EP0528328A2

EP0528328A2 - Well packer

Info

Publication number: EP0528328A2
Application number: EP92113657A
Authority: EP
Inventors: Philip Frederick Head
Original assignee: Individual
Current assignee: Individual
Priority date: 1991-08-16
Filing date: 1992-08-11
Publication date: 1993-02-24
Also published as: GB9216531D0; EP0528328A3; GB9117684D0; GB2258674A; GB2258674B; CA2075432A1

Abstract

An inflatable well packer includes several annular layers 1,3,5,7 of material, consisting of a series of oriented fibres 31 encapsulated in a resin. The layers 1,3,5,7 are corrugated along the direction of their circumference such that pressure from the bore through the annular layers causes the corrugations to at least partially unravel, thus causing inflation of the well packer. The fibres 31 within each layer 1,3,5,7 are oriented along the length of the layer, such that their orientations vary along the length of the layers 1,3,5,7.

A method of manufacturing the well packer is also described.

Description

This invention relates to well packers. In particular, the invention relates to inflatable well packers, which in use are inflated by fluid under pressure to isolate a zone in a well.
Inflatable well packers have been known for many years, the packers being used to isolate a zone in a well, so as, for example to enable a drill stem test to be performed, to perform a selective chemical treatment, or to isolate a redundant Zone in a productive well. There are presently two types of inflatable well packers, each being of a multilayered construction including an elastomeric inner bladder, but varying in the bearing system incorporated in the packer. The first type of known well packer includes wire or textile fibres, woven together with their ends secured to end fittings by an epoxy potting process, the sheath of woven wire or fibres being covered in an outer elastomeric boot which will form a hydraulic seal to the casing, or open-hole surface of a wall which the well packer will, in use, isolate. The other type of inflatable well packer utilises long, peripherally overlapping strips of spring steel which, when the packer is inflated, slide radially against each other like Venetian blinds, the strips surrounding the elastomeric inner bladder. The central portions of the strips are bonded to an outer annular elastomeric boot which acts as a hydraulic seal to the casing or open-hole surface in use of the well packer. An example of a well packer of this type is shown in U.S. Patent Number 3160211.
With either of these known well packers there are a number of shortcomings. Firstly, the manufacture of either of these well packers is labour intensive. In the case of the woven sheath reinforced well packer, the reinforcing wire or fabric has to be hand-woven during assembly of the well packer. In the case of the spring steel strip reinforced well packer, the large number of overlapping strips are difficult to assemble and engage in their end fittings.
Furthermore, In either of the known types of well packers, the elastomeric inner bladder has to expand typically by twice the amount that the outer elastomeric boot has to expand. Thus if the packer has to be inflated by a ratio of 3:1 in order for the outer boot to make the required seal, the inner elastomeric bladder will have to expand by a ratio of 6:1. This results in the inner elastomeric bladder in its inflated state being very thin, thus making the inner elastomeric bladder susceptible to any micro faults which it may have in its structure. Furthermore, the high expansion ratio required by the inner elastomeric bladder severely limits the choice of materials which may be used. As a result of the limited choice of materials, the inner elastomeric bladder tends to have a very limited chemical resistance to any fluid other than water, thus limiting the life of the packer when the packer is exposed to fluids such as acids, solvents, diesel oil, and surfactants, these all being chemicals which are commonly required for treatments of zones within wells.
With regard to the outer elastomeric boot in either of the known types of well packers, although this typically only has to expand by a ratio of 3:1, and thus an increased choice of materials enables it to have a better chemical resistance to the fluids used in the wells than that of the inner elastomeric bladder, the outer elastomeric boot still has a relatively short life span.
Finally, there is a further drawback to such known inflatable well packers, in that when they are expanded they exert a high radial stress on the end fitting as they try to expand to a diameter greater than the diameter of the end fitting. This puts a complex compressive stress on the outer reinforcing members of either type of well packer, and furthermore, exerts a high tensile stress on the reinforcing members inner surface. In some cases this has resulted in a splitting of the end fitting, this then releasing the well packer into the well bore.
It is an object of the present invention to provide a well packer, together with a method of making the well packer, wherein these problems are at least alleviated.
According to a first aspect of the present invention there is provided an inflatable well packer comprising at least one annular layer of material wherein at least a portion of the layer of material being corrugated along the direction of the circumference of the layer such that pressure from the bore of the annular layer to causes at least partial unfolding of the corrugations, which results in inflation of the well packer.
Thus, in such a well packer the need for an elastomeric inner bladder and an outer elastomeric boot can be avoided. Furthermore the corrugations enable the differential radial stress present in known well packers to be at least reduced relative to the equivalent expansion ratios of known inflatable well packers.
Preferably the layer(s) of material comprise a series of fibres encapsulated in a resin. The resin encapsulates the fibres on the inside and outside. The thickness of resin is preferably greater on the inside of the fibres compared to the outside.
It is advantageous for the angle of orientation of the fibres with respect to the length of the layer to vary along the length of the layer. It is also advantageous for the fibres to be orientated in the form of a helix.
It is also preferable, for there to be a plurality of layers. Where there are a plurality of layers, at least a portion of the fibres within each layer are suitably oriented along the length of the layer such that adjacent layers comprise fibres which are wound in opposite directions. It is also preferable for adjacent layers to comprise fibres which are wound at different angles.
It is preferable that the angles of orientation of the fibres are such that when the packer is inflated fibres in adjacent layers will lock up so as to oppose further expansion.
The edges of the layers will usually be clamped by a respective end fitting. In such a case, preferably the regions of the layers adjacent to the end fittings are not corrugated.
Preferably, at least one of the layers includes a series of teeth which are effective to dig into a structure surrounding the wall packer when the well packer is inflated.
According to a further aspect of the invention an end fitting is proposed with interlocking parts which coincide with the channels formed by the ribs on the outside circumference of the packer.
According to a further aspect of the present invention there is provided a method of making an inflatable well packer, including the steps of rolling a layer of elastomer onto a mandrel, laying of fibres on top of the layer of elastomer according to the required orientation, rolling a further layer of elastomer on the layer of fibres, and coating with separating material. Further layer or layers can be made in the same way with corresponding sizes to concentrically fit with each other. The layers are then molded into the corrugated shape by means of an appropriately shaped mould tool.
An embodiment of a well packer in accordance the invention, together with a method of making the well packer, will now be described, by way of example only, with reference to the accompanying figures, in which:-

