阿姆河右岸中-下侏罗统烃源岩地球化学特征及其沉积环境研究

Geochemical characteristics and sedimentary environment of the Middle and Lower Jurassic source rocks in the right bank of the Amu Darya River

阿姆河盆地是中亚地区天然气资源最丰富的盆地。阿姆河右岸区域的主力烃源岩存在于中-下侏罗统的煤系地层中,但烃源岩的地球化学特征、有机质来源及沉积环境还需进一步明确。本文以阿姆河盆地右岸地区侏罗系烃源岩为对象,在利用烃源岩样品开展系统的地球化学测试的基础上,对样品有机碳、镜质体反射率、饱和烃与芳烃气相色谱及有机碳同位素等数据进行了分析。结果表明:1)阿姆河右岸中-下侏罗统烃源岩的有机质丰度及生烃潜力较高,有机质类型以Ⅱ_(1)与Ⅱ_(2)型为主,存在少量Ⅲ型干酪根,烃源岩整体处于成熟—高成熟阶段;烃源岩以生油为主,兼生气。2)阿姆河右岸中-下侏罗统烃源岩大部分沉积于高盐度的强还原环境,少数沉积于低盐度氧化环境中。3)阿姆河右岸中-下侏罗统烃源岩中有机质母质的来源主要为低等浮游生物,部分有机质来源于高等植物。

The Amu Darya Basin is the most abundant basin of natural gas resources in Central Asia.The main source rocks in the right bank of the Amu Darya Basin exist in the Middle and Lower Jurassic coal measure strata,but the geochemical characteristics,organic matter sources and sedimentary environment of the source rocks need to be further clarified.Based on systematic geochemical tests of Jurassic source rocks in the right bank of the Amu Darya Basin,the data of organic carbon,vitrinite reflectance,saturated hydrocarbon and aromatic hydrocarbon gas chromatography and organic carbon isotope of the samples were analyzed.The results show that:1)the abundance of organic matter and hydrocarbon generation potential of the Middle and Lower Jurassic source rocks in the right bank of the Amu Darya River are high.The kerogen types are mainlyⅡ_(1) andⅡ_(2),with a small amount of typeⅢ.The source rocks are in the mature to high mature stage.The predominant source rocks primarily generate oil,with a minor gas contribution;2)most of the Middle and Lower Jurassic source rocks in the right bank of the Amu Darya River were deposited in the highly reducing environment with high salinity,while a few were deposited in the oxidizing environment with low salinity;3)the source material of organic matter in the Middle and Lower Jurassic source rocks in the right bank of the Amu Darya River is mainly lower plankton,and some organic matter comes from higher plants.