Resistivity And Acoustic Responses And Evaluation Model On Coal In South Of Shanxi

The relationship research of coal parameters and theacoustic and resistivity response can provide important rock physical foundation to analysis of reservoir characteristics using of geophysical data.This article based on the systematic analysis of the geological background and the characteristics of coal reservoir, for coal sample carrying on acoustic and resistivity physical simulation experiments in different coal petrography, quality, pore fracture structure, water saturation, coal body structure, temperature, pressure. And analysis the key coal parameters resistivity and acoustic response characteristics, and discusses the influence for the coal petrography resistivity and acoustic physical parameters, then build the mathematical model of the key reservoir parameters of resistivity and acoustic response.The results show that the acoustic and resistivity of coal samples in the study area are mainly affected by two factors: the internal factors(coal rank, coal petrography and coal quality, coal structure, water saturation); the external factors(temperature, pressure). The reflectivity of the vitrinite has a negative correlation with the resistivity, and has a positively correlated with the acoustic velocity. The content of the vitrinite has a positive correlation with resistivity and a negative correlation with the acoustic velocity. The resistivity and the acoustic velocity of coal presents growth with the increase of ash content. The resistivity of coal and acoustic velocity propagation all decreased by deepening the destruction of coal structure.Thedifferentitation of acoustic velocity and resistivity to the coal structure is significant. Relative tectonic coal, raw coal present higher resistivity and acoustic velocity. With the decrease of water saturation, the resistivityand the acoustic velocity are increased. The resistivity showed a linear decreasing trend with the increase of temperature, and the acoustic velocity present a kind of power function reduction with the increase of temperature. The resistivity presents an exponential reduction of the variation of the law with the increase of pressure, acoustic velocitypresents power function reduction with the increase of pressure. The main controlling factors of resistivity are ash content and content of the vitrinite and porosity.The main controlling factors of acoustic velocity are porosity and content of the vitrinite and water saturation.Established the coal structure identification model, and quantitative interpretation model of coal quality parameters, permeability, porosity and water saturation. Compared with the measured data, the model was calibrated and validated. The results show that the model has high reliability.