世界主要被动大陆边缘深水含油气盆地生储盖组合发育规律

世界被动陆缘深水含油气盆地的演化可划分为裂前期、裂谷期以及裂后期(被动陆缘期),裂后期又可划分出热沉降期和漂移期两个亚期.裂谷期发育的裂谷层序和漂移期发育的漂移层序是构成生储盖组合的主要层序.统计发现,盆地的生储盖组合主要有裂谷期生储盖、裂谷期生或混生-漂移期储盖和漂移期生储盖三种组合.三种生储盖组合类型均主要发育海陆...     

低勘探程度被动陆缘深水油气聚集研究方法:以赤道大西洋波蒂瓜尔盆地深水油气远景勘探为例

被动陆缘盆地演化通常包括裂谷期、过渡期和漂移期3套巨层序。分离的陆缘具有早期发育相关和后期发育稳定的特征。低勘探程度被动陆缘深水区研究方法包括使用共轭性分析拟定成盆规律特征和深水油气聚集条件、区带类比分析揭示不同级次构造带深水勘探潜力、成藏组合评价确定深水优质储层层系和平面分布位置,进而确定深水远景区圈闭类型及可能的成藏模式。以巴西北东部波蒂瓜尔盆地为例,研究表明:该盆地与西非尼日尔三角洲盆地共轭,其深水油气主要烃源岩是裂谷期湖相泥岩和过渡期浅海泥页岩,储层以漂移期斜坡扇体和浊积水道复合体砂体为主。盖层为层间或区域性海相泥页岩。区带分析显示,盆地南东部海域断阶带下降盘湖相砂岩或漂移期深海浊积岩、北西部漂移期深水扇体、水道复合体和前端朵叶体为主要勘探目标。纵向上最有利深水成藏组合是晚白垩世坎潘阶-中新统阿启坦阶Ubarana组砂岩成藏组合,平面上北西部紧邻烃源岩分布区以及南东部紧邻断阶处的砂体是最有利勘探区域。研究认为,盆地深水远景区以地层或与构造相关的地层圈闭为主,油气藏分布主要受疏导体系和成熟烃源岩分布控制。     

巴西坎普斯盆地油气地质特征

坎普斯盆地为典型的被动大陆边缘拉伸裂谷盆地,由前裂谷期(非海相)、同裂谷期(过渡相)及后裂谷期(海相)三个构造层组成.含盐层序为区域盖层,盐下层序泥页岩和盐上层序坎普斯组泥页岩为局部盖层;主要烃源岩为下白垩统拉高亚费耶组湖相黑色钙质页岩;古近系和新近系浊积砂岩为主力储集体,上白垩统浊积岩也是重要储层,下白垩统尼欧克姆阶...     

南美洲被动大陆边缘盆地的油气地质特征

南美洲被动大陆边缘盆地是目前世界油气勘探最活跃的地区之一。南美洲被动大陆边缘盆地形成于晚侏罗世-早白垩世冈瓦纳大陆的裂解,经历了前裂谷期、同裂谷期、过渡期、后漂移期4个阶段,发育了多套生储盖组合。其中同裂谷期的湖相源岩为最重要的生油岩,过渡期发育的盐岩层对油气的成藏起着关键作用。近年来,发现的大油气田均位于盐下同裂谷期的陆相碎屑岩和湖相碳酸盐岩储层中。南美东部被动大陆边缘盆地可以按油气潜力分为3类,最有潜力区位于巴西东海岸的中南部盆地群。随着油气勘探技术的进步,在本区进行油气藏勘探具有广阔的前景。     

摩洛哥—西撒哈拉被动陆缘盆地石油地质特征及勘探方向

针对摩洛哥—西撒哈拉具有相似构造和沉积特征的被动陆缘盆地,开展盆地演化、石油地质特征与资源潜力等方面的研究,并指出油气勘探方向。摩洛哥—西撒哈拉被动陆缘盆地经历前裂谷期、裂谷期和后裂谷期3期构造演化,发育多套烃源岩和储层、多种圈闭类型。最重要的烃源岩为后裂谷期侏罗系—白垩系海相泥岩,主要储层为侏罗系—白垩系碳酸盐岩和碎屑岩,圈闭类型以盐构造作用机制下形成的构造圈闭和构造-岩性圈闭为主。摩洛哥—西撒哈拉被动陆缘盆地可划分为3个主要成藏组合,侏罗系和白垩系—新近系成藏组合是最重要的成藏组合。侏罗系碳酸盐岩和白垩系阿尔布阶—塞诺曼阶浊积砂岩是研究区当前的重点勘探领域;深水区白垩系盐构造和斜坡扇形成的地层-岩性圈闭可能为未来的勘探潜力区。     

