Pipe Lining

This invention relates to lining and particularly, although not exclusively, relates to a method of lining a casing affixed within a wellbore.

As the drilling of an oil or gas well progresses, the well bore is lined with a casing that is secured in place by a cement slurry injected between the exterior of the casing and the well bore. The casing commonly consists of steel tubulars joined by couplings and functions to provide a permanent well bore of known diameter through which drilling, production, or injection operations may be conducted. The casing also provides the structure for attaching surface equipment required to control and produce fluids from the well bore or for injecting fluids therein. In addition, the casing prevents the migration of fluids between subterranean formations through the well bore (e.g., the intrusion of water into oil or gas formations or the pollution of fresh water by oil, gas, or salt water) .

Heat loss from produced fluids through the steel tubulars and couplings of the casing to the surrounding subterranean formations is relatively high due to the high thermal conductivity of steel and rock. Heat loss from the produced fluids can be problematic during production. For example, if a gas is produced through the steel tubulars, liquids condensing from the gas due to cooling can result in liquid dropout thereby causing a loss of valuable fluids and reducing the flow of the gas through the steel tubulars . Another problem may arise when temperature loss from the produced fluids induces the

formation of scales, paraffin, or other deposits on the steel tubulars, thereby creating restrictions, or even a blockage, of the fluid flow though the steel tubulars.

Though vacuum insulated steel tubing offers sufficient insulation, heat loss from the couplings may reduce the total insulation quality significantly. Furthermore, couplings can create discontinuities along the flow path that result in increased friction and turbulence in the flow of produced fluids. Plastic liners have demonstrated insulation benefits and are more consistent than vacuum insulated steel tubing because they do not have couplings. Plastic liners are generally less expensive than vacuum insulated steel tubing; however, current plastic liners are not as effective in insulation benefits per foot as the vacuum insulated steel tubing.

A method of lining a casing with a continuous string of tubular polymeric material has previously been proposed in U.S. Pat. No. 5,454,419 (Vloedman) . The method utilizes a continuous, smooth walled high density polyethylene tubular liner wound on a portable spool. The smooth walled liner has an outer diameter greater than the inner diameter of the casing and is reeled off the spool and through a roller reduction unit to reduce the diameter of the liner so that the liner can be injected into the casing. A weight system connected to the bottom end of the liner maintains the reduced liner in tension so that the liner remains in its reduced state until the liner is positioned at a desired depth. After the liner is run to such depth, the weights are removed thereby allowing the reduced liner to rebound and form a fluid tight seal with the casing and seal any breaches in the casing.

US 6283211 (Vloedman) discloses a method of patching a downhole casing using a casing patch which may comprise a high density polyethylene pipe. In the method, the pipe is compressed to form a reduced state and is maintained in its reduced state by weights which are arranged to act on the pipe and maintain it under tension. After the pipe has been positioned in the casing as desired, the weights are removed, thereby to remove the tension and therefore remove the force restricting expansion of the pipe. Accordingly, the pipe expands out against the casing.

One problem associated with the arrangements described is that, in both cases, weights are used to maintain the compressed pipes under tension. These weights are introduced into the casing with the pipe and apparatus must be provided to allow them to be removed to allow the pipe to expand when in position. The provision of weights as described adds to the complexity and/or cost of positioning a pipe in position using the aforementioned methods .

The inventor of the aforementioned patent applications has appreciated the aforementioned problem and has proposed a solution in US2004/0140093 (Vloedman) . The solution involves providing a pipe having an exterior surface which is provided with grooves and ridges. The outer diameter of the polymeric pipe is reduceable by the application of radially compressive forces to the ridges so that the outer diameter of the polymeric pipe is less than the inner diameter of the casing. Reduction of the pipe creates point loads that cause the polymeric pipe to deform non-uniformly whereby stress induced to the

polymeric pipe by the reduction thereof is stored in the polymeric pipe thereby decreasing the rate of expansion of the polymeric pipe and thus allowing the polymeric pipe to be inserted into the casing to a desired depth prior to the polymeric pipe expanding and engaging the internal wall of the casing. It is made clear in the document that a reduced diameter of pipe which is free of added weight can be introduced into a casing.

