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页岩含气量对页岩气田储量计算至关重要,直接关系到页岩气的产量、递减规律等。页岩气以游离气和吸附气形式赋存,有重量法等温吸附、容量法等温吸附、现场含气量测试等不同方法测试吸附气、游离气。通过测试页岩气降压解吸过程中气体体积变化来测量吸附气量,首次建立了同时测试页岩吸附气、游离气的方法。该方法采用柱状页岩岩心,模拟不同温度、压力、含水、真实孔隙结构等条件,消除了等温吸附曲线的负吸附异常;分析了有机质含量、压力、温度、含水、气体组成等因素对页岩吸附量的影响。实验结果表明,页岩的甲烷吸附量随压力增加而增加,压力大于12MPa后达到吸附/解吸动态平衡,吸附量不再增加;有机质含量TOC增加时吸附量增加;温度增加时吸附量降低;页岩含水后吸附量降低;甲烷吸附量高于氮气吸附量;焦石坝龙马溪组主力层页岩在温度20℃、压力30MPa下页岩气吸附气量介于1.8~3.1m~3/t之间,总含气量介于5.1~6.5m~3/t之间,吸附气占总气量40%左右。
Shale gas content is crucial for the calculation of shale gas reserves and is directly related to shale gas production and decreasing law. Shale gas exists in the form of free gas and adsorbed gas. There are different methods such as isothermal adsorption by gravimetric method, isothermal adsorption by volumetric method, and gas content measurement on site, and other methods to test adsorbed gas and free gas. By measuring the gas volume change during the desorption process of shale gas to measure the amount of adsorbed gas, a method for simultaneous testing of adsorbed gas and free gas in shale gas was established for the first time. The method uses columnar shale cores to simulate the conditions of different temperature, pressure, water and real pore structure, and eliminates the negative adsorption anomalies of isothermal adsorption curves. The influence of organic matter content, pressure, temperature, water content and gas composition on shale Effect of adsorption amount. The experimental results show that the adsorption amount of methane in shale increases with the increase of pressure, and reaches the equilibrium of adsorption / desorption when the pressure is higher than 12 MPa. The adsorption amount does not increase any more. The adsorption amount increases when the content of organic matter increases, and decreases when the temperature increases. The amount of adsorbed methane is higher than that of nitrogen; the shale of the main strata of Longmaxi Formation in Jishi Rock Dam is between 1.8 ~ 3.1m ~ 3 / t at a temperature of 20 ℃ and a pressure of 30MPa Between the total gas content is between 5.1 ~ 6.5m ~ 3 / t, adsorption gas accounts for about 40% of the total gas.