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鄂尔多斯盆地中南部地区发育含气的长7段页岩.为了充分认识长7段页岩气的生成过程、运移过程以及成藏演化过程,以气体化学与同位素化学相结合为手段,研究了不同气体组分及其同位素在解析过程中的含量变化,认为在页岩气的解析过程中,甲烷的含量逐渐降低,重烃气的含量逐渐升高,气体的干燥系数降低;甲烷的碳同位素逐渐增重,重烃气的碳同位素变化不明显.研究结果表明:解析过程中,二氧化碳体积分数变化范围为0.53%~5.15%,氮气体积分数变化范围为1.24%~4.64%,气体干燥系数在0.43~0.82之间,甲烷碳同位素变化范围为-51.6‰~-33.9‰.基于长7段页岩的气体解析特征,得出长7段页岩气为腐泥型母质生成的油型热解气;长7段页岩对二氧化碳的吸附能力最强,对甲烷的吸附能力次之,对氮气的吸附能力最弱;烷烃气体中,气体的分子体积越小,其在页岩内部的初次运移能力越强;页岩中,吸附态、溶解态及游离态3种赋存相态的页岩气在地质历史过程中不断转化与调整;长7段页岩的平均含气量大致为1.90m3/t.
In order to fully recognize the formation, migration and accumulation of shale gas in the Chang 7 Member, the gasbearing Chang 7 Member shale was developed in the central and southern Ordos Basin.By combining gas chemistry with isotope chemistry, During the analytical process of shale gas, the content of methane decreases, the content of heavy hydrocarbon gas gradually increases, and the drying coefficient of gas decreases. The carbon isotopes of methane The results showed that the volume fraction of carbon dioxide varied from 0.53% to 5.15% and the volume fraction of nitrogen varied from 1.24% to 4.64%. The gas drying coefficient was in the range of 0.43 ~ 0.82, and the range of carbon isotopes of methane is -51.6 ‰ ~ -33.9 ‰. Based on the gas analysis of shale in Chang 7 Member, the oil-type pyrolysis of shale gas from Chang 7 Member was obtained Gas. The sorption capacity of carbon dioxide is the strongest in the Chang 7 Member shale, followed by that of methane, and the weakest is the nitrogen sorption capacity. In the alkane gas, the smaller the molecular volume of gas is, Move more capacity Shale, shale, adsorbed, dissolved and free state of the three phases of shale gas in the geological history of the continuous transformation and adjustment; the average length of 7 shale gas is about 1.90m3 / t.