摘要
根据大量有机地球化学分析资料,系统讨论了北塘凹陷古近系烃源岩有机质丰度特征、有机质类型、有机质演化以及油气勘探等方面的基础地质地球化学问题。认为始新世中晚期湖盆扩张期形成的沙河街组三段,尤其是沙河街组三段下部地层是北塘凹陷主要生油层,它具有有机质丰度较高,转化率较高的特点;渐新世湖盆稳定发育期和抬升期形成的沙河街组一段和东营组烃源岩为差一非生油层。沙河街组三段有机质类型以Ⅰ型和Ⅱ型干酪根为主,沙河街组一段和东营组烃源岩则主要以Ⅲ型干酪根为主,其中的腐泥组和壳质组含量与烃源岩生烃潜力呈正相关关系,而镜质组含量则与烃源岩生烃潜力呈反相关关系,证实主要生烃母质为腐泥组和壳质组。研究区古近系烃源岩镜质体反射率为0.3%-1.1%,总体上处于低成熟-成熟演化阶段,烃源岩演化经历了低成熟和成熟两个演化阶段,有效生油层主要分布在凹陷南部新村、塘沽、新港地区,油气资源量约1.18×108t,新港构造是北塘凹陷下步油气勘探的有利地区。
Based on large quantities of organic geochemistry data,basic geologic geochemistry problems were systematically discussed on abundance characteristics, type, evolution of organic matter of the Paleogene source rocks and the hydrocarbon exploration in Beitang Sag. It considered that the lower part of Shasan member was the main oil source beds of the Beitang Sag, which was formed in lake basin spreading period in mid -later E-ocene and characterized with high organic matter abundance and high transformation rate. Source rocks in Sha 1 member and Dongying formation were poor - non oil source beds,which were formed in stably developed period and elevated period of Oligocene lake basin. The type of organic matter in Sha 3 member was dominated as type Ⅰ and type Ⅱ kerogen. While the source rocks of Sha 1 member and Dongying formation were dominated as type Ⅲ kerogen. The content of sapropel and exinite had direct correlation to hydrocarbon -generating potential of the source rocks, thus the content of vitrinite has inverse correlation to the hydrocarbon -generating potential. It turns out that the main hydrocarbon - generating parent material was sapropel and exinite. The vitrinite reflectance of the Paleogene source rocks was 0. 3 %～ 1.1% and was generally in the evolution stage of low maturity to maturity. The evolution history of organic matter in Beitang Sag can be divided into two stages of low maturity and maturity. The effective oil source beds were distributed mainly in the southern part of Beitang Sag of Xincun - Tanggu - Xingang area with oil - gas resource extent of about 1. 18～10^8t.Xingang structure will be the next favorable exploration target in Beitang Sag.
出处
《油气地质与采收率》
CAS
CSCD
北大核心
2005年第4期35-38,i0004,共5页
Petroleum Geology and Recovery Efficiency
关键词
古近系
烃源岩
有机质
丰度
类型
演化
勘探评价
北塘凹陷
Paleogene, source rock, organic matter, abundance, type, evolution, exploration evaluation, Beitang Sag
