GB2555093A

GB2555093A - Rotatable sand screen

Info

Publication number: GB2555093A
Application number: GB1617336.1A
Authority: GB
Inventors: Nasvik Håvard
Original assignee: Statoil Petroleum ASA
Current assignee: Equinor Energy AS
Priority date: 2016-10-12
Filing date: 2016-10-12
Publication date: 2018-04-25
Anticipated expiration: 2036-10-12
Also published as: GB2555093B; GB201617336D0; NO20171628A1

Abstract

A sand screen assembly 10 for use on a base pipe 130 in a wellbore comprises a sand screen 100 configured to surround the base pipe 130, a plurality of support elements 110 extending in a longitudinal direction of the sand screen 100 and configured to provide a space between the sand screen 100 and the base pipe 130, wherein one or more of the plurality of support elements 130 is connected to the sand screen 100, and a shroud 120 surrounding the sand screen 100, wherein the shroud 120 is connected to the sand screen 100. The shroud 130 is shaped to have apertures which covered by raised sections of the shroud 130, and to be open facing in a circumferential direction, such that when the assembly 10 is rotated particulates such as sand will not enter the openings, but fluids will. The assembly may be included on a drill string to allow completion of the well with the same riser as the drill bit. Also disclosed is optimising the number of apertures present on the shroud, maximising strength while maintaining adequate fluid flow through the shroud.

Description

(54) Title of the Invention: Rotatable sand screen

Abstract Title: Sand screen assembly with protective shroud (57) A sand screen assembly 10 for use on a base pipe 130 in a wellbore comprises a sand screen 100 configured to surround the base pipe 130, a plurality of support elements 110 extending in a longitudinal direction of the sand screen 100 and configured to provide a space between the sand screen 100 and the base pipe 130, wherein one or more of the plurality of support elements 130 is connected to the sand screen 100, and a shroud 120 surrounding the sand screen 100, wherein the shroud 120 is connected to the sand screen 100. The shroud 130 is shaped to have apertures which covered by raised sections of the shroud 130, and to be open facing in a circumferential direction, such that when the assembly 10 is rotated particulates such as sand will not enter the openings, but fluids will. The assembly may be included on a drill string to allow completion of the well with the same riser as the drill bit. Also disclosed is optimising the number of apertures present on the shroud, maximising strength while maintaining adequate fluid flow through the shroud.

Figure 1

At least one drawing originally filed was informal and the print reproduced here is taken from a later filed formal copy.

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ROTATABLE SAND SCREEN

Technical Field

The present invention relates to well completion, and, in particular, a rotatable sand screen for use in drilling and/or completion in a wellbore.

Background

Sand screens are used in hydrocarbon wells (or water wells) to minimise the production of sand or other solid particulate matter along with the desired fluid. Such sand screens typically take the form of wire wrapping surrounding a base pipe through which fluid is produced to the surface. The sand screen prevents (or at least reduces) the passage of particles of solid matter into the base pipe, but allows the passage of fluids. The base pipe may contain flow ports, or one or more inflow control valves to permit the entry of fluids to the base pipe.

Summary

According to a first aspect of the present invention there is provided a sand screen assembly for use on a base pipe in a wellbore, comprising: a sand screen configured to surround the base pipe; a plurality of support elements extending in a longitudinal direction of the sand screen and configured to provide a space between the sand screen and the base pipe, wherein one or more of the plurality of support elements is connected to the sand screen at respective one or more first portions of the sand screen; and a shroud surrounding the sand screen, wherein the shroud is connected to the sand screen at one or more second portions of the sand screen.

The one or more second portions of the sand screen may be in the vicinity of the one or more first portions of the sand screen. The shroud, the sand screen and the support elements may be connected to each other along the same radius.

Each of the plurality of support elements may be connected to the sand screen.

The plurality of support elements may be configured to transmit a load from the sand screen to the base pipe.

Each of the plurality of support elements may be configured to be connected to the base pipe.

The sand screen may comprise a plurality of individual sand screen sections connected to each other. Each of the plurality of individual sand screen sections may be configured to be connected to the base pipe.

The shroud may comprise a flow port defining an aperture in the shroud. The flow port may comprise a portion of the shroud that protrudes radially outward relative to a main body of the shroud, wherein the portion of the shroud covers all or part of the aperture. The sand screen assembly may comprise a plurality of flow ports, wherein each of the plurality of flow ports is open facing a first, substantially circumferential direction, such that entry of solid material from the wellbore through the plurality of flow ports is prevented when the sand screen assembly is rotated in a direction opposite to the first direction. The shroud may comprise an optimised number of flow ports per unit of shroud surface area. The number of flow ports per unit of shroud surface area may be optimised based on a flow area of the base pipe and/or torque requirements for the sand screen assembly.

According to a second aspect of the present invention there is provided a method of completing a well, comprising: rotating a sand screen assembly while the sand screen assembly is moved into a wellbore, wherein the sand screen assembly comprises: a sand screen configured to surround the base pipe; a plurality of support elements extending in a longitudinal direction of the sand screen and configured to provide a space between the sand screen and the base pipe, wherein one or more of the plurality of support elements is connected to the sand screen at respective one or more first portions of the sand screen; and a shroud surrounding the sand screen, wherein the shroud is connected to the sand screen at one or more second portions of the sand screen.

