分子动力学模拟研究方解石表面润湿性反转机理

利用分子动力学模拟技术从分子尺度探究方解石表面润湿性反转机理.首先,研究方解石表面润湿性反转过程;而后,从原油分子-方解石表面与原油分子-原油分子/水分子相互作用两个方面系统揭示方解石表面润湿性反转机理.结果:(1)水分子能够驱离方解石表面弱吸附的非极性分子造成润湿性的改变,但不能驱离强吸附的极性分子使润湿性反转难以实现;(2)原油分子极性越强与方解石表面相互作用越强,极性分子与方解石表面之间主要为静电力,非极性分子与方解石表面之间主要为范德华力;(3)原油分子极性越相近分子之间的相互作用越强,分子极性相差越大分子之间的相互作用越弱.非极性分子之间主要是范德华力,极性分子之间主要是静电力;(4)原油分子在方解石表面和水分子的共同作用下形成乙酸-吡啶-水-甲苯-己烷的稳定吸附序列.本研究为靶向提高采收率技术的设计与应用提供理论基础.

Wettability alteration mechanism of calcite surface: Molecular dynamics simulation study

Molecular dynamic simulation is used to study the wettability alteration mechanism of calcite surface in molecular scale. Firstly, the wettability alteration process is investigated with molecular dynamic simulation. Then, the wettability alteration mechanism is explained in two directions, including crude oil molecules-calcite surface and crude oil molecules-crude oil/water molecules interactions. Results show that (1) water can displace the weaker absorbed apolar crude oil molecules and result in the wettability alteration, while it can not displace the stronger absorbed polar molecules and calcite surface stay oil-wet; (2) The stronger the polarity of crude oil molecule is, the stronger the interaction between crude oil molecule and calcite surface is. Electrostatic force contribute most in polar molecule-calcite surface interactions, while van der Waals force is more important in non-polar molecule-calcite surface interactions; (3) The smaller the polarity difference of the crude oil molecules, the stronger the interaction among molecules, vice versa. The van der Waals force contributes most among non-polar molecules interactions; the electrostatic force play a major role among polar molecules interactions; (4) The stable adsorption sequence of acetic acid-pyridine-water-toluene-hexane is formed with the combination influence of water molecules and calcite surfaces. This study provides a theoretical basis for the design and application of targeted enhanced oil recovery technology.