CN101175893B - Self conforming screen - Google Patents

Abstract

A screen assembly has a material that conforms to the borehole shape after insertion. The assembly comprises a compliant layer that takes the borehole shape on expansion. The outer layer is formed having holes to permit production flow. The material that is selected preferably swells with heat a nd preferably comprises a shape memory foam that is thermoset. The base pipe ca n have a screen over it to act as an underlayment for support of the conformin g layer or alternatively for screening. The conforming layer can expand by itself or expansion can also occur from within the base pipe.

Description

adaptive screen

priority information

This application is a continuation-in-part of US Patent Application Serial No. 10/226,941 filed August 23,2002.

technical field

The technical field of the invention is downhole screens, and more particularly downhole screens that are expandable in openholes to seal off irregularly shaped wellbores.

Background technique

In the past, gravel packs on the outside of downhole screens have dominated sand control methods. The idea is to fill the annulus outside the screen with sand to prevent the production of unwanted solids from the formation. More recently, with the advent of pipe expansion techniques, it has been recognized that gravel packs would not be needed if the screens were expanded in situ to eliminate the surrounding annulus that was previously sand-packed. Due to the irregular shape of the wellbore, the use of screen expansion technology as an alternative to gravel packing has been problematic. Fixed expanders expand the screen by a fixed amount. The problem is that erosion in the wellbore can still leave a large annulus on the outside of the screen. Conversely, the reduced diameter in the wellbore creates the risk of jamming the fixed expander.

An improvement on fixed expander technology is the use of various forms of flexible expanders. In theory, these flexible expanders are adaptable so they will bend inward at the reduced diameter, reducing the risk of jamming the expander. On the other hand, if there is an empty area, the same problem exists that the flexible expander has a limited outer dimension to expand the screen outward. Therefore, when flexible expanders are used, there is still the problem of leaving an annular gap outside the screen, which can result in the production of unwanted solids when the well is producing from this zone.

Previous screen designs used pre-compressed felt held by a metal sheath, which was then subjected to chemical attack when placed downhole in the desired location. The felt can then expand from the pre-compressed state. The screen does not expand. Such designs are described in US Patents 2,981,332 and 2,981,333. Patent 5,667,011 discloses a fixed expander for expanding a downhole slotted liner. US Patent 5,901,789 and US Patent 6,012,522 disclose expanded wellbore screens. US Patent 6,253,850 discloses the technique of inserting a non-porous liner into another expanded slotted liner to seal it off, and using rubber or epoxy to seal between the liners. US Patent 6,263,966 discloses a screen with longitudinal pleats that expands downhole. US Patent No. 5,833,001 discloses curing in situ rubber to make a patch after expansion by a swell. Finally, US Patent 4,262,744 generally relates to techniques for making screens using molds.

Contents of the invention

The apparatus and method of the present invention solves this problem by providing a screen assembly having an outer layer that expands to conform to the shape of the wellbore. In a preferred embodiment, the selected material is one that expands upon contact with wellbore fluids to further facilitate filling of empty regions within the wellbore after expansion. In an alternative design, no screen expansion is required, and the outermost layer expands to conform to the shape of the wellbore upon contact with wellbore fluid or other fluids introduced into the wellbore. Screen sections are fabricated in such a way that welds are reduced or eliminated. Welds are under severe loads during expansion, so minimizing or eliminating welds provides more reliable screen operation after expansion. These and other advantages of the present invention will become more apparent to those skilled in the art after reading the following description of the preferred embodiment and claims.

The screen assembly has a material that conforms to the shape of the wellbore after insertion. The assembly includes a compliant layer that expands to take the shape of the wellbore. The outer layer is formed with holes to allow flow of the product. The selected material preferably expands upon heating and preferably comprises a thermoset shape memory foam material. The base pipe may have a screen on it to serve as a supporting adaptation layer or optionally a substrate layer for screening. The compliant layer can be self-expandable or expandable from within the base tube.

According to one aspect of the present invention, there is provided a well completion method comprising: covering at least one base pipe with a porous compliant material that expands when contacted with wellbore fluids; running the base pipe into a desired location in the wellbore ; filling an annulus between the compliant material and the wall of the wellbore; filtering fluid flowing through the compliant material to the base pipe.

