Apparatus and method for lining a downhole casing

A casing liner and method for lining a casing affixed in a well bore. The casing liner having a plurality of grooves and ridges arranged longitudinally and in an alternating relationship about the exterior surface of the casing liner to increase stress storage upon the casing liner being radially reduced in size and thereby decrease the expansion rate of the casing liner and facilitate installation of the casing liner into the casing.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liner for a well bore, and more particularly, but not by way of limitation, to an improved apparatus and method for lining a casing affixed within a well bore.

2. Brief Description of Related Art

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 through 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. This method is disclosed in U.S. Pat. No. 5,454,419, issued to Jack Vloedman. The method disclosed in the Vloedman '419 patent utilizes a continuous, smooth walled polymeric 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.

While the method disclosed in the Vloedman '419 patent has successfully met the need for lining and repairing breaches in a casing in an effective and time efficient manner, several inefficiencies have nevertheless been encountered, particularly when attempting to line a casing at depths below about 5,000 feet. In attempting to line a casing at depths below about 5,000 feet, the weight of the weight system coupled with the weight of the liner being run into the casing can cause the liner to plastically deform and exceed the yield strength resulting in permanent deformation.

SUMMARY OF THE INVENTION

The present invention is directed to a liner for lining a casing affixed within a well bore. The liner includes a polymeric pipe having a wall with an inner diameter, an outer diameter, an interior surface, and an exterior surface. The exterior surface of the pipe is provided with a plurality of 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.

The present invention is further directed to a liner for a well bore casing wherein the liner includes a polymeric tube having a wall with an inner diameter, an outer diameter, and an exterior surface having a plurality of alternating grooves and ridges extending longitudinally of the exterior surface and defining a substantially sinusoidal profile around the periphery of the exterior surface.

In another aspect, the present invention is directed to a method for lining a casing affixed within a well bore by reducing the outer diameter of a polymeric pipe having a wall with a plurality of ridges and grooves by applying radial compressive forces to the ridges so that the outer diameter of the polymeric pipe is less than the inner diameter of the of the casing. The application of compressive forces to the ridges 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 delaying expansion of the polymeric pipe for a period of time. The reduced pipe is then passed into the casing to a predetermined depth. The stored stress of the reduced pipe is released so that the reduced pipe expands against the inner wall of the casing.

The present invention is also directed to a method for lining a casing affixed within a well bore by reducing the outer diameter of a polymeric pipe having a plurality of ridges and grooves by applying radial compressive forces to the ridges of the polymeric pipe and passing the reduced pipe, free of added weight on a lower end of the reduced pipe, into the casing to a predetermined depth such that the reduced pipe is void of longitudinal tension except for the tension placed on the reduced pipe by the weight of the polymeric pipe itself. The reduced pipe is then allowed to expand against the inner wall of the casing so that the ridges of the exterior surface of the polymeric pipe engage the internal wall of the casing.

Still yet, the present invention is directed to a method for lining a well bore casing by reducing the outer diameter of a tube having a plurality of alternating ridges and grooves extending longitudinally of the outersurface and defining a substantially sinusoidal profile around the periphery of the exterior surface by applying a compressive force to the outer wall sufficient to reduce the outer diameter of the tube between the elastic limit and the ultimate strength of the tube. The reduced tube is then passed into the well bore casing and permitted to expand toward the inner wall of the casing.

The objects, features, and advantages of the present invention will become apparent from the following detailed description when read in conjunction with the accompanying drawings and appended claims.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, and more specifically toFIG. 1, a typical wellhead10utilized in the production of oil and gas from a well is shown. The wellhead10includes a casing head12which functions to support a casing14which is extended down the well to provide a permanent borehole through which production operations may be conducted. The casing14is shown affixed in a well bore16in a conventional manner, such as by cement (not shown). The casing14is illustrated as having an internal wall18defining a flow area.

FIG. 2shows a casing liner20inserted in the casing14in accordance with the present invention. The casing liner20is characterized as a polymeric pipe22having an upper end24, a lower end28, an interior surface32, and an exterior surface36. As best shown inFIG. 3, the exterior surface36of the casing liner20is provided with a plurality of grooves40and ridges44. More specifically, the ridges44of the exterior surface36of the casing liner20provide a contact area along the exterior surface36of the casing liner20that frictionally engages the internal wall18of the casing14while the grooves40of the exterior surface36of the casing liner20cooperate with the internal wall18of the casing14to form a plurality of cavities48.

