关键词: 油基泥浆, 储层, 润湿反转, 无机离子, 表面活性剂

Abstract: The synergetic effect of inorganic ions, such as Na⁺ and Ca²⁺ present in the formation water, and in the filtrates of oil-based muds on the wettability of sandstone cores has been studied.The Amott/USBM method was used to measure wettability changes.The water wettbility of pore surface of sandstone cores reduces (or oil wetability rises) with the increase in ion concentrations.Under the condition of the same concentration, the effect of multi valentions greatly surpasses the effect of monovalent ions, The effect of inorganic ions on the wettability of sandstone is shown mainly for system in which both inorganic ions and anionic surfactants are present.In this system, the inorganic ions tend to reduce the stability of the thin water film existed between the rock and oil because they strongly affect the surface charges on the rock surfaces and water/oil interfaces.Thus, they will cause an increase in the amount of surfactants adsorbed on the sandstone surface, and a change in the configurations of the surfactants as well.The inorganic ions have only a slight effect on the wetting behavior of cationic surfactants.