Multiple Characteristics Analysis And Attenuation Of Acoustic Sub-bottom Profile

As one of the main types of noises on the acoustic sub-bottom profile, the multiple can usually have strong energy, widely exist, and even conceal the primary wave from view. Without being attenuated effectively, it may lead to wrong geological interpretations.At present, the single-trace layout with high frequency sampling is the main data acquisition approach in the sub-bottom profile detection. This may lead to poor result by using the conventional multiple attenuation techniques. Therefore, only the techniques which can be effective on the single-trace profile should be considered instead. However, since that an acoustic sub-bottom profile is usually acquired with a source-receiver offset, it should hardly be identical to a zero-offset seismic section, and these techniques may not directly be used on the non-zero offset profile.Based upon the detailed theoretical and experimental analyses of the horizontal and dipping sub-interface models suitable for two-dimension observation with non-zero offset, the following important guidable conclusions are deduced:①For a horizontal sub-interface, there is still a fixed ratio between the travel time of the nth order long-path multiple and n times of that of the primary wave, and the former is always smaller than the later;②For a dipping interface, there is no longer a fixed ratio for the travel time. Therefore, the ratio of the apparent dip between the long-path multiple and the primary wave in the time domain is also no longer fixed;③The time-distance difference between the long-path multiple of non-zero offset and that of zero offset becomes greater as the offset gets longer, but smaller as the detective depth gets deeper.On the basis of theoretical and experimental analysis, the MBP processing software is used for multiple tracing and adjustment, and attenuation on a sub-bottom profile with different frequency range. A multiple attenuation flow which may be suitable for the acoustic sub-bottom profile is integrated based upon quite a number of experiments. The result after multiple suppressing shows the good quality of the profiles with significantly improved event continuity of primary waves and highly enhanced signal to noise ratio.In addition, a full flow which may be suitable for the total processing of acoustic sub-bottom profile is also discussed. After multiple attenuating, a much higher quality profile can be obtained by using further processing such as migration and main energy spiking deconvolution.