Universal cementing plug

Abstract

A cementing plug having a universal construction and improved wiping and extended wear characteristics. The cementing plug has a plug subassembly with a body member and an elastomeric jacket on the body member. The body member defines a central opening therethrough with a shoulder therein. To configure the plug as a bottom cementing plug, a shearable insert is positioned on the shoulder, and to configure the plug as a top cementing plug, a non-shearable insert is positioned on the shoulder. The shearable insert is one of a plurality of such inserts designed to shear at correspondingly different shear pressures. In a first embodiment, the shearable insert is a substantially flat disk having a uniform thickness, and in a second embodiment, the shearable insert has an outer ring portion and a relatively thin inner domed portion. Thus, a bottom plug may be pumped down a well casing with cement and a top plug thereabove so that when the bottom plug lands at the bottom of the casing, the shearable insert will shear at the predetermined pressure. The jacket has one or more wiper cups which have a conical surface extending at an acute angle with respect to a longitudinal axis of the plug, thereby providing a substantially large contact area in the well casing to improve wiping efficiency and extend life.

1. A cementing plug for use in cementing casing in a well, comprising:
 a body member defining a central opening therethrough;    an elastomeric jacket disposed around said body member and having a wiper cup extending therefrom for engaging an inner surface of the casing;    an insert disposed across said central opening in said body member for closure thereof, said insert being one of a plurality of interchangeable inserts; and    wherein said insert is a shearable member adapted for shearing and opening said central opening when a predetermined differential pressure is applied across said shearable member or a substantially non-shearable disk adapted for substantially permanent closure of said central opening.    
     
     
       2. The plug of  claim 1  wherein said shearable member is made of a rupturable material. 
     
     
       3. The plug of  claim 1  wherein said shearable member is a substantially flat disk having a substantially uniform thickness. 
     
     
       4. The plug of  claim 1  wherein said shearable member comprises:
 a ring portion; and    a domed portion extending from said ring portion.    
     
     
       5. The plug of  claim 1  wherein:
 said body member defines a shoulder in said central opening; and    said insert is disposed on said shoulder.    
     
     
       6. The plug of  claim 1  wherein said wiper cup is one of a plurality of such wiper cups. 
     
     
       7. The plug of  claim 1  wherein said wiper cup has an conical outer surface extending upwardly and outwardly at an acute angle with respect to a longitudinal axis of the plug. 
     
     
       8. A cementing plug for use in a cementing casing in a well, comprising:
 a body member defining a central opening therethrough and having a longitudinal axis;    an elastomeric jacket disposed around said body member and having a wiper cup extending therefrom, said wiper cup defining a conical outer surface extending upwardly and outwardly at an acute angle with respect to said longitudinal axis, wherein said outer surface is deflected into substantially cylindrical, wiping engagement with an inner surface of a casing when the plug is disposed therein;    an insert disposed in said central opening for at least temporary closure thereof, said insert being a selected one of a plurality of inserts; and    wherein said insert is a shearable member adapted for shearing and opening said central opening when a predetermined differential pressure is applied across said shearable member or a substantially non-shearable disk adapted for substantially permanent closure of said central opening.    
     
     
       9. The plug of  claim 8  wherein said wiper cup is one of a plurality of said wiper cups. 
     
     
       10. The plug of  claim 8  wherein said insert is positioned on a shoulder defined on said body member. 
     
     
       11. A cementing plug apparatus for use in cementing a length of well casing in a well, said apparatus comprising:
 a pair of substantially identical plug subassemblies, each of said plug subassemblies comprising: 
 a generally cylindrical body member defining a central opening longitudinally therethrough; and  
 an outer jacket disposed around said body member, said jacket having a resilient wiper cup extending therefrom adapted for wiping engagement with an inner surface of said length of casing;  
   a shearable insert positionable in one of said body members for temporarily closing said central opening in said one body member and for rupturing and thereby opening said central opening in response to a predetermined differential pressure thereacross; and    a substantially non-shearable insert positionable in the other of said body members for substantially permanently closing said central opening in the other body member.    
     
     
       12. The apparatus of  claim 11  wherein said jacket is made of an elastomeric material. 
     
     
       13. The apparatus of  claim 11  wherein said wiper cup is one of a plurality of wiper cups extending from said jacket. 
     
     
       14. The apparatus of  claim 11  wherein said wiper cup has an outer surface extending upwardly and outwardly at an acute angle with respect to a longitudinal axis of the corresponding body member. 
     
     
       15. The apparatus of  claim 11  wherein:
 said body member has a recess defined therein adjacent to said central opening;    said shearable insert is positioned in the recess of said one of said plugs; and    said non-shearable insert is positioned in the recess of the other of said plugs.    
     
