Abstract:
A device for improving down hole operations includes a tube that delivers high pressure jets of fluid against the interior surface of a well casing and optionally into perforations of the well casing. The tube also includes a helical array of brushes that scrape and scratch accumulated residue from the interior surface of a well casing and optionally into perforations of the well casing. A method for improving down hole operations includes moving the device into a bend or turn in an existing well casing string and retracting a nozzle or brush to facilitate passage of the device past the bend or turn.

Description:
[0001]    This application claims the benefit of U.S. Provisional Application No. 61/044,675, filed Apr. 14, 2008, and U.S. Provisional Application No. 61/044,667, filed Apr. 14, 2008, which are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates generally to devices, systems and methods relating to improved down hole operations and, more particularly, to devices, systems and methods for enhance the recovery of hydrocarbon liquids and gases from down hole environments. 
       BACKGROUND OF THE INVENTION 
       [0003]    The amount of oil and/or gas that a well produces often reduces significantly over time. The reduction is often caused by clogged or obstructed perforations in the well casing at the production area and the accumulation of wax, scale, or other residue on the inside of the casing of the well. Prior art methods for removing such debris and clearing the well casing perforations often require multiple tools, are inefficient and time consuming. Prior art methods and devices also may tend to alter ground formation permeability and may not allow for immediate bore cleanup without damage to the ground formation. Accordingly, there is a need for a method, system and device that provides for an efficient, cost-effective means to improve down hole operations. 
       SUMMARY OF THE INVENTION 
       [0004]    Certain embodiments of the present invention generally relate to devices, systems and methods relating to improved down hole operations. Embodiments of the present invention may be used to enhance the recovery of hydrocarbon liquids and gases from down hole environments. Embodiments may comprise an assembly attachable to a work string, with the assembly further comprising a plurality of directed fluid jets, brushes and or scrapers. Embodiments may comprise methods of using the assembly to enhance down hole operations or production. 
         [0005]    In aspects of the present invention, a device for improving pumping operations through a casing or lining comprises a hollow tube including a tube wall having an outer circumferential surface and an inner circumferential surface, the inner circumferential surface defining a fluid passageway. The device further includes brushes on the outer circumferential surface, and outlet holes formed through the tube wall. 
         [0006]    In aspects of the present invention, a system for improving pumping operations through a well casing or lining comprises a hollow scratcher tube including a tube wall having an outer circumferential surface and an inner circumferential surface, the inner circumferential surface defining a fluid passageway having a fluid inlet at one end of the scratcher tube. The system further comprises a plurality of bristles on the outer circumferential surface, a plurality fluid outlets formed through the tube wall, and a filter coupled to the fluid inlet. 
         [0007]    In aspects of the present invention, a method for improving down hole operations includes inserting a scratcher tube into a curved casing string, the hollow scratcher including a tube wall having an outer circumferential surface carrying a plurality of brushes and a plurality of nozzles. The method further includes retracting at least one of the plurality of brushes or at least one of the plurality of nozzles to facilitate passage of the scratcher tube past a curved segment of the casing string. 
         [0008]    The features and advantages of the invention will be more readily understood from the following detailed description which should be read in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is side elevation view of an assembly for improving down hole operations, showing a main body having a plurality of nozzle assemblies and brush assemblies. 
           [0010]      FIG. 2A  is a cross sectional view of a nozzle assembly. 
           [0011]      FIG. 2B  is a side elevation view of the nozzle assembly of  FIG. 2A . 
           [0012]      FIG. 3  is a cross sectional view of a portion the main body of  FIG. 1 , showing staggered insets  60  for receiving the nozzle assembly of  FIGS. 2A and 2B . 
           [0013]      FIG. 4  is a side view of an assembly for improving down hole operations, showing a plurality of outlet holes and inset portions for securing nozzles and brushes. 
           [0014]      FIGS. 5A-5D  are cross sectional views of the assembly of  FIG. 4 , showing various angular positions of inset portions for securing brushes. 
           [0015]      FIG. 6  is a cross sectional detailed view of a portion of  FIG. 5A , showing an inset portion and a correspondingly shaped brush assembly adapted to be secured into the inset portion. 
           [0016]      FIG. 7  is a cross sectional view of a the assembly of  FIG. 4 , showing various angular positions of outlet holes for securing nozzles. 
           [0017]      FIG. 8  is a cross-sectional detailed view of a portion of  FIG. 7 . 
           [0018]      FIG. 9A-9D  are a top view, side view, bottom view, and cross-section view, respectively, of a nozzle. 
           [0019]      FIGS. 10A-10D  are cross-sectional views of piston-type assemblies adapted to allow radial movement of a brush assembly. 
           [0020]      FIGS. 11A-11D  are cross-sectional views of piston-type assemblies adapted to allow radial movement of a nozzle 
           [0021]      FIG. 12  is an side elevation view of a system for improving down hole operations, showing the system in a disassembled state. 
           [0022]      FIG. 13  is a side elevation view of the system of  FIG. 12 , showing the system in a partially assembled state with a scratcher tube removed from the rest of the system. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0023]    Some embodiments of the present invention may comprise an assembly having a generally tubular shape and having a diameter appropriately sized to be inserted into the casing or well lining of a well, including in some instances an oil or gas production well. In some embodiments of the present invention the assembly may further comprise pressure jets, nozzles, and or orifices, brushes, and or scrapers. The assembly may comprise attachment configurations on an upper and lower portion of the assembly. The attachment configurations may facilitate attachment of the upper end of the assembly to a work string, sucker or other assembly. The attachment configurations may also facilitate attachment of the lower end of the assembly to other devices such as scrapers, filters, baskets or other devices. 
