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 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 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 one 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 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, 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 variable 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 method for wiping an inner surface of a tubular member comprising:
   providing in the tubular member a plug having two conical wipers one of which overlaps the other in an axial direction, the wipers engaging the inner surface in a manner so that each wiper is deflected into a substantially cylindrical shape in engagement with the inner surface; and applying pressure from one end of the tubular member to move the plug within the tubular member; 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 wiper closest to the one end of the tubular member is overlapped by the other wiper.  
     
     
       54. The method of  claim 52  wherein as the wiper closest to the one end of the tubular member wears, the pressure will be applied to the other wiper.  
     
     
       55. The method of  claim 52  further comprising:
   providing an additional plug in the tubular member having two axially - spaced, conical wipers thereon, wherein each wiper on the additional plug engages the inner surface in a manner so that the wiper is deflected into a substantially cylindrical shape in engagement with the inner surface; and    
   applying pressure from one end of the tubular member to move the additional plug within the tubular member.    
 
     
     
       56. The method of  claim 52  wherein the wiper closest to the one end of the tubular member is overlapped by the other wiper on each plug.  
     
     
       57. A method for wiping an inner surface of a tubular member comprising:
   introducing a first plug into one end of the tubular member;        introducing a fluid into the one end of the tubular member to force the first plug downwardly in the tubular member to displace any fluid from the tubular member below the first plug;        providing at least two wipers on the first plug, one of the wipers overlapping the other wiper in an axial direction so that, as the plug passes downwardly in the tubular member, it wipes the inner surface of the tubular member of any accumulated fluid, wherein each wiper of the first plug is sized to engage the inner surface in a manner so that it is deflected into a substantially cylindrical wiping engagement with the inner surface;        terminating the step of introducing the fluid into the tubular member;        introducing a second plug into the tubular member end;        forcing the second plug downwardly through the tubular member so that it forces the fluid and the first plug downwardly in the tubular member;        establishing a differential pressure across the first plug to open the first plug and allow the fluid to pass through the first plug and exit the other end of the tubular member; and        providing at least two wipers on the second plug one of which overlaps the other in an axial direction, so that as the second plug passes downwardly in the tubular member, it wipes the inner surface of the tubular member of any accumulated fluid, wherein each wiper of the second plug is sized to engage the inner surface in a manner so that it is deflected into a substantially cylindrical wiping engagement with the inner surface.      
     
     
       58. The method of  claim 57  wherein the wiper of each plug closest to the one end of the tubular member is overlapped by the other wiper of the same plug.  
     
     
       59. The method of  claim 57  wherein the second plug is forced downwardly in the tubular member introducing a fluid into the tubular member.  
     
     
       60. The method of  claim 57  wherein the second plug forces the fluid from the tubular member into an annulus formed between the tubular member and the well.  
     
     
       61. The method of  claim 57  further comprising providing a float shoe in the tubular member which stops the downward movement of the first plug and causes the differential pressure.  
     
     
       62. A method for wiping an inner surface of a tubular member comprising:
   introducing a first plug into one end of the tubular member;        introducing a fluid into the one end of the tubular member to apply pressure to the first plug to force it downwardly in the tubular member to displace any fluid in the tubular member below the first plug;        providing at least two wipers on the first plug, one of the wipers overlapping the other in an axial direction so that, as the first plug passes downwardly in the tubular member, it wipes the inner surface of the tubular member of any accumulated fluid, and so that, as a wiper on the first plug closest to the one end of the tubular member wears, the pressure will be applied to the other wiper of the same plug;        terminating the step of introducing the fluid into the tubular member;        introducing a second plug into the tubular member end;        applying pressure to the second plug to force it downwardly through the tubular member so that it forces the fluid and the first plug downwardly in the tubular member;        establishing a differential pressure across the first plug to open the first plug and allow the fluid to pass through the first plug and exit the other end of the tubular member; and        providing at least two wipers on the second plug, one the wipers overlapping the other in an axial direction so that, as the second plug passes downwardly in the tubular member, it wipes the inner surface of the tubular member of any accumulated fluid, wherein as a wiper on the second plug closest to the one end of the tubular member wears, the pressure will be applied to the other wiper of the same plug.      
     
     
       63. The method of  claim 62  wherein the wiper of each plug closest to the one end of the tubular member is overlapped by the other wiper of the same plug.  
     
