Heavy-oil recovery improvement by additives to steam injection: Identifying underlying mechanisms and chemical selection through visual experiments

Abstract

To mimic the gravity assisted drainage and flooding type, steam displacement tests we performed previously (Bruns and Babadagli, 2017) on cores saturated with 27,000 cP heavy-crude-oil; a visual Hele-Shaw model was designed to simulate the same process and identify the physical characteristics of the steam-condensate-oil interface and the role played by added chemicals. The majority of the chemicals/chemical blends showed either improvement in the rate or ultimate recoveries in the coreflooding tests and, based on this data, the best performing and the most thermally stable chemicals were selected for the visual tests. These chemicals include ionic liquids, anionic surfactant (linear toluene sulfonate), non-ionic surfactants, biodiesel (thermally stable surface active agents), solvents (heptane), and nano-fluids (silicon oxide). The chemical solution was injected at a constant rate and pressure after being vaporized in an oven along with steam; the whole process was recorded with a camera.The contribution to recovery improvement through these phenomena in flooding and gravity controlled cases were identified. Foaming, emulsification, and IFT reduction yielding reduced drag forces between two phases at the interface and were observed to be the main reason for positive contribution of chemicals. Biodiesel exhibited a diffusion-like behavior near the injection port where no residual oil was noticed. The solvent (heptane), simulating ES-SAGD, stabilized the flow of steam in the late stage of the experiment due to the viscosity reduction. Improved oil + condensate drainage was assumed to be the contributing mechanism because of the change in surface properties during the injection of the ionic liquid. Nanoparticle, silicon oxide, and the linear toluene sulfonate (LTS) showed similar improvements in tip-splitting of the displacing fingers. It was concluded that the interfacial tension (IFT) reduction resulted in a wider occupation of the Hele-Shaw cell (better lateral sweep). Non-ionic surfactants showed different emulsion capabilities and high efficiency in steam/condensate displacement with a higher HLB (hydrophile - lipophile balance) value.