油井水泥膨胀性自修复剂机理研究

固井水泥石微裂缝严重影响层间封隔完整性、缩短油气井寿命，水泥石微裂缝自修复技术是解决这一问题的有效途径。然而，目前对于膨胀性自修复剂机理研究较少，缺乏理论支撑。提出利用填充系数评价水泥石微裂缝自修复效果，建立了膨胀性自修复剂封堵水泥石微裂缝的数学模型，明确了影响水泥石微裂缝自修复效果的主要影响因素。此外，根据巴西劈裂试验，设计了一种简单的、能够定量模拟水泥石微裂缝的方法。利用水泥石微裂缝自封堵评价仪，对自选择修复材料进行自修复评价实验，验证了自修复效果与自修复剂吸液倍率、加量、微裂缝宽度的关系。结果显示，自选择修复材料的遇水自修复临界填充系数为0.473，最大可封堵234 μm微裂缝；遇油自修复临界填充系数为0.490，最大可封堵150μm微裂缝。研究结果为膨胀性自修复剂实现固井水泥石微裂缝自修复奠定了理论基础。 

Study on the Mechanism of Expansive Self-Healing Additives for Oil Well Cement

Micro-fractures developed inside set cement in an oil or gas well seriously affect the isolation integrity between borehole wall and casing string, thereby shortening the life of the well. Self-healing of micro-fractures in set cement is an effective way of resolving this problem. Studies on the mechanisms of expandable self-healing agents have seldom been conducted until now and the self-healing mechanisms lack theoretical support. This paper presents fill factor as an indicator to evaluate the self-healing of set cement, builds a mathematical model describing the sealing of micro-fractures in set cement by expandable self-healing agents, and explains main factors affecting the self-healing of set cement. A simple quantitative method for simulating the micro-fractures developed in set cement was designed based on Brazilian disk test. Several self-selective healing agents were evaluated for their self-healing ability using set cement micro-fracture self-sealing evaluation device, verifying the relationship between the self-healing effect and the amount of liquid adsorbed by self-healing agent, concentration of self-healing agent, as well as the width of micro-fracture. It was found that the selfselective healing agent, when mixed with water, had critical self-healing fill factor of 0.473, and the healing agent is, at most, able to seal fractures of 234 μm in width. The self-selective healing agent when mixed with oil, had critical self-healing fill factor of 0.490, and it is, at most, able to seal fractures of 150 μm in width. The studying results lay a theoretical foundation for the use of expandable self-healing agents in sealing micro-fractures developed inside set cement.