钻井液氟碳润湿反转剂作用机理的量子化学研究

针对低孔低渗储层钻井过程中极易受到水锁损害的特点,对氟碳类润湿反转剂的作用机理进行量子化学研究。建立了两种模拟砂岩的原子簇模型。利用量子化学从头计算法(HF-3-21G)计算了两种不同分子结构的氟碳润湿反转剂与砂岩模型的相互作用关系;并计算了水分子与砂岩以及润湿反转剂模型的相互作用关系。结果表明,两种氟碳润湿反转剂均倾向于以HOMO轨道和砂岩的LUMO轨道发生结合,结合后氟碳链官能团向外伸展,对内部结构及砂岩起到了屏蔽保护的作用;水分子在砂岩模型表面的吸附势阱绝对值大约在40 kJ·mol-1左右,为氢键力作用,在氟碳润湿反转剂模型表面的吸附势阱均绝对值小于10 kJ·mol-1甚至更小,为物理凝聚;此外,水分子在润湿反转剂模型表面的吸附距离也远大于砂岩模型表面,说明钻井液与砂岩的接触过程中,氟碳润湿反转剂倾向于以不含氟官能团吸附在砂岩表面,且吸附后砂岩表面与水分子的作用力明显减弱。

Quantum Chemical Study of Fluorocarbon Wettability Reversal Additives in Drilling Fluid

In order to address the problems of water block formation damage in low porosity and permeability reservoirs, the mechanism of fluorocarbon wettability reversal additives has been studied theoretically with quantum chemical method. Based on the cluster models of sandstone, the relation between sandstone and wettability reversal additive has been studied by the ab initio method (HF-3-21G), and the relation between water and different surfaces has also been investigated, including adsorption potential well and distance. The HOMO (highest occupied molecular orbital) of wettability reversal additives tends to adsorb on the LUMO (lower occupied molecular orbital) of sandstone. The adsorption potential well of water on sandstone is about 40 kJ?mol-1 which belongs to hydrogen bonds, and less than 10 kJ?mol-1 on wettability reversal additives which belongs to physical adsorption.