The casing liner20is fabricated of a tubular polymeric material which is compressible and has sufficient memory so as to permit the material to return to, or at least near to, its original shape after the compressive and tensile forces imparted by the casing liner installation process are removed from the material. More specifically, the tubular polymeric material is compressible in such a manner that the outer diameter of the casing liner20can be substantially reduced in size and the memory of the tubular polymeric material allows the material to rebound after a period of exposure to elevated pressures and temperatures experienced downhole. This capability of the diameter of the casing liner20to be downsized enables a tubular polymeric material having an outer diameter greater than the inner diameter of the casing14to be inserted into the casing14. Alternatively, a tubular polymeric material having an outer diameter equal to or less than the inner diameter of the casing14can be inserted into the casing14. As such, the outer diameter of the casing liner20preferably should be capable of being reduced up to about 25%. It will be understood that the reduction percentage must be sufficient to allow clearance and insertion of the casing liner20into the casing14. Furthermore, the reduction percentage should be such that the casing liner20remains substantially in a reduced state during insertion into the casing14and then expands once the casing liner20is disposed at the desired depth within the casing14. It will be understood that the reduction percentages and preferred range can vary depending on the material used to fabricate the casing liner20.

When forming the casing liner20from a tubular polymeric material having an outer diameter greater than the inner diameter of the casing14, the memory of the polymeric material causes the casing liner20to expand within the casing14such that the ridges44of the exterior surface36of the casing liner20presses against the internal wall18of the casing14. Because the original outer diameter of the tubular polymeric material is greater than the inner diameter of the casing14, the ridges44of the exterior surface36of the expanding tubular polymeric material presses tightly against the casing14and forms a plurality of frictionally engaged braces against the casing14while the grooves40of the exterior surface36of the expanding tubular polymeric material cooperate with the internal wall18of the casing14to form the plurality of cavities48. Furthermore, the amount of polymeric material used in fabricating the casing liner20is reduced, thereby reducing the amount of material needed to form the casing liner20while the outer diameter of the casing liner20is effectively maintained. The casing liner20remains capable of expanding and engaging the internal wall18of the casing14while decreasing the weight of the casing liner20that is supported by the frictionally engaged braces against the casing14. To this end, the casing liner20is secured against the casing14without the use of adhesives which have generally proven to be ineffective in downhole environments. Further, removal of the casing liner20from the casing14, if necessary, is facilitated by the reduced area of contact between the casing liner20and the casing14.

The thermal insulating property of the tubular polymeric material depends on the composition, thickness, and shape of the polymeric material. These factors limit the heat conduction area in contact with the casing wall. In particular, the cavities48increase the thermal insulating property of the tubular polymeric material so long as the cavities48are filled with a fluid that has less thermal conductivity than the tubular polymeric material itself. To this end, the plurality of cavities48formed by the grooves40of the exterior surface36of the casing liner20and the internal wall18of the casing14alter the thermal insulating property of the casing liner20installed in the casing14. Due to the low coefficient of heat transfer for fluid accumulated in the cavities48, the cavities48limit the heat conduction area of the casing liner20that is in contact with the casing14. However, it should be appreciated that in instances where heat loss is tolerated, the casing liner20of the present invention can be utilized irrespective of the formation of cavities48between the grooves40of the exterior surface36of the casing liner20and the internal wall18of the casing14. For example, the casing liner20can be utilized as a velocity string.

While the casing liner20of the present invention is described herein as serving as a thermal insulator when used alone within the casing14, it will be recognized that the casing liner20is not limited to being used alone to thermally insulate the casing14. For example, the casing liner20can be used in combination with a downhole heater to thermally insulate the casing14.

