南海北部新近系深水低位沉积特征及控制因素

Deposit Features and Control Factors of Low Stands in Deep Water Areas of Neocene in the Northern South China Sea

南海北部是中国重要的油气探区,该地区的深水低位沉积研究是目前油气勘探的热点。在地震、测井及岩心等资料综合分析的基础上,运用层序地层以及沉积分析方法,对南海北部新近系重点层序(SQzj2和SQhj2)的深水低位沉积层序特征及其控制因素进行了研究。研究表明,该区陆坡深水低位域沉积主要包括陆架边缘三角洲、低位扇、下切水道充填等;新近系深水低位沉积体系的展布以及层序结构的演化都不同程度地受到盆地古构造地貌、断裂陆架坡折带、构造沉降(速率)、沉积物供给及相对海平面变化等因素的控制,其中持续的构造沉降是研究区深水低位沉积体系展布及充填演化的主要控制因素。

The Northern South China Sea is an important oil and gas prospect in China. The studies on deposits in low stands in deep water areas of this region are the hot point of current petroleum exploration. On the basis of comprehensive analysis of seismic,well logging and cores,etc.,sequence stratigraphy and sedimentary analysis methods were used to study the deposit sequence features and control factors of low stands in deep water areas of the major sequences( SQzj2 and SQhj2) in Neocene in Northern South China Sea. Study results indicate that the deposits of low stands in deep water areas in continental slope of this region mainly include shelf margin delta,low stand fan and down-cutting channel fill,etc.; the distribution and the sequence structure evolution of low stand deposit systems in deep water areas of Neocene are inordinately controlled by several factors,such as palaeo-tectonic terrain,faulted neritic slope break belt,tectonic subsidence( rate),deposit supply and relative sea level change,etc. Hereinto,the continuous tectonic subsidence is the major controlling factor for the distribution of infill evolution of low stand deposit systems in deep water areas of the study area.