Hydrocarbon wells, especially those having horizontal wellbores, typically have sections of wellscreen comprising a perforated inner tube surrounded by a screen portion. The purpose of the screen is to block the flow of unwanted materials into the wellbore. Despite the wellscreen, some contaminants and other unwanted materials like sand, still enter the production tubing. The contaminants occur naturally and are also formed as part of the drilling process. As production fluids are recovered, the contaminants are also pumped out of the wellbore and retrieved at the surface of the well. By controlling and reducing the amount of contaminants that are pumped up to the surface, the production costs and valuable time associated with operating a hydrocarbon well will likewise be reduced.

One method of reducing the inflow of unwanted contaminants is through gravel packing. Normally, gravel packing involves the placement of gravel in an annular area formed between the screen portion of the wellscreen and the wellbore. In a gravel packing operation, a slurry of liquid, sand and gravel ("slurry") is pumped down the wellbore where it is redirected into the annular area with a cross-over tool. As the gravel fills the annulus, it becomes tightly packed and acts as an additional filtering layer along with the wellscreen to prevent collapse of the wellbore and to prevent the contaminants from entering the streams of production fluids pumped to the surface.

Ideally, the gravel will be uniformly packed around the entire length of the wellscreen, completely filling the annulus. However, during gravel packing, the slurry may become less viscous due to loss of fluid into the surrounding formations or into the wellscreen.

The loss of fluid causes sand bridges to form. Sand bridges are a wall bridging the annulus and interrupting the flow of the slurry, thereby preventing the annulus from completely filling with gravel.

The problem of sand bridges is illustrated in Figure 1, which is a side view, partially in section, of a horizontal wellbore with a wellscreen therein. The wellscreen 30 is positioned in the wellbore 14 adjacent a hydrocarbon bearing formation therearound. An annulus 16 is formed between the wellscreen 30 and the wellbore 14.

The Figure illustrates the path of gravel 13 as it is pumped down the production tubing 11 in a slurry and into the annulus 16 through a crossover tool 33.

Also illustrated in Figure 1 is a formation including an area of highly permeable material 15. The highly permeable area 15 can draw liquid from the slurry, thereby dehydrating the slurry. As the slurry dehydrates in the permeable area 15 of formation, the remaining solid particles form a sand bridge 20 and prevent further filling of the annulus 16 with gravel. As a result of the sand bridge, particles entering the wellbore from the formation are more likely to enter the production string and travel to the surface of the well. The particles may also travel at a high velocity, and are therefore more likely to damage and abrade the wellscreen components.

In response to the sand-bridging problem, shunt tubes have been developed creating an alternative path for gravel around a sand bridge. According to this conventional solution, when a slurry of sand encounters a sand bridge, the slurry enters an apparatus and travels in a tube, thereby bypassing the sand bridge to re-enter the annulus downstream. The shunt tubes may be placed on the outside of the apparatus or run along the interior thereof. However, there are problems associated with both designs. For example, by being outside of the apparatus, the shunt tubes are susceptible to breakage or deformation during construction or placement of the wellscreen in the wellbore. Additionally, since the shunt tubes are on the outside, the overall diameter of the production apparatus is increased, thereby decreasing the diameter of the annulus, and decreasing the filtering capabilities of packed gravel.

Shunt tubes located inside an apparatus are limited in their internal diameter and are generally constructed with little cross-sectional volume. Shunt tube-type devices also typically provide one location for slurry to enter and one location for slurry to exit.

The entry and exit apertures cannot be easily relocated or adjusted for conditions of

formations downhole because they are pre-manufactured. For example, when a sand bridge is by-passed using one of these conventional designs, the slurry re-enters the annulus where the shunt tube exits the apparatus. As a result, the slurry may re-enter the annulus adjacent the same highly permeable, formation causing the liquid portion of the slurry to be lost into the formation and more sand bridges to be formed as a result of the increased viscosity of the slurry There is a need therefore, for a wellscreen having an alternative pathway for injected material to by-pass sand bridges or other obstructions in a wellbore. There is a further need for a wellscreen that diverts the flow of a gravel slurry to the interior of the wellscreen and, thereafter, redirects the slurry to the exterior of the screen at a predetermined location along the wellbore. There is yet a further need for a wellscreen that controls the re-entry of the slurry by decreasing, increasing or closing apertures formed in a wall of the wellscreen. There is a further need for a wellscreen for use with gravel packing operations that provides a bypass for slurry wherein the bypass provides a channel of greater volume than prior art devices. There is yet a further need for a wellscreen for use with a gravel packing operation wherein the openings of apertures are resistant to erosion by high velocity particles.

