Stratigraphic Sequence and Sedimentary Systems in the Middle-Southern Continental Slope of the East China Sea from Seismic Reflection Data: Exploration Prospects of Gas Hydrate

Many evidences for gas hydrate bearing sediments had been found in the continental slope of the East China Sea,such as bottom simulating reflections(BSRs),undersea gas springs,pyrite associated with methane leakage,mud diapirs/mud volcanos,bottom-water methane anomalies and so on.In this study,six key stratigraphic interfaces including T_0(seafloor),T_1(LGM,23 kyr B.P.),T_2(2.58 Myr),T_3(5.33 Myr),T_4(11.02 Myr)and T_5(16.12 Myr)were identified,and then five third-order sequences of SQIII1 to SQIII5 were divided.However,T5 in southern continental slope is not found,which shows that the middle-northern Okinawa Trough had begun to rift in the early Miocene,earlier than the southern segment.Four system tracts including lowstand systems tract(LST),transgressive systems tract(TST),highstand systems tract(HST)and falling stage systems tract(FSST)are further divided.The marine erosion interface of 11.02 Myr and regressive unconformity interface of 23 kyr B.P.indicate two large-scale sea level drop events in the research area.Seven typical seismic facies identified in the continental slope are continental shelf-edge deltas,littoral fluvial-delta plains,incised channels or submarine canyons,slope fans,submarine fans or coastal sandbars,littoral-neritic finegrained sediments,mud volcanos and some other geological bodies respectively.The minimum water depth for hydrate occurrence in the Okinawa Trough is 630 m,and the thickness of gas hydrate stability zone in continental slope is between 0 and 590 m.The calculated bottom boundary of hydrate stability zone is slightly deeper than BSRs on the seismic sections.The re-depositional turbidite sand bodies,such as canyon channels,slope fans and submarine fans developed in Quaternary strata,are the predominant hydrate reservoirs.According to developing process,the dynamic accumulation of hydrate systems can be divided into three evolutionary stages including canyon erosion and hydrate stability zone migration stage,sediments destabilizing and methane leakage stage,and channel filling and hydrate re-occurrence stage.

Analysis of blasting vibration signal of high steep anti-dip layered rock slope

Blasting is one of the most economical and efficient mining methods in open-pit mine production.However,behind the huge benefits,it poses a hidden threat to the quality of slope rock mass,stability of slope,and safety of nearby buildings.In order to explore the influence of blasting vibration on the stability of anti-dip layered rock slopes,herein,the site near the large-scale toppling failure area of Changshanhao gold mine stope of Inner Mongolia Taiping Mining Co.,Ltd.was selected for on-site blasting test and monitoring.The Peak Particle Velocity(PPV)measured at the monitoring point is located on the lower side of the maximum allowable vibration velocity curve that is prepared based on the allowable speed standard evaluation chart in the full frequency domain established by standards practiced in various countries such as German DIN4150,the USBM RI 8507,and Chinese GB6722-2014.This indicates that the blasting vibration has less influence on the location of the monitoring point.The vibration signals obtained in the blasting test were analyzed using the wavelet packet theory,and it was concluded that the blasting vibration signals measured in the anti-dip layered rock slope were mainly concentrated in two frequency bands of 0-80 Hz and 115-160 Hz.The sum of energy of the two frequency bands accounted for more than 99%,wherein,the energy contained in the 0-80 Hz frequency band accounted for more than 85%of the monitoring signals.The vibration signal with 0-80 Hz frequency band monitored at the slope toe was selected for the energy attenuation analysis.The results showed that the energy attenuation decreased in radial,vertical,and tangential directions.Further,the Energy Attenuation Rate per Meter(EARPM)was calculated.In conjunction with the site characteristics analysis,it was found that the energy attenuation rate was significantly affected by the rock mass characteristics of the structural plane.The slope reinforcement project can effectively reduce the absorption of vibration energy by the slope and increase slope stability.

