博尔塔拉盆地油气显示的地质地球化学意义

THE GEOLOGICAL AND GEOCHEMICAL SIGNIFICANCE OF OIL AND GAS SHOWS IN THE BORTALA BASIN,NORTHERN XINJIANG

博尔塔拉盆地是准噶尔盆地西缘外围的中小型盆地,1992年在这个盆地中首次发现了油浸碎屑岩。本文从地层、构造与油浸碎屑岩的地球化学特征等方面指出了盆地可能存在油气远景。对油浸碎屑岩的实验研究表明:抽提物中含有丰富的生物标志物;有机质母质来源为混合源,既有高等植物输入,也有藻类输入,油源为海相和陆相生油层;有机质成熟度一般,非高成熟度油。盆地地质研究表明:生油层为侏罗纪、二叠纪陆相地层和石炭纪海相地层,储层丰富,除中上侏罗统和新生界可作为盖层外,阿拉套山推覆体可能是博尔塔拉原形盆地油气的良好盖层,具备生储盖组合条件。

The Bortala basin is a small-sized basin bordering on the western margin of the Junggar basin, northern Xinjiang. In 1992 oil-soaked clastic rocks were discovered in this basin. The stratigraphy , tectonics and geochemistry of the oil-soaked clastic rocks indicate that there might exist petroleum prospects in this basin. Experimental study of oil-soaked clastic rocks shows that: the extract from the rock has abundant biomarkers; the organic matter was derived from a mixing source, i. e. there were both the input of higher plants and the input of algae; the oil source comprised both marine and continental source beds; the oil was related to organic matter with ordinary maturity and is not highly mature one. The geological study of the basin suggests that: the source beds are Jurassic and Permian continental strata and Carboniferous marine strata; reservoir rocks are plentiful; the Middle-Upper Jurassic and Cenozoic might act as cover rocks, and in addition the Alataw nappe might probably serve as a good cap bed for the petroleum in the Bortala original basin. So the basin has good conditions for an association of source, reservoir and cap rocks.