Importance

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Abstract

Firing of a seismic source of the type called an air gun is detected by means of a fluid pressure sensor transducer in fluid communication with a shuttle-operating chamber of the air gun, and this sensor detects a surge in pressure in a portion of this chamber resulting from rapid motion of the shuttle, thereby producing an electrical signal which provides an accurate indication of the actual time of firing called the 'shot instant' of the air gun. The reaction time between the electrical firing command signal and the shot instant is not the same for all air guns in a seismic survey array but may differ from one to another due to variations in the solenoid-actuated valves which trigger the air gun, in tolerances of the air gun parts, frictional effects and slight differences in mass of moving parts, and wear of parts. The method and apparatus as disclosed enables a geophysical survey crew accurately to determine the reaction time of each individual air gun seismic energy source. Once their reaction times are determined, adjustments can be made in the firing command signals whereby the respective shot instant of air guns in an array can be synchronized, sequenced, or otherwise controlled in accord with any desired predetermined air gun array survey program. A convenient to install module is mounted in the electrical connections and pressurized gas supply line leading into the air gun, and a pressure transducer within this module senses the sudden changes occurring in the supply line as a result of surge in pressure in the shuttle-operating chamber produced by the rapid motion of the shuttle at the firing of the air gun.

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First Claim