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BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates generally to wellbore injection tools and methods for injection of wellbore chemicals or other fluids and/or solids. 
   2. Description of the Related Art 
   Wellbore injection tools are used to inject solvents, proppants, or other materials within a formation of earth surrounding a wellbore. Typically, such injection is used to increase the potential recovery of hydrocarbons from a formation. Injection tools can also be used to inject waste fluids into the earth. 
   SUMMARY OF THE INVENTION 
   The invention provides methods and devices for selective injection of fluids and/or solids into a formation. In particular aspects, the invention provides devices and methods for flowing such injection fluids and/or solids along a formation interval of a particular length so that the flow is substantially equalized along that length. 
   In a currently preferred embodiment, an injection wash tool is incorporated into a downhole injection string. The wash tool includes a plurality of interconnectable wash tool segments. Each of the segments provides a flow applicator nozzle for transmitting fluid/and or solid from the interior flowbore of the wash tool and into the surrounding formation. In a preferred embodiment, the flow applicator features a plurality of nozzle pipes and nozzles, which are oriented about the cross-sectional circumference of the segment in an angularly spaced orientation to provide for a flow pattern that is substantially equalized in an angular manner. In a preferred embodiment, the nozzle pipes have a length that extends into the flowbore of a neighboring wash tool segment. 
   Also in a currently preferred embodiment, the injection wash tool features a plurality of wash tool segments, each of which are interconnectable with other segments, to form wash tools of different required lengths, so as to correspond to various formation interval lengths. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The advantages and further aspects of the invention will be readily appreciated by those of ordinary skill in the art as the same becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference characters designate like or similar elements throughout the several figures of the drawing and wherein: 
       FIGS. 1A and 1B  are a side, quarter cross-sectional view of an exemplary equalizing injection tool constructed in accordance with the present invention. 
       FIG. 2  is a side, cross-sectional view of an exemplary wash tool segment constructed in accordance with the present invention. 
       FIG. 3  is an axial cross-section of the wash tool segment of  FIG. 2 , taken along lines  3 - 3  in  FIG. 2 . 
       FIG. 4  is an external, isometric view of a pair of exemplary wash tool segments illustrating how the segments are fit together. 
       FIG. 5  is an axial cross-sectional view of the pair of wash tool segments shown in  FIG. 4 , taken along the lines  5 - 5 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1A and 1B  illustrate an exemplary wellbore  10  which has been drilled through the earth  12  and into a hydrocarbon-bearing formation  13 . The wellbore  10  is lined with metallic casing  14 . A number of perforations  16  have been formed through the casing  14  and into the formation  13 . The perforations  16  are formed using any of a number of perforation tools well known in the art and permit fluid communication from the surrounding formation  13  through the casing  14  and into the wellbore  10 . It is noted that the formation  13  has an upper limit  18  and a lower limit  20 . The vertical distance “d”, or formation interval, is the distance between the upper and lower limits  18 ,  20 , and will vary according to the particular formation. 
   An exemplary equalizing production and injection tool  24 , constructed in accordance with the present invention, is shown disposed within the wellbore  10 . An annulus  25  is defined between the wellbore  10  and the tool  24 . The tool  10  is incorporated into a string of production/injection tubing  26  which extends downwardly into the wellbore  10  from a surface wellhead (not shown) as known in the art. A service packer  28  is affixed to the lower end of the tubing  26  and is depicted in a set position in  FIG. 1A . An upper cross-over tool  29  is secured below the packer  26 . A section of tubing  30  interconnects the upper cross-over tool  29  to a sliding sleeve valve production nipple  32 . A suitable sliding sleeve device for use as the sliding sleeve valve  32  is the CMD sliding sleeve available commercially from Baker Oil Tools of Houston, Tex. The sleeve valve  32  is used during the production phase of operations to draw in production fluids into the central flowbore  35  of the tool  10  from the surrounding wellbore  10 . A section of tubing  34  interconnects the sleeve valve  32  with a seating nipple  36 . The seating nipple  36  is used to seat and locate a wireline setting tool (not shown) that is used to operate the sleeve valve  32 . A lower cross-over sub  38  is secured to the lower end of the seating nipple  36 . 
   An exemplary modular wash tool, generally indicated at  40 , is secured below the cross-over sub  38 . At the lower end of the wash tool  40  is a bull nose closure plug  42 . The wash tool  40  is generally made up of a plurality of independent wash tool segments  44 , which are interconnectable to form a wash tool  40  of various lengths. In the embodiment depicted in  FIGS. 1A and 1B , there are eight wash tool segments  44 . The wash tool segments  44  include housings  45  which are interconnected by intermediate subs  46 . As can be seen in  FIGS. 1A and 1B , the made up length of the wash tool  40  approximates the vertical distance “d” of the formation interval. As a result, exterior spray nozzles associated with the wash tool  40  will be distributed in substantially regular spaced intervals along the entire length of the formation interval “d”. 
   Referring now to  FIGS. 2 and 3 , an exemplary wash tool segment  44  is depicted in greater detail. The wash tool segment  44  includes the generally cylindrical housing  45  is which defines a central flowbore  50  with internally threaded portions  52 ,  54  for removable connection of the intermediate subs  46 . In a currently preferred embodiment, the housing  45  is an elongated 2⅞″ 6.4 ppf NU 10rd collar which is available commercially from Baker Oil Tools of Houston, Tex. However, other diameters, sizes and shapes for the housing  45  may be used, as required by the user. Exterior nut fittings  56  secure curved nozzle pipes  58  within openings  60  in the housing  45 . The nozzle pipes  58  have a central curved portion  62  which separates a radial leg portion  64  and an axial leg portion  66 . In a currently preferred embodiment, the nozzle pipes  58  are ⅜″×0.049″ (thickness) stainless steel tubing. Each individual segment  44  also includes one intermediate sub  46  which is affixed to the housing  45 . Additionally, each of the nozzle pipes  58  provides a nozzle end  68  that provides for a distributed spray pattern for fluids/solids exiting the nozzle pipe  58 . 
