渤海海域埕岛低凸起东部南区新生代断裂系统及油气分布的控制作用

doi:10.13745/j.esf.sf.2021.1.62

摘要/Abstract

摘要：

埕岛低凸起东部南区新生代受控于伸展与走滑作用,断裂构造复杂,传统认为中深层北东向与近东西向断层属于同期同沉积断层。针对这一观点及引起的问题,利用钻井和地震资料,运用构造地质理论解析断裂系统。研究区主要发育正断层、走滑正断层两种类型,断开层位有基底—东营组、平原组—东营组、平原组—基底三种情况,现今断裂以东营组与馆陶组之间的区域不整合面为时限划分为两期断裂系统。早期断裂主要切开基底—东下段,属于同沉积断层;晚期断裂主要切开平原组—东营组,可断达基底,其发育受早期断裂制约。北东向与近东西向断层分别属于早晚两期断裂系统,对油气分布各起关键性控制作用:先期基底升降引起的伸展作用形成北东向断层,控制洼槽地貌与深水重力流沉积环境,发育了连片的层状砂质碎屑流;后期郯庐断裂右行走滑派生了近东西向雁列断层,断层面既充当储层上倾方向的遮挡条件,又在东西向挤压时封闭性变差而变成油气垂向运移通道,断层及断层作用控制了圈闭分布与油气聚集的有序性,自东向西,圈闭及油水界面依次升高且充满度变小,呈全充满、欠充满、半充满等状态。断裂系统研究将地质体置于一定的构造应力场中,分析断层组合的空间排列和交切关系以及断层的力学机制和位移特征等,探究时空演化对油气分布的控制作用。断裂系统研究方法在构造作用叠合区具有适宜性,对该区及类似地区的勘探开发具有现实意义。

关键词: 埕岛低凸起, 叠合构造, 断裂系统, 构造应力, 断层封闭性, 油气运移

Abstract:

The structural sedimentary evolution in southern East Chengdao low rise was controlled by both extension and strike-slip effects in the Cenozoic. The fault combination in this area is complex. It is generally believed that the NE and EW faults in the middle-deep stratum belong to contemporaneous and syngenetic faults. In response to this view and the questions it raised, the fracture system is analyzed on the basis of structural geological theory using drilling and seismic data. In the study area, the main types of faults in Cenozoic strata are normal faults and strike-slip normal faults, and there are three types of fault cutting through the blocks of basement-Dongying Formation, Pingyuan-Dongying Formation, and Pingyuan Formation-basement. Taking the regional unconformity between the Dongying and Guantao Formations as a time boundary marker, the existing faults are divided into the early and late fault systems. The early faults, belonging to synsedimentary fault, primarily grew from the basement to the lower part of the Dongying Formation; the late faults mainly cut through the block of the Pingyuan-Dongying Formation reaching the basement, and their evolution was restricted by pre-existing faults. The NE and near-EW faults belong to these two fault systems, respectively, which played a key role in hydrocarbon distribution. The extension caused by the differential elevation and subsidence of the basement formed the NE faults in the early stage, which controlled the trough landform and the sedimentary environment of deep-water gravity flow, and the continuous layered sandy debris flow was developed. The right strike-slip movement of the Tanlu fault initiated the formation of the near-EW en echelon normal faults in the later stage. Fault planes provided not only shielding for developing upward dip direction of reservoirs, but also vertical migration channels for oil-gas due to poor sealing during near-EW compression. Faults and faulting controlled the order of trap distribution and hydrocarbon accumulation. In the E-W direction, fault block traps and oil-water interface increased in proper sequence, and the degree of fullness successively decreased as full, under filled and half filled, etc. Fault system research, putting the geological body in a certain tectonic stress field, analyzes the spatial arrangement and intersectional relationship of fault combination as well as the mechanical mechanism and displacement characteristics of fault, and explores the control effect of space-time evolution on oil and gas distribution. Its research method is applicable in the areas of superimposed tectonics, which has practical significance for oil and gas exploration and development in such areas.

