The Upper Jurassic sediments,Marib-Shabwa Basin,Yemen:Lithofacies aspects and sequence stratigraphic analysis

The present study is devoted to understanding the evolution of the Upper Jurassic Sab'atayn Formation in the Marib-Shabwa Basin,Yemen,through a sequence stratigraphic analysis based on integrating datasets of sedimentology,seismic sections,and well logs.The Sab'atayn Formation(Tithonian age)is represented by a series of clastic and evaporites that were deposited under fluvio-deltaic to prodeltaic settings.It is divided into four members including Yah(at the base),upwards to Seen,Alif,and Safir at the top.Two third-order depositional sequences were determined for the Tithonian succession which were separated by three sequence boundaries.These sequences were classified into their systems tracts signifying several sedimentation patterns of progradational,aggradational,and retrogradational parasequence sets.The first depositional sequence corresponds to the early-middle Tithonian Yah and Seen units that can be classified into lowstand,transgressive,and highstand systems tracts.The second sequence comprises the late Tithonian Alif unit that can be subdivided into transgressive and highstand systems tracts.The sandy deposits of the Alif Member(highstand deposits)represent the most productive hydrocarbon reservoir in the basin.The Upper Jurassic sediments in the study area were resulted from a combination of eustatic and tectonic effects.

Highlighting relationships between sand thicknesses,reservoir-seal pairs and paleobathymetry from a sequence stratigraphic perspective:An example from Tortonian Serravallian deposits,onshore Niger Delta Basin

The utilization of sequence stratigraphic concepts in identifying sands and their spatial continuity in distinct gross depositional settings is key,especially in frontier settings where data paucity is a common challenge.In the Baka field,onshore Niger Delta,detailed reservoir correlation guided by sequence stratigraphic framework analysis showed the distribution of sand and shale units constituting reservoirseal pairs(RSP)correlatable across the field.Within the 3rd-order packages,it is observed that the lowstand systems tract(LST)and highstand systems tract(HST)contain more RSPs and thicker 4th-and 5th-order sands than the transgressive systems tract(TST).In terms of bathymetry,it is noted that irrespective of systems tracts,the RSP Index(RI)decreases from the proximal shallow/inner shelf settings to the more distal outer shelf areas.Amongst all three systems tracts,intervals interpreted as lowstand prograding complexes contain the best developed sands and highest RSP.Sand development within the LSTs has been controlled by a pronounced growth fault regime accompanied by high subsidence and sedimentation rates.This is linked to the basinward migration of the sands during prolonged sea-level fall,creating significant accommodation space for sand deposition.On the other hand,the TSTs known to mark periods of progressive sea-level rise and landward migration of sandy facies,show thinner sands enclosed in much thicker,laterally extensive,and better-preserved deeper marine shales.Interpreted seismic sections indicate intense growth faulting and channelization that influenced the syn-and postdepositional development of the sand packages across the field.The initial timing of deformation of subregional faults in this area coincides with periods of abrupt falls in sea level.This approach could be useful for predicting sand-prone areas in frontier fields as well as possible reservoir-seal parameters required for some aspects of petroleum system analysis and quick-look volume estimation.

Method and Description of Sedimentary System Characterization Based on Sequence Stratigraphy

A Oilfield is the most representative mid to deep oil field in the Bohai Sea, with the main oil bearing intervals being the upper and middle Shahejie-3 sections of the Paleogene Shahejie Formation. By combining well seismic analysis, the middle section of Shahejie-3 is divided into high-level system tract and forced lake retreat system tract, corresponding to the II oil formation and I oil formation, respectively. Using sequence stratigraphy methods, based on seismic profiles and drilling lithological cycles, the high stand system tract is divided into 5 stages of delta progradation. The first and second stages are high angle S-type progradation with large sedimentary thickness, the third stage is oblique progradation, and the fourth and fifth stages are S-oblique composite progradation;By combining seismic data, we characterized the large-scale (8 small-scale) progradation bodies of 5 periods, clarified the distribution characteristics of reservoir planes, and laid the foundation for the later exploration of oilfield potential.

