珠江口盆地白云深水区深水水道沉积体系及成因模式

Deposition system and formation mechanism of deepwater channel in Baiyun deepwater area,Pearl River Mouth Basin

深水水道沉积是深水油气勘探开发中重要的沉积类型。利用高分辨率三维地震、钻测井等资料,通过地震资料综合解释和地质分析,对南海北部白云深水区珠江组上段发育的大型深水水道的展布特征及成因模式进行识别、刻画和预测。研究认为,该体系近SN向展布,具低弯度蛇曲形态,体系内发育3类深水重力流沉积单元,其中块体搬运沉积发育于白云凹陷东北端,呈丘状外形、内部杂乱反射特征,底部发育侵蚀擦痕;水道为体系主体搬运通道,按成因可分为侵蚀型、侵蚀/加积型和加积型,受控于物源供给及古地貌特征,具"上下分期,南北分段"发育特征,为典型的复合水道沉积构型,复合水道内叠置迁移关系复杂;位于水道前端的朵体发育于荔湾凹陷南部,剖面上表现为强振幅平行—亚平行反射,在平面上具有朵状特征。从古水深、古地形、触发机制及古源头沉积体系等方面综合分析,探讨了该深水水道体系的成因模式,推测古珠江三角洲为其主力物源,东沙隆起碳酸盐岩沉积为次级物源。这一研究对研究深水重力流沉积过程具有重要的参考价值。

Deepwater channel deposits are one of the main depositional types in petroleum exploration and development.Based on high-resolution 3 Dseismic data,logging data and drilling data,a deepwater channel system was discovered in the Zhujiang Formation,Baiyun deepwater area,and the distribution character and genetic model of the system were identified by integrated with geological analysis and geophysical data interpretation.This system is NS-trending in a low sinuosity meandering form,and three types of deepwater gravity-flow deposits were identified,i.e.mass-transport,channel-levee complex and lobate deposits.The mass-transport deposit is developed in the northeast of Baiyun Sag,and has dome shaped appearance,internal chaotic seismic reflection with basal erosion scratches.The channel-levee complex deposit is the main pathway of the deepwater fan system,and can be classified as erosion,erosion/accretion and aggradations according to the origin.The channel deposit has the development feature of generation and segment controlled by source and geomorphology characteristics,and is a typical turbidite channel complexes configuration within complex superposition and migration relations.The lobate deposit which is located in the front of the channel is developed in the south of the Liwan Sag,and comes in a lobe-like shape on plane within a high-amplitude parallel to sub-parallel seismic reflection.And then the genetic model of the deepwater channel system was discussed by integrated with the ancient water depth,palaeotopography,triggering mechanism and the ancient source.The ancient Pearl River delta was speculated as its main source,and the carbonate deposition of Dongsha Massif as a secondary source.The research is of the theoretic significance in studying various depositional processes of deepwater gravity flow.