Comprehensive evaluation on hydrocarbon-bearing availability of fault traps in a rift basin: A case study of the Qikou sag in the Bohai Bay Basin, China

An evaluation system of hydrocarbon-bearing availability of fault traps was established based on the comprehensive analysis of fault segment growth history,fine reservoir anatomy and geochemistry tracing,with the Qikou sag in the Bohai Bay Basin as target area.The displacement/separation transform and displacement gradient method were used to prove the interpretation reliability of fault traps.The method of maximum throw subtraction was used to recover the history of fault growth and determine the availability of the forming period of fault traps.Based on the quantitative relationship between shale gouge ratio and cross-fault pressure difference of known reservoirs in southern Qikou sag,the critical shale gouge ratio of fault lateral sealing was calculated at 20%,and the quantitative evaluation chart based on the relationship of"fault throw–sand-formation ratio and hydrocarbon column height"was constructed.Based on the results of reservoir fine anatomy and quantitative fluorescence tracing test shale smear factor method is suitable for evaluating the vertical sealing of faults in the caprock of the middle submember of first member of Paleogene Shahejie Formation,and the shale smear factor critical value is 3.5.The juxtaposition thickness method is suitable for evaluating vertical sealing of faults in the caprock of the second member of Paleogene Dongying Formation,and the critical juxtaposition thickness of fault is 70–80 m.By combining four factors,the availability of fault trap interpretation,the availability of the forming period of fault trap,the availability of fault lateral sealing and the availability of fault vertical sealing,the comprehensive evaluation chart on hydrocarbon-bearing availability of fault traps in Qikou sag has been established,which provides a reasonable basis for risk assessment of fault traps.

Fault zone structures of northern and southern portions of the main central fault generated by the 2008 Wenchuan earthquake using fault zone trapped waves

The rupture process of the May 12, 2008 Ms8.0 Wenchuan earthquake was very complex. To study the rupture zones generated by this earthquake, four dense temporary seismic arrays across the two surface breaking traces of the main-shock were deployed in July and recorded a great amount of aftershocks. This paper focuses on the data interpretation of two arrays across the central main fault, the northern array line 1 and southern array line 3. The fault zone trapped waves recorded by the two arrays were used to study the structure of the central main fault and the difference between the northern and southern portions. The results show that the widths of the rupture zone are about 170-200 m and 200-230 m for northern and southern portions respectively. And the corresponding dip angles are 80° and 70°. The seismic velocity inside the fracture zone is about one half of the host rock. By comparison, the northern portion of the rupture zone is slightly narrower and steeper than the southern portion. Besides these differences, one more interesting and important difference is the positions of the rupture zone with respect to surface breaking traces. At the northern portion, the rupture zone is centered at the surface breaking trace, while at the southern portion it is not but is shifted to the northwest. This difference reflects the difference of rupture behaviors between two portions of the central main fault. The width of the rupture zone is smaller than that of MS.1 Kunlun earthquake though these two earthquakes have almost the same magnitudes. Multiple ruptures may be one factor to cause the narrower rupture zone.

Rock Damage Structure of the South Longmen-Shan Fault in the 2008 M8 Wenchuan Earthquake Viewed with Fault-Zone Trapped Waves and Scientific Drilling

