南苏门达腊盆地中国石油合同区块成藏组合分析

南苏门达腊盆地是典型的弧后裂谷盆地，其演化经历了4大构造期：始新世中期到渐新世早期为裂谷发育期；渐新世晚期到中新世初期为裂谷-坳陷过渡期；中新世早期到末期为坳陷期；上新世早期至今为盆地反转期。盆地形成以始新统湖相泥岩、生储盖组合特征、圈闭构造风格与油气富集特点，可将其油气成藏组合划分为深部组合、下部组合、中部组合和上部组合。深部组合以新生古储式潜山油气藏为主；下部组合以自生自储式油气藏为主；中部组合以古生新储式油气藏为主；上部组合以与晚期反转构造有关的油气藏为主。3个中国石油合同区块发现的成藏组合各不相同，每一区块还具有发现其它成藏组合的潜力。     

断陷盆地中含油气系统的特征

我国东部断陷盆地含油气系统具有与盆地结构及勘探程度相对应的多层次性,其基本单元是以单一生烃凹陷(洼陷)为中心的子系统。复式含油气系统的基础是在盆地中存在不同地质时期的活跃烃源岩,它是强烈的多期块断运动和高地热场的产物。断层的活动强度及活动时间和期次控制了盆地中油气系统的分布及特征。用生物标志物进行油源对比可以划分系统并确定其分布范围,从而进一步研究成藏规律。以济阳坳陷中的沾化凹陷为例说明复式含油气系统的形成及特征。盆地中三套主要的生油层系分别是始新统的沙河街组第三段、第四段及渐新统的沙河街组第一段。这几套生油岩形成于不同的沉积环境,经历了不同的成熟演化阶段并形成了各自的原油。三类原油的特征明显地反映在其中生物标志物的组成上。以这三套生油层系为核心,三个成藏期为标志,形成了复式含油气系统。这些系统有着各自的生储盖组合,运移通道及分布范围,它们在空间中叠置或交叉,在时间上呈现阶段性。     

南海北部多幕裂陷作用与含油气系统

南海北部的断陷盆地经历了早第三纪裂谷期和晚第三纪及第四纪裂后期二个演化时期,具多幕裂陷作用.构造与沉积的耦合作用,使盆地的演化具有多个阶段,包括构造地层序列的多幕性和各幕沉积充填样式的不同,以及因此形成的不同时期的烃源岩,组成了多个含油气系统;同时,断裂的多次活动,使早期含油气系统中已成藏的油气再次运移并再次聚集成藏.珠江口盆地珠三坳陷裂谷期可分为三个演化幕,而晚始新世末的一次盆缘张断事件造成了Ⅱ、Ⅲ幕之间沉降中心的迁移,发育了不同类型的古湖泊,形成了不同有机质类型的烃源岩,组成了多个含油气系统.裂后期的裂陷幕与油气的再次运移和再次成藏密切相关.     

珠一坳陷惠州西凹混源油研究

详细的原油和烃源岩抽提物分析表明,珠江口盆地东部地区存在两套有效的烃源岩。源自始新统湖相烃源岩的典型原油具有丰富的C304-甲基甾烷和相对较低的双杜松烷化合物(T)特征。与之相反,源自渐新统恩平组的典型原油则具有高含量的双杜松烷化合物(T)、高Pr/Ph比值以及相对低含量的C304-甲基甾烷。然而,绝大多数原油的化学组成特征与那些未知烃源岩不相匹配,而与这两套烃源岩的混合特征相一致。其油源对比结果表明,西江24-3、西江24-1原油主要来自西江24洼文昌组和恩平组烃源岩,而西江30-2原油主要来自西江30洼文昌组烃源岩。原油的化学组成受洼陷内烃源岩组合的控制,且油气具有近源成藏、短距离运移的特点。     

GENERATION AND ACCUMULATION OF HYDROCARBONS IN A DEEP “BURIED HILL” STRUCTURE IN THE BAXIAN DEPRESSION,BOHAI BAY BASIN,EASTERN CHINA