Biostratigraphy,Microfacies,Sedimentary Environments and Sequence Stratigraphy of the Late Devonian-Carboniferous Deposits at the Anarak Section,Central Iran

The Late Devonian-early Carboniferous deposits of the Anarak section in northeastern Isfahan,Central Iran,evaluated based on conodont biostratigraphy,sedimentary environment and sequence stratigraphy.According to the field observations,five lithological units were identified.Investigating the conodont fauna of the Late Devonian-Carboniferous(Mississippian-Pennsylvanian)deposits of Bahram,Shishtu,and Qaleh(Sardar 1)formations in Anarak section led to the identification of 67 species of 18 conodont genera,and accordingly 22 conodont biozones were differentiated.The correlation of sea-level change curves,regarding to the conodont biofacies with the global sea-level curve,demonstrates the relative correlation in the mentioned times due to the shallow condition of the central Iran basin compared to the European and American basins.The microfacies analysis led to the identification of 12 microfacies related to the open sea,bioclastic barrier,lagoon and tidal flat sub-sedimentary environments in a homoclinal carbonate ramp environment.Based on sequence stratigraphy studies,three 3rd order sequences were identified.The first sequence,which is of the Late Devonian(upper part of the Bahram Formation,32.5 m),the second sequence(12.5 m)is the Late Devonian(uppermost part of the Bahram Formation),and the third sequence(68 m)is the early Carboniferous(the Shishtu I Formation).

Integration of Sequence Stratigraphic Analysis and 3D Geostatistical Modeling of Pliocene–Pleistocene Delta,F3 Block,Netherlands

This research is focused on the analysis of the sequence stratigraphic units of F3 Block,within a wave-dominated delta of Plio–Pleistocene age.Three wells of F3 block and a 3D seismic data,are utilized in this research.The conventional techniques of 3D seismic interpretation were utilized to mark the 11 surfaces on the seismic section.Integration of seismic sequence stratigraphic interpretation,using well logs,and subsequent 3D geostatistical modeling,using seismic data,aided to evaluate the shallow hydrocarbon traps.The resulting models were obtained using System Tract and Facies models,which were generated by using sequential stimulation method and their variograms made by spherical method,moreover,these models are validated via histograms.The CDF curve generated from upscaling of well logs using geometric method,shows a good relation with less percentage of errors(1 to 2 for Facies and 3 to 4 for System Tract models)between upscaled and raw data that complements the resulted models.These approaches help us to delineate the best possible reservoir,lateral extent of system tracts(LST and/or HST)in the respective surface,and distribution of sand and shale in the delta.The clinoform break points alteration observed on seismic sections,also validates the sequence stratigraphic interpretation.The GR log-based Facies model and sequence stratigraphy-based System Tract model of SU-04-2 showed the reservoir characteristics,presence of sand bodies and majorly LST,respectively,mainly adjacent to the main fault of the studied area.Moreover,on the seismic section,SU-04-2 exhibits the presence of gas pockets at the same location that also complements the generated Facies and System Tract models.The generated models can be utilized for any similar kind of study and for the further research in the F3 block reservoir characterization.

Lithostratigraphy and Characterisation of Paleocene Limestones for Optimal Exploitation (Senegal, West Africa): Comparative Study of the Bandia and Popenguine Quarries

Limestones of different facies in the Senegal basin are most commonly used as aggregates, regardless of their petrographic properties. These differences may influence their behaviour. The aim of this paper is to study the stratigraphy and characterise the limestones of the Bandia and Popenguine quarries. Sampling and geochemical and geotechnical characterisation were carried out on these limestones. The results show the presence of several very different facies in the Paleocene formation. The geochemical study shows that the Bandia limestones (Bd2) have the highest CaCO3 percentages (98.54%) and the highest SiO2 percentages were recorded in the Popenguine limestones (Pop2). The study also gives MDE values of 22.38 and LA of 22, which are acceptable for use in road construction. It is important to carry out a complete study in order to select the right materials for optimal use.