     
       16. The apparatus of  claim 11  wherein said shearable insert comprises:
 a ring portion; and    a domed portion extending upwardly and outwardly from said outer ring portion.    
     
     
       17. The apparatus of  claim 11  wherein said shearable insert comprises a substantially flat disk of substantially uniform thickness. 
     
     
       18. The apparatus of  claim 11  wherein said non-shearable insert comprises a substantially flat disk of substantially uniform thickness. 
     
     
       19. A cementing plug apparatus for use in cementing casing in a well, said apparatus comprising:
 a first cementing plug comprising: 
 a first body member defining a first central opening therethrough;  
 a first jacket disposed on said first body member, said first jacket having a wiper cup extending therefrom adapted for wiping engagement with an inner surface of the casing; and  
 a replaceable first insert disposed adjacent to said first body member for temporarily closing said first central opening and subsequently shearing when subjected to a predetermined pressure, thereby opening said first central opening; and  
   a second cementing plug comprising: 
 a second body member defining a second central opening therethrough;  
 a second jacket disposed on said second body member, said second jacket having a wiper cup extending therefrom adapted for wiping engagement with an inner surface of the casing; and  
 a replaceable second insert disposed adjacent to said second body member for substantially permanently closing said second central opening.  
   
     
     
       20. The apparatus of  claim 19  wherein:
 said first and pond body members are substantially identical; and    said first and second jackets are substantially identical.    
     
     
       21. The apparatus of  claim 20  wherein said second insert comprises a substantially flat disk. 
     
     
       22. The apparatus of  claim 19  wherein said first and second inserts are interchangeable. 
     
     
       23. The apparatus of  claim 19  wherein said first insert is a selected one of a plurality of inserts shearable at a corresponding plurality of predetermined pressures. 
     
     
       24. The apparatus of  claim 23  wherein said first insert comprises a substantially flat disk. 
     
     
       25. The apparatus of  claim 23  wherein said first insert comprises:
 an outer ring portion; and    an inner domed portion integrally formed with said outer ring portion.    
     
     
       26. The apparatus of  claim 19  wherein said first and second jackets are made of an elastomeric material. 
     
     
       27. The apparatus of  claim 19  wherein:
 said wiper cup on said first jacket is made of a pair of wiper cups; and    said second wiper cup on said second jacket is one of a pair of wiper cups.    
     
     
       28. The apparatus of  claim 19  wherein said wiper cup on said first jacket and said wiper cup on said second jacket have a conical outer surface extending upwardly and outwardly at an acute angle with respect to a longitudinal axis of said first and second body members. 
     
     
       29. The apparatus of  claim 28  wherein said wiper cups are made of an elastomeric material. 
     
     
       30. The apparatus of  claim 19  wherein:
 said first body member defines a first shoulder therein;    said second body member defines a second shoulder therein;    said first disk is disposed on said first shoulder; and    said second disk is disposed on said second shoulder.    
     
     
       31. A plug for use in a well casing, comprising:
 a body member defining a central opening therethrough;    a jacket disposed around said body member and having a wiper cup extending therefrom for engaging an inner surface of the casing; and    an insert disposed in said central opening for at least temporary closure thereof, wherein said insert is a shearable member or a substantially non-shearable disk.    
     
     
       32. The plug of  claim 31  wherein said insert is one of a plurality of shearable and non-shearable inserts. 
     
     
       33. The plug of  claim 32  wherein said inserts are interchangeable. 
     
     
       34. The plug of  claim 31  wherein said insert is a substantially flat disk having a substantially uniform thickness. 
     
     
       35. The plug of  claim 31  wherein said shearable member is adapted for shearing and opening said central opening when a predetermined differential pressure is applied across said shearable member and said non-shearable disk is adapted for substantially permanent closure of said central opening. 
     
     
       36. The plug of  claim 31  wherein said shearable member is made of a rupturable material. 
     
     
       37. The plug of  claim 31  wherein said shearable member is one of a plurality of available thicknesses so that the shear pressure may be predetermined. 
     
     
       38. The plug of  claim 37  wherein said ring portion and said domed portion are integrally found. 
     
     
       39. The plug of  claim 31  wherein said shearable member comprises:
 a ring portion; and    a domed portion extending from said ring portion.    
     
     
       40. The plug of  claim 31  wherein said insert is positioned on a shoulder defined on said body member. 
     
     
       41. The plug of  claim 31  wherein said jacket is made of an elastomeric material. 
     
     
       42. The plug of  claim 31  wherein said wiper cup is one of a plurality of such wiper cups. 
     
     
       43. The plug of  claim 31  wherein said wiper cup has an conical outer surface extending upwardly and outwardly at an acute angle with respect to a longitudinal axis of the plug. 
     
