Heterogeneity and differential hydrocarbon accumulation model of deep reservoirs in foreland thrust belts: A case study of deep Cretaceous Qingshuihe Formation clastic reservoirs in southern Junggar Basin, NW China

Using the data of drilling, logging, core, experiments and production, the heterogeneity and differential hydrocarbon accumulation model of deep reservoirs in Cretaceous Qingshuihe Formation(K1q) in the western section of the foreland thrust belt in southern Junggar Basin are investigated. The target reservoirs are characterized by superimposition of conglomerates, sandy conglomerates and sandstones, with high content of plastic clasts. The reservoir space is mainly composed of intergranular pores. The reservoirs are overall tight, and the sandy conglomerate has the best physical properties. The coupling of short deep burial period with low paleotemperature gradient and formation overpressure led to the relatively weak diagenetic strength of the reservoirs. Specifically, the sandy conglomerates show relatively low carbonate cementation, low compaction rate and high dissolution porosity. The special stress-strain mechanism of the anticline makes the reservoirs at the top of the anticline turning point more reformed by fractures than those at the limbs, and the formation overpressure makes the fractures in open state. Moreover, the sandy conglomerates have the highest oil saturation. Typical anticline reservoirs are developed in deep part of the thrust belt, but characterized by "big trap with small reservoir". Significantly, the sandy conglomerates at the top of anticline turning point have better quality, lower in-situ stress and higher structural position than those at the limbs,with the internal hydrocarbons most enriched, making them high-yield oil/gas layers. The exponential decline of fractures makes hydrocarbon accumulation difficult in the reservoirs at the limbs. Nonetheless, plane hydrocarbon distribution is more extensive at the gentle limb than the steep limb.

Characteristics,origin and controlling effects on hydrocarbon accumulation of overpressure in foreland thrust belt of southern margin of Junggar Basin,NW China

Aiming at the differential distribution of overpressure in vertical and lateral directions in the foreland thrust belt in the southern margin of Junggar Basin,the study on overpressure origin identification and overpressure evolution simulation is carried out.Based on the measured formation pressure,drilling fluid density and well logging data,overpressure origin identification and overpressure evolution simulation techniques are used to analyze the vertical and lateral distribution patterns of overpressure,genetic mechanisms of overpressure in different structural belts and causes of the differential distribution of overpressure,and the controlling effects of overpressure development and evolution on the formation and distribution of oil and gas reservoirs.The research shows that overpressure occurs in multiple formations vertically in the southern Junggar foreland thrust belt,the deeper the formation,the bigger the scale of the overpressure is.Laterally,overpressure is least developed in the mountain front belt,most developed in the fold anticline belt,and relatively developed in the slope belt.The differential distribution of overpressure is mainly controlled by the differences in disequilibrium compaction and tectonic compression strengths of different belts.The vertical overpressure transmission caused by faults connecting the deep overpressured system has an important contribution to the further increase of the overpressure strength in this area.The controlling effect of overpressure development and evolution on hydrocarbon accumulation and distribution shows in the following aspects:When the strong overpressure was formed before reservoir becoming tight overpressure maintains the physical properties of deep reservoirs to some extent,expanding the exploration depth of deep reservoirs;reservoirs below the overpressured mudstone cap rocks of the Paleogene Anjihaihe Formation and Lower Cretaceous Tugulu Group are main sites for oil and gas accumulation;under the background of overall overpressure,both overpressure strength too high or too low are not conducive to hydrocarbon enrichment and preservation,and the pressure coefficient between 1.6 and 2.1 is the best.

