注入水成分对油藏中液固界面Zeta电位的影响

Effect of Injected Water Composition on Zeta Potential of Liquid - Solid Interface in Reservoir

摘要:

为了研究低矿化度水成分对油藏中岩石和原油表面带电量、润湿性、油膜脱附量的影响规律及三者之间的关系，配制离子类型、离子浓度、溶液pH不同的低矿化度水并分别将其与模拟岩石和原油样品混合后测定其Zeta电位值、与含油岩心切片接触测其表面的润湿角、与含油岩石颗粒混合测其表面油膜脱附量。实验结果表明，Na 、Ca2 和Mg2 离子溶液对原油和岩石表面带电量的影响主要取决于离子价态，二价离子对其带负电量影响更大。同种离子的溶液随着浓度的增加负电量减少。pH升高对带电量的影响与溶液所含离子的价态和水解性有关，二价Ca2 、Mg2 离子对应的溶液所测得的带电量比一价离子溶液低，且随着pH的增加其带电量呈现先增大后减小的趋势，这种趋势与一价Na 离子不同。实验得到的润湿角和油膜脱附量数据表明，低矿化度水成分变化对原油和岩石表面带电量的影响规律与其对界面润湿角和油膜脱附量的影响规律一致；当油藏液固界面Zeta电位值的绝对值减小时，其接触角增大、油膜脱附量减少。

Abstract:

In order to study the effect of low-salinity water composition on the surface charge, wettability and oil film desorption capacity of rock and crude oil as well as the relationship between them. low-salinity water prepared by different ions in varied ionic concentrations and pH values were mixed with simulated rocks and crude oil samples to measure the Zeta potential value，respectively. The solid/brine water/crude oil three-phase contact angle was measured on the man-made core slices. The oil film desorption capacity on the surface of rock particles mixed with brine water was measured. The experiments showed that the effect of Na , Ca2 and Mg2 ions on the surface charge of crude oil and rock are mainly depended on the ionic valence state. The divalent ions have a more significant influence on the negative charge. The negative charge detected in solutions of the same ions decreases with the increase of the concentration of ions. The effect of increasing pH on negative charge is related to the ionic valence and the dehydration of solutions. The negative charge of the divalent Ca2 or Mg2 ion is less than that of the monovalent ion solution, and displayed a trend that the negative charge increased initially and then decreased，which differs from the latter . The results indicated that the effect of low-salinity water on the surface charge of crude oil and rock is consistent with the influence on the interfacial contact angle and the oil film desorption capacity. As the absolute value of the Zeta potential decreases, the interfacial contact angle increases and the oil film desorption decreases.