Significant volumes of hydrocarbons have been produced from karstified Infracambrian dolomites in a “buried hill” structure at depths of 5860m to 6027m and reservoir temperatures of 190–201°C in well Niudong‐1 in the Baxian depression, Bohai Bay Basin. This is the deepest oil and gas discovery made in eastern China so far and structures at similar depths are targets for exploration elsewhere in the Bohai Bay Basin. However the origin and accumulation of the hydrocarbons at Niudong‐1 is not clear: they may have been generated from highly mature lacustrine source rocks in the Sha‐4 Member of the Eocene Shahejie Formation; or they may have been derived from thermal cracking of previously‐accumulated oil. This paper investigates the organic geochemistry of the Sha‐4 Member source rocks and the crude oils produced from well Niudong‐1. Analyses of molecular parameters show that the hydrocarbons originated from the pyrolysis of organic matter in Sha‐4 Member source rocks, rather than from cracking of previously accumulated oil. Infracambrian dolomites at the Niudong‐1 location may have been charged with low‐maturity oil around 34 Ma ago, when the Sha‐4 Member source rocks were buried to depths of about 3500m and first entered the oil window. During further rapid burial to more than 5500m starting at about 15Ma, these source rocks became highly mature and generated significant volumes of light oil and gas. Overpressures in the source rock interval forced these hydrocarbons to migrate into unconformably‐underlying Infracambrian dolomite reservoir rocks at the Niudong‐1 structure. Significant risks are associated with future exploration of deep “buried hill” structures in the Bohai Bay Basin. Not all the structures were charged with oil, and accumulations were not necessarily preserved during Neogene burial as the reservoirs may have been breached by faulting.     

THE GENERATION OF IMMATURE OILS IN THE LACUSTRINE JIYANG MEGA-DEPRESSION, BOHAI BAY BASIN, CHINA

The lacustrine Jiyang mega-depression (Bohai Bay Basin, eastern China) produces important volumes of immature oils. These oils were generated at shallow burial depths by source rocks which have not entered the conventional oil window. Oil-source correlation studies have determined that the oils were mainly generated by source rock intervals in the Es4 and Es1 Members of the Paleogene Shahejie Formation, which were deposited in saline- to brackish-water and brackish-water lacustrine conditions, respectively. Minor quantities of oil came from Es3 Member source rocks deposited in freshwater conditions.
Samples of the Es4, Es3 and Es1 source rocks underwent artificial maturation at low temperatures (100–400°C). For the Es4 sample, the hydrocarbon generation characteristics of soluble organic matter and kerogen were investigated. The results of the experiments show that soluble organic matter made a greater contribution than kerogen to the immature oil (76% versus 24%). A comparison of the results of the thermal simulation experiments with the naturally-occurring maturation profile shows that various factors influenced the generation of the immature oils. Firstly, the Es4 and Es1 Members include intervals enriched in algal material. Secondly, most of the immature oil is derived from soluble organic matter. Finally, the saline depositional environment was favorable for the preservation of organic matter.     

西藏伦坡拉盆地第三系及其含油性

伦坡拉盆地位于藏南褶皱系昂拉仁错—奇林湖复向斜带北部边界断裂的南侧。它是一个东西长约200公里,南北宽约20公里,面积约4000平方公里的陆相含油盆地。盆地的石油普查工作开始于1956年。从1967年起,地质部第四普查勘探大队在此开展了大规模的多工种的石油普查工作,现将已经取得的一些资料和本人的初步看法提出来，与同行们讨论。     