Simulation for the Controlling Factors of Structural Deformation in the Southern Margin of the Junggar Basin

According to the differences of structural deformation characteristics, the southern margin of the Junggar basin can be divided into two segments from east to west. Arcnate thrust-and-fold belts that protrude to the north are developed in the eastern segment. There are three rows of en echelon thrust-and-fold belts in the western segment. Thrust and fold structures of basement-involved styles are developed in the first row, and decollement fold structures are formed from the second row to the third row. In order to study the factors controlling the deformation of structures, sand-box experiments have been devised to simulate the evolution of plane and profile deformation. The planar simulation results indicate that the orthogonal compression coming from Bogeda Mountain and the oblique compression with an angle of 75° between the stress and the boundary originating from North Tianshan were responsible for the deformation differences between the eastern part and the western part. The Miquan-Uriimqi fault in the basement is the pre-existing condition for generating fragments from east to west. The profile simulation results show that the main factors controlling the deformation in the eastern part are related to the decollement of Jurassic coal beds alone, while those controlling the deformation in the western segment are related to both the Jurassic coal beds and the Eogene clay beds. The total amount of shortening from the Yaomoshan anticline to the Gumudi anticline in the eastern part is -19.57 km as estimated from the simulation results, and the shortening rate is about 36.46%; that from the Qingshuihe anticline to the Anjihai anticline in the western part is -22.01 km as estimated by the simulation results, with a shortening rate of about 32.48%. These estimated values obtained from the model results are very close to the values calculated by means of the balanced cross section.

基于离散元数值模拟的构造变形机制分析方法——以准噶尔盆地南缘为例

受多期构造运动影响,准噶尔盆地南缘前陆冲断褶皱带具横向东西分段、南北分带,纵向构造叠置的变形特征。但该区构造变形机制及样式的不同认识在一定程度上制约了油气勘探的深入。为探究准南缘新生代以来构造变形机制及其变形过程,本文利用高精度地震、钻井和岩石力学等资料,根据实际地质条件,重点考虑滑脱层的数量、强度及厚度变化,结合滑脱层纵向组合、横向分布范围及同沉积作用、先存构造等因素,共设计了10组模型,并采用离散元数值模拟方法开展了对比实验。实验结果表明,滑脱层强度、厚度及其组合主要控制冲断褶皱带构造纵向叠置关系及构造样式,滑脱层分布及同沉积作用主要控制其横向变形范围,先存构造主要影响后期构造的继承性发育。在此基础上,分段开展了多因素组合模拟实验并与实际地震剖面进行对比,重构了准南缘构造变形过程,揭示了新生代以来其构造变形机制,即先存断裂、古凸起、三套不同性质滑脱层纵向叠置关系和同沉积作用共同控制了西段构造的形成与演化,“下强上弱”“下薄上厚”两套纵向叠置滑脱层控制了中段构造的形成与演化,先存断裂及单套较弱滑脱层控制了东段构造的形成与演化。该方法可为类似的复杂构造变形区提供参考。

准噶尔盆地南缘西部山前褶皱—冲断带构造分带特征及形成演化

准噶尔盆地南缘西部构造呈新的构造叠置特征和复杂的复合叠加构造样式,叠加构造在空间分布上具有明显的分带特征。根据野外地质调查和地震解释资料,采用平衡剖面恢复、楔型构造理论和构造地质学分析方法,研究复杂叠加构造变形差异及分带特征。结果表明:准噶尔盆地南缘西部发育受基底卷入与顺层滑脱联合与差异控制下的空间断褶体系,褶皱发育受断层控制,褶皱与断层相互叠加形成构造楔、双重构造、突发构造等复合构造样式,表现为多期活动特征。研究区按构造变形性质及变形差异可划分为山前逆冲推覆构造带、基底卷入型褶皱—冲断带、盖层滑脱型褶皱—冲断带3个构造带;其中,基底卷入型褶皱—冲断带与第一排断褶带重合,受控于基底卷入型断裂体系,发育基底卷入式大型构造楔、背形堆垛式双重构造与前倾双重构造,背斜轴线与断层线平面重合度高;盖层滑脱型褶皱—冲断带包括第二和第三排断褶带,受控于顺层滑脱型断裂体系,发育断展褶皱,背斜轴线与断层线平面重合度低,构造垂向上具有分层差异,构造变形程度自南向北表现为由强至弱。挤压应力作用的时期和强度、滑脱断层的向北滑脱、构造楔的楔入长度及推挤距离、滑脱层的厚度和上覆地层厚度,以及沉积时代、沉积速率和岩性差异等因素是引起研究区构造垂向分层、南北分带的原因。该结果对明确研究区构造发育及下一步油气地质勘探具有指导意义。