   It is preferred that the nozzle pipes  58  have a length that is approximately equal to the axial length of two segments  44  plus 6 inches. This length of nozzle pipe  58  provides an optimum length for application and delivery of fluids and suspended solids as well as for equalization of flow rate along the length of the formation interval “d”. In a further preferred embodiment, the axial leg portion  66  is at least 8 feet long in order to create a fluid pressure drop to increase the flow rate radially outwardly into the annulus  25 . 
   As can be best seen in  FIGS. 2 and 3 , the nozzle pipes  58  are distributed in an angular spaced relation about the circumference of the housing  45 . In the embodiment depicted in  FIGS. 2 and 3 , there are four nozzle pipes  58  and they are equally spaced at approximately 90 degrees apart from one another. This angular spaced relation permits an optimal flow pattern for fluid and/or solids exiting the nozzles  58 . 
   Because the axial leg portions  66  of the nozzle pipes  58  have a length that is greater than that of a wash tool segment  44 , they will extend into the flowbore  50  of a neighboring wash tool segment  44 .  FIGS. 4 and 5  illustrate a method of accomplishing this while assuring that the nozzle pipes  58  of adjoining sections do not interfere with each other.  FIG. 4  depicts an upper wash tool segment  44   a  that is joined to the upper portion of a lower wash tool segment  44   b . As seen in  FIG. 4 , the upper wash tool segment housing  45   a  is rotated with respect to the lower wash tool segment housing  45   b  approximately 45 degrees. This causes the exterior fittings  56   a  and nozzle pipes  58   a  of the upper wash tool segment  44   a  to be offset approximately 45 degrees from the exterior fittings  56   b  and pipes  58   b  of the lower wash tool segment  44   b . As a result, the axial leg portions  66   a  of the upper wash tool segment  44   a  will be disposed angularly between the nozzle pipes  58   b  of the lower wash tool segment  44   b , thereby accommodating the longer length. 
   Manufacture of wash tool segments  44  is conducted by selecting nozzle pipes of a suitable length and then bending the pipes to form a generally 90 degree angle  62 . The outer nuts  56  are then used to secure the nozzle pipes  58  within the housing  45  of each segment  44 . A number of wash tool segments  44  are then assembled in an end-to-end fashion to form the wash tool  40 . The wash tool  40  will have an axial length which approximates the vertical length “d” of the formation interval. 
   In operation, a wash tool  40  is assembled at the surface of the wellbore and incorporated into the injection tool  24  and production tubing string  26 . The wash tool  44  is assembled to have a length “l” that approximates the formation interval “d”. It is noted that the formation interval “d” may be the depth of an entire production formation  13  or some portion thereof, as determined by an operator at the surface. The wash tool  40  is is assembled from a number of separate, like wash tool segments  44 , as described above. The necessary number of segments  44  are affixed to one another to approximate the formation interval “d”. The string  26  is then disposed into the wellbore and the injection tool  24  lowered until the wash tool  40  is located within the desired hydrocarbon-bearing formation  13 . Next, the packer device  26  is set against the casing  14  of the wellbore  10  to secure the wash tool  40  substantially within the production interval “d”. Fluids containing proppants, gravel or other suspended solids are then pumped down through the central flowbore  35  and through cross-over tools  29  and  38 , in a manner known in the art of wellbore injection. These fluids then enter the wash tool  40 , under pressure, and specifically, the central flowbore  50  of each of the interconnected segments  44 . Due to the narrowness of the nozzle pipes  58 , pressure can build within the confines of the wash tool  40 . Because the combined flow area of the nozzle pipes  58  is less than the flow area of the inside of the wash tool  40 , a flow restriction is created and pressure is allowed to build inside of the wash tool  40 . Pressurized fluid within the wash tool  40  will enter the axial leg portions  66  of each of the nozzle pipes  58  and be transmitted through the nozzle pipes  50  to the nozzle ends  68  and is sprayed radially outwardly therefrom into the annulus  25  and perforations  16 . The pressurized fluid flows from the confines of the wash tool  40  into the nozzle pipes  58 . As the fluid in each nozzle pipe  58  travels along a path of substantially identical length, diameter and angle as the other nozzle pipes  58 , the pressure and flow rates of the fluid in each of the nozzle pipes  58  becomes substantially equal. Optimum spray patterns for the particular formation  13  are provided as a result of the tailored length “l” of the wash tool  44 , the spaced angular distribution of the nozzles  68  about the circumference of each housing  45 . Upon completion of the injection operation, production of fluid from the surrounding formation may be commenced through the production nipple  32 , in a manner well known in the art. 
   The foregoing description is directed to particular embodiments of the present invention for the purpose of illustration and explanation. It will be apparent, however, to one skilled in the art that many modifications and changes to the embodiment set forth above are possible without departing from the scope and the spirit of the invention.

Summary:
An equalizing injection wash tool includes a plurality of interconnectable wash tool segments. Each of the segments provides a flow applicator nozzle for transmitting fluid/and or solid from the interior flowbore of the wash tool and into the surrounding formation. Each segment preferably features a plurality of nozzle pipes and nozzles which are oriented about the cross-sectional circumference of the segment in an angularly spaced orientation to provide for a flow pattern that is substantially equalized in an angular manner. In a preferred embodiment, the nozzle pipes have a length that extends into the flowbore of a neighboring wash tool segment.