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针对鄂尔多斯盆地中东部盐下奥陶系内幕天然气自生自储特征及其相应烃源岩发育不清的实际,利用地球化学与测井技术相结合的方法,分析了研究区奥陶系盐下烃源岩的分布特征。奥陶系马家沟组马五6亚段膏岩最为发育,分布最为广泛,该膏岩层之下发现的自生自储天然气出气点表明了海相碳酸盐岩烃源岩具有一定的生排气能力。研究表明:研究区马家沟组盐下碳酸盐岩烃源岩有机质丰度总体偏低,测试的有机碳含量平均值约为0.2%,大部分低于0.5%;岩石热解Tmax平均值达484℃,处于高成熟—过成熟阶段。平面分布上,盐下碳酸盐岩烃源岩有机碳含量在西部相对较高,向东逐渐降低;有机碳含量在北部相对较高,向盆地中部降低,最南部略有升高。研究区存在3个相对较好的烃源岩有利分布区。
In view of the fact that the autoclaved self-storage of Ordovician insider salt in the middle and eastern Ordos Basin and the development of its corresponding source rock are not well-developed, the combination of geochemistry and well logging techniques was used to analyze the characteristics of Ordovician saltwater Distribution characteristics of source rocks. The Ordovician Majiagou Formation Ma5 6 subglacial gypsum most developed and most widely distributed, found under the gypsum rock spontaneous self-storage natural gas outlet point shows that marine carbonate rock source rock has a certain degree of raw Gas capacity. The results show that the organic carbon abundance of the lower carbonate source rocks in the Majiagou Formation in the study area is generally low, with the average values of organic carbon content of about 0.2% and most of them less than 0.5%. The average values of Tmax Up to 484 ℃, in a high maturity - over maturity stage. In plane distribution, the organic carbon content of source rocks under salt rocks is relatively high in the west and gradually decreases to the east; organic carbon content is relatively high in the north, lower in the central part of the basin and slightly higher in the southern part. There are three favorable distribution areas of source rocks in the study area.