This article is to review results from scientific drilling and fault-zone trapped waves （FZTWs） at the south Longman-Shan fault （LSF） zone that ruptured in the 2008 May 12 M8 Wenchuan earthquake in Sichuan,China.Immediately after the mainshock,two Wenchuan Fault Scientific Drilling （WFSD） boreholes were drilled at WFSD-1 and WFSD-2 sites approximately 400 m and 1 km west of the surface rupture along the Yinxiu-Beichuan fault （YBF）,the middle fault strand of the south LSF zone.Two boreholes met the principal slip of Wenchuan earthquake along the YBF at depths of 589-m and 1230-m,respectively.The slip is accompanied with a 100-200-m-wide zone consisting of fault gouge,breccia,cataclasite and fractures.Close to WFSD-1 site,the nearly-vertical slip of ～4.3-m with a 190-m wide zone of highly fractured rocks restricted to the hanging wall of the YBF was found at the ground surface after the Wenchuan earthquake.A dense linear seismic array was deployed across the surface rupture at this venue to record FZTWs generated by aftershocks.Observations and 3-D finite-difference simulations of FZTWs recorded at this cross-fault array and network stations close to the YBF show a distinct low-velocity zone composed by severely damaged rocks along the south LSF at seismogenic depths.The zone is several hundred meters wide along the principal slip,within which seismic velocities are reduced by ～30-55％ from wall-rock velocities and with the maximum velocity reduction in the ～200-m-wide rupture core zone at shallow depth.The FZTW-inferred geometry and physical properties of the south LSF rupture zone at shallow depth are in general consistent with the results from petrological and structural analyses of cores and well log at WFSD boreholes.We interpret this remarkable low-velocity zone as being a break-down zone during dynamic rupture in the 2008 M8 earthquake.We examined the FZTWS generated by similar earthquakes before and after the 2008 mainshock and observed that seismic velocities within fault core zone was reduced by ～10％ due to severe damage of fault rocks during the M8 mainshock.Scientific drilling and locations of aftershocks generating prominent FZTWs also indicate rupture bifurcation along the YBF and the Anxian-Guangxian fault （AGF）,two strands of the south LSF at shallow depth.A combination of seismic,petrologic and geologic study at the south LSF leads to further understand the relationship between the fault-zone structure and rupture dynamics,and the amplification of ground shaking strength along the low-velocity fault zone due to its waveguide effect.

Fault-zone trapped waves at Muyu in Wenchuan earthquake region

Trapped waves in the Qingchuan fault zone were observed at Muyu near the northeastern end of the fractured zone of the Wenchuan Ms8. 0 earthquake. The results indicate a fault-zone width of about 200 m and a great difference in physical property of the crust on different sides of the fault. The inferred location of crustal changes is consistent with land-form boundary on the surface

Genetic models of structural traps related to normal faults in the Putaohua Oilfield,Songliao Basin

The Putaohua Oilfield is a fault-prolific area and the faults have close relation with structural traps. The genetic models of the structural traps in the Putaohua Oilfield can be divided into two types： individual fault model and multi-fault interaction model. This is based on the description of displacement distribution of typical individual normal faults, the geometry of the footwall and hanging wall, and the analysis of the interaction between faults and the corresponding change in geometry when the faults grow. The individual fault model is that the displacement reaches a maximum at or near the center of fault and decreases toward the fault tips, so a half-graben is formed on the hanging wall of the fault and a half- anticline is formed on the footwall because of the isostatic process. The multi-fault interaction model is that during the growth of faults, they overlap and interact with each other, and accommodation zones are formed in the overlapping segments. The accommodation zones are favorable targets for hydrocarbon exploration, and the trap characteristics are dependent The multi-fault interaction model can be subdivided on the extent of overlap and occurrence of faults. into three types： synthetic accommodation zone, convergent accommodation zone and divergent accommodation zone. Hydrocarbon migration and accumulation models of each type have been developed. The hydrocarbon migration and accumulation models of the traps with different genetic models have their own characteristics in the different stages of fault growth.

Fault zone trapped waves at Longmenshan fault belt

Trapped waves in different sections of Longmenshan fault belt were observed, and the results show the difference between the northern and southern portions of this fault belt. Guanzhuang and Leigu surveying lines are located at the northern portion of the fault belt, and the result indicates that the width of the rupture zone underground in this area is about 160 - 180 m. The center position of rupture zone underground corresponds to the surface breaking trace, and is equally distributed at the edges of the two fault walls. However, Hongkou surveying line is located at the southern portion of the fault belt, and the result indicates that the width of the rupture zone underground in this area is about 180 -200 m. The rupture zone underground is mainly distributed below fault scarp. The Wenchuan MsS. 0 earthquake and Lushan Ms7.0 earthquake both occurred at the Longmenshan fault belt. The results will provide information for the structure background of the two violent earthquakes.

