Application analysis of electromagnetic wave propagation logging in formation dielectric constant measurement

Complex oil and gas reservoirs have complex electrical characteristics owing to the influence of formation water salinity. It is difficult to accurately evaluate and identify the fluid in such complex reservoirs by using the conventional resistivity method. However, the water salinity of the formation has a reduced effect on its dielectric constant, and the dielectric constant of water is far greater than that of oil and gas. Therefore, formation dielectric constant measured by electromagnetic wave propagation logging tool can be used to effectively distinguish oil and gas reservoirs and water layers. The accuracy of the formation response inversion charts of dielectric logging instruments is important for accurately evaluating fluids in complex reservoirs when these instruments are used. Based on the equivalent magnetic dipole model, this study deduces the calculation formula of 1 GHz electromagnetic wave propagation in layered media, proposes to integrate the geometric engineering parameters of the measuring probe into the finite element accurate simulation method, and establishes a 1∶1 finite element simulation model using COMSOL-multiphysics. Then, the influence of the probe geometric engineering parameters on the formation conversion chart is analyzed. Meanwhile, the experimental system is established to measure the accuracy of theoretical simulation. The results show the relative error between the dielectric constant obtained using the precise simulation and the real value is about 1%. The electromagnetic wave propagation logging tool is developed and it is applied to unconventional shale oil and gas logging in an oilfield, providing an effective measurement method for the evaluation of complex oil and gas reservoirs in oil fields.