Shale Lithofacies and Sedimentary Environment of the Third Member,Shahejie Formation,Zhanhua Sag,Eastern China

Researches into shale lithofacies,their sedimentary environments and relationship benefit understanding both of sedimentary cycle division and unconventional hydrocarbon exploration in lacustrine basins.Based on a 100~300-m-thick dark shale,mudstone and limestone encountered in the lower third member of the Eocene Shahejie Formation(Es3l member)in Zhanhua Sag,Bohai Bay Basin,eastern China,routine core analysis,thin sectioning,scanning electron microscopy(SEM),mineralogical and geochemical measurements were used to understand detailed facies characterization and paleoclimate in the member.This Es3l shale sediment includes three sedimentary cycles(C3,C2 and C1),from bottom to top,with complex sedimentary characters and spatial distribution.In terms of the composition,texture,bedding and thickness,six lithofacies are recognized in this succession.Some geochemical parameters,such as trace elements(Sr/Ba,Na/Al,V/Ni,V/(V+Ni),U/Th),carbon and oxygen isotopes(δ^(18)O,δ^(13)C),and total organic carbon content(TOC)indicate that the shales were deposited in a deep to semi-deep lake,with the water column being salty,stratified,enclosed and reductive.During cycles C3 and C2 of the middle-lower sections,the climate was arid,and the water was salty and stratified.Laminated and laminar mudstone-limestone was deposited with moderate organic matter(average TOC 1.8%)and good reservoir quality(average porosity 6.5%),which can be regarded as favorable reservoir.During the C1 cycle,a large amount of organic matter was input from outside the basin and this led to high productivity with a more humid climate.Massive calcareous mudstone was deposited,and this is characterized by high TOC(average 3.6%)and moderate porosity(average 4%),and provides favorable source rocks.

Paleoenvironmental reconstruction and organic matter accumulation of the paleogene shahejie oil shale in the Zhanhua Sag, Bohai Bay Basin, Eastern China

The controlling factors of organic-rich shale accumulation is essential for the exploration and development of shale oil and gas resources.The sedimentary environment plays a vital role in the formation of organic-rich sediments in lacustrine facies.This article unravels the mineralogy,geochemistry,and paleoenvironmental evolution during the deposition of the Paleogene Shahejie Formation(Es_(3)^(L)).It discusses the effects of paleoclimate,paleosalinity,paleoredox conditions,paleowater depth,and paleoproductivity on organic matter(OM)enrichment.Finally,the OM enrichment model was established.The results show that the mineralogical compositions are mainly composed of calcite(avg.40.13%),quartz(avg.21.64%)and clay minerals(avg.24.07%),accompanied by dolomite(avg.7.07%),feldspar(avg.6.36%)and pyrite(avg.2.95%).The Es_(3)^(L) shale has a high abundance of OM,with total organic carbon(TOC)ranging from 1.07%to 5.12%.The organic matter type is mainly composed of type I-II_(1) kerogen,which is generally considered a good-quality source rock.The source of OM is a mixture of lower bacteria,algae,and plants.During the early sedimentary period,the paleoclimate was dry and cold,with high salinity,intense reducibility,and relatively low productivity.During the late sedimentary period,the climate became warmer and more humid.As a result,the salinity decreased to a level that was suitable for biological reproduction,and productivity increased gradually due to the input of terrigenous plants.Paleosalinity and paleoclimate determined the environment of the sedimentary period,in addition,paleoproductivity and paleoredox condition indicated the formation and preservation conditions of OM.The warm and humid climate,brackish water,suitable reduction conditions and high productivity are the favorable conditions for the generation and preservation of organic matter.The research results may have implications for the genetic mechanisms of organic matter accumulation.They will provide theoretical and technical insights into the exploration and development of shale oil.

