Stratigraphic Constraints on Sandy Conglomerates in Huanghekou Sag, Bohai Bay Basin, via In Situ U-Pb Dating of Vein Calcite and Detrital Zircons, and XRD Analysis
Stratigraphic Constraints on Sandy Conglomerates in Huanghekou Sag, Bohai Bay Basin, via In Situ U-Pb Dating of Vein Calcite and Detrital Zircons, and XRD Analysis
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DOI：
10.3390/en15113880
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发表时间：
2022-05
期刊：
影响因子：
3.2
通讯作者：
Wei Wang;Xianghua Yang;Hongtao Zhu;Li Huang
中科院分区：
文献类型：
--
作者：
Wei Wang;Xianghua Yang;Hongtao Zhu;Li Huang
渤中19 -6大型凝析气田的发现，说明渤海湾盆地桑迪岩储层的巨大潜力。然而，由于缺乏同沉积火山岩层和生物地层学的制约，黄河口凹陷北方桑迪岩序列的地层对比仍然是一个挑战。这一挑战限制了对区域地层分布的了解和进一步的勘探部署。本文对BZ 26-A孔桑迪岩中的脉状方解石和碎屑锆石进行了原位U-Pb定年。脉状方解石年龄和碎屑锆石最年轻年龄分别提供了沉积年龄的上限和下限。我们还通过XRD矿物成分的比较，将样品与那些来自已知地层的样品进行了关联。脉状方解石的绝对年龄为47.0Ma，碎屑锆石的最年轻年龄为103.5Ma，表明该沉积序列为孔店组（65 ~ 50.5Ma）。黄河口凹陷孔店组岩石地层至少可划分为三段，三段为干热气候条件下的红色沉积物，二段和一段为扇三角洲沉积，母岩分别为中生代火山岩和前寒武纪变花岗岩类。第1段由于高脆性矿物成分和裂缝发育，显示出巨大的能源勘探潜力。
The discovery of the BZ19-6 large-scale condensate gas field illustrates the great potential of the sandy conglomerate reservoirs in the Bohai Bay Basin. However, the stratigraphic correlation of the sandy conglomerate sequence in northern Huanghekou Sag remains a challenge due to the lack of syn-depositional volcanic layers and biostratigraphic constraints. The challenge limits understanding the regional strata distribution and further exploration deployment. In this study, we conducted in situ U-Pb dating of vein calcite and detrital zircons of the sandy conglomerate samples from borehole BZ26-A. The vein calcite age and the youngest age of detrital zircons provide the upper and lower bounds of the depositional age, respectively. We also correlated the samples with those from well-understood strata through a comparison of XRD mineral components. The absolute age of 47.0 Ma of the vein calcite and the youngest detrital zircon age of 103.5 Ma suggest the sedimentary sequence is supposed to be referred to as the Kongdian Formation (65–50.5 Ma). The XRD data and petrological analysis suggest that the lithostratigraphy of the Kongdian Formation in Huanghekou Sag could be divided into at least three members, with Member 3 consisting of red sediment deposited in a hot and dry climate; Member 2 and Member 1 deposited as fan delta with major parent rock of Mesozoic volcanic rocks and Precambrian meta-granitoid, respectively. Member 1 shows significant potential for energy exploration due to high brittle mineral components and fracture development.