         [0024]    In some embodiments the present invention is used to improve the flow of fluids, such as petrochemicals, or gases, through perforations or holes in the casing of an oil or gas well. In some embodiments of the present invention the flow of fluids or gases through the formations adjacent the perforations or holes in the casing may also be improved. 
         [0025]    Over the course of production of fluids or gases from a well there may typically be a buildup of paraffin, wax, scale, or other residue on the inside of the casing of the well. In some instances the perforations or other slots or openings on the casing become clogged to some degree. Additionally spaces in the geological formations adjacent the casing may also become clogged to some degree. Each of these conditions may tend to inhibit the flow of desired gases or fluids from the geological formation through the slots or perforations and into the casing of the well where it can be extracted from the well. Aspects of the present invention are particularly useful in cleaning the inside environment of the casing, of opening the perforations or slots extending through the casing and further, in opening portions of the geological formations adjacent the casing to further facilitate the flow of gases or liquids. 
         [0026]      FIG. 1  shows an embodiment of the present invention. Shown is an assembly  10  having an upper threaded portion  12  and a lower threaded portion  14 . Further shown in the assembly of  FIG. 1  are three rings of nozzles (or high-pressure jets)  18  (shown at  18 A,  18 B and  18 C). Also shown in  FIG. 1  is a spiraling array of brush assemblies  20 . An individual brush assembly is shown at  22  having brush fibers  24 , fiber assembly holder  26 , and threaded portion  28 . 
         [0027]    The assembly  10  may comprise a pipe like main body  11  having an outer diameter and an inner diameter. 
         [0028]    Main body  11  may have an inset portion for receiving the fiber assembly holder  26  of the individual brush assembly  22 . Further the inset portion they also comprise a receiver for receiving the threaded portion  28  of the brush assembly  22 . In some embodiments, the fiber assembly holder  26  does not extend out past the general exterior wall of the main body  11 . Instead, the brush fibers  24  extend radially out past the general exterior wall of the main body in  11 . The inset portions for receiving the fiber assembly, in some embodiments, may be spiraled vertically about the main body  11  as shown in  FIG. 1 . Such an arrangement allows for the overlap of the individual brushes of the brush assemblies  22  with the brushes of adjacent assemblies. 
         [0029]    Main body  11  may also include inset portions for receiving individual nozzles or high-pressure jets indicated at  18  and further illustrated in  FIGS. 2 and 3 . In some embodiments the inset portions for the individual nozzles are distributed around the circumference of the main body  11  as shown at  18 . In some embodiments the distribution of the inset portions for the nozzles may be staggered vertically as shown in  FIG. 1  at  18 . This staggering of the inset portions provides several advantages. One advantage is that it allows the nozzles to be spaced circumferentially about the main body  11  with smaller angles separating a first nozzle from an adjacent nozzle while still providing high structural integrity and strength to the main body  11 . In addition, as shown at  FIG. 3 , the individual insets may be so closely spaced that, as shown in  FIG. 3 , when viewed in cross-section the insets may appear to overlap with each other. By staggering the insets, this small rotational angle between the direction of adjacent nozzles can be achieved without deleteriously diminishing the structural integrity of the main body  11 . 
         [0030]    In some embodiments the assembly  10  is connected by upper threaded portion  12  to a working string and lowered to the production zone of a well. The assembly  10  can be raised and lowered by the working string to effect a beneficial interaction between the inside of the casing of the well and the brush assemblies  20  of the assembly  10 . The brush assemblies can be configured in some embodiments to provide forceful brush contact simultaneously around the interior circumference of the casing as the assembly  10  is raised and lowered through the production zone of the casing. The brush assemblies  20 , then, “scrub” the interior portions of the casing in the production zone. Such scrubbing is useful in removing undesirable materials from the inside of the casing and the perforations or slots in the casing. 
         [0031]    In some embodiments, simultaneously with the raising and lowering of the assembly  10  through the production zone of the well, high-pressure fluids are pumped through the work string into the top portion of the assembly  10 . In some embodiments, the assembly  10  will have a cap or similar structure attached to the bottom threads  14  prohibiting the exit of high-pressure fluids through the bottom portion of the assembly  10 . The high-pressure fluid will then exit the individual nozzles  18  of the assembly producing a highly desirable scouring effect on the interior portions of the casing as well as in the perforations and slots of the casing. The high-pressure flows of the fluid can also extend into the geological formations adjacent the casing thus opening improved opportunities for the flow of gas or fluid through the geological formations. 
         [0032]    Because of the overlap of the brush assemblies  20  when the assembly  10  is raised and lowered through the casing, the entire periphery of the casing is scrubbed by the brushes. The assembly  10  can include a number of brushes including one to four (or more) sets the brushes covering 360° of the exterior of the assembly  10 . 
         [0033]    Shown in  FIG. 1  are three arrays of nozzles,  18 A,  18 B and  18 C. in some embodiments a greater or lesser number of arrays of nozzles can also be used. 
         [0034]      FIG. 2  shows two views of an exemplary nozzle assembly  40 .  FIG. 2B  shows a plain view of the nozzle assembly  40  having a hexagonal or orthogonal head portion  42  and a threaded portion  44 .  FIG. 2A  shows a cutaway view of the nozzle assembly  40  of  FIG. 2B . 