Exploration of fault-zone trapped waves at Pingtong Town,in Wenchuan earthquake region

Pingtong Town is located on the fractured zone of the Wenchuan 8.0 earthquake, and is seriously damaged by the earthquake. Our observation line is centered at an earthquake exploration trench across the fractured zone in the NW-SE direction, and is about 400 m long. The results reveal trapped waves in the rup- tured fault zone of the earthquake, and indicate a great difference in physical property between the media inside and outside the fault zone. The predominant frequency of the fault-zone trapped waves is about 3 -4 Hz. The wave amplitudes are larger near the exploration trench. The width of the fault zone in the crust at this location is estimated to be 200 m. In some records, the waveforms and the arrival times of S waves are quite different between the two sides of the trench. The place of change coincides with the boundary of uplift at the surface.

SEM Numerical Simulation of Vertical and Inclined Fault Zone Trapped Waves and Comparison of Their Wave Fields

Fault zone trapped waves( F ZTWs) m ainly travel along the fractured fault zone( F Z)which is of low velocity and high attenuation. FZTWs often carry significant information about a fault  s internal structure,so it is important to understand their wave field characteristics for FZ structure inversion. Most previous simulations are based on vertical faults,while in this paper we implement the FZTW simulations on vertical or inclined faults and compare their wave fields in both time and frequency domains. The results show that the existence of fault zone and inclined angle of fault can significantly influence the features of waves near faults. In amplitude,a fault zone can generate a larger amplitude of waves. The velocity contrast between two walls of fault may lead to amplification of amplitudes in the low velocity fault wall. In frequency,a fault zone tends to influence the waves in the low frequency range. In a pattern of particle polarization of FZTWs,it tends to be single direction for vertical faults but fork to multiple directions for inclined faults,which might provide a new way to study the fault zone with FZTWs. These conclusions may be valuable for FZ structure inversion,and will enhance the knowledge on near-fault strong ground motions.

Study on rupture zone of the M=8.1 Kunlun Mountain earthquake using fault-zone trapped waves

The observation of the fault-zone trapped waves was conducted using a seismic line with dense receivers across surface rupture zone of the M=8.1 Kunlun Mountain earthquake. The fault zone trapped waves were separated from seismograms by numerical filtering and spectral analyzing. The results show that: a) Both explosion and earthquake sources can excite fault-zone trapped waves, as long as they locate in or near the fault zone; b) Most energy of the fault-zone trapped waves concentrates in the fault zone and the amplitudes strongly decay with the distance from observation point to the fault zone; c) Dominant frequencies of the fault-zone trapped waves are related to the width of the fault zone and the velocity of the media in it. The wider the fault zone or the lower the velocity is, the lower the dominant frequencies are; d) For fault zone trapped waves, there exist dispersions; e) Based on the fault zone trapped waves observed in Kunlun Mountain Pass region, the width of the rupture plane is deduced to be about 300 m and is greater than that on the surface.

非传统油气资源:现实且潜力巨大的油气勘探开发新领域

依据是否编入目前的石油地质学,将圈闭(油气藏)类型分为传统圈闭(油气藏)和非传统圈闭(油气藏)。与传统圈闭(油气藏)相比,非传统圈闭(油气藏)具有形态特殊、内部结构复杂、储层非均质性强且生储盖组合多变、成藏机理奇特、分布位置更加隐蔽等特征,甚至有的非传统油气藏位于传统石油地质理论认为的禁区。目前发现和开发的非传统油气藏有露头油气藏、断溶体油气藏、断缝体油气藏和断壳体油气藏等,非传统油气藏正逐渐成为油气勘探开发的热点和亮点。我国地质条件和成藏环境极为复杂,仍然有相当数量的圈闭(油气藏)没有收入经典的石油地质学,非传统油气资源潜力巨大,它们多分布在(超)深层、(超)深水、高原、极地、特殊气候地区,甚至盆地外,是现实的油气勘探开发新目标和新领域。

