海洋可控源电磁法三维数值模拟

3D numeric simulation of marine controlled source electromagnetics (MCSEM).

本文利用美国Sandia国家实验室Weiss编写的3D有限差分程序,通过建立的正演模型,开展3D水平电偶源电磁场特征与异常体空间展布特征(几何特征、埋藏特征)关系的实例研究,并对模型进行了正演数值模拟,得到以下几点认识:①同一位置处接收到的电场强度随着异常体半径的增大而增大,高阻体的存在能够增大电场强度,且异常体越大,场强也越大;②归一化后的电场曲线特征表明,随着发射电流频率的降低,异常体引起的异常越来越小;随着异常体半径增大,引起的异常也逐渐增大;③当异常体半径不变而埋深改变时,随着埋深的增加电场强度逐渐减小,对异常体的分辨力越来越小。文中所得结果对MCSEM电磁场基本传播特性的认识和MCSEM观测资料的解释提供了依据。

The paper used the 3D finite-difference program written by Mr. Weiss in American Sandia State Lab to implement the case study on relationship between the feature of 3D horizontal electric-dipole source electromagnetics and spatial distribution of anomalous body (geometric feature and buried depth) and gained following knowledge by numeric forward simulation of models: the electric field strength received at same position increases along with increasing the radius of anomalous body, the existence of resistive bed can increase electric field strength, the larger the anomalous body, the stronger the field strength; the normalized curve of electric field showed that the anomaly resulted from anomalous body is smaller and smaller along with reducing the frequency of emission current, and the resulted anomaly becomes gradual increase along with increasing the radius of anomalous body; the resolution of anomalous body becomes poorer and poorer along with increasing buried depth and gradually reducing the electric field strength when radius of anomalous body unchanged and changing buried depth. The results concluded in the paper provided the basis of knowledge on basic propagating characteristics of MCSEM field and interpretation of MCSEM surveying data.