准噶尔盆地四棵树凹陷多期应力场作用下的构造演化特征

准噶尔盆地南缘四棵树凹陷位于北天山山前冲断带西段,盆地自古生代以来经历了多期、多向的构造运动;明确研究区构造系统特征及其演化过程,对此类含油气盆地的油气勘探开发具有重要意义。在前人地质研究的基础上,结合详细的地震资料解释、地质调查与地层发育特征,根据研究区构造发育背景,以四棵树凹陷构造格局的变动和多期应力场为线索,对四棵树凹陷构造演化过程进行了系统性分析。研究表明,四棵树凹陷深部发育挤压反转-走滑构造层、浅部发育推覆-滑脱构造层;平面上根据构造样式发育特征可划分为南部挤压断褶带、中部走滑压扭带、北部隆起带;凹陷经历了2期强烈的构造隆升期,对应2期断裂活动高峰期;构造环境及应力场条件发生了多次转变,晚石炭世至早中二叠世为弧后裂陷背景下的NNW-SSE向伸展裂陷期、晚二叠世至三叠纪为扎伊尔山造山运动下NNW-SSE向挤压的断坳转换期、晚侏罗世至古近纪为周缘造山带与车排子凸起的共同作用下NNW-SSE向挤压陆内坳陷期、新近纪为北天山强烈的造山活动背景下NS向挤压作用的复活前陆盆地期。通过探讨多期应力场作用下四棵树凹陷的构造演化特征,进一步深入认识了此类含油气盆地整体构造格局的变动过程,也为研究区油气资源下一步勘探提供了新思路。

Structural analysis of multi-level detachments and identification of deep-seated anticline

Based on forward modeling of detachment fold, this study presents a method to analyze multi-level detachment structures and identify the authenticity of deep-seated anticlines using time-domain seismic section. The steps include the conversion of the time-migrated seismic image into depth domain image using a constant velocity field, structural interpretation of the depth seismic image, measurement of each structural relief area and each height above reference level, plotting of area-height relationship chart with piecewise fitting etc. The area-depth correlation can help the division of structural sequences, the definition of detachment levels, the calculation of the tectonic shortening, and the identification of deep-seated structure. The segment area-height relationship is a feature of multi-level detachment structures, while little or no linear correlation between area and height is an indicator of non-deformation or pseudo-anticline. Regardless of the uncertainty of area-height relationship, the segment slopes will correspond to the differential shortenings of multi-level detachments, the intersection between adjacent segments will give the height of detachment surface above reference level and then help define the detachment level in original time-domain seismic section. This method can make use of time-domain seismic data to determine the geologic structure of complicated structure areas and assess risks of deep exploration targets. It has achieved good results in southern Junggar and eastern Sichuan areas.

层间逆冲叠瓦构造-前陆冲断带大气区控藏模式

为了揭示中国中西部盆地前陆冲断带大气藏(大气区)的控藏模式,综合运用地质、地震、钻井及测井等资料,精细断裂解释,研究构造样式,分析成藏条件,特别是通过解剖塔里木盆地库车、准噶尔盆地准南和四川盆地西缘前陆冲断带已发现的大气藏,构建了前陆冲断带大气区控藏模式,并取得以下认识:(1)根据逆冲断裂发育的几何性质、与盖层和烃源岩的关系,特别是对圈闭以及成藏的控制,将前陆冲断带逆冲构造分为层间逆冲、上下穿透型逆冲、上穿透型逆冲、下穿透型逆冲4种构造样式。(2)层间逆冲构造是控制形成大气藏的主要构造样式。层间逆冲断层向下断至烃源岩,在烃源岩内逆掩形成天然缝网系统,构成优势运移通道,向上断至盖层而未断穿,即沟通油气源又未破坏圈闭的有效性,最有利于形成大气藏。(3)前陆冲断带往往发育成排成带层间逆冲断层相关背斜,具有相同的构造样式和成藏条件,从而形成连片分布的大气区。(4)大气藏(大气区)主要分布在前渊地区。