The method may further comprise drilling the well with the sand screen assembly installed on a drill string.

The method may further comprise running a complete length of the sand screen assembly into the well in a single stage.

The sand screen assembly may be rotated in a single direction.

According to a third aspect of the present invention there is provided a shroud configured to surround a sand screen assembly installed on a base pipe in a wellbore, comprising: a plurality of flow ports, wherein the number of flow ports is optimised to maximise the strength of the shroud while permitting a sufficient rate of fluid flow through the shroud.

The number of flow ports may be determined based on a cross-sectional flow area of the base pipe, such that the flow area provided by the plurality of flow ports is at least equal to the cross-sectional flow area of the base pipe.

Brief Description of Drawings

Some embodiments of the invention will now be described by way of example only and with reference to the accompanying drawings, in which:

Figure 1 shows an end-on, cross-sectional view of a sand screen assembly installed for use on a base pipe;

Figure 2 shows side elevation cross-sectional views of sand screens comprising different numbers of sand screen sections installed on a base pipe;

Figure 3 shows a side elevation cross-sectional view of an end portion of a sand screen comprising multiple sand screen sections, installed for use on a base pipe; Figure 4 shows an end-on cross-sectional view of a sand screen assembly comprising a sand screen, ribs and shroud installed on a base pipe, showing a portion of the circumference of the sand screen assembly and base pipe; and Figure 5 shows a plan view of the surface of a shroud, showing exemplary configurations of flow ports.

Detailed Description

In use, a sand screen assembly typically comprises a sand screen and a shroud surrounding the sand screen. The sand screen is intended to allow the passage of a desired fluid (e.g., hydrocarbon fluid such as oil or gas in a hydrocarbon well, or water in a water well) through the sand screen to a base pipe, through which the desired fluid may be produced, and prevent (or at least mitigate) the ingress of solid materials. The shroud is intended to allow passage of the desired fluid while preventing damage to the sand screen, which can result from engagement with the wellbore during the process of working the sand screen assembly into the wellbore, or during completion. However, the inventors have realised that even with the protection provided by the shroud, sand screen assemblies often do not have sufficient mechanical strength to prevent damage to the shroud and/or sand screen.

In a sand screen assembly according to the invention a sand screen for use on a base pipe is separated from the base pipe by longitudinal ribs that are connected to the sand screen and may be connected to the base pipe. The portion or portions of the sand screen at the ribs are connected to the sand screen define respective loading portions of the sand screen. A load applied to the outside of the sand screen at such a loading portion is transmitted directly to the base pipe via the sand screen and the rib. The sand screen is fully supported by the rib and the base pipe. A shroud surrounding the sand screen is joined to the sand screen at one or more portions of the sand screen; the attachment of the shroud to the sand screen along its length provides greater strength under applied torques. The one or more portions at which the shroud is joined to the sand screen are preferably the one or more loading portions of the sand screen, and the shroud may be joined to the sand screen only at one or more loading portions of the sand screen. This means that a load applied to the shroud is transmitted to the sand screen at one or more load portions of the sand screen, i.e., at portions of the sand screen that are supported by the ribs and the base pipe. A load applied to the shroud is thus transmitted directly to the base pipe, via the sand screen and ribs, and failure of the sand screen assembly is mitigated.

The sand screen can be made up of multiple sand screen sections, each being connected, preferably by welding, to the base pipe. The provision of a greater number of points at which the sand screen is connected to the base pipe for a given length of base pipe increases the mechanical strength of the sand screen, both in terms of resistance to loads and resistance to torque.

The shroud comprises a plurality of flow ports allowing passage of fluid through the shroud to the sand screen. The flow ports are configured to prevent engagement of the shroud with a formation (or the inside of a wellbore in general), and to prevent the ingress of solid material from the wellbore into the space between the shroud and the sand screen, when the sand screen assembly is rotated in a wellbore. In particular, the flow ports are all orientated in the same, substantially circumferential direction, so that each of the flow ports is and closed facing in a first circumferential direction and open facing in the other, second circumferential direction. Each flow port comprises a portion of the shroud material that partially or completely covers an aperture defined by the flow port. This means that when the shroud is rotated in the first direction in a wellbore, engagement between the shroud and the wellbore is minimised, and the entrainment of solid material from the wellbore into the sand screen assembly is prevented. The flow ports in the shroud are preferably located between the ribs of the sand screen assembly.

The density of flow ports (i.e. the number of flow ports per unit of surface area of the shroud) can be optimised to maximise the strength of the sand screen assembly while maintaining a sufficient fluid flow.