The expansion rate of the casing liner20is a function of thermal expansion and stored stress in the polymeric material that results from reduction of the outer diameter of the casing liner20. The storage of stress and the amount of stored stress is a function of the strength and shape of the polymeric material, temperature, and the extent of the induced reduction. To alter the expansion rate of the polymeric material of the casing liner20, the grooves40and the ridges44of the exterior surface36of the casing liner20are arranged in an alternating relationship about the circumference of the exterior surface36of the casing liner20. As best shown inFIG. 4, the grooves40and the ridges44of the exterior surface36of the casing liner20are curved and form a substantially sinusoidal profile about the circumference of the exterior surface36of the casing liner20. Such a profile results in the grooves40and the ridges44being shaped and dimensioned substantially similarly to each other and each of the ridges44being contiguous to the adjacent ridges44whereby the outer diameter of the casing liner20can be reduced so that the stress induced to the casing liner20during reduction can be stored, and later released while minimizing the amount of reduction necessary to maintain the casing liner20in the reduced state. To avoid inflicting undue stress to the ridges44during the reduction process, the casing liner20is formed so that the ridges44are truncated to provide the ridges44with a substantially flat end surface45.

FIG. 4Aillustrates the casing liner20in a reduced state and inserted in the casing14. The alternating arrangement of the grooves40and the ridges44along the exterior surface36of the casing liner20result in the wall of the casing liner20having a non-uniform thickness. The application of radially compressive forces to the ridges44during the installation process creates point loads that deform the casing liner20non-uniformly due to the non-uniform thickness of the casing liner20. More particularly, the portions of the casing liner20corresponding to the lowest point of the grooves40are the thinnest portions of the casing liner20, and the portions of the casing liner20corresponding to the peak of the ridges44are the thickest portions of the casing liner20. Upon the application of radially compressive forces to the ridges44, the thinner portions of the casing liner20deform to a greater degree than the thicker portions of the casing liner20, as best illustrated inFIG. 4Bby the formation of internal ridges47on the internal surface32of the casing liner20. The internal ridges47correspond to the thinner portions of the casing liner20.

To decrease the expansion rate of the reduced casing liner20, the casing liner20is reduced by the application of compressive forces on the casing liner20sufficient to deform the casing liner20between the elastic limit and the ultimate strength of the casing liner20. The elastic limit is defined herein as being the amount of stress that will cause permanent or semi-permanent set to a material. The ultimate strength is defined herein as being the maximum stress a material can sustain before rupture calculated on the basis of the ultimate load in original or unstrained dimensions. By deforming the casing liner20between its elastic limit and ultimate strength, the casing liner20is caused to hold its reduced size and shape. However, upon exposure for a period of time to elevated temperatures and internal pressures encountered in a downhole environment or axial compression or mechanical swedging, the stresses in the casing liner20are released, and the casing liner20is caused to rebound toward its original shape and size. It will be understood that the elastic limit and the ultimate strength vary depending on the material used to form the casing liner20, as well as the shape and thickness of the sidewall of the casing liner20. Therefore, the amount of radial reduction required to the casing liner20to delay expansion of the casing liner20is a function of the type of material used to form the casing liner20and the size and shape of the casing liner20.

For example, a casing having an outer diameter of 5.5 inches has an inner diameter of approximately 4.95 inches. As such, a casing liner having an outer diameter of 4.75 to 5.25 inches might be used to line the casing depending on whether a tight, neutral, or loose fit is desired. Assuming the casing liner has a shape as shown inFIG. 4, an outer diameter of 5.25 inches and a wall thickness of 0.35 inches (at the grooves) and is fabricated of a crosslinkable polyethylene, such as commercially available from Solvay and sold under the trademark ChemPEX®, the outer diameter of the casing liner would be reduced at least 13% to set the shape of the casing liner so that it may be inserted into the casing. However, a casing liner having a shape as shown inFIG. 4, an outer diameter of 5.25 inches and a wall thickness of 0.25 inches (at the grooves) and fabricated of a modified nylon six, such as commercially available from Honeywell and sold under the trademark CAPRON®, would require reduction of approximately 18-20% to set the shape of the casing liner so that it may be inserted into the casing.

