Study On The Key Technologies Of Seismic Data Processing In Loess Tableland

People's demand for oil and coal is increasing day by day. And more effort were payed to explore and develop the material to meet their demand. In recent years, coal and coalbed gas are found richly in loess tableland area. In order to carry out coalbed gas reservoir prediction and full waveform inversion in Loess tableland area, it is necessary to process the seismic data of loess tableland area with high signal-to-noise ratio, high resolution and high fidelity.The surface of the loess tableland area is very complex. As a result, the first break of the seismic data collected in the loess tableland area is seriously distorted. What's worse, there are a lot of noise in the data and the noise is various, the energy difference is relatively large and the signal's primary frequency is quite low. Therefore, it is very difficult to improve the signal to noise ratio and the resolution of the data.In view of the geological condition and the seismic data of loess tableland,combined with the requirement of the "three high" seismic data processing,the multi domain noise suppression technology with high fidelity, amplitude consistency fine processing technology and high resolution processing technology were studied. The main steps are as follows,with the seismic data after field static correction,surface consistent amplitude compensation was done firstly which was useful for the separation of signal and noise, then suppressed the abnormal amplitude in the shot domain with the median frequency filtering, then turned to cross-spread approach, and suppressed the high energy in small offset with the combination of LIFT and median frequency filtering, lastly suppressed the linear interference by 3D-FKK. The principle of that process is to reduce the loss of the effective signal as far as possible. After suppressing noise, the old amplitude compensation was reversed and the new was computed and applied, then the 4D residual amplitude compensation was done. For the heterogeneity of lateral amplitude caused by the difference of signal to noise ratio in difference surface,the method was used that applying the amplitude compensation calculated from the effective signal to the whole data. During the process of improving resolution, robust surface consistent deconvolution was used to make the seismic wavelet consistent with the different surface environment, then the prediction deconvolution was used to compress the wavelet and made the wavelet in zero phase, and the spectral constraint deconvolution was used to broaden the frequency band.Based on the seismic data in the eastern part of Ordos Basin belonged to loess tableland, the techniques above were used. Although the complex and changeable process made the calculation and cost increased greatly, the signal-to-noise ratio and resolution of the data had been greatly improved and the degree had been relatively weakened that the lateral amplitude was influenced by the signal to noise ratio of different surface data. Basically it had reached the "three high" requirements.