Application Of Current Potential Method To Simulate Direct Current Electric Logging

The Direct Current (DC) electric logging is widely used in the exploration and development of oil and gas field. Study on DC electric logging data not only has theoretical value, but also has a widespread practical significance. This paper focuses on the study of two commonly used DC logging methods including spontaneous potential logging and array lateral logging, constructs mathematical and physical model according to the instrument model and work principle, and finite element method has been used to calculate its response in two-dimensional formation models. Current potential method can not only compute the response in formations, but also can depict the distribution map of the real current line in strata. Consequently, the detection performance of the instrument can be visually investigated, which provides the beneficial reference for the optimization design of the instrument structure. It is the advantage of current potential method compared to other numerical algorithms. On this basis, the paper analyzes the effects of different environmental factors on the response of the different two kinds of logging instruments and makes the related correction charts. This paper is divided into six chapters.The first chapter introduces the research background and significance of the DC electric logging. The status of research at home and abroad as well as the main works and contributions are discussed in this dissertation.The second chapter presents the method and principle of DC electric logging, which describes the basic principles of two kinds of conventional logging method including spontaneous potential logging and lateral logging comprehensively.The implementation rationale of the current potential method and the description method of current potential in the steady flow field are expounded in the third chapter. It presents the development process of the finite element method and the detailed steps of finite element method to solve the logging electric field response. What consisted are from the differential equation and discrete equations, to the basis functions and front solution for the large matrix equations.Chapter four provides the applications of current potential method in spontaneous potential logging, which states the mathematical and physical model of the spontaneous potential logging and simulates the mathematical and physical model for spontaneous potential logging in using the current potential method. The SP-3 correction charts of spontaneous potential has been drawn, and the influence of different environmental factors on the spontaneous potential logging response are investigated.Chapter five uses the current potential method to simulate the instrument response of the array lateral electrode system, it also takes on the numerical boundary conditions that the current potential needs to satisfy. Then it studies on the response characteristics of asymmetric array lateral electrode system structure. The detection characteristics of the instrument are investigated and the current line distribution of different working modes of the different formation models are given, moreover, the Groningen effect of the lateral logging is simulated and the current distribution characteristics are given.Finally, the summary and research prospects are introduced. The main achievements of this dissertation are as follows:The application of current potential method to simulate DC electric logging can provide important basis for electric field characteristic analysis and the parameters design and optimization of DC electric logging instrument and a useful reference for logging instrument design researchers. Moreover, it is of great significance to explanation for the oil and gas workers which provides accurate forward data.