Seismic data acquisition of normally pressured shale gas reservoirs in residual synclines in the Pengshui area,Sichuan Basin,China

Normally pressured shale gas reservoirs in southern China,exhibiting significant potential resources,are primarily distributed in Silurian residual synclines at the periphery of the Sichuan Basin.Given intricate geological conditions in the study area,seismic data with high signal-to-noise ratios(SNRs) are required for fine-scale characterization of underground structural features and accurate description of the distribution patterns of high-quality shales.The purpose is to improve the probability of penetration of high-quality shales in horizontal wells and the drilling efficiency.Since 2011,the research and application of seismic data acquisition have been continually conducted in the Pengshui area.This study systematically summarized the methods,effects,and deficiencies of relevant projects implemented,and analyzed regional noise characteristics,the influence of channel spacing on static correction,and the degradation of the 3D seismic observation system.The results are shown as follows:(1)The 2D seismic data acquisition profiles displayed relatively clear reflection wave groups of shales in the Wufeng-Longmaxi formations,supporting the target selection and evaluation of normally pressured shale gas reservoirs;(2)The design principles of a 3D observation system,characterized by a wide azimuth,a low shot density,a high lateral fold number,and rich medium-near offset information, were proposed in this study;(3)The 3D seismic data processing profiles manifested high SNRs and clear wave group characteristics.The drilling results reveal accurate 3D structure imaging and a formation depth prediction error below 1%,strongly supporting shale gas exploration and production.The technical system in this study can be applied to similar exploration areas of normally pressured shale gas reservoirs.