南海北康盆地新生代重要不整合界面特征与沉积演化规律  

Characteristics of major unconformities and depositional evolution of Cenozoic in Beikang basin,South China Sea

作　　者：唐武 

机构地区：[1]中海油研究总院有限责任公司,北京100028

出　　处：《中国海上油气》2018年第2期9-16,共8页China Offshore Oil and Gas

基　　金：国家自然科学基金重大研究计划"南海深海地质演变对油气资源的控制作用(编号:91528303)";"十三五"国家科技重大专项"曾母-北康盆地群成藏条件与勘探方向(编号:2016ZX05026-004-006)"部分研究成果

摘　　要：以南海北康盆地钻井、测井及区域二维地震资料为基础,结合南海扩张及南沙地块构造演化历史,探讨了该盆地新生代重要不整合界面特征、盆地演化规律及其对沉积体系演化的控制作用,结果表明:北康盆地新生代发育4个重要不整合面,分别为裂开不整合、破裂不整合、碰撞不整合和超覆不整合,据此将盆地新生代演化划分为断拗、转换及拗陷等3个阶段,其中断拗期可分为2幕,断拗I幕对应于南沙地块漂移前,主要发育三角洲、滨浅海沉积;断拗II幕对应于南沙地块漂移期,三角洲规模减小,碳酸盐岩台地开始发育。转换期盆地继承早期沉积环境,为盆内提供物源。拗陷期盆地进入深水沉积环境,主要发育海底扇-水道-块体搬运-深水披覆泥的沉积组合。断拗期发育的三角洲-滨浅海砂岩是盆地最有利的储集体,应沿着盆缘及盆内大型隆起两侧寻找砂体;断拗晚期发育的碳酸盐岩台地储集体是盆地重要的勘探目标,应沿着构造古隆起方向在盆地中部及南部边缘寻找;而拗陷期的深水重力流砂体是盆地潜在的勘探目标,应在盆地西部垂直于陆坡方向向下寻找。Based on drilling,logging and regional 2 D seismic data of Beikang basin,and combined with South China Sea expansion and tectonic evolution history of Nansha block,this paper focuses on discussing major unconformities,evolution of Beikang basin and its controlling effect on the evolution of depositional systems.The results show that four major unconformity surfaces are recognized in Cenozoic,namely,rift onset unconformity,breakup unconformity,collisional unconformity and overlap unconformity.According to these unconformities,the evolution of Beikang basin depositional system in Cenozoic can be divided into three stages,namely,fault-depression stage,transform stage and depression stage,and the fault-depression stage can be subdivided into two episodes.Fault-depression I episode corresponds to the pre-drifting stage of Nansha block,where delta and shallow marine depositional systems mainly developed.Fault-de-pression II episode corresponds to the drifting stage of Nansha block,where the scale of delta decreased and carbonate platform developed.The transform period inherited the earlier depositional environment that provided resources to the inner part of basin.During depression stage,the basin entered into deepwater depositional environment,where the depositional combination of submarine fan-channel-mass transport deposits-deepwater mud mainly developed.The delta and shallow marine sandstones that developed during fault-depression stage are the most favorable reservoirs,which should be searched along basin margin and two sides of inner large scale uplifts.The carbonate platforms that were formed during the late period of fault-depression stage are important exploration targets,which should be explored in the inner part or south margin of the basin along the development direction of tectonic paleo-uplift.The deepwater gravity flow sandstone of depression stage is the potential exploration target,and should be searched in the west part of the basin,perpendicular to the strike of the shelf break.

关 键 词：北康盆地 新生代 不整合 盆地演化 沉积演化 储集体 南沙地块 南海 

分 类 号：TE121.3[石油与天然气工程—油气勘探]