MESOZOIC-PALAEOGENE BASIN DEVELOPMENT WITHIN THE EASTERN MEDITERRANEAN BORDERLAND

Pre-Alpine structures in the SE Mediterranean (Levant) are characterized by regional extensional features, which are associated with opening of the Mediterranean Sea. Marginal marine basins apparently began forming during the Triassic and Jurassic, and reached their apex during the Cretaceous. Stress patterns attributed to early development of the Mediterranean are similar to those seen in the relatively stable adjacent continental margin. The two major structural-basin trends in the continental margin are orthogonal, e.g. the NW-SE trend of the Sirhan Basin, and the NE-SW trend of the Palmyra Basin. The western convergence of these two basins is marked by basaltic flows and volcanoclastic deposits, probably related to basaltic volcanism in the nearby Mediterranean Sea. These two basins maintained a largely unimpeded circulation of seawater with the opening Mediterranean, and therefore they contain few highly carbonaceous beds. Post-rift shortening apparently produced minor petroleum resources.     

NEW DEVELOPMENTS IN THE PRE-RIFT PROSPECTIVITY OF THE ERITREAN RED SEA

Northern, central and southern Africa is covered by great thicknesses of Upper Palaeozoic and Mesozoic fluvio-deltaic and marine siliciclastics, which include important source rocks, reservoirs and seals. In the Eritrean Red Sea, the importance of these rocks has not yet been properly recognised.
The Red Sea initially formed by rifting of the Afro-Arabian continent in Oligo-Miocene times. Palaeozoic and Mesozoic rocks were downthrown into the resultant Gulf of Suez/ Red Sea Graben and were rapidly buried by syn- and post-rift sediments. In the Eritrean Red Sea area, pre-rift rocks are now only exposed in the Danakil Alps at the Straits of Bab el Mandab, on the Eritrean Plateau, in the coastal lowlands north of Massawa, and in isolated outcrops in Ethiopia.
The authors believe that an as-yet untested pre-rift "play" is to be found in the Eritrean Red Sea contiguous with the Danakil Alps. In addition, syn- and post-rift "plays" cannot be ruled out in this area. The combination of newly-mappedpre-salt structures, containing Jurassic source rocks and Jurassic and Cretaceous reservoir sandstones and carbonates overlain by Tertiary elastics and/or salt, embodies the primary hydrocarbon entrapment model in the area. Secondary hydrocarbon "plays" centre on deformed Miocene siliciclastic seauences in proximity to salt diapirs.     

含油气盆地中膏盐岩层对油气成藏的重要影响

多数盆地的膏盐岩为蒸发成因,部分地区则为深部热卤水作用的产物.研究表明:膏盐岩的形成环境(主要是陆相湖盆蒸发环境)有利于有机质的保存,为油气生成提供物质保障.深部热卤水作用致使深部热流体上侵,将提高烃源岩的油气转化效率以及为无机油气藏的形成提供了条件.膏盐岩能使其下部地层保持较高的孔隙度并且形成次生孔裂隙(但也可堵塞下部地层原生孔隙),同时本身也可成为油气的运移通道或储集空间,是其下部异常高压系统得以形成的重要条件,有利于油气藏的保存.膏盐层可以单独封盖油气,也可与断层联合封堵,具有很好的封盖能力.膏盐层对其上、下地层的区域构造样式产生影响,也限定了油气运移的途径和聚集层位.     

玛湖凹陷风城组碱湖烃源岩发育的构造背景和形成环境

玛湖凹陷是准噶尔盆地重要的生烃凹陷,凹陷中下二叠统风城组的湖相优质烃源岩被认为是中国至今发现的最古老的碱湖沉积,是准噶尔盆地西北缘百里油区形成的重要基础。通过区域构造、沉积学以及岩石矿物学方面的综合研究表明,风城组沉积于西准噶尔地区古生界基底上所发育的二叠纪造山后伸展断陷中,整体上是一套扇三角洲—湖相沉积体系,其中碱湖沉积集中于玛湖凹陷的中心地带。风城组发育大量的特征性碱类矿物,包括硅硼钠石、氯碳酸钠镁石、碳酸钠钙石、水硅硼钠石、碳镁钠石、碳氢钠石和苏打石等,表征了碱湖沉积特点,碱化程度高,区别于常见的盐湖沉积。碳酸钠钙石、碳氢钠石、硅硼钠石和水硅硼钠石等碱类矿物的发育,证实玛湖凹陷风城组碱湖烃源岩形成于受深部热液作用影响的高盐度闭塞性湖泊环境,而不是蒸发成因,这也和伸展断陷背景下活跃的火山活动密切相关。     