Figure 1 shows a cross-section of the well packer in accordance with an embodiment of the invention;
Figure 2 shows the well packer of Figure 1 in an inflated state;
Figure 3 shows a schematic sectional side view of part of the inflated packer of Figure 2;
Figure 4 shows a schematic cross-section, on an expanded scale along the line IV-IV of the reinforcing fibres shown in Figure 3;
Figure 5 shows a plan view in detail of the reinforcing fibres of Figure 4, the view being shown on an enlarged scale;
Figure 6 shows an enlarged view of a part of the reinforcing fibres of Figure 5;
Figure 7 shows a cross section of an embodiment of an end fitting for the well packer of the invention.
Figure 8 shows a cross section of a mandrel during the first stage of the manufacture of the well packer of figure 1.
Figure 9 shows a cross section of a mould tool used in the manufacture of the well packer of figure 1.
Figure 10 shows a longitudinal cross section of a particular embodiment of the well packer of figure 1.
Figure 11 shows a radial cross section of the embodiment of figure 10.

Referring firstly to Figure 1, the first well packer in accordance with an embodiment of the invention to be described comprises four concentric corrugated reinforcing fibre layers 1,3,5,7 encapsulated in an elastomeric resin 9. A series of ribs 2 are formed around the external circumference of the well packer. The edges of the layers 1,3,5,7 are secured by respective end fittings, not shown in Figure 1, but as will be described hereafter. The well packer of Figure 1 is shown installed on a running tool mandrel 11, a space 13 being defined between the outer surface of the mandrel 11 and the inner surface of the layer 1.
Referring now to figure 2, in use of the well packer, the packer is inserted in the bore of a well. In the particular example shown in Figure 2, the bore of the well is defined by a cylindrical steel casing 15. To inflate the well packer, fluid is pumped into the space 13 between the mandrel 11 and inner layer 1 of the well packer, until the outer layer 7 of fibres conforms to the shape of the inner surface of the lining 15 of the steel casing. As can be seen from Figure 1, the unfolding of the corrugations in the layers 1,3,5,7 enables the expansion of the well packer, without the necessity for the whole of the expansion to be accommodated by the elastic expansion of the elastomeric resin 9. This thus avoids the differential stresses which occur in the prior art well packers.
The layers 1,3,5,7 are separated by a separating layer 8 which is comprised of polytetrafluoroethylene or other suitable material which does not bond with the elastomer 9. This enables the layers 1,3,5,7 to move separately with respect to each other as the well packer is inflated.
Further features of this first embodiment of a well packer in accordance with the invention will now be described in relation to Figure 3 which shows a sectional side view of the edge of the well packer in an expanded state, including an end fitting 17, a similar end fitting (not shown) being attached to the opposite edge of the well packer. These end fittings 17 will be described in more detail hereafter.
As can be seen from Figure 3, with the well packer in its inflated state, there are defined first 19 and second 20 shoulder portions in the layers 1,3,5,7 between the end fitting 17 and the expanded portion of the well packer which contacts the lining 15 of the steel casing. At the first shoulder portion 19, the layers change from having a corrugated cross-section in their non-expanded configuration, to a circular cross-section, whilst the second shoulder portion 20 corresponds to the point at which the fibres within each layer 1,3,5,7 have been displaced away from the adjacent fibres in the layer. The fibres for each of the layers are variably oriented along the length of the packer such that their orientations when the packer is inflated describe a helix, with the orientations of the fibres in adjacent layers 1,3,5,7 being in opposite senses. At each of these shoulder portions 19,20, the fibres within each layer 1,3,5,7 are oriented in their fully extended position or lock up position in the inflated state.
As is well-known in the hydraulic hose industry, where the helix angles of a set of helically oriented fibres are oppositely directed to the fibres in an adjacent layer, and the fibres in the adjacent layers are at 57°, if internal pressure is applied to the layers, then the fibres within the two layers will lock-up preventing further expansion. Thus in the well packer, this prevents a large radial tensile stress being produced at the entrance 21 to the end fitting 17 as would be the case in conventional well packers. In the well packer, the fibres are variably oriented along the length of the packer in the packers unexpanded state. Thus, as the packer is inflated the fibres will try to change their helical angle relative to the longitudinal axis of the packer up to the maximum angle of 57°, at which point the fibres in adjacent layers will lock up. In order to reduce the expansion of the layers close to the end fittings 17, the initial helix angle before expansion of the well packer is arranged to be at least 57°, so that the packer does not expand by a large amount before the interaction of the adjacent layers causes locking up. As the distance of the fibres from the end fittings 17 increases, the fibre helix angle is reduced such that the amount by which the fibres can be displaced is increased, thus causing a corresponding expansion of the packer. Thus control of the orientation of the fibres along the length of the packer provides a corresponding control of the amount which the various regions of the packer can expand, the inflated expansion profile having a uniform stress distribution.
