Dual-porosity saturation model of low-porosity and low-permeability clastic reservoirs

Abundant non-Archie phenomena have been discovered in rock electrical property experiments of low-porosity and low-permeability reservoirs, and the classical Archie model is not suitable for the oil saturation calculation in these reservoirs. Based on the pore structure characteristics of the reservoirs, a new dual-porosity saturation model considering the effect of pore structure is presented, namely, the total rock resistance is considered as the parallel resistance of free water resistance and micropore water resistance. Both the effects of macropores and micropores on rock electrical properties are considered in this model. The model is applied to core samples to derive the theoretical litho-electric relations which are in good consistence with the experiment measurement. The applications to low-porosity and low-permeability reservoirs of different regions in the east and middle of China, it is showed that the Archie model compared with the new model when the effects of rock lithology, physical property, pore structure and oiliness on electrical properties are considered. Therefore, calculated oil saturation of the new model is in good accordance with the real petrophysical characteristics of reservoirs, and it is much closer to the real oil-bearing conditions.