Carbon Storage Dynamics in Lower Shimentan Formation of the Qiantang Sag, East China Sea Shelf Basin: Stratigraphy, Reservoir ‒ Cap Analysis, and Source ‒ Sink Compatibility

Excessive carbon emissions have resulted in the greenhouse effect, causing considerable global climate change. Marine carbon storage has emerged as a crucial approach to addressing climate change. The Qiantang Sag(QTS) in the East China Sea Shelf Basin, characterized by its extensive area, thick sedimentary strata, and optimal depth, presents distinct geological advantages for carbon dioxide(CO_(2)) storage. Focusing on the lower section of the Shimentan Formation in the Upper Cretaceous of the QTS, this study integrates seismic interpretation and drilling data with core and thin-section analysis. We reveal the vertical variation characteristics of the strata by providing a detailed stratigraphic description. We use petrophysical data to reveal the development characteristics of high-quality carbon-storage layers and favorable reservoircaprock combinations, thereby evaluating the geological conditions for CO_(2) storage in various stratigraphic sections. We identify Layer B of the lower Shimentan Formation as the most advantageous stratum for marine CO_(2) storage. Furthermore, we analyze the carbon emission trends in the adjacent Yangtze River Delta region. Considering the characteristics of the source and sink areas, we suggest a strong correlation between the carbon emission sources of the Yangtze River Delta and the CO_(2) storage area of the QTS, making the latter a priority area for conducting experiments on marine CO_(2) storage.

Sedimentary systems of the Oligocene Huagang Formation in the central anticline zone of the Xihu Depression,East China Sea Shelf Basin

The Xihu Depression is the largest hydrocarbon-bearing depression of the East China Sea Shelf Basin(also referred to as the ECSSB).However,the depositional systems and reservoir distribution of the Oligocene Huagang Formation in the Xihu Depression are still controversial.Under the guidance of sedimentology and stratigraphy,this study documented a marine-terrestrial transitional environment in the restricted bay setting of the Oligocene Huagang Formation through core description,well logging,and seismic data analysis.This study also revealed that the Oligocene Huagang Formation is dominated by tidal delta,estuary,and gravity flow deposits in the central anticline zone of the Xihu Depression.The new understanding of the sedimentary systems and the discovery of the transgressive gap in the eastern Diaoyu Islands uplift explain the origin of fine-grained sediments and the EW-trending sand bodies in the central depression and the sand bodies parallel to shoreline in the west slope belt,which cannot be explained by previous study results,such as southern transgression or fluvial deltas and even lacustrine deposition.Moreover,the tidal channels,tidal sand flats,and gravity flow sand bodies formed by the transgressive tides are high-quality reservoirs.The study will provide a basis for well placement and serve as guidance for the selection of favorable hydrocarbon exploration areas in the Xihu Depression.

New interpretation on the provenance changes of the upper Pinghu–lower Huagang Formation within Xihu Depression,East China Sea Shelf Basin

Both Pinghu and Huagang formations are important hydrocarbon reservoirs of the Xihu Depression in the East China Sea Shelf Basin.Clarifying the source suppliers and restoring source-to-sink transport routes are of great significance to the future petroleum and gas undertakings.Previous researchers were largely confined by either limitation of geological records,highly dependence on a singular method or low-precision dating techniques.Our study integrated heavy mineral assemblages,geochemical analyses and detrital zircon U-Pb dating to reconstruct multiple source-to-sink pathways,and to provide a better understanding on the provenance evolution for the upper Pinghu–lower Huagang depositions of the Xihu Depression.At least three major provenances have been confirmed and systematically investigated for their separate compositional features.The Hupijiao Uplift(or even farther northern area)was dominated by a major Paleoproterozoic population peaked at ca.1830 Ma along with minor Mesozoic clusters.The Haijiao Uplift to the west and the Yushan Low Uplift to the southwest,on the other hand,generate opposite U-Pb age spectra with apparently larger peaks of Indosinian and Yanshanian-aged zircons.To be noted,both Indosinian and Paleoproterozoic peaks are almost identical in proportion for the Haijiao Uplift.The overall sedimentary pattern of late Eocene-early Oligocene was featured by both spatial and temporal distinction.The Hupijiao Uplift was likely to cast limited impact during the late Eocene,whereas the broad southern Xihu Depression was transported by a large abundance of materials from the nearby Haijiao and Yushan Low Uplifts.The northern source substantially extended its influence to the farther south during the early Oligocene by delivering plentiful sediments of higher-degree metamorphic parent rocks.Combined with the proximal western and southwestern suppliers,the overall Xihu Depression was under control from both distant and local provenances.

