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利用页岩气现场解吸仪对龙马溪组页岩岩心进行二阶解吸(一阶45℃,二阶110℃),计量解吸气量和恢复损失气量的同时,连续采集不同解吸时段的解吸气样品并进行组分和同位素测定。结果表明:页岩解吸气以CH_4为主,含有少量的C_2H_6、CO_2和N_2,一阶解吸阶段页岩吸附能力弱的CH_4含量较高,表明这一阶段解吸气以游离气为主;二阶解吸阶段页岩吸附能力强的C_2H_6和CO_2含量较高,表明此阶段解吸气中吸附气所占比例逐渐增高;解吸气随解吸时间增加烷烃气碳同位素组成逐渐变重,主要受气体在扩散过程中的“质量分馏效应”和“吸附—脱附”作用影响;整个解吸过程中解吸气烷烃气碳同位素均发生倒转且倒转程度随解吸时间增加逐渐变大,主要受解吸过程中甲烷碳同位素组成逐渐变重影响。
The shale core of Longmaxi Formation was desorbed by second-order desorption (45 ° C for first order and 110 ° C for second order) using a shale gas field desorber to measure the amount of desorbed gas and recover lost gas. Simultaneously, desorbed gas samples Components and isotope measurements were performed. The results show that the desorption gas of shale is dominated by CH 4 and contains a small amount of C_2H_6, CO_2 and N_2. The content of CH_4 with weak adsorption capacity of shale in the first desorption stage indicates that the desorbed gas is mainly free gas. The higher content of C 2 H 6 and CO 2 in the shale with the second-order desorption phase indicates that the proportion of adsorbed gas in the desorbed gas gradually increases at this stage. The desorption gas gradually increases in carbon isotope composition with increasing desorption time, The effect of gas mass fractionation effect and adsorption / desorption effect on gas diffusion process are also affected. During the whole desorption process, the carbon isotopes of the desorbed paraffins are reversed and the degree of inversion is gradually increased with the increase of desorption time, Methane carbon isotope composition is mainly influenced by the process of desorption.