     
       64. The method of  claim 62  wherein the first and second plugs are identical.  
     
     
       65. The method of  claim 62  wherein the step of applying pressure to the second plug comprises introducing a fluid into the tubular member.  
     
     
       66. The method of  claim 62  wherein the second plug forces the fluid from the tubular member into an annulus formed between the tubular member and the well.  
     
     
       67. The method of  claim 62  further comprising providing a float shoe in the tubular member which stops the downward movement of the first plug and causes the differential pressure.  
     
     
       68. A method for wiping an inner surface of a tubular member comprising:
   providing in the tubular member a plug having two axially - spaced, conical wipers that engage the inner surface in a manner so that each wiper is deflected into a substantially cylindrical shape in engagement with the inner surface;        applying pressure from one end of the tubular member to move the plug within the tubular member;        providing an additional plug in the tubular member having two axially - spaced, conical wipers that engage the inner surface in a manner so that the wiper is deflected into a substantially cylindrical shape in engagement with the inner surface;        applying pressure from one end of the tubular member to move the additional plug within the tubular member; and        providing a shearable insert across a central opening in the plug closest to the end of the tubular member for closure thereof, the insert being adapted for shearing and opening the central opening in the latter 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 other plug for substantially permanent closure of the opening in the second plug.      
     
     
       69. A method for wiping a tubular member containing fluid comprising:
   introducing a first plug into one end of the tubular member;        introducing fluid into the one end of the tubular member to force the first plug downwardly in the tubular member to displace the fluid from the tubular member;        providing at least two axially spaced wipers on the first plug so that, as the plug passes downwardly in the tubular member, it wipes the inner surface of the tubular member of any accumulated fluid, wherein each wiper of the first plug is sized to engage the inner surface in a manner so that it is deflected into a substantially cylindrical wiping engagement with the inner surface;        terminating the step of introducing the fluid into the tubular member;        introducing a second plug into the tubular member end which is identical to the first plug;        forcing the second plug downwardly through the tubular member so that it forces the fluid and the first plug downwardly in the tubular member;        establishing a differential pressure across the first plug to open the first plug and allow the fluid to pass through the first plug and exit the other end of the tubular member; and        providing at least two axially spaced wipers on the second plug so that as the second plug passes downwardly in the tubular member, it wipes the inner surface of the tubular member of any accumulated fluid, wherein each wiper of the second plug is sized to engage the inner surface in a manner so that it is deflected into a substantially cylindrical wiping engagement with the inner surface.      
     
     
       70. A method for wiping a tubular member containing fluid in a well comprising:
   introducing a first plug into one end of the tubular member;        introducing fluid into the one end of the tubular member to force the first plug downwardly in the tubular member to displace the fluid from the tubular member; providing at least two axially spaced wipers on the first plug so that, as the plug passes downwardly in the tubular member, it wipes the inner surface of the tubular member of any accumulated fluid, wherein each wiper of the first plug is sized to engage the inner surface in a manner so that it is deflected into a substantially cylindrical wiping engagement with the inner surface;        terminating the step of introducing the fluid into the tubular member;        introducing a second plug into the tubular member end;        forcing the second plug downwardly through the tubular member so that it forces the fluid and the first plug downwardly in the tubular member;        establishing a differential pressure across the first plug to open the first plug and allow the fluid to pass through the first plug and exit the other end of the tubular member;        providing at least two axially spaced wipers on the second plug so that as the second plug passes downwardly in the tubular member, it wipes the inner surface of the tubular member of any accumulated fluid, wherein each wiper of the second plug is sized to engage the inner surface in a manner so that it is deflected into a substantially cylindrical wiping engagement with the inner surface; and        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.      
     
     
       71. A method for wiping a tubular member containing fluid comprising:
   introducing a first plug into one end of the tubular member;        introducing fluid into the one end of the tubular member to apply pressure to the first plug to force it downwardly in the tubular member to displace the fluid from the tubular member;        providing at least two axially spaced wipers on the first plug so that, as the first plug passes downwardly in the tubular member, it wipes the inner surface of the tubular member of any accumulated fluid, wherein as a wiper on the first plug closest to the one end of the tubular member wears, the pressure will be applied to the other wiper of the first plug;        terminating the step of introducing the fluid into the tubular member;        introducing a second plug into the tubular member end;        applying pressure to the second plug to force it downwardly through the tubular member so that it forces the fluid and the first plug downwardly in the tubular member;        establishing a differential pressure across the first plug to open the first plug and allow the fluid to pass through the first plug and exit the other end of the tubular member;        providing at least two axially spaced wipers on the second plug so that, as the second plug passes downwardly in the tubular member, it wipes the inner surface of the tubular member of any accumulated fluid, wherein as a wiper on the second plug closest to the one end of the tubular member wears, the pressure will be applied to the other wiper of the second plug; and        sizing each wiper to engage the inner surface in a manner so that it is deflected into a substantially cylindrical wiping engagement with the inner surface.      
     
