“源-汇”体系主导下的断陷湖盆陡坡带扇三角洲发育模式探讨:以苏丹Muglad盆地Fula凹陷为例

Discussion On Depositional Models of Fan Deltas in Steep Slope Belt of the Rift Basin under the Guidance of Source-to-Sink System Theory: A Case Study from the Fula Sub-basin, Muglad Basin, Sudan

断陷湖盆陡坡带粗粒三角洲地质研究对于油气勘探至关重要。通过岩心、测井和地震资料综合分析,在苏丹Muglad盆地Fula凹陷陡坡带识别出两类扇三角洲,分别为Jake区锥状扇三角洲和Keyi区片状扇三角洲。Jake区物源供给充足,早白垩世持续供源,形成的锥状扇三角洲岩石颗粒较粗,分选-磨圆差,砂体厚度较厚,分布范围较广;Keyi区物源供给不足,形成的片状扇三角洲岩石颗粒较细,分选-磨圆更好,砂体厚度较薄,分布范围有限。文章将"源-汇"体系理论引入到陡坡带粗粒三角洲研究中,通过对母岩剥蚀供源、搬运以及汇聚条件分析,对两类扇三角洲进行成因解释,并建立相应模式,同时指出,"源-汇"体系只有作为一个整体研究,才能较好地预测断陷湖盆陡坡带扇三角洲分布。

The coarse-grained delta, developed in steep slope belt of a rift basin, usually plays an important role in oil and gasexploration. Based on the analysis of core, logging and seismic data, two types of fan deltas are recognized in steep slope belt in theFula Sub-basin, Muglad Basin, Sudan. The taper-shaped fan delta in Jake Area is composed of relatively coarse-grained sandstone andconglomerate with more thickness and wide distribution. The sorting and grounding are poor in this type of fan delta deposition. On thecontrary, the grain is much finer in the platy fan delta in Keyi Area while the sorting and grounding are relatively good. The sand bodyis thin and limited spread. The source is sufficient in Jake Area but insufficient in Keyi Area during the Early Cretaceous. This paperbrings the theory of source-to-sink system into the fan delta research. Through the study about clastic supplying, transporting andaccumulating, the explanation of these two types of fan deltas are given, and the depositional models are built. Only be regarded as awhole, the source-to-sink system study can be utilized to predict the fan delta deposition in steep slope belt of the rift basin.