However, disadvantageously, the solution according to US 2004/0140093 necessitates use of a complex shaped pipe with its associated costs of production and, in any event, the pipe described still rebounds in about 12 hours so that the reduced diameter pipe cannot be stored for any appreciable length of time prior to introduction downhole. Essentially, therefore, the reduced diameter pipe must be produced at the site where it is to be used.

It is an object of the invention to address problems associated with lining of casings.

According to a first aspect of the invention, there is provided a method of lining a casing affixed within a well bore, comprising the steps of:

(b*) selecting a compressed polymeric pipe having a wall with an inner diameter, an outer diameter, an interior surface, and an exterior surface, wherein said polymeric pipe comprises polyetheretherketone;

(c) passing the compressed pipe into the casing to a predetermined depth; and

(d) subjecting the compressed pipe to conditions whereby the compressed pipe expands against the inner wall of the casing.

The invention extends to a method of lining a casing affixed within a well bore, comprising the steps of:

(a) selecting a polymeric pipe having a wall with an inner diameter, an outer diameter, an interior surface, and an exterior surface, wherein said polymeric pipe comprises polyetheretherketone;

(b) reducing the outer diameter of the polymeric pipe to produce a compressed pipe by applying a compressive force so that the outer diameter of the polymeric pipe is less than the inner diameter of the casing whereby stress induced to the polymeric pipe by the reduction thereof is stored in the polymeric pipe without maintaining the pipe in tension by use of a force independent of the pipe;

(c) passing the compressed pipe into the casing to a predetermined depth; and

(d) subjecting the compressed pipe to conditions whereby the compressed pipe expands against the inner wall of the casing.

Advantageously, the method may enable a said compressed pipe to be made from a selected pipe at a relatively low temperature, for example at ambient temperature, so no separate heating of the selected pipe may be required to enable it to be compressed. After compression, the compressed pipe may remain in such a state for a

substantial period of time, for example substantially indefinitely, without the need for it to be cooled to less than ambient temperature or for a force to be applied to restrict its expansion. Accordingly, it is possible to delay the fitment of the compressed pipe in position within the casing.

The wall of the pipe selected in step (a) may have a thickness of at least 0.25cm, preferably at least 0.5cm. The thickness of the wall may be selected in dependence upon the diameter of the pipe, with pipes having larger diameters having a thicker wall. The wall may have a thickness of less than 2cm, preferably less than 1.5cm.

During application of the compressive force in step (b) , a force may be applied to the wall of the pipe to cause it to move through a distance of at least lmm, preferably at least 5mm, especially at least lcm.

Preferably, in the method, force arranged to reduce the outer diameter in step (b) is applied substantially symmetrically to the selected pipe.

Said pipe selected in step (a) preferably has an outer diameter of at least 2.5 cm, more preferably at least 4cm, especially at least 5cm. The outer diameter is preferably less than 30cm, more preferably less than 25cm. Said pipe may have an outer diameter in the range 10 to 15 cm.

Said pipe selected in step (a) may be arranged to exhibit regions having different levels of crystallinity. For example, a first region towards the outside of the pipe may have a lower level of crystallinity compared to a

second region inwards of said first region. Said first region may be substantially amorphous and said second region may be semi-crystalline. Said pipe may include an outer skin which defines an outer surface of the pipe, wherein said outer skin has a lower level of crystallinity compared to a region of the pipe inwards of said outer skin. Said outer skin may be amorphous. Suitably, said pipe includes semi-crystalline regions and, preferably, is substantially entirely semi-crystalline, inwards of said outer skin. A pipe having lower levels of crystallinity, for example amorphous regions as described may be more easily expanded in step (d) compared to a pipe which is semi-crystalline across substantially its entire extent.

The ratio of the wall thickness to diameter ratio of a pipe selected for compression may be less than 0.06, preferably less than 0.05, more preferably less than 0.04. The ratio may be at least 0.01, suitably at least 0.02, preferably at least 0.025.

Said pipe is preferably substantially annular.

The pipe preferably include a substantially smooth outer surface; preferably along substantially its entire extent.

Preferably, substantially all points on an outwardly facing circumferential surface of the pipe are substantially equidistantly spaced from the centre about which the circumferential surface is defined.

The outer diameter of the pipe is preferably substantially constant for substantially all points on the outer wall of the pipe. Preferably, the outer diameter is substantially

constant along substantially the entire extent of the pipe.

