Three-dimensional structural models,evolution and petroleum geological significances of transtensional faults in the Ziyang area,central Sichuan Basin,SW China

With drilling and seismic data of Transtensional(strike-slip)Fault System in the Ziyang area of the central Sichuan Basin,SW China plane-section integrated structural interpretation,3-D fault framework model building,fault throw analyzing,and balanced profile restoration,it is pointed out that the transtensional fault system in the Ziyang 3-D seismic survey consists of the northeast-trending F_(I)19 and F_(I)20 fault zones dominated by extensional deformation,as well as 3 sets of northwest-trending en echelon normal faults experienced dextral shear deformation.Among them,the F_(I)19 and F_(I)20 fault zones cut through the Neoproterozoic to Lower Triassic Jialingjiang Formation,presenting a 3-D structure of an“S”-shaped ribbon.And before Permian and during the Early Triassic,the F_(I)19 and F_(I)20 fault zones underwent at least two periods of structural superimposition.Besides,the 3 sets of northwest-trending en echelon normal faults are composed of small normal faults arranged in pairs,with opposite dip directions and partially left-stepped arrangement.And before Permian,they had formed almost,restricting the eastward growth and propagation of the F_(I)19 fault zone.The F_(I)19 and F_(I)20 fault zones communicate multiple sets of source rocks and reservoirs from deep to shallow,and the timing of fault activity matches well with oil and gas generation peaks.If there were favorable Cambrian-Triassic sedimentary facies and reservoirs developing on the local anticlinal belts of both sides of the F_(I)19 and F_(I)20 fault zones,the major reservoirs in this area are expected to achieve breakthroughs in oil and gas exploration.

Tectonic features,genetic mechanisms and basin evolution of the eastern Doseo Basin,Chad

The features of the unconformity,fault and tectonic inversion in the eastern Doseo Basin,Chad,were analyzed,and the genetic mechanisms and basin evolution were discussed using seismic and drilling data.The following results are obtained.First,four stratigraphic unconformities,i.e.basement(Tg),Mangara Group(T10),lower Upper Cretaceous(T5)and Cretaceous(T4),four faulting stages,i.e.Barremian extensional faults,Aptian–Coniacian strike-slip faults,Campanian strike-slip faults,and Eocene strike-slip faults,and two tectonic inversions,i.e.Santonian and end of Cretaceous,were developed in the Doseo Basin.Second,the Doseo Basin was an early failed intracontinental passive rift basin transformed by the strike-slip movement and tectonic inversion.The initial rifting between the African and South American plates induced the nearly N-S stretching of the Doseo Basin,giving rise to the formation of the embryonic Doseo rift basin.The nearly E-W strike-slip movement of Borogop(F1)in the western section of the Central African Shear Zone resulted in the gradual cease of the near north-south rifting and long-term strike-slip transformation,forming a dextral transtension fault system with inherited activity but gradually weakened in intensity(interrupted by two tectonic inversions).This fault system was composed of the main shear(F1),R-type shear(F2-F3)and P-type shear(F4-F5)faults,with the strike-slip associated faults as branches.The strike-slip movements of F1 in Cretaceous and Eocene were controlled by the dextral shear opening of the equatorial south Atlantic and rapid expanding of the Indian Ocean,respectively.The combined function of the strike-slip movement of F1 and the convergence between Africa and Eurasia made the Doseo Basin underwent the Santonian dextral transpressional inversion characterized by intensive folding deformation leading to the echelon NE-SW and NNE-SSW nose-shaped uplifts and unconformity(T5)on high parts of the uplifts.The convergence between Africa and Eurasia caused the intensive tectonic inversion of Doseo Basin at the end of Cretaceous manifesting as intensive uplift,denudation and folding deformation,forming the regional unconformity(T4)and superposing a nearly E-W structural configuration on the Santonian structures.Third,the Doseo Basin experienced four evolutional stages with the features of short rifting and long depression,i.e.Barremian rifting,Aptian rifting–depression transition,Albian–Late Cretaceous depression,and Cenozoic extinction,under the control of the tectonic movements between Africa and its peripheral plates.