西非海岸盆地群形成演化及深水油气田发育特征

西非海岸盆地群的形成演化受非洲板块构造演化和大西洋张裂的控制,总体上可以分为前裂谷阶段、裂谷阶段和后裂谷阶段。沿岸15个主要盆地从北往南可细分为5段,分别为北段盐盆、中段盆地、尼日尔三角洲、中南段盐盆、南段盆地。深水油气田主要发育于后裂谷阶段的上白垩统和第三系海退层序中,以油田为主。在尼日尔三角洲和中南段盐盆的下刚果盆地,所发现的油气田个数及可采储量均比较集中,个数占西非深水油气田总个数比例分别为55%和29%,占总可采储量的比例分别为48%和41%。烃源岩主要有裂谷阶段下白垩统的湖相烃源岩,后裂谷阶段上白垩统、第三系的海相烃源岩。绝大多数储层为浊积岩储层,类型以深水水道砂岩为主,其次为席状砂储层和砂质碎屑流储层。圈闭类型主要为构造-地层复合圈闭,其次为构造圈闭,另外还有地层-岩性圈闭,其所占比例较小。盐构造和泥岩塑性变形构造总体上控制了西非深水区大多数复合圈闭和构造圈闭的形成。     

西非下刚果盆地、加蓬盆地裂陷期构造特征对比研究

为研究下刚果盆地和加蓬盆地盐下构造特征的差异性,指导其盐下勘探,通过不同构造位置的地震、地质剖面分析,对比两盆地裂陷期构造特征的异同。研究结果表明两者均经历了裂谷期、过渡期和漂移期三大构造演化阶段。在裂陷期,两者构造格局相同,但构造规模和隆坳格局有一定的差异性。下刚果盆地内裂谷盆地隆坳特征更为明显,加蓬盆地外裂谷盆地隆坳格局更加清楚。裂陷期的有利勘探区带,下刚果盆地主要集中在内裂谷盆地,加蓬盆地则主要集中在外裂谷盆地。裂谷作用的起始时间、转换断层和基底性质差异可能是造成两者异同的主要原因。     

红海盆地石油地质特征及其油气勘探潜力

红海盆地是Afar三联点裂谷的一支,属于陆内原洋裂谷盆地,另两支分别是亚丁湾裂谷和埃塞俄比亚的东非大裂谷。通过对红海盆地不同国家地层的对比,建立了红海盆地统一的地层格架。在中新世中期,红海盆地处于封闭洋盆环境,沉积了一套区域性盐层,主要发育盐下和盐上两套成藏组合。红海盆地南北成藏存在明显差异,北部与苏伊士湾类似,主要是盐下的基底断块、地垒和旋转掀斜断块等构造圈闭,同时半地堑边界断层控制的点源砂体是重要的勘探目标。而南部热流较高,有利目标集中在盐上,主要包括盐底辟构造、盐流动以及沿断层重力滑动在盐上地层形成的构造圈闭及地层尖灭圈闭。     

西非被动大陆边缘盆地群大油气田形成条件与成藏模式

以板块学说为理论基础,利用IHS能源信息库及新项目评价资料,从西非被动大陆边缘盆地群原型盆地入手,系统剖析了该区大油气田的形成条件与主控因素,建立了大油气田3类成藏模式。研究认为,西非经历了早白垩世贝利亚斯期至巴雷姆期陆内裂谷、阿普特期陆间裂谷、阿尔必期以来的被动大陆边缘3个原型阶段,分别充填了陆相、过渡期泻湖相及漂移期海相沉积体系。陆内裂谷湖相及漂移海相沉积形成了“下湖上海”两套优质烃源岩;过渡早期海侵砂砾岩,漂移期碳酸盐岩、三角洲、深水浊积砂体形成了多套优质储集层;过渡晚期盐岩及漂移期海相页岩分别为盐上及盐下大油气田形成了高效区域封堵。以此为依据,分别建立了南段“盐岩不发育裂谷型”、中段“盐岩发育双层型”及北段“高建设性三角洲型”3类大油气田成藏模式。该研究不但深化了被动大陆边缘盆地油气富集规律,而且能为我国石油公司在该类盆地新项目评价中提供充分的地质依据。     

