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 elastomerica jacket disposed around said body member and having a plurality of wiper cupcups extending therefrom, each said wiper cup having a conical outer surface extending upwardly and outwardly at an acute angle with respect to a longitudinal axis of the plug for engaging an inner surface of the casing; and  
 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 case 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 plurality of wiper cup  cups extending therefrom, each 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; and  
 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 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 plurality of resilient wiper cup  cups 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 each 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 inwardly 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 plurality of wiper cup  cups extending therefrom, each said wiper cup on said first jacket having a conical outer surface extending upwardly and outwardly at an acute angle with respect to a longitudinal axis of said first body member 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 first central opening therethrough;  
 a second jacket disposed on said second body member, said second jacket having a plurality of wiper cup  cups extending therefrom, each said wiper cup on said second jacket having a conical outer surface extending upwardly and outwardly at an acute angle with respect to a longitudinal axis of said second body member 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  second 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 plurality of wiper cup  cups on said first jacket is one of  comprises a pair of wiper cups; and  
 said second  plurality of wiper cup  cups on said second jacket is one of  comprises 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    19  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  insert is disposed on said first shoulder; and  
 said second disk  insert 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 plurality of wiper cup  cups extending therefrom each said wiper cup having a conical outer surface extending upwardly and outwardly at an acute angle with respect to a longitudinal axis of the plug 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 formed. 
     
     
       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  An apparatus, comprising:
 a cementing plug having:  a body member defining a central opening therethrough, the body member having a plurality of wipers that deflect into substantially cylindrical wiping engagement with the inner surface of a casing when the cementing plug is disposed therein; 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 an outwardly convex domed portion, is thinner than said outer ring portion and has a variable thickness.  
   
 
     
     
       45. The plug  apparatus of  claim 44  wherein said outer ring portion and said inner portion are integrally formed. 
     
     
       46. The plug  apparatus of  claim 44  wherein said outer ring portion and said inner portion form an internal corner. 
     
     
       47. The plug  apparatus of  claim 46  wherein said corner is radiused. 
     
     
       48. The plug  apparatus 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  apparatus of claim  49    48  wherein said domed portion has a height above said outer ring portion approximately equal to said first thickness. 
     
     
       51. The plug  apparatus of  claim 48  wherein said first thickness is less than said second thickness. 
     
     
       52. A method for wiping the inner surface of a casing comprising:
   providing a plug in the casing having at least two axially - spaced and overlapping wipers to engage and wipe the inner surface;        applying pressure from one end of the casing to move the plug within the casing; and        providing an insert across a central opening in the plug for closure thereof, wherein the insert is a shearable member adapted for shearing and opening the central opening when a predetermined pressure is applied across the shearable member or a substantially non - shearable member adapted for substantially permanent closure of the central opening.     
     
     
       53. The method of  claim 52  wherein the wipers are acutely angled with respect to a longitudinal axis of the plug. 
     
     
       54. The method of  claim 52  wherein the wiper closest to the one end of the casing is overlapped by the other wiper. 
     
     
       55. A method for wiping the inner surface of a casing comprising:
   providing a plug in the casing having at least two axially - spaced and overlapping wipers to engage and wipe the inner surface;        applying pressure from one end of the casing to move the plug within the casing;        providing an additional plug in the casing having at least two axially - spaced and overlapping wipers to engage and wipe the inner surface; and        applying pressure from one end of the casing to move the additional plug within the casing.     
     
     
       56. The method of  claim 55  wherein the plugs are identical. 
     
     
       57. The method of  claim 55  wherein the wipers on each plug are acutely angled with respect to a longitudinal axis of each plug. 
     
     
       58. The method of  claim 55  wherein the wiper closest to the one end of the casing is overlapped by the other wiper on each plug. 
     
     
       59. The method of  claim 55  further comprising providing a shearable insert across a central opening in one plug for closure thereof and adapted for shearing and opening the central opening when a predetermined pressure is applied across the shearable insert, and further comprising providing a substantially non- shearable insert disposed across a central opening in the other plug for substantially permanent closure of the latter opening.   
     
