Abstract:
A tool for forming an obstruction in the production casing of an oil or gas well includes a sleeve adapted to be secured to the casing and having an annular abutting surface that captures a body or a cage having a solid body within the casing thereby forming an obstruction. The tool may be secured within the well either by an expandable sleeve or a collet having resilient fingers. The tool may be used as a plug to prevent flow through the production casing of the well in a well treatment process such as fracing. A process for treating a well using the tool is also presented.

Description:
[0001]    This is a Continuation-in-Part of application Ser. No. 13/605,298 filed on Sep. 6, 2012. 
     
    
     BACKGROUND OF INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention disclosed and claimed in this application relates to the treatment of oil and/or gas wells. One example of such treatment is commonly referred to as fracturing the formulation around an oil or gas well. Fluid with certain chemical additives and a proppant are injected into the formation surrounding either a vertical or horizontal well to form cracks or passageways in the formation to stimulate the production of the well. 
         [0004]    2. Description of Related Art 
         [0005]    Currently there are several techniques utilized to stimulate producing of a well by fracing. Typically a packer or plug is utilized to isolate a particular portion of the well and the fracing fluid is injected into the isolated portion under high pressure. Once a given portion of the well is treated in this manner, a second zone uphole of the first zone is isolated by a second packer or plug that cuts off flow to the downhole portion of the well that has been treated. 
         [0006]    U.S. Pat. No. 7,322,417 discloses a plurality of vertically spaced production layers 1 and a plurality of valves 14. A ball is captured on a valve seat 94 which will cause an increase in pressure to open valve 14. This allows fracturing fluids to enter the annular region that surrounds the valve. The balls may be formed of a dissolvable or frangible material, which allows the ball to be dissolved or eroded to open up communication upstream through the casing. 
         [0007]    U.S. Pat. No. 7,134,505 discloses a similar system in which a plurality of spaced apart packers 20 a-n and a plurality of valve bodies 26 c-n that capture balls of varying diameters to selectively open ports 16 c-e to allow fracturing fluids to flow into the isolated zones. 
         [0008]    Stage frac methods include the use of pump down bridge plugs, perforating guns, and sliding sleeves. The current pump down method requires a drill out phase after frac with coiled tubing or jointed pipe. This is an expensive and time consuming process which involves additional risk of the coil tubing getting stuck in the wellbore. This time and operational risk is a significant impact item on the overall economics of oil and gas projects. 
         [0009]    Sliding sleeves require that their exact position needs to be known as the casing is run into the well. The number of frac initiation points is limited and the cost is significant for each sleeve. Sleeves may malfunction either during opening or closing. Higher risk comes from incomplete frac distribution and limited reservoir drainage. 
       BRIEF SUMMARY OF THE INVENTION 
       [0010]    The present invention overcomes the difficulties with the prior art as described above by using proven concepts and a simplified approach. An expansible valve seat or stop member that can be run on wireline (pump-down, tractor, tubing or coiled tubing) is positioned at predetermined locations along the production casing and is expanded for example by a shaped charge or with a mandrel extrusion process. A disintegrating or dissolvable ball can be dropped in the valve seat to isolate a portion of the well to allow for fracturing of the isolated portions of the well. The seat may be made of the same material as the ball so that the drill out step is completely eliminated. Alternately, the valve seat may be mechanically captured by the production casing. 
         [0011]    The ball and valve seat become the frac plug that would normally be pumped down in a conventional horizontal pump-down process. 
         [0012]    The production casing can be perforated as in the pump down method and fracing can be initiated once the ball seals on the valve seat. A dart may be used in lieu of a ball. Balls, darts, seats or sleeves may be soluble, dissolvable or frangible. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
         [0013]      FIG. 1  is a flow diagram of the process according to an embodiment of the invention. 
           [0014]      FIG. 2  is a cross sectional view of expansible sleeve seat according to an embodiment of the invention. 
           [0015]      FIG. 3  is a cross sectional view of the sleeve seat deployed within the production casing with the ball. 
           [0016]      FIG. 4  is a cross sectional view of a second expansible sleeve seat and a dart. 
           [0017]      FIG. 5  is a cross sectional view of a third expansible sleeve seat and a ball. 
           [0018]      FIG. 6  is a cross sectional view of a fourth embodiment with an expansible sleeve and separate seat with a dart. 
           [0019]      FIG. 7  is a cross sectional view of a fifth embodiment of the invention. 
           [0020]      FIG. 8  is an end view of the embodiment of  FIG. 7 . 
           [0021]      FIG. 9  is a cross sectional view of a sixth embodiment of the invention. 
           [0022]      FIG. 10  is a cross sectional view of a further embodiment of the invention. 
           [0023]      FIG. 11  is a cross sectional view of yet a further embodiment of the invention. 
           [0024]      FIG. 12  is a cross sectional view of an embodiment of a connector sub. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]    As described below, the invention of this application is directed to a novel process of fracturing a plurality of zones in the formation surrounding a horizontal or vertical well without the use of multiple bridge plugs or frac plugs that require drill out after the fracturing process is complete prior to the production stage. 