华夏造山系元古宙-早古生代洋板块地层分布与演化

本文按洋板块地层理论与方法,系统收集和梳理了华夏造山系元古宙-早古生代与洋壳生成扩张和俯冲消亡遗存的洋壳残块和洋盆建造(称之为洋板块地层)共96处,均有测年和岩石地球化学分析数据控制,主要包括洋脊、洋岛和洋内弧3类洋壳的火成岩建造,以及海山、远洋深海和海沟3类洋盆内的沉积建造。本文还对洋盆汇聚俯冲的直接产物-陆缘弧和叠加在裂离地块上的火山弧建造(非洋板块地层)系统收集梳理了85处,其中59处有测年和岩石地球化学分析数据控制,26处无测年与地球化学分析,但有实测剖面控制。笔者对上述181处中的39处进行了野外实地考察和相关样品采集与分析。在上述所获大量资料的基础上,本文主要以图解形式展示了华夏造山系元古宙-早古生代主要洋板块地层分布与构造演化历程。横向上将华夏造山系划分为江绍-郴州-钦防对接带(主要含陈蔡-龙游、神政桥-神山、鹰扬关和糯垌4个含蛇绿岩残块增生楔,以及绍兴-兰溪增生弧和钦防残余洋盆)、武夷-赣州多岛弧盆系(主要含罗霄弧、赣州弧间盆地、北武夷弧和南武夷弧以及南平-宁化构造混杂岩带)和东南沿海多岛弧盆系(主要含龙泉-政和-大埔、贵子-石窝2个含蛇绿岩残块增生楔,以及伴生的云开地块-弧、粤南弧-弧背盆地和东南沿海地块);纵向上据洋板块地层和相关火山弧时空分布,从老至新划分出华夏造山系(华南洋)的7个构造演化阶段:(1)约1800~1200 Ma,洋盆拉张形成期;(2)约1200~820 Ma,洋盆扩张与汇聚转换期;(3)约820~635 Ma洋盆汇聚俯冲、弧-弧和弧-陆增生峰期;(4)约635~541 Ma洋盆汇聚与扩张转换期;(5)约541~458 Ma洋盆扩张期;(6)约458~443 Ma洋盆汇聚俯冲、弧-陆增生峰期;(7)约443~420 Ma洋盆关闭与陆-陆碰撞、残留洋(海)期。

筠连地区上二叠统乐平组层序地层及沉积相研究

四川南部筠连地区乐平组煤层气资源储量大,勘探程度总体较低,制约了煤及煤系气资源的开采。煤层聚集、砂岩储层展布受控于沉积相及层序地层格架控制。为探究研究区内煤层发育特征及煤层聚集的沉积控因,以钻井和岩心资料为基础,利用层序地层学原理,识别出区内乐平组发育的Ⅲ级层序界面并划分层序,构建层序地层格架;厘清研究区含煤地层名称;利用岩相标志及测井响应特征进行地层对比、单井沉积相划分及连井沉积相对比,明确沉积相在各层序内的发育特征。结果表明,研究区乐平组共存在四个层序界面,依据四个层序界面划分出三个Ⅲ级层序。以测井响应特征为主体,共识别出两类沉积相,五类沉积亚相及九类沉积微相。第一层序(SQ1)和第二层序(SQ2)主要发育河流相,第三层序(SQ3)发育潮坪相。在剖面上,整体表现为由河流相至潮坪相的演化特征;自西向东体现为河流-潮坪-潟湖相的演化趋势。

