Study Of Statics Correction Method Applied To CBM Seismic Data On The Loess Tableland

Statics correction is the critical technology in the processing of seismic data,which determines the results of seismic surveys.If statics correction is not done properly,the formation of image in the seismic section will be influenced a lot and it may even cause false cognition in the subsurface structure.In recent years,loess tableland is becoming a hot spot of seismic exploration,because unconventional oil and gas exploration is valued than before,especially coal-bed methane.The elevation,thickness and lateral velocity of weathering layer change drastically,resulting in serious statics correction problem in loess tableland.The changes of lithology and disordered first-break increase the difficulty of processing.Two-dimensional seismic data processing has difficulty in closing the survey line,especially for high-density two-dimensional seismic data.Therefore,in order to ensure the exploration and development of coal-bed methane,the urgent need to solve the problem of statics correction and line closure.This essay analyzes several statics correction methods and the various application of them.By combining the seismic data of the loess plateau,choosing refraction and tomography statics correction method and parameters to test.The concrete procedures are to get the correct first arrival information,to test offset and weathering speed using the proper parameter,to make a reasonable speed model which reflects the subsurface formation structure through restraining using short-refraction or microlog statics.By comparing and analyzing different statics correction methods,we find tomography statics correction can better solve the problem of this region.But due to the instability of two-dimensional velocity model,cause the closure error is bigger and serious influence in the interpretation work,this essay using pseudo-three dimensional multi-line tomography statics correction inversion technique.First,merge the velocity model of all the survey line to calculate the statics of closing velocity model.Then,decomposing the statics into high frequency and low frequency.Finally,output the low frequency and high frequency after closure all the low frequency.By this method,the statics correction and line closing problem are solved.At last,calculate the restraining high frequency correction using reflect residual statics correction method,basically solved the problem of static correction in the region.