摘要
川中古隆起震旦系气源的问题存在争议。重新梳理了震旦系天然气气源对比的主要地球化学证据,发现:川中寒武系和震旦系的天然气乙烷碳同位素与乙烷含量符合同一个瑞利分馏模型,乙烷碳同位素的差异并非是母质类型造成的;震旦系内部甲烷氢同位素值随碳同位素值增加而异常降低,是因过成熟阶段地层水参与了氢交换反应而非水介质盐度的差异;灯影组储层沥青4-甲基二苯并噻吩/1-甲基二苯并噻吩值西南高,东北低,反映油气主要从裂陷槽筇竹寺组侧向运移而来;C7轻烃富甲基环己烷而贫甲苯,天然气主要来自油裂解而非碳酸盐岩。目前没有充足的地球化学证据证明震旦系烃源岩对灯影组天然气有明显贡献,贡献最大的烃源岩是安岳—德阳裂陷槽内筇竹寺组泥岩。
The origin of natural gas in Sinian of central Sichuan paleo-uplift is controversial.The major geochemical evidence to prove the gas origin was restudied,indicating：The relationship of Cambrian and Sinian＇s ethane carbon isotope and ethane content complies with the same Rayleigh distillation model,so the differences in δ-（13）C_2 was not due to the different parent materials;For Sinian methane,the δD_1abnormally decreases with the increase of δ-（13）C_1,which can be caused by the isotopic exchange with formation water at extremely high maturation stage rather than the different water salinities of their source rock depositional environment;for Sinian bitumen,the alkyldibenzothiophene molecular ratios 4-/1-MDBT is higher in the southwest and lower in the northeast,showing the hydrocarbon was laterally migrated from aulacogen Cambrian Qiongzhusi shale;the C_7 light hydrocarbon was dominated by methylcyclohexane and lack of toluene,proving the gas is from oil cracking instead of carbonates source rock.Therefore,the point that there is significant contribution from Sinian source rock is lack of evidence at present and the major contribution of Sinian gas is from ailacogen Cambrian shale.
出处
《天然气地球科学》
EI
CAS
CSCD
北大核心
2016年第8期1447-1453,共7页
Natural Gas Geoscience
基金
中国石油天然气股份有限公司重大科技专项"四川盆地深层海相碳酸盐岩勘探开发技术现场实验"(编号:2014E-3208(GF))资助