         [0035]    Shown in  FIG. 2A  is a fluid passageway comprising three sections: large diameter section  46 , step down section  50 , and small diameter section  48 . Also shown is an O-ring receiver portion  52 . The nozzle assembly  40  can be assembled into an appropriately sized inset in the main body  11 . The threaded portion  44  will mate with a threaded receiver in the main body  11 . The main body inset for the nozzle  40  can also comprise a receiver surface for receiving the O-ring (not shown) to be an attached in O-ring receiver portion  52 . The small diameter section  48  of the fluid passageway can be of varying lengths, including significantly shorter than the large diameter portion  46 . With this configuration the flow of high-pressure fluids through the nozzle assembly  40  is significantly facilitated, allowing a greater flow of fluid through the nozzle assembly  40  and reducing the energy loss of forcing the fluid through the fluid passageway of the nozzle assembly  40 . 
         [0036]    Shown that  FIG. 3  is a partial cross-sectional view of the main body  11  along the line  2 - 2  of  FIG. 1 . Shown in  FIG. 3  are three staggered insets  60  for receiving the nozzle assembly  40 . As can be seen in  FIG. 3 , the insets  60  may actually be positioned on radial angles sufficiently small that in the perspective of  FIG. 3  the insets  60  may be seen to overlap with each other. This facilitates a very close spacing of the angles of fluid jets from the nozzle assemblies  40  and increases the likelihood that high-pressure jet fluid flow will be directed at virtually every portion of the interior surface, perforation, slot or other opening of the casing. Further, the individual insets  60  can be “clocked” respectively between the arrays of nozzles such as is shown in  18 A,  18 B and  18 C. Thus the individual nozzles of  18 B can be clocked a few degrees from the positioning of the nozzles of  18 A and the nozzles of  18 C can be clocked a few degrees from the positioning of the nozzles of  18 B. In this fashion a very comprehensive coverage of the interior surfaces of the casing, perforations, slots or other openings can be achieved by the directed jets of fluids exiting the nozzles. 
         [0037]    During operation, in some embodiments, the main body  11  can be raised and lowered once or multiple times through the entire production zone of the well. In such fashion, the individual brushes and nozzles are effective through the entire production zone. 
         [0038]    In some embodiments a tubular type filter can be positioned at the top of the assembly  10  and inside the work string attached to the assembly  10 . The filter can provide many benefits including ensuring that only desired qualities of fluids (i.e. fluids without undesirable particles) are pumped into the assembly  10  and out the individual nozzles  40 . The tubular configuration of the filter can facilitate a modular array of filters that are connected end to end above the assembly  10 . In this fashion an overabundance of filter modules can be provided in conjunction with the assembly  10  before it is lowered into the well. The overabundance of filter capability can be useful to prevent a circumstance where a deficiency in filter surface area might exist while the tool  10  is down in the casing in cleaning operation. Should the filter have insufficient surface area to handle filtering needs for the entire duration of the cleaning operation, the filter may collapse because of the high pressures or otherwise become clogged thus reducing the efficacy of the cleaning operation. In some embodiments, the filter assemblies may comprise a 40 micron stainless steel strainer positioned at some distance, such as 30 feet, above the assembly  10  and a 30 micron stainless steel strainer located directly over the assembly  10 . 
         [0039]    In some embodiments, the inset portion for receiving the fiber assembly holder  26  of the individual brush assemblies  22  may be designed to snugly receive the fiber assembly holder  26 . By this fashion additional mechanical support and directive force is applied to the brush portions of the individual brushes. 
         [0040]    In some embodiments the assembly  10  can be configured and the system operated so as to provide up to 2000 or more pounds of fluid pressure per individual nozzle. 
         [0041]    Some embodiments of the present systems and devices can be applied to improve production from liner completed wells, inner liner completed wells, and solid string completed wells. 
         [0042]    In some embodiments a surface pump is used to displace fluids at high pressures through a working string to the assembly  10 . In some embodiments the assembly  10  may also comprise an upper collar that acts as a centralizer for the apparatus while in the casing. In some embodiments the assembly  10  may comprise a lower collar that acts as a centralizer for the apparatus while in the casing. In some embodiments the apparatus  10  may include both an upper and a lower collar. In some embodiments a scraper may be attached to the lower portion of the assembly  10 . The collars may also allow the washing fluid to be evenly displaced. 
         [0043]    In some embodiments the O-ring used in the nozzle assembly seating system may comprise Viton. In some embodiments the hexagonal or octagonal portion of the nozzle assembly  40  may facilitate set torque specifications for attaching the nozzle assemblies to the main body  11  and prohibiting undesirable loosening of the nozzles or over tightening of the nozzles. In some embodiments two or more circumferences of brush assemblies may be provided on the main body  11 . 
         [0044]    In some embodiments the fluid pumped through the assembly  12  may comprise an acidic solution. In some embodiments the fluid may comprise a washing fluid. In some embodiments the fluid may comprise water as found in the region of the well site. 
