宁南地区石炭系沉积演化及烃源岩评价

Carboniferous Sedimentary Evolution of Southern Ningxia and Its Source Rock Evaluation

石炭系是宁南地区油气勘探的新层系。石炭纪宁南地区位于北祁连-河西走廊沉积域的东南部,与北部巴彦浩特盆地及东部鄂尔多斯盆地联系紧密,后两者石炭系已作为其重要烃源岩。宁南地区沉积了近千米厚的石炭系,暗色泥岩和煤层发育,值得进一步开展油气远景调查。研究区经历的多期逆冲推覆运动使石炭系大规模出露,在逆冲推覆带后缘形成多个新生代凹陷盆地,是油气勘探重点。根据露头区地层展布、剖面岩性分析、烃源岩有机地球化学测试及与邻区河西走廊、鄂尔多斯盆地的对比来分析宁南地区石炭系沉积演化、凹陷区不同层系暗色泥岩和煤系地层存在的可能性。研究与对比表明,宁南地区石炭系在凹陷区保存较好,具有很好的生烃潜力和良好的油气前景。

Carboniferous system is the new target strata of hydrocarbon exploration in southern Ningxia. During Carboniferous period, southern Ningxia was in the southeast part of northern Qilian sedimentary area and had close relationships with Bayehot Basin and Ordos Basin. The latter two basins have been proved to have Carboniferous source rock, which suggests that Carboniferous system in southern Ningxia may have some hydrocarbon prospect for its nearly one kilometer strata and thick dark mudstone and coal seam. Southern Ningxia experienced multi-phase thrust-nappe movements, which massively exposed the Carboniferous strata, and meantime developed several Cenozoic depressed basins behind the thrust nappe belts which are the exploration focus. By means of analyzing Carboniferous strata distribution, profile li- thology and organic geochemical test in the outcrop area and comparing with Hexi Corridor and Ordos Ba- sin, this article tries to analyze Carboniferous sedimentary evolution, the possibility of dark mudstone and coal measure strata of different formations in the depressions and its distribution and thickness in southern Ningxia. It turns out that the Carboniferous strata in southern Ningxia preserved well and have good hy- drocarbon generation potential and pretty hydrocarbon ~rosDect.