CN1973111A - Screen for controlling sand production in a wellbore - Google Patents

Abstract

A wellbore screen (1) is provided for controlling inflow of solid particles into a wellbore (2). The wellbore screen comprises a conduit (3) for transporting fluid, an outer layer (4) comprising a filter for reducing inflow of solid particles into the conduit (3), the outer layer extending around the conduit and being radially expandable against the wellbore wall, and swelling means arranged between the conduit and the outer layer. The swelling means (6) is susceptible of swelling upon contact with a selected fluid so as to radially expand the outer layer against the wellbore wall.

Description

Screens to control sand production in the wellbore

technical field

The present invention relates to a wellbore screen for controlling the flow of solid particles into a wellbore, the screen comprising a conduit for conveying fluid, and an outer layer for filtering solid particles from the fluid flowing into the conduit.

Background of the invention

A separate sand removal system, such as a slotted liner or a wire-wound screen, is typically applied in a well producing fluid from a formation or in a well injecting fluid into the formation. The production and/or injection fluid streams may be, for example, oil, gas or water. A problem that often arises in the use of such sand removal systems involves the axial flow of fluid in the annulus between the wellbore wall and the screen. Solid particles from the surrounding formation that flow into the wellbore with the fluid flow can thus migrate along the screen and deposit on the screen as a deposit with very low permeability. The problem described refers in particular to the case of clay particles entering the wellbore. As a result of such fluid flow through the annulus, the screen may become clogged for the entire length of the screen, which can result in reduced production of hydrocarbon fluids or water from the well. In addition, excessive corrosion of the screen may result if the flow of fluid into the screen is reduced to localized areas of the screen that are not yet clogged.

It is an object of the present invention to provide an improved screen which overcomes the aforementioned problems.

Contents of the invention

According to the present invention, there is provided a wellbore screen for controlling the flow of solid particles into a wellbore, the wellbore screen comprising: a conduit for conveying fluid; an outer layer for reducing the amount of solid particles flowing into the conduit, the said outer layer extends around said conduit and is radially expandable against the well wall; and an expansion device disposed between the conduit and the outer layer readily expands upon contact with a selected fluid so that the outer layer Swell against the well wall.

It is obtained in this way that the outer layer with the filtering means will be biased against the well wall after the expansion means has come into contact with the selected fluid. Therefore, the solid particles partially entering the wellbore are prevented from flowing longitudinally along the entire screen, thereby eliminating the risk of blocking the entire screen due to the local inflow of solid particles. In addition, the expanded outer layer supports the wellbore to greatly reduce sand production failures at the wellbore. In addition, the expanded outer layer provides a large inflow area for the screen.

For example, the wellbore may be a production well that produces hydrocarbon fluids (crude oil or natural gas) or water. Alternatively, the wellbore may be an injection well that injects water, oil, gas, waste fluids, or other fluids into the formation. In another example, the selected fluid that can expand the expansion device may be a production fluid such as a hydrocarbon fluid or water, or an injection fluid such as a hydrocarbon fluid (eg, crude oil, diesel or natural gas) or water.

In the case of production wells producing hydrocarbon fluids, rapid activation may be achieved by pumping hydrocarbon fluids, such as diesel oil, into the wellbore to cause expansion of the expansion device. Once expansion is achieved, said expansion can be maintained by exposing the expansion device to produced hydrocarbon fluids.

It will be appreciated that, in the case of injection wells, plugging problems may arise in the time interval between cessation of fluid injection and backflow of fluid from the wellbore into the screen.

Suitably, said expansion device comprises a plurality of expandable rings, each ring extending around said catheter and susceptible to expansion upon contact with a selected fluid, said rings being spaced apart from each other along said catheter, for example by the same mutual spacing arrangement.

In another arrangement, the expansion device comprises a sleeve surrounding the catheter, the sleeve having a plurality of through holes spaced along the sleeve, for example the through holes having a substantially rectangular shape or a substantially circular shape .

In a preferred embodiment, said expansion means comprises a material which readily expands upon contact with hydrocarbon fluid or water.

The material is, for example, a rubber selected from NBR, HNBR, XNBR, FKM, FFKM, TFE/P, EPDM-based rubbers when it swells in contact with water.

The material preferably comprises a rubber selected from the group consisting of natural rubber, nitrile rubber, hydrogenated nitrile rubber, acrylate butadiene rubber, polyacrylate rubber, when swelled by contact with hydrocarbon fluids. Polyacrylaterubber, butyl rubber, bromobutyl rubber, chlorinated butyl rubber, chlorinated polyethylene rubber, neoprene, styrene butadiene copolymer rubber, sulfonated polyethylene rubber ), vinyl acrylate rubber (ethyleneacrylate rubber), epichlorohydrin ethylene oxide copolymer, binary ethylene propylene rubber (peroxide cross-linked), binary ethylene propylene rubber (sulfonated cross-linked), ternary Ethylene propylene rubber, ethylene vinyl acetate copolymer, fluorinated rubber, fluorosilicone acrylic rubber, silicone rubber.

