防治固井环空油气窜流的智能材料体系的构建及应用

The annulus oil/gas migration of cement that arising in the first and second cementing interface and micro-cracks in cement paste is the most serious menace to wellbore integrity. Firstly, series of tough nanocomposite hydrogels with excellent adherence to inorganic interfaces can be prepared by combining with multivalent metal cross-linking mechanism and in-situ grafting copolymerization, in which water dispersible nano-clay and modified cellulose are used as grafting bone, and water-soluble monomers and adhesive functional monomer are employed as major structural units of grafting chains. Moreover, the toughening and strengthening mechanism of nanocomposite hydrogels can be clearly clarified based on the analysis of their structure and performance. Finally, the principle of adherence between hydrogel materials and inorganic interfaces and the law of their structural design can be indicated. .On the other hands, as key component that can induce the self-healing of cement micro-cracks, the oil/gas responsive gradient materials (including gradient particle size and gradient density of grafting polymer chains) can be synthesized by irradiating gradient rubber particles pre-swollen with long alkyl chains monomer and functional monomer in the interior of particles. During the structural design and preparation process of gradient materials, oil/gas responsive ability (especially in gas responsive ability) is the most important target. Then, oil/gas triggering self-healing cement can be obtained by blending oil/gas responsive gradient materials with cement. .In our investigation, several crucial engineering technical problems that induced by mixing hydrogel material/gradient material with cement are analyzed, including sharp increment of system consistency, the change of cement setting time, and rheological properties of cement paste, etc.. In sum, the annulus oil/gas migration of cement can be completely resolved by combining hydrogel material with gradient material, in which the hydrogel materials are utilized to block the oil/gas migration in the first and second cementing interface, and oil/gas triggering self-healing cement is used to repaired micro-cracks in solidified cement stone.

发生在固井Ⅰ、Ⅱ界面和水泥石内部微裂缝的油气环空窜流是破坏井筒完整性的重要威胁。研究首先采用纳米粘土和改性纤维素为骨架，以水溶性单体和粘附功能性单体为主要接枝链单元，通过接枝共聚合，结合金属离子交联制备高粘附强韧纳米复合水凝胶。在明确凝胶强韧机理的同时，阐述凝胶同无机界面间粘附机制及结构设计原则。同时通过具有梯度分布的橡胶粒子作为接枝中心，以长烷基链烯酯类单体和功能性单体为主要结构单元，利用单体浸润、辐照接枝的方法制备粒径及接枝链具有梯度分布的油气响应型梯度材料。重点探索材料结构设计与合成方法之间的关系，明晰材料结构与油气触发（特别是气触发）特性间的内在关联，并同水泥共混制成油气触发自修复水泥。针对材料同水泥复合体系可能存在的工程技术问题（如稠度、流变性等）进行分析并解决。最终采用凝胶（固井Ⅰ和Ⅱ界面）和自修复水泥（水泥内部微裂缝）进行油气封隔，解决环空窜流问题，为固井提供创新技术思维。

研究选用阴离子化疏水单体（丙烯酰胺基十一烷酸）同功能性水溶性单体在改性纤维素及水分散型纳米粘土骨架上进行接枝共聚，结合多价态金属配位交联技术制备新型纳米复合凝胶。智能凝胶具有良好交联可控性，交联初期（40-50min）内粘度较低、易于泵送，而后在1-4 h内快速交联。交联后凝胶材料具有良好机械强度，压缩强度大于20 Mpa。通过胺基单体同丙烯酸类单体共聚制备高效高分子界面粘附剂，粘附剂的使用可以有效提升凝胶同套管管壁金属界面之间的粘附性能，粘附力值从20 N最高可提升至130-140N。智能凝胶材料利用智能凝胶机械强度和界面粘附性能改善的协同效应，可以实现油气的高效封堵。40-90℃条件下，掺有凝胶的水泥复合体系抗压差能力约为6.9 MPa（5.36 cm×20 cm 标准失水桶模拟评价装置），且对水泥浆稠化性能无不良影响。.研究以非极性异戊橡胶为接枝骨架，利用接枝技术实现甲基丙烯酸十八酯、十一烯酸和苯乙烯单体在接枝骨架材料内部和表面的化学接枝，制备对油和小分子气态烃类物质具有响应特性的油气敏感梯度材料。进而利用单复配隔离技术结合，成功实现材料的合成和微粒子化，解决了材料团聚、二次粘结、储存稳定性差等缺点。油气敏感梯度材料对水泥石具有优异的修复效果，可以有效的修复水泥石裂缝间隙。与常规水泥石相比，可以提高裂缝性水泥石抗窜压差1-2个数量级。将气态烃类通入损伤的水泥石后，72 h后气体通过量可下降为0，这是目前国内市场同类产品所不具备的性能。油气敏感梯度材料的加入不会对水泥浆体系造成不良影响，水泥浆无促凝、过缓凝、及包芯等现象出现，且水泥稠化时间可调，具有良好的可应用性。 目前技术已进入大庆油田现场应用，产品成本仅为进口产品的1/4，在提升完井质量的同时，可大幅降低固井成本。