摘要
“源-储”配置关系认识不清制约了西江主洼古近系油气勘探。依托地震、钻井、古生物等资料,厘定识别出5个层序界面和4个三级层序。建立了西江凹陷北部受先存断裂差异活化及应力场转变主控的迁移型层序演化模式:裂陷初始期(代表层序WCSQ1),多中心分段发育;东部强裂陷期(WCSQ2),东厚西薄、NE向“窄条”状展布;裂陷转换期(WCSQ3),西厚东薄,NE向席状展布;裂陷萎缩期(WCSQ4),近席状展布。文昌组发育辫状河三角洲、扇三角洲、湖相3种沉积体系,识别出2种主要的沉积充填特征:(1)WCSQ2“陡坡型”半地堑,深湖窄盆,富泥少砂;(2)WCSQ3“坡坪式”半地堑,深湖宽盆,砂泥共存。明确了烃源岩-储层配置关系:中深湖相优质烃源岩主要位于WCSQ2东部和WCSQ3西部洼陷中心;辫状河三角洲储集体主要发育于缓坡带WCSQ3和WCSQ4;扇三角洲储集体主要发育于陡坡带WCSQ2和WCSQ3。
The unclear understanding of the relationship between source rock and reservoir in the Xijiang Main Sag restricts the local Paleogene oil and gas exploration.Based on seismic,drilling,paleontological and other data,five sequence boundaries and four third-order sequences were determined and identified.The migration sequence evolution model featured with differential activation of preexisting faults and transformation of regional stress direction was established.In the initial stage of rifting(represented by Sequence WCSQ1),multiple centers distributed.In the strong rifting period(WCSQ2),it was thick in the eastern part of sag but thin in the western,with a“narrow strip”in the northeast direction.In the rifting transition period(WCSQ3),it was thick in the western part but thin in the eastern and in sheet-shaped distribution in the northeast.In the stage of collapse and shrinking(WCSQ4),it shows sheet-like distribution.Three depositional systems of braided river delta,fan delta,and lacustrine facies were identified in the Wenchang Formation.Two major depositional filling styles were recognized.The first is“steep slope”half-graben with deep-lake narrow basin in the WCSQ2,being rich in mud and poor in sand;and the second is“slope flat”half-graben with deep-lake wide basin in the WCSQ3,in sand-mud coexistence.Meanwhile,the relationship between source rock and reservoir was clarified:the middle-deep lacustrine highquality source rock was mainly located in the eastern part of the WCSQ2 and the western depression center of the WCSQ3;braided river delta reservoir is mainly developed in the gentle slope zones of the WCSQ3 and WCSQ4;and fan delta reservoir is mainly developed in the steep slope zones of WCSQ2 and WCSQ3.
作者
黄鑫
陈维涛
王文勇
何叶
HUANG Xin;CHEN Weitao;WANG Wenyong;HE Ye(Shenzhen Branch of CNOOC(China)Ltd.,Shenzhen 518054,China)
出处
《海洋地质前沿》
CSCD
北大核心
2023年第5期43-54,共12页
Marine Geology Frontiers
基金
中国海洋石油集团有限公司“十四五”重大科技项目“陆缘裂谷盆地深层/超深层油气成藏条件与成藏机制研究-珠江口盆地珠一坳陷”(KJGG2022-0403)。
关键词
西江主洼
先存断裂
成盆演化
三级层序
沉积体系
Xijiang Main Sag
preexisting fault
basin forming evolution
third order sequence
sedimentary system
