This work describes two types of laboratory chemical enhanced oil recovery (EOR) flooding experiment. Results are presented for micromodels and core floods (Bentheimer sandstone). Saturation behaviour is followed directly by optical microscopy in the micromodels and these images enable interpretation of the saturation development in the sandstone core as determined using spatially resolved nuclear magnetic resonance (NMR). The oil is a simple alkane (decane) but the surfactant combination is designed for EOR. The work is supported by surfactant phase behaviour, oil-water interfacial tension (spinning drop), and effluent analysis (surfactant concentration). The data and analysis presented here confirms much of that previously inferred general behaviour, using modern direct observation techniques (NMR and microfluidics). These micromodel data directly illustrate local behaviour of middle phases within the porous network, the mobilisation of ganglia, and the formation of middle phase from ganglia. The correlation of micromodel data with spatially resolved core data is striking, and allows identification of behaviours within the core.

An aqueous formulation of anionic surfactants and butan-2-ol is injected into decane-saturated porous media. The formulations were selected to give rise to equilibrium L1 and L3 phase behaviours at different NaCl concentrations. The aqueous formulation contains 1% of each of a C12,13 alcohol-propoxy-sulfate and a C20-24 internal olefin sulfonate (supplied by Shell Chemicals) and 8% butan-2-ol. This formulation with 2% and 4% NaCl give rise to L1 and L3 phase behaviour and oil-water (measured) interfacial tensions of 0.10 and 0.006 mN/m, respectively, which at the flow rates used give corresponding capillary numbers of 3.5×10-5 and 6.0×10-4, compared to a surfactant-free flood value of ~ 1×10-7. Both surfactant formulations provide improved oil displacement from the core. Adding surfactant in “L1-based” formulations reduces interfacial tension. However, “L3-based” formulations give ultra-low interfacial tensions and hence better recovery, exhibiting complex behaviour consistent with (1) the formation of, and then (2) the displacement of, microemulsion phases.

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