基于弹性方程与声学方程的裂缝模型正演与偏移
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摘要
在Hudson理论的基础上推导出基于弹性—声学近似的裂缝模型反射系数计算公式,然后用变参考慢度Rytov近似波场延拓算子,对给定裂缝模型进行正演和偏移,并分析其波场特征,得到以下三点结论:1在当前地震分辨率下,不能识别单个裂缝,但可以探测裂缝发育带;2裂缝带达到一定的宽度和密度,可以用地震方法检测裂缝的分布,潜山内幕反射波的范围与强弱,有利于研究裂缝发育带的宽度和密度;3裂缝带的低频复波反射,表明在裂缝发育带,地震波频率减低,意味着用地震波的频率特征是可以检测裂缝。
From Hudson theory,this paper deduces the reflectance formula for the fracture model based on elastic-acoustic approximation. Then using variation reference slowness Rytov approximation wave-field extrapolation propagator, a forward modeling for a given fracture model is carried out and migrated. From the wave-field character analysis of the model,the following three conclusions are drawn : (1) Though it is impossible to detect a single fracture, one can detect a developed fracture area with current seismic resolution; (2) If the fracture region has fair width and density, its distribution and reflect wave's range and intensity inside buried hills can be detected by seismic method; (3) In fracture regions, some low frequency compound wave can be observed, which shows that seismic wave frequency is lowered in fracture region and thus fractures can be detected by their seismic frequency characters.
From Hudson theory,this paper deduces the reflectance formula for the fracture model based on elastic-acoustic approximation. Then using variation reference slowness Rytov approximation wave-field extrapolation propagator, a forward modeling for a given fracture model is carried out and migrated. From the wave-field character analysis of the model,the following three conclusions are drawn : (1) Though it is impossible to detect a single fracture, one can detect a developed fracture area with current seismic resolution; (2) If the fracture region has fair width and density, its distribution and reflect wave's range and intensity inside buried hills can be detected by seismic method; (3) In fracture regions, some low frequency compound wave can be observed, which shows that seismic wave frequency is lowered in fracture region and thus fractures can be detected by their seismic frequency characters.
引文
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[2] 何樵登,张中杰.横向各向同性介质中地震波及其数值模拟[M].吉林大学出版社,1996.
[3] KESSINGER,W.Extendedsplit-stepFouriermigration:62ndAnn.Internat.Mtg,Soc.Exp1.Geophys[C].,ExtendedAbstracts,917.
[4] HUANGLJ.FEHLERMCandWWRS.ExtendedlocalRytovFouriermigrationmethod[J].Geophisics,1999,64:1535.
[5] 陈生昌,曹景忠,马在田.基于Rytov近似的叠前深度偏移方法[J].石油地球物理勘探,2001,36(6):690.
[6] 贺振华,王才经,李建朝,等.反射地震资料偏移处理与反演方法[M].重庆,重庆大学出版社,1989.
[7] 贺振华,黄德济,胡光岷,等.复杂油气藏地震波场特征方法理论及应用[M].成都:四川科学技术出版社,1999.
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