Numerical Simulation Of Induction Log In Shale Gas Reservoir

Along with the deep development of oil and gas exploration, supply problems are gradually raised in the conventional oil and gas resources field, while shale gas and other unconventional oil and gas resources are becoming a hot topic of energy exploration. However, since shale is either a source rock or a reservoir, its geophysical logging reservoir evaluation differences in conventional reservoirs. The establishment of specialized petrophysical model on shale gas reservoirs, and the use of computer simulation technology to analyze the corresponding geophysical response characteristics is the effective way to break through the puzzle of unconventional oil and gas exploration. By using the numerical simulation of induction logging, the thesis made construction of geological and geophysical models which based on the actual shale gas reservoirs material to study the characteristics and laws of the resistivity parameter in the models.The thesis analyzed the basic characteristics of shale gas reservoirs, selected the electrical parameters of the reservoir as the study variables, elaborated their respective factors, and combined with the basic theory of induction logging measurements to introduce the theory of dual induction, array induction and to describe related induction logging instrument, then analyzed the applications of induction logging in shale gas reservoirs. For numerical simulation method on induction logging, this thesis used Partial Differential Equations in the Dirichlet condition of the electromagnetic induction theorem which based on Maxwell equations, utilizing the principle of Yee’s mesh generation, combined with the principle that the total field is decomposed into a primary field i.e. background field and a secondary field i.e. scattering field that calculated separately, then derived the function method to calculate the distribution of the primary field and the finite difference method in frequency domain to calculate the distribution of the secondary field. For discrete linear equations, the thesis applied the preprocessing course of incomplete Cholesky decomposition and bi-conjugate gradient iterative method to calculate the problems. In the theory of numerical simulation methods, the induction logging algorithm program code was written by using MATLAB programming platform.On the basic of the verified accuracy of the positive base algorithm program on uniform formation model, according to geological models of different geological conditions, the thesis established of radial and longitudinal model to study the induction logging response influenced by the mud filtrate in wellbore environment, caliper and invaded zone. The analysis shows that the calculated apparent resistivity is positive correlation with the resistivity of mud filtrate and invasion, while on the contrary it negatively correlated with the borehole diameter and the invasion radius was.The thesis is based on the actual field data of the shale of carbonate rocks in southern areas and the shale gas reservoirs in the region of Sichuan Basin, described the establishment of the reservoir resistivity model, especially built the model of the rock electrical properties in Longshan area. The studies have shown that forward problem of induction logging is better able to distinguish low-resistivity shale section, for the high resistance of shale due to the complexity of the composition of organic material, its identification needs the help of log responses in the surrounding formation.