         [0045]    In some embodiments the individual nozzle assemblies  40  may extend radially outside the surface of the main body  11 . In some embodiments the individual nozzles assemblies  40  may extend just to the exterior surface of the main body  11 . In some embodiments the individual nozzle assemblies may not extend out to the exterior surface of the main body  11 . In some embodiments the nozzle assemblies  40  may be movably mounted on the main body  11 . In one embodiment, the nozzle assemblies are seeded into receivers in the main body. The nozzle assembly is connected to a piston type seat which is positioned in an inset in the main body. During operation when the assembly  10  is positioned in the production zone of the casing and the high-pressure fluid pumping is initiated, the pressure from the high-pressure fluid presses the piston assembly radially outward pressing the nozzles also radially outward and closer to the inside surface of the casing. In some embodiments the brush assemblies may also be movably positioned with piston type assemblies attached to the individual brushes. Again, when high-pressure fluid pumping is initiated the fluid pressure presses the piston assemblies and presses the brush assemblies radially outward and in enhanced contact with the inner surface of the casing. In some embodiments, the nozzle and or brush assembly configuration may include a spring which biases the positioning of the nozzle and or the individual brushes radially inward in the assembly  10  and until high-pressure fluid pumping is initiated. With the initiation of the high-pressure pumping, the bias of the spring is overcome by the pressure of the fluid on the piston and the nozzle and or brush is pressed radially outward into an enhanced position vis-à-vis the interior surface of the casing. In some embodiments this movable configuration of brush assemblies prevents the premature engagement of the brush with the inner surface of the casing as the assembly  10  is lowered through the well casing to the production zone. In some embodiments lowering the assembly  10  with the brushes fully engaged on the inner surface of the casing down the length of the casing can serve to both press undesirable amounts of debris or other materials into the production zone of the well (from upper portions of the well) and or undesirably wear out or bend the individual fibers of the brushes before the tool is actually positioned in the production zone of the well. In such an instance the scouring action of the brushes is diminished before the brushes reach the production zone of the well. 
         [0046]    As previously mentioned, the main body  11  may have an insert portion for receiving the fiber assembly holder  26  of the individual brush assembly  22 .  FIG. 4  shows a side view of an assembly  80  in accordance with embodiments of the present invention and  FIGS. 5A-5D  and  6  show cross-sectional views of the assembly  80 . As shown in  FIG. 6 , which is a detailed view of a portion of  FIG. 5A , a main body in the form of a hollow tube  82  has a recess or inset portion  84  that is formed into the outer circumferential surface  86  of the hollow tube. The inset portion  84  includes a first counter bore  88  having a first diameter  90 . The bottom surface  91  at the base of the first counter bore  88  provides a flat contact surface area that frictionally engages a brush assembly  110 . A holder portion  112  of the brush assembly  110  includes outer walls  114  that radius or bend inward at a radiused portion  116 . The radiused portion  116  surrounds a planar or flat portion  118 . When assembled, the flat portion  118  is pressed tightly against the bottom surface  91  at the base of the first counter bore  88 . 
         [0047]    At the base of the first counter bore  88 , there is a second counter bore  92  that extends further toward the center of the tube  82 . The second counter bore  92  has a second diameter  94  that is smaller than first diameter  90  of the first counter bore  88 . At the base of the first counter bore  92 , there is a threaded through hole  93  that extends to the hollow portion  96  at the center of the tube  82 . The first counter bore  88 , second counter bore  82 , and threaded hole  93  are concentric with each other. The threaded hole is adapted to receive an externally threaded portion  120  of the a brush assembly  110 . A circular boss  122  is located at the interface between the flat portion  118  and the threaded portion  120  of the brush assembly  110 . 
         [0048]    In some embodiments, the threaded portion  120  is the body of a screw or bolt that is removable from the holder portion  112  of the brush assembly  110 . As explained below, a removable bolt would allow the brush assembly  110  to be easily mounted at preselected torque and removed for replacement due to wear. The threaded body of the removable bolt extends through a bore formed through the flat portion  118  and the boss  122 . During assembly, the holder portion  112  may be seated into the inset portion  84  of the tube  82  without the bolt. The boss  122 , being fixedly secured to the flat portion  118 , provides a piloting function when fitting within the second counter bore  92 . The piloting function centers or aligns the bore in holder portion  112  with the threaded through hole  93  in the tube  82 . In this manner, the removable threaded body  120  of the bolt can be inserted through the bore and into the threaded hole  93 . The head  121  of the bolt is held on the other side of the flat portion  118  and is tightened to a preselected torque level to ensure sufficient fictional contact between the flat portion  118  and bottom surface  91  of the first counter bore  88 . The area of the brush assembly  110  which surrounds the head  121  of the bolt may be free of bristles to allow access to the head  121  for tightening and removal of the bolt. 
         [0049]    In some embodiments, the removable bolt is a 5/16″-18 hex head bolt and the threaded hole  93  is tapped to receive the 5/16″-18 thread of the bolt. Applicant has found that a 5/16″ diameter for the threaded portion  120  provides sufficient combination of strength that prevents the brush assembly  110  from being sheared or broken off the tube  82  during cleaning operations in a well casing and sufficient thread engagement to prevent loosening. 
         [0050]    In some embodiments, the first counter bore  88  has a depth  98  from the outer surface  86  that is at or about 0.375 inches, and the first diameter is at or about 1.375 inches. The depth  98  may be carefully selected so that bristles of a brush assembly extend radially outward beyond the outer surface  86  of the hollow tube  82  so as to make the overall outer diameter of the assembly  80 , measured from the tips of the bristles, greater than an inner diameter of the well casing or lining that is to be cleaned. In some embodiments, the bristles are of varying height and the overall outer diameter is measured from bristle tips that account for about 85% to 95% of the bristles. In some embodiments, the overall diameter as measured from 85% to 95% of the bristle tips is about 0.1 inches greater than the inner diameter (I.D.) of the casing to be cleaned. Applicant has found that having the overall diameter of the assembly  80  being 0.1 inch oversized relative to the well casing I.D. provides optimal cleaning results in many cases. In some embodiments, where the I.D. of the casing to be cleaned is about 5.5 inches, the overall diameter of the assembly  80  as measured from 85% to 95% of the bristle tips is at or about 5.6 inches. It will be appreciated that over sizing to a greater or lesser amount may be implemented as desired depending on the application, such as type of well, ground conditions, and other factors. 