Each of: the joining of the shroud to the sand screen at load portions of the sand screen; the provision of multiple sand screen sections in the sand screen; and the shape and configuration of the flow ports in the shroud, improves the performance of the sand screen assembly under rotation in a wellbore. Such rotation is beneficial, because rotation reduces the forces required to move the sand screen assembly into the wellbore. Standard sand screen assemblies typically do not have the strength to withstand rotation downhole, and are therefore either damaged when rotation is applied, or are installed without rotation, which means that the sand screen assembly is damaged by the increased forces required or cannot be moved to the required depth. The shape and orientation of the flow ports in the present sand screen assembly facilitate rotation downhole by preventing engagement of the sand screen assembly with the wellbore and preventing the ingress of solid material into the sand screen assembly; the increased resistance to loads and torsion provided by the integral connection of the shroud, sand screen and ribs, and the multiple sand screen sections increase the durability of the sand screen assembly under rotation downhole; and the optimised configuration of the flow ports in the shroud maintains a sufficient fluid flow while increasing the strength of the sand screen assembly.

Figure 1 shows an end-on, cross-sectional view of a sand screen assembly 10 installed for use on a base pipe 130. The sand screen assembly 10 comprises a sand screen 100, support elements 110 and a shroud 120.

The sand screen 100 is substantially cylindrical (tubular) in shape and surrounds the base pipe 130. The base pipe comprises one or more fluid ports and/or one or more inlet control valves. The sand screen 100 comprises wire wrapping that extends in a substantially circumferential direction, with a gap between each pair of adjacent wire wrapping elements, so that the wire wrapping forms a grid-like pattern (similar to a cattle grid). The gaps between the wire wrapping elements are sized to allow the passage of fluids and minimise the passage of solid materials. Each end of the sand screen is joined to, and in particular welded to, an end ring (not shown in Figure 1, shown in Figure 3 as 340). Each of the end rings is joined to, and in particular welded to, the base pipe 130 to join the sand screen 100 to the base pipe 130. In an alternative embodiment the end rings are joined to the base pipe by heat-shrinking the end rings onto the base pipe, or by using locking nuts, slips, or mechanical locks in conjunction with a recess in the base pipe. The different methods of joining the end rings to the base pipe may be used in combination for a single sand screen assembly. In one embodiment the whole sand screen assembly is heat-shrunk onto the base pipe and the end rings are welded onto the base pipe.

Each of the plurality of support elements 110, which will be referred to here as ribs 110, is an elongate element extending in a longitudinal direction relative to the sand screen 100, and the ribs 110 are located radially between the sand screen 100 and the base pipe 130. The cross-section of each rib 110 is triangular, with the point of the triangle contacting the sand screen 100 and the base of the triangle facing the base pipe 130. The ribs 110 and are joined to, and in particular welded to, the sand screen 100. Each area of the sand screen 100 at which a rib 110 is joined to the sand screen 100 defines a loading portion of the sand screen 100. As well as being joined to the sand screen 100 along its length, each of the plurality of ribs 110 is joined at each of its two ends, and in particular welded at each of its two ends, to an end ring (not shown in Figure 1, shown in Figure 3 as 340). The ribs 110 support the sand screen 100, provide a path for load transmission from the sand screen 100 to the base pipe 130, and separate the sand screen 100 from the base pipe 130 to provide space between the sand screen 100 and the base pipe 130. In one embodiment the ribs 110 and sand screen 100 are heat-shrunk onto the base pipe 130 to improve stability of the sand screen 100 on the base pipe 130.

In one embodiment the ribs 110 are joined, and in particular welded, to the base pipe 130. In this case the ribs 110 may be joined to the sand screen 100 first, and then joined (e.g., welded) to the base pipe 130 after the sand screen assembly 10 has been moved into position on the base pipe 130 (in fact, this will likely involve moving the elements of the sand screen assembly except for the shroud into position on the base pipe, joining the ribs to the base pipe, and then joining the shroud to the other elements of the sand screen assembly to form the complete sand screen assembly). Alternatively, the ribs are joined to the base pipe first, before the other elements of the sand screen assembly (i.e., the sand screen and shroud) are added to form the complete sand screen assembly on the pipe. In this case the ribs are pre-joined to end rings and this rib/end rings body is moved into position on the base pipe, and the ribs are then joined to the base pipe; alternatively, the ribs may be individually joined to the base pipe, and end rings then joined to the ribs. The sand screen (in particular, wire wrapping) is then joined to the ribs and the end rings, and the shroud is then added to form the complete sand screen assembly on the base pipe.

The shroud 120 is substantially cylindrical (tubular) in shape, and surrounds the sand screen 100. The shroud 120 is joined to, and in particular welded to, the sand screen 100. In particular, the shroud is joined to the sand screen at a plurality of the load portions of the sand screen 100. In particular, the shroud 120 is joined to the sand screen 100 at or near load portions of the sand screen 100. The shroud comprises one or more flow ports 150 configured to allow the passage of fluids and solids through the shroud 120 to the sand screen 100. Each flow port 150 defines an aperture in the shroud 120. The one or more flow ports 150 are located in the shroud 120, and the shroud 120 is aligned circumferentially around the sand screen 100, such that a minimum, and preferably none, of the apertures of the one or more flow ports 150 is located adjacent (in a radially outward direction) to a load portion of the sand screen

100. In other words, portions of the shroud 120 through which a load applied to the shroud 120 is transmitted to the sand screen 100 are adjacent (in a radially outward direction) to load portions of the sand screen 100.

