复杂构造变形区断控裂缝发育分布模式

doi:10.13745/j.esf.sf.2024.6.20

摘要/Abstract

摘要：

天然裂缝是油气重要的储集空间和渗流通道。在复杂构造变形区,裂缝明显受断层影响控制,但其规律和模式尚不清晰。为此,本次研究以库车坳陷为例,通过现场地质观测、成像测井裂缝解译和理论分析,计算断控裂缝系数,揭示走滑断层、逆冲断层控制复杂构造变形区天然裂缝的规律,提出断控裂缝发育分布模式。结果表明:(1)逆冲断层对天然裂缝产状和发育程度均具有明显的控制作用,裂缝密度与距断层距离呈现负指数关系,距断层由近及远可以划分为断层强控制裂缝带、断层弱控制裂缝带和区域裂缝带。(2)走滑断层包括调节走滑断层和逆冲-走滑断层。调节走滑断层与地层走向近垂直或大角度斜交,发育断层控制裂缝带,其受断层规模影响显著;逆冲-走滑断层与地层走向近平行或者小角度斜交,天然裂缝主要局限于断层带内,沿断层走向断裂带宽度发生变化。(3)定义断控裂缝系数(K),即断层强控制裂缝带宽度与断层断距(滑距)的比值,通过分析,库车坳陷逆冲断层K值为1.50~1.80,走滑断层K值为0.125~0.150。研究成果对复杂构造变形区油气勘探开发具有理论和实践指导意义。

关键词: 裂缝发育分布模式, 断控裂缝系数, 走滑断层, 复杂构造变形区, 库车坳陷

Abstract:

Natural fractures are important reservoir spaces and seepage channels for oil and gas. In complex structural deformation zones, fractures are obviously controlled by faults, but the laws and modes of fracture formation are not yet clear. This study investigates natural fractures developed in complex fault zones in the Kuqa depression. Based on geological observation, fracture interpretation from imaging logging, and theoretical analysis, a “fault-controlled fracture coefficient (K)” is defined and calculated to reveal the development and distribution pattern of fault-controlled fractures in the study area. The results indicate (1) the thrust faults obviously control both the occurrence and development of natural fractures, where the fracture density is exponentially inversely proportional to the distance from the fault, and the fault-controlled fracture zones can be divided into strongly-controlled, weakly-controlled, and regional fracture zones with increasing distance to the fault. (2) Among the strike-slip faults, high-angle oblique faults develop fault-controlled fracture zones where fracture development is significantly affected by the scale of the faults; while fractures associated with oblique thrust faults are mainly developed within the fault zone, and the width of the fault zone varies along the strike direction. (3) The fault-controlled fracture coefficient (K) is defined as the ratio of the width of the strongly-controlled fracture zone to the fault displacement (slip displacement). According to the analysis, the K values of thrust faults in the Kuqa depression ranged between 1.50-1.80, and that of strike-slip faults ranged between 0.125-0.150. The results have both theoretical and practical significance for guiding oil and gas exploration and development in complex structural deformation zones.

Key words: fracture development and distribution pattern, fault-controlled fracture coefficient, strike-slip fault, complex structural deformation zone, Kuqa depression

中图分类号:

鞠玮, 杨慧, 侯贵廷, 宁卫科, 李永康, 梁孝柏. 复杂构造变形区断控裂缝发育分布模式[J]. 地学前缘, 2024, 31(5): 130-138.

JU Wei, YANG Hui, HOU Guiting, NING Weike, LI Yongkang, LIANG Xiaobai. Development and distribution pattern of fault-controlled fractures in complex structural deformation zones[J]. Earth Science Frontiers, 2024, 31(5): 130-138.

图/表 10

图1 库车坳陷构造单元划分与典型地质剖面图 a—塔里木盆地位置及构造单元划分图;b—库车坳陷构造单元划分图;c—库车坳陷典型地质剖面图。图中符号: Є—寒武系;O—奥陶系;S-D—志留-泥盆系;C—石炭系;P—二叠系;T—三叠系;J—侏罗系;K—白垩系;E1-2km—库姆格列木群;E2-3s—苏维依组;N1j—吉迪克组;N1-2k—康村组;N2k—库车组;Q1x—西域组。

Fig.1 Geographic location, structural units and typical geological section of the Kuqa depression