Description of drawings

Accompanying drawing 1 is the sectional elevation view of screen pipe; With

Figure 2 is a cross-sectional view of a screen assembly, one of which is shown in Figure 1, in a downhole expanded position.

Detailed ways

Figure 1 shows a portion of a length of screen 10 . It has a base pipe 12 above which is a screen 14 above which is an external adaptation layer 16 . Layer 16 has a plurality of holes 18 . The base pipe 12 also has holes 20 . The actual filter material or screen 14 may be a wire mesh or fabric or other known filter products. The conforming layer 16 is preferably soft so that it will flow when the screen 10 expands. Preferred materials are those that swell when exposed to wellbore fluids for an extended period of time. Three examples are nitrile, natural rubber and AFLAS. In an alternative embodiment, the compliant layer 16 expands sufficiently to contact the wellbore after placement in the wellbore without the screen 10 expanding. Shown schematically at ends 22 and 24 of screen 10 are snap rings 26 and 28 . As the screen 10 expands, these stop rings will restrain the compliant layer 16 to prevent longitudinal movement of the compliant layer 16 in the annulus outside the screen 10 after the screen has expanded. Their use is optional.

The manner in which the screen 10 is assembled is another aspect of the invention. The compliant layer 16 may have an inner diameter that allows it to fit over the screen material 14 . An assembly of screen material 14 and adaptation layer 16 is slipped onto base pipe 12 . Afterwards, a known expansion tool is applied inside the base pipe 12 to slightly expand it. As a result, both the screen material 14 and the compliant layer 16 are secured to the base pipe 12 without the need for welding. This is advantageous because when the screen 10 is run into the wellbore and expanded, the expansion process puts high stress on the weld which can cause the screen to fail. An alternative way of assembling the screen 10 is to attach the screen material 14 to the base pipe 12 in the manner just described, followed by curing the adapting layer 16 on the screen material 14 . Alternatively, a protective overcoat (not shown) may be applied over the screen material 14, with the adaptation layer 16 installed on top of the protective overcoat. Even with the optional perforated protective jacket (not shown), the joining process expands from the inside out of the base pipe 12 as previously described.

The holes 18 can be of various shapes. Their function is to allow formation fluids to flow through after swelling. They may be circular holes, or slits, or other shapes, or a combination of shapes. The conforming layer 16 may be made of a polymeric material, preferably a material that expands upon continued exposure to wellbore fluids to better conform to the irregular shape of the wellbore 30, as shown in FIG. 2 . FIG. 2 also shows an outer protective casing 32 placed over the screen material 14 and below the adaptation layer 16 to protect the screen material 14 when placed in the wellbore 30 . The outer casing 32 is a known product with punched out openings 33 and may be used optionally if the conforming layer 16 is used. The reason it is optional is that the adaptation layer 16 provides to some extent the desired protection during the run-in process. Furthermore, without jacket 32, conforming layer 16 can be made thicker to better fill void volume 34 in the annulus around screen 10 after expansion. The thickness of the compliant layer 16 is limited by the outer diameter of the wellbore and components installed within it. Preferably, the conforming layer 16 is tightly squeezed, as this facilitates its movement to fill the void in the surrounding annulus.

Those skilled in the art will appreciate that the present invention allows for the manufacture of expandable screens that eliminate welds between layers. The use of a compliant material 16 allows the use of multiple expansion techniques and improves the ability to eliminate voids outside the expanded screen due to wellbore irregularities. Alternatively, the compliant material 16 may expand sufficiently without the screen 10 expanding downhole to allow the need for gravel packing to be eliminated. If this material swells due to exposure to downhole fluids, it may be desirable to use it as the compliant layer 16 . A protective jacket 32 beneath the compliant layer 16 may be used to protect the screen material 14 during running.