下刚果-刚果扇盆地沉积-构造演化与油气勘探领域

摘要：下刚果-刚果扇盆地位于西非海岸,因其富含油气,资源潜力大,长期以来一直引起众多研究者的关注。由于该区盐构造发育,变形复杂,盆地不同地区和不同勘探目的层勘探程度并不均衡,如何全面认识和评价盆地油气资源潜力成为指导下步勘探工作的关键。通过盆地沉积-构造演化特征研究,指出下刚果-刚果扇盆地是由下刚果盆地与刚果扇盆地垂向上叠置、平面上复合所形成的叠合复合型含油气盆地,经历了前裂谷期、陆内裂谷期、陆间裂谷期和被动陆缘期等演化阶段;在构造特征分析基础上,综合考虑油气成藏要素和运聚方式等特点,划分出新生界构造-岩性圈闭、盐上白垩系构造圈闭和盐下白垩系等三个油气勘探领域;通过各勘探领域油气成藏特征等的系统分析,指出了盆地东部陆上-浅水地区是勘探盐上白垩系构造圈闭勘探领域和盐下白垩系勘探领域的有利地区,盆地西部深水-超深水地区是勘探新生界构造-岩性圈闭勘探领域的有利地区。     

The Upper Aptian to Lower Albian syn-rift carbonate succession of the southern Maestrat Basin (Spain): Facies architecture and fault-controlled stratabound dolostones

Syn-rift shallow-marine carbonates of Late Aptian to Early Albian age in the southern Maestrat Basin (E Spain) register the thickest Aptian sedimentary record of the basin, and one of the most complete carbonate successions of this age reported in the northern Tethyan margin. The host limestones (Benassal Formation) are partially replaced by dolostones providing a new case study of fault-controlled hydrothermal dolomitization. The syn-rift sediments filled a graben controlled by normal basement faults. The Benassal Fm was deposited in a carbonate ramp with scarce siliciclastic input. The lithofacies are mainly characterized by the presence of orbitolinid foraminifera, corals and rudist bivalves fauna. The succession is stacked in three transgressive–regressive sequences (T–R) bounded by surfaces with sequence stratigraphic significance. The third sequence, which is reported for the first time in the basin, is formed by fully marine lithofacies of Albian age and represents the marine equivalent to the continental deposits of the Escucha Fm in the rest of the basin.The dolomitization of the host rock is spatially associated with the basement faults, and thus is fault-controlled. The dolostone forms seismic-scale stratabound tabular geobodies that extend several kilometres away from the fault zones, mostly in the hanging wall blocks, and host Mississippi Valley Type (MVT) deposits. The dolostones preferentially replaced middle to inner ramp grain-dominated facies from the third T–R sequences consisting of bioclastic packestones and peloidal grainstones. Field and petrology data indicate that the replacement took place after early calcite cementation and compaction, most likely during the Late Cretaceous post-rift stage of the basin. The dolostone registers the typical hydrothermal paragenesis constituted by the host limestone replacement, dolomite cementation and sulfide MVT mineralization. The Aptian succession studied provides a stratigraphic framework that can be used for oil exploration in age-equivalent rocks, especially in the València Trough, offshore Spain. Moreover, this new case study constitutes a world class outcrop analogue for similar partially stratabound, dolomitized limestone reservoirs worldwide.     

