|Texas A&M University
|Complex Pore and Grain Structures; Electrical Resistivity; Dielectric Permittivity
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Complex rock composition and pore geometry, as well as anisotropic behavior and heterogeneity, can significantly affect formation electrical resistivity and dielectric permittivity, which are used to estimate in situ petrophysical properties, such as water/hydrocarbon saturation. The main research topic of this dissertation is to quantify the impact of complex pore and grain structures on electrical resistivity and dielectric permittivity measurements of rock samples. Through the quantification of these impacts, this dissertation proposes a new dielectric permittivity model and a joint interpretation model (combining dielectric permittivity and electrical resistivity measurements) to improve the assessment of petrophysical properties of formations such as water/hydrocarbon saturation. In addition to the main research topic, this dissertation also designs and conducts laboratory experiments to quantify the impact of water-filled porosity and salinity on the dielectric permittivity of brine-saturated rocks. In this dissertation, pore-scale numerical simulations are implemented to estimate the effective electrical resistivity and dielectric permittivity of rock samples. Then, diffusive directional tortuosity, directional connectivity, and electrical directional tortuosity are introduced and applied to quantify the impact of pore and grain structures in rock samples on electrical resistivity and dielectric permittivity measurements. In the case of organic-rich mudrocks, the impacts of mature kerogen and pyrite networks are also quantified on electrical resistivity and dielectric permittivity of the rocks. The two proposed models in this dissertation, a new dielectric permittivity model and a joint interpretation model, take into account the spatial distribution of rock components and can provide more reliable estimation of water/hydrocarbon saturation in both conventional and unconventional formations when compared to conventional models such as the Complex Refractive Index Model. It is observed that formation water salinity affects the sensitivity of effective electrical resistivity to the connectivity of conductive components, as well as the sensitivity of dielectric permittivity to water-filled porosity. Experimental results showed that the impact of water salinity on high-frequency dielectric permittivity of brine-saturated rocks needs to be taken into account in the interpretation of dielectric permittivity measurements, especially for rock samples with water-filled porosity of higher than 15%. Overall, the outcomes of this dissertation improve the interpretation of electrical resistivity and dielectric permittivity measurements for reliable assessment of water/hydrocarbon saturation. Advisors/Committee Members: Heidari, Zoya (advisor), Sun, Yuefeng (committee member), Efendiev, Yalchin (committee member), Gildin, Eduardo (committee member).