Dimpled marine seismic cables

Abstract

An apparatus and method for improving the efficiency of marine cable tow operations. Indentations such as dimples in the cable exterior surface reduce frictional drag forces and reduce strumming of the cables as the cables are towed through the water. The size, configuration and orientation of the indentations can be selected to control the desired water flow parameters.

What is claimed is:  
     
         1 . An apparatus for reducing friction acting against a marine cable towable through water, comprising: 
 a cable sheath having an exterior surface in contact with the water; and    a plurality of indentations in said sheath exterior surface for reducing friction between said cable and the water as the cable is towed through the water.    
     
     
         2 . An apparatus as recited in  claim 1 , wherein said indentations comprise dimples.  
     
     
         3 . An apparatus as recited in  claim 1 , wherein said indentations are symmetrically configured.  
     
     
         4 . An apparatus as recited in  claim 3 , wherein at least one of said indentations is configured in a round dish shape.  
     
     
         5 . An apparatus as recited in  claim 3 , wherein at least one of said indentations is configured in a polygonal shape.  
     
     
         6 . An apparatus as recited in  claim 3 , wherein at least two different shapes of indentations are formed in said sheath exterior surface.  
     
     
         7 . An apparatus as recited in  claim 1 , wherein said indentations are oriented in a particular pattern on said sheath exterior surface.  
     
     
         8 . An apparatus as recited in  claim 1 , wherein at least two of said indentations have different sizes.  
     
     
         9 . An apparatus as recited in  claim 1 , further comprising a plurality of protrusions extending from said sheath exterior surface.  
     
     
         10 . An apparatus as recited in  claim 1 , further comprising a splitter plate attached to said cable sheath.  
     
     
         11 . An apparatus for reducing strumming in a marine cable towable through water, comprising: 
 a cable sheath having an exterior surface in contact with the water; and    a plurality of indentations in said sheath exterior surface for reducing friction between said cable and the water as the cable is towed through the water.    
     
     
         12 . An apparatus as recited in  claim 11 , wherein said indentations are symmetrically configured.  
     
     
         13 . An apparatus as recited in  claim 11 , wherein at least two different shapes of indentations are formed in said sheath exterior surface.  
     
     
         14 . An apparatus as recited in  claim 11 , wherein said indentations are oriented in a particular pattern on said sheath exterior surface.  
     
     
         15 . An apparatus as recited in  claim 11 , further comprising marine seismic equipment attached to said cable.  
     
     
         16 . A method for towing a cable in water, comprising the steps of: 
 deploying a cable having a cable sheath in the water behind a tow vessel, wherein said cable sheath exterior surface in contact with the water has a plurality of indentations for reducing friction between said cable and the water; and    towing said cable through the water.    
     
     
         17 . A method as recited in  claim 16 , further comprising the step of deploying a cable in the water wherein said indentations comprise dimples.  
     
     
         18 . A method as recited in  claim 16 , further comprising the step of deploying a cable in the water wherein at least two of said indentations have different configurations.  
     
     
         19 . A method as recited in  claim 16 , further comprising the steps of deploying at least two cables in the water and of towing such cables at a selected separation distance between said cables.  
     
     
         20 . A method as recited in  claim 16 , further comprising the step of connecting marine seismic equipment to said cable before said cable is deployed in the water.