羌塘盆地东部上二叠统海陆交互相烃源岩特征及勘探前景
投稿时间:2024-06-14  修订日期:2024-08-21  点此下载全文
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孙伟* 中国地质调查局成都地质调查中心(西南地质科技创新中心) 610000
中文摘要:长期以来,对羌塘盆地烃源岩研究多集中在中生代地层,但近年在羌塘盆地上二叠统发现了大量油气显示,表明上二叠统具有良好的油气勘探潜力。为进一步查明羌塘盆地上二叠统的烃源岩条件,本文选取了羌塘盆地东部上二叠统那益雄组6条野外剖面和1口钻井的暗色泥岩样品为研究对象,通过有机地球化学方法对其进行分析。结果表明:上二叠统那益雄组有机质丰度较高,绝大多数达到烃源岩标准,并含有数量可观的优质烃源岩(TOC>2%);有机质类型以Ⅱ2、Ⅲ型为主,含少量Ⅱ1型,母质呈现混合来源的特征,水生浮游生物和藻类贡献更大,伴有一定量的高等植物输入,多形成于还原-弱氧化环境,部分形成于缺氧的超盐度环境;有机质热演化程度均达到成熟阶段,且以高成熟-过成熟为主,多生凝析油、湿气。综合认为上二叠统那益雄组具有良好的生烃能力,而且其上的拉卜查日组生屑灰岩储层品质良好,两者可以构成有利的含油气系统,并具有良好的油气勘探潜力。
中文关键词:羌塘盆地  上二叠统  那益雄组烃源岩  勘探前景
 
Characteristics and Exploration Prospects of the Upper Permian Marine Land Interacting Source Rocks in the Eastern Qiangtang Basin
Abstract:For a long time, the focus of the hydrocarbon source rocks in the Qiangtang Basin has mostly been on the Mesozoic strata. However, in recent years, a large number of oil and gas discoveries have been found in the Upper Permian sequences in the Qiangtang Basin, indicating a good oil and gas potential. To further identify the source rock conditions of the Upper Permian, dark mudstone samples from 6 profiles and 1 drilling well in the Upper Permian Nayixiong Formation were analyzed by organic geochemical methods. The results show that the organic matter abundance in studied samples is relatively high, with the majority reaching the standards of source rocks and containing a considerable amount of high-quality source rocks (TOC>2%). The organic matter types are mainly II2 and III, and contain a small amount of type II1. Its parent material exhibits a mixed source characteristic, with greater contributions of aquatic plankton and algae and a certain input of terrestrial plants. These source rocks mostly deposited in a reducing environment, and some of them formed in an anoxic condition with hypersaline waters. The degree of thermal evolution of organic matter has reached the mature stage, and mainly falls into the high maturity to over maturity period, which prone to the generation of condensate oil and moisture. It is concluded that the Upper Permian Nayixiong Formation has good hydrocarbon generation ability, and the quality of the bioclastic limestone reservoir above it is good. Both of the source rocks and the reservoir form a favorable oil and gas system and have good oil and gas exploration potential.
keywords:Qiangtang Basin  Upper Permian  Nayixiong Formation source rock  Exploration prospects
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