考虑含水和多组分气体的页岩气含气量预测模型
Prediction model of shale gas content with the consideration of moisture and multicomponent gas
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摘要: 基于体积法建立页岩气含气量预测模型,含气量包括吸附气量和游离气量,在计算吸附气量时考虑了页岩矿物组成、温度、压力、水分和非甲烷多组分气体,在计算游离气量时考虑了吸附相体积,最终采用涪陵焦石坝地区焦页1井页岩现场解吸数据验证模型。结果表明,当考虑吸附相体积时,含气量模型计算值与现场解吸数据较吻合,当不考虑吸附相体积时,页岩含气量被高估27%~38%;水分对页岩含气量的影响较小;多组分气体不仅改变页岩含气量,也改变页岩气的赋存状态,不考虑多组分气体将高估目标区域含气量5. 6%~31. 8%。所建含气量模型精确性依赖于室内岩芯实验结果,未来应进一步开展含水页岩对多组分气体吸附实验研究,准确计算页岩气含气量。Abstract: A prediction model of shale gas content was established based on the volumetric method. The total gas con- tent of shale includes gas in the adsorbed phase and free phase. The amount of gas in the adsorbed phase was calculat- ed with the consideration of mineral composition of shale,temperature,pressure,moisture and non-methane gas,and in the calculation of gas amount in the free phase the adsorbed phase volume was con-sidered. The model validation was conducted with the experimental data of in-situ desorption of JY-1 well in Fuling Jiaoshiba area. The results show that when the adsorbed phase volume is considered,the gas content calculated by the model is in good agreement with the field desorption data. However,when the adsorbed phase volume is not considered,the gas content is overestimated by 27% -38% . Moisture has little effect on the gas content of shale. Multicomponent gas not only changes the gas content of shale,but also changes the occurrence state of shale gas. The gas content will be overestimated by 5. 6% -31. 8%without the consideration of multicomponent gas. The accuracy of the model greatly depends on the results of indoor ex- periments. To obtain an accurate shale gas content,a further study of adsorption experiments of multicomponent gas on moisture-equilibrated shale should be carried out in the future study.