Soft-sediment deformation structures interpreted as seismites in the uppermost Aptian to lowermost Albian transgressive deposits of the Chihuahua basin (Mexico)

Several levels of soft-sediment deformation structures (s.-s.d.s.) cut by synsedimentary normal faults have been observed in the transition beds between the “Las Vigas” and “La Virgen” formations (Cretaceous) in the northeastern part of the Chihuahua basin in Mexico. These structures consisted of four kinds of motifs (floating breccias, flame-like structures, large pillow structures, and wavy structures). They are restricted to five “stratigraphic” levels (Σ1–Σ5) and surrounded by undeformed beds in fluvio-lacustrine and tidal deposits and can be traced over a distance of several hundred meters. This deformation is interpreted to have resulted from the combined effects of liquidization and shear stress in soft-sediments due to local earthquakes in the area which could have been generated during the rifting stage of the Chihuahua basin. New constraints placed on the age of the “Las Vigas” Formation (bracketed by Late Aptian charophytes at the bottom and colomiellids of late Aptian to earliest Albian age at the top) suggest that this synrift tectonism lasted at least until the end of the Aptian.     

Coastal sediments from the Algarve: low-latitude climate archive for the Aptian-Albian

The Late Aptian to Early Albian transition has previously been identified as a possible example of substantial climate cooling within the mid-Cretaceous greenhouse period. To study the response of continental weathering and terrestrial vegetation to this cooling episode at low- to mid-latitudes, marine nearshore deposits from the Algarve Basin (SW Portugal) have been investigated with a combined approach including palynology, clay mineralogy and bulk-rock geochemistry. In the Lower Aptian part of the succession, quartz-rich sandstone facies is accompanied by high abundances of early diagenetic kaolinite, which is interpreted to reflect episodes of enhanced humidity and high meteoric flow-through. In contrast, the Late Aptian to Early Albian deposits are characterized by high abundances of detrital clay minerals (mica and chlorite) indicating the dominance of physical weathering processes in the source area, most probably related to low precipitation rates in conjunction with tectonically enhanced erosion. Palynological data show a strong dominance of Classopollis pollen associated with low pteridophyte spore abundances, suggesting warm semi-arid to arid palaeoenvironments. Changes in sedimentation patterns from varicoloured lagoonal marls to thick-bedded shallow-water carbonates are neither expressed in the spore-pollen assemblages nor in the distributions of clay minerals which both remain essentially stable throughout the Late Aptian to Early Albian. These relatively stable patterns are in contrast with various lines of evidence, predominantly from high-latitude areas, that suggest a significant cooling during this time interval. Our study demonstrates that terrestrial environments of low- to mid-latitude regions were not significantly affected by the Late Aptian - Early Albian “cold snap”.     

Carbon and oxygen-isotope stratigraphy of the Early Cretaceous carbonate platform of Pădurea Craiului (Apuseni Mountains,Romania): A chemostratigraphic correlation and paleoenvironmental tool

Stable C and O isotope records were obtained from carbonate rocks spanning the Hauterivian to Cenomanian interval collected in several sections from the carbonate platform of Pădurea Craiului (Apuseni Mountains, Romania). In the absence of some key biostratigraphic marker species, stable isotopes were applied as a tool for stratigraphic correlation and dating. The composite δ¹³C and δ¹⁸O curves for the Early Cretaceous shows variable conditions with large positive and negative excursions and provide information on past environmental changes. The Hauterivian and the Barremian limestones (Blid Formation) display lower δ¹³C values (−2.8‰ to +2.9‰) relative to the Aptian–Albian deposits (−2.6‰ to +5.4‰) (Ecleja, Valea Măgurii and Vârciorog Formations). The red detrital formation (Albian–Cenomanian) is characterized by a highly variable distribution of the δ¹³C values (−3.5‰ to +3.9‰). Based on the similarities between the C-isotope curve established in Pădurea Craiului and from other sections in the Tethyan and the Pacific regions, two major oceanic anoxic events characterized by δ¹³C positive excursions were clearly recognized. The first is the OAE1a event (Early Aptian) in the upper part of the Ecleja Formation and the Valea Măgurii Formation. The second is the OAE1b event (Late Aptian–Albian) in the upper part of the Vârciorog Formation and in the Subpiatră Member. The position of the Aptian/Albian boundary is estimated to be at the upper part of the Vârciorog Formation, immediately after the beginning of the δ¹³C positive excursion. The δ¹³C data show major negative excursions during the Barremian (Blid Formation), Early Aptian (Ecleja Formation), and Late Aptian (Vârciorog Formation). The O isotope variation pattern (−10.2‰ to −2.1‰) is consistent with progressively warming temperatures during the Early Barremian followed by a cooling period. A subsequent warming period culminated in the Early Aptian. A significant cooling phase corresponds to the Late Aptian and Early Albian and the climate cooled again during the Late Albian and into the Early Cenomanian stage. The data provide a better understanding of the Early Cretaceous sedimentation cycles in Pădurea Craiului and create a more reliable framework for regional correlations.     

