Experimental And Mechanism Research On Influence Of Clay Minerals On Rock Resistivity Dispersion

The complex resistivity method has been widely used in metal deposit exploration and hydrogeology,but has not been applied in well logging.In addition,there are no commercial tools yet.Because the mechanism of rock resistivity dispersion is not clear,the complex resistivity logging method is still studied in laboratory and numerical simulation.So it is necessary to carry out experimental and theoretical research on the dispersion of rock resistivity.In this paper,measurements of complex resistivity are performed on core plugs,obtained from artificial clear sand samples with different porosities and shaly sand samples with different clay types and contents,in a frequency range of 100 Hz to 15 MHz.The effects of porosity,saturation,salinity,temperature,ion type,clay mineral type and content on the dispersion properties of rock resistivity are studied.It is found that the resistivity and time constant of rock decrease with the increase of porosity,saturation,salinity,temperature and clay content and the dispersion degree of rocks also decrease.In addition,the sensitivity of each influencing factor to the rock resistivity dispersion curve is analyzed.The rock resistivity dispersion curve is more sensitive to saturation and porosity,followed by shale content.The impact of salinity and temperature on rock resistivity dispersion is smaller than the first three.The Cole-Cole model is used to fit the experimental data,and the model parameters are inversely simulated.It is found that the variation of rock time constant with all influent factors is similar with the rock resistivity.A model for evaluating the formation saturation with the time constant ? is built.The saturation calculated with the new model is very close to the real values.It is also found that the slope of real part of complex resistivity is related to the rock permeability.Based on the percolation theory,the dispersion characteristics of core resistivity are tried to be simulated.The simulation principle of rock resistivity dispersion is introduced.The effects of porosity,saturation,salinity,temperature and shale content on the dispersion of rock resistivity are simulated.The simulation results are consistent with the experimental results.