Application Of Automatic Search And Suppression To Multiple Attenuation In Shallow Profile Data

With the rapid development of economy and innovation of technology, more resources on the land are gradually consumed and depleted. However, abundant resources are buried under the ocean. Recently, some prospecting and exploitation on the sea are conducted to solve the shortage of resources. Seismic shallow profile prospecting is an important method for geological resource survey and exploration. Due to strong free surface between water and air, Seismic wave propagate to the free surface and are mostly reflected again, which is called multiple waves. For seismic reflection method, multiple waves are coherent interference waves. If multiple waves arise on seismic profile, the signal-to-noise ratio of seismic data is reduced, and the events are interpreted by mistake. An effective removal or suppression of multiple waves is a difficult work for seismic data processing. In this paper,an integrated suppression method and workflow of multiple waves are studied for improving resolution of the seismic shallow profile data.Due to limits of shallow profile data, common offset is small, and velocity information is difficultly obtained. Moreover,some information of multiple waves,such as arrival time,period, amplitude and phase,can’t be accurately calculated. The conventional suppression methods can not directly used. Based on predictive deconvolution algorithm, an automatic search and suppression method for removing multiple waves is studied,and a comprehensive processing workflow is given. The step size, which is used to solve Toeplitz equation and to get the filter coefficients, is automatically searched by using autocorrelation operation. A convolution is implemented between data and the filter coefficients,which is free from multiple waves. The preprocessing workflow for raw data is added to achieve better result.Firstly, the data is filtered and random noise is attenuated to improve the signal to noise ratio.Secondly, a suitable shaping filter operator is designed to conducts wavelet processing.Finally, the period of multiple waves is detected automatically by autocorrelation function for each trace data. Automatic search and suppression method is used to suppress multiple waves.Aiming at suppression of multiple wave in shallow profile data with small common offset and high frequency, some programs such as autocorrelation function, filtering, random noise suppression, wavelet processing and automatic search and suppression of multiples are developed. Multiple wave automatic search and suppression programs are tested by using model data and actual shallow profile data. The results verify the stability and reliability of these programs. And the processing profiles show the multiple waves are effectively suppressed.