各向异性介质中的浅海海洋可控源电磁响应特征

由于受到空气波的影响,浅海海洋可控源电磁数据对海底储油层的反映较弱,如何对浅海数据进行处理和解释一直是海洋电磁理论研究的热点。随着近年来海洋电磁理论的不断完善,浅海数据已经可以被较好地处理与反演,但是其解释水平仍然受基本理论研究不足的制约。针对这一现状,本文开展了海底电各向异性对浅海数据影响规律的研究。具体方法为:利用欧拉旋转建立不同的海底电性各向异性模型,然后采用交错网格有限差分法计算浅海海洋可控源电磁响应,最后通过分析同线情况下电场Ex分量的振幅和相位曲线特征以及海底电场及电流密度分布规律,分析各向异性对浅海海洋可控源电磁响应影响的物理机制,并讨论浅海各向异性情况下海洋电磁对高阻储油层的识别能力。得出的结论为各向异性介质中的浅海海洋电磁响应特征与深海有较大区别,在进行数据的处理、反演和解释时应区别于深海情况。

MCSEM Responses for Anisotropic Media in Shallow Water

Due to the impact of air waves ,marine CSEM response to oil reservoir is weak in shallow water .Data processing and interpretation in shallow water have long been a hotspot in marine electromagnetic theoretical research .In recent years ,with the development of marine CSEM theory , EM data interpretation in shallow water has been improved .However ,it is still subject to restriction of fundamental theory .Under this situation ,we carry out the research on the effect of electrical anisotropy to MCSEM data in shallow water .We use Euler rotation to establish different anisotropic models for seabed media . Through using the staggered grid finite‐difference method to calculate marine CSEM responses in shallow water ,we analyze the characteristics of amplitude ,phase of inline Ex component , and current density .The physical mechanism of the anisotropic effect on the response of oil reservoir has also been analyzed .We conclude that the characteristics of marine CSEM responses in shallow water are different from that in deep water ,and attentions should be paid to the differences when interpreting and inversing the marine CSEM data in shallow water .This research can provide a guideline for marine CSEM data interpretation in shallow water and promote marine CSEM data interpretation in shallow w ater .