Pulsating subsidence during a rift episode: stratigraphic and tectonic consequences (Aptian–Albian, northern Spain)

Backstripping analysis has been carried out on nine outcrop sections of the Basque-Cantabrian Aptian and Albian of northern Spain which consist of shallow-water marine deposits up to 7000 m thick. It reveals four main pulses of common accelerated subsidence: I (Early Aptian), II (Early Albian), III (lower Late Albian), and IV (uppermost Late Albian) separated by tectonic quiescent intervals. Tectonic subsidence rates of 70 m Myr^–1 for the Aptian and 101 m Myr^–1 for the Albian were recorded (Sopuerta section). The calculated stretching factor referred to a pre-rift continental crust of 35 km is (β_s=1.32) and represents approximately 8.5 km of crustal thinning. Points of change towards lesser subsidence rate in the curves are correlated with major unconformities in the sections, in the Basque-Cantabrian Basin and in Boreal Europe, suggesting geodynamic changes related with the opening of Bay of Biscay. Minor variations of spreading direction and intensity are proposed to explain the subsidence pulses.     

西非被动大陆边缘重力滑脱构造发育演化及成因机制

西非被动大陆边缘盆地在晚侏罗世伴随大西洋的裂开而形成,陆内裂陷构造旋回(晚侏罗世-早白垩世阿普特期(Aptian))主要发育陆内裂陷构造;过渡期构造旋回(阿普特期)沉积了一套潟湖相塑性层(盐岩);被动大陆边缘构造旋回(早白垩世阿尔布期(Albian)至今)共发育了两期重力滑脱构造,早白垩世阿尔布期-渐新世发育一期(早期)重力滑脱构造,中新世至今发育了另一期(晚期)重力滑脱构造。西非被动大陆边缘同一期重力滑脱构造具有从早到晚由陆向海的前展式发育规律,且多期重力滑脱构造具有从早到晚由陆向海迁移的进积叠加规律。西非被动大陆边缘重力滑脱构造发育的主要控制因素是大地构造背景、地层掀斜、滑脱面形态,其中大地构造背景控制重力滑脱构造体系类型,地层掀斜是引起地质体重力滑脱和变形的根本、控制构造变形的强度,滑脱面形态控制着重力滑脱构造类型和发育位置;次要控制因素是差异重力负载和塑性滑脱层等。并在此基础上建立了宽缓型凹面斜坡和窄陡型斜坡滑脱面下的西非被动大陆边缘重力滑脱构造成因发育模式。     

Deep incision in an Aptian carbonate succession indicates major sea‐level fall in the Cretaceous

Long‐term relative sea‐level cycles (0·5 to 6 Myr) have yet to be fully understood for the Cretaceous. During the Aptian, in the northern Maestrat Basin (Eastern Iberian Peninsula), fault‐controlled subsidence created depositional space, but eustasy governed changes in depositional trends. Relative sea‐level history was reconstructed by sequence stratigraphic analysis. Two forced regressive stages of relative sea‐level were recognized within three depositional sequences. The first stage is late Early Aptian age (intra Dufrenoyia furcata Zone) and is characterized by foreshore to upper shoreface sedimentary wedges, which occur detached from a highstand carbonate platform, and were deposited above basin marls. The amplitude of relative sea‐level drop was in the order of tens of metres, with a duration of <1 Myr. The second stage of relative sea‐level fall occurred within the Late Aptian and is recorded by an incised valley that, when restored to its pre‐contractional attitude, was >2 km wide and cut ≥115 m down into the underlying Aptian succession. With the subsequent transgression, the incision was backfilled with peritidal to shallow subtidal deposits. The changes in depositional trends, lithofacies evolution and geometric relation of the stratigraphic units characterized are similar to those observed in coeval rocks within the Maestrat Basin, as well as in other correlative basins elsewhere. The pace and magnitude of the two relative sea‐level drops identified fall within the glacio‐eustatic domain. In the Maestrat Basin, terrestrial palynological studies provide evidence that the late Early and Late Aptian climate was cooler than the earliest part of the Early Aptian and the Albian Stage, which were characterized by warmer environmental conditions. The outcrops documented here are significant because they preserve the results of Aptian long‐term sea‐level trends that are often only recognizable on larger scales (i.e. seismic), such as for the Arabian Plate.     

