Abstract:
An aperture design minimizes erosion on the surrounding casing and to the aperture itself and is particularly effective in fluid injection wells where large volumes of fluids over a long period of time with entrained solids are expected to be pumped through. The preferred design is an elongated shape with a flaring wider in the downhole direction. The downhole end of the opening features an exit that flares in the downhole direction with multiple slopes with an arc transition. Other options for the opening configuration are envisioned.

Description:
PRIORITY INFORMATION  
       [0001]     This application claims the benefit of U.S. Provisional Application No. 60/576,355, filed on Jun. 2, 2004. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The field of this invention is aperture shape for downhole valves or ported flow control tools and more particularly valves or tools of the sliding sleeve type for use in fluid injection wells.  
       BACKGROUND OF THE INVENTION  
       [0003]     When production becomes marginal in a given zone in a field, one way to bolster production is to inject large quantities of fluid such as water or steam into an injection well at one point in the zone or zones in question and take additional production in another well or wells in the field. In the injection well pumping equipment is used to move large amounts of fluid into the well to get the desired enhanced production. The injection well can have a valve, typically of a sliding sleeve design, to allow access into a single zone at a time and in turn service multiple zones, if desired. These sliding sleeve valves have a sleeve with a port where the port can be selectively brought into alignment with the housing around it. The injection well can have a service life as long as 15 years or more. In the course of its life span, high fluid volumes and large weights of entrained solids can be forced through a single sliding sleeve valve, when it is in the open position. It would not be unusual that in the life of such a well injection rates of about 45,000 barrels per day would be used. This could result in 250 million barrels pumped during the life of the well. Additionally, with solids content of about one pound per 1000 barrels the amount of solids pumped through such an opening could reach 250,000 pounds of fine sand, generally smaller than 50 micron and having a generally sharp and angular shape, being pumped through the open port in the expected life of the well.  
         [0004]     Maintaining these rates over long periods has raised concerns about erosion of the opening in the tool and more significantly to the surrounding casing  
         [0005]     In the past, other work has been done relating to crossover tools used in high rate high volume frac packing, as reported in the American Association of drilling Engineers (AADE) paper 03-NTCE-18 in 2003 by a group of engineers from Halliburton Energy Services Inc. In this application there are high flow volumes with significantly more solids content than in fluid injection applications. In the design tested in this paper, both the tool body and the sliding sleeve had matching ports that were created by simply angling a drill at a predetermined angle from the axis of the tool and drilling in an uphole direction through the tool body and the sleeve. This technique results in an oval shaped opening when viewed in a line perpendicular to the tool axis. The hole appears narrower at the top and bottom because of the slant in the drilling process and having generally parallel slopes at the uphole and downhole ends, again resulting from the slant drilling technique. While positive results were reported for high flows and high solids content application of frac packing, the overall volumes of fluid pale in comparison with the volumes of fluid and solids used during the life of an injection well.  
         [0006]     As a result of these differences simulations (such as CFD, Computational Fluid Dynamic models or simulations were run to evaluate port effectiveness) and field tests have led to an improved port design to minimize erosive effects on the surrounding casing and to the ports themselves. The resulting port designs feature elongated openings that flare in the downhole direction. It further can feature a multi-sloped downhole outlet composed of ramps or/and curves. These and other features of the invention will be more readily appreciated by those skilled in the art from a review of the description of the preferred embodiment and the claims that appear below.  
       SUMMARY OF THE INVENTION  
       [0007]     An aperture design minimizes erosion on the surrounding casing and to the aperture itself and is particularly effective in fluid injection wells where large volumes of fluids over a long period of time with entrained solids are expected to be pumped through. The preferred design is an elongated shape with a flaring wider in the downhole direction. The downhole end of the opening features an exit that flares in the downhole direction with multiple slopes with an arc transition. Other options for the opening configuration are envisioned. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  is an isometric view of the preferred embodiment;  
         [0009]      FIG. 2  is a section through the assembly along line  2 - 2  of  FIG. 1 ;  
         [0010]      FIG. 3  is a plan view of the aperture shown in section in  FIG. 2 ;  
         [0011]      FIGS. 4-7  show progressively better performing designs that are an alternative to that shown in  FIGS. 1-3  but each representing a design that is less favored on a performance basis than the preferred embodiment. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0012]      FIG. 1  shows an exterior view of the aperture  10  in the housing  12 . A conforming opening is located on the sliding sleeve (not shown) that can be moved between an open position and a closed position with a known tool. One or more assemblies may be mounted on a single string in a wellbore to allow selection of the zone into which the fluid is to be pumped for injection purposes. Surrounding this structure shown in  FIGS. 1-3  is generally casing (not shown). The flow comes out of the aperture  10  and into the cased surrounding wellbore. Aperture  10  has an uphole end  14  and a downhole end  16 . The number of apertures can be varied to accommodate the anticipated flow rates to keep the velocity in a desired range. A range of about 35-65 feet per second is preferred.  
