Assessing Subsurface CO2 Storage Integrity for UAE-Based EOR Operations

Thesis Abstract

The rapid expansion of enhanced oil recovery (EOR) in the United Arab Emirates relies on subsurface CO2 injection to sustain reservoir pressure while complicating long-term integrity assessments due to complex geology, variable sealing capacity, and potential leakage pathways. This study addresses the critical problem of ensuring CO2 storage integrity in UAE EOR operations, focusing on pre-and post-injection monitoring, risk identification, and mitigation within carbonate and clastic reservoir–cap rock systems. The aim is to develop a robust, field-scale framework for assessing storage integrity that integrates geological, geophysical, geochemical, and operational indicators to support safe, compliant, and economically viable CO2-EOR deployment. Specific objectives are (i) to characterize reservoir and cap rock properties relevant to CO2 containment across selected UAE fields; (ii) to evaluate seal integrity and potential leakage pathways using integrated petrophysical, sequence stratigraphic, and structural analyses; (iii) to quantify storage risk through probabilistic pore-scale and reservoir-scale modeling, including CO2 plume migration and estimate of maximum allowable leakage rates; (iv) to validate monitoring strategies using time-lapse seismic, borehole pressure monitoring, and geochemical tracers; and (v) to develop a decision-support framework linking monitoring data to operational actions and regulatory compliance. The methodology adopts a concurrent mixed-methods approach. The population comprises five UAE oil fields with established CO2-EOR programs and one pilot sequestration site, with a target sample of 50-70 wells and surrounding geologic units. Data collection employs (a) well logs (LWD/MWD, porosity, permeability, capillary pressure), core samples (n?120 cores) for cap rock and reservoir characterization, (b) time-lapse 3D seismic datasets (pre- and post-injection) spanning at least four years, (c) in-situ reservoir pressure and temperature records from monitoring wells (minimum 4 years of history), and (d) geochemical tracers and produced fluid samples for phase behavior and mineralogical analyses. Instruments include nuclear magnetic resonance (NMR) porosity measurements, mercury injection capillary pressure (MICP), X-ray diffraction (XRD) for mineralogy, and natural gamma and resistivity tools. The study uses a probabilistic risk assessment framework combined with physics-based reservoir simulation. Data analysis integrates (i) multivariate statistical methods and regression analyses to correlate lithofacies, fracture density, and seal properties with observed CO2 breakthrough indicators; (ii) Bayesian updating to refine leakage probability distributions as new data emerge; (iii) reservoir-scale CO2 flow modeling with TOUGHREACT/CMS-COUPLE to simulate plume migration, cap-rock integrity, and mineral trapping; (iv) time-lapse seismic attribute analysis and closed-loop inversion to monitor plume extent; (v) geochemical modeling to evaluate mineral-fluid reactions affecting seal stability; and (vi) thematic analysis of operator practices to identify procedural risk drivers, framed by the efficiency-equity theory to assess stakeholder compliance impacts. The theoretical backbone combines the containment theory of CO2 storage with the risk governance framework and barrier analysis (probabilistic barriers, dynamic containment, and early-warning signals). Expected findings include (i) quantified correlations between cap-rock properties and seal performance, (ii) probabilistic estimates of leakage risk under varying injection rates and reservoir pressures, (iii) validated monitoring protocols with sensitivity analyses identifying the most informative indicators (time-lapse seismic amplitudes, reservoir pressure transients, and tracer breakthrough timing), and (iv) a decision-support dashboard linking observed indicators to recommended operational actions. The study contributes to knowledge by integrating field-scale UAE CO2-EOR data into a holistic storage integrity framework, advancing methodology for predicting seal breach likelihood, and providing a validated workflow for monitoring program design tailored to Middle East geology. Practical implications include improved risk-informed operational decisions, enhanced regulatory reporting, and a scalable approach for transitioning CO2-EOR to safe storage. The main conclusion anticipates that a combined monitoring-software workflow, anchored in Bayesian updating and physics-based simulation, can reliably constrain leakage probabilities within regulatory thresholds under typical UAE reservoir conditions. Recommendations emphasize ongoing data integration, refinement of cap-rock characterization protocols, and adoption of standardized reporting formats for CO2 storage integrity in UAE EOR operations.