The present invention generally provides for an apparatus for use in a wellbore having an alternative pathway for a slurry to by-pass an obstruction such as a sand bridge during gravel packing.

In accordance with a first aspect of the present invention there is provided an apparatus for redirecting a slurry containing particulate matter, comprising: a wellscreen, said wellscreen comprising: a perforated base pipe; a wire wrap disposed around said perforated base pipe ; an annular space formed between said wire wrap and said perforated base pipe; at least one aperture at a first longitudinal position in said wellscreen providing fluid communication between an exterior of said wire wrap and said annular space; and at least one aperture at a second longitudinal position in said wellscreen providing fluid communication between the exterior of said first wire wrap and said

annular space.

Further preferred features are set out in claims 2 et seq.

In accordance with a second aspect of the present invention there is provided an apparatus for redirecting a slurry of sand, comprising: a wellscreen, said wellscreen comprising: a perforated base pipe; a first wire wrap disposed around said perforated base pipe; a first annular space formed between said perforated base pipe and said first wire wrap; a second wire wrap disposed around said first wire wrap; a second annular space formed between said first and said second wire wraps; at least one aperture at a first longitudinal position in said wellscreen providing fluid communication between an exterior of said second wire wrap and said second annular space; and at least one aperture at a second longitudinal position in said wellscreen providing fluid communication between the exterior of said second wire wrap and said second annular space.

In accordance with a third aspect of the present invention there is provided a method of using a wellscreen in a wellbore, comprising the steps of : collecting information relating to conditions of a formation around the wellscreen; analysing the information; and adjusting apertures formed in the wellscreen in response to the conditions.

Thus in preferred embodiments of the invention, an apparatus includes a perforated base pipe, a wire wrap around the perforated base pipe and an annular space therebetween providing an alternative pathway for a slurry to by-pass a sand bridge. At least one aperture is formed through the wire wrap to provide a path for slurry into the apparatus and at east one aperture is formed through the wire wrap to provide a path back out of the apparatus. In one embodiment, an apparatus additionally includes a

second wire wrap around the first wire wrap and forming a second annular space in the apparatus to provide an alternative pathway for a slurry to by-pass a sand bridge.

In one embodiment, the invention provides a method to control and predetermine the optimal exit point for the slurry to re-enter the annulus from the alternative pathway of the apparatus. The method comprises collecting information such as geological surveys and tests of the wellbore to determine the type of formations that would be encountered down hole during production; analysing the information; adjusting the size and/or plugging up the apertures of the screen with inserts based upon the collected information, and adding protective inserts to the apertures if highly abrasive particles are present in the wellbore. In another embodiment of the invention, the apparatus does not include a base-pipe but only two tubular-shaped wire wraps with an annular space formed therebetween.

Some preferred embodiments of the invention will now be described by way of example only and with reference to the accompanying drawings, in which: Figure 1 is a side view, partially in section, of a horizontal wellbore with a wellscreen therein; Figure 2 is a side view of an apparatus in accordance with the present invention disposed in a wellbore; Figure 3 is a cross-sectional view of the apparatus of Figure 2 taken along line 3- 3 of Figure 2; Figure 4 is a side view of an embodiment of the present invention disposed in a wellbore; and Figure 5 is a cross-sectional view of an embodiment of the invention taken along line 5-5 of Figure 4.

Figure 2 is a section view of an apparatus 100 according to the present invention disposed in a wellbore 14 and Figure 3 is a cross-sectional view of the apparatus 100 taken along line 3-3 of Figure 2. Although apparatus 100 is shown in a horizontal wellbore, the present invention can be utilised in any wellbore. In Figure 2, the apparatus 100 is shown having collars 41 disposed between sequential sections of wellscreen 30. In this manner, the apparatus can be made up to any length by threading sections of wellscreen 30 together using collars 41 therebetween.

Wellscreen 30 includes a base pipe 31 having perforations 19 through the wall thereof. While the base pipe is perforated in the Figures shown, the base pipe may be slotted or include perforations of any shape so long as the perforations permit the passage of production fluid but inhibit the passage of particles. A first set of spacers 38, visible in Figure 3, separate the perforated base pipe 31 from a first wire wrap 32 to create a first annular space 35 between the base pipe 31 and the first wire wrap 32. A second set of spacers 47 separate the first wire wrap 32 from a second wire wrap 39 to create a second annular space 36 therebetween. Additionally, the invention may be practised without a base pipe so long as the wire wraps are arranged to provide an annular area therebetween and are resistant to collapse. The first and second wire wraps 32,39 each may be made up of coil wires extending circumferentially around the base pipe 31. In the embodiment shown, the wire wraps are slightly spaced apart by spacers 38,47 to permit production fluid to pass into the perforated base pipe 31, but also to prevent particles from entering the base pipe. In the embodiment of Figures 2 and 3, the second annular space 36 forms an alternative pathway through the apparatus. More specifically, the purpose of annulus 36 is to provide an alternative pathway for slurry through the apparatus when the annulus 16 between the apparatus 100 and the wellbore 14 is blocked by a sand bridge 20.

