摘要： 准确的岩相古地理恢复对鄂尔多斯盆地奥陶系马家沟组四段有利储集层预测及勘探选区选带具有重要意义。依据野外露头剖面勘查、大量新钻井岩心和岩石薄片观察、单因素图分析、测井岩石结构组分解释和地震资料解译,建立了马家沟组四段台地—台缘—盆地的沉积模式,认为台地边缘带主要沿中央古隆起展布,同时受继承性发育的寒武纪乌审旗古隆起控制,台地内发育近北东向展布的榆林—志丹次级低隆带,低隆带两侧发育台内洼地,进而形成台地内部隆洼相间的沉积格局。重磁及地震资料解释表明,鄂尔多斯盆地中晚元古代发育沿北东向展布的裂陷槽,结合怀远运动构造背景,认为该裂陷槽对马家沟期沉积格局具有重要影响。受古地貌和古裂陷槽的共同作用,马家沟组四段颗粒滩主要发育在中央古隆起和榆林—志丹低隆带,总体呈北东向近似雁列式分布,藻丘发育在盆地东部神木—米脂盐隆地区。综合构造、沉积、储集层特征及勘探实践,优选出榆林—志丹次级低隆带和神木—米脂藻丘发育带是马家沟组四段天然气大规模成藏的有利勘探区。研究结果可为鄂尔多斯盆地马家沟组四段有利储集层的预测及勘探区带优选提供重要依据。

关键词: 鄂尔多斯盆地, 奥陶系, 马家沟组, 碳酸盐岩, 沉积相, 天然气, 地质勘探

Abstract: Accurate restoration of lithofacies palaeogeography is of great significance to the prediction of favorable reservoirs in the Member 4 of Ordovician Majiagou Formation in the Ordos Basin and the selection of exploration regions and belts. Based on the field survey,identification of a large number of newly drilled cores and thin sections,single factor diagram analysis,well log interpretation for rock structure identification,and seismic interpretation,the sedimentary pattern of platform-platform margin-basin for the Member 4 of Majiagou Formation has been established. It is believed that the marginal zone was controlled by the distribution of Central paleo-uplift and the Wushenqi paleo-uplift inherited from the Cambrian. The NE-trending Yulin-Zhidan secondary low uplift zone developed in the platform. The depressions developed at both sides,and it then formed the sedimentary pattern of inter-uplift and depression in the platform. The interpretation of gravity,magnetic and seismic data indicates that the NE-trending aulacogen developed in the Ordos Basin during the Middle and Late Proterozoic,when it was under the tectonic setting of Huaiyuan movement,making this aulacogen have an important influence on the Ordovician Majiagou sedimentary pattern. Affected by the palaeotopography and aulacogen,the NE-trending grain beaches with the echelon form of the Member 4 of Majiagou Formation are mainly developed in the Central paleo-uplift and the Yulin-Zhidan low uplift belt,and the algal mound develops in the Shenmu-Mizhi uplift zone located in the eastern of the sedimentary basin. Based on the comprehensive study of structure,sedimentary reservoir characteristics and exploration practice,the Yulin-Zhidan secondary low uplift belt and the Shenmu-Mizhi algal mound development belt were selected as favorable exploration areas for large-scale gas accumulation in the Member 4 of Majiagou Formation. Results can provide important reference for the prediction and the optimization of exploration target areas of favorable reservoir of the Member 4 of Majiagou Formation in the Ordos Basin.

Key words: Ordos Basin, Ordovician, Majiagou Formation, carbonate rock, sedimentary facies, natural gas, geological exploration

中图分类号: 

• P531