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长期以来,羌塘盆地烃源岩的研究一直限于中生代地层,而对其古生代地层生烃能力一直缺乏系统研究。针对这一问题,本文选择羌塘盆地石炭—二叠系8条剖面的暗色泥岩及碳酸盐岩样品,对其从有机质丰度、有机质类型和热演化程度等方面进行了有机地球化学特征的分析。研究发现,石炭—二叠系可能烃源岩类型包括泥岩和碳酸盐岩两种,其分布总体上受沉积相的控制,碳酸盐岩烃源岩可能为局限台地相发育的泥晶灰岩,而泥质烃源岩主要为三角洲及斜坡相发育的暗色泥岩及凝灰质泥岩。石炭—二叠纪泥岩有机碳含量较高,具有较好生烃能力,大多达到烃源岩标准,尤其是刻莫石炭系剖面及贡日二叠系剖面,大多为中等—好烃源岩。碳酸盐岩有机碳含量总体比较低,为非烃源岩。石炭—二叠系碳酸盐岩烃源岩有机质类型为Ⅱ1型,泥质烃源岩有机质类型主要为Ⅱ2-Ⅲ型。石炭—二叠系烃源岩热演化程度总体较高,除盆地东部刻莫石炭系剖面处在成熟阶段外,大都处在高成熟—过成熟阶段,非常有利于天然气的生成,具备良好的天然气勘探前景。
For a long time, the research on source rocks in the Qiangtang Basin has been limited to the Mesozoic strata, but there has been no systematic study on the hydrocarbon generation ability of the Paleozoic strata. In response to this problem, we selected dark mudstone and carbonate samples from 8 sections of Carboniferous Permian in the Qiangtang Basin to study their organic geochemical characteristics from organic matter abundance, organic matter type and thermal evolution degree analysis. It is found that the possible hydrocarbon source rocks of the Carboniferous-Permian include two types of mudstone and carbonate rocks. Their distribution is generally controlled by sedimentary facies. Carbonatite source rocks may be mudstone with limited platform facies Rock, whereas the muddy source rocks are mainly dark mudstone and tuffaceous mudstone developed in the delta and ramp facies. Carboniferous-Permian mudstones have high organic carbon content and good hydrocarbon generation ability, most of them meet the standards of source rocks, especially the Permo-Carboniferous section and Gongri Permian section, mostly medium-good source rocks. Carbonate organic carbon content is generally low, non-source rock. The organic matter type of Carboniferous-Permian carbonate source rock is Type II1, while the organic type of mudstone source rock is mainly Type II-III. The thermal evolution of the Carboniferous-Permian hydrocarbon source rocks is generally high. Except for the Carboniferous-Carboniferous section in the eastern part of the basin, which is in the mature stage and mature stage, it is very favorable to the generation of natural gas with good natural gas Prospect of exploration.