前陆冲断带深层储集层非均质性及油气差异聚集模式——以准噶尔盆地南缘西段白垩系清水河组碎屑岩储集层为例

基于钻井、测井、岩心及实验数据和油气生产资料,对准噶尔盆地南缘前陆冲断带西段深层白垩系清水河组储集层非均质性及其油气差异聚集模式进行研究。结果表明:(1)储集层以叠置连片的砾岩、砂砾岩及砂岩为特征,塑性岩屑含量高,储集空间以粒间孔为主,整体致密,其中砂砾岩物性最优;(2)较短的深埋时限匹配较低的古地温梯度和地层超压使得储集层整体成岩强度较弱,而砂砾岩具有相对更低的早期碳酸盐胶结及压实率和更高的溶蚀增孔;(3)背斜特殊的应力-应变机制使得转折端顶部储集层可较两翼宏观裂缝改造程度更大,且超压使得裂缝处于开启状态;(4)砂砾岩相对含油饱和度最高,而冲断带深层发育典型背斜油气藏,但整体表现为“大圈闭,小油藏”的特点;(5)背斜转折端顶部砂砾岩相较于两翼具有更优越的储集性能、更低的地应力大小及较高的构造位置,使得内部油气最为富集而成为高产油气层,而裂缝指数级递减使得两翼储集层难以富集成藏,但背斜缓翼相对陡翼油气平面延伸范围更大。

准噶尔盆地南缘新生代构造演化研究进展

新生代印度-欧亚板块碰撞的远程效应是理解中亚构造格局变化的主要机制。随着其远程效应的北移,位于中亚腹地的准噶尔盆地在周边山脉抬升的影响下,南北缘发生构造活动。基于前人的研究成果,将盆地新生代以来的构造演化概括如下:古新世,因基底断裂复活,盆地北部开始发生逆冲推覆活动;渐新世末期,博格达山脉恢复隆升,古牧地背斜发生构造变形;中新世以来,盆地南缘逐渐形成了三排构造带;上新世末期—更新世以来,北部基底断裂活动,南缘西段和东段分别形成浅层背斜和断裂。目前,由于印度-欧亚板块碰撞远程效应的传播模式仍处于探索阶段,因此需要更多的地质证据来证实它在不同阶段的传播方式以及使盆地发生构造变形的机制。

准噶尔盆地西北缘前陆冲断带二叠纪逆冲断裂活动的沉积响应

笔者从 16 0口单井剖面、15条联井剖面及 5个层位平面渐次展开了准噶尔西北缘前陆冲断带二叠纪逆冲断裂活动的沉积响应研究。各种成因扇体 (冲积扇、水下扇、扇三角洲 )在佳木河组和上乌尔禾组地层中最为发育 ,其沉积分布严格受不同时期活动的同生断裂控制。由早二叠世佳木河期至晚二叠世上乌尔禾期 ,扇体在克拉玛依—夏子街地区叠置程度较好 ,由盆缘向盆内迁移、推进明显 ;在车排子—中拐地区叠置程度相对较差 ,局部略呈向盆缘老山收缩、后退趋势 ,表明红山嘴 -车排子断裂带与克拉玛依 -百口泉断阶带、乌尔禾 -夏子街断褶带逆冲活动的强度及地域迁移性有明显差异。二叠纪总体为一由弱到强的前展式推覆冲断及渐进式扇体迁移模式 ,即随同生控扇断裂由老山向盆缘的前展式推覆活动 ,相应地 ,各构造带扇体逐渐由盆缘向盆地方向发育、推进 ,扇体面积不断扩大 ,显示出明显的渐进式迁移的沉积响应 ,两者形成良好的耦合性。进而引入“活动性指数”的概念与方法 ,对前陆冲断带同生断裂的冲断活动强度进行了定量化统计分析 ,据二叠纪冲断推覆事件的地层、沉积标识 ,识别出 3个逆冲推覆幕、7个逆冲推覆事件 ,划分出 P1 j— P1 f、P2 x— P2 w、P3w三套构造层序 ,并指出在 P1 f、P2 x及P2 + 3w各时期 ,由红山嘴 -车?