Integrated simulation and monitoring to analyze failure mechanism of the anti-dip layered slope with soft and hard rock interbedding

The significant difference between the mechanical properties of soft rock and hard rock results in the complexity of the failure mode of the anti-dip layered slope with soft and hard rock interbedding.In order to reveal the landslide mechanism,taking the north slope of Fushun West Open-pit Mine as an example,this paper analyzed the failure mechanism of different landslides with monitoring and field surveys,and simulated the evolution of landslides.The study indicated that when the green mudstone(hard rock)of the anti-dip slope contains siltized intercalations(soft rock),the existence of weak layers not only aggravates the toppling deformation of anti-dip layered slope with high dip,but also causes the shear failure of anti-dip layered slope with stable low dip.The shear failure including subsidence induced sliding and wedge failure mainly exists in the unloading zone of the slope.Its failure depth and failure time were far less than that of toppling failure.In terms of the development characteristics of deformation,toppling deformation has the long-term and progressive characteristics,but shear failure deformation has the abrupt and transient characteristics.This study has deepened the understanding of such slope landslide mechanism,and can provide reference for similar engineering.

Investigation of the block toppling evolution of a layered model slope by centrifuge test and discrete element modeling

Primary toppling usually occurs in layered rock slopes with large anti-dip angles.In this paper,the block toppling evolution was explored using a large-scale centrifuge system.Each block column in the layered model slope was made of cement mortar.Some artificial cracks perpendicular to the block column were prefabricated.Strain gages,displacement gages,and high-speed camera measurements were employed to monitor the deformation and failure processes of the model slope.The centrifuge test results show that the block toppling evolution can be divided into seven stages,i.e.layer compression,formation of major tensile crack,reverse bending of the block column,closure of major tensile crack,strong bending of the block column,formation of failure zone,and complete failure.Block toppling is characterized by sudden large deformation and occurs in stages.The wedge-shaped cracks in the model incline towards the slope.Experimental observations show that block toppling is mainly caused by bending failure rather than by shear failure.The tensile strength also plays a key factor in the evolution of block toppling.The simulation results from discrete element method(DEM)is in line with the testing results.Tensile stress exists at the backside of rock column during toppling deformation.Stress concentration results in the fragmented rock column and its degree is the most significant at the slope toe.

Creation Conditions and Development Model for Lithologic and Stratigraphic Traps in the West Sag of the Beach Area,Liaohe Depression

At present the Eocene reservoir is the focus of exploration in the west sag of the beach area,Liaohe Depression,and lithologic and stratigraphic traps are the most important in the future work.The regional geological background indicated that lithologic and stratigraphic traps might be created in the study area. Studies on creation conditions and distribution pattern of lithologic and stratigraphic traps are

鄂尔多斯盆地西南部庆城地区三叠系长7段—长3段层序地层特征及演化规律

通过井-震精细标定、凝灰岩标志层约束和速度模型正演等方法,建立了鄂尔多斯盆地西南部庆城地区三叠系长7段—长3段等时地层格架,并对地层演化特征进行了分析。研究结果表明:①庆城地区三叠系长7段—长3段湖泛泥岩具有高伽马、高声波和中—高电阻率特征,单层湖泛泥岩在横向上表现为向湖盆中心倾斜的特征,纵向上长7段—长3段均有分布,具有等时对比意义;长4+5段发育的细粒沉积是不同时期湖泛作用的叠加响应结果。②研究区长7段—长3段以湖泛泥岩为界,自下而上划分为7个等时地层单元(Pss1—Pss7),横向上彼此叠置,向湖盆中心方向进积,垂向上表现为顶积层、斜积层和底积层“三元”结构。③研究区长7段—长3段整体表现为震荡湖退背景下的前积式充填特征,其演化可分为3个阶段:早期(Pss1—Pss2),坡度相对较小,地层总体呈楔状加积—弱进积叠置样式;中期(Pss3—Pss5)随着前积斜坡推进到半深湖—深湖区,坡度变大,地层主要表现为“S”形前积结构,顶积层广泛发育三角洲前缘沉积,底积层深湖相重力流砂体发育;晚期(Pss6—Pss7)湖盆萎缩,水体变浅,斜坡高度和角度均变小,顶积层发育三角洲平原沉积,斜积层中上部主要为三角洲前缘沉积,斜积层中下部和底积层以前三角洲—半深湖相泥质沉积为主。

