32~10.5 Ma古韩江三角洲沉积演化与控制因素

近年来，古韩江三角洲已成为我国南海油气勘探的热点，对其开展沉积演化分析有助于评价珠江口盆地油气资源潜力，预测有利勘探区块。依据岩心、测井、钻井和地震资料，分析陆丰-韩江凹陷区32~10.5 Ma沉积相类型和古韩江三角洲演化。韩江-陆丰凹陷古韩江三角洲相可划分为三角洲平原、前缘和前三角洲亚相。古韩江三角洲演化分为3个阶段:第一阶段，渐新统珠海组至中新统珠江组沉积期，古韩江三角洲沉积物粒度粗，三角洲延伸远，主要分布在陆丰凹陷；第二阶段，中新统韩江组下段沉积期，随着海平面上升，古韩江三角洲逐渐向物源区退缩，陆丰和韩江地区以碳酸盐岩台地相和浅海陆棚相为主，海平面在韩江组下段沉积时期达到最大，古韩江三角洲面积达到最小；第三阶段，韩江组上段沉积期，随着海平面下降，古韩江三角洲又开始向盆地推进。 

Sedimentary evolution and controls in paleo-Hanjiang delta from 32 to 10.5 Ma

The paleo-Hanjiang delta has become a focus of petroleum exploration in the South China Sea. The sedimentary evolution analysis of the paleo-Hanjiang delta is helpful to evaluate the potential of petroleum resources in the Pearl River Mouth Basin and predict favorable exploration blocks. The sedimentary facies types and evolution of the paleo-Hanjiang delta in the Lufeng-Hanjiang sags from 32-10.5 Ma were analyzed based on core, logging, drilling and seismic data. The results show that paleo-Hanjiang delta can be subdivided into delta plain, delta front and pre-delta in the Hanjiang-Lufeng sags. The evolution of the paleo-Hanjiang delta has experienced three stages. In the first stage, during the sedimentary period from the Zhuhai Formation to the Zhujiang Formation, the sediments of the paleo-Hanjiang delta were coarse in grain size and extended in the delta, mainly distributed in the Lufeng Sag. In the second stage, during deposition of the lower part of Hanjiang Formation, the paleo-Hanjiang delta gradually had reduced provenance in response to increasing sea level. Shallow shelf and carbonate platform were dominant in the Lufeng and Hanjiang area. The sea level reached its maximum in the lower section of the Hanjiang Formation, and the area of the paleo-Hanjiang delta reached its smallest. In the third stage, during the sedimentary period of the upper section of Hanjiang Formation, the paleo-Hanjiang delta began to advance to the basin as the sea level fell.