Simulation And Application Of Forward Modeling And Inversion Of High-density Resistivity Survey

In recent years, high-density resistivity survey has been more and more widely used in the filed of engineering exploration. There are lots of previous examples in which this method has been used successfully. The two main researching methods of high-density resistivity survey are forward modeling and inversion. They are both of great importance in theory research, data processing and interpretation and so on.According to the existing research results in this field and the author's experience, in this article, the forward modeling and inversion are used in the study of theories which are relevant with high-density resistivity survey. Then the results achieved from the studying are used in the explorations in the filed, which shows the value of theories in guiding practice. The main contents of this article are as follows:First, this article begins with the electrical filed distribution rule of point current source which is in the uniform dielectric, and expounds the fundamental theory of direct current resistivity survey in details. It also gives a brief introduction of the anomalous bodies'effecting mechanism of the apparent resistivity and the fundamental theory of electrical profiling and drilling.Then, this article introduces the relevant theory of high-density resistivity survey following with the fundamental theory of conventional resistivity survey. It gives a brief overview of the surveying principle and common array types of high-density resistivity. The forward modeling and inversion techniques and the parameters of T ratios of high-density resistivity survey are also discussed in detail by the method of model test. On this basis, this article studied the relationship between anomaly magnitude and the resistivity difference on the one hand. As a result it generalizes a conclusion about what is necessary for the exploration in the field. On the other hand, it studies some factors about the common array types in the ideal condition of different geological and geoelectrical conditions, such as the depth of exploration, resolution and the factors which can impact them. As for the difficult of quantitative interpretation, this article introduces two ways to solve this problem, one is depth-correction based on the depth disclosed by borehole data. The other one is objective correlation method which is based on forward modeling. What is more ,it has verified the feasibility and effectiveness of the latter in the terms of quantitative interpretation through the model test.At last, the results of these studies are used in engineering examples in the following two respects. (1)the acquisition of data: they can be used to guide the selection of the acquisition parameters in order to improve the quality of data collection and exploration results;(2) data interpretation: As the presence of noise or the non-target abnormal may cause some interferences to apparent resistivity, and these interferences is difficult to identify or remove in data processing which can cause the unintelligibility and even concealment to the abnormal in the result of inversion. If the interpretation is made directly from the inversion results, there will be large deviations in the interpretation. Therefore, in the data processing and interpretation, other ways such as objective correlation method and the parameters of T ratios are used in addition to inversion, in order to distinguish the associated anomalies and find the anomalies which are not revealed in the inversion results. By comparison with the construction or borehole data, the interpretation results are identical with the truth.