PETROLEUM GEOLOGY OF THE WESTERN PART OF THE CENTRAL IRAN BASIN

Eocene extension and magmatism in Central Iran was followed by late Eocene – early Oligocene uplift, erosion, volcanism and the deposition of the continental and evaporitic sediments of the Lower Red Formation. During the late Oligocene – early Miocene, an extensional (or transtensional) phase occurred with the deposition of the limestones and marls of the Qom Formation, followed by the evaporitic deposits or mudstones of the basal part of the Upper Red Formation. Since the late Miocene, compression has resulted in regional shortening and uplift, with the deposition of the thick, clastic-dominated upper part of the Upper Red Formation and the overlying conglomeratic unit. Between 1951 and 2016, a total of 45 exploration, appraisal and development wells were drilled across the western part of the Central Iran Basin where the Alborz, Sarajeh and Aran fields are hydrocarbon discoveries. Traps at these fields are NW-SE oriented detachment folds formed during the late Miocene – Pliocene. Porous and fractured limestones in the Qom e-member are the principal reservoir units, and are capped by evaporites or mudstones in the basal part of the Upper Red Formation. Organic-rich mudstones in the Qom e- and c-members together with shales in the Jurassic Shemshak Formation are potential source rocks. An overview of 80 years of exploration efforts in the western part of the Central Iran Basin suggests that the main reasons for the general lack of success include drilling-associated problems, poor reservoir characteristics, lack of hydrocarbon charge, and underestimating the thickness of the overburden on top of the Qom reservoir.     

南海北部神狐海域浅层深水沉积体对天然气水合物成藏的控制

南海北部神狐海域是我国海域天然气水合物（以下简称水合物）研究的热点区域,但该区域水合物储集体类型及特征尚未得到充分的认识。为此,在对不断积累的资料进行分析总结的基础上,基于高分辨率三维地震资料精细解释、岩心沉积物粒度参数描述和粒度C—M模式分析,系统探讨了该海域含水合物层与上覆不含水合物层沉积物的成因机制,分析了含水合物层沉积物粒度参数与水合物饱和度的关系,并初步揭示了深水沉积与水合物藏分布的耦合关系。研究结果表明：①该区水合物赋存在南海北部陆坡峡谷脊部和下游段—嘴部的细粒浊积体中,含水合物细粒浊积体和上覆不含水合物层的沉积物具有不同的粒度参数特征和显著的沉积成因差异;②与峡谷脊部细粒浊积体相比,峡谷下游段—嘴部的细粒浊积体中可能存在着不同成因类型的沉积物夹层,其沉积过程具有复杂性和多期性;③含水合物层的粒度分选系数与水合物饱和度关联性最大,其次为偏度,粒度参数可能通过影响储层物性进而控制水合物饱和度;④气烟囱、断层等流体运移通道和细粒浊积体共同构成水合物的“运聚体系”。结论认为,细粒浊积体和气烟囱构造的空间匹配是神狐海域水合物不均匀性分布的关键控制因素,“水合物运聚体系”控制水合物成藏的模式将有助于进一步理解深水沉积与水合物成藏的关联性。     

