Dimpled riser floatation module

Abstract

An improved subsea riser for use in oil and gas drilling applications having a cylindrical floatation member adapted for attachment to a blow out preventer. The member may be configured with a plurality of generally evenly spaced dimples, indentations or protrusions about the circumference of the member to provide more streamlined water flow around the riser reducing turbulence and oscillations of the riser. The dimples, indentations or protrusions may be arranged in several ways including icosahedral, dodecahedral, octahedral and other polyhedral configurations.

1 . A riser comprising:
 a generally cylindrical member adapted for attachment to a blow out preventer from the drilling platform or rig to provide a conduit on a oil field installation; and   a plurality of generally evenly spaced dimples about the circumference of said member, wherein said dimples extend along a predetermined longitudinal dimension of said member.   
   
   
       2 . A riser as claimed in claim wherein said dimples are arranged in an icosahedral pattern based on a polyhedral with identical triangular faces. 
   
   
       3 . A riser as claimed in  claim 1  wherein said dimples are arranged in a dodecahedral pattern based on a polyhedral with identical pentagonal faces. 
   
   
       4 . A riser as claimed in  claim 1  wherein said dimples are arranged in a octahedral pattern based on a polyhedral with identical triangular faces. 
   
   
       5 . A riser as claimed in  claim 1  wherein said dimples are indented in a predetermined amount relative to the radius of the outer annulus of said member. 
   
   
       6 . A riser comprising:
 a generally cylindrical member adapted for attachment to a blow out preventer from the drilling platform or rig to provide a conduit on a oil field installation;   and a plurality of generally evenly spaced indentations about the circumference of said member, wherein said indentations extend along a predetermined longitudinal dimension of said member.   
   
   
       7 . A riser as claimed in  claim 6  further comprising dimples arranged in an symmetrical pattern on the surface of said indentation. 
   
   
       8 . A riser as claimed in  claim 6  further comprising:
 dimples arranged in an symmetrical pattern on the surface of said indentations;   said dimples arranged in an icosahedral pattern based on a polyhedral with identical triangular faces.   
   
   
       9 . A riser as claimed in  claim 6  further comprising:
 dimples arranged in an symmetrical pattern on the surface of said indentations;   said dimples arranged in an a dodecahedral pattern based on a polyhedral with identical pentagonal faces.   
   
   
       10 . A riser as claimed in  claim 6  further comprising:
 dimples arranged in an symmetrical pattern on the surface of said indentations;   said dimples arranged in an a octahedral pattern based on a polyhedral with identical triangular faces.   
   
   
       11 . A riser comprising:
 a generally cylindrical member adapted for attachment to a blow out preventer from the drilling platform or rig to provide a conduit on a oil field installation; and   a plurality of generally evenly spaced protrusions about the circumference of said member, wherein said protrusions extend along a predetermined longitudinal dimension of said member.   
   
   
       12 . A riser as claimed in  claim 11  further comprising:
 dimples arranged in an symmetrical pattern on the surface of said protrusions.   
   
   
       13 . A riser as claimed in  claim 11  further comprising:
 dimples arranged in an symmetrical pattern on the surface of said protrusions;   said dimples arranged in an icosahedral pattern based on a polyhedral with identical triangular faces.   
   
   
       14 . A riser as claimed in  claim 11  further comprising:
 dimples arranged in an symmetrical pattern on the surface of said protrusions;   said dimples arranged in an a dodecahedral pattern based on a polyhedral with identical pentagonal faces.   
   
   
       15 . A riser as claimed in  claim 11  further comprising:
 dimples arranged in an symmetrical pattern on the surface of said protrusions;   said dimples arranged in an a octahedral pattern based on a polyhedral with identical triangular faces.