海拉尔塔木察格盆地中部断陷带油气形成条件及富集规律

Formation and Accumulation Rules of Oil and Gas in Middle Fault Depression Belt of Hailar-Tamtsag Basin

海拉尔塔木察格盆地中部断陷带油气藏具有很大的资源潜力和储量规模,在白垩系均有广泛的分布,具备良好的油气地质背景和成藏条件,是未来油气勘探的重点领域,其形成条件及富集规律不明。笔者在大量统计分析和地质研究的基础上,探讨了中部断陷带油气藏的形成条件、分布特征和富集规律。指出油气藏形成的地质背景:该区经历了5期构造运动,其中3期改造强烈,形成3期叠合盆地,奠定了富油洼槽和油气规模富集的构造格局;不同演化时期发育的沉积体系类型不同,断裂坡折带和构造转换带控制扇体的展布,为油气规模富集提供了有利的储集空间;高含火山碎屑物质受有机酸溶蚀形成次生孔隙,为深部油气成藏提供了有效储层空间。系统分析得出油气藏形成控制因素和分布规律:复式箕状断陷凹中隆起带和大型缓坡断阶带是有利的油气成藏区带;烃源灶控制了油气藏的分布范围,已发现油藏主要分布在生烃洼槽内或周边;扇三角洲前缘、三角洲前缘及水下扇中扇相带是最有利的含油相带,是油气富集高产的重要因素。

The oil and gas reservoir in the middle fault depression belt of Hailar-Tamtsag basin shows great potential and with large scale.They distribute widespread in the Cretaceous sequences. Although it has been provided with favorable geology and accumulation conditions of oil and gas,and serves as the key field of oil and gas exploration in the future,the formation and accumulation rules are not clear.Based on integrated statistic analysis and geological data, we focus on the formation, distribution,and accumulation of oil and gas reservoir in the area.The controlling factors are as follows.First,multi-period structural movement controlled the basin framework and established the structural pattern of depression with rich oil accumulation.Second,different tectonic phase controlled the sedimentary infilling evolution.The fault slope break belt and structural transfer zone controlled the fan body distribution.All of them supply advantageous reservoir for oil and gas accumulation with great scale.Third,clastic rock with high content of volcanic substance was easy to dissolve,which resulted in the development of secondary pore,and it created beneficial condition for the formation of favorable reservoirs.We therefore that concluded that the concave uplift belt of composite half-graben fault depression and the great gentle slope fault terrace belt served as favorable oil and gas reservoir. Hydrocarbon kitchen controlled the distribution of oil and gas reservoir.The favorable facies belt was an important factor for oil and gas enrichment.The results may be useful for the consideration in similar petroleum system exploration.