水基凝胶微球的制备及在堵漏中的应用

采用反相乳液聚合法，合成了水基钻井液用凝胶微球。采用电子显微镜、红外光谱、热重分析、粒径分析，对合成的凝胶微球的组成、形貌及热稳定性进行了表征。结果显示制备出的凝胶微球呈现微米级球形结构，尺寸在4.5～68 μm范围内，初始热分解温度为150 ℃。同时考察了乳化剂加量、搅拌、油水比对凝胶微球粒径的影响，评价了凝胶微球的堵漏性能。结果表明，反应条件对凝胶微球尺寸有较大影响，随着乳化剂加量的增大，凝胶微球的平均粒径减小；适当搅拌会促进乳状液的稳定，合成得到的凝胶微球的粒径较小；增大油水比会导致凝胶微球的平均粒径减小。通过堵漏实验可知，凝胶微球有良好的封堵效果，其中乳化剂加量为4%，油水比为7∶3，不搅拌条件下制备的凝胶微球平均粒径为45.1 μm，是封堵效果最好的凝胶微球。 

Preparation of Gel Microspheres for Water Based Drilling Fluids and Its Application in Lost Circulation Control

A gel microsphere lost circulation material (LCM) has been synthesized through inverse emulsion polymerization. The composition, morphology and thermal stability of the gel microspheres were characterized using electron microscope, IR spectroscopy, thermogravimetric analysis and particle size analysis. It was found in these studies that the gel microspheres are in a micron spherical structure, with their particle sizes ranging from 4.5 μm to 68 μm. The initial thermal decomposition temperature of the gel microspheres is 150 ℃. The effects of the amount of emulsifier added into the reaction, mixing of the reactants and oil/water ratio on the particle size of the gel microspheres were examined and the performance of the gel microspheres evaluated. The results of the examination showed that the reaction conditions have a great influence on the sizes of the gel microspheres; as the amount of emulsifier increases, the average diameter of the gel microspheres decreases. Proper stirring promotes the stability of the emulsion, thereby reducing the particle sizes of the gel microspheres. An increase in oil/water ratio decreases the average particle size of the gel microspheres. The LCM evaluation test results showed that the gel microspheres have a good lost circulation control effect; gel microspheres, which are produced at 4% emulsifier, oil/water ratio of 7∶3 and without stirring have average particle size of 45.1 μm, and are the best LCM.