贝尔凹陷烃源岩发育与沉积环境的关系研究

Research on relationship between abundance,types and distribution of organic matter of source rock and sedimentary environments in Bell depression

对贝尔凹陷下白垩统地层不同沉积环境下的泥岩有机质丰度、类型及分布进行分析.贝尔凹陷主要发育扇三角洲、辫状河三角洲、滨浅湖和深湖-半深湖沉积环境.通过对泥岩的TOC值以及S1+S2值以及泥岩的有机质类型分析,认为丰度高、类型好的泥岩不一定沉积在深湖-半深湖环境下,在辫状河三角洲以及滨浅湖环境下也可以发育质量好的泥岩.泥岩的有机质丰度主要受到初始生产力以及保存条件的控制,以贝尔凹陷为例,南一段时期湖盆水体适宜水生生物大量繁殖保证了较高的初始生产力,另外缓慢的沉降速率使得有机质较好的得到保存,从而得到有机质丰度高的泥岩;泥岩的分布主要受当时的水动力条件,以及盆地自身的构造运动控制.

Focused on mudstones of lower cretaceous in Bell depression,this paper was offering the analysis on relationship between abundance,types and distribution of organic matter and different sedimentary environments.Facies like fan delta,braided river delta,shore shallow lacustrine and deep to semi-deep lake mainly developed during the sedimentation period of Bell depression.Through the way of analysis on TOC and S1 ＋ S2 value and types of organic matter of mudstone,it was regarded that mudstones of high quality and better types did not always sediment under the facies of deep to semi-deep lake,but also that of braided river and shore shallow lacustrine.The abundance of organic matter of mudstone was controlled by primary productivity and preservation conditions,as for Bell depression,during the period of K1n1,waters of lake were appropriate for mass propagation of hydrobionts,which assured higher primary productivity.Plus,proper settlement rate gave rise to better preservation of organic matter,which made up mudstones with high quality; the distribution of mudstone was caused by hydrodynamic conditions and tectogenesis of basin durine that period of time.