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板桥凹陷在中国东部中新生代湖相盆地独具特色,现今油气藏气油比(GOR)变化范围为300～3000m3/t,大部分属于天然气饱和-超饱和油气藏。本文首先基于大量岩石热解数据和测井、录井等资料,精细刻划了板桥凹陷烃源灶特征,有效源岩主要位于沙一段和沙三段,主体为II2-III型,有机质丰度为1%～2%的源岩对应的氢指数(HI,干酪根热解烃与总有机碳的比值)在100～300mg/g之间,源岩成熟深度范围约为3600～3800m。在此基础上,计算了沙一段和沙三段源岩的生排烃特征和组分,结果表明,板桥凹陷湖相源岩只有在生烃转化率达到30%左右、镜质体反射率(Ro)达0.8%以上才能实现排烃,沙三段排出烃类GOR超过600m3/t,沙一段排出烃类GOR相对较低,大约为222m3/t,与现今油气藏性质较为一致。中国东部更多的实例剖析表明,源岩的HI0和初始有机质丰度是控制油气藏GOR的关键性因素,板桥凹陷天然气大量聚集成藏归因于腐殖型源岩的存在。
The Banqiao sag is unique in the Mesozoic and Cenozoic lacustrine basin in eastern China. The gas-oil ratio (GOR) of today’s oil and gas reservoirs varies from 300 to 3000m3 / t, most of which are natural gas saturated-supersaturated reservoirs. Based on a large number of rock pyrolysis data and logging and well logging data, the paper first characterizes the hydrocarbon source stoves in Banqiao Sag. The effective source rocks are mainly located in the first and the third sand sections of Shahejiekou II-II, with main body type II2-III and organic matter abundance The corresponding hydrogen index (HI, ratio of pyrolysis kerogen to total organic carbon) of 1% ~ 2% of source rocks is between 100 ~ 300 mg / g, and the maturity depth of source rocks is about 3600 ~ 3800 m. On this basis, the hydrocarbon generation and expulsion characteristics and compositions of the source rocks in the first and the third member of the Shahejie Formation are calculated. The results show that the lake source rocks in the Banqiao sag only have a hydrocarbon conversion rate of about 30% and the vitrinite reflectance (Ro) Up to 0.8%, the GOR of discharged hydrocarbons in the third member of the Shahejie Formation is over 600m3 / t. The GOR of the first-stage discharged hydrocarbons in the first member of Shahejie Formation is relatively low, about 222m3 / t, which is consistent with the nature of current oil and gas reservoirs. More case studies in eastern China show that HI0 and initial organic matter abundance of source rocks are the key factors controlling GOR of reservoirs. The massive accumulation and accumulation of natural gas in Banqiao sag is attributed to the existence of humic source rocks.