Comparative Study on Adsorption of Biologically Generated Surface Active Agents on Carbonate and Sandstone Rock Surfaces

Surfactant adsorption at rock-fluid interface is fundamental to wettability alteration that is relevant to enhanced oil recovery process but the extent of this adsorption can also impact the economic viability of the surfactant application in the process. In this paper, adsorptions of two biologically generated surfactants (rhamnolipid and greenzyme) on carbonate and sandstone rock surfaces have been studied and reported. The rocks’ main components and physicochemical makeup were determined with the use of X-ray diffraction and scanning electron microscopy. The compositional analyses of sandstone and carbonate rocks show the dominant components as quartz and calcite respectively. From the adsorption investigations, rhamnolipid tends to show higher surface activity than greenzyme. It also shows stronger affinity for sandstone rock surface than carbonate while greenzyme shows stronger affinity for carbonate surface. Furthermore, decrease in adsorptions of rhamnolipid and greenzyme with increase in temperature and decrease in salinity was observed in all the systems. Finally, the adsorption models suggest rhamnolipid adsorption process to be mono-layer in nature, while greenzyme adsorption tends to be mono-layer at low adsorption and heterogeneous at high adsorption.