When the flow of slurry in annulus 16 is blocked by the presence of a sand bridge, the slurry enters the second annular space 36 through an entry aperture 34 formed in the wall of the wellscreen or, as illustrated in Figure 2, formed in a collar 41.

Second annular space 36 allows the slurry to by-pass the sand bridge 20 and the flow path through annular space 36 is illustrated with arrows 40.

Figure 2 also illustrates a feature of the invention designed to ensure that the re- entry of the slurry into the wellbore occurs at an optimal location in the wellbore. In Figure 2 for example the aperture 48 adjacent entry aperture 34 is also surrounded by highly permeable formation 15. In order to prevent the slurry from re-entering the annulus 16 in this continued area of high permeability, aperture 48 has a reduced inner diameter. In the preferred embodiment, the inner diameter of the aperture 48 is reduced with an insert 43 in order to discourage the flow of slurry back into the annulus 16 via aperture 48. Instead, the flow of slurry is encouraged to continue to the next aperture 49 as illustrated by arrows 40. Aperture 49 is constructed and arranged with a larger inner diameter. Consequently, as the flow of slurry reaches the next aperture 49, the slurry will re-enter the annulus 16 where the formation of a gravel pack in the annulus will continue. By utilising other apparatus 100 in the string of wellbore, additional sand bridges can be avoided in a similar manner. Since the alternative pathway provided by the second annular space 36 is larger than conventional shunt tubes, the apparatus 100 is able to carry more slurry at a faster rate to form a gravel pack more rapidly.

While Figures 2 and 3 show one embodiment of the invention, the invention may also be practised in alternative embodiments such as the one shown in Figure 4.

Figure 4 is a side view of an apparatus 200 of the present invention disposed in a wellbore and Figure 5 is a cross-sectional view of the apparatus taken along line 5-5 of Figure 4. The apparatus 200 has a perforated base pipe 31 with perforations 19, a first wire wrap 32 disposed directly around the base pipe 31 with no annular space therebetween, and a second wire wrap 39 disposed around the first wire wrap 32, and separated therefrom by a first set of spacers 38 (Figure 5) to form an annular space 35.

In this embodiment, annular space 35 forms an alternative pathway for slurry to travel in the apparatus. Another alternative embodiment includes a perforated base pipe 31 that is slotted or manufactured with openings that act to filter particles. A wire wrap 32 disposed around the perforated base pipe 31 and separated by first set of spacers 38 to form an annular space 35 for the alternative pathway.

A method of utilising the current invention will now be described. Initially, information about the formations surrounding the wellbore is collected. The

information is then analysed to determine the optimal entry and exit locations for slurry.

The apparatus arrives at the well site with numerous apertures 34 prefabricated therein.

Inserts 43 having various inner diameters are also supplied. The inserts 43 are manufactured from erosion resistant materials such as tungsten carbide or ceramic and made to fit the apertures 34. Before the wellscreen 30 is inserted into the wellbore, the apertures are pre-sized using inserts to determine the optimum entry and exist points for the slurry based upon the location of highly permeable portions of formations surrounding the wellbore. If permeable formations exist, apertures 34 are sized by placing inserts 43 to decrease the diameter of the aperture so as to limit the amount of slurry re-entering the annulus 16. The apertures 34 can also receive inserts that are blocked, thereby completely sealing the aperture to the flow of material therethrough.

Further, if an abrasive sand packing procedure will be utilised or if the particles encountered will be highly abrasive, erosion resistant inserts 43 are added to minimise the erosion of the apertures 34. The erosive resistant inserts 43 may be made of materials such as ceramic or tungsten carbide. The embodiment allows for more accurate control of when, where and how much of the slurry re-enters the annulus 16 from the alternative pathway.

It will be appreciated that departures from the above described embodiments may still fall within the scope of the invention. For example, the apparatus can be used in any wellbore where a portion of the wellbore is to be by-passed by a slurry of particulate matter. One example includes a water-bearing formation located between two hydrocarbon-bearing formations along a wellbore. By utilising the apparatus according to the invention, the water-bearing formation can be isolated and by-passed by a slurry of gravel.