Abstract
The complex resistivity of coal and related rocks contains abundant physical property information, which can be indirectly used to study the lithology and microstructure of these materials. These aspects are closely related to the fluids inside the considered coal rocks, such as gas, water and coalbed methane. In the present analysis, considering different lithological structures, and using the Cole-Cole model, a forward simulation method is used to study different physical parameters such as the zero-frequency resistivity, the polarizability, the relaxation time, and the frequency correlation coefficient. Moreover, using a least square technique, a complex resistivity “inversion” algorithm is written. The comparison of the initial model parameters and those obtained after inversion is used to verify the stability and accuracy of such approach. The method is finally applied to primary-structure coal considered as the experimental sample for complex resistivity measurements.
Highlights
The complex resistivity method is an emerging electrical exploration technology, which uses the induced polarization effect of the rock under the excitation of an external electric field to achieve the purpose of geophysical exploration [2]
The most important significance is that the complex resistivity parameters are closely related to the lithology and
Guo et al conducted testing and research on four types of structural coals with different metamorphic degrees, and the results showed that: with the increasing frequency, the complex resistivity modulus of different metamorphic coals showed a de-creasing trend, and the complex resistivity modulus at the low frequency stage showed obvious all directions
Summary
Coal resources are still the world main energy source. with the continuous increase in mining depth, the problem of geological disasters in production is becoming more and more serious. Many researchers have used complex resistivity to study the electrical characteristics of coal and rock, and analyzed the relationship between complex resistivity characteristics and parameters, gas content and coalbed methane content [10–12]. The research of Ke shizhen believes that the dispersion phenomenon of complex resistance is mainly caused by the polarization of the medium, and improved the Cole-Cole model to include multiple polarization points, and proposed a new interpretation method [15]. A forward modeling study of Cole-Cole is carried out to study the difference in induced polarization properties of coal and rock, which is reflected in the model parameters ρ0, m, τ, c and the real part and imaginary part calculated from them. The effect of joint inversion is better than that of individual inversion
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