中国南海A盆地深水区古近系B组层序地层格架特征

CHARACTERISTIC OF SEQUENCE STRATIGRAPHIC TRELLIS OF B FORMATION OF PALEOGENE IN DEEPWATER AREA IN THE A BASIN OF SOUTH CHINA SEA

运用Vail经典的层序地层学理论,针对中国南海A盆地深水区古近系B组地层地震资料品质差,无井资料、断层复杂、高温高压造成地层破碎导致层序界面不明显等困难,综合浅水区井资料和深水区地震资料,采用井震结合相互验证的方法,识别出SB0,SB1,SB2,SB3,SB4等5个层序界面,将B组自下而上划分为SⅠ,SⅡ,SⅢ,SⅣ4个三级层序,建立了研究区目的层三维等时层序地层格架。结果表明,各层序界面和层序厚度在盆地和凹陷不同部位特征各异,形成这种特征的地质要素主要是差异沉降作用、局部隆升剥蚀作用以及盆地断陷作用等。发育在层序界面附近的低位体系域的斜坡扇、盆底扇和高位体系域的扇三角洲等是隐蔽油气藏的发育区和油气勘探的有利区。

Guided by classical sequence stratigraphy theory of Vail,and aimed at the difficulties of poor seismic data quality,no well data,complexity of faults,stratum fragmentation and stratigraphic sequence interfaces unsigned that formed by high temperature and high pressure of B Formation,finely carved up the stratum of B Formation of Paleogene in deepwater area.In this process,the well data of shallow water area and the seismic date of deepwater area were used,and five sequence interfaces of SB0,SB1,SB2,SB3 and SB4 were identified.Then the stratum of B Formation of Paleogene were divided into four third-class sequences of SⅠ,SⅡ,SⅢ and SⅣ,and the three-dimensional isochronous stratigraphic sequence trellis of B Formation in the study area were founded.The study results show that reasons of the space-time distributing characteristic of each sequence were differently depositing,partly ascending and denudation effect and rift faulting.Slope fan and basin floor fan developed in LST and fan deltas deve-loped in HST were stratigraphic traps developed areas and favorable areas of prospecting.