边界断裂时空差异演化对断陷盆地的控制作用——以松辽盆地南部伏龙泉断陷为例
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The Control of the Spatial and Temporal Differential Evolution of Boundary Faults on Faulted Basins
Taking the Fulongquan Fault Depression in the Southern Songliao Basin as an Example
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收稿日期: 2019-11-25 修回日期: 2019-12-28 网络出版日期: 2020-02-23
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Received: 2019-11-25 Revised: 2019-12-28 Online: 2020-02-23
作者简介 About authors
刘玉虎(1986-),男,甘肃庆阳人,高级工程师,主要从事含油气盆地构造分析及石油地质研究工作.E-mail:liuyuhu2008@163.com
断陷盆地边界断裂普遍具有分段生长特点, 定量表征断层的生长过程及组合模式对盆地形成演化及油气成藏研究具有重要意义。以松辽盆地南部伏龙泉断陷为例,应用三维地震资料,采用断层—位移长度分析方法,对边界断层分段生长与演化过程进行了系统研究,分析了边界断裂时空差异演化对断陷盆地的控制作用。研究表明:伏龙泉断陷边界断裂分段生长控制形成了串联式半地堑;沙河子至营城期断裂差异演化控制沉积中心由南向北迁移;反转期边界断裂逆冲形成断展背斜,逆冲活动强弱控制了背斜圈闭的构造幅度高低;边界断裂性质的转化,相应控制了盆地构造格局由同期串联式半地堑向断展背斜带的演变。
关键词:
The boundary faults of faulted basins generally have segmental growth characteristics. Quantitative analysis of fault growth processes and combined models is of great significance for basin formation and evolution and hydrocarbon accumulation. Taking the Fulongquan fault depression in the southern part of the Songliao Basin as an example, using the 3D seismic data and using the fault-displacement length analysis method, the segmental growth and evolution process of the boundary fault is systematically studied, and the control effect of the spatial and temporal differential evolution of boundary faults on faulted basins is analyzed. The study shows that the segmental growth control of the boundary fault of Fulongquan fault depression forms a series of semi-mantle shoals; the sedimentary center of the Shahezi-Yingcheng fault is controlled to migrate from south to north; The slanting and thrusting activities control the height of the anticline trap; the transformation of the boundary fault property controls the evolution of the basin's tectonic pattern from the tandem semi-mantle to the faulted anticline.
Keywords:
本文引用格式
刘玉虎, 曹春辉, 李瑞磊, 朱建峰, 徐文, 黄兰, 栾颖.
Liu Yuhu, Cao Chunhui, Li Ruilei, Zhu Jianfeng, Xu Wen, Huang Lan, Luan Ying.
1 概 况
伏龙泉断陷位于松辽盆地一级构造单元东南隆起之上(图1),断陷面积约1 000 km2,最大埋深5 000 m,与双辽断陷、梨树断陷和德惠断陷等共同构成东南隆起之上的二级负向构造单元[1]。伏龙泉断陷为典型的东断西超箕状断陷,与松辽盆地的构造演化进程一致[2,3,4,5,6],发育下部断陷层序(火石岭组、沙河子组和营城组)、中部坳陷层序(登娄库组、泉头组、青山口组、姚家组和嫩江组)及上部反转层序(四方台组和明水组—新生界)。晚白垩世末期古近纪构造反转作用,使松辽盆地东南隆起区大幅度隆升,尤其在明水组沉积末期反转抬升之后长期处于隆起状态,导致伏龙泉坳陷构造层部分受到剥蚀,这次反转构造变形对油气运移、聚集、调整产生了重要影响[4,5,7,8,9,10]。
图1
图1
伏龙泉断陷构造位置及地层综合柱状图
Fig.1
Comprehensive histogram of the structural location and stratigraphy of the Fulongquan fault depression
陆相断陷盆地边界断层生长过程控制了盆地的演化与沉积充填[11],20世纪80年代以来,很多学者针对边界断层进行了大量研究,提出断层分段生长模型,认为裂陷早期由多条小断层分段生长,逐渐侧向连接、相互作用形成一条边界断层,断层的局部位移极小处即是断层的连接点[12,13,14,15]。断层最大断距(dmax)和长度(L)在双对数坐标下呈现线性关系[16,17,18]。其关系为dmax=cLn,其中c为常数,n的取值范围为1~2。随着断层分段生长量化研究的不断深入,更多学者认为,边界断裂的分段生长过程控制了洼槽的迁移,同时控制了沉积体系及砂体的展布,对油气运聚至关重要[19,20]。因此,本文基于研究区三维地震资料,结合钻采资料,采用断层—位移长度分析方法,对边界断层分段生长与演化过程进行了系统研究,分析了边界断裂时空差异演化对断陷盆地的控制作用,对油气勘探具有重要指导意义。