         [0051]    In some embodiments, the second counter bore  92  has a depth  100  from the base of the first counter bore  88  that is at or about 0.15 inches. In some embodiments, the depth  100  may be selected so that the boss  122  on the holder portion  112  of the brush assembly  110  does not bottom out or make contact with the bottom surface at the base of the second counter bore  92 . That is, the depth  100  is selected to allow for a small gap to remain between boss  122  and the bottom surface of the second counter bore  92 . In this manner, as the threaded portion  120  is tightened into the threaded hole  93 , the flat surface  118  of the brush assembly  110  is free to press down completely and engage the bottom surface  91  of the first counter bore  88  so as to prevent the brush assembly  110  from rotating and becoming dislodged during cleaning operations in the well casing. 
         [0052]    In some embodiments, as shown in  FIG. 4 , the inset portions  84  are spaced axially apart along the length of the tube  82 . In the illustrated embodiment, the tube  82  includes sixteen inset portions  84  in which are mounted a corresponding number of brush assemblies  110 . At each axial position, there are two inset portions  84  facing at opposite directions. The two opposite facing inset portions  84  lie on the same plane that is oriented perpendicular or substantially perpendicular to the central axis  130  of the tube  82 . In the illustrated embodiment, there are a total of eight such planes each having two opposite facing inset portions  84 .  FIGS. 5A-5D  show the cross-section at four of those planes. 
         [0053]    As shown in FIGS.  4  and  5 A- 5 D, the pairs of inset portions  84  are oriented at various angular positions in a double helical pattern. Each pair of inset portions  84  is clocked or angularly offset by forty-five degrees from adjacent pairs of inset portions  84 . In  FIG. 5A , with the 12 o&#39;clock position designated at 0 degrees, the two inset portions  84  at plane  142  ( FIG. 4 ) may be described as being located at a 0-degree and a 180-degree position. In  FIG. 5B , the two inset portions  84  at plane  144  ( FIG. 4 ) may be described as being located a 45-degree position and a 225-degree position. In  FIG. 5C , the two inset portions  84  at plane  146  ( FIG. 4 ) maybe described as being located at a 90-degree position and a 270-degree position. In  FIG. 5D , the two inset portions  84  at plane  148  ( FIG. 4 ) may be described as being located at a 135-degree position and a 315-degree position. Thus it will be appreciated that every adjacent grouping of eight inset portions  84  encompasses a 360-degree cleaning coverage of a well casing in which an inset portion is located every 45 degrees. As shown in  FIG. 4 , the inset portions  84  overlap each other in the circumferential direction, as indicated for example by area  132 , thus providing for complete 360-degree cleaning coverage when brush assemblies  110  are mounted in each inset portion  84 . 
         [0054]    Applicant has found that with a well casing having an inside diameter of about 5 inches, optimal cleaning can be achieved with eight 1.4-inch diameter brush assemblies for every 360 degrees of cleaning coverage. In the illustrated embodiment of  FIG. 4 , there would be sixteen brush assemblies  110  installed, providing 720 degrees of cleaning coverage. That is, there are sixteen brush assemblies for an internal well casing circumference of seventeen inches, or about one brush for every 1.1 inches of internal circumference of a well casing. Thus, it will be appreciated that a greater or less number of inset portions  84  and corresponding brush assemblies  110  may be implemented to allow for 360-degree cleaning coverage, depending on the internal circumference of the well casing to be cleaned. In other embodiments, there is one brush assembly for every 1.2 to 2 inches of well casing internal circumference. In other embodiments, there is one brush assembly for every 0.5 to 1 inches of well casing internal circumference. 
         [0055]    Referring again to  FIG. 4 , the planes on which the pairs of inset portions  84  are located are axially spaced apart. As previously mentioned, the planes are oriented perpendicular or substantially perpendicular to the central axis  130  of the tube  82 . In some embodiments, the axial spacing between the planes is selected to prevent removed material, such as paraffin, wax, scale, or other residue on the inside of the casing of the well, from building up and gathering around the bristles of the brush assemblies  110  to an extent inhibits cleaning. In some embodiments, the axial spacing provides a helical or spiral channel between the brush assemblies  110  to allow the removed material and cleaning fluid to move away from the assembly  80  while in the well casing, thereby allowing for continuous high pressure flow of cleaning fluid. 
         [0056]    In some embodiments, a first plane  140  is located at an axial distance of about 3.38 inches from a first edge  83  of the tube  82 . The previously mentioned second plane  142  is located at an axial distance of about 6.44 inches from the first edge  83 .  FIG. 5A  shows the cross-sectional view through the second plane  142 . The previously mentioned third plane  144  is located at an axial distance of about 8.14 inches from the first edge  83 .  FIG. 5B  shows the cross-sectional view through the third plane  144 . The previously mentioned fourth plane  146  is located at an axial distance of about 9.84 inches from the first edge  83 .  FIG. 5C  shows the cross-sectional view through the fourth plane  146 . The previously mentioned fifth plane  148  is located at an axial distance of about 12.9 inches from the first edge  83 .  FIG. 5D  shows the cross-sectional view through the fifth plane  148 . A sixth plane  150  is located at an axial distance of about 14.6 inches from the first edge  83 . A seventh plane  152  is located at an axial distance of about 16.3 inches from the first edge  83 . A eighth plane  154  is located at an axial distance of about 19.4 inches from the first edge  83 . 