尕斯库勒渐新统下部油藏原油成因地球化学

有机地球化学分析表明,尕斯库勒渐新统下部油藏原油为典型的盐湖相油,既有低熟油特征也有成熟油特征。油源对比表明,尕斯库勒渐新统下部油藏原油主要来自邻区埋深大于3500m的下第三系接近成熟或成熟的烃源岩。下第三系烃源岩形成于高钙多盐、强还原条件下的盐湖环境。烃源岩中盐和高含量的碳酸盐对甾、萜类化合物异构化有明显的抑制作用,导致下第三系烃源岩成熟滞后。尕斯库勒渐新统下部油藏中,目前找到的原油主要为低熟油,未熟油与成熟油发现不多。经分析,成熟的烃源岩分布在埋深大于4000m的深层,因此,深层具有寻找成熟油的潜力。     

COMPOSITION OF DIAMONDOIDS IN OIL SAMPLES FROM THE ALPINE FORELAND BASIN,AUSTRIA: POTENTIAL AS INDICES OF SOURCE ROCK FACIES,MATURITY AND BIODEGRADATION

Twenty‐seven oil samples from Cretaceous, Eocene and Rupelian reservoir rocks in the Alpine Foreland Basin (Austria) were analysed to evaluate the composition of diamondoid hydrocarbons using gas chromatography – triple quadrupole mass spectrometry. The oils were generated from marly and shaly Oligocene source rocks buried beneath the nappes of the Alpine foldbelt to the south of the study area. Diamondoid hydrocarbons were detected in the saturated fraction of all the analysed oils. A biodegraded oil sample from a shallow reservoir in the NE part of the study area showed an enrichment in diamondoids due to the molecule's high resistance to microbial degradation. Variations in the organic matter type of the source rock facies and differences in maturity are known to influence the composition of diamondoids. However in this study, biomarker‐derived maturity parameters do not show a convincing correlation with diamondoid maturity parameters. Moreover, no cracking trend based on biomarkers and diamondoid concentrations was observed. The results indicate that the composition of diamondoids in oils from the Austrian part of the Alpine Foreland Basin is mainly controlled by heterogeneities in the Lower Oligocene source rocks, including the occurrence of a redeposited source rock succession in the western part of the study area. By contrast, EAI‐1 (the ethyladamantane index) shows a good correlation with various maturity parameters and seems to be independent of source rock facies.     

PETROLEUM GEOLOGY AND HYDROCARBON POTENTIAL OF THE GUBAN BASIN,NORTHERN SOMALILAND

The Guban Basin is a NW‐SE trending Mesozoic‐Tertiary rift basin located in northern Somaliland (NW Somalia) at the southern coast of the Gulf of Aden. Only seven exploration wells have been drilled in the basin, making it one of the least explored basins in the Horn of Africa – southern Arabia region. Most of these wells encountered source, reservoir and seal rocks. However, the wells were based on poorly understood subsurface geology and were located in complex structural areas. The Guban Basin is composed of a series of on‐ and offshore sub‐basins which cover areas of 100s to 1000s of sq. km and which contain more than 3000 m of sedimentary section. Seismic, gravity, well, outcrop and geochemical data are used in this study to investigate the petroleum systems in the basin. The basin contains mature source rocks with adequate levels of organic carbon together with a variety of reservoir rocks. The principal exploration play is the Mesozoic petroleum system with mature source rocks (Upper Jurassic Gahodleh and Daghani shales) and reservoirs of Upper Jurassic to Miocene age. Maturity data suggest that maximum maturity was achieved prior to Oligocene rift‐associated uplift and unroofing. Renewed charge may have commenced during post‐ Oligocene‐Miocene rifting as a result of the increased heat flows and the increased depth of burial of the Upper Jurassic source rocks in localised depocentres. The syn‐rift Oligocene‐Miocene acts as a secondary objective owing to its low maturity except possibly in localised offshore sub‐basins. Seals include various shale intervals some of which are also source rocks, and the Lower Eocene evaporites of the Taleh Anhydrite constitute an effective regional seal. Traps are provided by drag and rollover anticlines associated with tilted fault blocks. However, basaltic volcanism and trap breaching as a consequence of the Afar plume and Oligocene‐Miocene rifting of the Gulf of Aden cause considerable exploration risk in the Guban Basin.     

