enhancedoilrecoveryMethoden

Enhanced oil recovery methods (EOR) are techniques used to increase the amount of crude oil that can be recovered from an oil reservoir beyond what is produced by primary and secondary recovery. EOR methods modify the physical properties of the reservoir fluids or the rock to improve displacement efficiency, often after conventional methods have diminished production.

The main categories of EOR are thermal, gas (or miscible) injection, and chemical methods. Thermal EOR uses heat, most commonly steam, to lower oil viscosity and improve flow. Techniques include cyclic steam stimulation and steam flooding, widely used in heavy oil and bitumen reservoirs. Gas injection EOR uses gases such as carbon dioxide, nitrogen, or hydrocarbon gases to maintain reservoir pressure and enhance oil mobility. In miscible gas flooding, the injected gas mixes with oil, reducing interfacial tension and improving sweep efficiency; immiscible gas flooding relies mainly on pressure effects. Chemical EOR involves injecting chemicals to improve displacement: polymer flooding increases the viscosity of the displacing water to reduce fingering; surfactant flooding lowers interfacial tension between oil and water; chemical combinations, including surfactant-polymer systems, aim to maximize recovery in specific reservoirs.

Some EOR approaches, such as microbial or MEOR methods, use microorganisms or their metabolic products to alter reservoir conditions and mobility. Environmental and economic considerations are central to EOR decisions, including energy input, capital costs, reservoir compatibility, and potential for CO2 sequestration or groundwater contamination. EOR is typically applied in mature fields where remaining oil would otherwise be unrecoverable, contributing to incremental recovery and extending field life.