Formation and evolution of the strike-slip faults in the central Sichuan Basin, SW China

Based on 3D seismic and drilling data, the timing, evolution and genetic mechanism of deep strike-slip faults in the central Sichuan Basin are thoroughly examined by using the U-Pb dating of fault-filled carbonate cement and seismic-geological analysis. The strike-slip fault system was initially formed in the Late Sinian, basically finalized in the Early Cambrian with dextral transtensional structure, was overlaid with at least one stage of transpressional deformation before the Permian, then was reversed into a sinistral weak transtensional structure in the Late Permian. Only a few of these faults were selectively activated in the Indosinian and later periods. The strike-slip fault system was affected by the preexisting structures such as Nanhuanian rifting normal faults and NW-striking deep basement faults. It is an oblique accommodated intracratonic transfer fault system developed from the Late Sinian to Early Cambrian to adjust the uneven extension of the Anyue trough from north to south and matches the Anyue trough in evolution time and intensity. In the later stage, multiple inversion tectonics and selective activation occurred under different tectonic backgrounds.

Origin and growth mechanisms of strike-slip faults in the central Tarim cratonic basin, NW China

Through fault structure analysis and chronology study, we discuss the origin and growth mechanisms of strike-slip faults in the Tarim Basin.(1) Multiple stages strike-slip faults with inherited growth were developed in the central Tarim cratonic basin. The faults initiation time is constrained at the end of Middle Ordovician of about 460 Ma according to U-Pb dating of the fault cements and seismic interpretation.(2) The formation of the strike-slip faults was controlled by the near N-S direction stress field caused by far-field compression of the closing of the Proto-Tethys Ocean.(3) The faults localization and characteristics were influenced by the pre-existing structures of the NE trending weakening zones in the basement and lithofacies change from south to north.(4) Following the fault initiation under the Andersonian mechanism, the strike-slip fault growth was dominantly fault linkage, associated with fault tip propagation and interaction of non-Andersonian mechanisms.(5) Sequential slip accommodated deformation in the conjugate strike-slip fault interaction zones, strong localization of the main displacement and deformation occurred in the overlap zones in the northern Tarim, while the fault tips, particularly of narrow-deep grabens, and strike-slip segments in thrust zones accumulated more deformation and strain in the Central uplift. In conclusion, non-Andersonian mechanisms, dominantly fault linkage and interaction, resulted in the small displacement but long intraplate strike-slip fault development in the central Tarim Basin. The regional and localized field stress, and pre-existing structures and lithofacies difference had strong impacts on the diversity of the strike-slip faults in the Tarim cratonic basin.

Large Active Faults and the Wharton Basin Intraplate Earthquakes in the Eastern Indian Ocean

In recent years,great earthquakes occurred within the Wharton Basin in the eastern Indian Ocean,and they have been associa-ted with active faulting on the ancient oceanic crust.Large seismogenic faults were thought to be the fault reactivation on the ancient oceanic crust,but these phenomena are still unclear and require examination.This study used high-quality multibeam bathymetry and multichannel seismic data collected over the northern Ninetyeast Ridge to investigate detailed fault geometry,structure,and activity.We recognized 12 large linear active faults by integrating bathymetry maps and multichannel seismic reflection profiles.Our results showed that these faults have high angles,and they all displaced the basement and propagated to the seafloor with distinct fault scarps.They trended NWW-SEE with a spacing of 10–40km and were parallel to each other and the nearby subfault of the 2012 great intraplate earthquake,suggesting similar stress fields.These faults are also in agreement with the orientations of magnetic isochrons,implying their formation by seafloor spreading.Furthermore,regarding the strike-slip focal mechanism of 2012 earthquakes,we proposed that these faults were created early by a normal spreading process and then evolved into a strike-slip pattern since the ancient oceanic crust ap-proached the subduction zones.

