Complex Resistivity Dispersion Characteristics of Water‐Bearing Coal Based on Double Cole‐Cole Model

Abstract

Reservoir fracture evaluation is an important research topic in the coalfield. In recent years, complex resistivity (CR) has been widely used in oil logging and achieved good results, such as permeability evaluation, water saturation (Sw) prediction, and aquifer identification. Therefore, the method has the potential to evaluate coal seam fracture. In the experiment, the real part R and imaginary part X of bituminous and anthracite coal with different Sw were measured by the impedance measuring instrument, then the Double Cole-Cole model was used to fit experimental data and analyze conductive mechanism. The main results are as follows: (1) the dispersion of CR parameters Reρ and Imρ is closely related to the metamorphism degree, frequency, and Sw; (2) induced polarization is the fundamental reason for the variation of coal samples’ complex resistivity parameters with frequency change; and (3) the Double Cole-Cole model agrees well with the experimental data, and the model parameters m1 and τ2 are strongly correlated with Sw. The parameters m1 and τ2 can be used to evaluate the Sw of fractures in coal seams and thus to evaluate the effect of hydraulic fracturing.

Study on the Complex Electrical Response Characteristics of Loaded Coal and the Control Mechanism of the Main Fracture System Structure

“…12,13 However, there is relatively little research on the electrical exploration of coalbed methane reservoir properties, and the basic theories are relatively weak. 14 Therefore, the applicability of electrical exploration technology for the physical properties of coal reservoirs urgently needs to be explored, especially for the strengthening of basic theoretical research of experiments. As a fundamental theoretical research method for electrical exploration in the laboratory, the complex resistivity method has been extensively studied in the field of oil and gas geology, focusing on the dispersion characteristics and mechanism of rock resistivity 15 and permeability evaluation.…”

“…Its detection and characterization are the primary prerequisites and key research content for coalbed methane exploration and development. − One of the main effective geophysical methods for detecting and describing the physical properties of coal reservoirs is the application of relevant electrical exploration methods in surface, well logging, well seismic joint, and coal mine underground . Many scholars have conducted extensive research on the basic theories and engineering practices related to electrical exploration of coal seams, but most of them have focused on the evaluation of coal seam water content/permeability under coal mining engineering conditions. , However, there is relatively little research on the electrical exploration of coalbed methane reservoir properties, and the basic theories are relatively weak . Therefore, the applicability of electrical exploration technology for the physical properties of coal reservoirs urgently needs to be explored, especially for the strengthening of basic theoretical research of experiments.…”