Said selected pipe may have a length (or maximum dimension) of at least Im, suitably at least 5m, preferably at least 10m, more preferably at least 50m, especially at least 100m. In some cases, the pipe may be even longer, for example 200m or greater.

In the method, the outside diameter of the pipe may be reduced by 5-15%, for example 10-15%, in step (a) . Thus, the ratio of the outside diameter of said selected pipe to that of said compressed pipe may be at least 1.05, preferably at least 1.1. The ratio may be less than 0.3, preferably less than 0.25, more preferably less than 0.2.

In step (b) of the method, with said selected pipe at a temperature of less than 120°C, suitably less than 100 ⁰ C, preferably less than 80°C, more preferably less than 50°C, especially less than 35 ⁰ C, said selected pipe may be subjected to, for example contacted with, a compression means to compress the pipe and produce said compressed pipe. Preferably, said selected pipe is initially contacted with a said compression means when said selected pipe is at a temperature of less than 80 ⁰ C, preferably less than 50 ⁰ C, more preferably less than 35°C. Suitably, the temperature of said selected pipe when it is subjected to, for example initially contacted with, said compression means is less than 8O ⁰ C, preferably less than 50 ⁰ C, more preferably less than 35 ⁰ C. Said temperature may be greater than 0 ⁰ C, preferably greater than 10 ⁰ C, more preferably greater than 15°C. Advantageously, the selected pipe may be at ambient temperature when it is

subjected to and/or initially contacted with said compression means and suitably therefore no heat from any external heat source need be supplied.

The temperature of the selected pipe may rise as mechanical work is done on it during compression. Preferably, the temperature does not rise to within 20°C, preferably does not rise to within 40°C, of the Tg of said polyetheretherketone (i.e. Tg=143°C) .

After removal of a force used to compress the selected pipe, the compressed pipe may advantageously not need to be subjected to active cooling; it may simply be subjected to ambient temperature.

Suitably, after compression in step (b) and prior to step (c) of the method, said compressed pipe is subjected to (and may be held at) a temperature (hereinafter referred to as "said post-compression temperature") of less than 50°C, preferably less than 40 ⁰ C, more preferably less than 35 ⁰ C. The post-compression temperature may be greater than 0 ⁰ C, preferably greater than 10 ⁰ C, more preferably greater than 15°C. Advantageously, the post-compression temperature may be ambient temperature. The selected pipe may be maintained at said post-compression temperature for at least 5 minutes, preferably at least 30 minutes, more preferably at least 1 hour. Said selected pipe may be maintained at said post-compression temperature for more than 13 hours. It has been found, advantageously, that the compressed pipe may be maintained at said post- compression temperature for one or more days or longer (even weeks or substantially indefinitely) and this may allow selected pipes to be compressed to produce

compressed pipes which may even be stored before being used in step (c) of the method. Compressed pipes could be produced at a factory and transported to a location wherein they may be used.

The time between the end of step (b) and the end of step

(c) (i.e. the time at which the compressed pipe is in its intended position in the casing) may be at least 15 minutes, 30 minutes, 1 hour, 2 hours, 5 hours or more. In some cases, for example where the compressed pipe is stored prior to use in step (c) it may be more than 12,

24, 36 or 48 hours.

Advantageously, said compressed pipe may be maintained in its compressed state under the temperature conditions and/or for the time as aforesaid due to intrinsic properties of said polyetheretherketone.

Said selected pipe may be maintained substantially in its compressed state provided its temperature does not rise above a relevant glass transition temperature of said polyetheretherketone, for example the glass transition temperature of said polyetheretherketone. Thus, the method preferably includes the step, between steps (b) and (c) , of maintaining the temperature of the compressed pipe below 143°C.

Thus, suitably, one or a plurality of properties inherent in said compressed pipe is sufficient, whilst said pipe is below its Tg, to maintain the compressed pipe in its compressed state. Preferably, after the end of step (b) and before step (c) (i.e. suitably after removal of said compression means when provided) the compressed pipe is

maintained in its compressed state by one or a plurality of properties inherent in said compressed pipe. Preferably, between steps (b) and (c) , no outside force (e.g. no physical force such as a tension or compression force applied by a force applying means) is applied to said compressed pipe to restrict it from expanding, for example to restrict it from reverting to (or moving towards) the form and/or size of the pipe selected in step (a) .