塔里木新元古代裂谷盆地基底结构与演化

沉积盆地基底结构与演化是盆地动力学研究的重要内容,针对塔里木板块新元古代变质基底与裂谷盆地成因机制问题,综合新元古代年代学与地球化学资料研究其基底结构、构造环境与演化.结果表明,南、北塔里木地块拼合于1.9~1.8 Ga,早新元古代沉积岩系与古元古代火成岩系于780~750 Ma形成统一的变质基底,并经历多期构造-热事件作用形成南北差异的复杂变质基底结构.新元古代具有950~900 Ma、860~840 Ma、830~800 Ma、780~760 Ma的多期前展式俯冲作用,760~720 Ma、670~610 Ma的多期后撤俯冲作用,形成了转换期在约760 Ma的前展-后撤俯冲构造旋回.新元古代前展式俯冲控制了变质基底的演变,后撤俯冲控制了大陆裂谷盆地的演化,具有不同于经典威尔逊旋回的成盆动力学机制与演化过程.

塔里木盆地塔中隆起中北部地区断裂构造特征及演化

为系统揭示塔里木盆地塔中隆起中北部地区断裂构造特征及其成因演化,通过对该区大连片三维地震工区精细构造解析和相干体等分析,并结合区域动力背景,系统论述了该区的断裂构造类型、几何学特征、差异活动机制及其构造演化过程。研究结果表明,塔中隆起中北部发育了4类7期断裂构造,其中逆冲断裂和走滑断裂尤其发育。平面上北西向弧形逆冲断裂与北东向、北西向及南北向走滑断裂相互交切与耦合;垂向上断裂分层差异活动特征明显,下奥陶统及其以下地层,断裂发育数量多且以线形为主,中奥陶统-中下泥盆统多呈雁列式,上泥盆统-二叠系仅在塔中Ⅱ号断裂带、顺北5号断裂带西南端等地区发育少量断裂。研究区断裂活动受多期、多方向不同性质应力场所控制,经历了极其复杂的演化历史:加里东早期以塔中Ⅱ号断裂带等少量北倾正断层活动为主;加里东中期Ⅰ幕断裂活动强烈,表现为逆冲断裂与走滑断裂协同演化和相互耦合特征,走滑断裂对逆冲断裂的切割或限制作用明显;加里东中期Ⅲ幕断裂活动基本继承了加里东中期Ⅰ幕的构造格局,但在工区北部的顺北4号、5号等断裂带张扭性断裂活动特征显著;加里东晚期-海西早期,部分断裂发生继承性活动且张扭断裂发育范围进一步向南扩大;印支-燕山期,仅有少数断裂发生继承性活动;喜山期该区构造比较稳定,早期形成的复杂断裂构造进入深埋阶段。

哈拉哈塘地区共轭走滑断裂差异特征及演化

塔里木盆地哈拉哈塘地区发育非典型X型共轭走滑断裂,具有分区、分层、分段差异性及差异演化特征,制约了油气勘探开发。以哈拉哈塘地区3400km^(2)三维地震为基础,通过详细解析NE向和NW向两条走滑断裂分层及分段特征,分析其差异演化特征,推测其成因机制。结果表明:1)从北向南,断裂成熟度与延伸性变弱,NE向断层扰动增强;从深至浅,NW向断层对北东向干扰越来越弱,NE向断层则此消彼长;NW向断层变形程度与成熟度由深至浅变低,而NE向断层向上变形程度增强。2)哈拉哈塘地区走滑断层具有多期活动特征,可以划分为中奥陶世共轭断裂形成阶段、石炭-二叠纪张扭走滑断裂活化阶段及中-新生代张扭走滑断层活动阶段,不同方向走滑断裂演化有差异。3)不同时期断层的成因机制有所差异,中奥陶世走滑断裂受控于纯剪和单剪的叠加变形,并受控应力场、先存构造以及区域厚度等影响,自北向南应力的衰减及其相应的应力场变化造成南北断裂样式的差异性。

