压差激活密封剂的微缺陷自适应修复行为及机理

Self-adaptive repair behavior and mechanism of micro-defects of differential pressure activated sealant

压差激活密封剂是一种适用于油气井管柱微泄漏快速、安全修复的新技术,目前关于该体系的应用及理论研究报道较少。采用室内实验、结构表征、理论分析及数值模拟相结合的方法,开展了压差激活密封剂制备、微形貌检测、密封性能评价、压差激活机理分析、自适应密封动力学模拟等方面的应用基础研究。研究结果显示:制备的压差激活密封剂是一种多分散相体系,分散相为水化胶粒,具有微米级层状体型结构,是确保压差激活密封性能的关键组分;在5~15 MPa压差范围内,密封剂能够在150 s内穿透丝扣滑脱及漏缝孔隙形成韧性固体屏障,有效封堵不同类型微缺陷;基于水化胶粒的分子形态与稳定性间关系,提出了压差激活密封流体的液-固转化构效假设,建立了漏点压差的自适应密封力学-化学耦合模型;分析了复合液滴在环境液体压差下的受力状态,采用LES-VOF方法模拟了复合液滴在环境液体射流场的变形与破碎动力学行为,研究了水化胶粒的去水化动态演化过程,表层水化膜的射流变形显著大于胶核,可发生振荡破裂使胶核活化聚结,进而充填固化封堵微缺陷。模拟结果与理论分析基本一致,为进一步研究压差激活密封剂提供了理论支持。

Differential pressure activated sealant is a new technology suitable for rapid and safe repair of micro leakage in tubular strings in oil and gas wells. There are few reports on the application and theoretical research of this system. Based on a combination of laboratory test, structural characterization, theoretical analysis and numerical simulation, this paper systematically carries out basic research for application in terms of preparation, micro-morphology detection, sealing property evaluation, mechanism analysis of differential pressure activation, as well as dynamics simulation of adaptive sealing. The research results show that the prepared differential pressure activated sealant is a polydisperse system;the dispersed phase is hydrated colloidal particles with micron-level layered physical conformation, which is a key component to ensure the sealing property of differential pressure activated sealant. Within the pressure differential range of 5-15 MPa, in 150 s, the sealant can penetrate the threaded dropout and leaky pores to form a tough solid barrier, which can effectively plug different types of micro-defects. Based on the relationship between the molecular morphology and stability of the hydrated colloidal particles, this paper proposes a hypothesis on the structure effect of liquid-solid transformation of differential pressure activated sealed fluid, and establishes an adaptive sealing mechanics-chemical coupling model of the differential pressure at the leaking point. Further, it analyzes the stress state of composite droplet under the differential pressure of environmental liquid, uses the LES-VOF method to simulate the dynamic behaviors of deformation and breaking of the composite droplet in the jet flow field of environmental liquid, explores the dynamic evolution process of the dehydration of hydrated colloidal particles. The jet deformation on the surface hydration shell is significantly larger than that of the colloidal nucleus, and thus wave breaking occurs, resulting in the elimination of surface hydration shell and the activation of colloidal nucleus, which will facilitate filling blockage of micro-defects. The simulation results are basically consistent with the theoretical analysis, which provides a theoretical support for further researches on the differential pressure activated sealant.