The selected pipe may be swaged in step (b) of the method thereby to produce a compressed pipe (which may be selected in step (b*) . This may include a step of forcing the pipe selected (suitably, a circular cross-section pipe) through an opening, suitably a circular opening, which has a diameter which is less than the outer diameter of the pipe. A mouth of the opening which defines an inlet of the opening preferably tapers inwardly to facilitate location and passage of the pipe through the opening. The pipe is suitably compressed as it is forced through the opening. Preferably, the step of forcing the pipe through the opening includes the application of a force to the pipe in the direction of the longitudinal axis of the pipe. The pipe may be pushed or pulled through the opening to apply said force or a combination of pushing and pulling may be used. Upstream of the opening the pipe may be supported on a carrier, for example a spool (or the like) and unwound from the spool for passage through the opening. A length of pipe of at least 5m, preferably at least 10m, more preferably at least 25m, more preferably at least 50m, especially at least 100m may be swaged in step (b) . Downstream of the

opening, the compressed or swaged pipe may be supported on a carrier, for example wound round a spool (or the like) .

In step (c) , the compressed pipe may be manipulated to engage the casing. During step (c) , preferably during the entirety of step (c) , the temperature of the compressed pipe does not rise above 143°C. Thus, suitably, the compressed pipe may be positioned whilst it is in a fixed configuration and/or is not expanding and/or changing its size and/or shape.

In step (d) , said compressed pipe preferably expands back towards the shape and/or size of said selected pipe. It preferably expands so that it fits tightly within the casing.

In step (d) , the conditions to which the compressed pipe may be subjected may be either one or a combination of an increase in temperature or application of internal pressure and/or compressive loading of the pipe along its axis. Where temperature is increased, it may be increased by at least 10 ⁰ C, at least 20°C, at least 30 ⁰ C or at least 40°C. The temperature is suitably not increased to more than 193 ⁰ C. Where pressure is applied, at least 200psi, suitably at least 500psi, preferably at least 750psi may be used. The pressure may be less than 5000psi, preferably less than 2500psi. Where axial compressive loading is used, the loads applied need to be below the compressive strength of the material. Where axial compressive loads are applied, the applied compressive stress should preferably be between 2500psi and lOOOOpsi and more preferably be between 5000psi and 7500psi. The

effect of any one condition is to reduce the level of the other conditions that need to be used.

In general terms, the lower the temperature is relative to the Tg of polyetheretherketone in step (d) the higher the pressure and/or axial compressive loading which may be required to cause appropriate expansion of the compressed pipe. If the temperature is raised to (or above) the Tg of the polyetheretherketone, there may be no need to apply pressure and/or axial compressive loading as aforesaid.

When the temperature is increased in step (d) , a heating means is preferably provided and suitably is arranged to direct heat to the compressed pipe from a position within the pipe. Suitably, heating means comprises a heated fluid.

Where the pressure is increased in step (d) , a pressure applying means is preferably provided and suitably is arranged within the pipe to direct a pressure from a position within the pipe outwardly. Suitably, the pressure applying means comprises a fluid.

The same fluid may be used to apply both heat and pressure to the pipe.

Axial compressive loads can be applied by loading the upper and lower extremities of the pipe. In a downhole application this could be achieved by fitting a packer into the well, locating the pipe on top of the packer and then loading the top of the pipe.

In general terms, in the case where the pipe has not been taken beyond its elastic limit (yield point) during step (b) , heat alone may be sufficient to bring about expansion in step (d) . In this case raising the pipe to a temperature at or close to the T _g of the polyetheretherketone would allow the elastic frozen-in residual stress to recover and the pipe to expand.

Where permanent deformation has occurred, that is the yield stress of the material has been exceeded during step

(a) then the application of heat, pressure and/or axial compressive loading may be necessary to bring about the expansion of the pipe in step (d) . The expansion will be based on any residual recoverable stress and generating a high enough stress in the material to ensure that it yields. The yield stress of a polymer will be a function of temperature, the yield stress generally reducing as the temperature is increased. Thus, the pressure required to achieve expansion will be a function of the temperature of the component and its environment.

For a compressed pipe having an annular cross-section, the required internal pressure to cause expansion in step (d) (without axial compressive loading) can be estimated from the following expression:

2SH

P = D

where : P = estimated pressure to bring about expansion (Pa) D = external diameter of the pipe (m) H = wall thickness (m)

S = yield stress of the material at the temperature concerned (Pa) .