Paleosalinity reconstruction in offshore lacustrine basins based on elemental geochemistry:a case study of Middle Upper Eocene Shahejie Formation,Zhanhua Sag,Bohai Bay Basin

Salinity is a crucial property of water body and is essential for the restoration of paleoecology and paleoenvironment.However,the theoretical method of application of elemental geochemical proxies to paleosalinity reconstruction is still underdeveloped.Moreover,accurate determination and reconstruction of paleosalinity and its variation in an offshore lacustrine basin have been extremely challenging thus far.This study presents detailed elemental geochemical investigations from the Zhanhua Sag in the southern Bohai Bay Basin to reconstruct the salinity variation in the Paleogene Eocene Shahejie Formation(50.8-33.9 Ma).Based on the variation of strontium barium ratio(Sr/Ba)and boron gallium ratio(B/Ga),we determined three typical salinity types of water body:salty water(Sr/Ba>0.5,B/Ga>6),brackish water(0.2<Sr/Ba<0.5,3<B/Ga<6),and fresh water(Sr/Ba<0.2,B/Ga<3),after eliminating carbonate-sourced strontium(Sr).The salinity values following Couch’s paleosalinometer r anged from 3.1 to 11.9,reflecting the overall characteristics of oligohaline(0.5<salinity value<5)to mesohaline(5<salinity value<18)brackish water.All proxies yielded similar trends in paleosalinity variation,demonstrating a clear trend of rising and then declining from 50.8 Ma to 33.9 Ma.We considered that the B/Ga ratio had the highest reliability and resolution in determining the salinity types of water body in the study area.The environmental factors causing paleosalinity variation were also thoroughly analysed based on the temporal relationship among the salinity types of watermasses,paleoclimate characteristics from pollen records,and marine transgression events from marine fossils.Our research established a model of paleoclimatic and eustatic mechanisms to explain paleosalinity variation,providing reasonable and integral driving forces for the salinity variation of all offshore lacustrine basins.

Quantitative Architectural Anatomy of the Meandering Fluvial Deposits of the Neogene Upper Guantao Formation in Zhanhua Sag,Bohai Bay Basin,China

The residual oil in the fluvial reservoir of Gudong Oilfield is still widely developed even after decades of development.In order to explore the remaining oil in the subsurface fluvial reservoir,we need to have a better understanding on fluvial sandbody characteristics.This paper aims to demonstrate how to quantify anatomy on meandering fluvial architecture.Sedimentologic data from core descriptions of Guantao Formation in Gudong Oilfield were used to identify architectural elements.The upper Guantao Formation consists of ten lithofacies composing five different types of architectural elements.By integrating the available core,well logs,and seismic data,the fluvial sandbody distribution was analyzed.To characterize the fluvial channel geomorphology,we used seismic inversion to explore the stratigraphic correlation and stacking patterns of different channels,and the sandbody isopach map was obtained by the sandbody thickness in each layer.The architectural elements distribution in the plane was mapped by the sandbody isopach map and its profile characteristics.According to the investigation of meandering fluvial outcrops,subsurface meandering fluvial seismic geomorphology,and modern river morphology,the upstream-bar portions are always eroded because of the downstream channel migration.Statistics on the morphometric parameters(bar width/looplength,upstream deflection angle,downstream deflection angle,etc.)of modern meandering river(Ob River)were obtained from the Google Earth.It is found that the bar width/looplength and upstream deflection angle,upstream deflection angle and downstream deflection angle in modern meandering river have a good relationship,and we can have a quantitative architectural characterization on the point bar.This study quantified lithofacies thickness and proportion in different architectural elements of Guantao Formation,which ensures a high resolution anatomy on the small scale architecture.By using this method,the lithofacies proportion in each architectural element was computed,and through the statistics of architectural elements proportion in the Gudong Oilfield,the different lithofacies proportions in the block 6 can be computed.

沾化凹陷孤北洼陷东三段沉积体系类型及差异分布

沾化凹陷孤北洼陷东营组油气资源十分丰富,但沉积类型及其分布制约了油气勘探方向和精细勘探。文中综合孤北洼陷钻测井、岩心和三维地震资料,详细研究了东营组东三段沉积类型及其时空分布特征。结果表明:1)孤北洼陷东三段(Ed3)发育近岸水下扇、辫状河三角洲、滑塌浊积扇、滨浅湖和半深湖—深湖沉积。2)东三段沉积类型时空分布差异性特征明显。西缘陡坡带发育近源砂砾岩与暗色泥岩组合的近岸水下扇;南侧和东侧缓坡带发育辫状河三角洲;洼陷内发育湖相泥岩,断裂带附近多为滑塌浊积扇。3)沉积相带影响了储层质量。距源区越远,结构成熟度越高,则有利储层越发育;滑塌浊积扇相带储层质量优于辫状河三角洲相带,近岸水下扇相带相对较差。

