Key factors of marine shale conductivity in southern China—Part II: The influence of pore system and the development direction of shale gas saturation models

Abstract This is the second part of our study on the resistivity curve responses of marine shale gas reservoirs. The characteristics of the effects of low-porosity systems on electrical conductivity have been explored previously. However, the effects of the pore system and reservoir type should also be carefully considered. The features of the pore system that have the greatest impact on resistivity must be identified so that they can be considered in subsequent studies. This paper shows that the pore type has the most direct effect on the rock resistivity. The R2 of the relationships between the porosity of each pore type and resistivity can exceed 0.8. The pore types must be distinguished when considering the application of shale conductivity features. Among the reservoir classification methods considered, those based on reservoir quality characteristics and clustering have the best correspondence with the resistivity curve. In addition, this paper shows that the existing common saturation models are insufficient to evaluate the saturation of shale gas reservoirs. Subsequent research, including the derivation of conductivity models or the performance of shale resistivity experiments and simulations, should fully consider the characteristics of the mineral composition, organic matter and pore types of the rock. This series of analyses paves the way for research on shale gas electrical conduction mechanisms and saturation models, which are for the study of shale gas reservoir petrophysics. This study helps to address the lack of deep rock geophysical research on the large shale gas reserves that have been discovered.