图2 库车坳陷吐尔力克河逆冲断层野外照片(a,b)及裂缝地质建模(c) a—吐尔力克河逆冲断层远观照片;b—吐尔力克河逆冲断层近观照片;c—断层上盘裂缝解译图。

Fig.2 Field photos of the Tuerlike River fault in the Kuqa depression (a, b) and its associated fractures by geological modeling (c)

图3 吐尔力克河逆冲断层控制裂缝发育分布规律 a—天然裂缝(包括区域裂缝和断层相关裂缝)密度与距断层距离的关系图;b—断层相关裂缝密度与距断层距离的关系图。图中:x表示距断层距离,m;y表示裂缝密度,m-1;R为相关系数。

Fig.3 Relationship between fracture density and the distance to fault by geological observation (a) and theoretical analysis (b) on natural fractures controlled by the Tuerlike River thrust fault

图4 库车坳陷走滑断层类型示意图 a—阿格逆冲-走滑断层;b—库东调节走滑断层;c—俄矿逆冲-走滑断层。图中地层:T3h—黄山街组;T3t—塔里奇克组;J1a—阿合组;J1y—阳霞组;J2kz—克孜勒努尔组;J2q—恰克马克组;J3q—齐古组;J3k—喀拉扎组;K1y—亚格列木组;K1sh—舒善河组;K1bx—巴西改组;K1bs—巴什基奇克组;E1-2km—库姆格列木群;E2-3s—苏维依组;N1j—吉迪克组;N1-2k—康村组;N2k—库车组。

Fig.4 Diagram showing strike-slip fault types in the Kuqa depression

图5 库车坳陷逆冲-走滑断层(a-c)和调节走滑断层(d,e)野外照片 a—阿格逆冲-走滑断层带,可见裂缝发育;b—阿格逆冲-走滑断层,沿断层走向断层带宽度变化;c—阿格逆冲-走滑断层带,可见裂缝发育;d—库东调节走滑断层及相关裂缝;e—库东调节走滑断层面。

Fig.5 Field photos of oblique thrust faults (a-c) and high-angle oblique faults (d, e) in the Kuqa depression

图6 库东调节走滑断层控制裂缝发育分布规律图中:x表示距断层距离,m;y表示裂缝密度,m-1;R为相关系数。

Fig.6 Relationship between fracture density and distance to fault by theoretical analysis on nature fractures controlled by the Kudong high-angle oblique fault

表1 有限元数值模拟参数表

Table 1 Parameters used in finite element modeling

地层	ρ/(g·cm^-3)	E/GPa	v	φ/(°)	ψ/(°)	C₀/MPa
N₂k	2.22	10.72	0.25	23	11.50	12.00
N_1-2k	2.25	18.23	0.24	25	12.50	12.80
N₁j	2.25	18.23	0.24	25	12.50	12.80
E	2.08	5.82	0.31	20	10.00	9.80
T-K	2.35	26.62	0.23	32	16.00	16.00
基底	2.40	30.81	0.19	35	17.50	17.00

图7 调节走滑断层滑移量对应变分布的影响数值模拟结果图图中可见滑移量差异部位,应变值较高,是潜在调节走滑断层发育部位,裂缝发育程度高。

Fig.7 Numerical simulation results showing the effect of high-angle oblique fault displacement on strain distribution

表2 库车坳陷断层控制裂缝发育分布效应统计表

Table 2 Calculated fault-controlled fracture coefficient (K) values for oblique thrust faults and thrust faults in the Kuqa depression

断层名称	断层性质	断距或滑距/m	断层强控制裂缝带宽度/m	K
塔拉克断层	逆冲-走滑断层	1 000	150	0.150
阿格断层	逆冲-走滑断层	280	40	0.143
库东断层	调节走滑断层	20	2.5	0.125
阳霞煤矿断层	逆冲断层	1.0	1.5	1.500
吐格尔明断层	逆冲断层	0.5	0.8	1.600
克孜勒努尔沟断层I	逆冲断层	20	30	1.500
克孜勒努尔沟断层II	逆冲断层	15	27	1.800
吐尔力克河断层	逆冲断层	32	50	1.563

图8 库车坳陷复杂构造变形区走滑断层和逆冲断层控制裂缝发育分布模式 a—逆冲断层;b—调节走滑断层;c—逆冲-走滑断层。

Fig.8 Proposed development and distribution patterns of fractures controlled by strike-slip faults and thrust faults in the complex structural deformation zones, Kuqa depression

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