广东三水盆地沉积体系研究

Study on the Depositional system of the Sanshui basin,Guangdong,China

通过大量钻井和露头资料的沉积学研究,确认了白垩纪—古近纪三水盆地存在冲积扇、扇三角洲、河流(辫状河)、三角洲、湖泊五大沉积体系,并详细描述了它们的特征和时空分布规律。根据五大沉积体系在纵向上的叠置关系,把三水盆地分为①早白垩世底部粗碎屑进积阶段;②晚白垩世初始湖泛阶段;③古新世—早始新世湖泊细碎屑加积阶段:④中始新世—晚始新世顶部粗碎屑填积阶段。最后,根据沉积演化过程中的生储盖匹配关系,指出盆地西部宝月地区为最有利的油气勘探区块,最有利的层位为古近系怖心组,最有利的沉积体系为发育在怖心组大岗段之上的冲积扇、扇三角洲和三角洲。

In this paper, five depositional systems are newly set up in the Cretaceous-Paleogene succession in the Sanshui basin, including alluvial fan, fan delta, fluvial （braided river）, delta and lacustrine facies based on abundant outcrops and well data, and also their features and spatial and temporal distribution laws are demonstrated in details. Based on the vertical superposed relation of the five huge sedimentary systems, the Sanshui basin was divided into：①the progradation stage of coarse detrial rocks at the bottom in the Early Cretaceous; ②the original flooding stage in the Late Cretaceous; ③the aggradation stage of lake fine detrial rocks in the Paleocene-Early Eocene; ④the filling stage of coarse detrial rocks at the top in the Middle Eocene-Late Eocene. Finally, according to the matching relation among source-reservoir-caprock during sedimentary evolutionary process, it was pointed out that Baoyue area in the western of the basin is the most favorable place for oil and gas exploration, and the Buxin Formation in the Paleogene is the beat layer, where the most favorable sedimentary system was developed on Dagang Member, including alluvial fan, fan-delta and delta.