AN INTRODUCTION TO THE PETROLEUM POTENTIAL OF NIGER

The Republic of Niger can be divided into two sedimentary and tectonic provinces: a Palaeozoic platform-type province in the north and west, and a series of Mesozoic grabens in the east.
Thick Palaeozoic successions are present in the NW (in the Tamesna-Talak area of the Iullemeden Basin), and the NE (in the Djado Basin). The petroleum potential of these areas is not yet proven. By analogy with the Algerian Illizi Basin and the Libyan Murzuk Basin, Silurian source rocks together with Ordovician, Devonian and Carboniferous sandstone reservoir units may occur here.
In East Niger, a complex rift system, whose sedimentary fill ranges in age from Late Jurassic to Early Tertiary, has proven petroleum potential. Reservoir rocks are mainly Cretaceous to Eocene sandstones, sourced by Cretaceous marine shales and Oligocene lacustrine shales.
This paper reviews the petroleum geology of Niger, and assesses potential exploration targets. Commercial developments can shortly be expected following the construction of an export pipeline from Chad to Cameroon, and the resumption of drilling activity in the Agadem and Djado Basins.     

BIOMARKER GEOCHEMISTRY OF PALEOGENE CRUDE OILS AND SOURCE ROCKS FROM THE RAOYANG SAG,BOHAI BAY BASIN,NE CHINA: AN OIL – SOURCE ROCK CORRELATION STUDY

This study presents a systematic geochemical analysis of Paleogene crude oils and source rocks from the Raoyang Sag in the Jizhong sub-basin of the Bohai Bay Basin (NE China). The geochemical characteristics of fifty-three oil samples from wells in four sub-sags were analysed using gas chromatography (GC) and gas chromatography – mass spectrometry (GC-MS). Twenty core samples of mudstones from Members 1 and 3 of the Eocene-Oligocene Shahejie Formation were investigated for total organic carbon (TOC) content and by Rock-Eval pyrolysis and GC-MS to study their geochemistry and hydrocarbon generation potential. The oils were tentatively correlated to the source rocks. The results show that three groups of crude oils can be identified. Group I oils are characterized by high values of the gammacerane index and low values of the ratios of Pr/Ph, Ts/Tm, 20S/(20S+20R) C₂₉ steranes, ββ/(ββ+αα) C₂₉ steranes, C₂₇ diasteranes/ C₂₇ regular steranes and C₂₇/C₂₉ steranes. These oils have the lowest maturity and are interpreted to have originated from a source rock containing mixed organic matter deposited in an anoxic saline lacustrine environment. The biomarker parameter values of Group III oils are the opposite to those in Group I, and are interpreted to indicate a highly mature, terrigenous organic matter input into source rocks which were deposited in suboxic to anoxic freshwater lacustrine conditions. The parameter values of Group II oils are between those of the oils in Groups I and III, and are interpreted to indicate that the oils were generated from mixed organic matter in source rocks deposited in an anoxic brackish–saline or saline lacustrine environment. The results of the source rock analyses show that samples from Member 1 of the Shahejie Formation were deposited in an anoxic, brackish – saline or saline lacustrine environment with mixed organic matter input and are of low maturity. Source rocks in Member 3 of the Shahejie Formation were deposited in a suboxic to anoxic, brackish – saline or freshwater lacustrine environment with a terrigenous organic matter input and are of higher maturity. Correlation between rock samples and crude oils indicates that Group I oils were probably derived from Member 1 source rocks, while Group III oils were more likely generated by Member 3 source rocks. The Group II oils with transitional characteristics are likely to have a mixed source from both sets of source rocks.     