The non-uniform deformation of the casing liner20that results from the grooves40and the ridges44of the exterior surface36of the casing liner20allows for more storage of stress in the polymeric material than is possible with a smooth wall liner of similar internal and external diameter and which is reduced approximately the same percentage. Without deforming the entire liner beyond its elastic limit, a smooth wall liner expands or rebounds too rapidly to allow it to be inserted into a well bore to great depths without the use of weights to keep the smooth wall liner in tension so that the outer diameter of the smooth wall liner remains reduced during insertion of the smooth wall liner into the well bore. However, because a smooth wall liner of comparable inner and outer diameter to the casing liner20has a uniform thickness, and thus a greater cross-sectional area than the casing liner20, a greater compressive force is required to deform the smooth wall liner beyond its elastic limit than that required to deform the casing liner20beyond its elastic limit. Consequently, deforming a smooth wall liner beyond its elastic limit so that the smooth wall liner will hold its reduced shaped requires a greater percentage of reduction than that required of the casing liner20. The problem encountered is that a smooth wall liner reduced sufficiently to hold its shape without the use of weight may not expand adequately to provide the desired internal flow area or to frictionally engage the casing even after exposure to elevated temperatures and pressures or the application of axial compressive forces. To this end, the increased stored stress in the polymeric material due to the formation of the grooves40and the ridges44on the exterior surface36of the casing liner20decreases the expansion rate and provides sufficient time to insert the casing liner20into the casing14, and yet allows the casing liner20to adequately expand after it has been positioned at the desired depth within the casing14and exposed to elevated downhole temperatures, pressures, or mechanical forces, thereby eliminating the need of weights to keep the polymeric material in tension. As such, the added complexities and inherent dangers associated with using weights when inserting a tubular polymeric material into the casing14of the well bore16are eliminated.

While the casing liner20of the present invention is described herein as being insertable into the casing14without the use of weights, it will be recognized that the casing liner20is not limited to being inserted into the casing14without the use of weights. The casing liner20can be inserted into the casing14with the use of weights as disclosed in U.S. Pat. No. 5,454,419 issued to Jack Vloedman on Oct. 3, 1995, which is hereby expressly incorporated herein by reference, or any other applied axial loads that keep the polymeric material in tension while the casing liner20is being inserted into the casing14, and then allowed to subsequently expand by releasing the applied tension loads. Furthermore, it will be recognized that in addition to expanding the casing liner20by releasing the applied tension loads, the casing liner20may also be expanded by action of temperature and internal pressure or mechanical tools, such as a device known as a swedge.

In one embodiment, the grooves40and the ridges44of the exterior surface36of the casing liner20extend longitudinally between the upper end24of the casing liner20and the lower end28of the casing liner20and are arranged such that the cavities48that result when the casing liner20is disposed and expanded in the casing14(FIG. 3) provide at least one continuous conduit52extending between the upper end24of the casing liner20and the lower end28of the casing liner20so that a fluid can flow between the upper end24of the casing liner20and the lower end28of the casing liner20. The continuous conduit52provides for convenient transport of well treatment fluids, such as soap, or equipment, such as sensors, down the casing14to the well reservoir without using the flow area of the casing liner20.

The longitudinal arrangement of the grooves40and the ridges44ensures that the plurality of grooves40and the ridges44along the exterior surface36of the casing liner20do not adversely effect the tensile strength of the tubular polymeric material. While the grooves40and the ridges44of the exterior surface36of the casing liner20of the present invention are described herein as being arranged such that the grooves40and the ridges44of the exterior surface36of the casing liner20extend longitudinally between the upper end24of the casing liner20and the lower end28of the casing liner20, it will be recognized that the grooves40and the ridges44are not limited to a longitudinal arrangement. The grooves40and the ridges44may be arranged in any direction, so long as the grooves40and the ridges44do not adversely affect the tensile strength of the tubular polymeric material and provide for cavities and frictional engagement. For example, the grooves40and the ridges44of the exterior surface36of the casing liner20could extend helically between the upper end24of the casing liner20and the lower end28of the casing liner20.