西湖凹陷平北斜坡带平湖组层序构型差异及控砂模式

平北斜坡带是西湖凹陷岩性油气藏勘探的重点区带之一,但实际勘探过程中存在岩性砂体厚度小、横向变化大等问题,亟需开展不同构造单元内地层发育样式、沉积中心变迁、砂体发育机制等构造-沉积响应研究。基于最新钻井、测井及覆盖全区的高精度三维地震资料,开展了平北斜坡带平湖组三级层序-体系域高精度层序地层研究。基于古地貌、断裂体系的差异,划分了平北斜坡带构造-沉积单元,分析了不同单元内层序构型下断裂组合样式、地层接触关系、沉积充填样式的差异,探讨了不同层序构型差异的控制因素和控砂模式。研究表明,平北斜坡带可以划分为断裂陡坡型、对向断阶型、反向断阶型、顺向断阶型4种层序构型,层序构型差异受物源供给强弱变化、断裂体系活动差异、微古地貌转换调节、基准旋回迁移变化等控制,形成了4种砂体发育模式。通过不同构造单元层序构型差异和控砂机制研究,对于推动西湖凹陷平北斜坡带岩性油气藏领域勘探进程意义重大。

渤海湾盆地沙垒田西北斜坡带碳酸盐岩潜山储层形成与油气成藏

下古生界碳酸盐岩潜山是渤海湾盆地重要的油气勘探领域,目前已发现的碳酸盐岩潜山油气藏主要集中在构造高部位,对构造低部位斜坡带碳酸盐岩潜山的储层发育程度以及成藏规模还缺乏深入认识。为了探索斜坡带碳酸盐岩潜山储层发育规律,明确油气成藏条件,本研究以沙垒田西北(沙西北)斜坡带为靶区,开展了潜山构造演化、储集空间形成机理、潜山油气成藏综合分析。结果表明:沙西北斜坡带下古生界潜山岩性由上组合(大套灰岩夹白云岩、泥灰岩)和下组合(鲕粒灰岩、灰岩和泥岩互层)组成,崮山组区域稳定泥岩是二者的分界线;斜坡带潜山经历印支期、燕山早期、燕山中期、燕山晚期和喜马拉雅期五期构造运动,具有跷跷板式构造演化特征,多期构造活动形成的大量裂缝为储层发育奠定基础,优势岩性组合-叠合应力成缝-多期岩溶改造三元耦合控制碳酸盐岩潜山储层发育,上组合形成似层状缝溶型优质储层,是优势的油气聚集层系;低斜坡碳酸盐岩潜山处于烃源岩超压中心与常压储层直接接触的常超过渡带,发育上组合表生岩溶成储-下组合致密层遮挡封盖的地层侧封油气成藏模式,形成斜坡带大中型油田群。

黄骅坳陷歧口凹陷古近系坡折体系聚砂控藏机制分析

通过构造背景入手,充分考虑沉积因素,提出了斜坡区坡折体系的概念,指出黄骅坳陷歧口凹陷发育了构造坡折带(陡坡、缓坡)、挠曲坡折带、沉积坡折带、古地貌坡折带及侵蚀坡折带5种类型,其分布受古构造背景、断裂活动与沉积成岩因素的交互影响。类似于沉积体系,歧口凹陷坡折体系中各种类型坡折带平面上匹配,垂向上共生,其分布达歧口凹陷平面面积的70%以上。坡折带既是物源水下供给通道又是可容纳空间分布区,造就了斜坡及洼陷区的砂体十分富集,砂体分布具有"物源供砂,沟槽输砂,坡折控砂,源型聚砂"的内在机制。广泛发育的储集体使得歧口凹陷古近系油气分布具有满凹含油,叠合连片,优势富集,匹配控藏的典型特征,由此指出了歧北斜坡、滨海斜坡、板桥次凹等的坡折带与洼陷区是目前歧口凹陷古近系地层岩性油气藏勘探的有利区域。