     
       72. A method for wiping a tubular member containing fluid in a well comprising:
   introducing a first plug into one end of the tubular member;        introducing fluid into the one end of the tubular member to apply pressure to the first plug to force it downwardly in the tubular member to displace the fluid from the tubular member;        providing at least two axially spaced wipers on the first plug so that, as the first plug passes downwardly in the tubular member, it wipes the inner surface of the tubular member of any accumulated fluid, wherein as a wiper on the first plug closest to the one end of the tubular member wears, the pressure will be applied to the other wiper of the first plug;        terminating the step of introducing the fluid into the tubular member;        introducing a second plug into the tubular member end;        applying pressure to the second plug to force it downwardly through the tubular member so that it forces the fluid and the first plug downwardly in the tubular member;        establishing a differential pressure across the first plug to open the first plug and allow the fluid to pass through the first plug and exit the other end of the tubular member;        providing at least two axially spaced wipers on the second plug so that, as the second plug passes downwardly in the tubular member, it wipes the inner surface of the tubular member of any accumulated fluid, wherein as a wiper on the second plug closest to the one end of the tubular member wears, the pressure will be applied to the other wiper of the second plug; and        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.      
     
     
       73. A plug for wiping an inner surface of a tubular member, the plug comprising:
   a body member;        a lip extending outwardly from the body member and defining a wiping surface for wiping the inner surface of the tubular member; and        at least two axially spaced wiper cups having a conical outer surface extending outwardly around the body member and defining a wiping surface for wiping the inner surface of the tubular member, wherein the length of the wiping surface of each of the wiper cups is greater than the length of the wiping surface of the lip.      
     
     
       74. The plug of  claim 73  wherein the axial length of the wiping surface of each of the wiper cups is up to approximately five times greater than the axial wiping surface of the lip.  
     
     
       75. A plug for wiping an inner surface of a tubular member, the plug comprising:
   a body member;        a lip extending outwardly from the body member and defining a wiping surface for wiping the inner surface of the tubular member; and        at least two axially spaced wiper cups extending outwardly from the body member and defining a wiping surface for wiping the inner surface of the tubular member;        wherein the axial length of the wiping surface of each of the wiper cups is greater than the maximum radial width of the lip; and        wherein each of the wiper cups is deflected into a substantially cylindrical shape in engagement with the inner surface.      
     
     
       76. The plug according to  claim 75  wherein the body member has a central opening.  
     
     
       77. The plug of  claim 75  wherein each of the wiper cups extends radially outwardly from the body member at an acute angle with respect to the longitudinal axis of the body member.  
     
     
       78. The plug of  claim 75  further comprising a jacket disposed around the body member wherein the at least two axially spaced wiper cups are integrally formed with the jacket.  
     
     
       79. The plug of  claim 75  further comprising an insert disposed across a central opening in the body member 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.    
     
     
       80. The plug of  claim 75  wherein one of the at least two axially spaced wiper cups overlaps the other wiper cup in an axial direction so that the outer surfaces of the wiper portions together extend continuously along the longitudinal axis of the body member before the plug is inserted in the tubular member.  
     
     
       81. A method of wiping comprising:
   introducing fluid into a tubular member; and        moving a plug in the tubular member to move the fluid wherein the plug is constructed in accordance with    claim 75   .      
     
     
       82. A method of wiping fluid from a tubular member:
   introducing fluid into a tubular member;        providing a plug having a body member, a lip and at least two axially spaced wiper cups having a conical outer surface, wherein each wiper cup defines a wiping surface for wiping an inner surface of the tubular member, wherein:    ( a )  the length of the wiping surface of each of the wiper cups is greater than the length of the wiping surface of the lip, or      ( b )  the axial length of the wiping surface of each of the wiper cups is greater than the maximum radial width of the lip; and          moving the plug in the tubular member to wipe the fluid.