In one embodiment the shroud 120 is joined, and in particular welded, at each of its two ends to the end rings. In particular, each end of the shroud is welded around its entire circumference to the end ring.

In use, the sand screen assembly 10 is installed on a base pipe 130 in a well. Shroud 120 protects sand screen 100 from damage while allowing passage of fluids and solids through flow ports 150 (not shown in figure 1). Sand screen 100 prevents the passage of solid materials but allows the passage of fluids through to the space between the sand screen 100 and the base pipe 130, where the size of the space between the sand screen 100 and base pipe 130 is determined by the radial dimension of ribs 110. The end rings provide longitudinal boundaries on the space defined in the radial direction by the base pipe 130 and the sand screen 100, and prevent flow of fluid around the sand screen 100. The fluid enters the base pipe 130 via one or more fluid ports or one or more inlet control valves, and the fluid is then removed to the surface via the base pipe. The configuration of the shroud 120 and the sand screen 100—in particular, the joining of the shroud 120 to the outside surface of the sand screen 100 at a plurality of points corresponding to (i.e., radially adjacent to) points on the inside surface of the sand screen 100 at which the sand screen 100 is joined to the ribs 110, and the location of the apertures of the flow ports 150 away from the portions of the sand screen 100 at which the sand screen 100 is joined to the ribs 110—means that the mechanical strength of the sand screen assembly is increased. In particular, the sand screen assembly’s resistance to failure under loads directly applied to the shroud 120 and/or torque is increased, because a load applied to the shroud 120 is transmitted to the sand screen 100 at portions of the sand screen 100 which are joined to ribs 110; the load is thus transmitted directly through the sand screen 100 and ribs 110 to the base pipe 130.

Figure 2 shows side elevation cross-sectional views of sand screens comprising different numbers of sand screen sections installed on a base pipe. Figure 2A shows an example of a typical sand screen of the prior art, in which a sand screen 200A comprising a single sand screen section 200A is installed for use on a base pipe 230A.

The sand screen 200A is welded to the base pipe 230A at two weld points 210A, 220A. Ribs (not shown) attached to the sand screen 200A may be heat shrunk onto the base pipe 230A to improve the stability of the sand screen 200A on the base pipe 230A. The base pipe 230A typically has a length of 10 m, and the sand screen 200A typically has a length of 6 to 8 m. The fact that the sand screen 200A is welded to the base pipe 230A at only two points that are separated by a relatively large length of 6 to 8 m means that the sand screen 200A may fail when rotated in hole, due to a lack of tolerance for applied torque, and may fail when run into hole without rotation, due to its poor structural integrity and mechanical strength.

Figure 2B shows a sand screen 250 installed for use on a base pipe 240. The sand screen 250 comprises three sand screen sections 251, 252, 253, each of which is welded to the base pipe 240. The sand screen 250 is welded to the base pipe 240 at four points 261,262, 263, 264 along its length. In this case for a sand screen 250 with a length of 8 m each sand screen section has a length of approximately 2.1 m.

Figure 2C shows a sand screen 270 installed for use on a base pipe 260. The sand screen 270 comprises nine sand screen sections 271-279, each of which is welded to the base pipe 260. The sand screen 270 is welded to the base pipe 260 at ten points 280-289 along its length. In this case for a sand screen 270 with a length of 8 m each sand screen section has a length of approximately 0.9 m.

Of course, other combinations of screen section lengths and numbers of screen sections are possible. Sand screen sections with different lengths can be used in the same sand screen. For example, longer sand screen sections may be used at end portions of the sand screen assembly or at portions of the sand screen assembly corresponding to an inlet into the base pipe, to facilitate fluid flow; and/or shorter sand screen sections may be used in portions of the sand screen assembly that will be subjected to greater torques.

The use of multiple sand screen sections in a sand screen (where the sand screen has a length similar to a typical sand screen, which comprises only one sand screen section), and in particular the welding of the sand screen to the base pipe at more points along its length, significantly increases the strength of the sand screen in use, and in particular when the sand screen is rotated in hole in a sand screen assembly.

With a sufficient number of points at which the sand screen is welded to the base pipe for a certain length of the sand screen, for example 10 points as shown in Figure 2C, the screen would be made durable enough for use in drilling unconsolidated sand reservoirs.

The configuration and assembly of a sand screen comprising multiple sand screen sections is set out in more detail with reference to Figure 3 and Figure 4.

