自修复固井前置液自修复机理

Study on Self-healing Mechanism of Self-healing Prepad Fluid for Well Cementing

将水灰比为0.44的油井水泥净浆灌入钢管中养护,然后切片并造缝,制作成钢管切片样品,放入清水和固井自修复前置液中浸泡养护,通过测试抗窜强度和对比分析样品微观结构与水化产物组成特征,研究固井自修复前置液的自修复机理。运用X-射线衍射仪对样品的物相组成进行分析,利用热重(TG/TGA)方法测定样品中Ca(OH)2含量,采用压汞仪对样品的孔结构变化进行分析,最后利用环境扫描显微镜对样品的微观形貌进行观测,并对测试样品的微区进行X射线能谱定性、定量分析。研究结果表明,GSN自修复前置液和NMFSJ自修复前置液能够渗透到样品的微裂缝中,与裂缝附近的氢氧化钙和未水化产物发生水化反应,形成硅酸钙结晶或水化硅酸钙凝胶和碱式碳酸钙等水化产物,自动修复样品的微裂缝;NMFSJ自修复前置液还能够渗透到样品固化体本体的孔隙中,激活水化反应;另外其有一部分组分不参与直接生成结晶体,而是催化水泥环中未水化的水泥颗粒水化。

Cylindrical sliced set cement slurry sample(water cement ratio of 0.44) aged in steel pipe were placed in clear water and self-healing prepad fluid for ageing. Using X-ray instrument, the aged slice samples were tested for their anti-channeling capacity and analyzed for their micro structures and composition of hydration product. The Ca(OH)2 content of the samples were measured with TG/TGA method. Using mercury porosimeter, the pore structure of the samples were analyzed. ESEM was finally used to survey the microscopic topography. It was concluded that the prepad fluid can infiltrate into the micro-fractures of the samples, where the prepad fluid reacted with the Ca(OH)2 and nonhydrated cement existed there to form hydrated product, thus realizing self-healing. The prepad fluid also infiltrate into the pores of the main body of the samples to activate hydration reaction, producing hydrated calcium silicate gel which can fill the pores in the main body, thus strengthening the main body and enhancing its ability to counter filtration and damage. The study is of importance in the application of self-healing prepad fluid, and for the success of well cementing.