Enhanced Oil Recovery Using Silica Nanoparticles: Sandpack Flooding Experiments in a Low Salinity Environment

Mobilizing and recovering crude oils from geological strata is crucial for the management and development of petroleum reservoirs. Unlike conventional oil production methods, enhanced oil recovery (EOR) processes can increase the recovery of most oil products from the reservoir above the secondary recovery baseline. Recent studies have demonstrated that nanoparticles (NPs) have the potential to improve EOR processes. Therefore, understanding how NPs impact the mechanisms that govern the interaction between the fluids interface, the fluid-solid interface, and the mobility of oil in porous media is critical to alter the properties of nanofluids for specific geofluid conditions and increase EOR efficiency. The objectives of this research are to determine the impacts of NPs on the fluid-fluid interfaces, the fluid-solid interfaces, the mobility of oil in porous media, and oil recovery. This research seeks to evaluate the different production processes in petroleum engineering commonly implemented at the field scale. Sequencing is a process that is heavily implemented by the petroleum industry and involves the injection of an aqueous phase (brine) prior to the injection of EOR fluid. Non-sequencing involves the immediate injection of chemical-EOR fluid to displace crude oil and is more of a theoretical process which allows for a direct comparison of the immediate impact of chemical-EOR fluid with oil displacement associated with waterflooding and sequenced chemical-EOR injection. In this study, silicon dioxide nanoparticles (SiO2 NPs) were employed to improve the efficiency of the chemical-EOR process that utilizes surfactant flooding in an oil wet sandstone aquifer analogue. Although sandstone aquifers are most frequently water wet, the imbibing liquid is crude oil in these experiments, resulting in more conservative oil recovery rates. Quartz silica sand was used to simulate the porous media material. Light (West Texas Intermediate, or WTI) crude oil was selected as the oil phase, due to its ubiquity as a global standard for crude oil characteristics and price. De-ionized water and one weight percent (1 wt %) NaCl brine, with 2 critical micelle concentrations (CMC) of anionic surfactant (sodium dodecyl sulphate, or SDS) and concentrations of silica nanoparticles including 0, 0.01, and 0.1 wt% were used to create the nanofluids. Experiments were conducted to measure the contact angle between the microscope glass slide and SiO2 / SDS - based aqueous nanofluid systems. The contact angle between the aqueous nanofluid and the microscope glass slide is a factor used to assess the alteration of the sand wettability, a property critical to the mobilization of crude oil from porous media. Microscope glass slides were used to simulate quartz silica grain surfaces for contact angle measurements. Sandpack flooding column experiments were conducted to test the impacts of the various nanofluids injected into the crude oil saturated sandpack on the cumulative and fractional recovery rates of WTI crude oil. The effective oil displacement by the SiO2 / SDS – based aqueous nanofluids tested was monitored over time and expressed as a function of the number of pore volumes (PVs) of fluid injected into the system during various processes. Cumulative and fractional oil displacement are plotted as a function of PVs injected during events designed to simulate common practices in the petroleum industry. Primary Oil Recovery is simply the process of oil recovery due to natural gravity drainage or pressure head driving fluid from the subsurface. This process is analogous to the initial oil injection phase, during which the column is saturated with oil to the extent that WTI crude oil is flowing out the effluent tube and into the designated pre-experiment effluent sample tube. Secondary oil recovery, or waterflooding as it is commonly called, involves the re-injection of natural aquifer fluids such as water or brine to displace an additional amount of crude oil. Finally, tertiary or Enhanced Oil Recovery (EOR) involves the injection of heat, gas, or chemicals to further improve the displacement efficiency of crude oil. This research seeks to evaluate the different impacts of processes commonly implemented at the field scale. The research demonstrated that SiO2 NPs can be used with surfactants such as SDS in crude oil to change the wettability of petroleum reservoir systems from oil wet to water wet, allowing for a more efficient displacement of crude oil and consequently yielding significantly higher oil recovery rates