Figure 3 shows a side elevation cross-sectional view of an end portion of a sand screen 300 installed for use on a base pipe 330. The sand screen 300 is configured to be surrounded by a shroud (not shown in Figure 3). Sand screen 300 comprises a plurality of sand screen sections 370, 380, 390 welded to each other. The end-most sand screen section 301 is welded to an end ring 340; the end ring 340 is itself welded to the base pipe 330. A corresponding end ring is located at the other end of the sand screen (not shown in Figure 3). Each of the sand screen sections 370, 380, 390 comprises a wire-wrapping grid and two ring-shaped end members 371,372, 381,382, 391; for example, sand screen section 370 comprises end members 371 and 372, and sand screen section 380 comprises end members 381 and 382. In Figure 3 the proportions of the end members relative to the sand screen sections are exaggerated. In practice the longitudinal width of each end member is approximately 4 to 8 mm, giving a joint width of 8 to 16 mm; these dimensions provide an acceptable added weight in the sand screen 300 (relative to a typical sand screen 200A as illustrated in Figure 2A). The size of the end members is determined according to expected loads. A plurality of ribs (not shown in Figure 3) are welded to the wire wrapping grid and the two end members of each sand screen section. The sand screen sections 370, 380, 390 overlap with each other to provide a secure structure in the sand screen 300. Each of the end members of the screen sections has an “L”-shaped cross-section (where the cross-section is cut along the longitudinal axis of the sand screen 300), and the “L’s” of adjacent pairs of end members (372, 381 and 382, 391) are 180° rotations (in the plane of the cross-section) relative to each other. Thus the end members of adjacent sand screen sections overlap to provide a joint between each pair of adjacent sand screen sections. The end member 371 of the sand screen section that is adjacent to the end ring 340 is a mirror image of end member 372, when reflected in a vertical axis, and fits into a corresponding recess in the end ring 340.

The screen sections are pre-made, and are then joined (in particular, welded) onto the base pipe 330 in sequence (with the end ring 340 and an end ring at the other end of sand screen 300), as follows: First, the end ring 340 is welded onto the base pipe 330 at weld 311. A first sand screen section 370 is then moved into place so that end member 371 is engaged with the corresponding recess in the end ring 340. The first sand screen section 370 is then welded to the end ring 340 at weld 312. The first sand screen section 370 is then welded to the base pipe 330 at weld 313. A second sand screen section 380 is then moved into place so that end member 381 of the second sand screen section 380 engages with end member 372 of the first sand screen section 370. The second sand screen section 380 is then welded to the first sand screen section 370 at weld 314. Then the second sand screen section 380 is welded to the base pipe at weld 315. For a sand screen comprising n sand screen sections, the process described for the second sand screen section (move into place, weld to adjacent sand screen section that has already been welded to base pipe, weld to base pipe) is repeated for each of the third up to n^,h sand screens. An end ring is then moved into place and welded to the n^,h sand screen, and subsequently welded or fastened to the base pipe.

In an embodiment in which the base pipe 330 has no fluid ports, and instead has one or more inflow control valves, each end member has a longitudinal hole to allow the longitudinal flow of fluids in the space between the sand screen 300 and the base pipe 330, such that fluids entering through a sand screen section distant from an inflow control valves can reach the inflow control valve. Of course, the longitudinal holes in adjacent pairs of end members 372, 381; 382, 391 line up to allow the passage of fluid.

In an embodiment in which the base pipe 330 has fluid ports (i.e., holes) allowing the passage of fluid into the base pipe from the space between the sand screen and the base pipe longitudinal holes in the end members are not required.

Figure 4 shows an end-on cross-sectional view of a sand screen assembly 40 comprising a sand screen 400, ribs 410 and shroud 420 installed on a base pipe 430, showing a portion of the circumference of the sand screen assembly 40 and base pipe 430. The configuration of the sand screen, ribs, shroud and base pipe is substantially as set out with reference to Figures 1 to 3. The shroud 420 comprises a plurality of flow ports 451,452, 453, 454, and is joined to the sand screen 400 at one or more points

421,422, 423, 424. Load portions of the sand screen 411, 412, 413, 414 are portions of the sand screen at which ribs 210 are joined to the sand screen 400. The points at which the shroud 420 is joined to the sand screen 400 substantially coincide with the load portions of the sand screen 400; that is, the points at which the shroud 420 is joined to the outside surface of the sand screen 400 are substantially radially adjacent to the points at which the ribs 410 are joined to the inside surface of the sand screen 400. Each of the flow ports defines an aperture in the shroud, and none of the apertures of the flow ports is radially adjacent to a load portion of the sand screen 400. This configuration of the flow ports in the shroud 420, and the relative configuration of the shroud 420, the sand screen 400 and the ribs 410 means that a load applied to the shroud 420 is transmitted directly to the base pipe 420 via the load portions of the sand screen 400 and the ribs 410. If, for example, the shroud 420 was rotated in a clockwise direction relative to the sand screen such that instead of being joined to the sand screen 400 at point 421, the shroud 420 was joined to the sand screen 400 at point 495, a load applied to the shroud 420 would be transmitted to the sand screen 400 at a point 495 at which the sand screen 400 is not supported by a rib 410; in this case mechanical failure of the sand assembly 40 is much more likely. The configuration of the sand screen assembly 40 avoids such a problem, and improves the mechanical strength of the sand screen assembly 40 under loads and torques applied to the shroud 420.

