Salting-in/Salting-out Mechanism of Carbon Dioxide in Aqueous Electrolyte Solutions

The solvation of carbon dioxide in sea water plays an important role in the carbon circle and the world climate. The salting-out/salting-in mechanism of CO2 in electrolyte solutions still remains elusive at molecule level. The ability of ion salting-out/salting-in CO2 in electrolyte solution follows Hofmeister Series and the change of water mobility induced by salts can be predicted by the viscosity B-coefficients. In this work, the chemical potential of carbon dioxide and the dynamic properties of water in aqueous NaCl, KF and NaClO4 solutions are calculated and analyzed. According to the viscosity B-coefficients, NaClO4 （0.012） should salt out the carbon dioxide relative to in pure water, but the opposite effect is observed for it. Our simulation results suggest that the salting-in effect of NaClO4 is due to the strongly direct anion-CO2 interaction. The inconsistency between＂ Hofmeister Series and the viscosity B-coefficient suggests that it is not always right to indicate whether a salt belongs to salting-in or salting-out just from these properties of the salt solution in the absence of solute.

碳酸盐岩油藏智能水驱规律与机制

基于伊拉克Missan油田Mishrif组孔隙型碳酸盐岩油藏开展长岩心驱替试验、润湿角测定和界面张力测定试验,研究碳酸盐岩油藏智能水驱作用规律与机制。结果表明碳酸盐岩油藏智能水驱中岩石表面润湿性改善与油水相互作用改变协同作用提高采收率,其中润湿性改善影响较大。关键离子类型及质量浓度对润湿性及界面张力影响明显。其中Mg^(2+)和Ca^(2+)促进润湿性和界面张力的改变,随着其质量浓度增加,润湿角和界面张力均先减小后增大,存在最优质量浓度使得润湿角和界面张力最小;Mg^(2+)作用效果强于Ca^(2+)。SO^(2-)_(4)促进关键阳离子对润湿性的影响,抑制其对界面张力的影响,质量浓度越高作用效果越明显。碳酸盐岩油藏智能水驱中SO^(2-)_(4)优先吸附于方解石表面,促进关键阳离子发生多离子交换反应,造成润湿性的转变;随着溶液中离子类型及质量浓度的改变,吸附于油水界面的极性原油分子发生盐溶和盐析作用,影响油水相互作用。