Abstract:
A coring apparatus comprises a coring bit operable to cut a core. An outer barrel is coupled to and configured to rotate the coring bit. An inner barrel is disposed within the outer barrel and is isolated from rotation with the outer barrel. A fabric sleeve is disposed within the inner barrel and configured to receive the core cut by the coring bit.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Patent Application Ser. No. 61/542,384, which was filed Oct. 3, 2011. This priority application is hereby incorporated by reference in its entirety into the present application, to the extent that it is not inconsistent with the present application. 
    
    
     BACKGROUND 
     This disclosure relates generally to methods and apparatus for acquiring and analyzing cores from subterranean formations. More particularly, this disclosure relates to methods and apparatus for utilizing an absorbent core barrel assembly to retain fluids that are ejected from a core and methods of analyzing the core and retained fluids. 
     Formation coring is a well-known process for obtaining a sample of a subterranean formation for analysis. In conventional coring operations, a specialized drilling assembly is used to obtain a cylindrical sample of material, or “core,” from the formation and retain that core within a core barrel so that the core can be brought to the surface. Once at the surface, the core can be analyzed to reveal formation data such as permeability, porosity, and other formation properties that provide information as to the type of formation being drilled and/or the types of fluids contained within the formation. 
     In many hydrocarbon-bearing formations, the hydrocarbons are entrained within the formation at high pressures. As a core is being retrieved to the surface, the pressure acting on the core can be reduced and gas entrained in the core can expand and migrate out of the core. The expanding gases can also push formation fluids out of the core. In conventional coring operations, the formation fluids and gases are often lost as the core is retrieved to the surface, thus limiting the analysis that can be performed. 
     One method used to counteract the loss of formation fluids is “sponge coring.” Sponge coring is similar to conventional coring but the coring assembly includes a core barrel that has an annular sponge that surrounds the core as it is acquired. The annular sponge can absorb formation fluid that is expelled from the core and can hold the fluid as the sample is retrieved to the surface. At the surface, the absorbed fluids can be analyzed to provide additional information about formation properties or formation fluids. 
     In conventional sponge coring tools, the sponge material is molded directly into a core barrel, or into a liner that fits into the core barrel. In many applications, an annular mold is formed by placing a cylindrical mandrel, which has a diameter substantially equal to the core to be acquired, inside a cylindrical liner. A liquid material (such as polyurethane), catalyst, and foaming agent are deposited into the mold and react to form a sponge material that fills the mold and hardens. During the molding process, the sponge material adheres to the liner or barrel and forms a non-adhering “skin” on the surface that contacts the mandrel. The mandrel is removed to leave an annular sponge adhered to the liner and having a circular hole through its center having the same diameter as the mandrel. The presence of the skin on the inner surface of the annular sponge limits absorption of fluid into the sponge and therefore requires a separate machining process to remove the skin and provide the necessary internal diameter to accept the core. Consistently and reliably machining the sponge material to the necessary diameter has proven to be a difficult process. 
     Conventional sponge coring tools are also susceptible to damage as the core moves through the annular sponge. In order to properly capture the formation fluid, the annular sponge is machined to an inner diameter that is closely matched to, or even in an interference fit with, the core that is being drilled. As the core moves relative to the annular sponge, the close engagement between the annular sponge and the core can result in the sponge being damaged. Once the sponge is damaged, it can interfere with the acquisition of the core or may lose the ability to effectively absorb fluids from the core and may therefore compromise the analysis sought to be performed. Attempts have been made to reinforce the annular sponge through strengthening members molded into the sponge material or by incorporating a non-absorbent retention mesh into the sponge material, but instances of damage to the annular sponge still occur. 
     The materials and methods used to form conventional sponge coring tools can also create limitations in the use of the technology. For example, the material used to form the annular sponge, often polyurethane foam, can interfere with some analysis, such as determining oil fluorescence using ultraviolet light. Further, conventional annular sponge material also tends to have a non-homogenous cross-section where permeability and absorbability of the material changes through the thickness of the material. 
     Thus, there is a continuing need in the art for methods and apparatus for acquiring and analyzing cores that overcome these and other limitations of the prior art. 
     BRIEF SUMMARY OF THE DISCLOSURE 
     In one embodiment, a coring apparatus can comprise an outer barrel coupled to and configured to rotate a coring bit. An inner barrel is disposed within the outer barrel and is isolated from rotation with the outer barrel. A fabric sleeve is disposed within the inner barrel and configured to receive the core that is cut by the core bit. 