Figure 4 also shows the shape of the flow ports in the shroud 420. The flow ports can be made by removing material from the shroud 420 (by, for example, punching the material out of the shroud 420), or by deforming the material of the shroud 420, or by a combination of removing material and deforming the material of the shroud 420. Each of the flow ports comprises a portion 461 of the material of the shroud 420 that protrudes in a radially outward direction relative to a main body of the shroud (the shape of the main body of the shroud 120 is schematically illustrated in Figure 1), extending from a portion of the perimeter of each of the flow ports. The protruding portion 461 of the material of the shroud 420 covers part, or all, of the aperture defined by each of the flow ports. The orientation of each of the flow ports is the same; in particular, the orientation of the protruding portion of the material of the shroud 420 is the same for each of the flow ports. The protruding portion 461 of the material of the shroud extends in a circumferential direction at right angles to the longitudinal axis of the shroud 420, and is substantially symmetrical about a circumferential axis cut through the centre of the flow port 451. As a rough illustration, the shape of the flow ports might resemble the holes and grating elements in a cheese grater, or the buckets in a rotary bucket excavator.

The shape of the flow ports means that, in use in a wellbore, when the sand screen assembly 40 is rotated in a specified direction 485, engagement between the shroud 420 and the wellbore is prevented, and material from the wellbore is not gathered into the flow ports. The shroud 420 rotates freely in the open hole without engaging with the wellbore or the fill in an open hole. The screen assembly 40 is not aggressive to the wellbore and does not fill the flow ports or the space between the shroud 420 and the wire wrapping of the sand screen 400 with sand or other debris. The screen can then be ready for production without any remedial action required after the sand screen assembly 40 is installed in the wellbore. In Figure 4 the direction of rotation 485 is clockwise. Of course, the shroud could be configured to rotate in an anticlockwise direction.

Figure 5 shows a plan view of the outside surface of a shroud 520; in this view the surface is shown as if the shroud (which is typically cylindrical and tubular) has been sliced along the length of one side (in the longitudinal direction), opened out and laid flat, with the short edges of the rectangular outline of the surface representing the circumferential edges of the circular end openings of the shroud, and the long edges of the rectangular outline representing a line along the length of the shroud (in the longitudinal direction of the base pipe and/or the sand screen assembly).

The position of ribs 510 (which are not part of the shroud) relative to the shroud 520 is shown in this view; the ribs 510 extend in the longitudinal direction of the shroud (substantially parallel to the long edges of the rectangular outline of the surface). In this example the position of 20 ribs is shown. In reality the sand screen assembly of which the shroud forms part may comprise more, or fewer, ribs around its circumference.

The shroud 520 comprises flow ports e.g. 551,552, 561, 562, 571,572; in Figure 5 the position of the flow ports is denoted using “x”. As set out above for Figure 4, the flow ports are located between the ribs, to improve the mechanical strength and resilience of the sand screen assembly of which the shroud forms part. In one embodiment the flow ports have a shape and orientation as set out above for Figure 4.

In Figure 5 the shroud is divided into longitudinal zones A, B, C, D. The zones show examples of different flow port configurations, and in particular different flow port densities (i.e., different number of flow ports per unit surface area of the shroud). It is noted that Figure 5 does not show a specific embodiment in which the zones A, B, C and D are arranged as shown, covering the complete length and circumference of the shroud. Rather, zones A, B, C and D show individual examples of flow port density patterns that can each be repeated (or not, if not required) to cover the entire circumference of the shroud. The length shown in Figure 5 (in the direction of the long sides of the rectangular outline of the surface) may be only a portion of the length of the shroud, or the full length of the shroud; therefore, the shroud may comprise a portion along its length with the flow port density pattern shown in A, followed by another portion with the flow port density pattern shown in C, and so on. Zone A shows a high-density pattern of flow ports, zone B shows a medium-density pattern of flow ports, zone C shows a longitudinal zone with no flow ports (i.e., zero-density), and zone D shows a low-density pattern of flow ports. The flow port configurations in zones A, B and D are in decreasing order of flow capacity; that is, zone A (high-density pattern) has the highest flow capacity, zone B (medium-density pattern) has a lower flow capacity, and zone D (low-density pattern) has a yet lower flow capacity. Zone C has no flow ports (the lowest flow capacity); zone C maintains full torsional, compressional and tensional capacity, and aides in strengthening the shroud. In a portion of the length of the shroud containing a high-density pattern as shown in zone A, only the highdensity pattern will be present. The medium-density, low-density and zero-density patterns shown respectively in zones B, D and C can be mixed in any combination and quantity within a portion of the length of the shroud. The flow ports in each zone are arranged in repeating cluster patterns, which makes the manufacture of the flow ports in the shroud more efficient. For example, in zone A, the flow ports are arranged into large clusters 550; in zone B the flow ports are arranged into medium clusters 560; and in zone D the flow ports are arranged in small clusters 570.

