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页岩气与煤层气的等温吸附特征既有相似性,又存在较大差异。目前页岩气等温吸附测试仍沿用煤层气相关测试规范,没有针对页岩气的等温吸附实验仪器。泥页岩储层等温吸附实验中普遍存在等温吸附曲线异常的现象,因此对常见的泥页岩储层等温吸附曲线异常现象进行了归纳,分析了导致异常的原因,并提出相应的改进建议。研究结果表明,在高压段,地层条件下由于甲烷处于超临界状态,吸附态气体不发生液化凝聚,造成测试曲线明显偏离Langmuir等温吸附模型,且特征参数失真,因而基于凝聚机理的Langmuir等温吸附模型在高压段不再适用,但该异常可通过模型改进或实验数据校正来消除;在低压段,通常由于泥页岩储层的吸附气含量远小于煤层气,而测试仪器精度难以满足要求,或泥页岩储层粘土矿物含量较高,在预处理中与水发生反应而影响吸附特征,可尝试通过增加测试样品量、预处理后充分脱水等方法来减少异常现象的发生。
The isothermal adsorption characteristics of shale gas and coalbed methane have similarities and big differences. At present, the shale gas isothermal adsorption test still follows the CBM-related test norms and there is no isothermal adsorption experimental instrument for shale gas. Absorption isotherms are common in the isothermal adsorption experiments of shale reservoirs. Therefore, the common anomalous adsorption isotherms of shale reservoirs are summarized. The causes of the anomalies are analyzed and corresponding suggestions for improvement are proposed. The results show that due to the supercritical methane in the high pressure section and the formation, the adsorbed gas does not liquefy and agglomerate, causing the test curve to deviate from the Langmuir isothermal adsorption model and the characteristic parameters are distorted. Therefore, the Langmuir Isothermal adsorption model based on the aggregation mechanism However, this anomaly can be eliminated through model improvement or experimental data correction. In the low pressure section, the accuracy of the test instrument usually can not meet the requirement because the adsorbed gas content of the shale reservoir is much smaller than the CBM. Mud shale reservoirs have a high content of clay minerals and react with water during pretreatment to affect the adsorption characteristics. Try to reduce the anomalies by increasing the amount of test samples and fully dehydrating after pretreatment.