     In another embodiment, a method of manufacturing a coring apparatus comprises coupling a coring bit to an outer barrel and disposing an inner barrel assembly within the outer barrel. The inner barrel assembly comprises a fabric sleeve operable to receive a core cut by the coring bit. 
     In another embodiment, a coring apparatus comprises an inner barrel with a fabric sleeve disposed within the inner barrel. A coring bit disposed proximate to one end of the inner barrel. The coring bit is operable to drill a core having an outer diameter substantially equal to an inner diameter of the fabric sleeve. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more detailed description of the embodiments of the present disclosure, reference will now be made to the accompanying drawings, wherein: 
         FIG. 1  is an partial-sectional schematic view of an exemplary coring assembly including a fabric sleeve; 
         FIG. 2  is a partial sectional view of an exemplary inner barrel liner assembly including a fabric sleeve and an annular sponge with internal supports extending inward from the barrel liner; 
         FIG. 3  is a partial sectional view of an exemplary inner barrel liner assembly including a fabric sleeve and an annular sponge with supports extending through the barrel liner; 
         FIG. 4  is a partial sectional isometric view of an exemplary inner barrel liner assembly including a fabric sleeve mechanically coupled to the liner; and 
         FIG. 5  is a partial sectional isometric view of an exemplary inner barrel liner assembly including an integral fabric sleeve. 
     
    
    
     DETAILED DESCRIPTION 
     It is to be understood that the following disclosure describes several exemplary embodiments for implementing different features, structures, or functions of the invention. Exemplary embodiments of components, arrangements, and configurations are described below to simplify the present disclosure; however, these exemplary embodiments are provided merely as examples and are not intended to limit the scope of the invention. Additionally, the present disclosure may repeat reference numerals and/or letters in the various exemplary embodiments and across the Figures provided herein. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various exemplary embodiments and/or configurations discussed in the various Figures. Moreover, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed interposing the first and second features, such that the first and second features may not be in direct contact. Finally, the exemplary embodiments presented below may be combined in any combination of ways, i.e., any element from one exemplary embodiment may be used in any other exemplary embodiment, without departing from the scope of the disclosure. 
     Additionally, certain terms are used throughout the following description and claims to refer to particular components. As one skilled in the art will appreciate, various entities may refer to the same component by different names, and as such, the naming convention for the elements described herein is not intended to limit the scope of the invention, unless otherwise specifically defined herein. Further, the naming convention used herein is not intended to distinguish between components that differ in name but not function. Additionally, in the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to.” All numerical values in this disclosure may be exact or approximate values unless otherwise specifically stated. Accordingly, various embodiments of the disclosure may deviate from the numbers, values, and ranges disclosed herein without departing from the intended scope. Furthermore, as it is used in the claims or specification, the term “or” is intended to encompass both exclusive and inclusive cases, i.e., “A or B” is intended to be synonymous with “at least one of A and B,” unless otherwise expressly specified herein. 
     Referring initially to  FIG. 1 , an exemplary coring apparatus  10  includes an outer barrel  12 , a coring bit  14 , a core catcher bowl  16 , a core catcher  18 , an inner barrel  20 , and a barrel liner assembly  24 . The coring bit  14  can be any suitable coring drill bit, such as a diamond bit, and is coupled to the outer barrel  12  so that rotation of the outer barrel rotates the coring bit. In operation, the outer barrel  12  can be coupled to a drill string or a drilling motor (not shown) that rotates the outer barrel  12 . The inner barrel  20  is disposed within the outer barrel  12  but does not rotate with the outer barrel  12 . The inner barrel  20  can be coupled to the core catcher bowl  16 , which is at least partially disposed within coring bit  14 . The core catcher  18  can be at least partially disposed within the core catcher bowl  16  and can provide a transition from the inner diameter of coring bit  14  to the barrel liner assembly  24 . 
     The inner barrel  20  houses a barrel liner assembly  24  that fits closely within the inner barrel  20 . The barrel liner assembly  24  can include a liner body  21  and a fabric sleeve  22  that has an inner diameter substantially equal to the diameter of the core drilled by coring bit  14 . The liner body  21  and inner barrel  20  can include orifices  38  that provide a flow path from the inside of the barrel liner assembly  24  to the annulus between the liner body  21  and the inner barrel  20 . Liner body  21  can be a tubular body manufactured from steel, aluminum, plastic, or any suitable material. It is also understood that fabric sleeve  22  can be coupled directly to barrel liner assembly  24  and the liner body  21  can be omitted from the assembly as desired. 
