论文详情
山前带浅表层结构复杂,建立准确的浅表层模型是山前带地球物理勘探关注的主要问题之一。在镇巴山前带开展了高密度二维地震调查、高密度电法、深井微测井等多种方法的浅表层调查和建模研究,结果表明,山前带浅表层结构是由相对连续的风化层、不连续的半风化层和基岩组成,等效于非均匀的连续模型,可以用连续、非均匀的速度模型来描述。初至波走时层析反演是应用较为成熟和广泛的获取近地表速度模型的技术,高密度二维地震与三维数值模拟资料应用表明,观测系统参数影响初至波走时层析反演精度的权重排序为道距、接收线距、炮点距、炮线距,其中,较小的道距是提高反演精度的关键。山前带高倾角地层出露区域采用道距≤10m、接收线距≤240m、炮点距≤20m、炮线距≤200m的观测系统,结合浅层结构约束的初至波走时层析能够提高近地表建模精度。
The near-surface structure of piedmont zones is complex and establishing accurate models of this zone is important for geophysical exploration.In this study,near-surface investigation and modeling were carried out in the Zhenba piedmont zone.A high density 2-D seismic survey and resistivity method,as well as a deep well micro-logging method were used.The study showed that the near-surface structure of the piedmont zone is composed of a relatively continuous weathering layer,a discontinuous semi-weathering layer,and bedrock.This near-surface structure is equivalent to a non-uniform continuous model and can,therefore,be characterized by a continuous,non-uniform velocity model.First-arrival traveltime tomography inversion of the high density 2-D seismic and 3-D numerical simulation data showed that the following factors (in order of importance) affect inversion accuracy:group interval,receiver line interval,shot point interval,shot line interval,and small group interval is essential.In a zone with exposure of high dip strata,an observation system was designed with group,receiver line,shot and shot line intervals of no more than 10m,240m,20m,and 200 m,respectively.First-arrival traveltime tomography with a near-structural constraint was then utilized to improve the accuracy of the near-surface modeling,with good results achieved in its practical application.
中国石油化工股份有限公司重大科技专项(PE19007-6)资助。