济阳坳陷沾化东部古—中生界潜山构造样式与成藏模式

济阳坳陷古—中生界潜山经历多期挤压、伸展、走滑及剥蚀等构造作用的叠加,以沾化东部潜山为例,利用丰富的钻井与地震资料,在潜山构造层划分的基础上,剖析了潜山构造演化及构造特征,总结了潜山构造样式,建立了油气成藏模式。研究结果表明,晚古生代以来,在多期不同方向、不同性质构造运动的作用下,沾化东部古—中生界潜山经历了4期挤压作用、2期伸展作用、2期走滑作用、4期剥蚀作用,形成了高位、中位和低位3类潜山,发育了伸展、挤压、走滑与剥蚀4类9种构造样式。依据构造样式及潜山地层残留和上覆盖层的差异,建立了3类潜山成藏模式,其油气来源、油气富集层段及富集特征各不相同,其中高位潜山斜坡带上古生界与中生界、中位潜山下古生界和低位潜山中紧靠油源的潜山各层系油气成藏条件最为有利,油气富集程度高,是研究区下一步重点勘探对象。

渤海湾盆地沾化凹陷新生界断层精细表征及地质意义

断层的精细表征对高含水期复杂断块油田剩余油挖潜具有重要意义。利用井-震标志层对比、地震同相轴变异识别与断层叠合模型验证等方法,对渤海湾盆地沾化凹陷新生界复杂断块油田开展了断层精细表征。研究结果表明:(1)沾化凹陷复杂断块油藏断层两侧岩层的对接关系复杂,断层组合样式多样,继承性小微断层发育,通过断点定位、断面解释、断层平面组合与空间叠合建模等,实现断层特别是小微断层的精准识别、定位与表征。(2)研究区小微断层发育的重要特征为地震剖面中同相轴的扭曲、分叉、合并等变异现象,同相轴微扭动、微扭曲、微错断是小微断层断点识别与定位的重要依据。(3)断层精细表征使研究区断层的断边“盲区”和“模糊区”变为剩余油富集的潜力区,断层两侧外扩可新增地质储量。断层精细表征可优化完善井网布局、增加挖潜开发实效,还可为进一步明确剩余油富集分布规律、调整开发井网和实施精准开发等提供科学依据。

济阳坳陷沾化凹陷邵家走滑—伸展断层带构造特征及其石油地质意义

沾化凹陷是济阳坳陷中重要的油气增储阵地之,经历多了多期构造运动的叠合改造,近期的研究表明该地区发育了许多走滑—伸展性质的断层,但是其对于成藏的控制作用研究较薄弱。本次研究结合地震、测井与岩心观察、地化分析等资料,采用地球物理—地质综合分析从断裂带结构的角度走滑—伸展性质的义东—邵家断裂带进行了剖析。

渤海湾盆地沾化凹陷新近系馆陶组储层敏感性

储层敏感性分析是判别储层伤害程度的重要手段,对后期高效开发和剩余油挖潜具有重要意义。选取渤海湾盆地沾化凹陷垦西油田新近系馆陶组储层岩心样品,结合薄片观察、X射线衍射分析及压汞测试、流动水驱实验,对馆陶组上段和下段储层伤害指数和敏感性特征进行了分析。研究结果表明:(1)渤海湾盆地沾化凹陷新近系馆陶组储层岩石胶结疏松,孔隙结构总体孔径较大,孔喉分布较均匀,连通性较好;岩石矿物组成以石英、斜长石、钾长石和岩屑为主,黏土矿物主要包括高岭石、伊利石、绿泥石及伊蒙混层;馆上段以细粒为主,馆下段以中粒为主。(2)馆陶组储层普遍具中等速敏性、弱碱敏性、弱盐敏性特征;上下两段的酸敏性特征差异较大,上段具有非酸敏性特征,而下段具有强酸敏性特征,酸敏指数达78.28%;(3)研究区馆陶组铁白云石、绿泥石含量及孔隙结构对储层敏感性具有控制作用。(4)控制注采流速是研究区开发方案中的重要内容,对馆下段酸敏带来的储层伤害要进行防护和治理。