         [0057]    Still referring to  FIG. 4 , the tube  82  includes a plurality holes  160  which provide outlets for cleaning fluid flowing through the central passage  96  of the tube  82 . The outlet holes  160  are arranged in series along several circumferential ring patterns on the outer surface  86  of the tube  82 . Each circumferential pattern or ring lies on an outlet plane oriented perpendicular or substantially perpendicular to the central axis  130  of the tube  82 . 
         [0058]    In the illustrated embodiment of  FIG. 4 , the outlet holes  160  are concentrated in three jetting zones  184 A, B, C, each of the zones comprising twelve outlet holes  160 . The twelve outlet holes  160  are centered on a pair of outlet planes that oriented perpendicular or substantially perpendicular to the central axis  130  of the tube  82 . One of these outlet planes is designated as line  7 - 7  in  FIG. 4  and a cross-sectional view at this plane is shown in  FIG. 7 . Each outlet plane includes six outlet holes  160 . The pair of outlet planes are spaced apart axially. The axial spacing between the outlet planes (i.e., the axial spacing between outlet holes  160 ) may be selected as a balance between, on one hand, maintaining sufficient strength and structural integrity of the tube  82 , and on the other hand, maximizing the number of outlet holes  160  to provide cleaning coverage of the well casing circumference. In the illustrated embodiment, the axial spacing between planes of each pair is at or about 0.4 inches. Further, each jetting zone  184 A, B, C is axially spaced apart from an adjacent jetting zone. The axial spacing between each jetting zone  184 A, B, C may be selected as a balance between, on one hand, maximizing fluid flow out of each jetting zone without inhibiting or significantly affecting fluid flow from an adjacent jetting zone, and on the other hand, minimizing the overall axial length of the assembly  80 . In the illustrated embodiment, the first jetting zone  184 A is at least about 6 inches from the second jetting zone  184 B, which is about 6 inches from the third jetting zone  184 C. 
         [0059]    As shown in  FIG. 7 , each outlet plane includes six outlet holes  160 . The outlet holes  160  are equally spaced apart from each other by about 30 degrees. For a well casing having an internal diameter of about 5.5 inches, there are six outlet holes  160  distributed around an internal well casing circumference of 17 inches. That is, for each outlet plane, there is one outlet hole for about every 3 inches of internal well casing circumference. As previously mentioned each jetting zone  184 A, B, C includes two outlet planes. As shown in  FIG. 8 , the outlet holes  160  of one outlet plane (illustrated with solid lines) are clocked or offset by 30 degrees from the outlet holes  160  of the immediately adjacent outlet plane (illustrated with broken lines). Thus, each jetting zone, which includes two outlet planes, provides twelve outlet holes  160  distributed around an internal well casing circumference of 17 inches. That is, for each jetting zone  184 A, B, C, there is one outlet hole for about every 1.4 inches of internal well casing circumference. It will be appreciated that a greater or less number of outlet holes  160  may be implemented depending on the internal circumference of the well casing to be cleaned. In some embodiments, there is one outlet hole  160  for about every 0.7 to 1.3 inches of internal well casing circumference. In some embodiments, there is one outlet hole  160  for about every 1.5 to 2 inches of internal well casing circumference. 
         [0060]    In some embodiments the outlet holes  160  and nozzles  170  in one jetting zone is clocked or offset at an preselected angle from the outlet holes  160  and nozzles  170  of adjacent jetting zones.  FIG. 8  shows the angular positions of the outlet holes  160  and nozzles  170  for one of the jetting zones  184 C. For the adjacent jetting zone  184 B, the angular positions of the outlet holes  160  and nozzles  170  can be clocked or offset by an angle of about 10 degrees from what is shown in  FIG. 8 . For the third jetting zone  184 A, the angular positions of the outlet holes  160  and nozzles  170  can be clocked or offset by an angle of about 20 degrees from what is shown in  FIG. 8 . In this manner, the entire assembly  80  provides a high pressure jet of cleaning fluid at every 10 degree position. For a well casing having an I.D. of 5.5 inches, there would be 36 nozzles  170  for every 17.3 inches of well casing internal circumference. That is, for the entire assembly  80 , there is one nozzle for about every 0.5 inches of well casing internal circumference. In some embodiments, the entire assembly  80  provides one nozzle  170  for every 0.1 to 0.4 inches of well casing internal circumference. In some embodiments, the entire assembly  80  provides one nozzle  170  for every 0.6 to 1 inch of well casing internal circumference. 
         [0061]    Referring again to  FIG. 8 , each outlet hole  160  includes a counter bore  162  and an internally threaded hole  164  that extends from the base of the counter bore to the hollow portion or central fluid passageway  96  of the tube  82 . The outlet hole  160  is shaped to received a nozzle  170 , shown in  FIGS. 9A-D . The counter bore  162  is sized to received a nozzle outlet portion  172  and the threaded hole  164  is configured to engage an externally threaded portion  174  of the nozzle  170 . In some embodiments, the counter bore  162  has a depth  166  that may be selected such that an outermost tip of the nozzle outlet portion  172  extends radially outward and away from the outer surface  86  of the tube  82  by a distance of about 0.25 inches, leaving a gap of about 0.5 inches between the nozzle tip and the interior surface of a well casing to be cleaned. It will be appreciated that the nozzle tip may protrude outward at lesser or greater distances. 