珠江口盆地白云凹陷北坡—番禺低隆起天然气成因类型及其烃源探讨

珠江口盆地白云凹陷北坡—番禺低隆起天然气的成因及其烃源问题,近年来引起了石油地质专家们的广泛关注。在前人工作基础上,根据天然气的组成、碳同位素及其甾萜类生物标志化合物特征,重点对天然气的成因类型及其烃源构成进行了深入分析。依据天然气甲烷碳同位素和乙烷碳同位素分布特征,将天然气成因类型划分为生物气、亚生物气、成熟偏煤型混合气、成熟—高熟偏油型混合气及成熟—高熟煤型气5类。天然气伴生凝析油的甾萜类生物标志物具有富集型煤系有机质和分散型Ⅲ型有机质两种明显不同的特征,由此认为油气主要来自成熟—高熟的渐新统恩平组煤系烃源岩、滨浅湖相烃源岩及始新统文昌组滨浅湖相烃源岩。通过油气地质及油气地球化学综合剖析,指出该区不仅具有巨大的天然气勘探潜力,而且具有石油资源勘探前景。     

柴达木盆地西部南区第三系原油成熟度特征

原油成熟度特征是原油地球化学研究的重要组成部分。通过对柴达木盆地西部南区第三系原油的色谱-质谱分析,在饱和烃和芳烃成熟度参数、生物标志物绝对浓度和热不稳定化合物的定量与定性分析基础上,详细剖析了该区原油的成熟度特征。研究结果表明:柴达木盆地西部南区第三系原油主体为未熟-低熟油,不存在混源造成未熟-低熟假象的可能性。成熟原油仅出现在花土沟、狮子沟和砂西地区。柴达木盆地西部南区有效烃源岩的发育特征,佐证了大量未熟-低熟原油存在的可能性。     

珠江口盆地珠一坳陷惠陆油区含油气系统与油气运聚成藏模式

珠江口盆地珠一坳陷惠陆油区具有3个经油气勘探证实的含油气系统,分别是惠西、惠东、惠中北含油气系统。惠西与惠东含油气系统烃源岩为始新统文昌组中深湖相;而惠中北含油气系统烃源岩为下渐新统恩平组煤系。惠陆油区油气运聚成藏模式存在2种类型即:古近系半地堑洼陷自源型油气运聚成藏模式与三角洲砂岩及生物礁外源型油气运聚成藏模式。前者油气运聚成藏的主控因素,主要取决于半地堑洼陷内生烃灶充足的烃源供给、优质储盖组合及圈闭的良好配置。这种油气藏分布于半地堑洼陷之内,具有自生自储近源运聚成藏特征,由于此类油藏埋深较深,深部储层物性优劣是油气成藏的关键;后者油气运聚成藏主控因素,则主要取决于富生烃洼陷及其附近的油源断裂和输导砂体及不整合面组成的复合运聚疏导体系与浅层不同类型有效圈闭的连通配置和相互衔接耦合。     

渤海湾盆地早第三纪构造样式的演化

在伸展和走滑两种活动体制下,渤海湾盆地早第三纪构造样式有五种类型.孔店-沙四期主要发育非旋转地堑、旋转半地堑、滚动半地堑和走滑地堑,沙三-沙二期以滚动半地堑和复式半地堑为主,沙一-东营期主要发育滚动半地堑、复式半地堑和走滑地堑.盆地构造样式的演化遵循着三个序列,即旋转半地堑→滚动半地堑→复式半地堑序列、非旋转地堑→滚动半地堑→复式半地堑序列和非旋转地堑→走滑地堑序列.演化序列本身存在差异并受断裂活动的控制.构造样式的演化具有明显的地区性特点,后两种序列沿郯庐断裂带、沧东-兰聊断裂带和太行山东麓断裂带发生,与三条岩石圈走滑带吻合.第一种序列发生在上述三条走滑带之间,构成两个伸展区.构造样式的演化与烃源岩、油气藏和含油气系统的性质和分布有着密切的关系.     