陆相断陷湖盆层序构成样式及砂体预测模式——以南堡凹陷东营组为例

以渤海湾盆地南堡凹陷东营组为例,通过不同构造带的层序构成样式分析,阐明了陆相断陷湖盆的层序构成样式对砂体分布的控制作用,为陆相断陷湖盆砂体分布预测提供了理论依据。通过南堡凹陷东营组沉积充填时不同构造背景下形成的层序样式及其对储集砂体控制作用的分析,归纳出两种构造背景下的4种层序构成样式,即在北部断坡带构造背景下发育的多断坡带型、单断坡带型和转换带型以及在南部滩海地区斜坡带构造背景下发育的缓坡坡折型。在此基础上,建立砂体预测模式指导储层预测,对确定优质储集体的分布具有指导意义。

古地貌对陆相裂谷盆地层序充填特征的控制——以渤中凹陷西斜坡区下第三系为例

构造运动造就的古地貌在陆相盆地 ,特别是裂谷盆地对层序形成与发育起着重要的控制作用。裂陷扩张早期 ,凸起前发育下切河谷充填作用 ,前缘发育扇三角洲体系 ;当陆源碎屑补给缺乏时 ,局部隆起的水下平台区发育滨、浅湖滩坝或生物碎屑滩体系。裂陷扩张早中期 ,基准面上升时期凸起区为盆地主要物源区。受长期活动的边界基底断裂规模、性质、活动强度的控制 ,盆地边缘发育 3种类型的古地形坡折带 ,分别控制 3种类型沉积体系的形成。断崖型坡折带发育近岸水下扇沉积体系 ;断阶型坡折带发育斜坡扇体系 ;陡坡型坡折带发育扇三角洲及前方的盆底扇体系。基准面下降时期盆地充填作用增强 ,受凸凹相间分布的宏观地貌特征控制 ,凸起前缘发育扇三角洲体系 ,凸起间鞍部地区沿盆地长轴方向发育外源大型河流 -三角洲体系。

断陷盆地缓坡区控砂控藏机制与勘探发现——以歧口凹陷歧北缓坡带为例

为揭示断陷盆地缓坡区的控砂控藏机制,以高品质的800km^2三维地震和91口钻井资料为基础,层序地层和沉积演化分析表明,受控于断块掀斜和差异沉降作用,歧口凹陷歧北斜坡南侧在古近纪表现为具挠曲坡折的缓坡带。该带层序界面标志清晰,包括削截、顶超和上超等反射终止类型,由此将古近系划分为3个二级层序和11个三级层序。三级层序的结构样式类似于具陆架坡折的被动大陆边缘,其低位体系域和湖扩体系域普遍发育不同类型的岩性圈闭。其中,沙河街组三段—沙河街组二段沉积期,研究区断陷作用强烈,挠曲坡折带的坡度较大,层序的低位体系域主要发育大型低位扇;随后,拗陷作用增强,挠曲坡折带的坡度逐渐减小,至东营组沉积期转变为以低位三角洲沉积为主。湖扩体系域的岩性圈闭发育在沙河街组二段—沙河街组一段和东营组,发育湖相碳酸盐岩滩坝和碎屑岩滩坝。研究区挠曲坡折带明显控制了地层-岩性圈闭的发育和分布,成为缓坡带油气勘探的有利场所。通过勘探实践,新增三级储量近4×10~8t,探井成功率达80%,展示了挠曲缓坡带地层-岩性油气藏良好的勘探前景。

贝尔凹陷贝西斜坡南屯组层序特征及其油气成藏模式研究

运用层序地层学指导油气藏勘探,是目前油气勘探的热门课题和重要的发展方向之一。以层序地层学理论为指导,综合运用地震、测井、岩心等资料,采用井—震对比综合分析,波阻抗反演来验证的方法,在贝尔凹陷贝西斜坡南屯组中共识别出2个主要由扇三角洲—湖泊体系组成的三级层序:层序Ⅰ相当于南一段,层序Ⅱ相当于南二段。每个层序发育完整,分别由低水位体系域、水进体系域和高水位体系域组成。针对研究区目的层段所划分层序发育的特点,在层序地层单元划分和对比基础上,对不同类型层序格架内的沉积特征和层序地层模式进行了总结,并建立了相应的油气成藏模式。