冀中坳陷南部中—新生代构造转换及其油气地质意义

为了分析冀中坳陷南部中—新生代构造转换机制及其与油气分布的关系,基于地震解释资料,对该区地质结构特征、构造演化及构造转换过程进行研究,并对其油气地质意义进行了探讨。结果表明:冀中坳陷南部衡水调节带两侧地质结构存在明显差异,北部为“双断-双向滑脱-背倾半地堑”结构,南部为“多断-单向滑脱-复式半地堑”结构;冀中坳陷南部地区中—新生代构造演化大致分为基底演化(中生代)、初始裂陷演化(孔店组—沙四段沉积时期)、强裂陷演化(沙三段—沙二段沉积时期)、弱裂陷演化(沙一段—东营组沉积时期)及后裂陷演化(馆陶组沉积时期以来)5个阶段;冀中坳陷南部经历了基底NNE向构造体系向新生代NE向构造体系的转换,区域中—新生代以来应力场变化是冀中坳陷多方位复杂构造形成的原因;冀中坳陷南部构造转换作用通过影响洼槽迁移进而影响有效烃源岩分布,通过控制砂体入盆通道影响储层砂体展布,构造变换过程中主干断层位移梯度变化导致横向背斜形成指示油气富集的有利部位。构造体制转换形成的不同规模变换构造具有一定勘探潜力。

新疆准噶尔盆地西北缘克拉玛依-乌尔禾断裂带推覆体上盘构造样式及影响因素

准噶尔盆地西北缘克拉玛依-乌尔禾断裂带(克-乌断裂带)及其周缘发现了大量的油气藏,尤其是推覆体上盘伴随着勘探程度及地质认识不断深化,已呈现出“百里油区”的态势。然而,受多期构造活动及断裂带内部复杂的岩性组合影响,石炭系内幕地层构造样式展现出多种类型及复杂的空间展布样式,因此需要对构造样式及成因进一步探讨。综合地震和钻井资料,结合区域构造格局,梳理了准噶尔盆地西北缘克-乌断裂带上盘构造变形特征与影响因素;根据构造样式与推覆体内的岩性组合类型,将克-乌断裂带推覆体上盘划分出南段、中段和北段3个变形单元;明确了上盘石炭系5期主要构造阶段,分段恢复了推覆体上盘构造演化期次及样式。综合上述研究,认为克-乌断裂带上、下盘原始岩性组合关系是造成上盘石炭系内幕地层原始形变差异的主要因素,上盘石炭系内幕地层岩性组合差异是造成原生构造保存的主要因素。上述因素共同造成了圈闭条件沿克-乌断裂带自南向北变化。该研究为克-乌断裂带上盘油气勘探提供指导,同时也为类似条件地区的油气勘探提供借鉴。

塔里木盆地台盆区走滑断裂带多层叠加样式及石油地质意义

随着塔里木盆地油气勘探的不断深入,在台盆区古生界发现大规模走滑断裂系统,提出了一种新型断溶体油气藏。受塔里木盆地多期构造运动的影响,走滑断裂表现出多层结构,具有多期叠加活动特征。基于高品质三维地震资料、钻井资料及油气地质资料,对塔里木盆地大型走滑断裂的多层叠加特征及对油气的控制作用展开研究。研究结果表明:塔里木盆地台盆区走滑断裂带在古生界主要发育5个结构层,分别为下寒武统盐下构造层、中寒武统盐构造层、上寒武统—中奥陶统碳酸盐岩构造层、上奥陶统—石炭系碎屑岩构造层和二叠系岩浆岩构造层;受多期构造运动及走滑断裂带活动的影响,5层结构在空间上具有带状分布、垂向叠置、差异叠加的特征;断裂叠加类型多样,总体上可以分为连接型、叠接型、反转叠加型及反转改造型4种;走滑断裂带叠加方式影响了石油地质条件,可形成多层差异聚集油气藏,主要包括Ⅰ型油气藏(奥陶系碳酸盐岩油气藏)、Ⅱ型油气藏(奥陶系碳酸盐岩油气藏、志留系碎屑岩油气藏及二叠系岩浆岩油气藏)及Ⅲ型油气藏(寒武系盐下层白云岩油气藏)3种类型。

