An improved blast liner assembly for use in gravel packing or fracturing operations wherein solid materials, in slurry form, are flowed out of the flowbore of a working tool and into the annulus of a wellbore. The blast liner is a cylindrical member that provides a protective shield to the interior retaining section. An angular flow diverter is provided within the blast liner and has a plurality of angled flow diversion channels formed into the inner surface of the blast liner body. Flow of slurry through the blast liner will cause the blast liner to rotate within the retaining section due to the reaction forces imparted to the blast liner from diverting the slurry flow. In this manner, the impingement area presented by the blast liner is increased, and the life of the blast liner extended. The blast liner may also be caused to move axially within the retaining section to further increase the impingement area.

BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The invention relates generally to devices and methods for improved fracturing and/or gravel packing operations within a wellbore. In more particular aspects, the invention relates to the protection of devices that are used to place gravel or proppants in such operations.  
         [0003]     2. Description of the Related Art  
         [0004]     There are times during the life of a well that it is necessary to flow granular or pelletized solid materials, in a slurry, into a wellbore in order to improve wellbore operation or to extend the life of the well. Two of the more common techniques are gravel packing and fracturing of a formation using a fracturing fluid having proppant therein. During gravel packing, gravel is pumped down a tubing string into a wellbore and placed, where desired, using a cross-over tool with suitable exit ports for placement of the gravel in desired locations within the wellbore. In fracturing operations, a fracturing agent is flowed into the wellbore under very high pressure to fracture the formation that immediately surrounds the borehole, thereby creating improved flowpaths for hydrocarbons to enter the wellbore from the surrounding formation. The fracturing agent, a fluid, often contains a proppant, which is in granular or pelletized form. Typical proppants includes peanut shells, sand, ceramics, and other materials known in the art. Proppants are flowed into the fractures created by the fracturing agent and remain there after the fracturing agent has been removed from the wellbore in order to help prop the fractures open and allow the improved flow to continue.  
         [0005]     While gravel packing and fracturing operations are often necessary, they do create significant erosion wear upon the components of the production assembly as the gravel or proppant is flowed into the wellbore. Erosion damage to the production assembly, if significant, can result in a loss of production containment in the wellbore. One area that tends to receive the most severe damage is around the exit port where the solid material exits the crossover tool and enters the inside of the production assembly. In order to counter this significant wear damage, devices have been developed that are better able to withstand the wear associated with these operations. Typically, a wear sleeve or blast liner will be placed proximate the exit port, or the exit port will actually be disposed through this wear sleeve or blast liner. There is, however, some disagreement over the preferred composition of a wear sleeve or blast liner that should be used. Materials that are harder, and less subject to deformation, also tend to be more brittle. Additionally, regardless of the material that is used to form the sleeve or liner, the concentration of erosive forces upon the liner/sleeve will always tend to shorten the life of the placement components.  
         [0006]     The present invention addresses the problems of the prior art.  
       SUMMARY OF THE INVENTION  
       [0007]     The invention provides an improved blast liner assembly for use in gravel packing or fracturing operations wherein solid materials, in slurry form, are flowed out of the flowbore of a working tool, into the production assembly, then into the annulus of a wellbore. In preferred embodiments, a gravel packing placement system includes an extension sleeve that is landed in a wellbore and a service tool that is run inside the extension sleeve. The service tool defines an axial flowbore and a lateral gravel exit port. The extension sleeve has an interior retaining section that contains a rotatable blast liner.  
         [0008]     The blast liner is a cylindrical member that provides a protective shield to the interior retaining section. It is typically fashioned from a hardened, resilient material, such as 4140 steel. The blast liner includes an impingement area that may be coated with a protective coating, such as a ceramic or tungsten coating. Additionally, an angular flow diverter is provided within the blast liner, preferably proximate the lower end. In preferred embodiments, the flow diverter is a plurality of angled flow diversion channels formed into the inner surface of the lower end of the blast liner body. The flow diversion channels may be provided by several radially inwardly-projecting vanes or, in the alternative, grooves that are milled into the interior surface of the lower end. Flow of slurry through the blast liner will cause the blast liner to rotate within the retaining section due to the reaction forces imparted to the blast liner from diverting the slurry flow. In this manner, the impingement area presented by the blast liner is increased, and the life of the blast liner extended.  
