针对泡沫水泥浆在井筒内的密度变化的不确定性和复杂性导致固井设计困难等问题,通过试验测试现场1.10和1.20 g/cm3两种化学充氮泡沫水泥浆体系的密度变化,分析水泥石中泡沫尺寸变化特点以及固井液柱压力的变化,并进行11口井的现场应用.结果表明:泡沫水泥浆密度随温度和压力的变化符合Boltzmann函数;随着压力增加,水泥石中泡沫尺寸呈先急剧缩小、后变化较小的趋势.修正后的泡沫水泥浆密度计算公式对现场固井具有指导作用,固井优质率超过96%,为煤层气泡沫水泥固井提供技术支撑.%Foamed cement slurry has been used in well completion in coalbed methane development due to its low density, high intensity and good anti-channeling ability. However, the density of the foamed cement slurry in borehole is instable and can be greatly affected by the well depth. In this study, laboratory experiments were carried out with the two foamed slurries of differ-ent densities (1. 10 g/cm3 and 1. 20 g/cm3), in order to investigate the density variation of chemical and nitrogen-filled foamed cement slurry at different pressures ( i. e. well depths) . The bubbles size in the cement stone was measured using the micro-structure SEM diagrams. A cement displacement model using foamed cement slurry in coalbed methane wells was established in consideration of the cement displacement process and rheological properties of the cement slurry at different depth and pressure. The application of the model in 11 wells was conducted. The results show that the variation of the foamed cement slurry density with temperature and pressure is in accordance with the Boltzmann function. The bubbles size in the cement stone reduces sharply firstly with the increase of pressure and then its variation becomes smaller at high pressures. The qualification rate of the cementing process based on the model developed in this study can be 100% and the merit factor is more than 96%.
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