松辽盆地敖古拉断裂带构造演化及断控油气聚集机制

松辽盆地敖古拉断裂带呈现出复杂的运动学特征,各成藏主控要素时空匹配关系研究难度大,为油藏形态精准刻画带来了挑战。针对该问题,综合地质、地震解剖和钻井资料分析,梳理构造发育史及断裂成因,并在成藏认识的基础上,明确断裂控制油气富集的机制。研究区断裂密集带可划分为2个级别,并根据断层与层位切割关系将断层分为3类。研究表明:敖古拉断裂带由2条反“S”形主干断裂组成,历经断陷期、坳陷期以及反转期3个阶段;断陷期断裂带活动强度与伸展率最大,坳陷期逐渐减弱,伴生多条反向调节断层,反转期断层活动强度与伸展率再次增强;油源断层是沟通烃源岩和圈闭的垂向运移通道,控制了与断层相关圈闭的形成,为油气运移、聚集提供了有利条件。研究结果能够为进一步寻找有利勘探目标及增储上产提供理论依据。

四川盆地南部泸州—云锦地区走滑断裂构造变形特征

以多重滑脱褶皱冲断构造为主要变形的泸州—云锦地区同样发育走滑断裂。逆冲构造和走滑断裂的分类、分期厘定对于重新认识泸州—云锦地区的断裂系统具有重要意义。以泸州—云锦地区的高精度三维地震数据、钻测井数据为基础,通过平面—剖面结合精细构造解析和井—震标定分析,获得如下认识:1)北东向、北西向、近南北向等不同走向、不同级别的逆断层和褶皱带叠加、复合变形,构成了泸州—云锦地区网状的多重滑脱冲断褶皱构造变形系统。2)区内主要发育4条走滑断裂带,断层对关键界面的改造呈现出微小伸展地堑的变形特征,在剖面上则主要表现出“Y”字形负花状构造的变形样式。其中,蜀南1号走滑断裂带近南北走向,在左旋剪切作用下形成;蜀南2号、3号走滑断裂带由多条次级断层带或小型正断层左阶斜列构成,形成于右旋剪切背景。蜀南1号、蜀南2号、蜀南3号走滑断裂带均形成于二叠系沉积前(相当于泥盆纪—石炭纪)。蜀南4号走滑断裂带则呈北东走向,主体沿着背斜带的脊部发育,在右旋剪切作用下发育,形成于二叠系沉积后(相当于早-中三叠世)。蜀南4号断裂带、蜀南3号断裂带的局部区段以及主体发育在二叠系—三叠系内的逆冲断层,对志留系、二叠系、三叠系的多套源储组合具有良好的沟通作用;同时,它们对断控缝洞型储集层的形成具有积极影响,利于二叠系栖霞组、茅二段、嘉陵江组等多层系的油气聚集成藏。

四川盆地中部资阳地区张扭断裂三维构造模型、构造演化与油气地质意义

基于钻井和地震数据,通过平面-剖面构造解析、三维断层构造建模、垂向断距分析及平衡剖面恢复,对四川盆地资阳地区张扭(走滑)断裂系统进行研究。结果表明,资阳三维地震工区张扭断裂系统由北东走向、伸展变形主导的F_(Ⅰ)19和F_(Ⅰ)20断裂带以及北西走向、右旋剪切变形的3组雁列正断层构成。其中,F_(Ⅰ)19、F_(Ⅰ)20断裂带贯穿新元古界—中下三叠统嘉陵江组,表现出“S”形丝带状的三维结构,在二叠系沉积前及早三叠世至少经历两期构造叠加改造;北西向的3组雁列正断层由两两成对、倾向相反、部分左阶排列的小型正断层构成,在二叠系沉积前基本定型,对F_(Ⅰ)19断裂带向东的生长和扩展造成限制。F_(Ⅰ)19、F_(Ⅰ)20断裂带自深往浅沟通多套烃源岩和储层,断层活动时间与生烃高峰期匹配良好;在F_(Ⅰ)19、F_(Ⅰ)20断裂带两侧的局部低幅背斜带上,若叠加发育寒武系—三叠系有利沉积相带和储层,则该区有望成为天然气聚集有利区。

