鄂尔多斯盆地南缘铜川地区三叠系延长组长9段浊积岩特征及对有机质富集的影响

摘要

Based on core observation and grain size analysis of thin sections, turbidites were identified in Chang 9 Member of Triassic Yanchang Formation in the southern margin of Ordos Basin, and the vertical sedimentary characteristics of the typical Bouma sequence were revealed. Meanwhile, TOC and pyrolysis were tested for the samples of oil shale and organic rich shale in Chang 9 Member of Yanchang Formation in Ordos Basin. The authors analyzed the characteristics of turbidites and their influences on the enrichment of organic matter. The results showed that the kerogen of oil shale and mudstone in the semi-deep lake-deep lake area was mainly type II1, andthe kerogen of mudstone, shale and silty mudstone overlying and underlying the turbidite were mainly type III and type II2. The Chang 9 turbidites had some influences on the organic matter accumulation in the oil shale section.The AB and ABC sequences of turbidites had the greatest influence on the organic matter content in the underlying mudstone and shale deposited, and the organic carbon content was relatively low. The DE sequence of turbidite had relatively less influence on the content of organic matter in the underlying mudstone and shale, and the content of organic matter was relatively high.%通过岩芯观察、岩石薄片粒度分析, 在鄂尔多斯盆地南缘铜川地区三叠系延长组9段识别出了浊积岩, 并揭示了其垂向上典型鲍马序列组合及沉积特征.同时, 对鄂尔多斯盆地延长组长9段的油页岩、富有机质泥岩等样本进行TOC、热解测试, 分析了该段浊积岩特征及对有机质富集的特征及影响.结果表明:半深湖—深湖区油页岩、泥岩干酪根类型以Ⅱ1型为主, 浊积岩上下层位的泥岩、泥页岩、粉砂质泥岩等干酪根类型主要为Ⅲ型和Ⅱ2型.长9段浊积岩对含油页岩段的有机质富集具有一定影响, 浊积岩AB及ABC序列对底部沉积的泥岩、泥页岩有机质含量影响最大, 其有机碳含量相对较低;浊积岩DE序列对底部沉积的泥岩、泥页岩有机质含量影响相对较小, 有机质含量相对较高.