Controlled-source electromagnetics (CSEM) can be used to image subsurface resistivity and add value in petroleum exploration. However, the application of CSEM methods can be particularly challenging in mature oil and gas fields, where the presence of steel casings and complex seabed infrastructure may influence electromagnetic (EM) fields. The effect of this metal infrastructure can be modeled using the method of moments (MoM), which has previously been demonstrated to be effective in simple situations. We have now developed a methodology for modeling the EM response of complex pipeline geometry using MoM, and we validate our approach numerically and experimentally; the difference between finite-element and MoM modeling is less than 3%, whereas the difference between experimental data and MoM results is less than 30%. We further develop a fast and efficient approach to model the EM response of horizontal pipeline infrastructure. First, we create individual pipe sections of custom shape; when assembled, these sections are used to construct the entire pipeline system. We then identify “precise” and “approximate” zones based on how accurately we need to perform the calculations. We find that the electric field values in the approximate zone can be calculated accurately and quickly using previously saved table values, and therefore achieve a considerable reduction in computational requirements. Finally, we apply our methodology to a real situation of a 60 km horizontal seabed pipeline and find that the electric field distortion can be calculated rapidly and efficiently with our custom-built algorithm.

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关于复杂管道基础设施的电磁响应

可控源电磁（CSEM）可用于成像地下电阻率并在石油勘探中增加价值。但是，在成熟的油气田中，CSEM方法的应用可能尤其具有挑战性，因为在这些油气田中，钢套管和复杂的海底基础设施的存在可能会影响电磁场。可以使用矩量法（MoM）对这种金属基础设施的影响进行建模，该方法先前已被证明在简单情况下有效。现在，我们已经开发了一种使用MoM对复杂管道几何结构的EM响应进行建模的方法，并且通过数值和实验验证了我们的方法。有限元和MoM建模之间的差异小于3％，而实验数据与MoM结果之间的差异小于30％。我们进一步开发了一种快速有效的方法来对水平管道基础设施的EM响应进行建模。首先，我们创建自定义形状的各个管段；组装时，这些部分用于构造整个管道系统。然后，我们根据执行计算所需的精确度来确定“精确”和“近似”区域。我们发现，使用先前保存的表值可以准确，快速地计算出近似区域中的电场值，从而大大减少了计算量。最后，我们将我们的方法应用于60 km水平海底管道的实际情况，发现可以使用定制算法快速有效地计算出电场畸变。