Source signature processing in deep water, Gulf of Mexico: comparison between deterministic deconvolution and phase conjugation

Abstract

The Center for Marine Resources and Environmental Technology has been developing a new method to improve the resolution of high-resolution seismic profiling. To achieve this the source signature is recorded and the reflected data are sampled at a very high rate. In addition a certain amount of post processing is performed. During September 1999 a series of seismic profiles were acquired in the Gulf of Mexico using a 15 in³ watergun towed at the surface and a short single-channel hydrophone array towed about 250 m below the surface. The profiles were digitized at a rate of 80 000 samples per second; the length of each record was 4 s. Two different processes were applied to the data: deterministic deconvolution and phase conjugation. Both have the effect of compressing each reflected wavelet into a short pulse that is symmetrical about a central lobe. The ratio of compression obtained by applying deterministic deconvolution on the source signature pulse was about 300; it was about 160 when applying phase conjugation. This produced a resolution of about 6 cm by the deconvolution process and about 10 cm by using phase conjugation. The deconvolution process however is more subject to noise so the better result in this experiment was found to be provided by phase conjugation.