滨里海盆地东缘北特鲁瓦油田石炭系层序地层与沉积演化特征

根据三维地震、测井及钻井取心等资料,结合Vail的层序划分方案,在滨里海盆地东缘北特鲁瓦油田石炭系碳酸盐岩台地内识别出7个地震层序界面及7个钻井层序界面,并将KT-Ⅰ油层组划分为3个半三级层序,KT-Ⅱ油层组划分为3个三级层序。纵向上层序格架内沉积环境由开阔台地、局限台地至蒸发台地演化。根据研究区层序格架内的古地貌恢复及沉积演化研究,将研究区古地貌—沉积演化划分为3个阶段:台地初始隆坳分异期(SQ2-SQ3层序)、差异抬升与沉积分异定型期(SQ4层序)及继承发育期(SQ5-SQ7层序)。进一步分析认为,层序格架控制下的隆坳格局分异控制了白云岩亚类在平面上的分布,低部位以泥晶云岩—膏盐岩组合和泥晶云岩—泥晶灰岩组合为主,主要为潟湖相沉积;而高部位则以泥粉晶云岩、细粉晶云岩和残余颗粒泥晶云岩为主,发育云坪相及云化颗粒滩相沉积。结果表明,区内KT-Ⅰ油层组沉积期并非前人认为的西高东低剥蚀后沉降充填,而是继承性差异沉降的结果,古地理格局总体具有“东台西槽、北高南低”特征,其始终控制着有利相带和优质储集层的发育展布。这一认识对滨里海地区油气勘探开发战略选区具有重要的指导作用。

河口海岸沉积层理特征与形成机制

河口海岸地处海陆交界带,其沉积层理特征与形成机制是沉积动力学、动力地貌学和地层学等学科方向的研究热点,对评价海岸工程环境效应、重建沉积古环境等具有重要参考价值。通过梳理河口海岸区域径流、潮汐、波浪等多种动力因子作用的研究成果,归纳不同动力主导作用形成的沉积层理特征,剖析3种基本动力对沉积层理塑造的动力学机制,阐释洪水、风暴偶发动力因子以及生物扰动、海平面变化、围垦工程等其他影响因子对沉积层理形成和保存的作用机理。同时,总结了数值模拟手段在沉积层理形成和破坏机制解译方面的应用及取得的机理认知,提出在河口海岸沉积层理时空尺度认知、多因素耦合反演模型开发应用等方面有待进一步研究的科学问题。

巨厚煤层物质组成特征与成因机制——以柴北缘鱼卡地区中侏罗统为例

厚煤层蕴含着丰富的地质信息,在全球碳循环中扮演着重要的角色。国内外深时地层中厚煤层广泛分布,近年来其成因机制逐渐成为煤地质学的研究热点。为明晰等时层序地层格架中的巨厚煤层的物质组成特征与形成机理,选取柴北缘鱼卡地区中侏罗统层序S1湖侵体系域发育的巨厚煤层M7为研究对象,等间隔连续采样并进行室内显微组分与矿物鉴定,依据煤层关键界面的识别原理、显微组分与矿物的古环境指示意义进行综合分析。结果显示:显微组分中镜质组体积分数最高(48.5%),惰质组体积分数同样较高(37.22%),类脂组所占比例很低,仅为3.32%。矿物组分体积分数较为稳定,平均值为10.96%。依据煤层与碎屑沉积的交替出现、显微组分与矿物体积分数在垂向上的变化趋势,识别出了多种关键界面,包括陆化面(TeS)、陆地暴露面(ExS)、沼泽化面(PaS)、湖侵淹没面(GUTS)与可容空间转换面(ARS)。沿沉积倾向在向陆与向湖方向分别选择钻孔,与鱼卡煤矿对比分析沼泽环境垂向演化过程。鱼卡煤矿巨厚煤层M7识别出4个沉积旋回,向陆以及向湖方向的YQ6–22与YQ6–12中由陆源碎屑、湖相沉积所分隔的M7–1—M7–3则均识别出3个沉积旋回。发现了巨厚煤层中蕴含的高分辨率层序,经过分析划分为4个四级层序,结合煤层中关键界面所对应的层序界面,揭示了巨厚煤层的成因机制。建立了层序地层格架中的多期泥炭沼泽垂向叠置模式,可进一步应用于国内外更多深时地层中巨厚煤层的研究。