2 边界断裂几何学特征
表1 伏龙泉断陷边界断裂要素表
Table 1
断层编号 | 断层性质 | 断开层位 | 最大断距/m | 延伸长度/km | 走向 | 倾向 | 主活动期 |
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F1 | 上逆下正 | T2~T5 | 3 200 | 25.1 | NE | NW | 沙河子期 |
F2 | 上逆下正 | T2~T5 | 3 500 | 35.2 | NE | NW | 沙河子期 |
F3 | 上逆下正 | T2~T5 | 4 075 | 20.0 | SN | W | 营城期 |
图2
图2
伏龙泉断陷过边界断裂主测线地震剖面
Fig. 2
Seismic section of the main survey line of the boundary fault in the Fulongquan fault depression
3 边界断裂时空差异演化对断陷盆地的控制作用
3.1 伸展期断裂时空差异演化控制沉积中心横向迁移
图3
图3
伏龙泉断陷边界断裂生长活动历史
(a)边界断裂现今位移—距离剖面;(b)边界断裂不同沉积期古落差—距离剖面;(c)边界断裂活动速率;(d)边界断裂反转逆冲断距
Fig. 3
History of fault growth activities at the boundary of the Fulongquan fault depression
(a) Current displacement-distance profiles of boundary faults; (b) Paleo-difference-distance profiles of boundary faults in different depositional periods; (c) Boundary fault activity rate; (d) Boundary fault inversion thrust distance
从现今位移—距离剖面可以看出(图3a),伏龙泉断陷边界断裂主要为4条断层分段生长连接而成,每条断裂位移—距离曲线呈现半椭圆形态,在断层连接处出现位移极小点,为横向凸起位置;在断层中部位移达到最大,为断陷沉降幅度最大、地层沉积最厚位置。
不同沉积期古落差—距离剖面基本反映了反转期之前边界断裂的生长活动过程(图3b),可以看出,对应不同地质时期盆地沉积充填特征也发生规律性的变化,主要表现在以下几个阶段:
火石岭组沉积期:此阶段表现为多条小的分支断裂开始活动,古落差以过L1控制点测线最大,达到699 m,断层各段活动强弱变化大(图3b),相应控制不同位置沉积充填。过边界断裂主测线地震剖面揭示(图2),火石岭组地层厚度在测线d、e具备“楔状”特征,而在测线a、b、c呈近等厚状分布,沙河子组、营城组地层则明显呈“楔状”特征。
图4
图4
伏龙泉断陷沙河子组边界断裂活动强度与地层厚度叠合图
Fig. 4
Overlapping map of boundary fault activity intensity and stratigraphic thickness of Shahezi Formation in Fulongquan fault depression
图5
图5
伏龙泉断陷营城组边界断裂活动强度与地层厚度叠合图
Fig. 5
Overlapping map of boundary fault intensity and stratigraphic thickness of Yingcheng Formation in Fulongquan fault depression
总体来看,伏龙泉断陷随不同时期断层活动强度发生改变,形成了“分段生长、强弱各异、横向迁移”的构造—沉积充填响应特征:在沙河子期,4条控盆断裂开始分段生长,控制3个半地堑的形成演化;至营城期,断裂活动强度差异变化,沉积中心向北迁移,登娄库期则继续保留了这一构造格局。
3.2 边界断裂展布形态控制形成串联式半地堑
图6
图6
伏龙泉断陷同期半地堑串联式平面组合模式
Fig. 6
The planar combination model of Half-graben cascade in the same period of the Fulongquan fault depression
图7
图7
伏龙泉断陷过3个次洼地震剖面
Fig.7
The seismic profiles through three sub-sag in the Fulongquan fault depression
3.3 反转期边界断裂逆冲强弱控制断展背斜构造幅度高低
松辽盆地反转构造样式主要有3类:
考虑到本区反转构造零点较难识别,因此根据反转变形机理和发育过程,采用坳陷期层序登娄库组和泉头组地层顶界面反转逆冲断距来近似反映反转强弱程度。
3.4 边界断裂性质转化控制盆地构造格局演变
图8
图8
伏龙泉断陷伸展期构造变形场模式
Fig. 8
Model of tectonic deformation field during the extension of the Fulongquan fault depression
图9
图9
伏龙泉断陷反转期构造变形场模式
Fig. 9
Model of tectonic deformation field during the inversion period of the Fulongquan fault depression
总体来看,伏龙泉断陷历经断陷期、坳陷期、反转期三大构造演化阶段,3条边界断裂分段生长、差异演化,控制了盆地的沉积充填和主要烃源岩层系的发育,由于边界断裂性质的转化,相应控制了盆地构造格局由同期串联式半地堑向断展背斜带的演变,形成现今构造格局。
4 结 论
伏龙泉断陷边界断裂展布形态控制形成3个同期同向串连式半地堑,每个半地堑是其最基本的单元,分别由边界断裂F1、F2、F3控制,自南向北依次发育3个次洼。
边界断裂时空差异演化,控制形成了“分段生长、强弱各异、横向迁移”的构造—沉积充填响应特征。
反转期边界断裂逆冲形成断展背斜,逆冲活动强弱控制了背斜圈闭的构造幅度高低,逆冲作用呈现南强北弱,背斜幅度呈现南高北低。
边界断裂性质的转化,相应控制了盆地构造格局由同期串联式半地堑向断展背斜带的演变。
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