In figure 7 is shown an alternative end fitting comprising an inner fitting 101 and an outer fitting 102. The inner fitting 101 comprises outwardly extending fins 103 which correspond with the internal channels formed on the inside diameter of the ribs 2 of the ribbed well packer. The outer end fitting 104 comprises a plurality of elongate elements with inwardly extending projections 105 which correspond to the channels formed on the outside surface of the ribs 2 of corrugated well packer. The outer end fitting 104 and inner end fitting 103 are joined at the end and are secured to the running mandrel 11 by suitable means such as by means of a thread (not shown).
The composition of the layers 1,3,5,7 is shown in more detail in figures 4, 5 and 6. Referring firstly particularly to Figure 4, when the well packer expands, the fibres 23 within each of the layers 1,3,5,7 move away from each other, causing necking of the inner circumferential surface of the well packer as a result,
as indicated at 25 in Figure 4, the outer surface of the packer being constrained into a cylindrical configuration by the lining 15 of the steel casing.
It will be appreciated that the more layers of fibres incorporated within the well packer, the finer will be the resulting mesh distribution, and the less will be the unsupported regions 27 shown in figure 6, between the fibres 23. In order to reduce the number of unsupported regions 27 which may occur, it may be advantageous to include short fibre reinforcements 29 in the elastomeric matrix as indicated in Figure 6. When the well packer is inflated, these short fibres 29 will maintain the links between the fibres 23, thus providing a bridging action over the unsupported regions 27 when the well packer is expanded. Suitable materials for the fibres 29 include glass fibres and short Kevlar fibres. The fibres 29 will also perform a memory function, helping the well packer to recover to its non-inflated form after inflation.
Fibres in adjacent layers can vary in the angle of orientation to the length of the packer as well as having a varying angle of orientation within each layer.
The manufacture of the well packer comprising two layers will now be described with reference to Figures 8 and 9. Referring firstly to Figure 8, an inner elastomeric layer 111 of 3 mm thick is rolled onto a mandrel 112. A layer of fibres 113 is then laid on the layer of elastomer. A final layer of separating material such as polytetrafluoroethylene is then applied to the outside surface of the elastomer. A further layer of grease proof material can also be applied to aid the subsequent rolling together of a plurality of layers concentrically. This process is repeated for a second layer of elastomer and fibres. Referring now to figure 9, these two layers are removed from the mandrel and fitted together concentrically one inside the other and placed in a mould tool. The mould tool comprises appropriate tool parts 114 for the inside and outside of the packer to mould the corrugations 7 into shape. The whole assembly is then cured at a curing temperature suitable for the elastomers used.
Referring now to Figures 10 and 11, these figures show an adaptation of the embodiments of the well packer in accordance with the invention described herebefore. In a well packer in accordance with the invention it may be useful to incorporate an anti-slip feature consisting of a continuous strip of material 73 on which sharp pointed teeth 75 are positioned at regular intervals. This strip 73 will be located in the troughs defined between the corrugated inner surface of the outer reinforcing layer 7, and the corrugated outside surface of the next layer 5. When the well packer is inflated the teeth 75 will pierce the outer layer 7 at some parts of the packer outer surface, and on increased pressure will dig into the surface of the constraining surface 15 of the cylindrical steel casing, thus anchoring the well packer firmly to the inside of the casing. The continuous strip 73 will prevent the individual teeth 75 from being ripped out of the well packer when the packer is subjected to a longitudinal load, for example on removal of the packer from the casing.
It will be appreciated that whilst in each of the embodiments of the well packer described herebefore by way of example, there are four layers of reinforcing fibres, a well packer in accordance with the invention may have any number of layers, including a single layer, although multiple layers are advantageous. Where a single layer of reinforcing fibres is used, the use of the short fibres 29 to bridge the gaps between the reinforcing fibres, when the well packer is in an expanded state, is particularly advantageous.
It will also be appreciated that whilst in the particular well packers in accordance with embodiments of the invention, described hereinbefore, the encapsulating resin is an elastomeric material, a well packer in accordance with the invention enables the use of encapsulation resins other than elastomeric, thus allowing the selection of highly resilient material with good resistance to the well bore and treatment fluids. Suitable alternative encapsulation resins are fluoroplastics such as PTFE or FEP, which are sold under the trade names Teflon and Xynar, or polyphenylene sulphide such as PPS, which is sold under the trade names Ryton and SUPEC. All of these materials have limited elastic properties, but do have good chemical resistance of the chemical, pressure, and temperature conditions in which the well packer is likely to be required to operate. Where a non-elastomeric material is chosen for the encapsulating resin, the use of the short reinforcing fibres 29 to provide a memory function to help recovery of the well packer to its non-inflated state is particularly advantageous.

