Nona Semana Integrada do Instituto de Física de São Carlos

Study of interaction between calibrated sea water, oil and carbonatic rocks by nonlinear vibrational spectroscopy

Não agendado

20m

Mestrado

Palestrante

Nicolau Barbosa Palma

Descrição

Nowadays there are many industries exploring the Brazilian “pre-salt” oil reservoirs to supply the future energy needs. However, both the oil and rock compositions are very different for these reservoirs and thereby new studies are needed to enhance the extraction with several strategies, including the low salinity water injection (LSWI). There is a large body of recent research in the literature about oil recovery by low salinity water injection spanning approximately the last 18 years.(1)Several coreflood experiments have shown that LSWI may, but not always, increase oil recovery compared with conventional seawater-flood. Here we propose a novel study with sum-frequency generation vibrational spectroscopy (SFG) to investigate the oil-water-rock interactions at the molecular level, aiming at the understanding of the role of water salinity on the rock wettability by water against oil, which could lead to improvement in the oil recovery. SFG spectroscopy is a nonlinear optical technique that can provide important information about the chemical nature of an interface by its vibrational spectrum, and about the average molecular orientation, with sub-monolayer sensitivity.(2)This technique relies on broken inversion symmetry, which naturally occurs at interfaces between two isotropic media such as gases, liquids and a large number of solids. Initially we performed a detailed study of the anisotropy and polarization dependence of the SFG spectrum for the clean calcite surface, as this will serve as a reference to understand future results on calcite interaction with water, ions and oil. Afterwards, studies of surface cleaning (up to the last monolayer) by low salinity water rinsing of the rock surfaces contaminated by stearic acid, condensed oil and “dead oil” have been performed. Similar strategies have been reported with organic solvents instead of low salinity water.(3)We found that neither diluted sea water nor pure water rinsing were able to completely remove the adsorbed oil from calcite, so that a water-wet surface is not likely to occur in carbonate reservoirs upon LSWI. This explains the modest effect of LSWI and low values of total oil recovery (~30%) for these “pre-salt” reservoirs. We plan to investigate different salt formulations for the injection water that may be capable of completely removing the organic contaminations from the rocks, thus enhancing oil recovery in these reservoirs.

Referências

1 SOHRABI, M. et al. Novel Insights into mechanisms of oil recovery by use of low-salinity-water injection. Society of Petroleum Engineers Journal, v. 22, p. 407-16,2017.doi.org/10.2118/172778-PA.
2 SHEN,Y. R.Surfaces probed by nonlinear optics. Surface Science, v. 299-300, p. 551–562, 1994.
3 ZHENG, Y. et al. Binary solvents with ethanol for effective bBitumen displacement at solvent/mineral interfaces. Energy Fuels, v. 29, n.7, p. 4222-4226, 2015.