地震正演模拟技术在膏盐岩识别中的应用  

Applications of Seismic Forward Modeling Technology for Identifying of Gypsum-Salt Rocks

作　　者：李广才 王兴宇 李培[1,2] 张鹏辉 何梅兴[1,2] LI Guangcai;WANG Xingyu;LI Pei;ZHANG Penghui;HE Meixing(Institute of Geophysical and Geochemical Exploration,Chinese Academy of Geological Sciences,Langfang,Hebei 065000;National Center for Geological Exploration Technology,Langfang,Hebei 065000)

机构地区：[1]中国地质科学院地球物理地球化学勘查研究所,河北廊坊065000 [2]国家现代地质勘查工程技术研究中心,河北廊坊065000

出　　处：《中国煤炭地质》2023年第2期67-72,共6页Coal Geology of China

基　　金：中国地质调查局项目(DD20221638,DD20221639);中国地质科学院基本科研业务费项目(AS2020J03)。

摘　　要：膏盐岩层是一种良好的油气盖层,可作为探寻油气的一种先行有利条件,识别膏盐岩层对油气勘探具有积极的指导意义。目前地震波在膏盐岩层传播规律与波场特征有待进一步研究,尤其复杂构造膏盐岩对下伏地层的地震成像影响一直是勘探领域关注的热点问题之一。地震正演模拟可为揭示地震波在膏盐岩层传播规律、描述波场特征提供重要支撑。首先模拟研究了水平薄沉积膏盐岩层同地震子波分辨率问题,其次针对强变形的膏盐岩构造,设计了“眼球状”盐丘模型和复杂膏盐岩入侵白云岩的逆冲推覆地质模型,对地震地质模型进行了地震正演模拟和数据叠加、成像处理。结果表明:受限于地震子波频带,薄膏盐层厚达二分之一波长方可完全分辨;通过波动方程差分求解对复杂含膏盐地质体进行实际地震模拟,可动态显示地震波场向下延拓的细节特征;膏盐岩层引起的多次波、散射波及导波等干扰降低了下伏层反射波信噪比和连续性;利用覆盖次数较高观测系统可增强有效反射信号能量,识别一定厚度地下薄膏盐岩层;高速膏盐岩对下伏地层能量具有屏蔽作用,且使下伏地层产生明显“上拉”假象,模拟应用进一步深化了对含膏盐岩层地震波场的特征认识。As a good oil and gas caprock,gypsum-salt rock can be deemed as a connatural beneficial condition for oil and gas exploration,and thus the identification of gypsum-salt is of positive significance.At present,the propagation law and wave field characteristics of seismic waves in the gypsum-salt rocks need to be further studied,especially for the fact that the research on the impact of complex-structured gypsum-salt rocks on the seismic imaging of underlying strata has always been one of the hotspots in the exploration field.Seismic forward modeling supports a lot for revealing the law of seismic wave propagation and describing the characteristics of the wave field.First,the correlation of horizontally thin sedimentary gypsum-salt rocks and the seismic wavelet resolution is simulated and studied.Then,for the strongly deformed gypsum-salt rocks,the “eyeball-shaped” salt dome model and the actual complex thrust-nappe geological model of the salt dome invading dolomite are designed.After seismic forward modeling,data stacking and migration are carried out for the seismic-geological models.The results show that:limited by the resolution of seismic wavelet,the thin gypsum-salt layer can be wholly distinguished unless its thickness is no less than half of the wavelength;the actual seismic simulation of the complex gypsum-salt-bearing geological structure by the differential solution of the wave equation can dynamically show the downward propagation of the seismic wave field.Resulted from the gypsum-salt rock formations,the multiples,scattered waves,and guided waves,reduce the SNR and degrade the continuity of reflections from the underlying strata,and the survey with higher folds can enhance the effective signal,which can identify the underground thin gypsum-salt rock layers with certain thickness;the high-speed gypsum-salt rock has a shielding effect on the energy of the underlying strata,and makes the underlying strata produce the obvious illusion of “pulling up”.All the simulation tests further deepen the unde

关 键 词：正演模拟 膏盐岩 波场快照 分辨率 地震成像 

分 类 号：P618.11[天文地球—矿床学]