The conforming layer 16 may be a foam material, preferably a thermoset foam material, but may also be a thermoplastic foam material. The conforming layer 16 is shown as cylindrical, but may be altered, for example by concave ends or striated regions (not shown), to facilitate placement, or to enhance the filtering properties of the layer. The conforming layer 16 is preferably constructed of a resilient memory foam material, such as an open cell syntactic foam. Such foams have the property of being able to transform from one size and shape to another size and/or shape by changing the temperature of the foam. Such foams can be formed into objects of desired original size and shape, such as cylinders of desired outer diameter. The foam thus formed is then heated to raise its temperature to its transition temperature. When it reaches the transition temperature, the foam material softens, allowing the foam to be reshaped to the desired transition size and shape, such as by compression to form a smaller diameter cylinder. The temperature of the foam is then lowered below the transition temperature so that the foam retains its transition size and shape. When subsequently raised back to its transition temperature, the foam will return to its original size and shape.

Cylindrical foam compliant layer 16 may be initially formed on screen 10 or base pipe 12 by wrapping a foam blanket having a desired original outer diameter OD ₁ . Alternatively, the process of forming the compliant layer 16 on the base pipe 12 or screen 10 may be any other process that produces a compliant layer 16 of the desired original diameter, such as directly molding foam. The desired original outer diameter _OD1 is greater than the borehole diameter (BHD) where the assembly will be deployed. For example, a compliant layer 16 having an original outer diameter _OD1 of 10 inches may be formed for an 8.5 inch diameter wellbore.

The foam components are formulated to achieve the desired transition temperature. This property allows foams to be formulated with the desired transition temperature anticipated for a particular application. For example, when used in the present invention, the foam component may be formulated so that the transition temperature is only slightly below the expected downhole temperature at the depth at which the component will be used. This causes the temperature expansion of the compliant layer 16 at the desired depth and remains expanded against the wellbore wall. Downhole temperature may be used to expand the adaptation layer 16; alternatively, other means, such as a separate heat source, may be used. Such a heat source may be a cable run electric heater, or a battery powered heater. For example, such a heat source may be mounted to the base pipe 12 , integrated therein, or mounted in contact with the foam compliant layer 16 . The heaters can be controlled from the surface at the wellsite, or by timing devices or pressure transducers. Also, the exothermic reaction may be produced by chemicals pumped downhole from the surface, or heat may be generated by any other suitable means.

The conforming layer 16 can be made to function as the sole filter medium without using any screen material, such as 14 . This is due to the nature of the conforming material to be porous. However, its conventional production technique is that the mold leaves an impermeable layer on its entire periphery. This property allows the material to function essentially as a barrier material under demolded conditions. However, if the impermeable layer of the outer surface that eventually comes into contact with the wellbore wall is stripped or otherwise removed, the compliant layer 16 can be installed on the base pipe 12 or the screen 14 and can act alone as the sole filter material or For use with screen 14. The screen 14 may be configured exclusively for structural support of the compliant material 16 so that the compliant material does not pass through the base pipe 12 as wellbore fluid is filtered through the compliant material 16, or the screen may be omitted entirely. The uphole and downhole ends of the compliant material 16 may have an impermeable layer left from the molding process during manufacture to better guide fluid into the openings in the base pipe 12 .

The conforming material may preferably be a shape memory polymer, which is porous and thermoset, although thermoplastics could also be used if they were porous, or could be manufactured under that condition.

The foregoing disclosure and description of the invention are exemplary and explanatory and various changes may be made in size, shape and materials, as well as specific details of the exemplified constructions, without departing from the spirit of the invention.

Claims (8)

1. A well completion method comprising: covering at least one base pipe having the screen thereon with a porous compliant material that expands upon contact with wellbore fluids; running the base pipe to a desired location in the wellbore; filling an annulus with a compliant material to contact a wall of the wellbore without expanding the screen; Fluid flowing through the compliant material to the base pipe is filtered. 2. The method of claim 1, comprising: Foam is chosen as the adaptation material. 3. The method of claim 1, comprising: A material of shape memory polymer is chosen as said adaptation material. 4. The method of claim 3, comprising: A thermosetting material is chosen as the adaptation material. 5. The method of claim 3, comprising: A thermoplastic material is chosen as the adaptation material. 6. The method of claim 1, comprising: A source of downhole heat is provided to initiate the filling. 7. The method of claim 1, comprising: providing an impermeable layer on the conforming material; and The impermeable layer is removed from the compliant material to expose pores in the compliant material. 8. The method of claim 4, comprising: providing an impermeable layer on the conforming material; and The impermeable layer is removed from the compliant material to expose pores in the compliant material.

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