Resistivity response to the porosity and permeability of low rank coal

Laojunmiao coal samples from the eastern Junggar basin were studied to understand the relationship between coal resistivity and the physical parameters of coal reservoirs under high temperatures and pressures. Specifically, we analysed the relationship of coal resistivity to porosity and permeability via heating and pressurization experiments. The results indicated that coal resistivity decreases exponentially with increasing pressure. Increasing the temperature decreases the resistivity. The sensitivity of coal resistivity to the confining pressure is worse when the temperature is higher. The resistivity of dry coal samples was linearly related to ϕm. Increasing the temperature decreased the cementation exponent (m). Increasing the confining pressure exponentially decreases the porosity. Decreasing the pressure increases the resistivity and porosity for a constant temperature. Increasing the temperature yields a quadratic relationship between the resistivity and permeability for a constant confining pressure. Based on the Archie formula, we obtained the coupling relationship between coal resistivity and permeability for Laojunmiao coal samples at different temperatures and confining pressures.