Application of seismic sedimentology in characterization of fluvial-deltaic reservoirs in Xihu sag, East China Sea shelf basin

The fluvial-deltaic reservoirs of the Oligocene Huagang Formation in the Xihu sag of the East China Sea shelf basin reflect rapid lateral change in sedimentary facies and poor morphology of conventional slice attributes,which bring difficulties to the reservoir prediction for subsequent exploration and development of lithologic reservoirs.The traditional seismic sedimentology technology is optimized by applying the characteristic technologies such as frequency-boosting interpretation,inversion-conventional–90°phase shift joint construction of seismic lithologic bodies,nonlinear slices,paleogeomorphology restoration,and multi-attribute fusion,to obtain typical slice attributes,which are conducive to geological form description and sedimentary interpretation.The Huagang Formation developed three types of sedimentary bodies:braided river,meandering river and shallow water delta,and the vertical sedimentary evolution was controlled by the mid-term base-level cycle and paleogeomorphology.In the early–middle stage of the mid-term base-level ascending cycle,braided channel deposits were dominant,and vertical superimposed sand bodies were developed.In the late stage of the ascending half-cycle and the early stage of the descending half-cycle,meandering river deposits were dominant,and isolated sand bodies were developed.In the middle–late stage of the descending half-cycle,shallow-water delta deposits were dominant,and migratory medium–thick sand bodies were developed.Restricted paleogeomorphology controlled the sand body distribution,while non-restricted paleogeomorphology had little effect on the sand body distribution.Based on reservoir characterization,the fault sealing type and reservoir updip pinch-out type structural lithological traps are proposed as the main directions for future exploration and development in the Xihu sag.

Origin of hydrocarbon fluids and discussion of abnormal carbon isotopic compositions in the Lishui-Jiaojiang Sag,East China Sea Shelf Basin

The hydrocarbon gases in the L1 gas field of the Lishui-Jiaojiang Sag have been commonly interpreted to be an accumulation of pure sapropelic-type thermogenic gas.In this study,chemical components,stable isotopic compositions,and light hydrocarbons were utilized to shed light on the origins of the hydrocarbon fluids in the L1gas pool.The hydrocarbon fluids in the L1 gas pool are proposed to be a mixture of three unique components:mid-maturity oil from the middle Paleocene coastal marine Lingfeng source rock,oil-associated(late oil window)gas generated from the lower Paleocene lacustrine Yueguifeng source rock,and primary microbial gas from the paralic deposits of the upper Paleocene Mingyuefeng source rock.Here,for the first time,the hydrocarbon gases in the L1 gas pool are diagnosed as mixed oil-associated sapropelic-type gas and microbial gas via four pieces of principal evidence:(1)The abnormal carbon isotopic distributions of all methane homologues from C_(1)(CH_(4)or methane)to C_(5)(C_(5)H_(12)or pentane)shown in the Chung plot;(2)the diagnostic~(13)C-depleted C_(1)compared with the thermogenic sapropelic-type gas model,whileδ^(13)C_(2)(C_(2)H_(6)or ethane)andδ^(13)C_(3)(C_(3)H_(8)or propane)both fit perfectly;(3)the excellent agreement of the calculated carbon isotopic compositions of the pure thermogenic gas with the results of the thermal simulated gas from the type-II1 kerogen-rich Yueguifeng source rock;and(4)the oil-associated gas inferred from various binary genetic diagrams with an abnormally elevated gas oil ratio.Overall,the natural gases of the L1 gas pool were quantified in this study to comprise approximately 13%microbial gas,nearly 48%oil-associated sapropelic-type gas,and 39%of nonhydrocarbon gas.The microbial gas is interpreted to have been codeposited and entrained in the humic-kerogen-rich Mingyuefeng Formation under favorable lowtemperature conditions during the late Paleocene-middle Eocene.The microbial gas subsequently leaked into the structurally and stratigraphically complex L1 trap with oil-associated sapropelic-type gas from the Yueguifeng source rock during the late Eocene-Oligocene uplifting event.A small amount of humic-kerogen-generated oil in the L1 gas pool is most likely to be derived from the underlying Lingfeng source rock.The detailed geological and geochemical considerations of source rocks are discussed to explain the accumulation history of hydrocarbon fluids in the L1 gas pool.This paper,therefore,represents an effort to increase the awareness of the pitfalls of various genetic diagrams,and an integrated geochemical and geological approach is required for hydrocarbonsource correlation.