华北克拉通矽卡岩型富铁矿成矿关键控制因素:来自地层学的制约

华北克拉通矽卡岩型富铁矿床成矿关键控制因素一直是科学研究的热点和难点,也是制约下一步找矿方向和进一步实现找矿突破的关键。本次工作基于对华北克拉通典型矿床矿体分布规律的研究,基于地层学分析,研究了矿体分布的关键控制因素和制约机理。华北克拉通各典型矽卡岩型富铁矿床主矿体与围岩层系、岩溶层、膏岩层等的空间关系密切,主要分布于中奥陶统峰峰组二段、下马家沟组二段和上马家沟组二段,处于主要含膏层的上覆强岩溶层。地层学因素对矽卡岩型富铁矿床成矿的关键控制作用主要表现在四个方面:岩溶层系的垂向分布制约富铁矿体就位的有利空间;不整合面的发育控制岩溶系统发育的程度,影响富铁矿体规模;层序地层对岩溶期次的约束作用,限定了岩溶发育层位以及富铁矿层的分布;膏盐岩层指示阶段性强岩溶作用的底界,限定富铁矿体赋存的有利空间下限。根据研究认识,建立了华北克拉通矽卡岩型富铁矿床地质找矿模型,提出七个潜在成矿空间层段,其中包括三个主力成矿层段,并指出了下一步重点找矿及研究方向。

沉积盆地古水深恢复方法与研究进展

古水深分析对古环境重建、盆地分析、层序地层学研究、古地貌恢复以及生、储、盖层条件的评价都有重要意义。古水深分析通常有古生物法、沉积学法、地球物理法、地球化学法及数字模拟法,各种方法优缺点并存,尽管某些方法在特定地质条件下存在优势,但在恢复同一环境的古水深时,不同方法还是存在其偏差;这些方法多以定性为主,许多方法易受自然条件限制,且对样品可靠性要求高,一定程度上限制了古水深研究。古水深恢复建议综合考虑地质背景、环境演化、研究地质体特征及地质资料情况等多种因素,多方法研究相互约束,以期更客观地再现古水深变化规律。

龙门山中段北川通口剖面中二叠统栖霞组地层沉积特征

川西龙门山前带栖霞组是近期油气勘探的热点,龙门山中段栖霞组勘探程度低,明确其地层沉积特征,对于天然气勘探具有重要的指导意义。基于对龙门山中段北川通口剖面实测,结合薄片鉴定和主量、微量元素分析,对栖霞组层序地层及沉积特征进行了研究,明确了沉积环境。北川通口剖面梁山组—栖霞组识别出2个三级和1个四级层序界面,划分为1个三级层序和2个四级层序。梁山组—栖霞组发育滨岸—沼泽、开阔台地及台地边缘3种沉积相,开阔海、滩间海、台内滩和台缘滩4种亚相,台内生屑滩、台缘生屑滩和台缘砂屑、生屑滩3种微相。栖一段至栖二段下部整体处于开阔台地,栖二段中上部则处于台地边缘,建立了龙门山中段栖霞组镶边碳酸盐岩台地沉积模式。栖霞组沉积期整体处于温暖、湿润、富氧、古生物大量繁殖的海水—陆表海沉积环境,栖二段中上部高位体系域Sr/Ba比值整体最低,MgO/CaO比值最高,平均古水温高,V/(V+Ni)、V/Cr低值,古盐度m值明显较高,代表远离陆地的浅水、高能台地边缘沉积环境,厚大高能台缘砂屑、生屑滩发育,是规模优质滩相孔隙型白云岩储层发育有利部位。龙门山中段栖二段与北段、南段具有相似的沉积相带和储集条件,是栖霞组油气勘探的有利区带,有望成为实现规模增储的重要战略接替阵地。

