摘要
鄂尔多斯盆地延长组7段（长7段）为典型的湖相沉积。在鄂尔多斯盆地中部地区，由于靠近湖泊的边缘，长7段泥页岩厚度偏薄，针对该地区的烃源岩研究尤其是泥岩的研究薄弱。基于15口探井开展了暗色泥岩的甄别工作并进行了采样，然后运用岩心观察、有机碳测定、岩石热解、色谱-质谱等分析手段，全面获得了暗色泥岩的烃源岩特征参数。研究表明，长7段暗色泥岩发育于弱还原-弱氧化的沉积环境。暗色泥岩的有机质丰度高，平均值2.39%；有机质以Ⅱ型和Ⅲ型为主；生烃潜力好，+平均值7.65 mg/g；热演化适中，平均值0.98%。暗色泥岩的生烃量总计7.93×10 t，排烃量总计3.37×10 t，残留烃量总计4.56×10 t，综合排烃效率42.50%。暗色泥岩与页岩对研究区油气资源的贡献比为1：1.8。长7段暗色泥岩的生烃有机质包括陆源性输入来源和水体有机质来源。
Abstract
The seventh member of Yanchang Formation (Chang 7 Member) in Ordos Basin is typical lacustrine dark mudstone, which slims down while approaching lake rim at the central part of the basin.The study of source rocks, especially the dark mudstone as source rock in that part, has been very limited due to its thinness.Dark mudstone samples from 15 exploration wells in the area are collected and analyzed through core observation, determination, rock pyrolysis, GC-MS and organic carbon isotope analysis.The results indicate a sedimentary environment of weak reduction and oxidation with mixed inputs of plankton and terrestrial plants for the dark mudstone and provide parameters that define the dark mudstone as a good source rock: high (averaged at 2.39%), type Ⅱ and type Ⅲ dominated organic matter with an average + at 7.65 mg/g, and moderate thermal evolution with averaged at 0.98%.The total hydrocarbon generation amount, hydrocarbon expulsion amount and residual hydrocarbon amount of the dark mudstone are respectively measured to be 793, 337 and 456 million tons.And the comprehensive hydrocarbon expulsion efficiency is 42.50%.The contribution ratio of dark mudstone and shale to the oil and gas resources in the area is 1:1.8.All indicate great source rock potential of the stone.
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