Patent Publication Number: US-10309188-B2

Title: Vee ramp slips with plug

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Patent Application No. 62/292,425 that was filed on Feb. 8, 2016. 
    
    
     BACKGROUND 
     In the course of producing oil and gas wells, typically after the well is drilled, the well may be completed. One way to complete a well is to divide the well into several zones and then treat each zone individually. Treating each section of the well individually may be accomplished in several ways. 
     One commonly used way of accessing the area to be treated is referred to as plug and perf. Generally, when plug and perf is used a perforating assembly is prepared on the surface. The perforating assembly typically consists of a plug on the lower end of the assembly, a setting tool just above the plug, and a perforating gun just above the setting tool. The assembly is then run into the wellbore to some point below the first zone that the operator desires to treat. The setting tool is then activated locking the plug into place and sealing the well below the plug against fluid flow from the surface or the well above the plug. The setting tool is then disconnected from the plug allowing the setting tool in the perforating gun to be moved to a point adjacent the first zone that the operator desires to treat. The perforating gun is then activated penetrating the casing to allow access to the first zone. The process is then repeated to allow access to each additional zone. 
     One of the difficulties with the plug and perf method is that the plug has very thick walls in order to support the compressive loads that are applied which allow the slips to dig into the casing wall when the slips are set. In order to immediately put the well on production after the well treatment, such as fracking, is complete operators tend to prefer plug that is a hollow throughbore that can be sealed with a ball during well treatment. The ball can then be removed by reverse flow or dissolution allowing the well to be put on production. Unfortunately, in order to meet the requirement that the plug must support the compressive loads as the slips are set, again the walls must be very thick in turn greatly reducing the diameter of the through bore through which fluid is produced. It is not uncommon for a conventional plug to have a through bore with less than half the diameter of the outer diameter of the plug. 
     SUMMARY 
     The current embodiment allows the use of a dissolvable, erodible, or composite material to be used as a plug or packer while maintaining a large bore through the internal diameter of the tool. The large internal diameter, even when using a relatively low strength material such as various polymers, dissolvable materials, erodible materials, composite material, or even soft metal such as aluminum is accomplished by distributing the load required to set the slips over a much larger area, while keeping the overall length of the plug or packer relatively short. In the event that harder and stronger material is used then the internal bore can be increased even further. For example, in a current embodiment of the plug the unset length of the packer is between 3 and 4 times the overall diameter of the packer where the thickness of a sidewall of the tool is about one fifth of the internal bore diameter. It may be understood that the actual dimensions of the tool and the various components may vary some amount while still keeping within the spirit of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  depicts a cutaway side view of a vee ramp packer. 
         FIG. 2  depicts the cross-section A from  FIG. 1  through the slips of the vee ramp packer. 
     
    
    