Claims

An inflatable packer comprising at least one annular layer of material, characterised in that at least a portion of the layer of material is corrugated along the direction of the circumference of the layer such that pressure from the bore of the annular layer causes at least partial unfolding of the corrugations, thus resulting in inflation of the packer.
An inflatable packer according to claim 1, characterised in that the layer of material comprises a series of fibres encapsulated in a resin.
An inflatable packer according to claim 2 characterised in that the thickness of resin encapsulating the fibres on the inside is greater that the thickness of the resin on the outside of the fibres.
An inflatable packer according to any one of the preceding claims, characterised in that it comprises more than one layer.
An inflatable packer according to claim 4, characterised in that each layer is separated by a suitable separating means.
An inflatable packer according to claim 5, characterised in that the separating means is made from polytetrafluoroethylene.
An inflatable packer according to claim 4, characterised in that the layers are not separate but are formed from a common encapsulating material.
An inflatable packer according to any of the preceding claims 2 to 7, characterised in that at least a portion of the fibres within each layer are orientated along the length of the layer in a helical manner.
An inflatable packer according to any of the preceding claims 2 to 7, characterised in that the angle of orientation of the fibres with respect to the direction of the length of the layer varies along the length of the layer.
An inflatable packer according to claim 4, characterised in that adjacent layers comprise fibres which are wound in opposite directions.
An inflatable packer according to claim 4, characterised in that adjacent layers comprise fibres which are wound at different angles to the direction of the length of the layers.
An inflatable packer according to any one of the preceding claims, characterised in that the regions at the ends of the layers are not corrugated to allow clamping by a respective end fitting.
An inflatable packer according to any one of the preceding claims, characterised in that at least one end of at least one layer includes a series of teeth which are effective to dig into a structure surrounding the packer when the packer is inflated.
An inflatable packer according to any one of claims 1 to 12, characterised in that at least one end of at least one layer includes a series of indentations which are adapted receive corresponding teeth in a structure surrounding the packer.