东濮凹陷盐岩形成环境

东濮凹陷随着大量油气资源的发现,对凹陷内巨厚盐层的成因及盐的来源已引起广大地质工作者的极大兴趣和关注,笔者仅就凹陷中成盐环境作尝试性的探讨,不妥之处请批评指教。     

THE HYDROCARBON PROSPECTS OF THE RED SEA-GULF OF ADEN: A REVIEW

The area reviewed covers some 825,000sq. kms. Since the early 1960s. 52 exploration wells have been drilled in the Red Sea. leading to four undeveloped (mainly gas-condensate and dry gas) discoveries; twelve exploration wells have been drilled in the Gulf of Aden since the late 1970s, leading to one undeveloped oil discovery. Numerous surface oil seeps in the Red Sea testify to oil generation, while many of the drilled wells have also had shows. The syn-and post-rift Neogene stratigraphy of the Red Sea is very similar to that of the prolific oil-producing Gulf of Suez graben, with source, reservoir and seal rocks widely present; pre Neogene rocks. however, are only present in patches. and include some marine Paleogene and Late Cretaceous sediments on older continental clastics in the northern half, and marine Jurassic on Basement in the southernmost sector. In the Gulf of Aden, the Neogene is less thickly developed, and lacks the widely-occurring evaporite sequence of the Red Sea; the marine Paleogene and Creataceous-Jurassic sequences of the pre-rift succession are, however, welldeveloped, although the Jurassic is locally removed by block erosion. The tectonic evolution of the two rift basins is here discussed, and evidence for the areal extent of oceanic floor or stretched coninental crust. for episodic or continuous extension and sea-floor spreading, and for pre-rift doming and fracturing, is reviewed. It is concluded that episodic extension and spreading have occurred, and may be more advanced in the Gulf of Aden than elsewhere; this has been accompanied by higher paleo-temperatures and geothermal gradients along the margins in the past, and high present-day heat-flow in the axial regions of both rifts. Overmaturation of the pre-rift sequence in the southern margins of the Red Sea has resulted, aided by deeper burial, but contrary to prevalent views that the regions is too hot and gas-prone, black-oil potential in both basins is present at depths ranging from 1,000 m to a maximum of 4,500 m. Hydrocarbon play in the Red Sea is principally Neogene, and traps are provided by rotated Basement fault-blocks and horsts in the pre-evaporite sequence, and by salt flowage and piercement, together with stratigraphic pinch-out, in the post-evaporite sequence. In the Gulf of Aden, the main play is in the pre-rift Paleogene sequence, while lower potential also exists in Neogene and Mesozoic successions. The Arabian side of the Red Sea has the widest and most poorly-explored shelf of the whole region.     

THE SUDANESE RED SEA: 1. NEW DEVELOPMENTS IN STRATIGRAPHY AND PETROLEUM-GEOLOGICAL EVOLUTION.

The development of the Red Sea-Gulf of Suez Rift follows two tectonic phases: pre-rift and syn-rift: rifting of the Afro-Arabian craton was initiated in Eo-Oligocene times. Generally good reservoir-quality fluvio-deltaic and marginal-to fully-marine Palaeozoic, Mesozoic and lowermost Cenozoic (Palaeogene) rocks had been deposited and are partly preserved.
Marine Upper Cretaceous shales, carbonates and sandstones in the Gulf of Suez change facies to more continental sandstones of the Sudanese Red Sea; similarly, Post-Cretaceous pre-rift limestones and shales change facies to shallow-marine sandstones. Syn-rift sedimentation on either side of the Red Sea axial trough is essentially identical to that of the Gulf of Suez. As a consequence of this, the Gulf of Suez ingredients of mature oil-prone source rocks, reservoirs and seals are present in the Sudanese Red Sea. Heat flows are higher in the Red Sea than in the Gulf.
During the early pliocene there was a further episode of doming, further Red Sea extension took place, and the Red Sea attained its current shape.
Remapping of 5,000 kms of 1970's-vintage seismic data in the Sudanese Red Sea has resulted in recognition of many new prospects, which include: post-salt prospects, similar in structural style to the structures tested by the successful Sudanese Red Sea Suakin-1 and Bashayer-1A gascondensate and dry gas discoveries; base-evaporite prospects of a structural style virtually untested in the Sudanese Red Sea, but known to be prospective in the Gulf of Suez; and preevaporite prospects with structural styles indentical to those most prospective in the Gulf of Suez.     