         [0062]    In some embodiments, as shown in  FIG. 9A-D , the nozzle  170  has the shape of a hexagon-head bolt with side walls that can be engaged by a torque wrench or other tool to allow for installation and removal of the nozzle for cleaning and replacement. In some embodiments, the nozzle  170  is about one inch in length, with the nozzle outlet portion  172  and the threaded portion  174  being about 0.5 inches each in length. The side walls  176  of the hexagon-shaped outlet portion  172  may have a wall-to-wall distance  178  of about 0.5 inches and a point-to-point distance  180  of about 0.6 inches, which allows rotation of the outlet portion  172  within a 0.625-inch diameter of the counter bore  162  of the outlet holes  160 . A fluid passageway  182  formed through the nozzle  170  tapers down in three segments: an inlet segment  184  having a first diameter, an outlet segment  186  having a second diameter smaller than the first diameter, and a constriction or tapered segment  188  disposed between the inlet and outlet segments and providing a transition from the first diameter to the second diameter. The tapering down or narrowing of the fluid passageway  182  facilitates high pressure flow of cleaning fluid out toward the well casing. The second diameter may be selected to maintain a balance between, on one hand, having sufficient clean fluid flow volume and pressure, and on the other hand, maintaining strength and structural integrity of the threaded portion  174  to prevent the nozzle outlet portion  172  from shearing off the tube  82  during cleaning operations inside the well casing. In some embodiments the first diameter is about 5/64 inch and the second diameter is about ⅛ inch and 0.6 inches deep. In some embodiments, the threaded portion  174  has a ¼″-20 NC thread and the threaded hole  164  ( FIG. 8 ) in the tube  82  is tapped to a corresponding thread configuration. 
         [0063]    As shown in  FIGS. 9C and 9D , the outlet portion  172  of the nozzle  170  includes an annular groove  190  configured to receive a resilient O-ring seal when in an undeformed or natural state. The annular groove  190  may be sized to allow the entire O-ring to fit inside of it. In some embodiments, the depth  192  of the groove may be selected to be less than the thickness of the O-ring, and the inner and outer diameters of the groove may be selected to allow space for the O-ring to radially expand. During installation of the nozzle  170  in one of the outlet holes  160  in the tube  82 , the O-ring is placed in the annular groove  190  and a tool is used to engage the side walls  176  of the outlet portion  172  and rotate the nozzle  170  to a preselected torque at which the base of the head portion contacts the bottom of the counter bore  162  ( FIG. 8 ) of the outlet hole  160 . At the preselected torque level, the O-ring is squeezed due to the relatively shallow depth  192  of the annular groove  190 . As the O-ring is squeezed, it may expand to fill the space within the annular groove  190 , thereby creating a fluid tight seal. In some embodiments, the O-ring has a thickness of about 0.07 inches, an inner diameter of about 0.24 inches, and an outer diameter of about 0.38 inches. In some embodiments, the annular groove has a depth  192  of about 0.055 inches, an inner diameter of about 0.25 inches and an outer diameter of about 0.41 inches. 
         [0064]    In some embodiments, as shown in  FIGS. 10A-10C , a brush assembly  110 ′ may be retractable or capable of piston-like movement. In operation, while the assembly  80  is being lowered to the desired production area that requires cleaning, the brush assembly  110 ′ is in a retracted position as shown in  FIGS. 10A and 10C , thereby avoiding undue wear and degradation of the bristles before the assembly  80  reaches the area to be cleaned, which may be several hundred to thousands of feet below the well surface. When cleaning fluid is introduced into the central fluid passageway  96 , pressure from the fluid may force the brush assembly  110 ′ radially outward to an extended position ( FIGS. 10B and 10D ), away from the center of the tube  82 , thereby pressing the bristles of the brush assembly against the inner surface of the well casing to be cleaned. 
         [0065]    Retraction may be accomplished using a piston-type assembly that includes inserts  200  that are bolted to the body of the tube  82 . Sealing elements  202 , such as O-rings, may be used between sliding surfaces of the insert and the stem  120 ′ of the brush assembly  110 ′. The stem  120 ′ may include a locking element  204  that limits the radially outward movement of the brush assembly. 
         [0066]    In other embodiments, as shown in  FIG. 10C , the retractable brush assembly  110 ′ may be biased to be in the retracted position by a spring  210  disposed between the locking element  204  and the inserts  200 . In this fashion, the brush assembly  110 ′ remains in the retracted position until a threshold level of fluid pressure is present in the central fluid passageway  96 . 
         [0067]    In some embodiments, as shown in  FIG. 10D , the retractable brush assembly  110 ′ may be biased to be in the extended position by a spring  220  disposed between the inserts  200  and the bottom, flat surface  118 ′ of the holder portion of the brush assembly  110 ′. In this fashion, the brush assembly  110 ′ may retract when it reaches a bend or turn in the well casing, thereby allowing the cleaning assembly tool  80  to pass the bend and reach the area of the well casing that requires cleaning. 
         [0068]    In some embodiments, as shown in  FIGS. 11A-11D , nozzles  170 ′ may be retractable or capable of piston-like movement. In operation, while the assembly  80  is being lowered to the desired production area that requires cleaning, each nozzle  170 ′ is in a retracted position as shown in  FIGS. 11A and 11C , thereby avoiding possible damage before the assembly  80  reaches the area to be cleaned. When cleaning fluid is introduced into the central fluid passageway  96 , pressure from the fluid may force the nozzles  170 ′ radially outward to an extended position ( FIGS. 11B and 11D ), away from the center of the tube  82 , thereby bringing high pressure jets of cleaning fluid closer to the inner surface of the well casing to be cleaned. 
         [0069]    Retraction may be accomplished using a piston-type assembly that includes inserts  200 ′ that are bolted to the body of the tube  82 . Sealing elements  202 ′, such as O-rings, may be used between sliding surfaces of the inserts  200 ′ and the stem  174 ′ of the nozzle  170 ′. The stem  174 ′ may include a locking element  204 ′ that limits the radially outward movement of the nozzle. 