         [0009]     Several exemplary constructions for a rotatable blast liner assembly are described herein. In one embodiment, the liner is rotatable within a fixed axial space in the retaining section. Bearing members are disposed between the blast liner and the retaining section to assist rotation. In a second described embodiment, the blast liner assembly includes a wearable, or erodable, bushing that is disposed below the blast liner in the liner retaining section. As the liner rotates within the liner retaining section, the bushing wears away, resulting in axial movement of the blast liner within the liner retaining section. This axial movement further increases the impingement or wear area provided by the blast liner. In a further described embodiment, the liner retaining section is provided with a circuitous lug track and the blast liner is provided with an outwardly projecting lug that resides within the lug track. Rotation of the blast liner within the liner retaining section thereby results in controlled axial movement of the blast liner within the liner retaining section. Again, the axial movement of the blast liner acts to increase the impingement or wear area provided by the blast liner. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     For a thorough understanding of the present invention, reference is made to the following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings, wherein like reference numerals designate like or similar elements throughout the several figures of the drawings and wherein:  
         [0011]      FIGS. 1   a  and  1   b  are side, cross-sectional views of a wellbore having an exemplary solids placement tool suspended therein.  
         [0012]      FIG. 2  is an isometric view of an exemplary blast liner constructed in accordance with the present invention.  
         [0013]      FIG. 3  is a side, cross-sectional view of the exemplary blast liner shown in  FIG. 2 .  
         [0014]      FIG. 4  is an axial cross-section of an alternative blast liner wherein the flow channels are formed by milling into the interior surface of the liner body.  
         [0015]      FIGS. 5   a  and  5   b  depict an alternative embodiment for an exemplary blast liner assembly constructed in accordance with the present invention, which incorporates a progressive wear member to permit axial travel of the blast liner.  
         [0016]      FIG. 6  is a side, cross-sectional view of an alternative embodiment for an exemplary blast liner assembly which incorporates a lug and track mechanism to permit liner movement of the blast liner during operation.  
         [0017]      FIG. 7  is a side, cross-sectional view of the track mechanism for the assembly shown in  FIG. 6 .  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0018]      FIGS. 1   a  and  1   b  depict an exemplary solids placement system  10 , which includes an extension sleeve assembly  12  that is secured to the lower end of a packer assembly  14 . The exemplary solids placement system  10  is a system for the placement of gravel within a wellbore  16  during gravel packing. However, those of skill in the art will appreciate that a similar arrangement may be used for disposal of proppants and other solids within a wellbore. It is noted that the details of gravel packing and proppant placement operations generally are well known to those of skill in the art and, therefore, will not be described in detail herein. However, the general outline of an exemplary gravel packing tool and system  10  is described in order to illustrate one use of the blast liner assembly of the present invention.  
         [0019]     The packer assembly  14  is a through-tubing packer assembly in that, once set, it can permit a service tool to be passed through its axial center. At the beginning of a gravel packing operation, the packer assembly  14  and extension sleeve assembly  12  are run into the wellbore  16 . The packer assembly  14  is set against the cased side of the wellbore  16 , and an annulus  18  is thereby defined between the extension sleeve assembly  12  and the side of the wellbore  16 . In this situation, it is desired to place gravel  20  within the annulus  18  below the packer  14 .  
         [0020]     The extension sleeve assembly  12  has a generally cylindrical body  22  and defines an interior bore  24  with a pair of gravel flow ports  26  disposed therethrough. The extension sleeve assembly  12  also includes a blast liner retainer section, generally shown at  28 . A rotatable blast liner  30 , the structure and operation of which will be described shortly, is retained within the blast liner retainer section  28 .  
         [0021]     The solids placement system  10  also includes a service tool, generally shown at  32 , which is disposed through the packer assembly  14  and into the bore  24  of the extension sleeve assembly  12 . The service tool  32  is suspended upon a tubing string  34  that extends to the surface of the wellbore  16 . The tubing string  34  defines an axial flowbore  36  along its length. The other portion of the service tool  32  is a gravel placement tool  38 , which is secured to the lower end of the tubing string  34  and defines an axial, interior flowbore  40  along its length as well. Reverse recirculation ports  42  are disposed through a lower portion of the gravel placement tool  38 . The use of such recirculation ports in gravel packng tools is well understood by those of skill in the art and, therefore, will not be described in any detail herein. Annular elastomeric seals  44  surround the gravel placement tool  38  at intervals along its length and serve to provide fluid sealing. The flowbore  40  of the gravel placement tool  38  contains a ball seat  46 . Located just above the ball seat  46  is a lateral gravel flow port  48 .  