塔里木盆地库车坳陷克拉苏构造带古近系膏盐岩盖层演化与圈闭有效性

膏盐岩层是含油气盆地良好的区域盖层,但不是完美的盖层。研究表明,膏盐岩具有"低温脆变、高温塑变"特征,构造挤压背景下膏盐岩盖层的封闭性随埋深而演化,大于3 000~3 200 m的埋藏深度是克拉苏构造带膏盐岩盖层封闭的关键。克拉苏构造带盐下圈闭成藏有效性因盖层封闭性演化不同而异,克拉苏区带盖层封闭的关键时间为库车中晚期,以勘探盖层埋深超过3 200 m的完整背斜圈闭为主;克深区带盖层封闭的关键时间为库车早中期,在断层侧向封堵时盐下断块、断背斜等圈闭均可聚集油气。研究成果与勘探现状吻合,并有利于提高勘探成功率。     

东海大陆边缘基底性质与沉积盆地

根据基底性质分析 ,探讨了东海大陆边缘新生代沉积盆地的形成演化与成因机制。重磁异常、岩浆活动、重矿物组合等研究结果表明 ,东海陆架第三纪盆地的基底性质与大陆裂谷盆地的基底性质类似。东海陆架沉积盆地具有断陷盆地的结构特征 ,具多物源供给条件 ,断裂活动控制了盆地的发展演化 ,并且与中国东部地区断陷盆地一样 ,也经历了断陷—断拗—拗陷的演化进程     

西藏羌塘盆地侏罗系膏盐岩与油气成藏

石油地质调查与研究表明，羌塘盆地在中生代前陆盆地形成演化阶段广泛地发育了膏盐岩沉积，其中中侏罗统雀莫错组、布曲组和夏里组膏盐岩最发育。受前陆盆地北部冲断带和前陆隆起的制约，膏盐岩主要沿中央隆起和盆地北部边缘展布。膏盐岩形成于干旱气候条件下的封闭—半封闭泻湖和萨巴哈环境，具有较好的封闭性，为盆地最重要的盖层。同时，膏盐层变形产生了多种类型的盐相关构造圈闭，这些圈闭构造主体形成于侏罗纪末—白垩纪初，与盆地主力烃源岩的生烃高峰在时间上具有一致性，为盆地油气聚集成藏提供了有利场所。     

南海北部白云凹陷21Ma深水重力流沉积体系

深水重力流沉积是南海北部陆坡主要的沉积类型,以高分辨率三维地震、钻测井等资料为基础,通过地震资料解释和地质分析,对南海北部白云凹陷21 Ma所发育的深水沉积体系进行识别、解释和预测。识别出块体搬运沉积体系、水道堤岸复合体以及朵体3类深水重力流沉积单元。块体搬运沉积体系呈杂乱反射特征,底部发育侵蚀擦痕;水道作为重力流的搬运通道,呈弱振幅U或V形特征;重力流溢流形成的堤岸呈强振幅楔形特征;水道与堤岸构成水道堤岸复合体具有典型的海鸥翼状特征;位于水道前端的朵体表现为强振幅平行-亚平行反射,在平面上具有朵状特征。块体搬运沉积体系逐渐向水道、水道堤岸复合体以及朵体演化的过程中伴随着不同流态的深水重力流之间的相互转化。综合地球物理学、沉积学以及海洋地质学等方法,对南海北部陆坡21 Ma开展重力流沉积体系研究,建立深水沉积模式,对研究深水重力流沉积过程具有重要的理论意义。     

