Extracting sv shear data from p-wave marine data

Abstract

A system and method of processing seismic data obtained using a plurality of towed single-component receivers in a marine environment is described, the towed single-component receivers configured to measure compressional P waves. The method comprises retrieving seismic data from a storage device, the seismic data comprising P-P data and shear mode data, wherein the P-P data and shear mode data were both received at the towed single-component receivers configured to measure compressional P waves to generate the seismic data. The method further comprises processing the seismic data to extract SV-P shear mode data and generating shear mode image data based on the extracted shear mode data.

1 . A method of processing seismic data, the seismic data obtained using a plurality of single-component towed receivers in a marine environment, the single-component towed receivers configured to measure compressional P waves, comprising:
 retrieving seismic data from a storage device, the seismic data comprising P-P data and shear mode data, wherein the P-P data and shear mode data were both received at the single-component towed receivers;   processing the seismic data to extract SV-P shear mode data; and   generating shear mode image data based on the extracted shear mode data.   
     
     
         2 . The method of  claim 1 , wherein the processing comprises extrapolating wavefields represented by the seismic data downward to computationally create virtual sources and virtual receivers on a seafloor in the vicinity of an area imaged by the seismic data. 
     
     
         3 . The method of  claim 2 , wherein the processing comprises determining SV-P velocities separately for positive-offset SV-P data and negative-offset SV-P data. 
     
     
         4 . The method of  claim 3 , wherein the processing comprises creating separate common conversion point stacks for the positive-offset SV-P data and the negative-offset SV-P data, wherein the processing comprises separately pre-stack migrating the SV-P data for positive-offset SV-P data and negative-offset SV-P data. 
     
     
         5 . The method of  claim 4 , wherein the processing comprises summing the common conversion point stacks for the positive-offset SV-P data and the negative-offset SV-P data, wherein the processing comprises post-stack migrating the SV-P data. 
     
     
         6 . The method of  claim 1 , wherein the P-P data and shear mode data were both received at the single-component towed receivers disposed well above the seafloor within the water column without the use of multi-component geophones, the single-component towed receivers configured to receive compressional P waves and not shear waves. 
     
     
         7 . The method of  claim 1 , wherein the SV-P data is a result of down going P waves from towed P wave sources which upon contact with the seafloor generate downgoing SV shear waves directly at the point of contact of the P waves with the seafloor at the seafloor surface. 
     
     
         8 . The method of  claim 1 , further comprising:
 transmitting P waves from P wave sources, wherein the P waves upon contact with the seafloor generate downgoing SV shear waves directly at the point of contact of the P waves with the seafloor at the seafloor surface, the downgoing SV shear waves reflecting off sub-seafloor interfaces as SV-P wave modes;   receiving the SV-P wave modes using the single-component towed receivers; and   storing the SV-P wave modes in the data storage device to achieve the seismic data comprising P-P data and shear mode data.   
     
     
         9 . A method of generating a shear mode image from marine P-wave seismic data acquired with a plurality of towed single-component P-wave sensors, comprising:
 retrieving from a storage device seismic data generated by a source and received by the towed single-component P-wave sensors, the data comprising SV-P mode data;   extrapolating wavefields represented by the seismic data downward to computationally create virtual sources and virtual receivers on a seafloor in the vicinity of an area imaged by the seismic data; and   processing the extrapolated wavefields to generate shear mode image data.   
     
     
         10 . The method of  claim 9 , wherein the SV-P mode data is a result of a downgoing P wave from a towed P wave source which upon contact with the seafloor generates downgoing SV shear wave modes directly at the point of contact of the P wave with the seafloor at the seafloor surface. 
     
     
         11 . The method of  claim 10 , wherein the seismic data was received at the towed P-wave sensors as they were being towed, the sensors disposed well above the seafloor within the water column without the use of multi-component geophones. 
     
     
         12 . The method of  claim 9 , further comprising:
 providing a memory programmed to store processed seismic data, the stored, processed seismic data having been processed from direct shear wave mode data, the direct shear wave mode data representing seismic waves which were provided as shear waves directly at a point of application of a vertical force source and sensed as reflections at one or more geophones; and   transferring the stored, processed seismic data to a memory device using a processing circuit.   
     
     
         13 . The method of  claim 12 , further comprising transferring the stored, processed seismic data over a wired or wireless network to another computing device over a network interface circuit, using a processing circuit. 
     
     
         14 . The method of  claim 12 , wherein the memory device comprises at least one of a hard drive, a tape drive, a disk drive, optical disk storage, magnetic disk storage or flash memory.