         [0026]    This is accomplished in the following manner. After the well has been drilled ( 81 ) and the production casing has been fully positioned ( 82 ), an expansible sleeve such as shown in  FIG. 2  is placed at the desired location within the casing ( 83 ). As shown in  FIG. 2 , the expansible sleeve  10  consists of a relatively thin walled cylindrical tube  11  formed of a high tensile strength material similar to that of the production casing  21 . A ring of expansible material  12  may surround a portion of tube  11 . A cap  15  is positioned over the downhole end  16  of the tube so that the expansible sleeve  10  may be pumped into the well. The outside diameter of the ring  12  is slightly less that the inside diameter of the casing. Detonation cord  14  is wound about a frangible mandrel  13  positioned within the tube and includes an electrical cord  17  for detonation. Another embodiment of this invention may employ the use of an extrusion process using a mandrel and sleeve to create the seat as shown in  FIG. 3 . The resultant sleeve or seat installed in the production casing will be the same whether the installation process is expansive or extruded. 
         [0027]    Expansible sleeve  10  may be precisely positioned within the production casing by any suitable known technique such as a line counter or collar locator. Once positioned within the desired location of the production casing, the cord is detonated ( 84 ) causing the sleeve to expand outwardly against the inner surface of the casing ( 21 ). In so doing, the sleeve forms a seat  12  as shown in  FIG. 3  which is capable of catching and retaining a ball or dart as shown in  FIG. 3  and  FIG. 4  that is pumped down ( 86 ). The outer surface of tube  11  may be impregnated with a thin strip of no slip high strength metallic material. 
         [0028]    Once the tube  11  and seat have been set in place, the production casing and cement (if present) in the first frac zone can be perforated ( 85 ) in the conventional way by a perforating gun on the same tool-string as the expansible sleeve. At this point the tool-string can be removed, and the fracing process can be initiated by pumping down ( 86 ) a ball or dart to rest against seat  12 . This will prevent the fracing fluid from flowing downhole and will cause the fracing fluid under pressure ( 87 ) to enter the formation surrounding the perforations in the production casing and thus commence the fracing process. 
         [0029]    Once the process is completed for the first zone, a second expansible sleeve can be placed ( 88 ) to isolate a second zone and the process can be repeated ( 88 - 92 ) for as many zones as desired as indicated in  FIG. 1 . The ball, dart, seat or sleeve may be made of a soluble, dissolvable, or frangible material such that it would not be necessary to drillout the sealing mechanism after fracturing. The ball, dart, seat or sleeve would shrink in size or completely dissolve so that the constituents went into solution or were flowed back with the frac load water. 
         [0030]    Another embodiment of the expansible sleeve is illustrated in  FIG. 5 . In this embodiment, a tubular member is shown in an unexpanded condition at  45 . Chevron or swellable seals  43  are positioned about an uphole portion  44  of the sleeve  45 . Sleeve portion  45  is expanded by a mandrel or shaped charge into the position indicated at  46  against the inner surface of the casing  21 . In this embodiment the uphole portion  44  of the sleeve may have a beveled surface ( 47 ) against which ball  22  rests when a ball or dart is pumped down into the casing. 
         [0031]    An additional embodiment of the expansible sleeve is illustrated in  FIG. 6 . In this embodiment, a sleeve  11  is expanded in the production casing  21  and used as a stop or no-go for a secondary conical seat  51  that is either simultaneously or subsequently placed on the no-go. The perforations are then added. A ball or dart  32  is then landed on the seat forming the sealing mechanism for the wellbore and the stage is frac&#39;d. Secondary seat  51  may have an elastomeric annular seat  52  that engages a tapered portion  53  of the sleeve  11  to form a seal. This process can be repeated as many times as necessary to adequately stimulate the formation surrounding the wellbore. The ball, dart or seat in this embodiment may also be made of a soluble, dissolvable, or frangible material. 
         [0032]    A further embodiment of the invention can be described by reference to  FIGS. 7 and 8 . As with other embodiments, an expandable sleeve  10  is positioned and expanded within production casing  21  so that cylindrical tube  11  is secured to the casing. A cage member  65  having a ball  66  is then pumped down to a position where it rests on shoulder  53  of tube  11  as shown in  FIG. 7 . Cage member  65  has a hollow cylindrical portion  62  of slightly less diameter than the internal diameter of casing  21 . Cage member also has a hollow frustoconical portion  61  which terminates in an outlet  68 . 
         [0033]    A perforated disk  64  having perforations  63  closes one end of the cage as shown in  FIG. 7 . Disk  63  includes an annular wall portion  67  which spaces ball  65  from disk  64 . The diameter of ball  63  is smaller than the inside diameter of cylindrical portion  62  of cage  65  so that fluid can flow from right to left, looking at  FIG. 7 , around ball  65  and through apertures  63 . However, cage  65  will prevent fluid flow from left to right as in fracing operations by virtue of ball  66  resting on frustoconical portion  61  of the cage. 
         [0034]    As in previous embodiments, the sleeve  11 , cage member  62  and ball  66  may be made of a soluble, dissolvable or frangible material so that it would not be necessary to drill out the sealing mechanism after fracing. 
