Assessment of EOR Effectiveness via Field-Scale Sediment and Permeability Changes in Mature Oil Sands Reservoirs

Thesis Abstract

This study addresses the challenge of sustaining enhanced oil recovery (EOR) performance in mature oil sands reservoirs by investigating field-scale sediment displacement and permeability evolution under EOR operations. The aim is to quantify how optimized EOR schemes influence pore structure, fines migration, and permeability distribution, and to relate these changes to incremental oil recovery in real-field settings. Specific objectives include (1) characterizing pre-EOR reservoir heterogeneity and baseline permeability using core data, well logs, and formation testers; (2) monitoring sediment transport and fines migration during EOR cycles with tracer tests and production/injection history; (3) quantifying field-scale permeability changes through time-lapse reservoir simulations calibrated with production data and measured rock properties; (4) evaluating the relationship between sedimentary parameters (particle size distribution, sorting, mineralogy) and EOR performance; and (5) developing predictive indicators of EOR effectiveness under varying injection strategies for mature oil sands plays. A mixed-methods approach is employed. The population comprises mature oil sands reservoirs undergoing polymer, solvent, or steam-assisted EOR processes within the Athabasca-type plays. The sample includes data from five representative field pilots, encompassing 40–60 horizontal producer wells and 15–20 injector wells across 3–5 reservoir units, with historical production spanning 6–12 years. Data collection instruments include wireline and core plug analyses for sediment and permeability characterization, high-resolution seismic and time-lapse (4D) monitoring for spatial permeability evolution, production and injection rate records, pressure and temperature gauges, tracer-sweep surveys for fines migration, and laboratory measurements of grain size distribution, mineralogy, and pore throat characterization. Analytical techniques encompass probabilistic resilience analysis of permeability distributions, regression analysis to link sediment parameters with permeability changes, ANOVA to compare EOR schemes, and time-series analysis of production data. Numerical modeling uses dual-porosity, dual-permeability reservoir simulators calibrated with 4D seismic constraints and core-derived flow properties, augmented by a Bayesian updating framework to quantify uncertainty. The study also applies transport models for fines migration and coupled geomechanical models to assess sediment mobilization risks under thermal and chemical EOR conditions. The theoretical underpinning integrates the concepts of reservoir heterogeneity, fines migration theory, and non-Darcy flow effects in tight sands, with two named theories guiding interpretation Darcy–Forchheimer dual-porosity flow and hydromechanical coupling theory for sediment mobilization. Key expected findings include (i) quantified increments in oil recovery correlated with field-scale permeability redistribution and sediment displacement patterns, (ii) identification of critical sediment regimes and mineralogical compositions that amplify or constrain EOR effectiveness, (iii) delineation of spatial heterogeneity zones where fines migration reduces injectivity or promotes bypassed oil, and (iv) development of empirically validated indicators (e.g., permeability variance thresholds, fines mobility indexes) that predict EOR performance under specific injection schemes. The study anticipates that moderate fines mobilization in high-permeability streaks may enhance sweep efficiency in certain stalked boulder-porosity intervals, while excessive fines migration in clay-rich units could deteriorate injector performance. The intended contribution advances knowledge in petroleum engineering by linking field-scale sedimentary characteristics to EOR effectiveness in mature oil sands reservoirs, providing a transferable framework for predicting EOR outcomes in heterogenous systems and offering guidance for field-scale optimization of injection strategies. The study concludes that integrating sedimentology, 4D monitoring, and calibrated transport-geomechanical models yields robust predictive capability for EOR performance, enabling operators to tailor EOR programs to reservoir-specific sedimentary architectures. Practical recommendations include adopting targeted sand-and-gravel stratigraphy-aware injection planning, implementing proactive fines-management practices, and applying Bayesian updating workflows for ongoing performance assessment to minimize uncertainty and maximize incremental recovery.