     For the purposes of this description, a fabric sleeve can be any sleeve formed from a material formed from fibers by weaving, knitting, felting, or any other method used to assemble fibers into a substantially homogeneous material. In certain embodiments, fabric sleeve  22  can be formed from a non-woven fabric material such as a felt, needle felt, scrim-supported needle felt, or other non-woven fabric material manufactured from fibers having high tenacity and a long staple. Exemplary non-woven fabric sleeves are manufactured by Andrew Webron Ltd. for use in filtration applications. Fabric sleeve  22  can be a seamless cylinder or may have one or more longitudinal seams that can facilitate removal of the sleeve from the core for analysis. The fabric sleeve  22  can be a singular elongated cylinder or can be manufactured from a plurality of shorter length cylinders connected in series. 
     The fabric sleeve  22  can be manufactured from any material that will satisfactorily interact with the expected wellbore fluids. The thickness, density, and permeability of the material can be selected based on the expected wellbore conditions and the configuration of the coring apparatus. For example, a fabric sleeve  22  can be manufactured from a fabric between 0.0625 and 0.75 inches thick, having a density of between 1 lbs./cu.ft. and 10 lbs./cu.ft., and having a permeability of between 0.1 and 10 millidarcys. The fabric used can be an oil-wetting material, a water-wetting material, a non-absorbing material, or a combination thereof, including, but not limited to polypropylene, polyester, polyaramid, homopolymer acrylic, and polyphenylsulphide. Other properties of the fabric material, such as color, can be selected based on the formation fluids expected and the intended analysis. For example, a low ultraviolet reflective fabric can be used in applications where oil fluorescence will be measured using ultraviolet light. 
     The composition of the fabric sleeve  22  can provide resistance to tearing, shearing, and other damage often seen in conventional sponge coring applications. For example, a fabric sleeve  22  manufactured from high-tenacity, long staple fibers assembled into a non-woven felt can provide increased resistance to tearing compared to a polyurethane foam sponge. Damage that may occur in the fabric sleeve  22  will likely be localized, therefore reducing the likelihood for damage to the fabric sleeve  22  to impact acquisition of the core  26 . 
     Further, the fabric sleeve  22  can be manufactured with a closely controlled inner diameter and thickness that can eliminate the need for any finish machining of the barrel liner assembly  24 . The fabric sleeve  22  can be manufactured so as to have substantially consistent properties across its thickness. As previously discussed, polyurethane foam used in conventional sponge coring has a variable permeability and density across its thickness that may interfere with the absorption of formation fluids. Due to its substantially homogenous nature, a fabric sleeve  22  can have consistent properties across its thickness, which can enable reliable absorption of formation fluids and an increased resistance to tearing or other damage. 
     Referring now to  FIG. 2 , a cross-sectional view of an exemplary barrel liner assembly  29  is shown including a liner body  30 , retention members  32 , a molded layer  34 , and a fabric sleeve  36 . Retention members  32  protrude inward from the wall of liner body  30  and can be integrally formed as part of the liner body or attached to the liner body through other means. Retention members  32  can be longitudinal, spiral, helical, or in any desired configuration. The liner body  30  can also include a plurality of orifices  38  that extend through the liner body  30  and are operable to relieve pressure and vent gas from the interior of the liner body  30 . 
     Molded layer  34  can be coupled to the interior walls of liner body  30  and to retention members  32 . The molded layer  34  can be a layer of material that is molded onto liner body  30 . The molded layer  34  can be a formed from a polymer, such as foamed or solid polyurethane, or other moldable material. The fabric sleeve  36  is coupled to the molded layer  34  and has an inner diameter sized to be in close contact with a core that is received by the barrel liner assembly  29 . The fabric sleeve  36  may be affixed to molded layer  34  by an adhesive or may be partially molded into the molded layer. 
     The molded layer  34  can be formed by directly molding the layer in place between the liner body  30  and the absorbent fabric sleeve  36 . As previously described, the absorbent fabric sleeve  36  can be provided as a cylinder of material having a selected thickness and inner diameter. The fabric sleeve  36  can be centrally disposed in the liner body  30  and offset from the inner diameter of the liner body  30  to form an annular mold into which the molded layer  34  can be formed. 