Under these circumstances, any deformation resulting from the expansion and yielding will involve an element of recoverable elastic deformation. It will, therefore, be necessary to maintain the pressure and temperature for a period following the expansion process in order to allow the decay of this recoverable elastic deformation in order to ensure that the pipe retains its expanded dimensions. The period of time that the pressure and temperature need to be maintained will depend on the temperature of the pipe and its environment. The higher the temperature the shorter the period of time required. If the temperature of the polyetheretherketone is above 143°C, then the required time will be very much shorter than the time required if the material is below its T ₉ .

The compressed pipe may be subjected to an internal pressure which is between 80% (preferably at least 90%, more preferably at least 95%, especially at least 100%) and 150% of the pressure estimated to be required using the equation

2SH

P = D

where P, D, H and S are as described above. In general terms, the higher the pressure above that estimated to be required as described, the faster the rate of expansion.

When the compressed pipe includes an outer skin which has lower crystallinity (e.g. it is substantially amorphous)

compared to the crystallinity of regions inwards of said outer skin, the pipe may be more easily expanded compared to a pipe which is substantially wholly semi-crystalline. For example, a pipe with an outer skin as described may relatively easily be expanded using only a suitable temperature and internal pressure.

The ratio of the outer diameter of the compressed pipe produced in step (b) to that of the expanded pipe produced in step (d) may be at least 0.8, preferably at least 0.85. The ratio may be less than 0.95.

The ratio of the outer diameter of the pipe selected before compression in step (b) to that of the expanded pipe produced in step (d) may be in the range 0.9 to 1.1, preferably in the range 0.9 to 1.

Said polyetheretherketone suitably has a melt viscosity (MV) of at least 0.06 kNsm ^"2 , preferably has a MV of at least 0.09 kNsm ^"2 , more preferably at least 0.12 kNsm ^"2 , especially at least 0.15 kNsm ^"2 .

MV is suitably measured using capillary rheometry operating at 400°C at a shear rate of 1000s ^"1 using a tungsten carbide die, 0.5x3.175mm.

Said polyetheretherketone may have a MV of less than 1.00 kNsm ^"2 , preferably less than 0.5 kNsm ^"2 .

Said polyetheretherketone may have a MV in the range 0.09 to 0.5 kNsm ^"2 , preferably in the range 0.14 to 0.5 kNsm ^"2 .

Said polyetherethereketone may have a tensile strength, measured in accordance with ASTM D790 of at least 40 MPa, preferably at least 60 MPa, more preferably at least 80 MPa. The tensile strength is preferably in the range 80- 110 MPa, more preferably in the range 80-100 MPa.

Said polyetherethereketone may have a flexural strength, measured in accordance with ASTM D790 of at least 145 MPa. The flexural strength is preferably in the range 145-180 MPa, more preferably in the range 145-165 MPa.

Said polyetheretherketone may have a flexural modulus, measured in accordance with ASTM D790, of at least 2 GPa, preferably at least 3GPa, more preferably at least 3.5 GPa. The flexural modulus is preferably in the range 3.5- 4.5 GPa, more preferably in the range 3.5-4.1 GPa.

Said polyetheretherketone may consist essentially of a polymer having a repeat unit of formula

According to a another aspect of the invention, there is provided an assembly comprising a polymeric pipe as described in the first or second aspects fitted in a said casing as described in the first or second aspects.

The invention extends to a polymeric pipe comprising a first region towards the outside of the pipe which has a lower level of crystallinity compared to the crystallinity

of a second region inwards of said first region. Said first region is suitably defined by a skin of said pipe.

The level and extent of crystallinity in a polymer is preferably measured by wide angle X-ray diffraction (also referred to as Wide Angle X-ray Scattering or WAXS) , for example as described by Blundell and Osborn (Polymer 2A_ _r 953, 1983) . Alternatively, crystallinity may be assessed by Differential Scanning Calerimetry (DSC) .

The level of crystallinity of said second region may be at least 1%, suitably at least 3%, preferably at least 5% and more preferably at least 10%. In some embodiments, the crystallinity may be greater than 20% or greater than 30%. The difference in the level of crystallinity between said first region and said second region may be at least 5%, preferably at least 10%, more preferably at least 15%, especially at least 20%.

