Wiper plug seal integrity system and method

Abstract

An efficient wiper plug seal integrity system and method for deviated/horizontal wellbore is disclosed. The system/method includes a wellbore casing installed into a wellbore along with restriction elements, a secondary engagement sub, a float collar and a shoe. A wiper plug is deployed into the wellbore casing after cement slurry is pumped into the wellbore casing. The secondary engagement sub provides a tapered entry guide directly above the float collar. The entry guide has a reduced inside diameter that serves to enhance the sealing integrity of the wiper plug and also aligns the wiper plug to properly latch into a locked position. In another system, a stepped diameter wiper plug with a reduced nose is disclosed. The reduced nose provides for an improved seal integrity that fits and latches into a smaller internal diameter secondary engagement sub.

What is claimed is: 
     
         1 . An apparatus for sealing a casing with a wiper plug; said apparatus comprising
 (a) a hollow tubular shaped secondary engagement sub having a toe sub end and a heel sub end; and   (b) an inner diameter surface having an entry guide portion near the heel sub end;   wherein said wiper plug enters said heel sub end and engages he inner diameter surface;   wherein said wiper plug produces a fluid seal with the secondary engagement sub.   
     
     
         2 . The apparatus of  claim 1  wherein the inner diameter surface of said secondary engagement sub is configured to enable substantially unobstructed entry of said wiper plug into said secondary engagement sub. 
     
     
         3 . The apparatus of  claim 1  further comprises:
 (c) a float collar coupled to the toe sub end; and 
 (d) a wellbore casing coupled to the heel sub end of the secondary engagement sub. 
 
     
     
         4 . The apparatus of  claim 3  wherein said wellbore casing has an inner diameter and a ratio of said inner diameter of said secondary engagement sub to the inner diameter of said wellbore casing is less than 0.9. 
     
     
         5 . The apparatus of  claim 1  wherein an inner diameter of said toe sub end and an inner diameter of said heel sub end are equal. 
     
     
         6 . The apparatus of  claim 1  wherein an inner diameter of said toe sub end is smaller than an inner diameter of said heel sub end. 
     
     
         7 . A wiper plug seal integrity method, said method operating in conjunction with a wiper plug seal integrity system in a wellbore casing comprising a secondary engagement sub;
 said secondary engagement sub is a hollow tubular member that is positioned upstream of a float collar; said float collar is integrated at a toe end of said wellbore casing;   an inner diameter of said secondary engagement sub is configured to enable substantially unobstructed entry of said wiper plug; and   said secondary engagement sub is configured to latch said wiper plug thereon into a locked position when said wiper plug enters said secondary engagement sub;   wherein said method comprises the steps of:   (1) pumping cement into said wellbore casing;   (2) pumping said wiper plug at a pumping rate into said wellbore casing;   (3) pumping a fluid behind said wiper plug;   (4) slowing said pumping rate when said wiper plug approaches close to said secondary engagement sub;   (5) providing an entry guide portion for said wiper plug into said secondary engagement sub;   (6) centralizing and aligning said wiper plug in said secondary engagement sub; and   (7) locking and latching said wiper plug into said float collar.   
     
     
         8 . The method of  claim 7  wherein said inner diameter of said secondary engagement sub is configured to enable substantially unobstructed entry of said wiper plug into said secondary engagement sub. 
     
     
         9 . The method of  claim 7  wherein ratio of said inner diameter of said secondary engagement sub to an inner diameter of said wellbore casing is less than 0.9. 
     
     
         10 . The method of  claim 7  wherein said secondary engagement sub further comprises a toe sub end and a heel sub end; said toe sub end coupled to an end of said float collar; and said heel sub end coupled to said wellbore casing. 
     
     
         11 . The method of  claim 7  wherein an inner diameter of said toe sub end and an inner diameter of said heel sub end are equal. 
     
     
         12 . The method of  claim 7  wherein an inner diameter of said toe sub end is substantially smaller than an inner diameter of said heel sub end. 
     
     
         13 . A stepped wiper plug for use in a wellbore casing; said stepped wiper plug comprising
 (a) a hollow cylindrical shaped first section and   (b) a hollow cylindrical shaped second section attached to and extending from said first section;   wherein said first section has a diameter larger than a diameter of said second section; said first section configured to wipe an inner portion of said casing; said second section configured to wipe inner portions of downhole tools in said casing.   
     
     
         14 . The stepped wiper plug of  claim 13  wherein a ratio of said diameter of said first section to said diameter of said second section ranges from 0.4 to 0.9 
     
     
         15 . The stepped wiper plug of  claim 13  wherein said diameter of said second section is equal to a diameter of a secondary engagement sub. 
     
     
         16 . The stepped wiper plug of  claim 13  wherein said first section and said second section further comprises fins extending from an outer surface of said first section and said second section respectively. 
     
     
         17 . The stepped wiper plug of  claim 13  further comprises
 (c) a third section that is attached and extending from an end of said second section. 
 
     
     
         18 . The stepped wiper plug of  claim 17  wherein a diameter said third section is less than an inner diameter of said downhole tools. 
     
     
         19 . The stepped wiper plug of  claim 17  wherein a ratio of said diameter of said second section to said diameter of said third section ranges from 0.2 to 0.9 
     
     
         20 . The stepped wiper plug of  claim 13  wherein said downhole tools are selected from a group comprising: sliding sleeve valves, restrictions, or toe valves.