     As the liquid material is poured into the mold, it engages the outer edge of the fabric sleeve  36  and permeates a short distance into the fabric sleeve  36 . As the material sets to form the molded layer  34 , the engagement with the fabric sleeve  36  affixes the molded layer  34  to the fabric sleeve. Manufacturing the barrel liner assembly  29  in this method eliminates the need for machining molded layer  34  after it is formed. Further, because absorbent fabric sleeve  36  can be manufactured to the desired finished diameter, once the molding process is complete, the barrel liner assembly  29  can be ready for use without any further processing. 
     Referring now to  FIG. 3 , an exemplary barrel liner assembly  40  includes a liner body  42 , a molded layer  44 , and a fabric sleeve  46 . The liner body  42  can include a plurality of orifices  48 , and a plurality of retention channels  50 . Orifices  48  are operable to relieve pressure from the interior of the liner body  42 . 
     Integral channels  50  are shown as T-shaped slots but can have any desirable shape, including, but not limited to, T-shaped, L-shaped, and diagonal slots. During the molding process, the liquid sponge material enters the channels  50 . As the liquid material hardens to form the molded layer  44 , the material fills the channels  50 . Once molded layer  44  is formed, the retention channels  50  provide additional contact area between the liner body  42  and the molded layer  44 . This additional contact area can help to support the molded layer  44  and aid in preventing the molded layer  44  from tearing away from the liner body  42 . 
     The molded layer  44  can be formed by directly molding the molded layer  44  in place between the liner body  42  and the absorbent fabric sleeve  46 . The fabric sleeve  46  can be centrally disposed in the liner body  42  and offset from the inner diameter of the liner body  42  to form an annular mold into which the molded layer  44  can be formed. As liquid material is poured into the mold, it can permeate a short distance into the fabric sleeve  46 . As the material sets to form the molded layer  44 , the fabric sleeve  46  is affixed to the molded layer  44 . In other embodiments, the fabric sleeve  46  can be affixed to the molded layer  44  by an adhesive. 
     Referring now to  FIG. 4 , an exemplary barrel liner assembly  52  includes liner body  54  and fabric sleeve  56 . Fabric sleeve  56  can be affixed directly to liner body  54  through the use of an adhesive, mechanical means, or a combination thereof. The liner body  54  can include retention members  58  that act to engage fabric sleeve  56  and retain the layer in the liner body. The retention members  58  can be integrally formed as part of the liner body  54 , may be coupled onto the liner body  54 , or can be inserted through the wall of the liner body  54 . 
     The retention members  58  may be shaped to allow the fabric sleeve  56  to move longitudinally relative to the liner body  54  in a first direction but prevent the fabric sleeve from moving longitudinally in the opposite direction. In this manner, the retention members  58  allow the fabric sleeve  56  to be inserted longitudinally into the liner body  54  but retain the fabric sleeve  56  in position during coring operations. Liner body  54  can also include orifices  60  that relieve pressure and vent gas from inside the liner body  54 . 
     Referring now to  FIG. 5 , an exemplary barrel liner assembly  62  includes a liner body  64  and a fabric sleeve  66 . Liner body  64  can be constructed from a moldable material, such as polyurethane, that can be formed onto the fabric sleeve  66 . The fabric sleeve  66  can be disposed within a cylindrical mold into which a liquid material is poured. As the material sets to form the liner body  64 , it can permeate a short distance into the fabric sleeve  66 , thus affixing the fabric sleeve  66  to the liner body  64 . Liner body  64  can also include orifices  60  that relieve pressure and vent gas from inside the liner body  64 . 
     Referring back to  FIG. 1 , to acquire a core for analysis, the coring apparatus  10  is run into a wellbore disposed in formation  28 . As it is run into the formation  28 , the coring apparatus  10  can be subjected to increasing hydrostatic pressure. If the fabric sleeve  22  contains interstitial volumes that are filled with air, or any other compressible fluid, the increasing hydrostatic pressure can compress and potentially damage the fabric sleeve  22 . In order to counteract the compressive forces created by the increasing pressure, the barrel liner assembly  24  and fabric sleeve  22  can be filled with a pressurized fluid, or “pre-load fluid,” before being run into the formation  28 . 