塔中凸起张扭走滑断裂带分段构造特征及生长机制

塔里木盆地奥陶系碳酸盐岩发育斜向挤压背景下的压扭走滑断裂,但塔中凸起发现了一系列张扭走滑断裂,并对油气富集具有重要的控制作用。基于塔中凸起西部地区三维地震资料,结合相干、曲率等属性,统计走滑断裂运动参数,运用走滑断裂构造解析方法,优选塔中凸起F_(Ⅱ)21走滑断裂带开展走滑断裂分段建模研究,并探讨其生长机制。结果表明,F_(Ⅱ)21走滑断裂带具有平面分段、垂向分层特征,奥陶系碳酸盐岩顶面发育线状构造、斜列构造、马尾构造、翼尾构造、辫状构造和叠覆构造。走滑断裂构造高差分布特征揭示了走滑断裂带的分段生长与尾端扩张生长机制,该断裂带为调节走滑断裂带两侧反向收缩变形的变换断裂,经历雁列断裂阶段、生长连接阶段及再激活雁列断裂阶段的演化过程。

川东地区寒武系洗象池组构造特征及成藏模式

四川盆地东部上寒武统洗象池组是盆地内下组合油气勘探的重点领域。基于地层及沉积演化特征,利用地震、钻井岩心以及地球化学等资料,分析了川东地区上寒武统洗象池组构造特征及变形机制,从源、储、盖、运4个方面分析了其油气成藏条件,并总结了成藏模式。研究结果表明:(1)川东地区寒武系洗象池组表现为以2套滑脱变形带(中寒武统高台组膏盐岩和志留系泥岩)控制的、沿北西向传递的断褶构造,发育背冲构造、叠瓦状构造、断弯褶皱和盐底辟断弯褶皱4种构造圈闭样式;中寒武统高台组膏盐岩和中—下奥陶统泥灰岩2套盖层分别将下寒武统筇竹寺组、上奥陶统五峰组—下志留统龙马溪组2套烃源岩与洗象池组隔离。(2)研究区洗象池组具备油气成藏条件,五峰组—龙马溪组泥页岩是主要烃源岩,厚度为300~700 m,TOC值为2%~7%,生烃能力强,Ro为2.4%~4.0%,处于过成熟阶段;洗象池组沉积后期被岩溶和裂缝改造的滩相白云岩是相对优质的规模较大的储层,孔隙度大于2.1%;燕山期构造抬升和变形不仅在洗象池组形成了有效构造圈闭,还使其突破中—下奥陶统盖层与五峰组—龙马溪组对接,实现了油气的水平侧向运移。(3)研究区洗象池组为“新生古储、源储并置、侧向运移、构造圈闭”晚期天然气成藏模式;逆冲断层导致上盘褶皱的洗象池组与下盘五峰组—龙马溪组在水平面上并置,形成了源-储横向对接的构造圈闭,有效地提高了供烃和成藏的效率。

东海陆架盆地中部隆起带北西向大断层识别及成因机制

东海陆架盆地不同地区均揭示有局部北西走向断层的存在,但由于对断层缺乏盆地整体研究,导致断层运动学和动力学认识存在争议。以中部隆起带为重点研究区,通过对区域重磁和地震资料的综合分析开展了盆地尺度北西向大断层识别和分布规律研究,探讨了区域北西向大断层构造演化过程及成因机制。结果表明:①中部隆起带发育有10条北西向大断层,该类断层具有分布范围广,断层规模“南大北小”和断面相对低角度的特点,并控制了区域内中生界及古新—中下始新统厚度的南北差异;②北西向大断层形成时间早于北东、北北东向断层,主要经历中生代燕山期正断层发育、中生代末期至早中始新世伸展-转换断层发育、中晚始新世到渐新世断层整体消亡和中—上新世至今断层局部活化四个演化阶段;③北西向大断层的形成与中国东部印支—燕山期先挤压逆冲、后伸展回滑作用有关,反映印支期华南与华北板块南北碰撞向东南方向深入影响至东海陆架盆地区域,形成大量北西走向低角度逆冲断层,燕山期在北西—南东向区域挤压及地壳增厚背景下,存在广泛的北北东—南南西向伸展逃逸,最终控制了北西向低角度正断层的形成。上述研究为区域内深层及基底潜山领域的油气勘探研究提供了支撑。