Said first region, for example said outer skin, may be substantially amorphous. Said second region may be crystalline. Preferably substantially the entirety of the material of the pipe inwards of said first region is crystalline.

Any feature of any aspect of any invention or embodiment described herein may be combined with any feature of any aspect of any other invention or embodiment described herein mutatis mutandis.

Specific embodiments of the invention will not be described by way of example with reference to the accompanying drawings, in which:

Figure 1 is a cross-sectional view of a well bore having a casing affixed herein.

Figure 2 is a cross-sectional view of the well bore of Figure 1 showing a casing liner inserted into the casing.

Figure 3 is a cross-sectional view of the casing liner shown inserted into a casing.

Figure 4 is a schematic diagram illustrating, partly in cross-section, apparatus for use in swaging (or reducing the diameter) of a pipe.

Figure 5 is a cross sectional view of the casing liner Figure 4 shown in a reduced condition and inserted in the casing .

Figure 6 is a diagrammatical illustration of a casing liner injector unit.

VICTREX PEEK polymer referred to hereinafter refers to VICTREX PEEK polymer grade 450G obtainable from Victrex PIc of UK.

Referring now to the drawings, and more specifically Figure 1, a typical wellhead 10 utilized in the production of oil and gas from a well is shown. The wellhead 10 includes a casing head 12 which functions to support a casing 14 which is extended down the well to provide a permanent borehole through which production operations may ^¬ be conducted. The casing 14 is shown affixed in a well bore 16 in a conventional manner, such as by cement (not

shown) . The casing 14 is illustrated as having an internal wall 18 defining a flow area.

Figure 2 shows a casing liner 20 inserted in the casing 14. The casing liner 20 is characterized as a polymeric pipe 22 having an upper end 24, a lower end 28, an interior surface 32, and an exterior surface 36. As best shown in Figure 3, the exterior surface 36 of the casing liner 20 is substantially smooth and is in the form of a circular cross-section cylinder.

The casing liner 20 is fabricated from extruded VICTREX PEEK polymer pipe. The pipe is compressible and has sufficient memory so as to permit the material to return to, or at least near to, its original shape under conditions described herein. More specifically, the polymer is compressible in such a manner that the outer diameter of the casing liner 20 can be substantially reduced in size and the memory of the polymer allows the material to rebound after a period of exposure to elevated pressures and/or temperatures experienced downhole. This capability of the diameter of the casing liner 20 to be downsized enables a tubular liner having an outer diameter greater than the inner diameter of the casing 14 to be inserted into the casing 14. Alternatively, a liner having an outer diameter equal to or less than the inner diameter of the casing 14 can be inserted into the casing 14.

The casing liner may be made from an extruded length of pipe made from VICTREX PEEK polymer by reducing the outside diameter of the pipe by swaging. In this regard, referring to Figure 4, a part of a pipe 102 made from

VICTREX PEEK polymer is shown during its passage through an apparatus for swaging (or reducing the diameter of) the pipe. The pipe 102 has an external diameter A prior to passage through a die 104 and an outside diameter C after passage through the die 104.

The die 104 is held in position by means not shown. It tapers inwardly in the direction 105 of travel of the pipe 102 therethrough so as to define a relatively wide mouth for initially receiving the pipe 102, the mouth narrowing to define a minimum diameter B of the die. Upstream of the die 104 are a pair of contra-rotating feed rollers 106 and further upstream are four idler rollers 108. The rollers 108 support the pipe 102 as it is conveyed by the feed rollers 106 to the die 104. Upstream of the idler rollers may be a very long length of pipe (not shown) which may be carried on a spool (or the like) . Downstream of the die 104 are further rollers 110 for facilitating passage of the pipe through the die 104. In use, the pipe 102 is gradually unwound from the spool and forced through the die 104 whereupon its diameter is reduced to diameter

B. After it emerges from the die the pipe has a diameter

C. Diameters B and C are approximately equal, although C may be slightly greater than diameter B if the pipe relaxes slightly after passing through the die. In any event diameter C is less than diameter A, for example by about 10%.

The pipe 102 need not be subjected to an external heating means prior to or during passage through the die and need not be subjected to a cooling means after passage through the die. Thus, treatment of the pipe may be undertaken at ambient temperature.