         [0013]     Referring to  FIGS. 2 and 3  it can be seen that the aperture  10  has an elongated shape. From the inside looking out, in  FIG. 2 , the aperture  10  has a ramp  18  that is preferably at 45 degrees. While a single planar surface is shown for ramp  18  it is also possible to use multiple ramps with or without intervening transitional surfaces. Alternatively a combination of planar and arcuate surfaces can be used where the arcs are at a constant or varying radii. It is preferred that the larger radii be further uphole, if used on surface  18  so that at the outside surface  20  of the body  12  the curvature will be more pronounced.  
         [0014]     At the downhole end  16  the preferred configuration of surface  22  between the inside surface  24  and the outside surface  20  is an initial ramp  26  of about 55 degrees followed by an arcuate segment  28  at about an inch and a quarter radius followed by an exit ramp  30  at about 15 degrees.  
         [0015]      FIG. 3  shows the aperture  10  flaring out at a constant angle of about 10 degrees making the aperture  10  wider near the downhole end  16  than at the uphole end  14 .  
         [0016]     While these combinations of parameters represent the preferred embodiment other possibilities are within the scope of the invention. As one example the aperture  10  shape may feature a flaring wider from uphole to downhole end regardless of the flaring being along a straight line, an arc, a combination of a line or lines and an arc and where the arc segments have the same or varying radii. Furthermore, the surfaces can be arranged in any order going between inside surface  20  and outside surface  24 . This feature alone without the other illustrated features of  FIGS. 1-3  will perform better from a minimizing erosion point of view than a simple rectangular opening, shown in  FIG. 4 , that has parallel sides  32  and  34  and hence no flaring of a generally rectangular opening. Note in  FIG. 4  that uphole surface  36  and downhole surface  38  are flat and are each a single ramp with both oriented perpendicularly to the axis of the tool While surface  36  &amp;  38  are actually shown with perpendicular 90 degree ramp angle, they could be reoriented to improve performance by orienting both of them in down hole direction. While a flare angle of 10 degrees is preferred the flare angle can vary with the diameter of the body  12 , the number and length of apertures  10  and the need to accommodate control lines (not shown), which are mounted out of the trajectory of coursing fluid through the apertures  10 . Thus straight taper angles from about a degree to about 30 degrees are contemplated while even larger angles are also possible. This flare angle could also increase for the same port in a direction toward downhole by disposing increased angles in the down hole direction or gradual arcing or any combination of the two.  
         [0017]     Another feature that can also stand-alone and produce erosion-minimizing properties, apart from the flare along the length discussed above, is the shape of the exit at the lower end  16 . The base feature is to include more than a single surface. A single flat exit surface  42  is shown in  FIG. 6 . It should be noted that although the opening in  FIG. 6  gets wider from the inside of body  12  to outside as indicated by lines  44  and  46 , in this view those lines are parallel so that there is no flaring of the width in the  FIG. 6  design. Accordingly, just improving the exit at the lower end  16  of the aperture  10  without making the other modifications described, will yield erosion minimization. More than a single surface can be accomplished by two flat surfaces with the surface closest to the inside  24  of body  12  having the steeper angle. This feature is also illustrated with surface  46  being steeper than surface  48  in  FIG. 5 . Other alternatives envision flat surfaces with line transitions or arcuate surfaces of differing radii or combinations of flat and arcuate surfaces in any order and involving the same or different radii on the arcuate surfaces. Alternatively a single arc at a constant radius is possible as well as what looks like a single arc but is really a combination of arcs of different radii is also envisioned.  
         [0018]     The upper end  14  can also have the same options as outlined for the lower end  16  and if that is the only feature used it will still help to minimize erosion but likely with less effect as a similar change done by itself in the manner described above to the lower end  16 .  
         [0019]     Of course, it would be more preferred to address the upper and lower ends  14  and  16  in each aperture either with similar surface, if not angle or radii combinations, however, the surface treatments at the ends need not be duplicates of each other. Indeed they are not as shown in the section view of  FIG. 2 . Using the two planar surface variation for the end treatment, the initial ramp can be in the range of about 50 to 90 degrees with 80 degrees being closer to optimal and the final ramp in the direction of flow can be between about 1 to 50 degrees.  
         [0020]     The designs of  FIGS. 5-7  represent alternatives within the scope of the invention that show some different permutations over the basic design of an elongated opening, preferably rectangular that still performs better than the known prior art of drilling a hole using a drill held on a slant to the long axis of the housing.  FIG. 4  is a basic design similar to a current product, which differs by having rounded uphole and downhole ends instead of flat/square ends. A feature of the prior art Halliburton ports is that they require multiple ports in series in a direction downstream, with the port sizes reduced in the downstream direction. Reduced port sizes downstream forces more flow through the up hole ports, which would otherwise see significantly reduced flow velocities. The downstream ports would otherwise erode most.  
         [0021]     The above description is illustrative of the preferred embodiment and the full scope of the invention can be determined from the claims, which appear below.