Wettability has been recognized as one of the most important factors affecting enhanced oil recovery (EOR). Several studies have shown the influence of different EOR agents on the reservoir rock wettability and oil recovery rates. However, most of these studies are not considering the reservoir conditions i.e. the high temperature and high pressure.
Low interfacial tension (IFT) between the crude oil and the injected fluid is generally considered to be an important requirement for mobilization and displacement of the oil. Using CO2as an injection fluid is gaining a lot of interest since there is also a possibility for simultaneous CO2capture and storage. To be able to predict the CO2flooding capacity, it is necessary to study the interfacial tension change between CO2– water / oil with pressure, temperature and CO2concentration. The influence of pressure on interfacial tension between CO2– water/brine and CO2-crude oil has been studied. Generally, it has been found that the IFT decreases with increasing pressure for both systems. This has been linked to adsorption of CO2molecules and the higher CO2solubility at elevated pressures.
Surfactant flooding is another much used EOR method. The two main functions of surfactants in enhanced oil recovery is either to reduce the interfacial tension or wettability alteration. For wettability alteration with surfactants two different mechanisms have been proposed; coating and cleaning mechanisms. In coating mechanism, the surfactant is adsorbed onto the oil-wet solid surface. Cleaning mechanism, on the other hand, refers to a process where surfactant molecules complex with contaminant molecules adsorbed from crude oil to strip them off the rock surfaces.
It is well-known that the surfactant behavior can change drastically at high temperatures. The effect of pressure is less studied. However, to be able to measure water-based surfactants near and above 100 °C, high pressures are needed to prevent boiling.
If you would like to see more examples how pressure affect the wettability, please download the slide deck below.
Susanna is an Application Scientist at Biolin Scientific. In her PhD thesis, she developed fabrication methods for a new type of inorganic-organic polymers. Microfabricated polymer chips were utilized as tool for biomolecule separation in analytical chemistry.