广东西樵山40—50 ka B P地质遗迹与古人类活动新发现

1958—1999年,在广东省佛山市南海区西樵镇一带发现了众多记录了史前人类活动的石器地点,石器中包括双肩石器和细石器。迄今为止,“西樵山遗址”被认定是4—7 ka B P的大型新石器时期采石场和加工场。2011—2022年,笔者经多次地质遗迹和地质环境调查,在西樵山东南麓富贤村北面发现了良好的第四纪地层剖面。地质探槽剖面测量和地质年代学研究表明:富贤地点存在2套原始沉积地层:上部为第四纪全新世沼泽相地层,AMS14C校正年龄为5052—5409 a B P;下部为第四纪晚更新世冲积-洪积相地层,AMS14C校正年龄为38420—40502 a B P,OSL (光释光)年龄为41.977—43.796 ka B P;在晚更新世地层中发现2层含旧石器层,下部A1层主要石器类型有较大型刮削器、尖刃器、舌型刃器及小型石片工具,如各类刮削器、锯齿刃器、凹缺器、石刀、使用石片、石核等,包括带铤斧型小石刀;上部A2层明显出现更多石刀类型且常常附带修背和修铤工作,其中一件用于生产细小长石片的原始楔形石核引人关注。据平均沉积速率计算,下部A1石器层年龄为46.511—47.325 ka B P,上部A2石器层年龄为41.977—42.167 ka B P;距今大于5 ka的全新世沉积物中的石制品数量虽少,但器物类型仍具有明显继承性与发展性特点。本文的发现更新并延伸了西樵山国家地质公园和“西樵山文化”的内涵,首次突破了珠江三角洲地区有确切年代的晚更新世旧石器遗存的纪录,追踪到大约40—50 ka现代人在华南沿海的足迹,揭示了同期石器工业的面貌及其文化内涵的发展特征和演变。研究表明,在MIS3间冰段相对湿热时期以及MIS2相对干冷阶段,富贤地点的古人类面临环境变化的挑战而开启了新的生计模式,这对于揭示现代人对全球和区域环境变化的响应与适应的科学问题具有重要意义。

研究生学位课程“层序地层学”的教学改革与实践

“层序地层学”是地质学、地质资源与地质工程以及地球物理学等专业研究生的学位课程。随着研究生培养形势和需求的不断变化,原有的教学效果已不能满足新形势下社会对学生专业能力日益增长的要求。根据新时代研究生培养需求和课程教学中存在的问题,通过更新课程内容、调整课程结构、提升教学方法、建设线上课程、改革考核方式等进行了课程教学改革与实践,有效提升了课程教学质量。

乍得Doseo盆地东部坳陷下白垩统Kedeni组层序地层格架与沉积体系分布

中非裂谷系Doseo盆地Kedeni组油气勘探获重大突破,但对该主力层系层序地层和沉积充填方面的认识仍不明确,成为制约下一步油气勘探的关键。以Doseo盆地东部坳陷Kedeni组为研究对象,运用层序地层学及沉积学理论,结合岩心、测录井和地震资料,明确了Kedeni组层序地层格架及沉积体系展布。研究表明:Kedeni组可识别出3个层序界面,划分为2个三级层序(SQⅠ、SQⅡ),对应于2个“湖进—湖退”旋回。Kedeni组沉积物主要来自4个方向,并发育6种沉积相类型,沉积相展布具有东西分异、垂向继承发育的特征。正常三角洲分布于东南部缓坡带及中央低凸带,辫状河三角洲主要分布于东北部长轴方向和南部陡坡带,扇三角洲和近岸水下扇发育于北部陡坡带边界断层下降盘,湖底扇主要分布于西部凹陷深湖区。纵向上,SQⅠ层序的骨架砂体规模整体大于SQⅡ层序,且在每个三级层序内部,低位域和湖侵域组成的下部单元中三角洲—水下扇砂体更为发育。Kedeni组层序与沉积演化主要受到主干断层的构造活动、“南多北少”的物源供给、“半干旱—湿润”气候的转变等因素控制。在层序—沉积模式指导下,认为北部陡坡带小规模扇三角洲前缘—近岸水下扇砂体、南部及东北部大范围正常三角洲前缘、辫状河三角洲前缘砂体及西部凹陷深湖区湖底扇砂体可作为区内有利储集层的勘探目标。

