Seismic source apparatus

Abstract

The embodiments herein describe a seismic source that includes at least two firing heads connected to a shared reservoir of compressed gas. When underwater, a controller can instruct the firing heads to fire at the same time or at different times to create gas bubbles that generate seismic energy for identifying structures underneath a body of water. If the firing heads fire at the same, the resulting gas bubble may coalesce to form a single bubble, depending on the size of the respective bubbles and the separation distance between the firing heads. In one embodiment, the firing heads are attached at opposite ends of the shared reservoir (although this is not a requirement). The length of the reservoir, which dictates in part the separation distance of the firing heads, can be set so that gas bubbles generated by the firing heads at substantially the same time coalesce.

We claim: 
     
         1 . A seismic source comprising:
 a reservoir configured to hold compressed gas;   a first firing head coupled to the reservoir, the first firing head configured to generate seismic energy by releasing a first portion of the compressed air from the reservoir to form a first gas bubble in a seismic medium; and   a second firing head coupled to the reservoir, the second firing head configured to generate seismic energy by releasing a second portion of the compressed gas from the reservoir to form a second gas bubble in the seismic medium,   wherein the reservoir comprises a baffle dividing the reservoir into a first sub-chamber containing the first portion of the compressed gas and a second sub-chamber containing the second portion of the compressed gas.   
     
     
         2 . The seismic source of  claim 1 , wherein pressures in the first and second sub-chambers are maintained at a substantially equal pressure. 
     
     
         3 . The seismic source of  claim 2 , wherein the baffle comprises a pressure regulation feature for equalizing the pressures in the first and second sub-chambers. 
     
     
         4 . The seismic source of  claim 3 , wherein the pressure regulation feature defines an aperture that fluidly connects the first and second sub-chambers. 
     
     
         5 . The seismic source of  claim 3 , wherein the pressure regulation feature comprises a valve that fluidly connects the first and second sub-chambers. 
     
     
         6 . The seismic source of  claim 1 , wherein the reservoir comprises a cylindrical housing, wherein the first and second firing heads are disposed on opposite ends of the cylindrical housing. 
     
     
         7 . The seismic source of  claim 1 , wherein the first and second firing heads are separated by a distance of at least one meter. 
     
     
         8 . The seismic source of  claim 7 , wherein the distance separating the first and second firing heads is less than three meters. 
     
     
         9 . A seismic source comprising:
 a reservoir configured to hold compressed gas;   a first firing head coupled to the reservoir, the first firing head configured to generate seismic energy by releasing a first portion of the compressed gas from the reservoir to form a first gas bubble in a seismic medium; and   a second firing head coupled to the reservoir, the second firing head configured to generate seismic energy by releasing a second portion of the compressed gas from the reservoir to form a second gas bubble in the seismic medium,   wherein the first and second firing heads are separated by a distance of at least one meter.   
     
     
         10 . The seismic source of  claim 9 , wherein the distance separating the first and second firing heads is less than three meters. 
     
     
         11 . The seismic source of  claim 9 , wherein the reservoir comprises a cylindrical housing, wherein the first and second firing heads are coupled to opposite ends of the cylindrical housing. 
     
     
         12 . The seismic source of  claim 11 , wherein the reservoir comprises respective ports disposed at the opposite ends for receiving compressed gas to refill the reservoir. 
     
     
         13 . The seismic source of  claim 11 , wherein a length of the cylindrical housing is at least one meter. 
     
     
         14 . The seismic source of  claim 9 , wherein the reservoir comprises insulation mechanisms to mitigate heat transfer between the reservoir and the water in which the seismic source is submerged,
 wherein at least one sensor is mounted onto the reservoir for measuring an environmental condition.   
     
     
         15 . A method, comprising:
 generating seismic energy using a first firing head by releasing a first portion of compressed air stored in a reservoir to form a first gas bubble in a seismic medium; and   generating seismic energy using a second firing head by releasing a second portion of compressed air stored in the reservoir to form a second gas bubble in the seismic medium,   wherein the reservoir comprises a baffle dividing the reservoir into a first sub-chamber containing the first portion of the compressed gas and a second sub-chamber containing the second portion of the compressed gas.   
     
     
         16 . The method of  claim 15 , wherein pressures in the first and second sub-chambers are maintained at a substantially equal pressure. 
     
     
         17 . The method of  claim 15 , wherein the baffle comprises a pressure regulation feature for equalizing the pressures in the first and second sub-chambers. 
     
     
         18 . The method of  claim 15 , further comprising:
 towing a sensor system through the seismic medium, the sensor system comprising the first and second firing heads, the reservoir, a control plate, suspension means configured to connect the control plate to at least one of the first firing head, the second firing head, or the reservoir, and a cable bundle coupled at a first end to the control plate and at a second end to at least one of the first firing head, the second firing head, or the reservoir, wherein the cable bundle comprises an electrical wire and a high pressure hose for refilling the reservoir.   
     
     
         19 . The method of  claim 18 , wherein the sensor system further comprises:
 a second cable bundle coupled at a third end to the control plate and at a fourth end to at least one of the first firing head, the second firing head, or the reservoir, the second cable bundle comprising a second electrical wire and a second high pressure hose for refilling the reservoir, wherein the second high pressure hose is coupled to a first end of the reservoir and the high pressure hose is coupled to a second end of the reservoir that is opposite the first end.   
     
     
         20 . The method of  claim 15 , wherein the sensor system further comprises:
 a tow bridle coupled to the control plate and at least one of the first firing head, the second firing head, or the reservoir, wherein the tow bridle is configured to couple to an umbilical cord that tows the sensor system behind a tow vessel.