     The pre-load fluid is selected so that the fluid is not absorbed by the fabric sleeve  22 . For example, if the fabric sleeve  22  is made from an oil-absorbing material, water could be used as a pre-load fluid. The selected pre-load fluid is not absorbed by the fabric sleeve  22  but can fill any interstitial areas within the fabric sleeve  22 , preventing damage to the fabric sleeve  22  as it is subjected to increasing hydrostatic pressure from being run into the formation  28 . 
     Once the coring apparatus  10  reaches the bottom of the wellbore in the formation  28 , the outer barrel  12  and coring bit  14  are rotated. Rotation of the coring bit  14  deepens the wellbore in formation  28  and creates core  26 , which increases in length as the coring bit  14  is moved through the formation  28 . As the core  26  moves through the center opening of the coring bit  14 , it is guided by core catcher  18  into barrel liner assembly  24 . 
     As the core  26  moves into the barrel liner assembly  24 , the fabric sleeve  22  closely engages the outer surface of the core  26 . As coring bit  14  continues drilling, the core  26  moves further into engagement with the fabric sleeve  22 . As the core  26  moves relative to the fabric sleeve  22 , it slides along the surface of the fabric sleeve  22 . As previously discussed, the fabric sleeve  22  resists tearing and damage caused by the dynamic interface with the core  26  and can reduce the impact of any damage by maintaining the damage in a localized area. Once drilling is complete, the core  26  can be disconnected from the formation  28 . The core  26  is retained within fabric sleeve  22  and barrel liner assembly  24  and the coring apparatus  10  can be withdrawn from the formation  28 . 
     As the core  26  is withdrawn from the formation, the hydrostatic pressure acting on the core  26  decreases. This decreasing pressure allows gas entrained within core  26  to expand in volume. As the gas expands, gas and other formation fluids contained within the core  26  can migrate out of the core  26 . Any fluids that migrate out of the core  26  will flow into fabric sleeve  22 . The close contact between the core  26  and the fabric sleeve  22  prevents gravity separation of fluids that migrate out of the core and maintains the formation fluids in close proximity to the portion of the core  26  from which they originated. 
     As migrating gases and formation fluids flow into the fabric sleeve  22 , pre-load fluid entrained in the fabric sleeve  22  will be displaced. The displaced pre-load fluid can pass laterally outward through orifices  38 . Fabric sleeve  22  is operable to absorb one or more of the formation fluids that can migrate out of the core  26 . For example, if the fabric sleeve  22  is oil-wetting, it can absorb hydrocarbons that migrate out of the core  26  while allowing water that migrates out of the core  26  to pass through without being absorbed. Because absorbent fabric sleeve  22  has a high permeability that is relatively constant across its thickness, non-absorbed fluids and gases can easily pass laterally through the fabric sleeve  22  and the orifices  38 . 
     This lateral movement of the fluids and gases through the fabric sleeve  22  and the orifices  38  can prevent a backpressure from forming therein that can impede free transfer of formation fluids present in the core  26  into the sleeve  22 . In addition, gases migrating out from the formation  28  can expand in volume so the orifices  38  provide an important pressure relief function. 
     After the core  26  and fabric sleeve  22  are withdrawn from the well, they can be shipped to a laboratory for analysis. As will be discussed in detail to follow, fluids retained by the fabric sleeve  22  can be analyzed along with the core  26  to provide useful information about the formation  28  and any fluids entrained in the formation. 
     In one example, the core  26  can be analyzed to establish the presence of hydrocarbon liquids, determine the amount of hydrocarbon liquids that can be held by the formation, and provide a qualitative assessment of any hydrocarbon liquids found. To facilitate this analysis, fabric sleeve  22  can be manufactured from an oil-wetting material that will preferentially absorb hydrocarbon liquids but will not absorb water. Once the core  26  is recovered, the core and the barrel liner assembly  24  can be sectioned along a longitudinal plane. The core  26  and fabric sleeve  22  can be analyzed to determine which portions of the core  26  produced hydrocarbon fluids during coring and which portions still contain entrained hydrocarbon fluids. 
