论文详情
复杂结构膏盐岩对下伏碳酸盐岩地震成像的影响一直是地震勘探研究的热点之一。首先,分析了阿姆河右岸“三膏两盐”结构膏盐岩的地震反射特征:上盐层表现为一套弱振幅反射,同相轴平缓;中石膏层、下盐层、下石膏层的地震反射能量强,同相轴起伏变化强烈、连续性差。其次,针对强烈变形膏盐岩构造,设计了3个理论模型(“眼球状”盐丘模型、厚层盐层模型、两层薄盐层模型)和两个实际复杂膏盐岩模型。最后,应用非均匀介质声波方程交错网格高阶有限差分方法,对理论模型和实际模型进行了地震响应正演模拟和照明分析。结果表明:膏盐层引起的强能量多次波、广角导波、散射波和回转波等干扰波降低了下伏层反射波信噪比和连续性;复杂构造膏盐体形成的回转波一般会引起下伏层反射振幅的假亮点;膏盐层层数对下伏层能量的屏蔽作用比厚度更加显著;膏盐体的复杂构造导致了地震波向下传播能量的非均匀性和照明阴影。
The research on the impact of complex halo-anhydrite on seismic imaging of underlying carbonate is always one of the hotspots for seismic exploration .Firstly,we analyzed the seismic reflection characteristics of halo-anhydrites,which are featured by the structural combination of three layers of anhydrites and two layers of halites in Amu Darya right bank.The reflections from upper halites display a set of weak amplitude and gentle events;reflections from middle anhydrites,lower halites and lower anhydrites show strong energy and distortional events.Secondly,some models have been designed including three theoretical models (“eyeball-shaped” halite dome model,thick halite model and two-layer thin halite model) and two actual complex halo-anhydrite models.Finally,we performed seismic forward modeling and illumination analysis to the theoretical and actual models using the staggered-grid high-order finite difference method of acoustic equation in inhomogeneous media.The result indicates that:①the strong energy multiples,wide-angle guided waves,scattered waves and reverse waves generated by halo-anhydrites are interference waves,which reduce the SNR and continuity of reflections from underlying strata;②the reverse waves form halo-anhydrites with complex structure cause false bright spots of reflection amplitude from the underlying formation;③the number of halo-anhydrite layers has more remarkable shielding effect on the energy from underlying strata than their thickness;④the complex halo-anhydrite bodies leads to the heterogeneity of the downward seismic energy and forms illumination shadows.
国家科技重大专项“海外重点风险项目勘探综合配套技术”二期(2011ZX05029-003)项目资助。