         [0022]     Turning now to  FIGS. 2, 3 , and  4 , the structure and operation of an exemplary rotatable blast liner  30  is now further described.  FIGS. 2, 3 , and  4  depict a blast liner  30  having a generally tubular liner body  50  with a pair of annular recessed portions  52 ,  54  upon the outer surface  56  of the blast liner  30 . The radially inner surface  58  of the blast liner  30  includes a lower diversion portion  60  proximate the lower axial end  62  of the liner body  50 . The diversion portion  60  features a plurality of angled flow channels  64 . The flow channels  64  are formed between inwardly projecting vanes  66 , as shown in  FIGS. 2 and 3 . Alternatively, flow channels may be formed by milling angled grooves  64 ′ into the radially inner surface  58  of the blast liner body  50 , as in alternative blast liner  30 ′ illustrated in  FIG. 4 .  
         [0023]     Referring again to  FIGS. 1   a  and  1   b , when the service tool  32  is disposed into the extension sleeve assembly  12 , it is landed by the interengagement of landing shoulders (not shown), in a manner known in the art. When landed, the lateral gravel flow port  48  of the service tool  32  is located adjacent an upper portion of the rotatable blast liner  30 . An annular space  70  is defined between the blast liner  30  and the outer radial surface  72  of the gravel placement tool  38 . In order to begin placing gravel, a ball plug  74  is dropped into the flowbore  36  of the tubing string  34  and lands upon the ball seat  46 . Once the ball plug  74  is seated, any fluids or slurries that are pumped down the flowbore  36  from the surface will be forced to exit the flowbore  36  through the gravel flow port  48 .  
         [0024]     In operation, flow of gravel slurry out of the gravel flow port  48  and through the annular space  70  to the gravel flow ports  26  will induce rotation of the blast liner  30  within the liner retaining section  28  in the direction opposite that in which the flow is being diverted by the diverter section  60  of the blast liner  30  due to the principal of equal and opposite reaction of forces. Arrow  76  in  FIG. 3  illustrates the direction of the rotation of the blast liner  30 , while arrows  78  in  FIG. 3  illustrate the direction of diversion of slurry by the diversion portion  60 . Rotation of the blast liner  30  within the liner retaining section  60  will prevent a single small area of the blast liner  30  from being exposed to the blast of slurry exiting the gravel flow port  48 . Wear and abrasion damage will be spread substantially evenly about the circumference of the inner surface  58  of the blast liner  30  as the liner  30  is rotated, rather than the erosion wear being concentrated upon one angular area of the liner  30 . As a result of the rotation of the liner  30 , the life of the blast liner  30 , and the solids placement system  10 , overall, is extended as compared to a stationary sleeve, which would develop a hole at the point of impact.  FIGS. 1   a  and  2  illustrate an exemplary annular primary wear, or impingement, area  80  having upper boundary  82  and lower boundary  84  upon the inner radial surface  58  of the blast liner  30 . The primary wear area  80  is the portion of the inner radial surface  58  of the blast liner  30  that lies proximate the gravel flow port  48  and receives the primary erosion wear from gravel exiting the port  48 . It is noted that annular bearings  86 ,  88 , visible in  FIG. 3  reside within the recessed portions  52 ,  54 , respectively, to provide for standoff of the blast liner  30  from the liner retaining section  28  of the extension sleeve assembly  12  and helps ensure ease of rotation of the blast liner  30  within the liner retaining section  28 .  
         [0025]      FIGS. 5   a  and  5   b  depict portions of an alternative embodiment for a blast liner assembly, generally indicated at  90 , that is constructed in accordance with the present invention. The blast liner assembly  90  is used within the solids placement system  10  described earlier. In this embodiment, the blast liner  30 ,  30 ′ is caused to move axially as well as rotationally within the liner retaining section  28  during use, thereby further increasing the area of the sleeve that is exposed to wear and abrasion damage. Because the damage is spread upon a larger area, there is less severe damage to any point area upon the sleeve.  
