四川盆地东部走滑断裂识别与特征分析及形成演化:以涪陵地区为例

doi:10.13745/j.esf.sf.2022.12.58

摘要/Abstract

摘要：

近年来的国内外油气勘探实践表明含油气盆地内的基底走滑断裂带为一种新的高产油气富集带,油气勘探开发前景广阔。对基底走滑断裂的识别、几何学和运动学特征分析及“控储、控藏”作用方面的研究越来越引起高度关注。本文利用四川盆地东部涪陵地区的高精度三维地震剖面的断裂构造精细解析、相干体属性和水平时间切片分析、野外露头断裂特征观测等多种资料,基于走滑构造理论,在研究区新发现了规模较大的北西向和北东向基底走滑断裂带的分布,并建立了川东地区走滑断裂在剖面上直立断层和花状构造、平面上线性延伸和地质界线错开、空间上的“丝带效应”和“海豚效应”及主干断裂产状和力学性质“明显分段性”的识别标准。并提出了基于走滑断裂垂直位移量变化和两侧构造活动强度差异性对比分析厘定走滑方向的新方法;依据地震水平时间切片地层界线错开、走滑断裂两侧厚度差异估算走滑距离的方法,实际应用结果表明,NW向基底走滑断裂带现今整体呈现左行走滑特征,但不同时期走滑性质多变,自形成期以来至少经历了5次左行滑动与3次右行滑动,总体表现出“深部左行,浅部右行,北部活动强度大,南部活动强度小”的特点,左行走滑距累积可达到1 400~3 400 m。北东向基底走滑断裂带现今呈现右行走滑特征,累积走滑距约1 930 m。本文提出了NW向与NE向基底走滑断裂带形成演化模式存在着明显的差异性,其主要受控于区域构造运动和不同时期应力场环境演化及区域滑脱层的应力释放作用,NW向走滑作用受下三叠统膏盐滑脱层的影响,NE向走滑活动则受中-下志留统页岩滑脱层的影响。

关键词: 四川盆地东部, 走滑断裂, 几何学特征, 运动学特征, 形成演化模式

Abstract:

Basement strike-slip fault zones of petroliferous basins are newly recognized high-yield hydrocarbon enrichment zones with broad prospects for oil/gas exploration and development. Increasingly more attention has been paid to the identification and geometrical/kinematical characterization of basement strike-slip faults as well as the role of “reservoir/pool controls” in this type of fault systems. This paper reports the new discovery of large-scale NW and NE-trending basement strike-slip fault zones in Fuling area, eastern Sichuan Basin, and establishes the identification criteria for strike-slip faults in this area based on characteristic fault patterns. The characteristic fault patterns include vertical faults and flower-like structures on the profile; planar linear extension of fault with staggered geological boundaries; and obvious segmentation of master faults in “ribbon-like” or “dolphin-like” strike-slip fault patterns and with changing mechanical properties. A new method is proposed for determining the strike-slip directions based on seismic analysis to measure the change of vertical displacements and the difference in tectonic-activity intensities between the two sides of the fault. It is found that the NW-trending basement strike-slip fault zone generally presents left-lateral slip but with variable strike-slip deformations in different evolutionary stages. Since its formation, the NW-trending faults zone has experienced at least 5 left-lateral and 3 right-lateral slip events which can be characterized by left-lateral slip in the deep crust, right-lateral slip in the shallow crust, high activity-intensity in the north and low activity-intensity in the south, with a cumulative left-lateral strike-slip offset reaching up to 1400-3400 m. In comparison, the NE-trending basement strike-slip fault zone is characterized by right-lateral strike-slip, and the cumulative strike-slip offset is about 1930 m. It suggests that there are significant differences in the formation and evolution of the two fault zones controlled mainly by regional tectonic movements, evolution of stress field environment in different evolutionary stages as well as stress release of regional detachment layers where the NW-trending strike-slip fault zone is affected by Lower-Triassic gypsum-salt detachment layer and the NE-trending strike-slip zone is affected by Middle-Lower-Silurian shale detachment layer.

Key words: Eastern Sichuan Basin, strike-slip faults, geometric features, kinematic characteristics, formation and evolution model

中图分类号:

P542.3

曾韬, 凡睿, 夏文谦, 邹玉涛, 石司宇. 四川盆地东部走滑断裂识别与特征分析及形成演化:以涪陵地区为例[J]. 地学前缘, 2023, 30(3): 366-385.

ZENG Tao, FAN Rui, XIA Wenqian, ZOU Yutao, SHI Siyu. Formation and evolution of strike-slip fault zones in the eastern Sichuan Basin and identification and characterization of the fault zones: A case study of the Fuling area[J]. Earth Science Frontiers, 2023, 30(3): 366-385.

图/表 22

图1 四川盆地大地构造位置与构造区划图(A引自文献[34];B据文献[35]补充修改)

Fig.1 Geotectonic location (A), tectonic environment (A, after [34]) and tectonic zoning map (B, modified after [35]) of the Sichuan Basin

图2 四川盆地沉积地层特征与区域构造运动及应力场环境演化(据文献[40]补充修改)

Fig.2 Characteristics of sedimentary strata, regional tectonic movement and environmental evolution of stress field in the Sichuan Basin. Modified from [40].

