摘要
北部湾盆地油气勘探已取得丰硕成果,但进一步扩大勘探成果难度不断增大。为了明确该盆地乌石凹陷东区反转构造带的成因机制,指导南海北部油气勘探,以乌石凹陷隆起带构造特征为研究对象,结合构造物理模拟实验,分析了其特点及形成机制,提出了乌石凹陷东区渐新世末期具有东挤西张的“剪刀式开合”构造特征。实验结果很好地再现了统一构造背景下,同时形成伸展和挤压“剪刀式开合”构造的成因机制。研究结果表明:①乌石凹陷东区反转构造带渐新世末期形成两组一侧伸展、一侧挤压的“剪刀式开合”构造;②构造整体上以东北部挤压形成的大范围宽缓背斜为轴,两侧发育两个构造变形区,均表现为西侧伸展、东侧挤压的特征;③构造变形区越向西区延伸,断裂的活动性越强,伸展量越大。结论认为,乌石凹陷东区区域挤压应力作用下共轭断层及其分隔断块体发生旋转是控制研究区开合构造样式差异的成因;受先存基底断裂分割,此类块体旋转在北部湾盆地南部坳陷普遍存在,正好与迈陈凹陷具有西挤东张的特征相对应。
Great achievements of oil and gas exploration in Beibuwan Basin have been made,but several difficulties to expand these achievements are further increasing.In order to clarify genetic mechanisms of inversion structure belt in eastern Wushi sag,and to provide guidance for exploration in northern South China Sea,this study took one uplift belt in Wushi sag as an objective to analyze its structural characteristics and forming mechanisms by virtue of structural physical simulation.And it's indicated that:(1)during late Oligocene,the eastern Wushi sag had some characteristics of"scissorstype opening-closing"tectonics,i.e.,compression in the east and tension in the west.Many experimental results well reproduce the genetic mechanisms of these tectonics with simultaneous tension and compression under unified structural settings.Also during late Oligocene,two sets of"scissors-type opening-closing"tectonics which were tensile on one side and compressive on anther side were formed at the inversion structure belt;(2)on the whole,two structural deformation zones were developed on both sides with a wide and gentle anticline formed under compression in the northeast as an axis,and they are both tensile in the west and compressive in the east;(3)faulting got stronger and its extension became larger as these structural deformation zones extended to the west.In conclusion,a conjugate fault and rotation of its isolated fault block under regional compression stress in eastern Wushi sag are the genesis-dominating style difference of opening-clos ing tectonics.Due to a cutting effect of preexisting basement fault,this kind of mass rotation is common during falling of southern Beibuwan Basin,and it's right correspondent with compression in the west and tension in the east of Maichen sag.
作者
李才
胡林
杨希冰
平贵东
董贵能
Li Cai;Hu Lin;Yang Xibing;Ping Guidong;Dong Guineng(CNOOC Zhanjiang Branch,Zhanjiang,Guangdong 524057,China;School of Earth Sciences,Northeast Petroleum University,Daqing,Heilongjiang 163000,China)
出处
《天然气技术与经济》
2020年第2期1-5,共5页
Natural Gas Technology and Economy
基金
国家科技重大专项(编号:2016ZX05024-002-009)
国家科技重大专项(编号:2016ZX05024-006)。
关键词
北部湾盆地
乌石凹陷
渐新世末期
剪刀式开合构造
共轭块体
Beibuwan Basin
Wushi sag
Late Oligocene
Scissors-type opening-closing tectonics
Conjugate mass