川北—鄂西上二叠统富有机岩沉积与地球化学特征

【目的】随着非常规油气理论的发展,沉积有机质富集机理再次成为热点研究,其中有机质富集主控因素成为争论的焦点。以往的研究对沉积过程的分析较少,这可能是存在争论的原因之一。【方法】结合沉积学与地球化学研究方法,在分析层序地层学和沉积环境的基础上,详细开展元素地球化学研究,讨论富有机岩沉积有机质富集机理。【结果】四川盆地北部和鄂西盆地上二叠统吴家坪组自下而上分为吴一段、吴二段和吴三段,大隆组自下而上分为大一段和大二段。吴家坪组至大隆组自下而上总共分为五个三级层序SQ1~SQ5。由层序地层学分析将广利海槽和鄂西海槽的发展分为四个阶段,分别为初始、快速发展、高潮稳定和萎缩阶段。初始阶段主要发育SQ2时期斜坡相暗色硅质灰岩,快速发展阶段主要发育SQ3时期陆棚相钙质页岩,高潮稳定阶段主要发育SQ4时期盆地相黑色硅质岩,萎缩阶段主要发育SQ5时期斜坡相石灰岩。含异常高有机质的甜点段主要形成于SQ3高位域至SQ5海侵域沉积期,在该时期Fe、Cu、Ni和Zn营养元素周期性富集,Mo、V、Fe/Al和S等氧化还原敏感元素均表现为较高的水平,热液强度参数Al/(Al+Fe+Mn)和Al-Fe-Mn三角图均指示频繁的热液活动特征。【结论】在甜点段,高营养元素含量和初级生产力水平的出现早于强还原条件,说明沉积水体的氧化还原条件主要受控于沉积有机质沉降埋藏过程中对氧的消耗,有机质的富集主要受较高初级生产力的控制。营养物质P、Si、Fe、Zn的供应主要与裂陷槽形成过程中深部热液活动和周围火山活动有关,这些构造活动周期性带来大量营养物质提高了初级生产力水平。因此海洋表层高的初级生产力水平是甜点段异常高有机质富集的启动和基础条件,而海洋底部水体较强的还原环境是有机质埋藏和保存的关键因素。

川东北普光地区下三叠统蒸发岩沉积特征与演化及其对钾盐矿形成的控制作用

四川盆地中—下三叠统地层中发育大量膏-盐沉积,其中与石盐共伴生杂卤石(被命名为“新型杂卤石钾盐矿”)的大量发现和重新评估引起了近年来的广泛关注。但当前对此类杂卤石的研究主要集中在其矿物发育特征与成因类型等方面,对于其发育地层的沉积特征与演化规律的精细剖析及其对杂卤石形成的控制作用研究较少。本文利用川宣地1井连续取心的目的层段岩心资料进行了沉积微相和高精度层序地层学分析。共识别出14种沉积微相类型,并将其划分为6个微相组合,依次代表从局限台地到蒸发台地不同的沉积相带及能量、环境特征。在此基础上根据沉积微相的纵向发育演化、地层厚度以及典型诊断界面等信息,划分出4个四级沉积层序以及其内部的多个五级旋回。研究认为川东北地区与石盐共伴生的原生杂卤石是明显受不同级别海平面波动影响和控制的,主要发育在四级层序海退末期与五级旋回海侵的叠加时期,前者的强蒸发条件为杂卤石的形成提供了重要基础,但后者带来的海水补给则是其形成的必要条件。

基于动态物源演变的“源-汇”分析——以琼东南盆地松南地区陵水组为例

琼东南盆地作为中国重点含油气盆地,其勘探重点逐渐向盆内深水区拓展。作为盆内重要物源的松南地区,其构造地貌存在典型的坡控特点,与盆缘断控地区具有明显差异。海平面的周期性旋回变化,致使油气勘探过程中可能忽视早期局部物源存在,制约了松南地区规模性储集体的寻找工作。本文以物源的动态演化为核心,认为松南地区主要发育“动态多期型”和“动态淹没型”2大动态物源体系。前者在陵水组沉积时期实际成扇的有效供源面积呈递减趋势,于陵三段低位期、高位期及陵二段低位期形成近源扇三角洲沉积;后者在陵三段低位域时期存在规模性局部物源,发育扇三角洲沉积体系。松南地区动态物源体系受海平面旋回变化与构造地貌共同影响,隆起区整体呈现“早期供源成扇,晚期作为水下隆起控坝”的沉积规律。对动态物源体系“源-汇”要素的定量分析显示,源区规模、渠道深度及古水系组合样式是松南地区动态物源体系砂体沉积的主控因素,即低水位期规模性物源、高陡地形强下切沟道、平缓背景下多级复合古水系,有利于汇水区规模性扇体发育。