图3 研究区寒武系底界、志留系底界、上二叠统底界高精度相干体属性切片与断裂系统分布图

Fig.3 High-resolution coherence attribute slices through interfaces T 1q (A), TS (C) and TP2 (E) in the study area and interpretation of the corresponding coherence maps showing the distributions of the fault arrays (B, D, F)

图4 垂直于15号基底走滑断裂带南段的a~c地震剖面的断层解释与未解释对比图图中☉、$\otimes$ 分别代表走滑断裂的两侧断盘朝向读者和远离读者的相对运动方向。

Fig.4 Comparison of interpreted (left) and uninterpreted (right) seismic sections a-c normal to the southern segment of No.15 basement strike-slip fault zone. Symbols (☉) and ($\otimes$) respectively represent the forward and backward movement directions (relative to the reader) of the fault blocks on either sides of the strike-slip fault

图5 垂直于NE-F2、NE-F3、NE-F4基底走滑断裂的1~3地震剖面断层解释与未解释对比图

Fig.5 Comparison between interpreted (bottom penal) and uninterpreted (top penal) seismic sections 1-3 respectively normal to basement strike-slip fault zones NE-F2, NE-F3 and NE-F4

图6 研究区NW向15号(A)和NE-F2(B)基底走滑断裂带两侧地层厚度突变

Fig.6 Interpreted seismic sections showing abrupt stratum-thickness changes on either sides of the NE-trending NE-F2 (A) or the NW-trending No.15 (B) basement strike-slip fault zones in the study area

图7 研究区附近华蓥山二崖野外露头剖面上的走滑断裂重要识别标志照片

Fig.7 Photos showing important structural features on the Erya outcrop profiles for the identification of basement strike-slip faults in the Huaying Mountain area

图8 涪陵地区NW向15号基底走滑断裂带带状展布(A)与水平时间切片同相轴错开图(B)

Fig.8 Zonal plane distribution (A) and fault offset on horizontal time slice (B) of No.15 fault zone in Fuling area

图9 涪陵地区15号基底走滑断裂带主干断裂“丝带效应”地震解释剖面栅状对比图

Fig.9 Grid comparison of interpreted seismic sections of mater-fault segments (A-D) of No.15 fault zone with “ribbon-like” strike-slip fault patterns

图10 涪陵地区15号基底走滑断裂带主干断裂TS、TP1和TP2界面“丝带效应”分段图

Fig.10 Sectional views of interfaces TS, TP1 and TP2 of master faults in No.15 fault zone with “ribbon-like” fault pattern

图11 涪陵地区15号基底走滑断裂带主干断裂“海豚效应”地震解释剖面栅状对比图

Fig.11 Grid comparison of seismic interpretation sections of “dolphin effect” of master fault in No.15 basement strike-slip fault zone in Fuling area

图12 涪陵地区15号基底走滑断裂带主干断裂TS、TP1和TP2界面“海豚效应”分段图

Fig.12 Sectional views of interfaces TS, TP1 and TP2 of master faults in No.15 fault zone with “dolphin-like” fault pattern

图13 基于垂直位移量变化特征的走滑方向厘定方法的原理

Fig.13 Characteristics of vertical displacements and their variation patterns used in the new method to determine strike-slip directions

图14 研究区15号基底走滑断裂带南段沿走向不同地震反射界面垂直位移量变化曲线图

Fig.14 Variation of vertical displacement of seismic-reflection profiles 1-22 along the strike of the southern segment of No.15 fault zone at interfaces TS, TP1, TP2

图15 研究区15号基底走滑断裂带北段沿走向不同地震反射界面垂直位移量变化曲线图

Fig.15 Variation of vertical displacement of seismic-reflection profiles 1-28 along the strike of the northern segment of No.15 fault zone at interfaces TS, TP1, TP2

图16 研究区15号基底走滑断裂带两侧的NW-SE向地震测线平衡地质剖面对比图

Fig.16 Balanced geological profile of NW-SE seismic sections on either sides of No.15 fault zone in different deformation stages for calculating strike-slip directions in each stage

图17 研究区15号基底走滑断裂带两侧不同时期构造活动强度参数对比曲线图

Fig.17 Comparisons of tectonic-activity intensity parameters between the two sides of No.15 fault zone in different geological periods for calculating strike-slip offset in each period

图18 15号基底走滑断裂两侧TP1界面和TP1m界面地层厚度变化曲线对比图

Fig.18 Comparison of stratum-thickness peak positions between surfaces TP1 and TP1m on either sides of No.15 fault zone for calculating strike-slip offset

图19 涪陵地区15号(A)和NE-F2基底走滑断裂带(B)地震剖面断裂期次划分图

Fig.19 Fault development stages revealed on seismic sections of No.15 (A) and NE-F2 (B) basement strike-slip fault zones in Fuling area

图20 四川盆地东部涪陵地区走滑断裂带形成演化机制与区域构造活动的关系 (A)—加里东运动早期;(B)—加里东运动中期;(C)—加里东运动晚期—海西运动早期;(D)—海西运动中晚期。

Fig.20 Relationship between formation/evolution of strike-slip fault zones and regional tectonic activity in Fuling area, eastern Sichuan Basin

图21 四川盆地东部涪陵地区15号基底走滑走滑断裂带形成与多期构造演化模式图

Fig.21 Model for the formation and multi-stage tectonic evolution of No.15 basement strike-slip fault zone in Fuling area, eastern Sichuan Basin

图22 四川盆地东部涪陵地区NE-F2走滑断裂带形成与多期构造演化模式图

Fig.22 Model for the formation and multi-stage tectonic evolution of NE-F2 basement strike-slip fault zone in Fuling area, eastern Sichuan Basin

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