金湖凹陷基性岩捕获锆石年龄及其区域构造意义

郯庐断裂带的形成演化是中国东部中生代关键大地构造事件,该断裂带起源机制问题是了解华南与华北板块汇聚过程与方式的基本前提。本文利用郯庐断裂带东侧金湖凹陷内7个新生代基性岩样品394个点的LA-ICP-MS锆石U-Pb年代学数据,在分析岩浆活动时代基础上,利用捕获锆石年龄信息探讨了大别造山带的古生代演化及郯庐断裂带起源机制问题,为认识上述问题提供了一个全新的视角。研究表明,金湖凹陷的基性岩浆活动时代为古近纪早期(66.1~56.5 Ma),与围岩的沉积时代吻合;基性岩中的捕获锆石来自大别造山带,是印支期板块碰撞造山中楔入郯庐断裂带东侧华南板块的造山带物质,具有华南板块、北淮阳和华北板块的混杂岩石圈信息;捕获锆石中445 Ma(变质锆石)、290 Ma(岩浆锆石)及214 Ma(变质锆石)等峰值年龄信息指示古生代以来北淮阳构造带经历了与北秦岭构造带类似的弧—陆俯冲、碰撞历程,暗示秦岭造山带的二郎坪洋、商丹洋和勉略洋可延伸至大别造山带东端;年代学数据及构造分析支持郯庐断裂带起源于嵌入碰撞背景下的华南板片撕裂边界,其起源形式为陆—陆碰撞下的板块斜向汇聚边界。

苏北盆地盐城凹陷盐③断裂带构造演化及其控圈作用

盐(3)断裂带位于苏北盆地盐城凹陷中,断裂带及周边区域发生过多期伸展-走滑复合的构造演化,控制圈闭的时空有效性。为阐明这些构造圈闭对油气差异聚集的影响,需先明确盐(3)断裂带在各时期的演化过程,并研究构造变形对圈闭的控制作用。本文基于盐城凹陷高精度三维地震资料,揭示主要断层和周边褶皱的几何学形态和运动学特征;结合断距回剥法定量恢复断层分段生长过程,进一步利用古构造图分析各期次的褶皱变形规律,解析各期次构造演化性质以及控圈作用。结果表明,盐(3)断裂带经历3个主要演化阶段:(1)泰州—阜宁期(K_(2)t—E_(1)f_(4))NW向伸展控制盐(3)正断层西段孤立生长、东段发生软连接,此时主干断裂的控陷作用不明显,圈闭不发育;(2)阜宁期末发生短期快速的压扭作用,造成盐(3)断层再活动,同时形成一系列的NW向共轭剪切断层,此时沿着盐(3)断裂带形成了一系列的圈闭;(3)戴南—盐城期(E_(2)d-Ny)发生SN向东强西弱的伸展,控制盐(3)断裂带东部再活动,并对圈闭进行调整。整体而言,盐城凹陷的构造活动强度具有“早强晚弱,东强西弱”的差异性,随着研究区构造应力场的不断变化,圈闭的构造幅度、面积逐渐缩小,构造高点也逐渐往SW向转移。

松辽盆地葡北油田油源断裂分类及其对油气分布的控制作用

为了研究松辽盆地北部断裂对葡北油田油气成藏的作用,基于断层引起的地层变形特征,通过断层地震特征的精细分析,重新划分并研究了葡北油田葡萄花油层油源断裂对该油田葡萄花油层成藏的作用。根据断裂是否连接源岩和目的储层,且在油气成藏期断裂是否活动,包括断距相对较大的断裂活动和无明显断距的微弱活动,划分了3种类型的油源断裂:一是沟通青一段源岩和葡萄花油层且断穿至T 06反射层(嫩江组三段底界面)的穿透型油源断裂;二是连接青一段源岩和葡萄花油层,在油气成藏期没有明显活动但引起断层端部发生褶皱变形的断层端部褶皱型油源断裂;三是连接青一段源岩和葡萄花油层在油气成藏期没有明显活动但断层两盘地层存在变形差异特征的断层两盘差异型油源断裂。研究结果表明,油源断裂与葡北油田葡萄花油层油气平面分布吻合程度更高,其中,穿透型油源断裂对油气聚集控制作用最为显著,揭示了油源断裂的活动强度以及油源断裂与断层圈闭的匹配所控制的油气成藏数量对油气富集的差异性的影响,该研究对类似区块油源断裂对油气控制作用分析可借鉴参考。