     
       44. A plug for use in a well casing, comprising:
 a body member defining a central opening therethrough; and    an insert positioned for at least temporary closure of said central opening, wherein said insert comprises: 
 an outer ring portion; and  
 an inner portion extending from said outer ring portion, wherein said inner portion is thinner than said outer ring portion and has a viable thickness.  
   
     
     
       45. The plug of  claim 44  wherein said outer ring portion and said inner portion are integrally formed. 
     
     
       46. The plug of  claim 44  wherein said outer ring portion and said inner portion form an internal corner. 
     
     
       47. The plug of  claim 46  wherein said corner is radiused. 
     
     
       48. The plug of  claim 44  wherein said inner portion has a first thickness at a center thereof and a second thickness at an outer portion thereof adjacent to said outer ring portion. 
     
     
       49. The plug of  claim 48  wherein said inner portion is an outwardly convex domed portion. 
     
     
       50. The plug of  claim 49  wherein said domed portion has a height above said outer ring portion approximately equal to said first thickness. 
     
     
       51. The plug of  claim 48  wherein said first thickness is less than said second thickness. 
     
     
       52. A cementing plug comprising:
   a cylindrical body member having an opening extending longitudinally therethrough;        a jacket disposed around said body member having at least two wipers extending radially outward therefrom; and        a one - piece dome - shaped insert extending across the opening for temporarily closing the opening and adapted for being shearingly removed from the entire opening;        wherein the insert comprises an outer ring and an inner portion extending within the ring, wherein the inner portion has a variable thickness including a first thickness at the center thereof and a second thickness adjacent to an internal corner formed between the ring and the inner portion.      
     
     
       53. The cementing plug of  claim 52  wherein the insert shears in response to a predetermined fluid pressure applied to one surface thereof.  
     
     
       54. The cementing plug of  claim 53  wherein the cementing plug is adapted to be lowered into a well and the fluid pressure is created by introducing a fluid into the well.  
     
     
       55. The cementing plug of  claim 54  wherein a passage is formed through the body member through which the fluid flows when the insert shears.  
     
     
       56. The cementing plug of  claim 52  wherein the inner portion is thinner than the ring and is adapted to shear when subjected to the predetermined fluid pressure.  
     
     
       57. The cementing plug of  claim 52  wherein the inner portion has an outwardly convex, curvilinear configuration.  
     
     
       58. The cementing plug of  claim 52  wherein the height of the inner portion above the ring is approximately equal to the center thickness of the inner portion.  
     
     
       59. The cementing plug of  claim 52  wherein the first thickness is less than the second thickness.  
     
     
       60. The cementing plug of  claim 52  wherein the insert is fabricated from a material selected from the group consisting of rubber, plastic, and glass- filled plastic.    
     
     
       61. A cementing method comprising:
   lowering a body into a well;        providing an opening in the body;        disposing a one - piece dome - shaped member across the opening; and        subjecting the member to a fluid pressure sufficient to shear the member and open the opening.      
     
     
       62. The method of  claim 61  wherein the member shears in response to a predetermined fluid pressure applied against one surface of the member.  
     
     
       63. The method of  claim 61  wherein the step of subjecting comprises introducing a fluid into the well.  
     
     
       64. The method of  claim 63  wherein the opening is a passage through the body through which the fluid flows when the member shears.  
     
     
       65. The method of  claim 61  wherein the sheared member falls from the opening to open the entire opening.  
     
     
       66. The method of  claim 61  further comprising fabricating the member from a material selected from the group consisting of rubber, plastic, and glass- filled plastic.    
     
     
       67. A cementing method comprising:
   lowering a body into a well;        providing an opening in the body;        providing a one - piece dome - shaped member having a first thickness at the center thereof and a second thickness spaced from the center that is different from the first thickness;        disposing the member across the opening; and        subjecting the member to a fluid pressure sufficient to shear the member and open the opening.      
     
     
       68. The method of  claim 67  wherein the member shears in response to a predetermined fluid pressure applied against one surface of the member.  
     
     
       69. The method of  claim 67  wherein the step of subjecting comprises introducing a fluid into the well.  
     
     
       70. The method of  claim 67  wherein the opening is a passage through the body through which the fluid flows when the member shears.  
     
     
       71. The method of  claim 67  wherein the sheared member falls from the opening to open the entire opening.  
     
     
       72. The method of  claim 67  further comprising providing a ring around the member.  
     
     
       73. The method of  claim 72  wherein the member is thinner than the ring and is adapted to shear when subjected to a predetermined fluid pressure.  
     
     
       74. The method of  claim 73  further comprising fabricating the member from a material selected from the group consisting of rubber, plastic, and glass- filled plastic.