磨溪气田嘉二段陆表海碳酸盐岩台地内滩体发育规律

Shoal Development within the Epicontinental Carbonate Platform, Jia 2 Member,Lower Triassic,Moxi Gas Field,Central Sichuan Basin

近年来,四川盆地三叠系台缘鲕滩的油气勘探取得了重大的突破和进展,激发了人们对广阔台地内部滩体的研究兴趣。以四川盆地川中地区磨溪气田嘉二2A层为研究对象,通过对区内钻孔的测、录井及岩心芯资料的分析,总结了陆表海碳酸盐岩台地上台内滩体发育特征:向上变浅序列发育、单滩体厚度一般小于4m、累积厚度较小以及横向连续性较差。进一步分析讨论后认为,沉积期古地貌、古水深、海水动荡程度以及古海平面相对升降变化共同控制了台内滩的发育与分布,结果表明陆表海碳酸盐岩台地内继承性古隆起是台内滩体的有利发育区,形成的台内滩体具有一定的厚度规模和较大分布面积,但是台地内部的隆坳地形分异使滩体横向分布变化较大。这些认识可为台内鲕滩储层的下一步勘探提供必要的地质支撑。

The oil and gas exploration for oolitic shoals in the Triassic platform margin in Sichuan Basin makes important breakthrough and headway. This has aroused the research interest for shoal body within wide carbonate platform. Taking the Bed A of the Jia2 Member in the Moxi Gas Field in central Sichuan Basin for an object of study, this article summarizes the development characteristics of the intraplatform shoal in the epicontinental carbonate platform, based on the analysis of the data of logging and coring in the region of interest. The intraplatform shoal is characterized by the shallowing-upward sequence. A single shoal body is less than 4 meters in the thickness. Besides, the cumulative thickness and horizontal succession are both relatively inferior. The further research proves that the development and distribution of the oolitic shoals within the platform are controlled by the depositional palaeogeomorphology, water depth, turbulent of sea water and fluctuation of sea level. Meanwhile the research also indicates that the inherited palaeohigh within the epicontinental carbonate platform is benefit to develop the shoal vertically and horizontally. However, the palaeogeomorphologic differentiation causes horizontally great variation of intraplatform shoal. All of the investigation has laid a solid geologic foundation for the further exploration.