RESERVOIR CHARACTERIZATION OF THE PLIOCENE RED SERIES,LAM FIELD AND SURROUNDING AREAS,OFFSHORE WESTERN TURKMENISTAN

The sedimentology, petrography and reservoir potential of Pliocene sandstones within the Upper Red Series in the offshore LAM field, Western Turkmenistan, have been examined. Depositional settings are interpreted within the framework of the Red Series palaeoenvironments across the entire Turkmen sector of the Apsheron-Prebalkhan uplift zone, including its onshore extension to the east. Examination of 81 m of core from three separate intervals suggests that the Red Series in the LAM field is the product of a fluvial-dominated delta system with associated floodplain deposits, periodically flooded by the saline waters of the South Caspian Lake. Relatively thick sandstones, up to around 5 m thick, are interpreted as channel and point-bar deposits of a meandering river system, with thinner and finer-grained sandstones and siltstones inferred to be crevasse-splay and interdistributary floodplain deposits. Floodplain mudstones display signs of desiccation, soil formation, plant rootlets and occasional thin layers of anhydrite. Intervals with marine trace-fossil assemblages record incursions of saline-lake waters. Conglomeratic layers at the base of thicker mudstone intervals may be associated with abrupt transgressions of the lake. The best reservoir qualities are associated with the fluvial channel and point-bar sandstones. Crevasse-splay and other overbank sandstones are of poorer quality, while intercalated floodplain to lacustrine claystone/siltstone units may constitute local seals. Eighteen sandstone plug samples from the cored intervals were examined in thin-section and by XRD and SEM to assess how mineralogy, grain size and diagenesis affect reservoir quality. The samples consist predominantly of lithic arkoses and feldspathic litharenites; higher porosities, and therefore better reservoir potential, are associated with the feldspathic litharenites. Primary controls on porosity include compaction, clay-matrix content and calcite cementation. XRD data reveal the presence of illite, illite-smectite and chlorite. The presence of swelling clays has been the main cause of formation damage in the field. The interpretation of meandering fluvial channels here is thought to represent the first published account of such channels within Pliocene reservoir rocks in the north of the South Caspian Basin. Previous accounts of the Red Series sandstones deposited onshore to the east have indicated deposition within braided channels of the palaeo-Amu Darya river delta plain, and alluvial-fan deposits sourced from uplands to the north. Deposition of the equivalent Productive Series by the palaeo-Volga in the Azerbaijan sector to the west has also been interpreted as having taken place within braided systems, although mixed or suspended-load fluvial channels ascribed to the contemporary Kura delta farther south may have been associated with a meandering system. Two palaeogeographic maps are presented to illustrate depositional environments for the Red Series during relative high- and low-stands of the South Caspian Lake. The maps cover the area where the Productive Series of Azerbaijan passes into the Red Series of Western Turkmenistan.     

Hydrocarbon potentiality, burial history and thermal evolution for some source rocks in October oil field, northern Gulf of Suez, Egypt

This paper attempts to apply a one dimensional model on four source rocks (Belayim, Lower Rudeis, Thebes, and Brown Limestone formations), in East Warda concession, October oil field, throughout the different geological times. Moreover, the fundamental aspects of the petroleum system in the study area is evaluated through studying maturation and hydrocarbon potential in order to gain an understanding of onset of oil generation and expulsion. The position of three wells (syn. or pseudo wells) is proposed based on the available geological and thermal data. Also, the existing temperature database is enhanced by using the available temperature data for 220 wells in the Gulf of Suez and the Red Sea, 53 wells in the Mediterranean Sea, 29 wells in the Nile delta, 7 wells in Sinai, 2 wells in Upper Egypt and 39 wells in the Western desert. Finally, the timing of oil generation for Belayim, Thebes, Lower Rudeis and Brown Limestone source rocks in the Northern Gulf of Suez area is updated. From this study we conclude that, the cumulative yield of the Belayim and Lower Rudeis formations is lower than that of the Thebes and Brown Limestone formations.     

南海东北部陆坡天然气水合物富集特征及成因模式

南海东北部陆坡具有良好的天然气水合物(以下简称水合物)成藏条件,其水合物资源的成因模式明显不同于2007年在神狐海域钻探发现的分散型水合物成矿区。为探讨前者的成藏特征与成因模式,利用钻探区的地震、测井、现场钻探取心及测试分析等资料进行了综合研究,以期加深对南海东北部陆坡水合物富集规律的认识。研究结果表明:(1)在纵向上,该区发育浅、中、深3套水合物层,构成既相对独立又有一定成因联系的成藏系统,区内存在扩散型、渗漏型和复合型3种成因模式的水合物矿藏;(2)扩散型水合物呈层状分布在稳定域底部,其底界与海底反射界面(BSR)分布吻合;(3)渗漏型水合物呈块状、脉状等形式充填在沉积物裂隙或裂缝中,在稳定域不同部位形成多个矿体;(4)复合型水合物矿藏兼具扩散型和渗漏型水合物的成藏特征,在稳定域底部发育扩散型水合物矿层,而在稳定域上部发育渗漏型水合物体,共同构成复式成藏系统。结论认为:南海东北部陆坡是目前中国水合物资源最为丰富、成藏地质条件最为复杂的成矿区之一。     

