四川盆地涪陵地区五峰—龙马溪组解吸气特征及影响因素分析

Characteristics and influencing factors of desorption gas in Wufeng-Longmaxi formations in Fuling area,Sichuan Basin

页岩气主要以吸附气和游离气的方式赋存在页岩中,通过对页岩气的解吸气特征及影响因素分析,可以更好地指导页岩气的勘探开发。通过对四川盆地涪陵地区五峰—龙马溪组页岩气的现场解吸实验,分析了解吸速率变化、解吸气量大小变化及碳同位素的差异性。解吸气量是指将岩心装入解吸仪之后一定时间范围内所解吸出的天然气数量,主体反映岩石中的吸附气数量及部分游离气量。通过与页岩自身品质的比较分析,解吸气量与总有机碳含量呈正相关的关系,与脆性矿物含量呈一定的正相关性;与黏土矿物中的伊蒙混层含量具有一定的正相关性,与伊利石的含量相关性不大,与绿泥石含量具备一定的负相关性。解吸气量与微孔的孔容具备一定正相关性,与介孔的孔容具备较好的正相关性,与大孔的孔容不具备相关性。

Adsorption gas is the main form of shale gas,and research of the characteristics and influencing factors of desorption gas can guide the exploration and development of shale gas.The variation of desorption rate,the change of desorption gas volume and the difference of carbon isotopes were analyzed using desorption experiments of shale gas from Wufeng-Longmaxi formations in Fuling area in Sichuan Basin.The amount of natural gas desorbed within a certain time after a core is loaded into the desorber is measured and mainly reflects the amount of adsorbed gas and part of the free gas in the rock.The comparison with shale quality shows that the amount of desorbed gas is positively correlated with total organic carbon content,brittle mineral content,and the illite/smectite ratio in clay,but not related to illite content.It has a negative correlation with chlorite content.The amount of desorbed gas has a positive correlation with the micropore volume and possesses a good positive correlation with the mesopore volume,but not with the macropore volume.