The glass transition temperature of VICTREX PEEK polymer is 143°C. Provided the reduced diameter pipe produced as described is not heated to a temperature approaching the glass transition temperature and provided the pipe is not subjected to a significant internal pressure, the pipe will remain at its reduced diameter C substantially indefinitely and certainly for days and weeks after its production. A reduced diameter pipe may therefore be manufactured at a factory and it may be wound on a spool or other carrier prior to being transported to a place wherein it may be used. A length of pipe may then be cut from that on the spool as may be required.

For a casing 14 having an outer diameter of about 14cm and an inner diameter of about 12.6cm, an extruded VICTREX PEEK polymer pipe having (before swaging) an outer diameter of about 12cm to about 13.3cm might be used to line the casing 14 depending on whether a tight, neutral or loose fit is desired.

A casing liner 20 made from a length of reduced diameter pipe 102 as described may be fitted in position within casing 14 as described hereinafter. Once in position as represented in Figure 5, the liner 20 is caused to expand so its exterior surface 36 is urged against the inner wall 40 of the casing 14 so the liner 20 becomes an interference fit within the casing 14. The means of expansion may be selected on a case by case basis which may depend on the conditions under which pipe 102 was compressed initially, its wall thickness and diameter, the time available to complete the expansion and the availability of means for heating the pipe, for example

from within. Different expansion processes may be as follows:

(i) When the pipe 102 was not compressed beyond its elastic limit (yield point) during swaging, expansion of liner 20 may be achieved by use only of heat. Thus, heat may be applied (in the absence of any means for pressurizing the pipe) to increase the temperature of the liner to its Tg or above. At or about the Tg, the elastic frozen-in stress in the liner is able to recover and the liner will expand.

(ii) When permanent deformation of the pipe 102 occurred during its compression (i.e. when the yield stress of the VICTREX PEEK polymer was exceeded during compression) , then heat and pressure may be used to cause expansion.

The pressure required may be given by equation

where :

P = estimated pressure to bring about expansion (Pa) D = external diameter of the pipe (m) H = wall thickness (Pa)

S = yield stress of the material at the temperature concerned (Pa)

As an example, the pressure required to expand a 100mm outside diameter polyetheretherketone pipe with a 5mm wall thickness would be:

- 12.5MPa at room temperature

- 7MPa at 100 ⁰ C

- 4.5MPa at 150 ⁰ C

When using VICTREX PEEK to manufacture a pipe as described, the pipe may be manufactured so that it is substantially crystalline throughout its extent or it may be manufactured to have an amorphous skin on the outside of a crystalline internal region. A pipe which is substantially crystalline throughout may be made by extruding the VICTREX PEEK to form a pipe and cooling the polymer following extrusion at a rate which is sufficiently slow to allow the crystallisation process to occur such that a sufficiently high level (e.g. 25 to 35%) crystallinity is achieved. A pipe which has an amorphous skin may be produced by cooling the outside of the extruded pipe quickly so that there is insufficient time for crystallisation in the outer regions of the pipe. A pipe which is substantially crystalline throughout is generally more resistant to expansion and, accordingly a suitable combination of temperature, internal pressure and an axial compressive load may be used to expand the pipe. A pipe which has an amorphous skin may be more easily expanded and this may be achieved using a suitable temperature and internal pressure.

An example of axial compressive, internal pressure and temperature that produce satisfactory expansion results with an amorphous skinned pipe would be:

Pipe diameter 4.2" SDR 28 Internal pressure = 800psi Axial compressive load = 120001b

Temperature = 175 ⁰ F

Referring now to Figure 6, an injector unit 60 constructed for both reducing the diameter of a VICTREX PEEK polymer pipe, such as a coiled polymeric pipe 62, and injecting it into the casing 14 in order to form the casing liner 20

(Figure 2) is schematically illustrated. The injector unit

60 includes a reel 64 for handling and storing the coiled polymeric pipe 62 and a roller reduction unit 66 for directing the pipe 62 into the casing 14, reducing the diameter of the pipe 62 to the desired diameter, and injecting the reduced pipe 62 into the casing 14 to form the casing liner 20. A conventional workover rig 68 is also utilized in the process of positioning the pipe 62 in the casing 14. As an alternative to the workover rig 68, other lifting and supporting structures, such as a crane, can be employed. The reel 64 includes a spool 70 rotatably mounted to a frame 72. The frame 72 is set on a suitable support surface such as the ground, a trailer, or offshore platform deck.