Key words: Chengdao low rise, superposed structure, fault system, tectonic stress, fault sealing, oil and gas migration

中图分类号:

P618.130.21

谢宗奎, 王志伟, 明玉坤, 王明, 张在振, 杨彬, 马自超, 孙士杰, 黄元俊. 渤海海域埕岛低凸起东部南区新生代断裂系统及油气分布的控制作用[J]. 地学前缘, 2021, 28(5): 413-420.

XIE Zongkui, WANG Zhiwei, MING Yukun, WANG Ming, ZHANG Zaizhen, YANG Bin, MA Zichao, SUN Shijie, HUANG Yuanjun. Cenozoic fault system in the southern East Chengdao low rise of Bohai Sea area and its control on oil and gas distribution[J]. Earth Science Frontiers, 2021, 28(5): 413-420.

图/表 5

图1 研究区构造地理位置图(a)、埕岛地区基底构造格局图(b)、埕岛低凸起东部南区构造图(c),以及地层演化剖面图(d)(b据文献[9]修改;c,d据文献[7]修改)

Fig.1 Geotectonic map of the study area (a), basement structural framework in the Chengdao area (b), structural map of southern East Chengdao low rise (c),and stratigraphic evolution column profile (d) (b modified after [9]; c and d modified after [7])

表1 研究区主要断层要素

Table 1 List of main fault elements in the study area

断层号		断层走向	倾向	倾角/(°)	断开层位	最大断距/m	延伸长度/m	演化时期	类型
F0	正断层	NW-EW	SW	3060	T1¹-T6	280	12 900	Es-Q	持续活动性
F30N	正断层	NE	NW	64	T6-T2¹	120	13 500	Es-Ed	前期活动型
F30S	走滑正断层	NE	SE	70	T1¹-T2¹	200	11 500	Nm-Q	后期活动型
F9	正断层	EW-NE	NNW	58	T1¹-T6	130	5 600	Nm-Q	后期活动型
F8	正断层	EW	N	63	T1¹-T6	70	2 900	Nm-Q	后期活动型
F7	正断层	EW-NE	NNW	69	T1¹-T6	230	8 000	Nm-Q	后期活动型
F10	正断层	EW	N	55	T1¹-T2¹	140	2 600	Nm-Q	后期活动型

图2 研究区地震反射剖面图与断层分布平面图

Fig.2 Seismic reflection profile and fault distribution plan of the study area

图3 研究区断坡控砂模式(a)与砂质碎屑流沉积构造标志(b)(b据文献[17]修改) P1—块状泥砾质中砂岩-粗砂岩,泥砾“漂浮”状排列,略呈逆粒序,反映高密度流中砾石漂移和磨蚀作用,埕北32井,3 488.72 m;P2—中砂岩-粗砂岩,发育塑性条带状泥砾、磨圆状泥砾,反映滑塌、扯裂变形作用,砂岩与泥砾整体“冻结”沉积,埕北32井,3 491.34 m;P3—块状中砂岩-粗砂岩,发育同生平行层理,反映高密度流因重力剪切作用而呈层滑动,剪切面处分选出相对均一的碎屑,埕北323井,3 828.82 m;P4—块状中砂岩-粗砂岩,包裹深色植物碎片,伴生平行层理,反映搬运物快速迁移、滑动,掩埋了生物体,埕北323井,4 235.77 m。P1、P2、P3、P4均反映搬运物受湖水稀释和砂泥分异作用,析出了纯净砂岩,属于砂质碎屑流成因类型。

Fig.3 (a) Model of sandbody development controlled by faults and slopes, and (b) sedimentary structural marks of sandy debris flow in the study area. b is modified after [17].

图4 研究区断层控藏机制(a)与油藏剖面图(b) 自然伽马(Gr)相对低值和地层电阻率(Rt)相对高值井段为储层,一般油层电阻率大于10 Ω·m,水层电阻率值在10 Ω·m以下。

Fig.4 Fault control mechanism for oil reservoir (a) and reservoir profile (b) in the study area

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