Experimental Study on the Induced Polarization of Carbonate Rocks

The induced polarization (IP) parameters, such as the peak relaxation time and polarizability, have the potential to characterize pore structures of geomaterials and can be further used to distinguish lithology. However, the systematic experimental research on the IP response of carbonate rocks is scarce. To fill this gap of knowledge, we investigated the complex resistivity of 16 carbonate rocks, including dolostone and limestone, and discussed the applicability of existing induced polarization mechanisms for carbonate rocks. The relationship between IP parameters and pore structures were further analyzed by the experiment on variable confining pressure. The results indicate that the carbonate rocks with intergranular micropores or microfractures exhibit observable induced polarization response, where the amplitude and phase of complex resistivity are frequency-dependent, and still exist under high pressure conditions. Dolostone is characterized by low resistivity, high peak relaxation time, low polarizability, and the bell-shaped phase spectrum. Moreover, Stern layer polarization can explain the positive correlation relationship between peak relaxation time and pore size in samples with intercrystalline micropores. In contrast, membrane polarization provides a mechanism for the larger peak relaxation time in samples with microfractures, which is related to the low pore aspect ratio.