西湖凹陷平北地区断裂控藏作用研究

平湖构造带北部(简称平北地区)断裂复杂,复杂断裂不仅控制着圈闭的形成,而且对油气疏导和保存起着至关重要的作用。该文结合最新的地震和钻井资料,对平北地区断裂特征及控圈控藏作用进行梳理。结果表明,平北地区受控于早期鼻状隆起构造背景,断裂系统十分发育,形成自WS向NE散开的帚状断裂体系,主要发育断背斜、断鼻和断块等构造圈闭;同时北东走向的断裂与来自西部物源的条带状三角洲和潮汐作用的砂体相配合,形成一系列断裂-岩性复合圈闭。断裂对油气成藏的控制作用主要体现在两个方面,一方面是作为沟源断裂,起到疏导油气的作用;另一方面是作为圈闭边界,起到封堵油气的作用。该研究成果对研究区下步勘探部署可提供一定的技术支持。

断层阴影区地震优势信号提取新技术及其在西湖TT区的应用

在复杂断块地区,地震成像受断层的影响,断层下盘同相轴出现“上拉”、“下拉”或者同相轴错断的现象,极大地影响了断层圈闭构造高点的确定以及圈闭幅度的准确判断。开展针对复杂断层的高精度速度建模和高精度成像技术被认为是解决断层阴影区成像的主要处理技术解决方案。立足于地震采集信号自身的属性信息,充分挖掘地震信号的潜力,提出广角反射的折射线性去噪技术、中低频有效信号提取技术和优势信号精细速度建模技术,在西湖TT区目标评价中取得了良好的效果,明显减低了断层阴影对目标构造形态的影响,提高了构造圈闭定位的准确性。应用结果表明:通过准确的PSDM速度模型结合断层阴影区优势信号的提取,获得更聚焦的反射能量,断层阴影区弱振幅区得到消除,有效改善了断裂阴影区的成像效果。

北部湾盆地涠西南凹陷涠洲组断裂—岩性复合圈闭发育模式与勘探实践

为了解决北部湾盆地涠西南凹陷勘探目标搜索和油田可持续开发难度大的问题,对该区二号断裂带渐新统涠洲组三段构造圈闭发育层段开展了断裂—岩性复合圈闭研究。通过对控洼断裂演化与涠三段沉积特征关系的研究,发现涠三段沉积期二号断裂带活动性较弱,凹陷长轴方向辫状河三角洲水下分流河道向洼中持续推进;涠二段、涠一段沉积期区域构造活动强烈,产生一系列雁列式断裂,辫状河三角洲前缘形成的相对孤立的水下分流河道与呈雁列式断裂形成角度交错相互切割,从而形成了NE—SW向靠断层封堵、NW—SE向靠砂体尖灭的特色河道型构造—岩性圈闭群。研究表明:(1)涠三段发育“二号断裂带洼中断隆背景、低频摆动水道、雁列张扭断裂”三因素耦合的断裂—岩性型圈闭模式,辫状河三角洲水下分流河道主流线与二号断裂带的交会区是构造—岩性圈闭有利发育区带;(2)近物源交会区主要发育复合型构造—岩性圈闭,远物源交会区主要发育孤立型构造—岩性圈闭,建立了凹陷轴向河道控砂,断裂、砂体复合控藏的成藏模式。断裂—岩性型圈闭模式和成藏模式应用效果好,搜索了一批NE—SW向靠断层封堵、NW—SE向靠砂体尖灭的有利断裂—岩性复合圈闭群,并在涠B-E构造得到很好的应用,WB-E 1井钻遇油层近100 m,后续多口井钻探成功,新增油气探明地质储量超千万立方米,证实二号断裂带涠三段断裂—岩性复合圈闭是重要的勘探领域。