准噶尔西北缘前陆冲断带三叠纪—侏罗纪逆冲断裂活动的沉积响应

笔者从冲断活动的产物———各种成因扇体(冲积扇、水下扇、扇三角洲)出发,由160口单井剖面、15条联井剖面、8个层位平面渐次展开了准噶尔西北缘前陆冲断带三叠—侏罗纪逆冲断裂活动的沉积响应研究。三叠纪扇体在乌尔禾—夏子街地区发育叠置程度最好,T1b到T3b,其由盆内向盆缘老山方向退缩迁移明显,并具T1b到T2k1由盆缘向盆内、T2k2到T3b由盆内向盆缘迁移的2个进退波动变化。侏罗纪扇体在八道湾组最为发育,总体叠置关系较差,J1b到J2t,均呈由盆内向盆缘老山退缩沉积的退覆式迁移特征。三叠纪到侏罗纪,总体为由强到弱的退覆式冲断活动及扇体迁移模式,即随主要同生控扇断裂分布由盆缘向老山方向退缩迁移,冲断活动强度由盆缘向盆地方向逐渐减弱直至停息;相应地,各期扇体平面上分布规模渐小,总体呈由盆内向盆缘老山退缩迁移的沉积响应,两者耦合性良好。各类扇体的沉积分布受不同时期同生断裂活动的严格控制,其时空叠置及迁移规律的差异是红山嘴—车排子、克拉玛依—百口泉及乌尔禾—夏子街各构造带冲断作用地域性及作用强度差异性的沉积响应。进而引入“活动性指数”的概念与方法,对前陆冲断带同生断裂的冲断活动强度进行了定量化统计分析,并根据冲断推覆事件的地层、沉积标识划分出T1b-T3b、J1b-J2x、J2t三套构造层序,识别出三叠—侏罗纪的3个逆冲推覆幕、6次逆冲推覆事件。

天山南缘与北缘前陆冲断带构造地质特征对比及油气勘探建议

在区域构造、盆地演化与沉积充填特征分析的基础上,对天山南、北缘地震大剖面进行了精细构造变形几何学与年代学的解析。揭示出中—新生代以来天山南、北缘虽然具有相似的构造演化过程、沉积充填特征和油气地质条件,但是受沉积地层介质的力学性质差异和印—藏碰撞远距离效应的空间位置差异的影响,天山南、北缘新生代构造变形启动的时间与构造变形样式存在明显的差异,并在一定程度上导致油气聚集的不同。新生代天山隆升并向两侧扩展,冲断构造沿滑脱层向克拉通盆地内传播,构造形成的时间从造山带向克拉通方向依次变晚。库车前陆冲断带的构造变形时间早于准南,因此库车冲断带内构造圈闭的油气充注时间长、充满程度高,容易形成高丰度大型气藏。库车冲断带盐下发育多个切过中生界煤系烃源岩的逆冲断层,它们不仅控制了多个褶皱侧向上台阶状叠置,形成盐下堆垛的构造样式,而且成为深部中生界油气向浅层运移聚集的通道;膏盐岩保证了盐下构造圈闭的完整性和封盖条件。准南冲断带主要的构造变形样式是层间滑脱与构造位移量反向冲断的楔形构造,水平滑脱断层封隔了上、下含油气系统,限制深部油气向中浅层运移;大型背斜内部发育多个小型叠置的楔形构造,破坏了构造圈闭的完整性。因此准南山前东端隐伏的燕山期古构造与二、三排新生代构造核部以及库车秋里塔格西段中生界印支期古构造和克拉苏—依奇克里克新生代较早形成的构造带是成藏的有利部位;库车盐下储盖组合是油气富集的有效构造层,准南深层中生界中的大型、完整的构造圈闭是油气勘探大突破的场所。

