Fractal Characterization Of The Conductive Equivalent Path Of Micropores

During the later stages of oilfield development,the remaining oil is scattered in an unconventional manner within the reservoir,greatly influenced by the micro-heterogeneity of the rock layers.Exploring the mapping relationship between micro-scale controlling pore structure parameters and macroscopic electrical characterization is beneficial for precise evaluation of the remaining oil in the reservoir.Based on 25 typical samples from tightly cored wells in Daqing Oilfield,this thesis utilized nano-CT scanning experiments to obtain pore throat parameters and core slice images.The core slices were subjected to edge-preserving filtering,Otsu thresholding,and extraction of fractal dimensions.Analyzing the fluorescent microscopic scanning images of rock samples from the field’s tightly cored wells,the distribution of oil and water within the pores was analyzed.It was found that the emulsified state of oil and water and the multiple flushing of injected water had a significant impact on the resistivity.Based on data from high-porosity and high-permeability rock layers,as well as oil displacement efficiency and residual oil saturation from the same well under the same primary and development conditions,a strong correlation was observed between fractal dimensions and oil displacement efficiency,measured resistivity,and water saturation.The fractal dimension parameter comprehensively summarized the fluid migration and the properties of the rock layer’s flow channels,providing a better reflection of resistivity and the distribution of remaining oil.Furthermore,the Archie formula inversion further confirmed the influence of fractal dimensions on residual oil saturation and resistivity.From an experimental perspective,the conductivity theory of sandstone was studied,and dynamic displacement experiments of two-phase fluid resistivity were conducted to measure the salinity of mixed formation water and resistivity.After achieving oil saturation,a mixed liquid was used for displacement,and the curve depicting the relationship between saturation and resistivity change was obtained.It was observed that the variation and distribution of formation water during water flooding development were closely related.Finally,based on the theory of porous media flow,a micro-scale pore conductivity model based on fractal characterization was established,and the relationship between water saturation and formation resistivity was analyzed.A comparison between the water saturation calculated by the micro-scale pore conductivity fractal model and the water saturation measured from the core showed good agreement.Additionally,the resistivity response models for different equivalent models during water injection development were deduced to achieve innovation in theory and application on a larger scale,creating conditions for the low-cost,high-efficiency,and scientifically driven development of mature oilfields.