Seismic sensor recording system

Abstract

A sensor system for deployment on or close to the seabed in marine seismic surveys includes a central hub, and a plurality of arms coupled to the central hub. Each arm has a degree of freedom of movement with respect to the central hub. The system further includes at least one seismic sensor mounted to each of said arms.

1 . A sensor system for deployment on or close to a seabed in marine seismic surveys, the sensor system comprising:
 a central hub configured to sit on or close to the seabed;   a mast projecting upwardly from the central hub; and   a plurality of seismic sensors attached to the mast at at least two vertically spaced locations.   
     
     
         2 . The sensor system according to  claim 1 , further comprising a first set of seismic sensors attached to said mast at a first, lower level, and a second set of seismic sensors attached to said mast at a second, upper level. 
     
     
         3 . The sensor system according to  claim 2 , each of the first and second sets of seismic sensors comprises a set of pressure sensors spaced angularly around the mast, each pressure sensor being at a radial offset position with respect to the mast. 
     
     
         4 . The sensor system according to  claim 2 , wherein at least one of the seismic sensors is attached to the mast at one or both of the first and second levels, substantially at a radially central location. 
     
     
         5 . The sensor system according to  claim 3 , wherein at least another one of the seismic sensors is attached to said mast at a position between said upper and lower levels. 
     
     
         6 . The sensor system according to  claim 2 , further comprising a first set of accelerometers at said upper level and a second set of accelerometers at said lower level, each set of accelerometers being located within a neutrally balanced housing coupled to said mast. 
     
     
         7 . The sensor system according  claim 1 , further comprising a data recorder, and a clock, located within the central hub, the data recorder being electrically coupled to each of the seismic sensors in order to receive seismic data therefrom. 
     
     
         8 . The sensor system according to  claim 1 , further comprising a data recorder, and a clock, the data recorder and clock being co-located with each seismic sensor. 
     
     
         9 . A sensor system for deployment on or close to the seabed in marine seismic surveys and comprising:
 a substantially rigid and planar frame; and   a plurality of seismic sensors mounted to the frame at respective peripheral locations.   
     
     
         10 . The sensor system according to  claim 9 , wherein said frame is substantially triangular or quadratic and one of the seismic sensors is mounted at or close to each of the points of the triangular or quadratic frame. 
     
     
         11 . The sensor system according to  claim 9 , wherein each seismic sensor is mounted to the frame by means of a substantially flexible coupling mechanism. 
     
     
         12 . The sensor system according to  claim 11 , wherein said coupling mechanism comprises one or more wires, ropes, or elastic bands. 
     
     
         13 . The sensor system according to  claim 9 , wherein at least one of the seismic sensors is mounted to the frame at a central location of the frame. 
     
     
         14 . A marine seismic survey system comprising:
 one or more ropes;   a rope deployment system for deploying the or each rope on or close to the seabed;   a multiplicity of sensor systems according to  claim 9 ; and   an attachment mechanism for attaching and detaching the sensor systems to the one or more ropes during deployment.   
     
     
         15 . An apparatus for collecting sensor nodes used in a marine seismic survey, where the nodes are configured to ascend towards the sea surface following use in a seismic survey, the apparatus comprising a funnel for deployment in the water and being configured to receive and capture ascending sensor nodes. 
     
     
         16 . The apparatus according to  claim 15 , further comprising:
 a detector for detecting location related signals emitted by sensor nodes; and   a transmitter for sending received location related signals to a vessel positioning system of a vessel on which the apparatus is located.   
     
     
         17 . The apparatus according to  claim 15 , further comprising a node deployment mechanism configured to deploy the nodes into the water through said funnel. 
     
     
         18 . A vessel comprising the apparatus of  claim 15 . 
     
     
         19 . A method of collecting sensor nodes used in a marine seismic survey, comprising:
 causing a sensor node to ascend through water towards the surface;   causing the sensor node to enter a collection system deployed on or close to the sea surface, via a funnel submerged in the water;   capturing the sensor node within the collection system; and   moving the captured sensor node to a storage location.   
     
     
         20 . The method according to  claim 19 , wherein said step of causing the sensor node to enter the collection system comprises:
 estimating a surface arrival location for the ascending sensor node; and   causing said funnel to move to approximately said surface arrival location.   
     
     
         21 . The method according to  claim 20 , wherein said collection system is located on or within a vessel, and said step of causing said funnel to move to approximately said surface arrival location comprises maneuvering the vessel to position the funnel approximately at said surface arrival location. 
     
     
         22 . The method according to  claim 20 , wherein said step of estimating the surface arrival location for the ascending sensor node comprises receiving a wireless signal, transmitted by the sensor node, and processing the wireless signal to estimate the surface arrival location. 
     
     
         23 . A method of deploying multicomponent sensor systems for use in a marine seismic survey, the method comprising:
 whilst advancing a vessel across a surface of water, laying onto the seabed from the vessel two or more closely spaced ropes, the two or more ropes being laid substantially parallel to one another, and each rope having coupled to it at spaced intervals a plurality of seismic sensors; and   configuring the deployed seismic sensors such that each cluster of adjacent sensors on the two or more ropes operates as a single multicomponent sensor system, giving rise to multiple single multicomponent sensor systems along the length of the deployed ropes.   
     
     
         24 . The method according to  claim 23 , wherein the ropes are spaced at a distance of 1 to 25 meters. 
     
     
         25 . The method according to  claim 23 , further comprising repeating the laying and configuring steps multiple times in order to deploy a corresponding multiple of lines of multicomponent sensor systems. 
     
     
         26 . The method according to  claim 23 , further comprising laying at least two closely spaced ropes, wherein each sensor is at least a  2 C or 4C sensor and each said single multicomponent sensor system is at least a 6C sensor.