【作者】 李楠；

【导师】 李巍然；

【作者基本信息】 中国海洋大学 ， 海洋地质， 2010， 博士

【摘要】 南黄海盆地是叠合于下扬子地台前震旦系变质岩基底之上的一个多旋回叠合盆地。北部坳陷是南黄海盆地的次级构造单元,北以千里岩隆起为界,南部地层超覆于南黄海盆地中部隆起之上,整体结构为北断南超,总面积约51000Km2。北部坳陷又可分为九个三级构造单元,包括六个负向构造单元(东北凹、北凹、中凹、西凹、南凹、东凹)和三个正向构造单元(北凸、西凸、南凸)。南黄海盆地北部坳陷自1975年钻探黄二井以来,已经有约三十年的勘探历史。我国在北凹的泰州组岩芯裂隙中见到了液体原油,韩国有2口井见到了气显示,但均未获得商业性油气发现。本文以构造地质学、沉积学、石油地质学理论为基础,利用地震剖面、钻井等地球物理资料,通过构造样式分析、平衡剖面恢复、沉降史分析、沉积相分析等方法,研究该区域的构造演化过程与沉积特征,并进行初步的油气远景分析。研究表明,南黄海盆地北部坳陷构造演化可分为三个阶段,即海相盆地演化阶段(Z-T),陆相断陷盆地演化阶段(K-E)和坳陷盆地演化阶段(N-Q)。在海相盆地演化阶段,南黄海盆地北部坳陷沉积了扬子型基底盖层。地层发育较为齐全,基本无沉积间断。在陆相断陷盆地演化阶段,由于张性断裂的发展,产生了活动性强、分布局限的陆相断陷盆地。到了坳陷盆地演化阶段,南黄海盆地北部坳陷区域性沉降。南黄海盆地北部坳陷的构造样式主要有两类,一类是压性断块和基底逆冲断层,另一类是张性断块,这两类均为基底卷入型构造样式。基底逆冲断层主要位于千里岩隆起南缘,张性断块在坳陷内广泛发育。正、负反转构造在南黄海盆地北部坳陷内均有发育。负反转构造主要分布于千里岩隆起南侧。正反转构造主要分布于东北凹、北凹、中凹和南凹。反转期主要有渐新世和上新世末两期,后者的影响相对较小。构造反转与太平洋板块与欧亚板块的汇聚速率变化有关。南黄海盆地北部坳陷沉降曲线呈两段式,第一段曲线较陡,沉降速率快,对应于断陷阶段；第二段曲线变缓,对应于坳陷阶段。断陷阶段又可进一步分为初始裂陷阶段,强裂陷阶段,裂陷萎缩阶段,反转隆升阶段,整体上具有伸展作用控制下的幕式旋回演化特征。北凹、中凹、南凹有着近似的沉降史,晚白垩世即进入快速沉降期,一直到古新世保持着较高的沉积速率,东北凹则是在古新世进入裂陷高峰期。南黄海盆地北部坳陷从晚白垩世到始新世呈现河流相—湖泊相—河流相的沉积演化特征。晚白垩世时主要发育河流相沉积,至上白垩统泰州组,沉积范围缩小,主要分布于北凹和东北凹,发育有河流相和湖相沉积。阜宁组沉积时期,从阜一段到阜四段,随着水体的加深,沉积物由河流相沉积逐渐转变为湖相沉积。戴南组沉积时期,沉积范围比阜宁组有所缩小,以河流相沉积为主。到三垛组沉积时期,地形逐渐被夷平,主要发育河流相沉积。不同构造阶段的构造格局对盆地的沉积充填具有明显的控制作用。初始裂陷期和强裂陷期的沉积充填,沉降速率快,沉积厚度大,沉积区域受同沉积断裂控制,呈近东西向条带状分布。总体上沉积中心位于北凹和东北凹北界断裂陡坡带。同沉积断裂的差异活动和演化导致沉积中心的迁移。初始裂陷期沉积以河流相为主,随着水体加深湖相沉积逐渐发育。裂陷萎缩期的沉积充填,沉降速率慢,沉积厚度小,沉积范围大。由于遭受了广泛的剥蚀,局部构造活动的差异、次级地堑和地垒等可造成局部残余厚度的明显变化。裂陷萎缩期水体较浅,以河流相沉积为主。更多还原

