Adsorption of surfactants in the presence of two fluids for enhanced oil recovery : experimental investigation using the QCM-D

Abstract

Rock wettability when in contact with two fluid phases - oil and water - plays an important role in oil recovery from hydrocarbon reservoirs. Water injection as a pressure maintenance mechanism performs substantially better in water wet reservoirs compared to oil reservoirs. This is due to low relative permeability to water and tendency of water to imbibe and displace in a water-wet system. A whole category of Enhanced Oil Recovery (EOR) processes consists in altering the rock wettability towards more water wetting used in the Chemical EOR industry. Surfactant water injection is one of these processes. In this project, the adsorption of surfactants on silica surfaces saturated with oil is examined using the Quartz Crystal Microbalance with dissipation (QCM-D) technique. This mineral mimics sandstone reservoirs. The effect of Sodium Dodecyl Sulfate (SDS) and Triton X-100 concentration is experimentally investigated, along with the effect of salinity. One light crude oil (crude oil A) and one moderately heavy crude oil (crude oil B) were used for the desorption process. The maximum amount of oil desorbed from the silica surface has reached 27.4percent and 22.6percent using SDS and Triton X-100 respectively. These values are around the CMC. In addition, SDS did not help in reaching higher amount of desorption when adding salt to the medium. However, using Triton X-100, the total percentage of oil desorption has increased from 87.3percent to 92.9percent upon addition of NaCl. As the concentration of surfactant increases more crude oil B has been desorbed from the silica surface until reaching the CMC value where no more desorption occurs. In addition, increasing the salinity of the control solution has decreased the CMC of two surfactants leading to reaching the maximum desorption using lower surfactant concentration. On another note, SDS, an anionic surfactant has led to more desorption of oil from a negatively charged surface than the nonionic surfactant Triton X-100.