歧口凹陷歧北斜坡沙三段挠曲坡折体系与岩性油气藏勘探

从斜坡带沉积背景和古地貌特征入手,以高分辨率层序地层格架为单元,采用3D地震、测录井、取心、砂体分布与油气藏特征等资料综合分析的方法,探讨了渤海湾盆地歧口凹陷歧北斜坡沙三段坡折体系特征与砂体分布以及油气藏之间的关系。结果表明,歧北斜坡沙三段受差异沉降、断块翘倾与基底构造影响,总体发育三级坡坪带,在斜坡高部位一级坡坪带的凸起近缘发育侵蚀坡折带,斜坡中低部位发育挠曲坡折带,构成了沙三段低位期侵蚀-挠曲坡折体系。在斜坡区沙三期,盆内物源供砂,沟槽输砂,坡坪控砂,源型聚砂,纵向上可识别出低位、湖扩、高位3个三级旋回与7个四级高分辨率旋回,各层顺斜向上超覆分布,在各级坡坪带发育了辫状河三角洲前缘、远岸水下扇与滨浅湖砂质滩坝等砂体,地层岩性圈闭发育。这些地层岩性圈闭与烃源区近邻,优势输导,富集成藏,叠合连片,是斜坡区地层岩性油气藏勘探的重要对象之一。

塔北地区上奥陶统良里塔格组台缘带分段性及石油地质意义

碳酸盐岩台缘带类型对储层形成与油气产能具有重要的控制作用。利用塔北地区大量最新的地震资料与钻井资料,通过上奥陶统良里塔格组地层厚度变化刻画台缘带平面展布,基于台缘带地层坡度的计算揭示其不同段台缘类型的差异。在此基础上,探讨台缘带分段性对储层发育的控制作用。结果表明:①良里塔格组台缘带具有明显地层加厚的特点,平面上环塔北古隆起呈条带状展布,长约240km、宽约10～20km,面积达2600km^2。②基于台缘带地层坡度的变化,明确了良里塔格组台缘带沿东西方向表现为不同的类型,具有一定的分段性。西段为弱镶边型台地边缘,分布在英买力—哈拉哈塘—托普台地区,地震响应为向盆地方向减薄的楔形反射,地层坡度较大,介于1°～3°;东段为宽缓的缓坡型台地边缘,分布在塔河东部—轮古东—于奇地区,在地震剖面上由台地向盆地方向表现为一个波谷同相轴逐渐变细直至消失,地层坡度较小,介于0.2°～1°。③台缘带的分段性造成东、西段储层发育的差异性。西段储层品质好,厚度大,横向变化大;东段储层品质稍差,厚度小,平面分布广。塔北地区良里塔格组台缘带分段性对于优选有利勘探区带具有一定的指导意义。

黄骅坳陷歧北斜坡区薄层湖相碳酸盐岩沉积相模式及演化特征

歧北斜坡区沙-下亚段湖相碳酸盐岩储层较薄（多数集中在0．5～8m），地震资料难以指导内部小层及滩体划分，沉积相模式、演化规律及主控因素认识不清，采用标志层控制、静-动态资料相互拟合的方法，利用岩心、测井、地球化学、古生物等资料，结合示踪剂、吸水剖面等动态资料对薄层湖相碳酸盐岩储层进行综合研究。研究结果表明：超覆地层对比模式符合研究区薄层湖相碳酸盐岩地层真实发育情况，并识别出5期明显的湖岸线；湖水首先沿着港西断层形成的断槽及中部的斜坡低洼区由东向西主发生湖侵；研究区主要发育滨浅湖亚相，包括生屑滩、混积滩等6种沉积微相，生屑滩面积占60％以上；沉积模式显示出沉积早期，地形坡度大、湖侵范围小、滨浅湖面积也最小，主要沉积沿岸碎屑岩砂坝；沉积中后期，水体越过坡折带，滨浅湖面积不断扩大，并迅速超覆至全区，生屑滩沉积面积达到最大的演化规律。歧北斜坡区湖水成化、湖相碳酸盐岩广泛沉积的主要原因，是海侵作用致使湖水初步成化和浅水缓坡台地环境导致混合水蒸发浓缩二次成化双重作用的结果。强烈的剥蚀和填平补齐导致的近似平台型古地貌特征和古生物的大量繁殖，也是控制北斜坡区沉积相类型及演化的主要因素之一。