     DETAILED DESCRIPTION 
     As can be seen in  FIG. 1 , the plug  10  has castellations  12  at the top of the tool and castellations  14  at the bottom of the plug  10 . The castellations  12  are provided so that if another tool should sit down on top of the plug  10 , the castellations  12  may engage with a portion of the other tool in order to prevent the other tool from rotating thereby allowing the other tool to be milled out. Similarly, castellations  14 , at the lower end of the plug, are provided so that as a mill moves through the plug  10  once the mill moves through the slips  16  the remainder of the plug typically falls on top of the next lower tool or to the bottom of the well. The castellations  14  allow the remaining portion of plug  10  to engage with a portion of another tool or lower down plug in order to prevent the plug  10  from rotating during mill out. In certain versions of the plug  10  the castellations may have added elastomer  101  That does not stop a ball from moving past during pumping but the added elastomer  101  acts as a ball stop during reverse flow. The added elastomer  101  reduces the inner diameter of the plug  10  to an inner diameter less than that of a ball that may flow past the plug or has been previously introduced and is below the plug of interest. By having an inner diameter less than that of the ball that may be below the plug  10  during reverse flow the ball will move up and interact with the elastomer  101  and be prevented from flowing further upwards. However the castellations allow fluid to flow around the ball in between the openings and castellations such as opening  103  or around the tool and flow into the interior of the tool through port  105  thereby allowing the well to be produced even in the presence of an obturator or ball. 
     Starting from the top  13  of the mandrel  20  are the castellations  12 . Moving further down the mandrel  20  is recess  23 . At the upper end of recess  23  is ramp  21 . Recess  23  provides an initial location within the outer diameter of mandrel  20  for the sealing element  22  and backup ring  24 . The sealing element  22  is a swedgable cup type sealing element. In order to activate the sealing element  22  the plug  10  is axially compressed such that ramp  21  of the mandrel  20  and backup ring  24  moves towards one another thereby forcing the sealing element  22  radially outward on ramp  21  and into sealing engagement with the casing or wellbore wall within which the plug  10  is placed. With the sealing element  22  forced radially outward on ramp  21  a cup is formed facing the upper portion  13  of the plug  10  such that as downwards pressure from the surface is increased on the mandrel  20  of the plug  10  the sealing element  22  is forced into increasingly tighter engagement with the wellbore or casing. 
     As the plug  10  is axially compressed during setting the slip  30  engages with ramp  32  to move the slip  30  radially outward. Both the slip  30  and the ramp  32  have matching geometry in order to cooperate to spread the force of moving the slip  30  radially outward to engage with the casing over as large of an area of the mandrel  20  as is reasonably available. Generally, the ramp  32  is formed so that a first surface  52  is at some first angle  50  to the centerline of the plug  10  and surface  60  of slip  30  will be formed at a matching angle to that of first angle  50  of first surface  52 . Preferably first angle  50  is 15° however it is been found that a first angle  50  between 10° and 30° is sufficient. Additionally, first surface  52  has a second angle  160  that is offset by a predetermined amount from the perpendicular along first angle  50 . While the surface  60  of slip  30  will also have a second matching angle that matches the second angle  160  of first surface  50 . 
     The second matching angle can be more readily seen in  FIG. 2  which is a cross-section of the plug  10  across section line A-A. Perpendicular line  154  is shown extending from circumferential centerpoint  152  of plug  10  radially outward through the circumference of plug  10 . Perpendicular line  154  is perpendicular to the mandrel  20  at point  158 . The slip  30  has an edge  150  that extends along line  156 . Line  156  is set at an angle  160  to line  154 . The angle  160  is the second angle of the ramp  32  and the matching second angle of slip  30 . Preferably angle  160  is 15° however it is been found that an angle  160  between 10° and 30° is sufficient. An exemplary device would be a vee hull boat moving up an angled boat trailer ramp. Typically, the slip  30  will have a number of buttons  62  to engage the casing. In other instances, the slip  30  may have a number of serrations in order to engage the casing. 
     By using vee shaped slips and ramps the load required for the slip to engage the casing may be distributed across a larger surface area of the mandrel. As seen in  FIG. 1  by distributing the load across the surface of the mandrel  20  the mandrel thickness at the slips may be reduced. In the embodiment depicted the portion of the mandrel  20  where the ramp  32  is located has a thickness  80  denoted T 2  whereas the overall thickness  82  is denoted T 1 . T 2  is generally about ¼ of the thickness of T 1  although the ratio may be more or less depending upon materials and how the load of the set slip  30  is distributed across the mandrel  20  by varying both the first and second angles. The relatively small thickness  82  of the mandrel wall provides a through bore diameter  91  that is at least 70% of the overall diameter  92  of the mandrel  20 . In certain versions, such as where relatively weak materials, other than steel or cast iron, such as plastics, composites, and dissolvable materials are used, the through bore diameter may be reduced to as little as 40% of the overall diameter of the mandrel. 
     As the plug  10  is axially compressed the lock  90  and locking ring  106  move towards the top end  13  of mandrel  20 . As the lock  90  moves towards the top end  13  of the mandrel  20 , serrations  96  on the interior surface  94  of lock  90  engage with serrations  98  on the exterior surface of mandrel  20 . Upon the removal of the compressing force on plug  10  the lock  90  is prevented from moving towards the lower end  100  of plug  10  by the interaction between serrations  96  and serrations  98 . In the event that after slip  30  is set, forces are applied that would cause slip  30  to move towards the lower end  100  of the plug  10  then shoulder  102  of slip  30  presses against shoulder  104  of lock ring  106 . Lock ring  106  has angled surface  108  that interacts with angled surface  110  of lock  90  to force the serrations  96  deeper into the serrations  98  of mandrel  20  thereby preventing the lock  90  from moving towards the lower end  100  of the plug  10 . With the lock  90  prevented from moving towards the lower end of plug  10  the lock ring  106  is prevented from moving towards the lower end of plug  10  and the slip  30  is held in place engaged with the casing. 
     With the multi angles of the ramp/slip the thickness of the mandrel can be minimized and the materials may be varied because the force of the slip setting in casing is distributed over a large surface area of the mandrel instead of over the small circumferential area allowed by a typical cone set plug. 
     While the embodiments are described with reference to various implementations and exploitations, it will be understood that these embodiments are illustrative and that the scope of the inventive subject matter is not limited to them. Many variations, modifications, additions and improvements are possible. 
     Plural instances may be provided for components, operations or structures described herein as a single instance. In general, structures and functionality presented as separate components in the exemplary configurations may be implemented as a combined structure or component. Similarly, structures and functionality presented as a single component may be implemented as separate components. These and other variations, modifications, additions, and improvements may fall within the scope of the inventive subject matter.