Date of Award

January 2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Energy Engineering

First Advisor

Olusegun S. Tomomewo

Abstract

The 2015 Paris Accord sparked unprecedented global decarbonization to net-zero CO2 emissions. Carbon storage (CS), an important technology for addressing climate change, requires mandatory monitoring using 4D seismic approaches to demonstrate conformance and containment to meet regulatory requirements that demonstrate safety, performance understanding, and operational long-term stability. Although conventional amplitude- and velocity-based 4D seismic monitoring approaches detect CO2, they cannot adequately quantify CO2 saturation and pressure for conformance compliance validation. Therefore, this research investigated the potential of rock physics modeling to identify optimal CO2-saturation quantifiers and the potential of seismic inversion to link rock physics to accurately extract CO2 saturation from 4D seismic data using a novel pseudo-well assisted prestack seismic inversion approach deployed to the Sleipner storage dataset. The results showed that a patchy mixing (i.e. Brie, e = 4) offered a plausible balanced velocity-saturation calibration for CO2-brine substitution in the Utsira storage reservoir. The findings identified that lambda‐rho (λρ) depicted an effective/optimal CO₂ saturation quantifier in the storage complex, with the highest sensitivity and strongest correlation (R² > 0.99) among elastic attributes. The inversion results suggested that CO2 is discernible in a range of fluid-sensitive impedances (i.e. Vp, AI, Vp/Vs, and λϱ) while showing a consistent decrease with injection time. The analyses demonstrated that λρ accurately quantified CO₂ saturation, strongly correlated with the simulation data (R² = 0.81), effectively matched containment maps, and showed moderate-to-low saturation uncertainty (±3–7.3%) from multi-attribute saturation-based assessments. This result significantly outperformed predictions using Vp, Vp/Vs (R² = 0.6), and AI (R² = 0.48). The results were also corroborated with a 2D-synthetic time-lapse impedance model, especially using λϱ, which matched respective 4D plume observations. The findings showed that S-wave velocity could sufficiently quantify effective stress/pressure changes with negligible impact of CO2 saturation. The findings can support safety and simulation validation accuracy that enhances containment and conformance assessment and facilitates the reliable measurement, monitoring, and verification of data for regulatory compliance. The findings reinforce 4D seismic quantification as a critical energy engineering tool for precise temporal reservoir analysis, enabling accurate evaluation of storage resource utilization, thereby enhancing CS as a sustainable climate mitigation technology.

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