Describing the Flow Behavior of Smart Water in Micromodels with Wettability Modified Pore Structures

Abstract

Abstract This work focuses on oil recovery processes by smart-water injection in micromodels with different wettabilities. It provides detailed visualization of the displacements taking place during Smart-Water flooding at a pore scale level, whilst evaluating the effect of wettability on oil recovery. We propose a workflow for the evaluation of Smart-Water flooding including fluid-fluid and rock-fluid interactions. The methods studied comprise experiments with micromodels and core flooding. Artificial and real-structure water-wet micromodels (derived from Bentheimer sandstone material with three different permeability zones) were used to understand flow behavior and oil recovery. Subsequently, complex-wet and oil-wet micromodels helped understanding wettability and rock-fluid interaction. Synthetic-Sea-Water (SSW) was the benchmark fluid, and subsequently modified by diluting its composition. The effect of sulphate content in the brine was key in this work; polymer flooding was used as a final step to discard any possible further effects and as mobility control agent. Micromodel experiments conducted in this work indicate that Smart-Water flooding performs better in mixed-wet (artificial structure) than water-wet systems, but with seemly good results for oil-wet systems. The observation slightly differs from core flood experiments, where oil-wet conditions provided a better process efficiency. Smart-Water flooding in artificial oil-wet micromodels led to higher produced oil compared to SSW injection in water-wet system. This behavior was expected, since the spiked sulphate present in Smart-Water disturbed the ionic equilibrium in the micromodel system causing a release of the polar compounds of oil. This is understood as an improved interfacial viscoelasticity at the oil-brine interface (fluid-fluid interaction), promoting additional oil production/continuous flow and ganglia movement. Results obtained in mixed-wet micromodel showed that when Smart Water is spiked with sulphate a 3.13% higher recovery is obtained compared to SSW. Same trend was observed for oil-wet micromodel with additional recovery of 2.63%. As an overall result, Smart-Water flooding recovered higher oil than the SSW injection in oil-wet and complex-wet system as compare to water-wet. Majority of the work presented in the literature, have mainly focused on the evaluation of core flooding data for smart water injection. This work unlocks the potential of micromodels to study the micro-scale visual analysis of Smart-Water flooding through porous media. The workflow not only relies on oil-ganglia analysis and displacement efficiency evaluation, but also considers fluid-fluid and rock-fluid interactions.