Preferably, the material is selected from EP(D)M rubber (peroxidized or sulfonated ethylene rubber), EPT rubber (ethylene propylene diene), butyl rubber, bromobutyl rubber, chlorobutyl rubber Base rubber, and rubber selected from chlorinated polyethylene rubber.

Suitably, the outer layer comprises an annular filter layer and an annular shroud extending around the annular filter layer.

Description of drawings

The present invention will be described in more detail below by way of examples and in conjunction with the accompanying drawings.

Fig. 1 schematically shows a longitudinal section of an embodiment of the wellbore screen of the present invention before expansion of the expansion device;

Figure 2 schematically shows a longitudinal section of the embodiment of Figure 1 after expansion of the expansion device;

Fig. 3 schematically shows the section at section line 3-3 in Fig. 1;

FIG. 4 schematically shows a section at section line 4-4 in FIG. 2 .

Like reference numerals denote like parts in the figures.

Detailed ways

Referring to Figures 1 and 2, there is shown a wellbore screen 1 disposed in a wellbore 2 producing hydrocarbon fluids. The screen 1 comprises: a tubular part 3; a permeable annular outer layer 4 surrounding the tubular part 3 at a radial distance, said outer layer 4 consisting of a filter layer 4a and a cover layer 4b outside the filter layer; An expandable element in the form of a ring 6 between 3 and the outer layer 4 . The rings 6 are arranged at regular intervals along the tubular part 3 . The outer layer 4 is flexible and can radially expand at least a rate of expansion to bring the cover layer 4b into contact with the borehole wall. Furthermore, the filter layer 4a has a mesh size suitable for preventing solid particles from flowing into the tubular part. The ring 6 is made of an elastic material, such as EPDM rubber, which expands on contact with hydrocarbon fluids. The tubular member 3 has a plurality of perforations 7 for allowing produced hydrocarbon fluids to flow into the tubular member 3, and at its end has a conduit 9 for interconnecting the wellbore screen 1 to deliver the produced hydrocarbon fluids to Corresponding connection parts 8, 10 of the ground.

Figure 1 shows the wellbore screen 1 before the rings 6 have been expanded in contact with produced hydrocarbon fluids, so that the outer layer 4 is in an unexpanded state so that there is a gap 11 between the overburden 4b and the wellbore wall.

FIG. 2 shows the wellbore screen 1 after the ring 6 has been expanded in contact with produced hydrocarbon fluids, so that the outer layer 4 has been radially expanded through the ring 6 so that the annular overburden 4b contacts the wall of the wellbore 2 .

Figure 3 shows the cross-section of the wellbore screen 1 and the wellbore 2 before the ring 6 is expanded. As shown in the figure, the filter layer 4a is composed of a plurality of overlapping filter sheets 5 . Each filter disc 5 is connected at its ends by a corresponding lug 14 to one or more rings 6 and overlaps an adjacent filter disc 5 . The cover layer 4b is a thin metal cylinder with a mesh formed by overlapping longitudinal slits (not shown) in the longitudinal direction, which give the cover layer 4b great flexibility for radial expansion to provide filter layer 4a adequate protection.

Referring to Figure 4, there is shown a cross-section of the screen 1 and wellbore 2 after the ring 6 has been expanded. The outer layer 4 has expanded against the borehole wall, so that during the expansion of the filter layer 4a there is relative sliding of the adjacent filter sheets 5 and during the expansion of the cover layer 4b the seams of the cover layer 4b widen.

For the sake of simplicity, not all rings 6 and eyelets 7 have been identified with reference numerals in the figures.

During normal use, the screen 1 is lowered into the wellbore 2 and set in a reservoir containing hydrocarbon fluids in the surrounding formation so that the rings 6 are in their respective unexpanded state and the interstices 11 exist in the outer layer 4 and the wall of the wellbore 2 (Fig. 1). When the wellbore 2 is on production, a stream of crude oil flows from the surrounding formation into the wellbore 2 and through the outer layer 4 and the perforations 7 and thence into the tubular member 3 . Thus, the flow of hydrocarbon fluid flows along the ring 6, whereby the ring 6 transforms from its unexpanded state (Fig. 1) to an expanded state (Fig. 2). Upon expansion, the ring 6 is pushed in a radially outward direction against the outer layer 4 , whereby the outer layer 4 expands against the wall of the wellbore 2 . The expansion forces exerted by the ring pack are distributed along the length of the outer layer 4, so that the outer layer 4 will substantially adapt to larger irregularities of the borehole wall after its expansion. Since each filter sheet 5 slides relative to each other during the expansion of the filter layer 4a so that the overlapping amount of adjacent filter sheets 5 is reduced, the mesh size of the filter layer 4a will not change due to radial expansion. The degree of overlap of adjacent filter sheets 5 is chosen to maintain sufficient overlap of the filter sheets 5 after expansion of the filter layer 4a to ensure that no openings are present which would allow fluid to bypass the filter layer 4a.

