湖盆深水区细粒沉积成因研究进展——以鄂尔多斯盆地延长组为例

对于以中新生代陆相湖盆勘探为主的中国,随着勘探领域由湖盆的浅水区转向深水区,打破了深水区为油气勘探禁区的观念。而深水细粒沉积的研究程度低,早期大多集中于烃源岩生油潜力分析。为了更好地认识深水区细粒沉积类型及成因,为非常规油气勘探提供指导,该文以鄂尔多斯盆地延长组为例,在调研大量文献资料的基础上,结合现代分析测试技术,对深水区的沉积相及岩石沉积成因进行了研究。主要探讨了深水原地沉积、凝灰岩、深部热液、远端浊积岩、放射性铀等的特征及成因,认为岩矿分析、地球化学分析是研究细粒沉积的主要手段,而纳米技术将是当前和今后的重要研究方法。深水区细粒沉积中发育一定量的孔隙,且由于其紧邻烃源岩,很容易聚集成藏,今后可作为重要的油气勘探对象之一。

Study progress of origin of fine-grained sedimentary rocks in deep-water area of lacustrine basin:Taking Yangchang Formation in Ordos Basin as an example

Since the exploration objects gradually changed from shallow-water to deep-water area in lacustrine basins for China's Meso-Cenozoic lacustrine basins, it will break the concept that the deep-water area is a forbidden zone for hydrocarbon exploration. Fine-grained deposits in the deep-water area were poorly studied in the past, and mainly focusing on the hydrocarbon-generating potential of source rocks. In order to determine the types and origins of the fine-grained deposits in the deep-water area, and to guide unconventional hydrocarbon explorations, a case study was made in the Yanchang Formation of the Ordos Basin. Based on a large amount of previous data and combined with modern testing techniques, the sedimentary facies and origins of rocks in the deep-water area were analyzed, especially the characteristics and origins of deep-water autochthonous sedimentation, tuff, deep thermal fluid, distal turbidite and radioactive uranium. It was emphasized that rock and mineral analysis together with geochemical analysis were the main methods to realize fine-grained deposits, among which nanotechnology would be the main research method in current and the future. A certain amount of pores developed in the fine-grained deposits in the deep-water area, which were close to source rocks, hence were favorable for hydrocarbon accumulation and exploration.