鄂尔多斯盆地南缘中元古界长城系烃源岩地球化学特征

摘要

In order to probe into whether the good source rocks in the Meso-Neoproterozoic could become the premise and foundation of reservoir forming,based on the data analysis of thin-section,TOC,rock py-rolysis,gas chromatography of saturated hydrocarbons and Chloroform pitch"A"group,the petrological characteristics,abundance,types and maturity of organic matter of source rocks are researched on Meso-proterozoic Erathem Changchengian system in the south margins of Ordos basin. It was shown that the source rocks which a set of lagoon facies dark mudstones are mainly developed in the top of the Gaos-hanhe formation of Changchengian system. There are 44. 8% source rocks in dark mudstones,in which the source rocks,poor,better and the best source rocks are 25. 9%,15. 5% and 3. 4%,respectively. It was also shown that the type of organic matter is I kerogen,and the second is II kerogen,and the thermal evolution of source rocks is high,and is in the mature stage,which is the main source of the formation of dry gas. Based on the above research,the source rocks of the Changchengian system have certain hydro-carbon generating capacity,there have formed the premise condition of self generated and self storage type of oil and gas reservoirs in the Meso-Neoproterozoic Erathem.%为了弄清鄂尔多斯盆地南缘中元古界是否发育较好的烃源岩,综合利用野外地质实地考察、有机地球化学分析等方法,对长城系烃源岩野外地质特征和有机质丰度、类型、成熟度进行了研究.该套烃源岩主要发育于长城系高山河组顶部,为一套泻湖相暗色泥岩,累计厚度为38 . 3 m;TOC总体上比较高,达到烃源岩标准的占44. 8%,其中差烃源岩、较好烃源岩和好烃源岩所占比例分别是25. 9%,15. 5%与3. 4%;有机质类型以Ⅰ型为主,其次为Ⅱ型干酪根;长城系暗色泥岩奇偶碳数比OEP值介于0. 76~1. 04之间,最高仅为1. 04,Tmax值介于583~601 ℃.盆地南缘长城系发育较好的烃源岩,具有一定的生烃能力,具备形成原生油气藏的基本前提条件.