New Insights into the Effect of Micro-Dispersion During Core Flooding Experiments Using Low-Salinity Water

Accurate modelling of low-salinity water flooding process is challenging, as illustrated by the ongoing debate surrounding its underlying causes, highlighting the uncertainty about the complex relationships between water, oil, and rock in porous media. The effects of low-salinity water are currently simulated using mechanistic techniques such as multi-ion exchange and fine particle migration (and even calcite interaction); however, further research in modelling is essential given the growing interest in fluid-fluid interaction as a potential influencing factor during this process. This paper aims to improve the model of fluid flow performance in laboratory experiments during low-salinity water flooding.

To investigate the interactions of fluids with low-salinity water, this paper presents a series of tests and experiments that revealed a promising phenomenon associated with enhanced oil flow or recovery. This new formation is termed "micro-dispersion". The paper also highlights several laboratory studies and fluid property data, along with a hypothesis regarding its relationship to the polar components of oil. A smaller sample from this group is used for data collection and experimental analyses.

Using a commercial black oil model, several core flooding tests from a published research paper were predicted. These studies examined the micro-dispersion of water in oil to varying degrees during flooding with low-salinity water, yielding mixed results. The goal of the modelling effort was to ensure reliable experimental performance in terms of capillary pressure and relative permeability. Changes in these properties are thought to indirectly indicate changes in wettability. Performance differences (e.g., pressure anomalies) across measured results in some studies highlight other, often overlooked, effects that may be related to fluid interactions.

New insights are provided into the effectiveness of low-salinity water for improving oil recovery. This benefit is attributed to two enhancing factors: one through the fluid and rock interactions in the system and the other as a result of inter-fluid interactions. Although the first factor represents a change in wettability, this effectiveness was found to be correlated to the experimental observation of micro-dispersion.

However, some implications have yet to be recognised or addressed and require further research. It was difficult to determine which outcome was most closely related to wettability changes, although our research demonstrates a variety of effects during low-salinity water flooding. Consequently, a direct component or parameter, other than one assumed or based on the inverse of performance variability, must be linked to the onset of the subsequent effect in the process.