Comparative Analysis of Enhanced Oil Recovery in Conventional vs. Tight Reservoirs

Thesis Abstract

The increasing push to optimize hydrocarbon recovery has highlighted distinct performance gaps between conventional and tight reservoirs, where Enhanced Oil Recovery (EOR) techniques must be reassessed for viability, efficiency, and economic sustainability. This study addresses the problem of uneven EOR applicability and performance across reservoir classifications, aiming to establish evidence-based guidance for selecting, designing, and scaling EOR strategies in conventional versus tight settings. The specific objectives are (1) to compare the learned impact of chemical, gas, and thermal EOR methods on sweep efficiency and ultimate recovery across reservoir types; (2) to identify key reservoir–fluid–process interactions that govern EOR performance differences; (3) to develop a decision framework integrating reservoir characteristics, operational constraints, and economic metrics for cross-type EOR deployment; and (4) to validate the framework against field case studies and published benchmarks. A sequential mixed-methods research design is employed. The population comprises mature oil fields with well-documented production histories in both conventional and tight formations. A stratified purposive sample of 20 fields (10 conventional, 10 tight) is selected to ensure representation of carbonate and sandstone conventional reservoirs as well as shale and ultra-tight sand systems. Data collection integrates archival production data, rock–fluid properties, and EOR pilot results from field reports, supplemented by 30 in-depth interviews with reservoir engineers and geoscientists to capture operational nuances and decision rationales. Instrumentation includes a standardized data extraction template, semi-structured interview guides, and field-validated performance indicators. Validity is enhanced through triangulation of production metrics, core-flood data, and interview insights, while reliability is addressed via inter-rater coding checks for qualitative data and cross-field data reconciliation for quantitative metrics. Analytical approaches include (i) multivariate regression and ANOVA to quantify differential EOR performance across reservoir types while controlling for oil price, temperature, and reservoir heterogeneity; (ii) reservoir simulation using history-mmatching with both conventional and tight rock data to evaluate sweep efficiency under chemical, gas, and thermal EOR schemes; (iii) a conceptual framework grounded in theory of Enhanced Oil Recovery and the Theory of Reservoir Heterogeneity to interpret results; and (iv) a decision-support model integrating technical, economic, and risk parameters to guide cross-type EOR selection. The study will also apply a “best-worst case” scenario analysis to quantify robustness under data uncertainty. Expected findings indicate that conventional reservoirs exhibit higher incremental recovery with chemical and polymer flooding due to moderate heterogeneity and favorable wettability, whereas tight reservoirs demonstrate comparatively constrained mobility control but higher fossil energy penalties may be offset by gas-assisted gravity drainage and robust thermal methods where temperature profiles permit. The research anticipates that effective EOR in tight formations will depend strongly on nano-scale pore throat architecture, matrix-fracture connectivity, and precise formulation of surfactants and polymers to mitigate adsorption losses and high capillary pressures. The study will quantify the sensitivity of recovery factors to reservoir permeability, porosity, and confining stress, and will identify thresholds beyond which EOR advantages diminish. The contribution to knowledge includes (i) a comparative, data-driven evaluation of EOR performance across conventional and tight reservoirs with an explicit, replicable methodology; (ii) a validated cross-type decision framework that integrates technical feasibility with economic viability; and (iii) actionable guidelines for tailoring EOR technologies to reservoir class, including recommended pilot design, process conditions, and monitoring metrics. The main conclusion posits that while conventional reservoirs generally benefit more from traditional EOR approaches, tight reservoirs require a bespoke integration of mobility-control and energy-efficient methods underpinned by robust characterization and real-time surveillance. Recommendations emphasize prioritizing pilot studies in mixed-system basins, developing reservoir-specific surfactant–polymer formulations for tight rocks, and investing in digital twin platforms to continuously optimize EOR performance across reservoir types.