The roller reduction unit 66 is supported above the wellhead 10 by a support structure 74. The workover rig 68 is also connected to the roller reduction unit 66 so as to cooperate with the support structure 74 to support the roller reduction unit 66 above the wellhead 10. The connection of the workover rig 68 to the roller reduction unit 66 further facilitates the rigging up and the rigging down of the roller reduction unit 66 by enabling the roller reduction unit 66 to be moved from a trailer (not shown) to its position over the wellhead 10 and back to the trailer once the injection process is completed.

The roller reduction unit 66 includes a guide wheel 80 and a support frame 82. The support frame 82 supports several banks of rollers 84, 86, 88, 90, 92, and 94 which are each journaled to the frame 82. The rollers in each bank 84-94 are arranged to form a substantially circular passageway through which the pipe 62 is passed. Each subsequent bank of rollers 86-90 from the upper end to the lower end provides the passageway with a diameter smaller than the diameter provided by the previous bank of rollers 84 thereby cooperating to form a substantially frusto- conically shaped passageway such that the outer diameter of the pipe 62 will be gradually reduced as the pipe 62 is passed therethrough. As stated above, the banks of rollers 84-90 can be set up to reduce the outer diameter of the pipe 62 in a range of from 0 to about 25%. The portion of the passageway formed by the banks of rollers 92 and 94 provide the passageway with a diameter that is the same size as the portion of the passageway formed by the banks of roller 90 and thus the banks of rollers 90, 92, and 94 are adapted to frictionally engage the reduced pipe 62 to provide the thrust to snub the reduced pipe 62 into the casing 14 and to control the rate of entry into the casing 14. To this end, each bank of rollers 84-94 is controlled by a hydraulic motor (not shown) . The hydraulic motors are used to control the insertion rate of the pipe 62 into the casing 14 with respect to injection, as well as braking of the pipe 62.

The roller reduction injector unit 66 is supported in an elevated position above the wellhead 10 with support structure 74 which can include a plurality of telescoping legs or other suitable device such a hydraulic jack stand. It should be noted that the roller reduction injector unit

66 should be elevated sufficiently above the wellhead 10 to permit access to the wellhead 10 during the pipe injection process and to accommodate additional equipment, such as a blow out preventer 96.

Roller reduction units as briefly described above are well known in the art. Thus, no further description of their components, construction, or operation is believed necessary in order for one skilled in the art to understand the unit.

Regardless of the manner in which the polymeric pipe 62 is injected into the casing, the pipe 62 should remain in a reduced state as the pipe 62 is being injected into the casing 14 and until the pipe 62 is set at the desired depth. As described above, a casing liner made from VICTREX PEEK polymer as described may remain in its reduced diameter state substantially indefinitely when its temperature is less than its Tg and when it is not subjected to significant internal pressure. Thus, in use, there may generally be no time pressure for positioning the liner in position.

Before the pipe 62 is inserted into the casing 14 to provide the casing liner 20, the casing 14 is cleaned with a brush or scrapper to remove debris such as cement. The well is then killed by injecting KCl, inserting a bridge plug downhole, or other methods of killing a well. The pipe 62 is then fed over the guide wheel 80 and into the roller reduction unit 66. The roller reduction unit 66 is operated to inject the pipe 62 into the casing 14, as illustrated in Figure 6. After the pipe 62 is run a distance into the casing 14, the roller reduction unit 66

is operated as a braking system to control the rate of descent of the pipe 62 due to the weight of the pipe 62.

Once the pipe 62 is run to the desired depth in the casing 14, the pipe 62 is caused to expand into position against the casing 14 thereby effectively lining the casing 14. Next, the pipe 62 is cut and fused to a flange which is, in turn, attached to the wellhead 10.

Expansion of the pipe 62 to its final position may be achieved by exposure to elevated downhole temperature and pressure. Alternatively, expansion of the pipe 62 can be induced by exposing the pipe 62 to an appropriate high temperature and/or pressure. This can be achieved by circulating a hot, optionally pressurized, fluid through the pipe 62 after the pipe 62 is inserted and flanged to casing 14.

As an alternative to the use of the complete apparatus of Figure 6, only part of the apparatus will be required if a liner pipe is prepared off-site and transported in a reduced state to the well-head. This may save significant costs associated with the use of apparatus.