Experimental investigation of the effect of the chemical flooding on the effective zeta potential in rock samples - improved understanding of the EOR

The aim of this research is to determine experimentally the effects controlled salinity waterflooding (CSW) (low-salinity effect) has on chemical floods. This will be achieved by measuring parameters such as the zeta potential that are influenced by both chemical flood and CSW schemes and to observe if any additional changes in these parameters due to synergy correlate to a meaningful positive influence on incremental oil recovery. The inspiration for this PhD came from recent evidence that suggested that changes in the zeta potential of the oil-brine and mineral-brine interfaces lead to changes in the wetting state in CSW experiments. Changing of the wetting state to mixed-wet in CSW experiments and mixed/water-wet in chemical floods have been identified previously as favourable to increase incremental oil recovery. Hence this research should improve our understanding of wettability control and can improve the performance of these flood schemes.
The work planned for this PhD includes: a literature review and meta-analysis of chemical floods and CSW in carbonates and sandstones, experimental work including single-phase & multi-phase behaviour tests and core flood experiments. The single-phase experiments will focus on measuring the key parameters that characterise how the reservoir (rock sample) and fluids (formation brine, injection brine or crude oil) interact with each other such as permeability and zeta potential of the mineral-brine interface. The multi-phase experiments will be conducted at the same time as the core flood experiments which will determine the ultimate oil recovery of the flood and will allow for the determination of many factors that characterise how the oil, formation brine and injected brine interact with each other such as: relative permeability and zeta-potential measurements of the oil-brine and mineral-brine interface. The equipment will be capable of taking live readings so changes in these parameters can be monitored in real time. The experiments will be performed at conventional reservoir conditions and the properties and compositions of the initial brines, oils and effluents will be evaluated. The altered variables and how they will be manipulated to achieve optimum results in this experiment will be determined by the literature review & meta-analysis and by the single-phase and multi-phase behaviour tests.
Other sub-objectives that have been identified as potential further research include: optimising chemical floods with CSW by reducing the amount of chemical used to achieve similar performance to conventional chemical floods, the effects of strontium in the formation brine, alteration of the temperature the experiments are performed at, different formations (carbonates and sandstones) and what effects hard and soft aquifer water replacing seawater as a component of the CSW scheme has on the performance of chemical flooding + CSW.
This project will have applications in the oil industry as a potential novel enhanced oil recovery technique. The project also aims to enhance our understanding of chemical floods and its synergistic effects with CSW by determining how factors that haven't previously been considered such as the zeta potential of the oil-brine and mineral brine interface influence ultimate oil recovery. Accounting for these factors could explain why some CSW and chemical floods either fail or underperform.