As set out above in relation to Figure 4, the positioning of the flow ports in the shroud is optimised relative to the position of the ribs and the sand screen (by positioning the flow ports between the ribs) to increase the strength of the sand screen assembly of which the shroud forms part, and the shape and orientation of the flow ports is optimised to minimise engagement with a formation when the sand screen is used in a wellbore. The density of flow ports in the shroud (as set out above in relation to Figure 5 using the examples in zones A to D) is also optimised to maximise the strength of the shroud, and the sand screen assembly as a whole, while maintaining a sufficient fluid flow through the shroud. For example, zone A, which has a high flow rate configuration (-25% flow capacity relative to fully open), retains a significant portion of the strength of a shroud with no flow ports. In zones B and D, smaller clusters of flow ports are interleaved with blank spaces containing no flow ports, giving typically 10-15% flow capacity while retaining more of the strength of the shroud; this reduction of flow capacity with blank spaces gives the shroud significant added strength and a sufficient flow capacity. This improves upon existing technologies, in which the flow ports in the shroud are typically made using a simple steel sheet pressing machine; no account is taken of how many flow ports are needed, nor of positioning in relation to the sand screen or ribs, nor of the strength of the flow ports or interaction properties with the formation.

In existing technologies for the construction of screens on a base pipe the number of flow ports included in a shroud (and in the base pipe) is typically much greater than is required to maintain a sufficient flow rate, resulting in a weak shroud with a far larger flow capacity than is needed. In particular, the mechanical strength of the screen assembly is compromised, with reduced tension strength, collapse strength, and, significantly, torsional strength. For applications in which a sand screen assembly is rotated, either when it is run in hole for completion or for drilling, the torsional strength is preferably improved. The inventors have realised that the number of flow ports in the shroud can be reduced significantly to achieve improved torsional strength without any reduction in the production potential. The number of flow ports in the base pipe may also be reduced. When a fluid flow leaves the formation or a gravel pack and enters the sand screen assembly, the flow properties are mainly ruled by Newton flow, and the resistance to flow is much less than in the formation or gravel pack; the major factor limiting the flow is then the inside diameter of the completion base pipe, and no portion of the sand screen assembly needs to have a larger inflow area than the crosssectional flow area of the base pipe. In a base pipe with an inner diameter of, for example, 4.5 inches (-115 mm), the flow area corresponds to 80 holes with a diameter of 0.5 inches (-13 mm) in the base pipe; this number of holes, which allows maximum flow, is significantly lower than the 150-200 holes typically used in base pipes in existing technologies; this reasoning also applies to the number of flow ports in the shroud. The procedure for determining the minimum number of flow ports required in a shroud (such that the shroud is not the limiting factor restricting the flow of fluid from the wellbore to be produced) is therefore simple; the flow area provided by the flow ports in the shroud is preferably at least equal to the cross-sectional flow area of the base pipe (this reasoning also applies to holes in the base pipe). Considering that a completion typically comprises a larger number of sand screen assemblies (e.g., 10 or more in a horizontal well), the number of holes in the base pipe and the number of flow ports in the shroud can be reduced accordingly (given an even inflow in each sand screen assembly) without reducing the production potential of the well. The sand screen assembly then becomes viable for rotation during completion and drilling of soft formations. In a completion where the inflow is distributed over several sand screen assemblies, the number of flow ports in the shrouds and the base pipes could correspondingly be further reduced without limiting the production or injection capacity of the well.

The construction and configuration of the sand screen assembly described with reference to Figures 1 to 5 increases the mechanical strength of the sand screen assembly, increases its tolerance to torsional forces, prevents the engagement of the sand screen assembly with a wellbore in which it is installed, or being run into, prevents the entrainment of material from the wellbore into the flow ports of the shroud and the space between the shroud and the wire wrapping of the sand screen, and optimises the flow capacity of the sand screen assembly while maintaining increased strength. These advantages mean that the sand screen assembly can be rotated downhole, and can be used while drilling is being carried out. In particular, the shroud configuration with a large number of screen sections gives the screen the necessary strength for drilling easily drillable loose sand stone reservoirs.

In a method of completing a well, the sand screen assembly is rotated while being moved into the wellbore in a direction away from the surface, i.e., towards the end of the wellbore that is most distant from the surface along the length of the wellbore. The entire length of the sand screen assembly, or multiple sand screen assemblies, is installed in the wellbore in one stage of installation. In one embodiment the sand screen assembly is present while drilling is carried out in the well, and completion of the well is carried out without the need for a separate stage for the installation of the sand screen assembly.

In one embodiment in which the sand screen assembly is used in drilling operations, the sand screen assembly comprises a temporary solid material between the base pipe and the shroud, to protect from plugging by drilling fluids. Optionally, the solid material extends outside the perimeter between the base pipe and the shroud and also encloses the shroud. In this embodiment a base pipe without holes (in conjunction with an inlet control valve) is prefered. If the solid material is strong enough to resist the pumping pressure, a base pipe with holes can be used, otherwise an inner string for pumping the drilling fluids is required.

Although the invention has been described in terms of preferred embodiments as set forth above, it should be understood that these embodiments are illustrative only and that the claims are not limited to those embodiments. Those skilled in the art will be able to make modifications and alternatives in view of the disclosure which are contemplated as falling within the scope of the appended claims. Each feature disclosed or illustrated in the present specification may be incorporated in the invention, whether alone or in any appropriate combination with any other feature disclosed or illustrated herein.

