Acquisition and Processing of Multi-source Technique Offshore with Different Types of Source

Abstract:

Multi-source blended offshore seismic acquisition has been developed in recent years. The technology aims to improve the efficiency of acquisition or enhance the image quality through the dense spatial sampling. Previous methods usually use several source of the same type, we propose applying onshore sources with different central frequencies to image multiscale target layers at different depths. Low frequency seismic source is used to image the deep structure but has low resolution at shallow depth, which can be compensated by high frequency. By combing the low and high frequency imaging together, we obtain high resolution profiles on both shallow and deep. Considering all of above, we implemented a 2-D cruise using 300Hz and 2000Hz central frequency spark source whcich are randomly shooted with certain delay time. In this process we separate blended data by denoising methods, including middle filter and curvelet transform, and then match prestack data to obtain final profiles. Median filter can restrain impulse noise and protect the edges while curvelet transform has multi-scale characteristics and powerful sparse expression ability. The iterative noise elimination can produce good results. Prestack matching filter is important when integrate wavelet of two different spark sources because of their different characteristics, making data accordant for reflecting time, amplitude, frequency and phase. By comparing with profiles used either single type of source, the image of blended acquisition shows higher resolution at shallow depth and results in more information in deep locations.