Abstract
Further enhancement of crude oil recovery in the enhanced recovery stage from calcite oil wells is a major global challenge for oil industry. Experimental results suggest that ions present in sea water, also called smart water, have a significant influence on the wettability alteration (less oil wet) of calcite surface. In this paper, by utilizing Density Functional Theory (DFT) and Quantum Molecular Dynamics (QMD) simulations, we investigate the effect of additive ions of sea water in oil recovery by using acetic acid as a model compound of crude oil molecules. We find that Na+ ions precipitate to the calcite surface and form Na acetate. The binding energy of Na acetate is larger than original oil molecule (acetic acid), which reduces oil recovery. On the other hand, Mg2+ and {rm{S}}{{rm{O}}}_{4}^{2-} ions can also reach to the calcite surface in proximity and modify the calcite surface. The binding energy of oil molecule on modified calcite surface is smaller than on pure calcite surface, which enhances oil recovery. Our results might help in understanding interaction among oil, water and additives ions of smart water for further experimental investigations.
Highlights
Further enhancement of crude oil recovery in the enhanced recovery stage from calcite oil wells is a major global challenge for oil industry
In the enhanced recovery stage, when sea water is injected in the oil wells, contains of active sea water ions Mg2+, Ca2+, and SO24− affect the characteristics of wettability alteration of calcite surface that enhance the efficiency of crude oil recovery[2,3,4]
We use quantum mechanical calculations based on density functional theory (DFT) and Quantum Molecular Dynamics (QMD) simulations and find that the binding energy of acetic acid is larger than water molecule on pure calcite surface, which confirms that the calcite surface is oil wet
Summary
Further enhancement of crude oil recovery in the enhanced recovery stage from calcite oil wells is a major global challenge for oil industry. We further find that Na+ ion reach to the calcite surface as a precipitate and form Na acetate that has larger binding energy than acetic acid This provides an explanation for the experimental observations by Fathi et al that injecting low salinity water (removing some of Na+ and Cl− ions from sea water) in oil wells enhances oil recovery. As discussed by authors in refs[2,4], oil recovery is enhanced when Mg2+ ion of sea water replaces Ca2+ of calcite and SO24− ion of sea water replaces CO32− of calcite In this case, on modified calcite.MgSO4 surface, the binding energy of acetic acid decreases and water molecule increases. Such interplay causes an enhancement of caCbrauo2du+etitoowniliscreewcthohevenecroMynogcne2+nmtrreoaptdiloiafniceeodsfcCSaOalc224+i−t.eaH.MnedgnSacbOeo,4iunstuftrohfuaisrcepti.amIpneessretwhaeewcfaiontnedrc,eatnnhteraacdtoidonintcieoonnftCarlaatr2io+ol.neToohfferMMe gagr22+e+
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