     
       60. A method for cementing a casing containing drilling mud in a well comprising:
   introducing a first plug into one end of the casing;        introducing cement into the one end of the casing to force the first plug downwardly in the casing to displace the mud from the casing;        providing at least two axially - spaced wipers on the first plug so that, as the plug passes downwardly in the casing, it wipes the inner surface of the casing of any accumulated mud;        terminating the step of introducing the cement into the casing;        introducing a second plug into the casing end;        forcing the second plug downwardly through the casing so that it forces the cement and the first plug downwardly in the casing;        establishing a differential pressure across the first plug to open the first plug and allow the cement to pass through the first plug and exit the other end of the casing; and        providing at least two axially spaced wipers on the second plug so that as the second plug passes downwardly in the casing, it wipes the inner surface of the casing of any accumulated cement; and        sizing each wiper so that the wiper of each plug closest to the one end of the casing is overlapped by the other wiper of the same plug.     
     
     
       61. The method of  claim 60  wherein the first and second plugs are identical. 
     
     
       62. The method of  claim 60  further comprising providing a shearable insert across a central opening in the first plug for closure thereof and adapted for shearing and opening the central opening in the first plug when a predetermined pressure is applied across the shearable insert, and further comprising providing a substantially non- shearable insert across a central opening in the second plug for substantially permanent closure of the opening in the second plug.   
     
     
       63. The method of  claim 60  wherein the second plug is forced downwardly in the casing by introducing a fluid into the casing. 
     
     
       64. The method of  claim 60  wherein the second plug forces the cement from the casing into an annulus formed between the casing and the well. 
     
     
       65. The method of  claim 60  further comprising providing a float shoe in the casing which stops the downward movement of the first plug and causes the differential pressure. 
     
     
       66. A cementing plug for use in cementing a casing in a well comprising:
   a plug having a longitudinal axis;        a first wiper extending radially outwardly from the plug at an acute angle with respect to the longitudinal axis of the plug;        a second wiper extending radially outwardly from the plug at an acute angle with respect to the longitudinal axis of the plug and disposed in an axially spaced relation to the first wiper;        wherein the second wiper overlaps the first wiper in an axial direction so that the outer surfaces of the wipers portions together extend continuously along the axial length of the body member before the plug is inserted in the casing; and        wherein the wipers deflect into substantially cylindrical, wiping engagement with an inner surface of the casing when the plug is inserted in the casing.     
     
     
       67. The plug of  claim 66  wherein the plug comprises a body member having an elastomeric jacket disposed therearound and wherein the first and second wipers are integrally formed with the jacket. 
     
     
       68. The plug of  claim 67  wherein the jacket comprises a cylindrical portion surrounding the body member and is integrally formed with the wipers. 
     
     
       69. The plug of  claim 67  wherein the body member is cylindrical and wherein the jacket has a through bore for receiving the body member. 
     
     
       70. The plug of  claim 66  further comprising an insert disposed across a central opening in the plug for closure thereof, wherein said insert is a shearable member adapted for shearing and opening the central opening when a predetermined pressure is applied across the shearable member or a substantially non- shearable member adapted for substantially permanent closure of the central opening.   
     
     
       71. A cementing plug for use in cementing casing in a well, comprising:
   a body member defining a central opening through the plug;        a plurality of wiper cups extending from the plug, each said wiper cup having a conical outer surface extending upwardly and outwardly at an acute angle with respect to a longitudinal axis of the plug 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.     
     
     
       72. The plug of  claim 71  wherein said shearable member is made of a rupturable material. 
     
     
       73. The plug of  claim 71  wherein said shearable member is a substantially flat disk having a substantially uniform thickness. 
     
     
       74. The plug of  claim 71  wherein said shearable member comprises:
   a ring portion; and        a domed portion extending from said ring portion.     
     
     
       75. The plug of  claim 71  wherein:
   said body member defines a shoulder in said central opening; and        said insert is disposed on said shoulder.     
     
     
       76. 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 plurality of wiper cups 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 comprising a ring portion and a domed portion extending from said ring portion or a substantially non - shearable disk.