Porosity-Limited Transport during Two-Phase Surfactant/Polymer Floods in a Layered Sandstone

Surfactant/polymer flooding presents itself as an attractive technique for the full utilization of current reservoirs given its potential to yield high oil recoveries. Despite this appeal, discrepancies between laboratory and field results exist and limit their industrial implementation. Within the scale-up process, corefloods serve as a key tool for the evaluation of the recovery potential; however, due to complexities in the fluid system itself, these are commonly performed on homogeneous core samples. To further understand this, we conduct a surfactant/polymer flood as a tertiary recovery method within a Nugget sandstone core. A notable feature of the chosen core is its stratified nature, with layers of high and low porosity characterized via X-ray CT. Via the use of direct imaging, coupled with a step tracer test, preferential flow paths and slow-to-ingress regions of the core are identified, information that is then coupled with the surfactant/polymer flood results to better understand the mechanisms at play. To better understand the influence of the structured heterogeneity present within the core, the results are compared to an analogous experiment within a homogeneous sandstone core. We note the inability of an oil bank to form and the comparatively larger variability of the recoveries between different porosity layers within the core. Lastly, we highlight how, despite a high overall recovery of 80%, inefficiencies in the displacement process are still present and only observable due to the direct imaging methodology implemented, ultimately showcasing its value in this context.