济阳坳陷地温-地压场特征及其石油地质意义

总结济阳坳陷各凹陷地温场和地压场的平面和剖面特征以及二者的耦合特征 ,分析不同的地温 地压场特征与油气分布的关系。认为东营凹陷和沾化凹陷具有超压型复式温度 压力系统特征 ,惠民凹陷具有低压型复式温度 压力系统特征。不同的温度 压力系统使得油气藏在各凹陷的形成与分布特征也不同。图 5参

渤海湾盆地沾化凹陷渤南洼陷原油地球化学特征及成藏期分析

下第三系沙四段是沾化凹陷渤南洼陷深层主要产油层,目前关于沙四段原油的油源和成藏期问题还存在不同的认识。通过对研究区储层流体包裹体分析,结合沙四段原油的地球化学特征,沙三段和沙四段烃源岩的生、排烃资料及构造演化资料,讨论了沙四段油藏的形成历史。研究表明,渤南洼陷沙四段曾发生过2期油气充注:第一期始于沙二段沉积末期,主要时期为沙一段沉积后期到东营组沉积中期,由于构造抬升,至东营组沉积末期(28.8 Ma)可能存在间断;第二期油气聚集从馆陶组沉积初期到明化镇组沉积早期,主要在馆陶组沉积期。油气成藏时期与沙四段和沙三段烃源岩的主要生、排烃期是相一致的。由此推测,沙三段与沙四段油源的相对贡献主要取决于烃源岩与油源断层及圈闭的空间配置关系。

沾化凹陷罗家地区沙三下段泥页岩储层特征

沾化凹陷罗家地区古近系沙河街组沙三下段发育100～300m厚的暗色泥页岩，具有较大的油气资源量和勘探潜力。研究表明，罗家地区的这套泥页岩为盐度较高、强还原性的深湖一半深湖沉积，岩石类型以泥岩、灰岩及之间的过渡岩性为主，碳酸盐矿物含量一般高于50％。根据泥页岩纹层厚度、组合方式、比例和稳定性，将深水泥页岩划分为6种类型，其中以薄层状泥质灰岩为主。泥页岩储层孔隙度为2％-8％，平均5．3％；渗透率变化较大，一般为（1-10）×10^-3μm。，平均为7．5×10-μm^2，为低孔低渗的非常规储层。储集空间类型多，储层发育的裂缝包括构造裂缝、层间微裂缝和成岩缝，孔隙包括矿物晶间孔、溶蚀孔、有机质孔等。储层质量受矿物组成和岩相、成岩作用、有机质含量等因素共同控制，其中有机质含量是控制该套泥页岩储层物性的主要内在因素。

沾化凹陷中、新生代断裂发育及其形成机制分析

在采用断层活动速率定量分析断裂活动性的基础上 ,就印支运动以来沾化凹陷断裂的发育期次、组合特点、成因机制等进行了研究和探讨。结果表明 :中、新生代济阳坳陷沾化凹陷的断裂发育受控于欧亚构造域的西伯利亚板块、扬子板块与华北板块的挤压拼接和滨太平洋构造域及其郯庐断裂带的活动两大构造体系域 ;晚三叠世NW向逆推断层的发育为华北板块与扬子板块挤压拼接时产生的板内局部挤压调整效应 ;晚侏罗世—白垩纪NW向断层发生的构造反转是在太平洋板块俯冲造成地幔上涌所产生水平拉张背景下郯庐断裂左行走滑的结果 ;燕山—喜山构造阶段过渡期郯庐断裂由左旋至右旋的转换 ,则导致了研究区断裂发育由NW向至NE(NEE)