         [0070]    In other embodiments, as shown in  FIG. 11C , the retractable nozzle  170 ′ may be biased to be in the retracted position by a spring  210 ′ disposed between the locking element  204 ′ and the inserts  200 ′. In this fashion, the nozzle  170 ′ remains in the retracted position until a threshold level of fluid pressure is present in the central fluid passageway  96 . 
         [0071]    In some embodiments, as shown in  FIG. 11D , the retractable nozzle  170 ′ may be biased to be in the extended position by a spring  220 ′ disposed between the inserts  200 ′ and the bottom of the head portion  172 ′ of the nozzle  170 ′. In this fashion, the brush assembly  110 ′ may retract when it reaches a bend in the well casing, thereby allowing the cleaning assembly tool  80  to pass the bend and reach the area of the well casing that requires cleaning. 
         [0072]    A system  300  for improving pumping operations in accordance with embodiments of the present invention is shown in  FIGS. 12 and 13 .  FIG. 12  shows the system  300  disassembled, and  FIG. 13  shows the system  300  partially assembled. The system  300  comprises a hollow scratcher tube  302  having a plurality of outlet holes for holding high pressure nozzles and a plurality of inset portions for holding brush assemblies. The scratcher tube  302  is externally threaded at a bottom end  301  to allow it to be connected to another tool, such as a scraper, or to allow it to be capped off with an end cap. The scratcher tube  302  is also externally threaded at an inlet end  303  to allow it to be connected to a base sub  304 . A standard coupler  306  with internal threads at both ends may be used to connect the scratcher tube  302  to the base sub  304 . 
         [0073]    The base sub  302  is a hollow tube and includes external threads and internal threads at its inlet end  305 . The external threads allow the base sub  304  to be connected to a working string  310 . The working string  310  is a hollow tube which is used to lower the scratcher tube  302  to the region of a well casing that is to be cleaned and is used to deliver cleaning fluid to the scratcher tube. Another standard coupler  306  may be used to connect the inlet end  305  of the base sub  304  to the working string  310 . The internal threads at the inlet end  305  of the base sub  304  allow the base sub  304  to be connected to a tubular filter  308 . The tubular filter  308  is hollow includes cylindrical walls made of fine stainless steel mesh. Cleaning fluid delivered down the working string  310  passes through the mesh of the cylindrical walls and exits through an outlet end  309  which is in fluid communication with the internal fluid passageway of the scratcher tube  302 . The outlet end  309 , which is internally threaded, is connected to the inlet end  305  of the base sub  304 . This connection may be accomplished using a stainless steel pipe  312  that is externally threaded at both ends. When assembled, as shown in  FIG. 13 , the filter  308  is located inside of the working string  310 . The filter  308  is sized so that there is a gap or space between its cylindrical walls and the internal circumference of the working string  310 . In this manner, cleaning fluid delivered down into the working string  310  may easily pass into the filter  308 . The top end of the filter  308  may be covered by an end cap, or may be connected to another filter to allow for greater filtering capacity in order to support delivery of higher volumes of cleaning fluid to the scratcher tube  302 . 
         [0074]    In some embodiments, the system  300  may include a pressure valve disposed above the scratcher tube  302  and configured to limit or prevent delivery of fluid to the scratcher tube  302  unless a predetermined fluid pressure, referred to as an opening threshold pressure, is present in the working string  310 . The pressure valve may include a valve element that is biased to a closed position by a spring that pushes the valve element at a force level that corresponds to the opening threshold pressure. In some embodiments, the pressure valve is located within the base sub  304 . In some embodiments, the pressure valve is located within the pipe  312  between the base sub  304  and the filter  308 . By controlling the fluid pressure in the working string  310 , cleaning fluid may be prevented from flowing out of the scratcher tube  302  while the scratcher tube  302  is being lowered into the well casing before reaching the region to be cleaned. In this manner, the amount of cleaning fluid that is wasted can be reduced. Also, the quantity of cleaning fluid that enters the geological formation can also be minimized if desired. 
         [0075]    In some embodiments, the system  300  may include a choke device that limits or prevents delivery of fluid to the scratcher tube  302  when the fluid pressure inside the working string  310  is excessive. In this way, damage to nozzles and any piston-type assemblies on the scratcher tube  302  due to a sudden pressure shock may be avoided. 
         [0076]    As shown in  FIG. 12 , the outlet holes and inset portions on the scratcher tube  302  may be positioned at a distance from the threaded ends that is sufficient to allow holding and turning tools, such as tongs, to engage the scratcher tube and facilitate assembly. The distance may from one to three inches. 
         [0077]    While particular embodiments of the invention and variations thereof have been described in detail, other modifications and methods will be apparent to those of skill in the art. Accordingly, it should be understood that various applications, modifications, and substitutions may be made of equivalents without departing from the spirit of the invention or the scope of the claims. Various terms have been used in the description to convey an understanding of the invention; it will be understood that the meaning of these various terms extends to common linguistic or grammatical variations or forms thereof. Further, it should be understood that the invention is not limited to the embodiments that have been set forth for purposes of exemplification, but is to be defined only by a fair reading of claims that will be appended, including the full range of equivalency to which each element thereof is entitled. 
         [0078]    While several particular forms of the invention have been illustrated and described, it will also be apparent that various modifications can be made without departing from the scope of the invention. It is also contemplated that various combinations or subcombinations of the specific features and aspects of the disclosed embodiments can be combined with or substituted for one another in order to form varying modes of the invention. Accordingly, it is not intended that the invention be limited, except as by the appended claims.