Toward mechanistic understanding of wettability alteration in calcite and dolomite rocks: The effects of resin, asphaltene, anionic surfactant, and hydrophilic nano particles

Wettability as related to an oil reservoir represents a fluid 's propensity to adsorb or stick to a solid surface in the presence of another immiscible liquid. Therefore, wettability is a key aspect in assessing the degree of recovery of oil from the reservoir. This paper aims at the investigation of the effect of resin, asphaltene, anionic surfactant, and hydrophilic nanopartides on the wettability alteration of calcite and dolomite rocks. In order to provide a better insight into wettability alteration, several laboratory tests were carried out including energy dispersive X-ray (EDX) analysis, Fourier transform infrared spectroscopy (FTIR), and Scanning electron microscopy (SEM). The contact angles measured on the calcite and dolomite rock surfaces for resin (1000 ppm in toluene) after three weeks were 88 degrees and 93 degrees, respectively. The results of contact angle analyses as a screen for two rocks (calcite and dolomite) wettability showed that resin altered the wettability of rock samples to oil-wet. Also, asphaltene as a heavy and polar component has more influence than resin on the wettability alteration towards oil-wet state. The polarization interaction mechanism is the principle method for altering the wettability of samples by asphaltene and resin. EDX analysis illustrated that the amount of carbon and oxygen after aging rocks in oil, asphaltene, and resin increased, and the heteroatoms N and S were appeared on the calcite and dolomite surfaces. Afterwards, the combination of silica (SiO2) nanofluid and anionic surfactant (sodium dodecyl sulfate (SDS)) for modification of wettability of oil-wet carbonate surface was investigated. The most significant changes were observed after 24 h of contacts of rocks with a mixture of nanofluid and anionic surfactant. The contact angle decreased from about 88 degrees to 16 degrees for calcite and from 93 degrees to 15 degrees in the case of dolomite. The main mechanisms responsible for wettability modification by SiO2-SDS surfactant are: first) hydrogen bonding between the hydroxyl groups of silica nanopartides and the tail of the anionic surfactant, second) the adsorption of SiO2-nanopartides to the carbonate rock substrate due to a high degree of negative charges. (C) 2020 Published by Elsevier B.V.

Automated summary

This study investigates the impact of resin, asphaltene, anionic surfactant, and hydrophilic nanoparticles on the wettability alteration of calcite and dolomite rocks. The results show that these components significantly affect the wettability of the rocks, with resin and asphaltene playing a key role in altering the rocks towards an oil-wet state. The use of silica nanofluids and anionic surfactants also showed promising results in modifying the wettability of carbonate rock surfaces.