四川盆地及周缘页岩气赋存方式展布特征研究

Study on the distribution characteristics of occurrence modes of shale gas in the Sichuan Basin and its periphery

为了厘清四川盆地页岩气赋存方式的展布特征,针对四川盆地及其周缘各层系中页岩气含气量数值差别较大,页岩气赋存方式不同的问题,对四川盆地及周缘的20多口已钻探的页岩气井开展了现场含气量解吸数据、气体组分数据以及同位素数据等方面的分析工作。结果表明,该区页岩气井的解吸速率曲线、气体组分变化曲线及同位素变化曲线均存在一个峰值变化的拐点,这个拐点是赋存方式变化的一个标志。在解吸速率曲线上使用速率峰值拐点法分别计算吸附气和游离气含量以判断页岩气的赋存方式,发现四川盆地内部页岩气赋存方式以游离气为主,盆地外部以吸附气为主,且游离气含量从盆内向盆外有降低趋势的分布特征。该研究成果对四川盆地页岩气的勘探工作具有一定指导意义。

In order to clarify the distribution characteristics of occurrence mode of shale gas in Sichuan Basin, in view of the problems of the large differences in the gas content of shale gas and different shale gas occurrence modes in the Sichuan Basin and its periphery, research on more than 20 wells of shale gas that have been drilled in the Sichuan Basin and its periphery, the analysis of gas content desorption data, gas composition data and isotope data was carried out. The results show that the desorption rate curve, gas composition change curve and isotope change curve of shale gas wells in this area, all have an inflection point of peak change, which is a sign of the change of occurrence mode. On the desorption rate curve, the rate peak inflection point method is used to calculate the adsorbed gas and free gas content to determine the occurrence mode of shale gas. It is found that the occurrence mode of shale gas in the Sichuan Basin is mainly free gas, and the outside of the basin is mainly adsorbed gas, and the distribution of free gas content tends to decrease from the inside to the outside of the basin.The research results have certain guiding significance for the exploration of shale gas in the Sichuan Basin.