Referring now toFIG. 5, the casing liner20is shown inserted into a casing14a. As mentioned above, the casing liner20of the present invention is not limited to having an outer diameter greater than the inner diameter of the casing. That is, the casing liner20may have an outer diameter substantially equal to the inner diameter of the casing14ain which case the casing liner20may have a neutral fit with respect to the casing14a, or the casing liner20may have an outer diameter less than the inner diameter of the casing14ain which case the casing liner20may have a loose fit with respect to the casing14a. In either case, the casing liner20is preferably downsized to facilitate insertion of the casing liner20into the casing14a. The reduction percentage should be such that the casing liner20remains substantially in a reduced state during insertion into the casing14aand then substantially expands once the casing liner20is disposed at the desired depth within the casing14a. Because the casing liner20has an initial diameter equal to or less than the inner diameter of the casing14a, the casing liner20can generally be inserted to greater depths without the use of weights and without concern that the casing liner20will expand prematurely so as to impede insertion of the casing liner20.

When positioned at the desired depth, the casing liner20may expand to engage the casing14adue to thermal expansion and the effects of internal pressure. However, the engagement may not be sufficient to support the weight of the casing liner20. Accordingly, a flow-through packer or anchor53may be set at the desired depth in the casing14a. The casing liner20is then downsized and inserted into the casing14auntil the casing liner20lands on the packer53. The ridges44of the casing liner20form a stiffer column so that the casing liner20is able to resist compressive loading resulting from the casing liner20resting on the packer53.

Suitable materials for the fabrication of the casing liner20are polyethylene, cross-linked polyethylene, polypropylene, polyamides, polyketones, and copolymers thereof. In addition to the compression and memory characteristics mentioned above, these materials are resistant to abrasion, which enables them to withstand the passage of downhole tools, and are resistant to various chemical and salt water corrosion. These materials are readily shapeable, which allows them to be fabricated such that the interior surface32of the casing liner20is smooth and the exterior surface36of the casing liner20is provided with a plurality of grooves40and the ridges44. Furthermore, these materials can be formed into a long, continuous joint containing no joint connections. Coupling connections in standard steel tubular casings create discontinuities along the flow area of the casing14that result in increased friction and turbulence in the flow of produced fluids. By lining the casing14with a continuous joint of material which is accomplished as a result of the ability of the these materials to be fused, the flow area of the casing14utilized for production is effectively continuous and smooth. The casing liner20can also be fabricated with a predetermined inner diameter. As the pressure in a well reservoir depletes, there may be insufficient velocity to transport all liquids from the well bore16thereby impairing production. By lining the casing14with a pipe made from these materials or others with an inner diameter that reduces the flow area of the casing14being utilized for production, the flow velocity of the casing14is effectively increased thereby enabling liquids to be transported from the well bore16.

While these materials are described herein as the materials of preference for the fabrication of the casing liner20of the present invention, it will be recognized that the casing liner20is not limited to being fabricated of these materials. The casing liner20can be fabricated of any durable, polymeric material that is capable of withstanding temperatures and pressures typically encountered in oil and gas wells, compatible with produced and treatment fluids, and has compression and memory properties that allow it to be downsized for insertion into the casing14or14aand subsequently permit it to expand to near its original shape.

Referring now toFIG. 6, an injector unit60constructed in accordance with the present invention for injecting a tubular polymeric material, such as a coiled polymeric pipe62, into the casing14in order to form the casing liner20(FIG. 2) is schematically illustrated. The injector unit60includes a reel64for handling and storing the coiled polymeric pipe62and a roller reduction unit66for directing the pipe62into the casing14, reducing the diameter of the pipe62to the desired diameter, and injecting the reduced pipe62into the casing14to form the casing liner20. A conventional workover rig68is also utilized in the process of positioning the pipe62in the casing14. As an alternative to the workover rig68, other lifting and supporting structures, such as a crane, can be employed. The reel64includes a spool70rotatably mounted to a frame72. The frame72is set on a suitable support surface such as the ground (FIG.6), a trailer, or offshore platform deck.

The roller reduction unit66is supported above the wellhead10by a support structure74. The workover rig68is also connected to the roller reduction unit66so as to cooperate with the support structure74to support the roller reduction unit66above the wellhead10. The connection of the workover rig68to the roller reduction unit66further facilitates the rigging up and the rigging down of the roller reduction unit66by enabling the roller reduction unit66to be moved from a trailer (not shown) to its position over the wellhead10and back to the trailer once the injection process is completed.

