Patent ID: 6236212
Filing Date: 2001-05-22
Classification: G01V

Abstract:
A system for use in making induced polarization measurements under the sea, said system comprising:a streamer cable having a proximal end towed from a ship in the sea, and a distal end positioned in sediments on the sea floor, said streamer cable including an active portion located at the distal end and comprising at least one transmitter for injecting a periodic electrical current into the sea floor, a plurality of receiver electrodes disposed along the towed cable in said sediments of the sea floor for receiving secondary signals produced by induced polarization of sources on or beneath the sea floor in response to said periodic electrical current, said plurality of receiver electrodes comprising at least first and second dipole groups of receiver electrodes for providing sampling at two different depths, said receiver electrodes comprising four electrodes arranged together in groups of three to form said first and second dipole groups and each of said dipole groups including an electrode shared with the other group and a central reference electrode between dipole electrodes and at least one pre-amplifier connected to each of said dipole groups for conditioning said secondary signals from the respective dipole group so as to combat noise and cross-talk effects in said secondary signals to thereby produce conditioned secondary signals; andon-board means, disposed on-board the ship, for supplying electrical current to said at least one transmitter and for receiving and processing said conditioned secondary signals from said at least one pre-amplifier.