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白云凹陷恩平组沉积晚期发育大型的辫状河三角洲,但该三角洲的沉积过程、内部发育期次及平面分布规律尚不明确.基于9口钻遇恩三段的钻井资料,开展了砂岩碎屑锆石U-Pb定年及全区覆盖的三维、二维地震资料分析.结果表明恩平组不同沉积时期的主要物源供给方式:恩平组早-中期以白云凹陷四周隆起提供短程物源碎屑为主(母岩类型以中生代火成岩为主),恩平组沉积晚期白云凹陷与北部珠一坳陷开始连通,盆外大型水系携带华南褶皱带物源碎屑沿NW-SE方向进入白云凹陷沉积(母岩类型以古生代-前寒武系变质岩为主),大型三角洲开始发育.地震相及能量半衰时属性分析揭示了白云凹陷恩平组沉积晚期大型三角洲的沉积构成特征,即发育3期不断向东南方向进积的楔状体,其沉积规模由小到大,然后再变小,直至断陷消亡.恩平组沉积晚期三角洲煤系烃源岩及陆源海相烃源岩广泛发育,大型三角洲具备优越的生储盖组合,有利于形成三角洲前缘上倾尖灭油气藏,是白云凹陷深水区古近系油气勘探重要目标.
Large-scale braided river delta developed in Enping Formation of Baiyun Sag, but the sedimentary process, internal development period and plane distribution law of this delta are not clear.According to the drilling data of 9 wells, Zircon U-Pb dating and whole-area 3D and 2D seismic data analysis.The results show that the main source of Enping Formation during different sedimentary periods is the Enping Formation source: short-range source (Mainly Mesozoic igneous rocks). The late Baiyun sag in the Enping Formation and the Chu-1 depression in the north of the Enping Formation began to communicate with each other. Large-scale water systems outside the basin entered the belt of NW-SE along the NW-SE direction Depression and sedimentation (the parent rocks are dominated by Paleozoic-Precambrian metamorphic rocks), and large-scale deltas begin to develop.The analysis of seismic phase and energy half-decay time reveals the sedimentary features of the large sediments of Enping Formation in Baiyun Depression In the third stage, wedges continuously southeastward are deposited, and the sedimentary scale is from small to large and then smaller until they disappear.The Upper Triassic coal-bearing source rocks and terrigenous marine facies The source rocks are widely developed, and the large delta reserves have the advantages of reservoir-cap assemblage, contributing to the formation of up-dip degased reservoirs in the delta front. This is an important objective of petroleum exploration in the Paleogene in the Baiyun Sag.