沾化凹陷新近系沉积岩地球化学特征及其物源指示意义

采用ICP-MS详细研究了沾化凹陷新近系馆陶组（Ng）和明化镇组（Nm）沉积岩的微量元素地球化学特征。结果显示：样品稀土元素（REE）质量分数相对较高,w（ΣREE）介于106.4×10^-6-390.9×10^-6间,馆陶组和明化镇组的平均值分别为198.83×10^-6,203.18×10^-6,高于大陆上地壳（UCC）和后太古宙页岩（PAAS）的平均值;稀土元素配分曲线显示LREE富集、HREE平坦和中等负Eu异常[δ（Eu）介于0.66-0.83,平均值为0.75]的典型后太古宙沉积岩特征。样品过渡族元素Cr、Co、Ni质量分数较低,与UCC相近,稍低于PAAS;高场强元素Zr、Hf、Nb、Ta、Th质量分数则相对比它们在UCC和PAAS中的质量分数高。泥岩样品的REE、Nb、Ta、Th质量分数明显高于粉砂岩和细砂岩,表明黏土矿物的吸附作用对这些元素的富集有重要的控制作用;但稀土元素的配分模式和特征参数,以及不活动元素之间的比值[如w（La）/w（Co）,w（Co）/w（Th）,w（Cr）/w（Th）,w（Zr）/w（Hf）]并不受粒度效应的影响。微量元素地球化学特征指示沾化凹陷新近系馆陶组和明化镇组沉积岩的源岩以中酸性的长英质岩石为主,可能主要来自盆地东部的胶东隆起区,而南部鲁西隆起区广泛出露的太古宇岩石对盆地供应的碎屑量较小;物源供应的变化表明馆陶组上段沉积时期,东营水系和车沾水系开始衰退,而垦青水系仍较发育。

陆相断陷盆地复式成烃及成藏系统研究——以济阳坳陷沾化凹陷为例

渤海湾盆地油气勘探实践证明 ,丰富的油气资源与富含有机质的生烃凹陷具有十分密切的关系。陆相断陷盆地多沉降中心、多物源供给和充填演化的多旋回性 ,发育了多套有机地球化学特征不同的生油层系和多种油气储集相带组合 ,形成了不同层系、不同圈闭类型的复式油气聚集带 ,并在空间上构成了多个相互交叉、叠置或并列的复合含油气系统。研究表明 ,盆地叠加演化及动力学环境所构成的复式成盆系统孕育了复式成烃系统 ,复式生烃系统的特点决定了油气成藏的复杂性 ,它们控制了复合含油气系统 (多源油藏 )

沾化凹陷渤南洼陷沙河街组原油成因类型及分布特征

利用饱和烃色谱、色—质谱谱图特征及生物标志化合物指标,在沙河街组不同层系烃源岩地化特征差异性对比的基础上,结合原油地化特征,分析了沾化凹陷渤南洼陷已发现油气的成因类型及其分布规律。分析表明,渤南洼陷发育沙三段和沙四段2套有效烃源岩,其中沙四段烃源岩按照地化特征差异又细分为膏盐间和膏盐下烃源岩,三者在伽马蜡烷含量、姥植比和成熟度指标上存在明显差异。油源对比表明,目前已发现的原油存在5种成因类型,且具有一定的分布规律。沙三Ⅰ型和沙三Ⅱ型原油均来源于沙三段烃源岩,但是在成熟度和分布上明显不同,沙三Ⅰ型原油分布在洼陷区的沙三中上亚段,成熟度相对较低;沙三Ⅱ型原油分布层位较深,成熟度较高。沙四Ⅰ型原油分布零星,来源于沙四段膏盐间烃源岩。沙四Ⅱ型原油主要来源于沙四段膏盐下烃源岩,多为自生自储型油藏;混源型油气来源于沙三和沙四段烃源岩。油气分布远离油源中心,多位于断阶带上,断层作用对其分布影响明显。

渤海湾盆地沾化凹陷沙河街组页岩油微观储集特征

页岩油储层微观孔隙储集特征是勘探开发的重要基础资料。采集渤海湾盆地沾化凹陷罗69井沙河街组三段页岩油层段18块岩心样品,利用氩离子抛光—场发射扫描电镜实验,研究页岩油储层孔隙发育特征。沾化凹陷沙三段页岩油层段为泥岩和灰岩的过渡岩性,以灰质泥岩、泥质灰岩和含泥灰岩为主,夹少量灰岩薄层。页岩油层段主要孔隙类型包括泥质碎片间微孔和碳酸盐矿物的溶蚀孔、晶间孔和晶内孔。页岩油层段的储层孔隙主要由泥质部分提供,泥质粒间孔提供的面孔率贡献最大,方解石溶蚀孔对面孔率有一定贡献,晶间孔和晶内孔的面孔率贡献最低。页岩油储层孔隙的孔径属于纳米级和微米级,纳米级孔隙数量占绝对优势,然而储层孔隙面积主要由数量较少的微米级孔隙提供,即页岩油开发的储集空间应该以微米级孔隙为主要对象。

