Integrated Surfactant-Polymer Flooding for Cyclic Steam-Assisted Schemes: Design, Implementation, Evaluation

Thesis Abstract

Integrated Surfactant-Polymer Flooding for Cyclic Steam-Assisted Schemes Design, Implementation, Evaluation This study addresses the low recovery efficiency and high steam–oil ratio challenges in mature heavy oil reservoirs by integrating surfactant-polymer flooding with cyclic steam-assisted schemes to enhance sweep efficiency and mobility control while reducing thermal penalties. The aim is to design, implement, and evaluate an integrated EOR (enhanced oil recovery) strategy that couples surfactant/polymer flooding with cyclic steam stimulation (CSS) to maximize oil recovery, minimize energy intensity, and improve reservoir conformance. Specific objectives include (i) formulating a robust chemical system comprising a compatible surfactant and polymer for high-temperature, high-salinity conditions typical of CSS cycles; (ii) developing a workflow for sequencing and timing of CSS with polymer-surfactant (SP) injections to optimize micro- and macro-scale displacement; (iii) evaluating reservoir performance through laboratory coreflood experiments, numerical simulation, and sensitivity analyses; (iv) establishing optimal operating windows for chemical concentrations, injection rates, and steam cycles; and (v) providing implementation guidelines for field pilots, including economic and environmental implications. A mixed-methods approach underpins the methodology. The research adopts a design-based experimental framework complemented by a reservoir simulation component. Laboratory work utilizes high-temperature, high-salinity corefloods with Berea sandstone and oil taps to mimic reservoir conditions up to 250°C and salinity levels of 150,000–250,000 ppm. Surfactant and polymer formulations are selected based on interfacial tension reductions to below 10?3 mN/m, favorable viscosity enhancement, and thermal stability, drawing on amphiphilic polymer-surfactant systems with partially hydrolyzed polyacrylamide and alkyl benzene sulfonate-based surfactants. The sample consists of 12 core plugs, each subjected to a baseline CSS cycle followed by SP-assisted CSS cycles, with triplicate runs to assess reproducibility. Data collection instruments include high-temperature core flood rigs, nuclear magnetic resonance (NMR) porosity measurements, differential scanning calorimetry (DSC) for thermal stability, and real-time pressure transducers for breakthrough curves. A numerical model will be constructed in CMG STARS to couple polymer dynamics, surfactant transport, and steam heat transfer, calibrated against experimental data. The population of interest comprises mature heavy oil reservoirs amenable to CSS, with sampling focusing on geochemical compatibility and field-scale transition probabilities. Data analysis proceeds in three tiers. First, descriptive statistics and analysis of variance (ANOVA) assess coreflood performance across formulations and cycle sequences. Second, regression analysis and response surface methodology identify the relationships between chemical concentrations, steam pulse duration, and incremental oil recovery. Third, sensitivity analyses in the numerical model quantify the impact of key parameters, including adsorption losses, phase behavior, and mobility ratio alterations, validating a conceptual framework grounded in the theories of relative permeability alteration and thermal diffusion enhancement. The study tests hypotheses related to incremental recovery gains from SP-CSS integration, the trade-offs between chemical cost and oil gained, and the robustness of the approach under salinity and temperature variability. Anticipated findings include substantial improvements in cumulative oil recovery relative to CSS alone, driven by reduced interfacial tension, improved mobility control, and enhanced sweep efficiency within burn zones. The combination is expected to produce a favorable incremental oil recovery in the range of 8–15% OOIP under field-representative conditions, with steam–chemical synergy reducing peak steam ratio by 10–20% and lowering bypassed oil. The research contributes to knowledge by operationalizing an integrated design framework for SP-assisted CSS, providing validated SEM and PFR (specific enthalpy management) indicators for field deployment, and detailing criteria for chemical selection, cycle sequencing, and economic viability. The study concludes that the integrated scheme offers a viable pathway to rehabilitate depleted heavy oil reservoirs when designed with site-specific temperature, salinity, and rock–fluid properties. Recommendations include guidelines for pilot validation, optimization of chemical costs, monitoring strategies for reservoir cleanliness and stability, and policy implications for environmental performance and lifecycle assessment.