Abstract
Dolomite rocks constitute many important reservoirs due to the porosity-preserving and connectivity-enhancing effects of dolomitization. This study explores the correlation between resistivity and pore structure in dolomite rocks from the Mississippian Madison Formation in Wyoming and proposes a novel approach for predicting permeability from complex resistivity spectra (CRS).
Digital image analysis (DIA) on thin-sections is used to quantify the pore structure of 54 sucrosic dolomite samples. Pore-structure parameters derived from DIA are correlated to resistivity values of each plug and show that larger and simpler pore networks result in higher cementation factors.
Analyses of CRS are performed on brine-saturated core plugs in a log sweep from 0.1– 100,000 Hz with a four-electrode setup at varying confining pressures. Results show that the frequency dispersion of CRS between 10 and 100 kHz is directly related to the porosity in these dolomites. The phase shift of CRS shows high variance in both low and high porosity samples with characteristic slopes βPhase and βAmplitude for frequencies between 10 and 100 kHz. Modifying an empirical model of Tong & Tao (2008) to include porosity and both βPhase and βAmplitude can predict permeability with a correlation coefficient of R2 = 0.84.
•kHz-range complex resistivity spectra can be used to predict permeability.•Small and intricate pore networks facilitate electrical flow in dolomites.•Small pressure dependency of measurements suggests core data in dolomites is representative of reservoir conditions.
