Study on electrical characteristics and geophysical numerical simulation of high temperature coal and rock mass

Abstract

In order to guide the geophysical exploration technology of coal field fire area, judge the development stage of coal fire, accurately identify the boundary of hidden fire area, carry out targeted high-temperature electrical property research of coal and coal surrounding rock by analyzing the conductive mechanism of rock and the electrical property characteristics of coal rock mass in a narrow sense, by testing the resistance values of coal and rock mass at different temperatures, the change law of coal and rock resistivity with temperature and its influence mechanism are summarized; by means of numerical simulation method, the geoelectric model of the coal field fire area is established and the forward and reverse calculation of transient electromagnetic (TEM) is carried out. The results show that the resistivity of coal decreases with the increase of temperature, and the carbon content of coal is the dominant factor affecting its resistivity at high temperature stage; the resistivity of the surrounding rock of dry coal decreases with the increase of temperature, and the number of free moving carriers under the thermal dynamic condition is the dominant factor affecting its resistivity. Through numerical simulation, it is found that the transient electromagnetic abnormal response amplitude caused by high-temperature coal is much larger than that caused by high-temperature surrounding rock, the coupling effect of the transient electromagnetic central loop device on the high-temperature fire area is the best, and the shallower the burial depth of the fire area, the more obvious the electrical abnormal effects.

Keywords

• coalfield fire area
• high temperature coal and rock mass
• resistivity
• geophysical exploration
• numerical simulation
• transient electromagnetic(tem)
• forward inversion