柴达木盆地西部侏罗系油砂的发现及其意义

最近在柴达木盆地西部阿尔金断裂南侧地面剖面上侏罗统地层中首次发现了厚约90m的油砂及大量裂缝沥青脉。通过对这些油砂和沥青的分析研究发现,它们与柴达木盆地西部第三系原油差别较大,与柴达木盆地东部侏罗系原油较相似但也有一定差异。野外地质调查发现柴达木盆地西北部发育大量侏罗系烃源岩,其生物标志物等特征与这些油砂和沥青相似,综合分析认为这些油砂和沥青脉可能来源于成熟的侏罗系源岩。这些油砂的发现对柴达木盆地西北部及阿尔金断裂沿线盆地的油气勘探具有重要意义。     

珠江口盆地珠一坳陷始新世中-晚期构造变革特征及成因

通过不整合面、断裂体系和盆地构造格局的综合分析,研究珠一坳陷早-中始新世与晚始新世—早渐新世之间的构造变革特征,探讨构造转型机制。印支半岛的旋转挤出及古南海向南俯冲,造成了区域应力场由NW向顺时针转变为近SN向拉张,导致了NE和NEE向断裂控盆向近EW和NWW向断裂控盆转变,且发育大量近EW向新生断裂。岩石圈伸展变形由均一式的宽裂谷模式向集中式的窄裂谷模式转变,且向南海北部大陆边缘迁移,造成了盆地格局由彼此孤立、分割性强的半地堑或窄地堑系趋于相互连通,盆地范围增大。在近SN向拉张作用下,珠一坳陷北缘控盆断裂作为北部的拉伸边界,为先存薄弱带,应力较集中,断裂活动强烈且明显向北扩展,沉降中心整体向北迁移。裂陷期盆地构造变革造成了文昌组与恩平组烃源岩特征的差异,导致了油气资源分布的贫富不均。     

南海西部深水区天然气地质与大气田重大发现

为加快我国深海油气勘探的步伐,"十一五"以来,综合利用大面积三维地震、测井、钻井岩心(屑)和地球化学分析等资料,系统研究了南海西部琼东南盆地深水区的沉积过程、烃源岩形成和生排烃过程,取得了"烃源条件优越""储集条件良好""大型勘探目标成群成带分布"3个创新性认识。研究结果表明:①该深水区位于琼东南盆地的中南部,其形成受印支欧亚板块碰撞与喜马拉雅隆升、南海扩张等多重构造事件控制,经历了古近纪裂陷和新近纪坳陷期;②始新世断裂活动强烈并伴有湖泊沉积,早渐新世裂陷继续发育,沉积环境为海陆过渡相和滨浅海相;③以生油为主的始新统湖相泥岩和以生气为主的下渐新统海陆过渡相煤系地层为两套主力烃源岩;④根据对热演化程度、生烃量及生烃强度指标的分析结果认为,乐东、陵水、宝岛和长昌等4大凹陷属于潜在富生烃凹陷,其中乐东和陵水凹陷的良好生烃潜力已得到钻探证实;⑤深水沉积学和成藏动力学研究成果表明,该区纵向上发育古近系和新近系两大成藏组合,横向上发育中央峡谷岩性圈闭带(群)、长昌环凹圈闭带(群)和宝岛南部断阶带等有利成藏区带;⑥中央峡谷岩性圈闭带成藏条件优越,油气勘探潜力巨大,应作为首选目标实施钻探,南海北部最大天然气田——中央峡谷气田的发现验证了上述观点的正确性。     

珠江口盆地惠州凹陷古近系烃源岩层序地层学和地球化学研究

为了更加准确地预测和评价珠江口盆地惠州凹陷古近系油气资源潜力，精细划分了该凹陷油气汇聚单元和成藏体系，并利用层序地层学和地球化学相结合的方法，分析了该凹陷古近系始新统一下渐新统恩平组和始新统文昌组6个三级层序烃源岩有机质丰度、有机质类型、生烃潜力大小和生物标志物组合特征，指出文昌组SQ2层序地层中一深湖相泥岩是主力烃源岩，恩平组SQ5和SQ6层序地层沼泽相、河流三角洲相和浅湖相煤系烃源岩是重要烃慊岩。