The roller reduction unit66includes a guide wheel80and a support frame82. The support frame82supports several banks of rollers84,86,88,90,92, and94which are each journaled to the frame82. The rollers in each bank84-94are arranged to form a substantially circular passageway through which the pipe62is passed. Each subsequent bank of rollers86-90from the upper end to the lower end provides the passageway with a diameter smaller than the diameter provided by the previous bank of rollers84thereby cooperating to form a substantially frusto-conically shaped passageway such that the outer diameter of the pipe62will be gradually reduced as the pipe62is passed therethrough. As stated above, the banks of rollers84-90can be set up to reduce the outer diameter of the pipe62in a range of from 0 to about 25%. The portion of the passageway formed by the banks of rollers92and94provide the passageway with a diameter that is the same size as the portion of the passageway formed by the banks of roller90and thus the banks of rollers90,92, and94are adapted to frictionally engage the reduced pipe62to provide the thrust to snub the reduced pipe62into the casing14and to control the rate of entry into the casing14. To this end, each bank of rollers84-94is controlled by a hydraulic motor (not shown). The hydraulic motors are used to control the insertion rate of the pipe62into the casing14with respect to injection, as well as braking of the pipe62.

An alternative for controlling the insertion rate of the pipe62into the casing14, as well as braking of the polymeric pipe62involves the use of an injector head in a manner described in U.S. Pat. No. 5,454,419, issued to Jack Vloedman on Oct. 3, 1995, which is hereby expressly incorporated herein by reference.

The roller reduction injector unit66is supported an elevated position above the wellhead10with support structure74which 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 unit66should be elevated sufficiently above the wellhead10to permit access to the wellhead10during the pipe injection process and to accommodate additional equipment, such as a blow out preventer96.

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 and implement the method of the present invention.

Regardless of the manner in which the polymeric pipe62is injected into the casing, the pipe62must remain in a reduced state as the pipe62is being injected into the casing14and until the pipe62is set at the desired depth. For example, with a reduction percentage of about 25%, the time period for the polymeric pipe62of a specifically designed original outer diameter to rebound is about twelve hours, though one of ordinary skill in the art will understand that this rebound time can vary depending on the depth and bottom hole temperature of the well bore16. Therefore, the polymeric pipe62should be inserted into the casing14such that the pipe62remains substantially reduced during insertion into the casing14and then substantially expands once the pipe62is disposed at the desired depth within the casing14. The insertion time is generally between about four and eight hours once the reduction process begins. However, one of ordinary skill in the art will understand that the rebound time period and insertion time period can vary depending on the depth of insertion, the material, reduction percentage, and environmental temperature of the casing liner20.

Before the pipe62is inserted into the casing14to provide the casing liner20, the casing14is 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 pipe62is then fed over the guide wheel80and into the roller reduction unit66. The roller reduction unit66is operated to inject the pipe62into the casing14, as illustrated in FIG.6. After the pipe62is run a distance into the casing14, the roller reduction unit66is operated as a braking system to control the rate of descent of the pipe62due to the weight of the pipe62.

Once the pipe62is run to the desired depth in the casing14, the pipe62is allowed to expand into position against the casing14thereby effectively lining the casing14. Next, the pipe62is cut and fused to a flange which is, in turn, attached to the wellhead10. Alternatively, if the casing liner20is set on an anchor, such as anchor53, the pipe62can be cut and fused to a flange prior to allowing the pipe62to expand.

As an alternative to allowing the pipe62to expand due to exposure to elevated downhole temperature and pressure, expansion of the pipe62can be induced by exposing the pipe62to an appropriate high temperature based on the characteristics of the material used to fabricate the pipe62. This can be achieved by circulating a hot fluid through the pipe62after the pipe62is inserted and flanged to casing14.

From the above description, it is clear that the present invention is well adapted to carry out the objects and to attain the advantages mentioned herein, as well as those inherent in the invention. While a presently preferred embodiments of the invention have been described for purposes of this disclosure, it will be understood that numerous changes may be made which will readily suggest themselves to those skilled in the art and which are accomplished within the spirit of the invention disclosed and as defined in the appended claims.