前陆冲断带构造分段特征——以准噶尔盆地西北缘断裂构造带为例

前陆冲断带普遍具有构造分段的特点。横断层、侧断坡与斜断坡常是构造分段的边界 ,它们起着运动方向、变形速率、构造样式与成因机制转换的作用。准噶尔西北缘前陆冲断带是古生代晚期—中生代早期发展起来的大型冲断推覆系统 ,南自车排子 ,北至夏子街、红旗坝的大型断裂带为其冲断前锋断裂。由于形成时间、活动方式与受力条件等出现变化 ,车排子—夏子街断裂带被北西向的横断层分割为构造样式与地质结构截然不同的三段 ,南段为红山嘴—车排子断裂带 ,构成车排子断隆的东部逆冲边界 ;中段为具压扭性质的克拉玛依—百口泉断裂带 ;北段为具冲断推覆性质的乌尔禾—夏子街断裂带。中生代晚期—新生代以来该前陆冲断带被稳定埋藏 。

准噶尔盆地南缘前陆冲断带油气成藏差异性分析

准噶尔盆地南缘前陆冲断带构造演化与成藏过程复杂。为深化对这种复杂性的认识,以给区域油气勘探和基础石油地质研究提供参考信息,针对区域构造上存在东西分段、南北分带的特点,从不同角度详细分析了不同区段油气成藏的特征及其差异,包括烃源、储层、圈闭、输导、保存、成藏模式和主控因素。结果表明,不同区段的油气藏分布层位和成藏特征均不同,展示出油气成藏的差异性。其中,东段阜康断裂带主要是二叠系(包括侏罗系)的油气聚集于侏罗系储层中,成藏主控因素是圈闭、保存条件和储层;中段山前冲断带主要是侏罗系和二叠系(包括白垩系)的油气聚集于古近系和白垩系储层中,成藏主控因素是烃源岩、油源断裂和储层;西段四棵树凹陷地区主要是侏罗系(包括古近系)的油气聚集于古近系—新近系和白垩系储层中,油气成藏主控因素是运移通道和储层条件。

准噶尔盆地南缘褶皱-冲断带变形特征及成因机制模拟

准噶尔盆地南缘褶皱-冲断带发育于北天山和博格达山北侧的准噶尔盆地南部的山前地区,构造变形具有明显的横向分带、纵向分段、垂向分层特征,其主控因素在于挤压应力的作用方式和滑脱层的空间分布规律。西段受北天山斜向挤压应力作用影响,发育北西西向四排雁列式褶皱-冲断带,构造变形样式为基底卷入式厚皮构造和盖层滑脱式薄皮构造,变形过程受侏罗系煤层和白垩系、古近系高塑性泥岩层等多滑脱层控制。滑脱层及其上覆岩层厚度决定变形的强度和应力向前传递的远近程度,厚度越大,褶皱变形强度越大。东段受博格达山正向楔冲挤压应力作用影响,发育近东西向向北凸出的弧形基底卷入式褶皱-冲断带,滑脱构造不发育。根据构造变形特征和相似理论,利用沙箱模拟实验分别对正向挤压和15°、30°、45°等斜向挤压平面变形进行了模拟,结果表明正向挤压和15°斜向挤压是形成东段和西段变形特征的主控应力条件,并设计了斜向和正向挤压组合边界平面模拟实验进行了验证,合理地解释了东、西段构造变形的差异。利用双滑脱层剖面模型实验对西段四排褶皱-冲断带的演化过程进行了模拟再现。

