阳离子型絮凝剂与粘土矿物相互作用分子模拟

Interaction Studies Between Cationic Flocculants and Clay Minerals:Molecular Simulations

我国页岩气资源丰富,潜力巨大,为发展“低碳经济”提供了重要支撑。国内页岩气资源埋藏深,开采难度大,普遍存在水平段过长、储层裂缝发育严重、水敏性强、井眼不稳定等问题。与水基钻井液相比,油基钻井液在页岩气开发中具有更为优异抑制性、良好润滑性,在页岩气钻井中应用广泛,但面临有害固相难以去除难题。通过化学选择性絮凝技术实现油基钻井液有害固相清除有效手段之一,本文通过分子模拟研究了阳离子型絮凝剂与粘土矿物的相互作用,从分子尺度揭示了阳离子型絮凝剂絮凝带负电岩屑的选择性。计算发现:对于带负电岩屑成分具有较强的絮凝能力,对于不带电的岩屑成分絮凝能力差;阳离子型絮凝剂对于亲水性强的岩屑絮凝能力较差,且对于亲水性差的岩屑几乎没有絮凝能力;在有限浓度范围内絮凝剂浓度越大,絮凝效果越好;絮凝剂的性能随着环境温度的升高而下降。

China’s shale gas resources are abundant and have great potential,providing critical support for developing a“low-carbon economy”.Shale gas resources in China are deeply buried,difficult to exploit,long horizontal sections,severe reservoir fracture development,strong water sensitivity,and unstable boreholes.Compared with water-based drilling fluids,oil-based drilling fluids have better inhibition and good lubricity in shale gas development and are widely used in shale gas drilling but face difficulties in removing harmful solid phases.This work investigates the interaction between cationic flocculants and clay minerals through molecular simulation,which reveals the selectivity of cationic flocculants in flocculating negatively charged rock chips at the molecular scale.It founds that the cationic flocculant has a strong flocculation ability for negatively charged rock chips and a poor flocculation ability for uncharged rock chips;the cationic flocculant has a poor flocculation ability for highly hydrophilic rock chips and almost no flocculation ability for poorly hydrophilic rock chips;the higher the flocculant concentration in a limited concentration range,the better the flocculation effect;and the performance of the flocculant decreases with increasing ambient temperature.