(191f) Structures in Brines and Petroleum Fluids

Petroleum fluids and water/brine do not generally mix. However, due to various heteroatoms, some petroleum fluids and water/brine form water-in-oil and oil-in-water microemulsions. Water-in-oil emulsion is detrimental to displacement of oil by water/brine in permeable media in the subsurface. In this presentation, we  discuss the structures from mixing of an unusual petroleum fluid and water/brine in a vial. We also show results frond displacement of the oil by brine in porous media. The displacement tests show the strong effect of structures close to the interface. We then discuss our attempts to use functionalized molecules at 100 ppm concentration to change structures. There is profound effect of structure change in fluid displacement. In the rest of the presentation, we will discuss molecular modeling for prediction of the observed structures. Our molecular modeling includes: 1) specific ion effect on the self-assembly of ionic surfactants in brines, and 2) water-in-oil and oil-in-water emulsions. We will demonstrate that dispersion interaction of counter-ions through quantum mechanical calculations fully describe ion specificity. The presentation will conclude with  modeling of structures in water/oil surfactants.