Accelerated expansion of the annulus 6 can be obtained, if desired, by pumping diesel or other suitable fluid into the wellbore 2 before bringing the well into production.

It is thus achieved that the hydrocarbon fluid flow is prevented from flowing axially along the outer side of the outer layer 4 , thereby preventing sand or clay particles which can locally enter the hydrocarbon fluid flow from flowing in longitudinal direction along the entire outer layer 4 . Since this flow of particles along the entire outer layer 4 may lead to clogging of the entire filter layer 4b, especially in the case of clay particles entering the wellbore, the present invention has important advantages.

Other advantages of the wellbore screen of the present invention are the solid pre-drilled tubular member with high resistance to collapse, the annulus between the tubular member and the outer layer and the expansion mechanism, the annulus provides good flow for the produced fluids characteristic, the expansion mechanism avoids the need to mechanically expand the tubular member.

Instead of all rings being made of an elastic material that swells when in contact with hydrocarbon fluids, one or more rings may be made of a material that swells when in contact with formation produced water. For example, the rings may comprise a first set of rings susceptible to expansion in hydrocarbon fluid and a second set of rings susceptible to expansion in water, whereby the first and second sets of rings are arranged in an alternating manner.

Furthermore, instead of each filter disc being connected at its ends to some or all of the rings, any other suitable portion of the filter discs could be connected to the rings. Additionally, the filter discs may be held in place by the cover layer so that there is no need to attach the filter discs to some or all of the rings.

As an alternative to a slotted covering with overlapping longitudinal slits, any other suitable covering can be used, such as a foldable covering with hinges to allow the covering to unfold, or a covering made of a number of interconnected small tubes. The covering layer is formed so that the individual tubes flatten out as the covering layer expands.

Claims (12)

1. A wellbore screen for controlling the flow of solid particles into a wellbore, the wellbore screen comprising: a conduit for transporting fluid; an outer layer for reducing the amount of solid particles flowing into the conduit, the outer layer a layer extending around said conduit and radially expandable against the well wall; an expansion device disposed between the conduit and the outer layer, said expansion device being susceptible to expansion upon contact with a selected fluid to radially expand the outer layer Lean against the wall of the well. 2. The wellbore screen of claim 1, wherein said expansion means comprises a plurality of expandable rings, each ring extending around said conduit and susceptible to expansion upon contact with a selected fluid, said The rings are spaced apart from each other along the conduit. 3. The wellbore screen of claim 2, wherein said rings are arranged at regular mutual spacing along the conduit. 4. The wellbore screen of claim 1, wherein the expansion device comprises a sleeve extending around the conduit, the sleeve having a plurality of through holes spaced along the sleeve. 5. The wellbore screen of claim 4, wherein each through hole has a substantially rectangular shape or a substantially circular shape. 6. The wellbore screen of any one of claims 1-5, wherein the expansion means comprises a material that readily expands when in contact with hydrocarbon fluid or water. 7. The wellbore screen according to claim 6, wherein the material is a material that is easy to swell when it contacts water, and includes nitrile rubber, hydrogenated nitrile rubber, carboxylated nitrile rubber, fluorinated Rubber selected from polymer rubber, tetrafluoroethylene/polypropylene rubber, EPDM rubber, neoprene rubber, chlorosulfonated polyethylene rubber, chlorinated polyethylene rubber, and polyurethane rubber. 8. The wellbore screen according to claim 6, wherein said material is a material that swells easily when in contact with hydrocarbon fluids, and comprises natural rubber, acrylic butadiene rubber, butyl rubber, brominated Butyl rubber, chlorinated butyl rubber, chlorinated polyethylene rubber, neoprene rubber, styrene butadiene rubber, sulfonated polyethylene rubber, ethylene acrylate rubber, surface Rubber selected from chlorohydrin ethylene oxide copolymer, epichlorohydrin ethylene oxide terpolymer, ethylene propylene rubber (peroxidation crosslinked), EPDM rubber, silicone rubber. 9. The wellbore screen according to claim 8, wherein said material is selected from ethylene propylene copolymer (peroxidation cross-linked), EPDM, butyl rubber, bromobutyl rubber , chlorinated butyl rubber, and rubber selected from chlorinated polyethylene rubber. 10. The wellbore screen according to any one of claims 1-9, wherein the outer layer comprises an annular filter layer and an annular cover layer extending around the annular filter layer. 11. The wellbore screen according to any one of claims 1-10, wherein the wellbore is a wellbore for producing hydrocarbon fluid or water from the formation. 12. A wellbore screen substantially as hereinbefore described with reference to the accompanying drawings.

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