复杂断裂精细成像技术在南海东部惠州21洼的应用

珠江口盆地惠州21洼地下构造及断裂极为复杂,以前的地震采集方式和处理技术相对落后,地震资料存在断层成像不清、断点不落实、断层下降盘成像模糊等问题,极大地影响了对圈闭形态、构造高点及构造圈闭幅度的准确判断,导致构造圈闭难以识别和落实。为此,提出针对断裂发育区地震信号的深入挖潜处理技术,通过开展精细的信号处理,充分挖掘常规拖缆采集地震数据潜力,获得能够有效改善复杂断裂区成像的中、低频信号及大入射角范围内的有效地震反射,提高了断裂发育区地震资料信噪比。利用高保真的地震信号,开展基于数据与地质模式相约束的高精度叠前深度偏移速度建模,针对复杂断裂区,较好地利用大炮检距地震信息和中、低频有效信号,采取优势信号驱动下的高精度网格层析速度建模,极大地提高了速度拾取精度。同时,利用地质模式对速度模型进行有效约束,将成像效果与速度模型的相关性相结合,确定最终的成像速度模型,改善了惠州21洼复杂断裂区的构造成像效果。该项技术在惠州21洼勘探研究中得到较好应用,极大地降低了断层不落实对构造圈闭评价带来的影响,提高了构造圈闭解释的准确性,有效推动了该区勘探进程。

SNMP Trap机制在网络故障管理中的应用

本文介绍了SNMPTrap的基本概念,并给出了在Windows环境下,利用SNMPTrap机制,采用VisualC++6.0和SNMP++实现故障管理的方法。

Reservoir controlling differences between consequent faults and antithetic faults in slope area outside of source: A case study of the south-central Wenan slope of Jizhong Depression, Bohai Bay Basin, East China

The control effects of different occurrence faults on oil and gas accumulation and distribution in the outer slope area of oil and gas reservoirs were studied taking the south-central Wen’an slope of the Jizhong depression in the Bohai Bay Basin as an example.Based on 3D seismic data and the distribution of oil and water,the controlling differences between consequent fault and antithetic fault were analyzed and compared from the formation and evolution rule of faults and the formation mechanism of fault traps,including development positions of the consequent fault traps and antithetic fault traps,oil and gas distribution horizon adjusted by fault and formation period of fault traps.The differences between consequent faults and antithetic faults in controlling reservoirs have three main aspects:(1)Consequent fault traps and antithetic fault traps are in different positions,the consequent fault traps are at the segmented growing point in the hanging wall of"hard-linkage"faults,while the antithetic fault traps are developed in the position with the largest throw in the footwall because of tilting action;(2)The two kinds of faults result in different oil and gas distribution vertically,oil and gas adjusted by consequent faults is distributed in a single layer or multi-layers,while oil and gas adjusted by antithetic faults occur in single layers;(3)The two kinds of fault traps are formed in different periods,the consequent fault traps are formed at the time when the related faults enter the stage of"hard-linkage",while the antithetic fault traps are formed at the beginning of the fault active period.

Hydrocarbon Trap and Folding Style of the Pishvar Anticline, Sub-Coastal Fars, Zagros

The Pishvar anticline with Northwest-Southeast trend is located in the Sub-Coastal Fars area. This anticline with 80 Km length and 5 - 7 Km width is located in western part of the Lar area. The Pishvar anticline has two closures that are separated together by smooth down-warp. The oldest units that have outcropped on the surfaces are Asmari and Jahrom Formations. The most faults that observed on the Pishvar anticline are Normal fault. In the study area, the Razak and Hendurabi faults are main faults. These faults are strike slip with sinistral displacement. This anticline has greater dip in Northern flank compared to Southern flank. In this research, the main aim is folding style analysis, based on Description of fold geometry for indicate hydrocarbon trap structure in the Pishvar anticline. Description of fold geometry is important because they allow comparisons within and between folds and pattern-recognition in addition to occurrence and distribution of fold systems. We used Tectonics FP and Global Mapper Software for prepared some data in our study. In addition, we used the common classification of folds for our research. Based on results, the folding pattern of this anticline has indicated the fold style has different type in different parts of the Pishvar anticline. According to fold style variation and deformation analysis from B-B’ to C-C’ parts of the study anticline, it seems that the location of the Razak sinistral strike slip fault has existed in this parts. Fold style change can show this case. In addition, fold style variation and deformation analysis from E-E’ to F-F’ parts of this anticline has been affected of the secondary fault that is related to the Razak sinistral strike slip fault. We introduced this fault for first time. Finally, Based on results in this research, in western part there is little probability for access to hydrocarbon trap in upper horizons, unless the exploratory drilling continues to the deeper horizons.