伊通盆地莫里青断陷双一段高凝油成因探讨

Discussion on the genesis of high pour-point oil in the Shitang-1 member of the Moliqing dowm-hasm,Yitong Basin

莫里青断陷为伊通盆地最南端的一个二级构造单元,古近纪以来经历了张扭、热沉降、压扭和挤压构造演化阶段。通过对烃源岩有机质地化特征及演化的分析,探讨莫里青断陷双一段高凝油的成因,对研究双一段油气成藏机理、预测油气分布具有重要的理论和实际意义。莫里青断陷双一段原油具有含蜡量、凝固点、析蜡温度高和胶质+沥青质含量较低的高凝油特征。饱/芳比值高等原油地化特征显示母质主要为陆生植物为主或者为混合来源的双阳组烃源岩。丰富的陆源有机质和藻类多种先体物质和湖沼相环境为高凝油生成提供了母质条件,长期低演化的特征是构造高部位高凝油保存的关键因素。

The Moliqing downchnsm is a secondary structural unit at the most southern end of the Yitong basin.Since Eogene,it had experienced a number of structural evolution stages such as tensu-shear,thermal subsidence,compresso-shear and compression.By means of analysis of geochemical features and evolution of organic matters in the source rock,genesis of high pour- point oil in the Shuang-1 member of the Moliqing downchasm is discussed,which is of important significance theoretically and practically for prediction of oil and gas distribution.The oil in the Shuang- 1 member of the Moliqing downchasm has features of high wax content,high pour- point and high temperature of wax precipitation as well as characteristics of high pour point oil with low contents of resin + alsphalline.It is indicated from crude geochemical features such as high saturates/aromatics ratio that,kerogen came mainly from land- plant or the Shuangyang Formation is the source rock with mixed sources.Various precursors of abundant terrestrial organic matters and alga as well as the lirnnic facies environment 'had provided parent conditions for the genesis of high pour- point oil.The features of long- term low evolution is the key factor for the retaining of high pour- point oil in the high structural portion.