东海陆架盆地丽水-椒江凹陷构造演化特征及其与油气成藏的关系

东海陆架盆地丽水-椒江凹陷经历了复杂的构造运动过程,目前已发现多个含油气构造,但仍未取得大规模商业油气发现,油气勘探未能突破的主要原因在于对其构造演化特征认识不清。基于最新采集的三维地震和钻井资料,通过断裂特征的精细刻画、平衡剖面恢复、已钻井地球化学特征分析等方法,对丽水-椒江凹陷的构造演化特征及其与油气成藏的关系进行了深入分析。结果表明:丽水-椒江凹陷主要发育3套断裂系统,包括深部断裂系统、浅部断裂系统和贯穿断裂系统,控制了凹陷整体东断西超,内部南北分区东西分带的构造格局;凹陷演化共经历4个阶段,包括晚白垩世—古新世断陷期、始新世初期坳陷期、始新世末期—渐新世抬升剥蚀期以及新近纪—第四纪沉降期,不同断裂系统形成于不同演化阶段,并对凹陷结构具有差异控制作用;断陷期发育的灵峰组厚层泥岩阻挡了油气的垂向运移,且深部断裂与浅部断裂在纵向上各自独立,互不连通,油气垂向运移不畅,限制了油气在烃源岩及邻近层位成藏,确定了丽水-椒江凹陷“近源下洼”的油气勘探方向。研究成果可为丽水-椒江凹陷的油气勘探提供基础理论支撑。

渤海湾盆地渤南低凸起西段低角度正断层分段生长特征及其油气地质意义

为了研究渤海湾盆地渤南低凸起低角度正断层分段生长诱发的时空差异演化特征及控藏机制,基于最新三维地震资料,精细刻画表征了断层分段生长过程及差异演化特征,结合区域构造背景,探讨断层成因机制及对油气成藏的控制作用。结果表明:渤南低凸起南边界F1断层和F2断层均为低角度正断层,源于中生代NWW—近EW向先存逆冲断层发生负反转,在新生代发生再次活化。F1断层具有平面上分段连接、垂向上多幕活动的特征,中段继承原有断面持续活动,西段和东段分别与裂陷Ⅱ幕新生NEE向断层和裂陷Ⅲ幕新生近EW向断层垂向搭接形成现今形态。低角度正断层对油气成藏的控制作用主要表现为:①低角度正断层断控侧沉积规模大,可提供充足的可容纳空间,形成规模陡坡砂体;②长期活动的低角度正断层是垂向油气运移通道,控制了油气垂向上的富集层位;③低角度正断层多期活动改造了深部储层物性,断层活动强度与优质储层的发育密切相关。

A Cenozoic tectono-sedimentary model of the Tainan Basin, the South China Sea: evidence from a multi-channel seismic profile

The Tainan Basin is one of the set of Cenozoic extensional basins along northern margin of the South China Sea that experienced extension and subsequently thermal subsidence. The Tainan Basin is close to the Taiwan Arc-Trench System and straddles a transition zone between oceanic and continental crust. A new regional multi-channel seismic profile （973-01） across the region of NE South China Sea is introduced in this paper. In seismic stratigraphy and structural geology, a model of Cenozoic tectono-sedimentation of the Tainan Basin is established. The results show that three stages can be suggested in Tainan Basin; In Stage A （Oligocene （？）-Lower Miocene） the stratigraphy shows restricted rifting, indicating crustal extension. Terrestrial sedi- ments mostly filled the faulted sags of the North Depression on the continental shelf. Structural highs, including the Central Uplift, blocked material transportation to the South Depression in abyssal basin. In Stage B the Tainan Basin （Middle-Upper Miocene） exhibits a broad subsidence resulting from the post-rifting thermal cooling. The faulted-sags in North Depression had been filled up. Terrestrial materials were transported over the structural highs and deposited directly in the South Depression through sub- marine gullies or canyons. This sedimentation resulted in a crucial change in the slope to a modem shape. In Stage C （Latest Miocene-Recent） a phase change from extension to compression took place due to the orogeny caused by the overthrusting of the Luzon volcanic arc. Many inverse structures, such as thrusts, fault bend folds, and a regional unconformity were formed. Forland basin began developing.