沉积学进展

近廿多年来,随着人类对油气资源和其它矿产需求的增加和对人类生活环境的保护,以及边缘学科与新技术的兴起,使沉积学的研究领域更为扩大和深入。它已从人类熟知的大陆扩展到两极和荒漠的研究;从陆地和大陆边缘海域扩展到深海的研究;从区域地质调查扩展到全球的研究;从寒武纪以后的地层扩展到前寒武系的研究;从地壳浅部扩展到地球深部地幔地核以至宇宙其它星球的研究等等,这些都标志着地质科学发展的新阶段。     

PETROLEUM EXPLORATION IN THE ETHIOPIAN RED SEA

The Red Sea is a pericratonic Upper Tertiary basin which developed on the continental margin of Africa during the separation of Arabia from Africa, and is characterized by halokinetic tectonics in the upper stuctual stage and block-rifting in the lower strctual stage. The margin is overprinted on a pre-rift Mesozoic platform.
Hydrocarbon exploration interest in the Ethiopian Red Sea area is based on three objectives, which correspond to stages in geotectonic evolution: Mesozic pre-rift targets; Miocene rift presalt targets; and upper Miocene-Pliocene post-rift drift sequences.
Reservoirs with appropriate sealing units (salt or shale) have been recorded. Models of sourcerock maturation using observed geothermal gradients are consistent with anaytical resuits, and prove that oil generation and preservation is to be xpected in the Ethiopian Red Sea.     

THE RED SEA — GULF OF ADEN: BIOSTRATIGRAPHY, LITHOSTRATIGRAPHY AND PALAEOENVIRONMENTS

Sediments of Palaeozoic, Mesozoic and early Palaeogene ages experienced a similar geological history in Ethiopia, Yemen and Somalia. During the late Eocene, however, uplift and differential erosion took place, prior to rift development in the middle Oligocene, when the proto-Gulf of Aden became established. To a certain extent, a similar sequence of events had also taken place in those regions of Egypt, Sudan, Ethiopia, Yemen and Saudi Arabia which border the Red Sea, but post-Eocene subsidence is now believed to have commenced during the late Oligocene in the southern Red Sea and progressed later, during the early Miocene, in the northern Red Sea and Gulf of Suez. Timing of this progressive development of the Gulf of Aden rift complex through the Red Sea and Gulf of Suez is well constrained by biostratigraphy, and provides a new approach to the understanding of lithological variations within the region.
These lithological variations have, until now, only been considered on a country-specific basis, thus hindering establishment of a regional history of sedimentation. The well-understood and well-documented lithostratigraphic nomenclature of the Miocene succession of the Gulf of Suez has been used as a reference, or type, with which the lateral facies variations within the Red Sea have been compared. By this method only has it been possible to produce palaeoenvironmental maps for the entire study region, and for each formation and member. Lateral equivalents of the Gulf of Suez Nukhul, Rudeis, Kareem, Belayim, South Gharib. Zeit, Wardan and Shagara Formations have been identified within the Red Sea syn-rift and post-rift episodes.     

岩盐成因与发育模式——以柴达木盆地英西地区古近系下干柴沟组为例

柴达木盆地英西地区古近系下干柴沟组为寒冷干旱的咸化湖盆沉积,发育多期岩盐(成层石盐),其成因和发育模式是当前待解决的热点问题。岩心资料揭示完整的成盐单期旋回为"蒸发沉积序列",探井岩性序列组合特征表明湖盆经历了半咸化、咸化和盐湖3个演化阶段。通过包裹体岩相学、均一温度测试及成分研究与含盐层系硫、碳、氧同位素分析明确提出岩盐为低温水下浓缩结晶成因。岩盐形成于蒸发作用强烈的陆相闭塞环境,物质来源为陆源地表水携带而来。咸化阶段中后期与广盐湖阶段发育2种成盐模式,每种模式可再分为初始咸化期、咸化期及成盐期3个演化阶段。连井对比分析表明存在5个岩盐集中发育期,盐湖经历了初始、鼎盛与萎缩3个演化过程。盐湖中心岩盐厚度最大,平面分布具局限性,受古地形控制形成多个次级盐洼中心。垂向上多期岩盐的发育缘于陆相湖盆季节性的湖平面频繁升降。