         [0026]     The blast liner assembly  90  includes the blast liner  30  radially surrounding the gravel placement tool  38  and the liner retaining section  28  within the body  22  of the extension sleeve assembly  12 . It is noted that, although a blast liner  30  is depicted in  FIGS. 5   a  and  5   b , a blast liner having milled grooves to form the flow channels, such as exemplary blast liner  30 ′ might be used as well in the blast liner assembly  90 . Additionally, the blast liner assembly  90  includes an erodable or wearable bushing  92  that is retained within the liner retaining section  28  below the blast liner  30 . The wearable bushing  92  is formed of a readily erodable material, such as fiberglass, ceramic, or plastic. As the blast liner  30  (or  30 ′) rotates within the liner retaining section  28 , as described above, during flow of gravel slurry, the frictional engagement of the lower end of the blast liner  30  (or  30 ′) with the bushing  92  will cause the bushing  92  to gradually wear away.  FIG. 5   a  depicts the blast liner assembly  90  at the onset of flowing of gravel slurry, while  FIG. 5   b  depicts the assembly after slurry has been flowed for a period of time. As can be seen by a comparison of  FIGS. 5   a  and  5   b , the bushing  92  has become much shorter axially due to the frictional wear upon it provided by the blast liner  30 / 30 ′. As a result, the blast liner  30 / 30 ′ moves progressively downwardly within the liner retaining section  28 . As the liner  30  or  30 ′ moves downwardly within the liner retaining section  28 , the annular impingement area  80  is expanded axially as the upper boundary  82  of the impingement area progressively moves upwardly upon the inner surface  58  of the liner body  50 .  
         [0027]     Referring now to  FIGS. 6 and 7 , a further embodiment is depicted for a blast liner assembly  100  constructed in accordance with the present invention. The blast liner assembly  100  includes a blast liner  30 ″ that is retained within the liner retaining section  28 ′ of the extension sleeve assembly  12 . The liner retaining section  28 ′ is inscribed with a lug track  102 , which is continuous. Details of the lug track  102  are better understood with reference to  FIG. 7 , which depicts the liner retaining section  28 ″ in cross-section apart from other components. The lug track  102  of the liner retaining section  28 ″ is essentially a double-helix that includes a first helical path  104  which, in the manner of a spring, is made up of individual spiral winds  106  that are sequentially disposed along the length of the retaining section  28 ″. The winds  106  are formed in a first spiral direction. For example, as illustrated in  FIG. 7 , the path  104  and winds  106  proceed downwardly along the length of the retaining section  28 ″ when traversed in a clockwise direction. The lug track  102  also includes a second helical path  108  that is inscribed within the retaining section  28 ″. The second helical path  108  includes multiple individual spiral winds  110 , which are oriented in a second spiral direction from the first winds  106 . As depicted in  FIG. 7 , the second helical path  108  and winds  110  proceed axially upwardly along the length of the retaining section  28 ″ when traversed in a clockwise direction. Both axial ends of the spiral paths  106 ,  110  are joined to one another at a joining point  112 . Only one joining point  112  is depicted in  FIG. 7 . However, it will be understood that the opposite end of each spiral path  106  and  110  will be joined at a similar joining point at their opposite ends. As a result of the joining points  112 , a continuous double-helical path is provided for the lug track  102 .  FIG. 6  illustrates that a lug  114  projects outwardly from the outer surface of the blast liner  30 ″ and resides within the lug track  102 . When the blast liner  30 ″ is then rotated within the liner retaining section  28 ′ by flow of slurry, as described previously, the lug  114  will be moved along the lug track  102  imparting axial movement to the blast liner  30 ″. This axial movement of the liner  30 ″ will cause the impingement area  80  to become axially larger. Approximate upper and lower boundaries  82 ,  84  of the annular impingement area  80  are illustrated in  FIG. 6 .  
         [0028]     Those of skill in the art will recognize that the above-described devices and methods, although described in relation to a gravel packing arrangement, are also readily applicable to other solids placement arrangements, such as fracturing tools that place solid proppants within a wellbore. Those of skill in the art will also recognize that numerous modifications and changes may be made to the exemplary designs and embodiments described herein and that the invention is limited only by the claims that follow and any equivalents thereof.