Le Bassin lusitanien (Portugal) à l'Aptien supérieur–Albien : organisation séquentielle,proposition de corrélations, évolutionThe Lusitanian Basin (Portugal) during the late Aptian–Albian: sequential arrangement,proposal of correlations,evolution

. Three transgressive–regressive 2nd-order cycles were identified in the Upper Aptian–Albian fluvial and marine deposits of the Lusitanian Basin. Its widespread nature, probably including eustatic origin, allows correlation between the southern package, with precise stratigraphic positioning, and the northern series with a poorly constrained age. The main unconformities can be related to the onset of an oceanic crust, in the western margin of Galicia during the Late Aptian, in the bay of Biscay during the Early Albian, and, to the northwest of the Galicia triple point, during the Middle to Late Albian transition, and, at the Albian–Cenomanian boundary, to a probable compressive event with Africa due to the rotation of Iberia. To cite this article: J. Dinis et al., C. R. Geoscience 334 (2002) 757–764.     

Brachiopod events in the European Middle Cretaceous (Aptian-Cenomanian)

Brachiopod events in the European Middle Cretaceous (Aptian-Cenomanian). Brachiopod species proliferated in the Late Aptian and Cenomanian. Significant palaeobiogeographical events took place during the Middle Cretaceous, in particular during Early and Late Albian time.     

Carbonate microfacies and chemostratigraphy of a late Aptian–early Albian marine distal section from the primitive South Atlantic (SE Brazilian continental margin): Record of global ocean-climate changes?

Late Aptian–early Albian limestones from the eastern Brazilian continental margin record the early evolution of the South Atlantic Ocean. In Tethyan and North Atlantic domains, a planktic foraminiferal turnover and organic-rich deposits related to Oceanic Anoxic Event 1b (OAE 1b) point to major ocean-climate changes through this interval. Coeval organic-rich deposits of the South Atlantic Ocean have been interpreted as the product of restricted circulation rather than attributed to a global event. However, previous investigations of the early marine phase of South Atlantic lack data from more distal facies, making correlations to global events difficult. Here, we present C, O, and Sr isotopes, elemental geochemistry, TOC and pyrolysis data, as well as a microfacies analysis of an upper Aptian–lower Albian distal section from the Campos Basin (southeastern Brazil). Our focus is on the paleoenvironmental characterization of and the possible association between organic-rich deposits and major perturbations related to Aptian–Albian transition. Five microfacies associations (MA) were identified in the informal units I and III, which were deposited in the neritic region on a carbonate ramp. Organic-rich deposits were described in unit III, composed of planktic-dominated wackestones interbedded with black shales, in a distal dysoxic to anoxic environment. The carbonates ⁸⁷Sr/⁸⁶Sr ratios showed a drastic increase (0.7072–0.7074), interpreted as enhanced chemical weathering, supported by the increase of continental input to the top of section. This trend was accompanied by a long-term δ¹³C_carb negative excursion, which were assigned to the latest late Aptian–early Albian interval of the isotope reference curves, in accordance with the described occurrence of Colomiella recta. This scenario matches those proposed for the late Aptian–early Albian transition and OAE 1b set, as an enhanced greenhouse stage, pointing to the influence of the referred ocean-climate changes on the deposition of organic-rich deposits of the early South Atlantic Ocean. This investigation gives more evidences that these perturbations were a widespread event, as a product of broad-scale disturbances in the global carbon cycle which also controlled organic deposition and preservation on restricted settings.