【摘要】 海洋可控源电磁法是钻前储层评价的有效手段,它可作为海洋地震重要辅助手段识别海底构造的储油/储水特征,从而减少盲钻率和勘探成本。然而,当使用水平电偶极作为发射源在浅水区测量时,沿空气-海水分界面传播的空气波会完全掩盖从高阻储油层返回的有用信号。由于空气波不含海底储油层的任何信息,空气波的存在严重影响海洋电磁的应用。因此,如何在浅水区观测数据中去除空气波影响以取得好的反演结果成为当前海洋电磁法的研究热点之一。首先基于Weidelt的空气波理论并采用对TE谱核直接求导的方法推导出空气波的主导项,然后根据空气波的物理成因及影响特征阐述了海洋电磁数据解释之前必须去除空气波的原因,最后将目前处理空气波问题的方法分成3类:1)根据空气波在频率域和时间域的特性去除或压制空气波,2)采用无空气波的测量方式,3)直接对含空气波的电磁数据进行反演解释。通过比较各种方法的效果,发现所有方法都有自己的应用条件和局限性。为有效地压制和去除空气波,各种方法的组合也许有更好的应用效果。更多还原

【Abstract】 Marine controlled-source electromagnetic method(MCSEM) is an effective technology for pre-drill reservoir appraisal.It is an important auxiliary technology for marine seismic to distinguish between oil-and water-bearing reservoir and consequently reduces the risk of dry wells and exploration cost.However,when surveying in shallow water using a horizontal electrical dipole(HED) as transmitting source,the airwave,propagating at the air-ocean interface,will almost totally mask the signal from the resistive reservoir.Due to the fact that the airwave doesn’t contain any information about the resistive layer,it seriously affects the MCSEM application in shallow water.Therefore,removal of the airwave from MCSEM data to get a good inversion result becomes a research focus.Based on Weidelt’s(2007) airwave theory,we first get the leading term of airwave by derivation of spectral kernels of TE mode.We then,discuss the reason for airwave removal before MCSEM inversion by elaborating the mechanism of its origin and effects.Finally,we divide the current technologies dealing with airwave problem into three categories: 1)Remove airwave based on its characteristics in frequency-domain and time-domain;2)Airwave-free survey;3)Direct interpretation.After analyzing these technologies,we find that all current technologies cannot completely remove the airwave effect in MCSEM data.Each method has its own conditions and limitations for application.A combination of these methods is more helpful and effective.更多还原