深水钻井环境下有机土/石蜡油分散体系的胶体稳定性及其调控机制研究

Colloid stability in nonpolar media over a wide temperature range is an important scientific problem in the research area of oil based drilling fluids (OBM), and also one of the basic problems for soft mater science. The rheological properties of OBM are often out of control in the process of deepwater drilling due to the effect of low temperature, and the mechanism has not been fully elucidated. It is mostly believed that the change of rheological properties is related with the transformation of molecular conformation for the alkyl chain of the organoclay. In our preliminary work, polyisobutylenesuccinimide (PIBSI) was found to be a good additive to control the colloid stability of organoclay suspensions in mineral oil at low temperature. Moreover, some quaternary ammonium surfactants could be used to organically modify Na-montmorillonite in nonpolar media at high temperature conditions of the well bottom. So we infer that changes of the rheological parameters are the results of the transformation of molecular conformation for the alkyl chain of the organoclay and the increase of the actual concentration for organoclay. In order to confirm this hypothesis, we will work on different organoclays with iso-alkyl chain and n-alkyl chain modifiers (quaternary ammonium surfactants), and to explain the mechanism of the viscosity increase for OBM at low temperature and to explore the feasibility of in situ formation of OBM in deepwater drilling conditions.. The research results of this project will be helpful to provide theoretical guidance for the practical application of the non-aqueous colloidal system in harsh environmental conditions like low temperature and high temperature. Non-aqueous dispersion remained relatively stable rheological properties over wide temperature range could be used for deep-water oil and gas exploration, and has great significance to ensure that offshore oil industry will become the backbone of our national energy.

宽温度范围内非极性介质中的胶体稳定性是油基钻井液研究的重要科学问题，也是软物质科学的基本问题之一。海上钻井中深海低温造成的钻井液流变学性能失稳机制尚未阐明，多认为与粘土粒子表面烷基链构象随温度而变有关。前期研究中发现聚异丁烯琥珀酰亚胺类有利于调控低温胶体稳定性，而在模拟井底的相对高温下非极性烷烃中水溶性季铵盐类可以使钠土有机改性。我们推测深海低温所致的钻井液流变学参数增加不仅与有机土表面烷基链构象随温度而变有关，也与有机土实际浓度增加有关。为证实这一假说，将通过异构烷烃链与正构烷烃链的对比，阐明非极性胶体低温增稠的机制，并探索典型深水钻井环境下原位形成油基钻井液的可行性。. 本课题将为高、低温等苛刻环境条件下非水胶体体系实际应用提供理论指导，宽温度范围内流变学性能稳定的非水体系可望用于深水油气开采，对保障海洋石油顺利接替陆地成为国家能源支柱具有重要意义。

宽温度范围内非极性介质中的胶体稳定性是油基钻井液领域的重要科学问题。海上钻井中低温造成的钻井液流变学性能失稳机制尚未阐明。本项目研究了烷烃类油相中常规有机土的胶体稳定性及影响因素，模拟深水环境下所钻地层钠土在烷烃类油相中的分散性，进行了有机土/石蜡油分散体系的原位制备。研究发现随着改性剂加量的增大，依次发生插层反应、离子交换和物理吸附。当加量低于1.2CEC时，有机土的分散稳定性逐渐增强，当加量高于1.2CEC后，有机土颗粒的表面重新变得亲水，分散稳定性降低。兼具强吸附基团和不饱和尾链的表面活性剂可能更有利于提高分散稳定性，而羧基和酯基均不具有强吸附性特点。表面活性剂在促进有机土分散的同时会进入有机土的层间，增大层间距。油相中静电作用可能对有机土的分散稳定性有一定贡献。表面活性剂和有机土阳离子改性剂之间存在竞争吸附，竞争吸附的程度对体系的高温稳定性影响显著。原位改性的方法可以制备得到分散性改善的有机土，并且具有稳定乳液的能力，但是表面物理吸附的改性剂分子的含量差异导致原位有机土和水法有机土的性能差异。本课题将为苛刻环境条件下非水胶体体系实际应用提供理论指导，对国家能源领域具有重要意义。