Abstract Despite a recent renewal in exploration, the Ceduna Sub-basin is underexplored and, as is typical with frontier basins, there is considerable uncertainty regarding lithofacies distribution. As such, there is limited understanding of reservoir and seal coupling as well as structural trapping and thus fluid migration pathways within the prospective Late Cretaceous marine and deltaic intervals from the Tiger and Hammerhead supersequences. To address these uncertainties, a stratigraphic forward model using multiple sediment source points and constrained by recent marine survey data was developed to simulate the deposition and preservation of potential stratigraphic successions across the sub-basin. Pseudo-wells have been extracted from the stratigraphic forward modelling output to forecast vertical and lateral stratigraphic trends. These trends were analysed to predict fault seal and structural trapping likelihood using the Shale Gouge Ratio methodology and triangle juxtaposition diagrams. Over the study area, the modelled facies distributions and geometries are consistent with sequence stratigraphy, seismic stratigraphy and well data. The stratigraphic model shows an overall NW to SE trend of decreasing sand volume and sand interval thickness for the Tiger and Hammerhead supersequences. Although this highlights the general trend of a higher likelihood of reservoir presence to the NW of the study area, and more seal presence to the SE, the model predicts enough vertical variability within the supersequences to create ranges of stacked reservoir-seal couplets. The stratigraphic model and fault seal assessment suggest that, in the marine-influenced Tiger and lower Hammerhead supersequences, the best reservoir and top/fault seal couplets are located along a WSW-NE trend to the NW of the study area where faults with throw≥150 m are expected to yield membrane fault seal. The NW corner of the study area is predicted to have high net-to-gross ratio for the upper Tiger, too high to yield any efficient membrane fault seal. In the deltaic upper Hammerhead supersequence, the best reservoir and top/fault seal couplets are expected along an E-W trend in the central part of the study area. Along this trend faults with throw≥100 m are expected to yield membrane fault seal able to impede lateral hydrocarbon flow in modelled mid Campanian reservoirs and a nearshore interval. These inferred Late Cretaceous structural traps could have been charged by hydrocarbons expelled from local Late Cretaceous source rocks between the Cenomanian to the present-day.

中文翻译：

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塞杜纳盆地中部的地层和构造圈闭格架

摘要 尽管最近进行了勘探更新，但塞杜纳亚盆地勘探不足，并且与典型的前沿盆地一样，岩相分布存在相当大的不确定性。因此，对储层和密封层耦合以及构造圈闭以及来自 Tiger 和 Hammerhead 超层序的潜在晚白垩世海相和三角洲层段内的流体运移路径的了解有限。为了解决这些不确定性，开发了一个使用多个沉积源点并受最近海洋调查数据约束的地层正向模型，以模拟整个子盆地潜在地层序列的沉积和保存。已从地层正向建模输出中提取伪井来预测垂直和横向地层趋势。使用页岩泥岩比率方法和三角形并置图分析这些趋势以预测断层封闭和构造圈闭的可能性。在研究区，模拟的相分布和几何形状与层序地层、地震地层和井数据一致。地层模型显示了 Tiger 和 Hammerhead 超层序的砂体积和砂层厚度减小的整体 NW 到 SE 趋势。尽管这突显了研究区域 NW 存在储层的可能性更高，SE 存在更多密封的总体趋势，但该模型预测了超序列内足够的垂直变化，以创建堆积的储层-密封对联的范围。地层模型和断层封闭评估表明，在受海洋影响的 Tiger 和下 Hammerhead 超层序中，最好的储层和顶部/断层密封对位于研究区 NW 的 WSW-NE 趋势，其中距断≥150 m 的断层预计会产生膜断层密封。预计研究区的西北角具有较高的老虎上部净毛比，太高而无法产生任何有效的膜断层密封。在三角洲上部 Hammerhead 超层序中，最好的储层和顶部/断层密封对在研究区的中部沿 EW 趋势出现。沿着这一趋势，距离≥100 m 的断层预计会产生膜断层封闭，能够阻止模拟的坎帕阶中部储层和近岸层段中的横向烃流。