沾化凹陷东营组三段储集层特征

济阳坳陷沾化凹陷东营组岩性油藏勘探近年来获得了较大突破。对东营组三段砂岩储集层沉积演化特征、岩石特征及孔渗特征进行了综合分析,预测其储集层厚度和物性分布规律。沾化凹陷东营组三段为一套扇三角洲沉积体系,储集砂体主要发育在扇三角洲水下分流河道、滩坝、滑塌浊积体等沉积微相内。岩石薄片分析表明,储集层主要属于岩屑质石英砂岩、岩屑砂岩,储集空间以原生孔隙为主,孔隙连通性较好。储集层平均孔隙度为21.15%,平均渗透率为108.08mD,属于中孔中渗储集层。受沉积相的控制,砂岩体呈现凹陷边缘厚、中间薄的特点,岩石物性从凸起向凹陷内具有逐渐变好再变差的分布特征。扇三角洲前缘滑塌成因的湖底扇沉积砂体物性较好,且被周围的浅湖—半深湖相暗色烃源岩包围,是该区东营组最有利的储集砂体。

渤海湾盆地沾化凹陷沙河街组富有机质页岩孔隙分类及孔径定量表征

页岩微观孔隙特征分析和孔径定量表征是页岩油气储层评价和开发的关键。通过岩心观察、薄片鉴定、X-衍射、扫描电镜、氮气吸附等实验手段,分析了渤海湾盆地沾化凹陷富有机质页岩的矿物组成和微观孔隙类型,并对微观孔径进行了定量表征。结果表明:沙河街组页岩具有碳酸盐矿物含量高、粘土矿物含量较低的特征。根据发育位置、成因及产状,将储集空间分为孔隙与裂缝两大类,并制定了孔隙和裂缝的尺度评价标准。孔隙包括矿物基质孔隙和有机质孔隙;裂缝包括构造、层间、超压破裂、成岩和有机质收缩裂缝。氮气吸附等温曲线主要存在3种类型,分别反映了样品中微孔、中孔及宏孔的分布差异。通常氮气吸附实验能更好地表征中孔的发育特征,而扫描电镜所测孔隙更好地表征了宏孔的发育。需要进一步采用二氧化碳吸附、纳米CT及压汞实验定量表征页岩的微孔和宏孔的大小及分布。

渤海湾盆地济阳坳陷沾化凹陷L69井古近系沙三下亚段取心段页岩油勘探有利层段

为探讨渤海湾盆地济阳坳陷沾化凹陷L69井沙河街组三段下亚段(沙三下亚段)取心段页岩油勘探有利层段,对L69井沙三下亚段取心段典型岩相样品和获工业页岩油产量的XYS9井沙三下亚段取心段典型岩相样品,开展了常规热解和多温阶热释法分析,对比研究其含油性与不同赋存形式油含量特征,结合其他影响页岩油产量的因素综合评价页岩油勘探有利层段。结果表明:L69井埋深3 040. 35～3 072. 10 m富有机质纹层状泥质灰岩段,其游离油总量尤其是轻烃校正后游离油S1-1含量显著低于获工业页岩油产量的XYS9井沙三下亚段的含量,并且油饱和指数(OSI)均值仅为67 mg/g,不具有页岩油勘探潜力;埋深3 116. 90～3 126. 70 m含有机质纹层状泥质灰岩段,虽其油饱和指数(OSI)均在100 mg/g以上,平均达204 mg/g(样品数n=8),但游离油总量和轻烃校正后游离油S1-1含量显著低于获工业页岩油产量的XYS9井沙三下亚段的含量,页岩油勘探潜力较低;埋深2 994. 10～3 010. 90 m富有机质层状泥质灰岩、灰质泥岩段,其游离油总量尤其是轻烃校正后游离油S1-1含量和油饱和指数(OSI),与获工业页岩油产量的XYS9井沙三下亚段的含量基本相近或相等,并且该层段微裂缝发育、具异常压力、脆性矿物含量高和存在成熟运移油的贡献,为页岩油勘探的有利层段。