     The hydrocarbon liquids found in the core  26  and/or in the fabric sleeve  22  can also be analyzed to determine what type and quality of hydrocarbons are found in the formation. One method for qualitatively assessing the liquid hydrocarbons is determining the fluorescence of the liquids using ultraviolet light. In this analysis, the fabric sleeve  22  can be examined with an ultraviolet light in order to determine the fluorescence of any oil contained within the sleeve  22 . Certain reflective materials may interfere with this analysis so the fabric sleeve  22  can be manufactured from a material that minimizes reflection of ultraviolet light so as to reduce interference with the determination of fluorescence of the liquid. 
     The hydrocarbon liquids that are collected by the fabric sleeve  22  and the hydrocarbon liquids that remain in the formation can be analyzed to determine the oil saturation of the formation, which can be used to determine the amount of oil that may be in place in the formation. In order to facilitate analysis, formation fluids can be recovered from fabric sleeve  22  by one or more processes including, but not limited to, mechanical separation, chemical treatments, thermal processing, or any combination thereof. 
     The analysis of the core and fabric sleeve  22  can include a solvent extraction method to remove all the hydrocarbons from the fabric sleeve  22 . Conventional solvents, such as toluene, used to extract hydrocarbons from foam, which often caused a reaction with the foam itself, will not typically react with the fabric sleeve  22 . After the hydrocarbons have been extracted from the fabric sleeve  22  and are in solution with the solvent, usual means of measuring the oil content in the solution can be used, e.g. florescence intensity, or gas chromatography. The oil saturation measured in the fabric sleeve can then be added to the oil saturation measured in the core, to provide a more accurate determination of the volume of oil in the core, and by application the amount of oil in the reservoir. 
     In another example, a core  26  is recovered from a formation that contains hydrocarbon gases and water, but does not contain significant amounts of hydrocarbon liquids. An indication as to the amount of gas entrained in the formation can be determined if the amount of water in the formation, or water saturation, can be determined. In order to facilitate this analysis, fabric sleeve  22  can be manufactured from a water-wetting material that will preferentially absorb water but will not absorb hydrocarbon liquids. 
     As the core  26  is recovered from the formation, gases entrained in the formation will expand and migrate out of the core. As the gases migrate, they can cause water and other formation fluids to also migrate out of the core. As these fluids migrate, fabric sleeve  22  will absorb water while allowing any hydrocarbon fluids to pass through the sleeve. The water absorbed by the fabric sleeve  22  can be recovered and, along with water retained in the core  26 , analyzed to determine the water saturation of the formation. 
     The fabric sleeve  22  may also act as a jam prevention tool. A core jam normally occurs when a core that enters a conventional coring assembly fractures and the broken core wedges across the confining inner diameter of an inner barrel. When a core jam occurs, the core can no longer enter the core barrel and, once the problem is detected, the core run is ended. The coring assembly is pulled from the well and additional core runs may be needed to recover the total zone of interest. A core jam can also subject the core below the point of jam to high compressive forces as drill string weight is transferred to the core column. This compressive force can eventually exceed the strength of the core column and result in a broken and damaged core, which significantly reduces its value in core analysis. If the formation is soft and friable, the jam may not be identified by surface operating parameters and the jammed barrel may mill up, or drill additional hole without core entry, thus losing valuable data. 
     The fabric sleeve  22  can act to guide to allow the core to continue moving into the core barrel even though the core may have fractures that would normally try to wedge against the inner diameter of a conventional inner tube and jam. Conventional sponge liners often tear or delaminate when interacting with a fractured core. The high tenacity, shear strength, and flexibility of a fabric sleeve could contain or channel the core as it passes into the inner barrel. The fabric sleeve  22  can allow some diametrical expansion of the core column and act as a guide by not allowing it to get a firm purchase on the surface of the fabric. 
     To further enhance resistance to a core jam, a fabric sleeve  22  could be saturated with a lubricant, such as mineral oil, to provide lubricity in addition to the guiding of the core. Once the fabric sleeve  22  is saturated with a lubricant, the excess lubricant can be drained from the liner assembly, but the lubricant saturated in the fabric sleeve  22  will be retained. 
     Conventional systems used to mitigate core jams often have relatively short lengths over which the system can be effective. Because the fabric sleeve  22  covers the inner surface of the liner assembly, running multiple lengths of liner together can allow jam protection over a much longer length, perhaps 300 ft, or more. 
     While the disclosure is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and description. It should be understood, however, that the drawings and detailed description thereto are not intended to limit the disclosure to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the present disclosure.