Claims

CLAIMS:

1. A sand screen assembly for use on a base pipe in a wellbore, comprising: a sand screen configured to surround the base pipe;

a plurality of support elements extending in a longitudinal direction of the sand screen and configured to provide a space between the sand screen and the base pipe, wherein one or more of the plurality of support elements is connected to the sand screen at respective one or more first portions of the sand screen; and a shroud surrounding the sand screen, wherein the shroud is connected to the sand screen at one or more second portions of the sand screen.

2. The sand screen assembly of claim 1, wherein the one or more second portions of the sand screen are in the vicinity of the one or more first portions of the sand screen.

3. The sand screen assembly of claim 2, wherein the shroud, the sand screen and the support elements are connected to each other along the same radius.

4. The sand screen assembly of any one of the preceding claims, wherein each of the plurality of support elements is connected to the sand screen.

5. The sand screen assembly of any one of the preceding claims, wherein the plurality of support elements is configured to transmit a load from the sand screen to the base pipe.

6. The sand screen assembly of any one of the preceding claims, where each of the plurality of support elements is configured to be connected to the base pipe.

7. The sand screen assembly of any one of the preceding claims, wherein the sand screen comprises a plurality of individual sand screen sections connected to each other.

8. The sand screen assembly of claim 7, wherein each of the plurality of individual sand screen sections is configured to be connected to the base pipe.

9. The sand screen assembly of any one of the preceding claims, wherein the shroud comprises a flow port defining an aperture in the shroud,

10. The sand screen assembly of claim 9, wherein the flow port comprises a portion of the shroud that protrudes radially outward relative to a main body of the shroud, wherein the portion of the shroud covers all or part of the aperture.

11. The sand screen assembly of claim 9 or claim 10, comprising a plurality of flow ports, wherein each of the plurality of flow ports is open facing a first, substantially circumferential direction, such that entry of solid material from the wellbore through the plurality of flow ports is prevented when the sand screen assembly is rotated in a direction opposite to the first direction.

12. The sand screen assembly of any one of claims 9 to 11, wherein the shroud comprises an optimised number of flow ports per unit of shroud surface area.

13. The sand screen assembly of claim 12, wherein the number of flow ports per unit of shroud surface area is optimised based on a flow area of the base pipe and/or torque requirements for the sand screen assembly.

14. A method of completing a well, comprising:

rotating a sand screen assembly while the sand screen assembly is moved into a wellbore, wherein the sand screen assembly comprises: a sand screen configured to surround the base pipe;

15. The method of claim 14, comprising drilling the well with the sand screen assembly installed on a drill string.

16. The method of claim 14 or claim 15, comprising running a complete length of the sand screen assembly into the well in a single stage.

17. The method of any one of claims 14 to 16, wherein the sand screen assembly is 5 rotated in a single direction.

18. A shroud configured to surround a sand screen assembly installed on a base pipe in a wellbore, comprising:

a plurality of flow ports,

10 wherein the number of flow ports is optimised to maximise the strength of the shroud while permitting a sufficient rate of fluid flow through the shroud.

19. The shroud of claim 18, wherein the number of flow ports is determined based on a cross-sectional flow area of the base pipe, such that the flow area provided by the

15. The method of any one of claims 12 to 14, wherein the sand screen assembly is rotated in a single direction.

Intellectual

Property

Office

Application No: Claims searched:

GB1617336.1

1-17

15 plurality of flow ports is at least equal to the cross-sectional flow area of the base pipe.

Amendments to the Claims have been filed as follows:CLAIMS:

a plurality of support elements extending in a longitudinal direction of the sand screen and configured to provide a space between the sand screen and the base pipe, wherein one or more of the plurality of support elements is connected to the sand screen at respective one or more first portions of the sand screen; and a shroud surrounding the sand screen, wherein the shroud is connected to the sand screen at one or more second portions of the sand screen, wherein the sand screen comprises a plurality of individual sand screen sections connected to each other.

7. The sand screen assembly of any one of the preceding claims, wherein each of the plurality of individual sand screen sections is configured to be connected to the base pipe.

8. The sand screen assembly of any one of the preceding claims, wherein the shroud comprises a flow port defining an aperture in the shroud,

9. The sand screen assembly of claim 8, wherein the flow port comprises a portion of the shroud that protrudes radially outward relative to a main body of the shroud, wherein the portion of the shroud covers all or part of the aperture.

10. The sand screen assembly of claim 8 or claim 9, comprising a plurality of flow ports, wherein each of the plurality of flow ports is open facing a first, substantially circumferential direction, such that entry of solid material from the wellbore through the plurality of flow ports is prevented when the sand screen assembly is rotated in a direction opposite to the first direction.

11. The sand screen assembly of any one of claims 8 to 10, wherein the shroud comprises a minimum number of flow ports per unit of shroud surface area, wherein the minimum number of flow ports per unit of shroud surface area provides a flow area through the shroud that is equal to a cross-sectional flow area of the base pipe.

12. A method of completing a well, comprising:

13. The method of claim 12, comprising drilling the well with the sand screen assembly installed on a drill string.

14. The method of claim 12 or claim 13, comprising running a complete length of the sand screen assembly into the well in a single stage.