         [0035]    Another embodiment of the invention is illustrated in  FIG. 9 . This embodiment also utilizes a cylindrical tube  11  that has been expanded so to be secured within casing  21 . A solid frustoconical plug  71  after being pumped down into the well, rests against shoulder  53  of tube  11  at  72  as shown in  FIG. 9  to prevent flow downhole of the plug  71 . Plug  71  may also be made of a soluble, dissolvable or frangible material. 
         [0036]    The expandable sleeve may be formed of steel for example J-55 or similar steel. The wall thickness may vary from approximately 0.095 inches to about 0.25 inches. The diameter of the sleeve is selected to be slightly smaller than that of the production casing so for example if the casing is 5 ½ inch casing, the sleeve may have an outside diameter of 4.5 inches. 
         [0037]    A further embodiment of a tool suitable for use according to the invention is shown in  FIG. 10 . The tool  100  includes a hollow cone shaped sleeve  103  having an end portion having an outlet  119  formed therein. Sleeve  103  includes an internal converging passageway  110  leading to outlet  119 . The uphole end of the tool includes a plurality of radially spaced resilient collet style fingers  108  which each include a tab member  105  of a given width. The tabs  105  are sized to mate with an annular gap  107  formed between two sections of production casing  101 . The two sections  101  are secured together by a coupling  104 . Tool  100  may be run into the well with a disposable setting sleeve in conjunction with select fire perforating guns. As tabs  105  come into alignment with gap  107  having the same width as the tabs  105 , fingers  108  will expand outwardly in a known manner to lock the tool within the production casing. A ball or dart  106  can then be dropped into the production casing and will engage a converging wall section of sleeve  103  to thereby act as a frac plug. Ball or dart  106  may be made from a bio degradable material that dissolves. Sleeve  103  may be made from a degradable fiberglass resin or any other degradable material so that it does not need to be drilled out. This process can be repeated to form plural fracing zones. Each tool or plug  100  will have tabs  105  having a unique width so that the collet fingers will only be captured by a gap between the production casing members having the corresponding width. 
         [0038]    A cup shaped member  112  having seals  113  can be positioned on the uphole portion of ball or dart  106  to provide a seal. The internal surface of cup  112  is formed to conform to the spherical surface of ball or dart  106 . 
         [0039]      FIG. 11  illustrates yet a further embodiment of a tool according to an aspect of the invention. In this embodiment the tool includes an outer collet sleeve  127  that is deployed from inside a setting tool and is run in a wire string in the same manner that a frac plug would be run. Outer collet sleeve  127  includes a plurality of resilient collect fingers  131  having tabs  123  of a given width that mate with a gap  122  formed between adjacent production casing members  111  that are coupled together by a threaded coupler  121  for example. A valve seat  125  having a downhole end  129  is captured within collet sleeve  127  by virtue of complementary converging surfaces on the inside of the collet sleeve  127  and on the outer surface of valve seat  125 . Valve seat  125  includes a converging passageway  130  which may be initially filled by a bio-degradable material. Valve seat  125  may be separately carried down to engage collet sleeve  127 . Valve seat  125  carries an annular sealing ring  124  which is compressed outwardly against production casing  111  as valve sleeve  125  is forced, for example, by fluid pressure into collet sleeve  127 . 
         [0040]    After the collet sleeve and valve seat have been positioned within the production casing and the casing has been perforated, a ball or dart can be run in or dropped to engage valve seat  125  to form a plug. At this point, the perforated zone of formation uphole of the plug can now be treated. As in other embodiments the collet sleeve, valve seat and dart or ball can be made of bio-degradable or dissolvable material. 
         [0041]    Collet sleeve  127  and valve seat  125  may be run into the production casing separately or loosely attached to each other by an attachment mechanism, for example a shear pin, that can be disengaged by a suitable force applied to the valve seat such as fluid pressure. 
         [0042]    As in the embodiment of  FIG. 10 , each plug will have unique width tabs so as to be selectively placed within the production casing. The gaps between adjacent production casing members will have different widths to selectively capture the collet sleeves. Typically the first tool placed at the end of the production casing will have the widest tabs so as to pass over gaps of a smaller width as the tool is run into the production casing. 
         [0043]    The embodiments of  FIGS. 10 and 11  could be used in conjunction with a casing profile nipple (CPN). In lieu of having the tabs of the collet fingers being captured in a gap between production casing members, the tabs could be captured by an annular groove provided on the interior of a casing profile nipple which can be connected between adjacent production casing members as is known in the art. A suitable CPN is manufactured by Tesco Corporation. Additionally, a simple connector sub with an interior annular groove could be utilized as the securing mechanism for the embodiments of  FIGS. 10 and 11 . As shown in  FIG. 12 , the connector sub  200  has threaded end portions  201 ,  202  and a cylindrical tubular body portion  203 . An annular groove  204  is formed in the interior surface of body portion  203 . The groove is sized to accommodate tabs  105  or  123  on the end of the collet fingers  108  or  131 . 
         [0044]    Although the present invention has been described with respect to specific details, it is not intended that such details should be regarded as limitations on the scope of the invention, except to the extent that they are included in the accompanying claims.