The Effect of Asphaltene Structure on Wettability Alteration during Enhanced Oil Recovery Using Carbonated Water

The Effect of Asphaltene Structure on Wettability Alteration during Enhanced Oil Recovery Using Carbonated Water

The presence of the polar compounds in the crude oil play a major role in dictating the type of wettability. The objective of this study is to find out the effect of the structure of asphaltene and other polar compounds on wettability alteration during enhanced oil recovery using carbonated water. The presence of heavy components in the crude oil, for instance, asphaltene and resins play a major role in the wettability reversal.

Effect of pressure was investigated on crude oil /carbonated water/ pure Dolomite system using carbonated water (200 cm³ liquid CO₂ mixed with 800 cm³ of brine at the initial pressure of 2000 psi. On pure Dolomite solid surface was saturated with crude oil containing 11.6 wt% of asphaltene. Decreasing Dolomite content in mixed Dolomite/Calcite systems caused shift in contact angle from oil negative intermediate wet to weakly water wet regardless of saturating fluid phase.

The characterization of asphaltene using Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS) has clearly indicated that asphaltene sample consist of condensed hydrocarbon and sulfur aromatic molecules with one or two sulfur atoms per molecule. The weight average number of fused aromatic rings for hydrocarbon molecules ranges from 6 to 7 and for sulfur containing molecules having an average of 8 aromatic rings,

Using FT-ICR MS, it was found that asphaltene contains almost similar number of poly-aromatic rings with different average alkyl chain length. However, the total S and N content was different in each oil sample. The more total S and N content leads to more polarity and more oil wet behavior. It seems that the difference wettability alteration is mainly rooted to the difference in polarity of the oil.