【Abstract】 South Yellow Sea Basin is a multicycle superimposed basin forming on the pre-Sinian metamorphic rock basement of the Lower Yangtze Platform.North Depression is the secondary structual unit of South Yellow Sea Basin,making Qianliyan Uplift as the northern boundary.Its southern stratum overlaps the Middle Uplift of South Yellow Sea Basin,and on the whole it downfaults to north and overlaps to the south,with a total area of about 51,000 km2.North Depression can be devided into 9 third-level structural units,including 6 negative structural units(Northeast Sag,North Sag,Middle Sag,West Sag,South Sag and East Sag) and 3 positive structural units(North Salient,West Salient and South Salient).Since well Huang 2 was drilled in 1975 in North Depression of South Yellow Sea Basin,it has been almost 30 years already.China has found liquid crude oil in the crack of Taizhou Formation in North Sag,and Korea has found gas show in its 2 wells,but neither of the two countries get commercial gas and oil flows so far.On the base of structural geology,sendimentology and petroleum geology,geophysical data such as seismic profiles and wells are used to study the structural evolution,sedimentary characteristics and hydrocarbon potential of this region by means of structural style analysis,balanced cross-section restoration,subsidence history analysis and sedimentary facies analysis.The result shows that the structural evolution of North Depression of South Yellow Sea Basin can be divided into three stages:the marine basin stage,the continental rift basin stage and depression basin stage. Basement cover of Yangtze style was deposited in North Depression of South Yellow Sea Basin in the marine basin stage.The sequence of the strata was well developed and there was basically no hiatus. Owing to the development of tensional faults,active continental rift basion with limited distribution was developed in the continental rift basin stage. The depression basin stage was the regional subsidence stage of North Depression of South Yellow Sea Basin.There are mainly two kinds of structural styles in the North Depression of South Yellow Sea Basin:compressive block and basement-involved thrust style and tensional block style.Both of them are basement-involved type.The basement-involved thrust is mainly located in the southern edge of Qianliyan Uplift,and the tensional blocks are widely developed.Both positive inversion tectonics and negative inversion tectonics can be identified in the North Depression of South Yellow Sea Basin.The negative inversion tectonics are mailly distributed to the south of Qianliyan Uplift.The positive inversion tectonics are mainly distributed in northeast sag,north sag,middle sag and south sag.The inversion period is Oligocene and late Pliocene.The inversion is related to the convergence rate between Paciffic plate and Eurasia plate.The subsidence curve of North Depression of South Yellow Sea Basin can be divided into two sections.The steep section corresponds to the rift phase in which subsidence rate is high,and the slow section corresponds to the depression phase in which subsidence rate is low.The rift phase can further be diveded into initial rifting stage(Late Cretaceous),high rifting stage(Palaeocene),rifting atrophy stage(Eocene) and inversion-uplifting stage(Oligocene).On the whole it shows the characteristic of episodic rift basin cycle evolution under the control of extensional action.The sedimentary evolution characteristic of North Depression of South Yellow Sea Basin from Late Cretaceous to Eocene can be summarized to river facies-lacustrine facies-river facies.Sedimentation of river facies was well developed in Late Cretaceous.The Late Cretaceous Taizhou Formation which developed sedimentation of river facies and lacustrine facies was districted only in North Sag and Northeast Sag.With the deepening of water,the sedimentary facies of Palaeocene Funing-1 Member to Palaeocene Funing-4 Member gradually changed from river facies to lacustrine facies.The Eocene Dainan Formation developed sedimentation of river facies in a smaller area compared with Funing Formation. The Eocene Sanduo Formation developed sedimentation of river facies after planation.The structural framework has control action on depositional filling of the basin.In the initial rifting stage and high rifting stage the subsidence rate is high and the sedimentation is thick.The sedimentation is distributed in EW trending belts controlled by synsedimentary faults.The depocenter is mainly located in steep slope zone of the northern border fault of north sag and northeast sag.The differential activity and evolution of the synsedimentary fault makes the transfer of depocenter.The sedimentation of river facies is well developed in the initial rifting stage. With the deepening of water,the sedimentary facies gradually changes to lacustrine facies. In the rifting atrophy stage the subsidence rate is low and the sedimentation is thin and wide.Owing to wide-ranging denudation,the difference of local structural activities,secondary horsts and grabens can make obvious differerce of local residual thickness.The river facies are well developed in the rifting atrophy stage.更多还原