Research On 3-D Multi-Parameter Borehole-ground Electrical Numerical Simulation And Contrast

In our country most oil fields are at the moment of oil extraction in high water cut stage in the middle and later periods of oilfield development, the situation with high level of drilling and low permeability reservoir brings up higher standard for research on drilling the remain oil. The borehole-ground electrical method which can solve the problem of the distribution of the remain oil has many virtues: low cost,easy operating,convenient application and so on. The operating stages of the borehole-ground resistivity method are as follows. Firstly the high current is applied to the case of the oil well, then the current flows to the layer from the perforated section of the well so that the non-uniform electric field form in the layer. Finally the resistivity distribution can be deduced through the measurement of the potential between the two points on the surface. But the shortcomings of the borehole-ground resistivity method which depends on the only parameter of resistivity for studying the remain oil distribution are the weak detecting ability of the depth and the weak anti-interference ability and so on. The induced polarization method which is sensitive for the interface between the oil and water can research better on the remaining oil of the reservoir and the frontier of water-flooding. There are some resemblances and differences between the time-domain induced polarization and the frequency-domain induced polarization. In this study, we research into numerical simulation methods of the borehole-ground resistivity method, the borehole-ground time-domain induced polarization method and the borehole-ground dual-frequency induced polarization method. By the numerical simulation methods, we get the influencing regularities from some parameters that influence on the apparent resistivity , the apparent chargeability and the apparent amplitude frequency ,the merits and faults and the application environment of the three methods by contrasting.Research into the numerical simulation theory of the borehole-ground resistivity method. Through the boundary conditions of the differential equation, form the liner equation in the 3-D mesh, solve the differential equation by the incomplete Cholesky decomposition conjugate gradient method (ICCG) method, the potential and the apparent resistivity can be get. We use the numerical simulation to construct different models. Through the contrast of different models, the influencing regularities from the distribution of the anomaly body that influence on the apparent resistivity can be get by calculating. The deeper the anomaly body is buried, the weaker the ability of detecting the anomaly body is by the borehole-ground resistivity method. Increasing the current can increase the surface potential in order to measure more potential data by the instrument with the fixed resolution.Research into the numerical simulation theory of the borehole-ground time-domain induced polarization method. Based on the numerical simulation of the borehole-ground resistivity method, according to the theory of the equivalent resistivity, the surface potential and the apparent chargeability can be get by calculating after the finite difference numerical simulation twice. Through the contrast among the different models, the influencing regularities from the distribution of the anomaly body that influence on the apparent chargeability can be get by calculating. The deeper the anomaly body is buried, the weaker the ability of detecting the anomaly body is by the borehole-ground time-domain induced polarization method. The higher the chargeability of the anomaly body is, the stronger the ability of detecting the anomaly body is.Research into the numerical simulation theory of the borehole-ground dual-frequency induced polarization method. According to the theory of cole-cole model, the complex resistivity can be computed by the expression of cole-cole model, the potential and apparent amplitude frequency by the dual-frequency induced polarization can be computed by the method the same as the numerical simulation of the borehole-ground resistivity. Through the contrast among the different models, the influencing regularities from the distribution of the anomaly body that influence on the apparent amplitude frequency can be get by calculating. The deeper the anomaly body is buried, the weaker the ability of detecting the anomaly body is by the borehole-ground dual-frequency induced polarization method. When other conditions are not changed and the anomaly body have the smaller chargeability or the larger time constant, the ability of detecting the anomaly body is stronger.Comparing among the three methods, the anomaly body with the different chargeability and the same resistivity as the earth can not be detected by the borehole-ground resistivity method. When the same anomaly body is buried deeper, the detecting ability by the borehole-ground time-domain induced polarization method is stronger than that by the borehole-ground resistivity; the apparent complex resistivity is the general reflection of the electrical conductivity and the polarization properties of the subjects underground. The apparent amplitude frequency is the reflection of the polarization properties of subjects underground, When the same anomaly body is buried deeper, the detecting ability by the borehole-ground dual-frequency induced polarization method is stronger than that by the borehole-ground resistivity; the borehole-ground dual-frequency induced polarization is equivalent on the principle to the borehole-ground time-domain induced polarization. But during the field work, the borehole-ground dual-frequency induced polarization method has some advantages such as powerful anti-jamming performance and restraining electromagnetic coupling, besides, When the same anomaly body is buried deeper, the detecting ability by the borehole-ground dual-frequency induced polarization method is stronger than that by the borehole-ground time-domain induce polarization.