川西南部灯影组展布特征新认识及油气地质勘探意义

四川盆地震旦系灯影组勘探成效显著、潜力巨大。对四川盆地川西南部开展野外露头、岩心岩石学特征和地球化学分析,并结合地震资料综合研究认为:川西南部汉王场构造汉深1井震旦系灯影组具有贫藻富硅、Ca及Mg含量相对低、Si含量高、δ13C及δ18O偏低的特征,与灯四段在岩性特征、常量元素和同位素含量上基本一致,所钻揭的灯影组层位归属为灯四段;井震结合预测,川西南部灯四段主要在成都—犍为以西地区分布,厚200~300m,在盆地内分布面积达1.5×10^4km^2,向南一直延伸到西昌、云南地区。灯四段厚度向德阳—安岳裂陷内逐渐减薄,具有缓坡型台地边缘特征。川西南部地区灯四段储层发育,紧邻裂陷槽内寒武系优质烃源岩,成油期处于古隆起高部位,发育古油藏,后期历经多次构造运动,油裂气重新调整聚集,具备形成构造型、构造—岩性复合型、构造—地层复合型等气藏的地质条件,邛崃—大兴场—眉山地区是勘探的有利区带。

白云凹陷北坡特殊层序地层样式

白云凹陷北坡具有独特的层序地层样式 :它的坡度较缓 ,不存在地貌上的陆架坡折 ,但由于断裂的活动 ,断层上下盘的落差客观上起到了陆架坡折的作用 ,使其低水位体系域具有Ⅰ型陡坡层序的特征 ,主要由盆底扇、深切河谷及充填物等组成。对于这种新的层序地层样式 。

歧北凹陷古近系构造坡折带对圈闭的控制作用

应用三维地震、钻井和测井等资料,对歧北凹陷进行层序地层学研究。研究区古近系可划分为3个二级层序,11个三级层序。歧北凹陷斜坡区发育断裂坡折和挠曲坡折两种构造坡折带类型。坡折带的发育演化具有明显的阶段性和继承性:早期为断裂坡折带,晚期为挠曲坡折带。不同类型坡折带层序构成样式及内部体系域构成不同,断裂坡折带控制了低位扇三角洲砂体以及构造-岩性复合圈闭的发育,而挠曲坡折带除了对砂体有控制作用外,更突出地表现为对地层超覆以及岩性圈闭发育的控制。坡折带附近是非构造圈闭发育的有利部位,进一步勘探的潜力巨大。

源外地层-岩性油气藏成藏与富集高产主控因素

埕海斜坡区是歧口凹陷重要的"源外"油气勘探区带,尤其是地层-岩性油气藏勘探程度较低,剩余勘探潜力较大。通过对埕海斜坡区古近系地层-岩性油气藏成藏条件的研究表明,该区邻近歧口生烃凹陷,存在多个继承性古沟槽,为砂体输送提供了重要通道,发育2类5种地层-岩性圈闭,储盖组合条件良好,具备地层-岩性油气藏形成的地质条件。研究区与生烃中心存在的源储压差是埕海斜坡区地层-岩性油气藏富集的基础,断层、不整合面和渗透性砂层组成的复式输导体系控制了油气运移方向和聚集方式,沉积微相控制了油气的平面分布。通过地层-岩性油藏特征及分布规律研究,建立埕海斜坡区油气富集成藏模式,明确了北部断阶区主要发育构造-岩性油藏,南部高斜坡区主要发育地层-岩性油藏。