准噶尔盆地西北缘下盘掩伏构造油气勘探新领域

准噶尔盆地西北缘冲断构造自西向东由北部单斜带、中部向斜带、克—乌断裂带和前缘斜坡带4个部分组成,在纵向又可划分为上、下两个构造层,上构造层的冲断序列要先于下构造层。现今保存下来的冲断构造应始于三叠纪末期形成,并在侏罗纪继承性活动,白垩纪之后冲断活动基本停止。西北缘冲断带下构造层内的背斜圈闭和"帽檐"式圈闭是油气勘探前景很大的新领域,尤其是大侏罗沟横向断裂与克—乌断裂带夹持的三角区域,"帽檐"圈闭埋藏适中,是一个有利的勘探目标。应在获得必要的深部地质资料和速度资料后,再针对保存完整、面积和幅度均较大的下盘掩伏背斜开展地震处理攻关与解释成图。

准噶尔盆地南缘褶皱-逆冲断层带分析

讨论了与准噶尔盆地南缘褶皱-逆冲断层带有关的4个问题。(1)准噶尔盆地南缘褶皱-逆冲断层带具有纵向分带、横向分段和垂向构造分层的特征:纵向上由南至北可分为逆冲推覆构造带、基底卷入褶皱-冲断带和滑脱型褶皱-冲断带三个带;横向上,基底卷入褶皱-冲断带从西至东按横向调节带分为5个段,构造特征表现为反冲断层从不发育到向南反冲的位移逐渐增大、反冲断层所滑脱的层位亦逐渐加深;滑脱型褶皱-冲断带以红车断裂为界划分为西段和东段,西段构造运动弱,构造变形具双层结构;东段构造运动较强,发育大型冲向后陆的反向逆冲断层,构造变形多具有3层结构。(2)逆冲断层-褶皱类型按其形成机制分为基底卷入型冲断-褶皱、滑脱型冲断-褶皱以及基底卷入-滑脱混合型冲断-褶皱3大类,其中,基底卷入型冲断-褶皱的特征是褶皱作用发生在逆冲断裂之前,而滑脱型冲断-褶皱以冲断和褶皱同时或冲断层先于褶皱形成为特征。(3)本区存在横向和纵向传递带。横向调节带一般分布于基底卷入型褶皱-冲断带,主要为左旋走滑断层;纵向传递带分布于滑脱型褶皱-冲断带,以逆冲断层系斜列分布和位移纵向斜列传递为特征。(4)褶皱-冲断带形成的主控因素主要有:近南北向的水平挤压作用,上新世末—早更新世末和晚侏罗世末发生的构造变形以及古近系、下白垩统和下—中侏罗统发育的三套异常高压泥岩层相关的滑脱作用。

准噶尔盆地西北缘走滑断层特征及油气地质意义

准噶尔盆地西北缘前陆冲断带构造样式复杂多样,除规模较大的逆断层外,还发育一系列北西向的走滑断层。以高分辨率三维地震资料为基础,对断裂体系分析表明克拉玛依—百口泉地区的走滑断层可分为花状走滑断层和简单走滑断层两类,二者在成因、剖面特征等方面具有明显差别。研究结果认为走滑断层对油气的运聚成藏具有重要的双重控制作用,即能作为有效的运移通道,又能够起遮挡作用而形成圈闭。

酒泉盆地南缘新生代冲断带的变形特征和变形时间

酒泉盆地南缘冲断带具有多层次的逆冲结构,包括浅层的远距离冲断系统、中层的近距离冲断系统和深层的原地冲断系统。远距离冲断系统由奥陶系和志留系构成,局部地区表现为飞来峰;近距离冲断系统由古生界和中生界构成,大部分隐伏在远距离冲断系统之下,局部地带以构造窗的形式出露地表,其变形样式主要为叠瓦状的冲断变形;原地冲断系统隐伏在近距离冲断系统和第四系之下,其南部的变形主要表现为双冲构造或堆垛构造,往NE方向变形逐渐简单,主要表现为断层传播褶皱和断层弯曲褶皱,前锋地带表现为三角带的突起构造。酒泉盆地南缘冲断带的变形是一个具有大缩短量的薄皮冲断系统,旱峡剖面的构造缩短量为52.7 km,缩短率为55.1%。酒泉盆地南缘冲断带的变形时期大致开始于9.0 M a,并以“前展式”向北扩张,变形时间向北变新,前锋断层开始活动时间约为8.3 M a。