Date of Award

December 2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Petroleum Engineering

First Advisor

Kegang Ling

Abstract

This dissertation investigates the influence of stress, mineralogy, and microstructure on the elastic and transport properties of reservoir rocks. A multi-scale framework integrating laboratory measurements, petrophysical inversion, and discrete-element simulations is developed to quantify the stress-dependent behavior of heterogeneous sedimentary formations relevant to hydrocarbon production and CO2 sequestration.

Core-scale experiments quantify velocity–effective stress and permeability–effective stress relationships in tight siliciclastic and mixed lithologies. Results demonstrate that pore-throat collapse and microcrack closure under confining stress cause systematic reductions in permeability and acoustic velocities. The derived empirical functions provide predictive capability for estimating in-situ stress effects on reservoir performance and time-lapse seismic response.

Integrated petrophysical and rock-physics modeling delineates the diagenetic and mineralogical controls on elastic behavior and reservoir quality. Multimineral inversion calibrated with X-ray diffraction and petrographic data reveals that quartz overgrowth, dolomitization, and anhydrite cementation significantly modify pore topology, porosity, and stiffness. The quantitative estimation of pore-filling and contact-cement fractions links diagenetic evolution to mechanical and flow properties, providing diagnostic parameters for injectivity and seal integrity assessment in CO2 storage intervals.

Grain- and fracture-scale simulations extend these analyses to resolve micromechanical processes controlling stress-dependent permeability and elastic response. Particulate discrete-element models quantify the influence of grain-size distribution on permeability reduction and deformation modulus. Three-dimensional distinct-element modeling of columnar-jointed rocks characterizes tensorial permeability evolution under poly-axial loading and demonstrates that variations in the intermediate principal stress control permeability anisotropy and flow orientation. Numerical results underscore the necessity of tensor-based formulations for fractured and jointed media.

Discrete-element models of composite granular rocks further elucidate the effects of inclusion geometry, orientation, and stiffness contrast on effective elastic moduli and damage localization. The evolution of stress–strain fields and crack propagation within binary mixtures establishes mechanistic links between microstructural heterogeneity and macroscopic anisotropy.

Collectively, these experimental and computational results establish a coherent, scale-bridging framework for characterizing stress-sensitive permeability and stiffness in geologically complex reservoirs. The integration of laboratory data, petrographic constraints, and discrete-element modeling provides a quantitative basis for incorporating stress, fabric, and diagenetic effects into predictive rock-physics models and reservoir simulators. The findings enhance understanding of permeability evolution and mechanical stability under varying stress regimes, contributing to improved reservoir characterization, CO2 injection optimization, and long-term containment evaluation.

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