硫酸钠溶液中方解石表面油膜脱附机理研究

摘要：本文重点研究油湿型方解石表面形成的过程和方解石表面油膜在SO42-作用下脱附的过程，从分子尺度探究油膜形成机理和SO42-作用机理。首先，为模拟碳酸盐岩储层实际而建立油湿型碳酸盐岩表面。范德华力和静电作用下油分子运动到方解石表面形成双层结构的油膜，方解石由水湿变为油湿。结果表明，与第二层相比，第一层排列更有序，结构更稳定，对储层润湿性影响更大。而后，研究方解石表面油膜在SO42-作用下脱附的过程和作用机理。方解石表面油膜的脱附可以分为两步：静电作用下水通道的形成；氢键作用下水膜的形成。最终，方解石表面由油湿变为水湿。研究表明：SO42-参与了方解石表面油膜脱附过程中重要的静电力作用和氢键作用，加速了水通道和水膜的形成，加速了方解石表面油膜的脱附，对储层润湿性影响较大。

Effect of Sulfate Ions on Oil Detachment from Calcite Surface

Abstract: This paper focus on the interaction of oil molecules and calcite surface in sodium sulfate solution and gives a schematic model of the oil detachment from calcite surface at molecular level. Firstly, a hydrophobic surface is constructed to simulate the oil-wet carbonate reservoirs. Under the dispersion force and the electrostatic interaction, the oil molecules migrate to the calcite surface and array in two layers. Compared with the second oil layer, the first one is more ordered and more stable, and has a greater effect on the reservoir wettability. Secondly, the mechanism of oil detachment from calcite surface in sodium sulphate solutions is studied. The detachment of oil from calcite surface can be divided into two steps: The formation of water channel under electrostatic interaction, and the formation of water film under H-bonding interaction. As a result, the calcite surface will be alter from oil-wet to water-wet. Results shows that the sulfate ions participate in the electrostatic interaction and H-bonding interaction, accelerate the formation of water channel and water film, and accelerate the oil detachment from calcite surface.