Seismic sensor devices

Abstract

A sensor device is adapted to be installed at a land-air interface. The sensor device comprises a fluid-filled housing and a sensor arrangement supported within the housing and coupled directly to the fluid so as to detect movement thereof. A seismic sensor installation comprises a sensor device installed at a land-air boundary, wherein the sensor device comprises a fluid-filled housing and a sensor arrangement supported within the housing and coupled directly to the fluid as to detect movement thereof.

1 . A sensor device adapted to be installed at a land-air interface, the sensor device comprising:
 a fluid-filled housing;   a sensor arrangement comprising at least one hydrophone and/or at least one geophone disposed within the fluid filling the housing, wherein the sensor arrangement is surrounded by the fluid and configured to provide that the sensor arrangement is directly coupled to the fluid; and   a coupling device located at a lower part of the housing adapted to couple the sensor device to the land at the land-air interface, wherein the sensor arrangement is configured to measure compressional waves traveling from the land through the coupling device and through the fluid.   
     
     
         2 . A sensor device as claimed in  claim 1 , wherein the sensor device is adapted to be installed at a land-air interface by comprising a level oriented in common with a sensor of the sensor arrangement. 
     
     
         3 . A sensor device as claimed in  claim 1 , wherein the compressional waves comprise at least one of Rayleigh waves or P-waves. 
     
     
         4 . A sensor device as claimed in  claim 1 , wherein the sensor arrangement comprises a hydrophone and is absent of geophones and accelerometers. 
     
     
         5 . A sensor device as claimed in  claim 1 , wherein the sensor arrangement comprises three hydrophones arranged generally horizontally and in different orientations to one another. 
     
     
         6 . A sensor device as claimed in  claim 1 , wherein the sensor arrangement comprises a hydrophone and one or more geophones or accelerometers. 
     
     
         7 . A sensor device as claimed in  claim 1 , wherein the sensor arrangement is absent of a hydrophone and comprises two or more geophones or accelerometers. 
     
     
         8 . A sensor device as claimed in  claim 7 , wherein the sensor arrangement comprises two geophones or accelerometers arranged generally horizontally and in different orientations to one another. 
     
     
         9 . A sensor device as claimed in  claim 8 , wherein the sensor arrangement includes a vertically aligned geophone or accelerometer and a horizontally aligned geophone or accelerometer. 
     
     
         10 . A sensor device as claimed in  claim 9 , wherein the sensor arrangement includes two horizontally aligned geophones or accelerometers aligned orthogonally to one another. 
     
     
         11 . A sensor device as claimed in  claim 1 , comprising a mechanical decoupling arrangement for mechanically decoupling one or more sensors of the sensor arrangement from the housing and configured to provide that only motion of the fluid is sensed by the mechanically decoupled sensor. 
     
     
         12 . A sensor device as claimed in  claim 11 , wherein the mechanical decoupling arrangement comprises a spring and dashpot arrangement. 
     
     
         13 . A sensor device as claimed in  claim 1 , wherein the sensor device is partially buried in a land surface at the land-air boundary. 
     
     
         14 . A sensor device as claimed in  claim 1 , wherein the sensor device is disposed in a borehole. 
     
     
         15 . A method for sensing compressional waves at a land-air boundary, comprising:
 using a coupling device to couple a fluid-based sensor system to the land at the land-air boundary, wherein the fluid-based sensor system comprises a housing, a fluid disposed within the housing and one or more sensors disposed within the fluid and directly coupled to the fluid, and wherein the one or more sensors comprises one or more hydrophones and/or one or more geophones; and   using the one or more sensors to sense compressional waves within the fluid.   
     
     
         16 . The method of  claim 15 , wherein the one or more sensors are mechanically decoupled from the housing to isolate the sensors from the housing. 
     
     
         17 . The method of  claim 16 , wherein the compressional waves comprise at least one of Rayleigh waves or P-waves.