Performing geophysical surveys using unmanned tow vessels

Abstract

Techniques are disclosed relating to towing source elements and geophysical sensors through a body of water using one or more unmanned tow vessel. In some embodiments, a plurality of unmanned tow vessels are configured to tow one or more signal sources and/or one or more streamers. The plurality of unmanned tow vessels may, in some embodiments, traverse various sail paths along a surface of a body of water in order to acquire geophysical data relating to formations disposed below the bottom of the body of water.

What is claimed is: 
     
         1 . A system, comprising:
 a plurality of unmanned tow vessels positioned in a crossline direction to form a survey spread, wherein the plurality of unmanned tow vessels are configured to traverse a sail path while towing one or more streamers and a set of source elements, including:
 a subset of high-frequency source elements towed at a first source density relative to a width of the survey spread; 
 a subset of mid-frequency source elements towed at a second source density relative to the width of the survey spread; and 
 a subset of low-frequency source elements towed at a third source density relative to the width of the survey spread, wherein the third source density is lower than at least one of the first source density or the second source density. 
   
     
     
         2 . The system of  claim 1 , wherein the second source density is lower than the first source density. 
     
     
         3 . The system of  claim 1 , wherein the third source density is lower than both the first source density and the second source density. 
     
     
         4 . The system of  claim 1 , further comprising:
 a survey vessel configured to tow one or more low-frequency signal sources.   
     
     
         5 . The system of  claim 1 , wherein each of the plurality of unmanned tow vessels is configured to tow at least one streamer. 
     
     
         6 . The system of  claim 1 , wherein a first unmanned tow vessel, of the plurality of unmanned tow vessels, is configured to tow at least one streamer and at least one of the set of source elements. 
     
     
         7 . The system of  claim 1 , wherein a distribution of the set of source elements is asymmetric relative to a centerline of the survey spread. 
     
     
         8 . The system of  claim 1 , wherein the plurality of unmanned tow vessels are further configured to adjust a lateral spacing between one or more of the plurality of unmanned tow vessels while traversing the sail path. 
     
     
         9 . The system of  claim 1 , further comprising:
 a different plurality of unmanned tow vessels distributed in a crossline direction to form a different survey spread, wherein the different plurality of unmanned tow vessels are configured to traverse the sail path at a particular distance in an inline direction behind the plurality of unmanned tow vessels while towing one or more streamers and one or more source elements.   
     
     
         10 . A system, comprising:
 a plurality of unmanned tow vessels distributed in a crossline direction to form a survey spread;   wherein the plurality of unmanned tow vessels are configured to traverse a sail path along a body of water while towing a plurality of streamers and a plurality of plurality of source elements that includes one or more low-frequency source elements and one or more high-frequency source elements, wherein a number of low-frequency source elements towed by the plurality of unmanned tow vessels is different than a number of high-frequency source elements towed by the plurality of unmanned tow vessels; and   wherein the plurality of unmanned tow vessels are further configured to actuate one or more of the plurality of source elements and collect data via one or more of the plurality of streamers while traversing the sail path.   
     
     
         11 . The system of  claim 10 , wherein a first unmanned tow vessel, of the plurality of unmanned tow vessels, is configured to tow only one or more source elements. 
     
     
         12 . The system of  claim 10 , wherein a first unmanned tow vessel, of the plurality of unmanned tow vessels, is configured to tow only one or more streamers. 
     
     
         13 . The system of  claim 10 , wherein a distribution of the plurality of source elements is asymmetric relative to a centerline of the survey spread. 
     
     
         14 . The system of  claim 10 , wherein a distribution of both the plurality of streamers and the plurality of source elements is asymmetric relative to a centerline of the survey spread. 
     
     
         15 . The system of  claim 10 , wherein a first lateral spacing between first and second unmanned tow vessels is greater than a second lateral spacing between a third and a fourth unmanned tow vessels. 
     
     
         16 . The system of  claim 10 , wherein the plurality of unmanned tow vessels are further configured to adjust a lateral spacing between one or more of the plurality of unmanned tow vessels while traversing the sail path. 
     
     
         17 . The system of  claim 10 , further comprising:
 a different plurality of unmanned tow vessels distributed in a crossline direction to form a different survey spread, wherein the different plurality of unmanned tow vessels are configured to traverse the sail path at a particular distance in an inline direction behind the plurality of unmanned tow vessels while towing one or more streamers and one or more source elements.   
     
     
         18 . The system of  claim 10 , further comprising:
 a different plurality of unmanned tow vessels distributed in a crossline direction to form a different survey spread, wherein the different plurality of unmanned tow vessels are configured to traverse a different sail path while towing one or more source elements, wherein the different sail path is positioned at a particular distance in a crossline direction relative to the survey spread.   
     
     
         19 . The system of  claim 10 , wherein a first unmanned tow vessel of the plurality of unmanned tow vessels includes a winch configured to control a position of one or more source elements. 
     
     
         20 . The system of  claim 10 , wherein a first unmanned tow vessel of the plurality of unmanned tow vessels includes a bay configured to receive at least one of the one or more source elements.