Direct detection of hydrocarbons using seismic procedures

Methods for determination of amplitudes and spectra of seismic signals were combined to form a reliable and versatile interpretational system which allows an economical, semiautomatic extraction and a spatial presentation of various seismic parameters for lithological studies. An application of the system to an offshore survey area showed clear correlation between high amplitude anomalies and gas zones. Other indicators of hydrocarbons did not show much significant anomalies. Any quantitative interpretation of the results was impeded by complex layering of sandbeds which could not be resolved by seismic techniques. A method was developed which allows a reliable determination of frequency dependent attenuation if clear signals, undistorted by interference, are available and if comparatively high minimal attenuation is present.