咪唑类离子液体对水基钻井液抑制性的影响及机理

Effect of an ionic liquid with an imidazole cation on shale inhibitive property in water-based drilling fluids and its mechanism

油气钻井过程中泥页岩不稳定主要是由于泥页岩的水化作用造成。本文采用页岩滚动回收率法、毛细管吸入时间法和粒度分析法3种方法,与传统抑制剂KCl和新型抑制剂聚胺作对比,评价了离子液体RIL作为抑制剂对水基钻井液抑制性能的影响。结果表明高温作用下低浓度(质量分数0.05%)的离子液体RIL有着优异的抑制黏土膨胀和分散的能力,其抑制效果优于5%KCl,与2%聚胺相当;同时低浓度的离子液体RIL可以改善水基钻井液的高温流变性而不会使钻井液的滤失性变差。通过接触角和热稳定性测试分析了其抑制机理。离子液体RIL改性后的Na蒙脱土润湿性从亲水性向疏水性转变,可以阻止水分子进入Na蒙脱土的层间结构从而抑制Na蒙脱土的膨胀和分散。低浓度的离子液体RIL改性后的钠蒙脱土具有更好的热稳定性,可以提高高温作用下水基钻井液的抑制性。

Shale instability is mainly induced by the hydration of shale in the drilling of oil and gas.An ionic liquid,as an inhibitor,was evaluated by hot-rolling recovery,capillary suction time,and particle size distribution tests.The results showed thatat high temperature the ionic liquid(RIL)with very low concentration had superior capacity to inhibit clay swelling and dispersing.It performed better than5%KCl,a conventional inhibitor,and had similar performance of2%polyether diamine,a novel inhibitor.RIL at very low concentration can improve the rheology of water-based drilling fluids and would not affectthe filtration performance at high temperature.The mechanism of inhibiting was investigated via contact angle tests and thermogravimetric analyses.It is found that RIL strengthened lipophilicity of Na-MMT,which prohibited water from ingress.The thermal stability of Na-MMT was greatly improved when Na-MMT was modified with lower concentration of RIL,leading to the excellent inhibition of ILB at high temperatures.