slide easilyrelative to each other and relative to the carrier tubeduring the process of expanding the carrier tube.

The well screen according to the invention theretocomprises filter sheets having slots which are orientedin a substantially circumferentiai orientation withrespect to the carrier tube.

When used in this spécification the reference to acircumferentiai arrangement of slots means that the slotseach are directed in a substantially tangential orientation with respect to the carrier tube and such theslots are oriented substantially transversal to thecentral axis and any axial slots of the carrier tube.

Preferably the filter sheets consist of elongatestrips with staggered rows of slots in a transversaldirection with respect to a longitudinal axis of eachstrip.

The pattern of slots is preferably such thatalternate rows are displaced up to half a slot pitch inthe transverse direction, the length of the slots isgreater than half the transverse slot pitch, and thepattern of slots is continued through the longitudinaledges of the strips.

It is also preferred that each strip is secured atrégula ri y spaced points along its length to theexpandable slotted carrier tube and that each strip issecured te the expandable slotted carrier tube at saidpoints by either spot welding, brazing, soldering,gluing, riveting or screwing the strip to the tube ateach of said points. 3 01 1 2 Ί 1

These and further aspects, features and advantages ofthe well screen according to the présent invention willbecome apparent from the accompanying daims, abstractand the following detailed description with reference to 5 the drawings.

In the drawings:

Fig. 1 is a cross-sectional view of a well-screencomprising an iris-shaped configuration of filter sheetsaccording to the invention; 10 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. 1and 2 in which the protective surrounding tube has beenomitted; and 15 Fig. 4 and Fig. 4A, B, C and D show the original shape and deformation of the circumferential slots near alongitudinal edge of the filter sheets before, during andafter the expansion process.

Referring now to Fig. 1 there is shown an expandable 20 slotted carrier tube 1 which is surrounded by a well screen 2 which comprises a sériés of filter sheets 3which are arranged in an iris-shaped configuration aroundthe carrier tube 1. As shown in Fig. 2 and 3 the filtersheets 3 consist of elongate rectangular strips which are 25 each, as shown in Fig. 1 secured to the carrier tube 1 at attachment points 4 located on or close to thelongitudinal centreline of the filter sheet 3 by forexample 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 thecarrier tube 1 .

The filter sheets 3 overlap each other in both axialand circumferential direction such that during and after 35 the expansion process which is illustrated in Fig. 4 at 4 011211 least some overlap remains between adjacent filtersheets 3.

In Fig. 3 the protective surrounding tube 5 which isshown in Figs. 1 and 2 has been omitted to show that thefilter sheets 3 each comprise a sériés of staggered rowsof circumferential slots 6 which are oriented in asubstantially tangential direction with respect to thecarrier tube 1 and substantially transversal to the axialslots 7 of the carrier tube 1 and to the central axis 8of the carrier tube 1.

As shown in Fig. 4 the carrier tube 1 is expanded byan expansion cône 9 during the expansion process suchthat the axial slots 7 deform into a diamond shape.

The expansion causes the carrier tube 1 to shortenand as illustrated in Figs. 4A-D the circumferentialslots 6 at and near the longitudinal edges of the filtersheets 3 will initially open up to the diamond shapeshown in Fig. 4B, then close to the X-shape shown inFig. 4C and then partly re-open again to the key-holeshape shown in Fig. 4D.

The illustrated sequential opening and closing of thecircumferential slots 6 provides axial flexibility to thefilter sheets 3 which prevents buckling or tearing of thefragile sheets 3 during expansion of the carrier tube 1.

The circumferential slots 6 also allow theoverlapping sheets 3 to slide easily relative to eachother during the expansion process.

It is observed that instead of arranging the filtersheets 3 in a longitudinal direction around the carriertube 1 as illustrated in Fig. 3, the filter sheets 3 mayalso be arranged in a shallow hélix around the carriertube 1. In such case the hélix angle should be selectedsmall enough so that the déviation of the slots 6 fromthe tangential direction of the carrier tube 1 is lessthan 20 degrees.

Claims

5 C L A I M S 01 121 1

1. An expandable well screen for preventing migration ofsolid particles into a hydrocarbon fluid production well,which screen comprises a number of filter sheets whichare secured in an iris-shaped configuration and co-axialto an expandable slotted carrier tube such that as aresuit of expansion of the tube the amount of overlapbetween adjacent filter sheets is reduced, wherein thefilter sheets comprise slots which are oriented in asubstantially circumferential orientation with respect tothe carrier tube.
2. The well screen of claim 1, wherein the filter sheetsconsist of elongate strips with staggered rows of slotsin a transversal direction with respect to a longitudinalaxis of each strip.
3. The well screen of claim 2, wherein the pattern ofslots is such that alternate rows are displaced up tohalf a slot pitch in the transverse direction, the lengthof the slots is greater than half the transverse slotpitch, and the pattern of slots is continued through thelongitudinal edges of the strips.
4. The well screen of claim 3, wherein each strip issecured at regularly spaced attachment points along itslength to the expandable slotted carrier tube.
5. The well screen of claim 4, wherein each strip issecured to the expandable slotted carrier tube at saidattachment points by either spot welding, brazing,solder!ng, gluing, riveting or screwing the strip to thetube at each of said points.
6. The well screen of claim 5, wherein the regularlyspaced attachment points are located on the nodes between 6 011211 the ends of the slots of the expandable slotted carriertube.
7. The well screen of claim 6, wherein the longitudinalaxis of each strip is substantially parallel to a central 5 axis of the carrier tube both before and after expansion of the carrier tube.