Diagenesis and Diagenetic Evolution of Deltaic and Neritic Gas-Bearing Sandstones in the Lower Mingyuefeng Formation of Paleogene, Lishui Sag, East China Sea Shelf Basin: Implications for Depositional Environments and Sequence Stratigraphy Controls

Gas-bearing deposits in the Lower Mingyuefeng Formation of Paleogene, Lishui Sag, East China Sea Shelf Basin consist of shoreface sandstones of the highstand systems tract（HST） and transgressive systems tract（TST）, and deltaic sandstones of the lowstand systems tract（LST） and falling stage systems tract（FSST）.Detailed petrographic observations suggest that the diagenetic features and related evolution of these deposits cannot be simply characterized and demonstrated in the depth domain.However, the occurrence of diagenetic minerals systematically depends on the studied interval within the HST, TST, LST, and FSST; therefore, diagenesis in this region can be better constrained when studied in the context of the depositional environments and sequence stratigraphic framework.The eogenetic processes in such settings include：（1） microcrystalline siderite precipitated as concretions in almost all environments and systems tracts, which inhibited further mechanical compaction;（2） grain dissolution and kaolinitization occurred in shoreface HST sandstones and deltaic LST and FSST sandstones;（3） glaucony was locally observed, which did not clearly reflect the controls of facies or sequence stratigraphy; and（4） cementation by pyrite aggregates occurred in the shoreface HST sandstones and deltaic LST sandstones.The mesogenetic diagenesis includes：（1） partial conversion of kaolinite into dickite in deltaic LST sandstones, and minor chlorite cementation in deltaic FSST sandstones;（2） transformation of kaolinite into illite and quartz cementation in deltaic LST and FSST sandstones;（3） frequent precipitation of ankerite and ferroan calcite in shoreface TST sandstones and early HST sandstones, forming baffles and barriers for fluid flow, with common calcite in shoreface HST sandstones as a late diagenetic cement; and（4） formation of dawsonite in the deltaic LST and FSST sandstones, which is interpreted to be a product of the invasion of a CO2-rich fluid, and acts as a good indicator of CO2-bearing reservoirs.This study has thus constructed a reliable conceptual model to describe the spatial and temporal distribution of diagenetic alterations.The results may provide an entirely new conceptual framework and methodology for successful gas exploration in the continental margins of offshore China, thus allowing us to predict and unravel the distribution and quality evolution of clastic reservoirs at a more detailed and reliable scale.

The Mesozoic Basin-Mountain Coupling Process of the Southern East China Sea Shelf Basin and its Adjacent Land Area

Basin-mountain coupling is a key issue for basin formation and evolution. The analysis of basin-mountain coupling process, as well as quantitative or semiquantitative restoration of prototype basin and the evolution of continental margin, can be used to interpret the geological process of basin-range conversion and reconstruct early prototype basins, which is a difficult and leadin~ scientific oroblem of basin research.

Depositional Responding to Tectonic Evolution of East China Sea Shelf Basin

? The East China Sea Shelf basin is a large marginal rift basin occurred in backarc area of west Pacific. Three main regional unconformities and eleven sequence boundary isochronous surfaces (hiatuses) were developed within the basin filling, which are separared the fill succession into three tectonic sequences and fourteen sequences. The depositional response of every tectonic sequence indicates the different phases in the evolution of basin and a specific filling process or filling pattern.

Tectonics and Petroleum Potential of the East China Sea Shelf Rift Basin

There are two Cenozoic sedimentary basins in the East China Sea. They are the East China Sea shelf basin and the Okinawa Trough basin. The former can be divided into a western and an eastern rift region. The development of the shelf basin underwent continental-margin fault depression, post-rift and then tectonic inversion stages. Available exploration results show that the distribution of source rocks is controlled by the basin architecture and its tectonic evolution. In the Xihu depression, mudstones and coals are the main source rocks. The eastern rift region has good geological conditions for the formation of large oil and gas fields.

Tertiary Sea Level Changes and Sequence Stratigraphic Framework in East China Sea Shelf Basin

The East China Sea shelf basin is a key area for setting up the sea level changes of Cenozoic in the West Pacific. Based upon the characteristics of seismic reflection, the analysis of sequence stratigraphy and depositional system, the high resolution chronostratigraphic framework has been set up by using the data of micropaleontologic biozone fossils. The relative sea level change curve has been set up by combining analysis of paleoecology, genetic facies, specific sedimentary structures and on lap recognized from the seismic profiles with study of geochemical characteristics. There are 4 2nd order basin cycles showing the long term sea level changes, and 22 3rd order cycles showing short term ones with relative changing ranges of 0-150 m. Transgression and regression showing long term sea level changes bear asymmetric feature, which indicates that the speed of transgression is faster than that of regression. There are a lot of differences when compared with Haq ’s curve. The sequence stratigraphic framework has also been set up and 3 tectonic sequences, 7 supersequences and 19 sequences have been subdivided for Tertiary in the East China Sea shelf basin. On the basis of detailed analysis of genetic facies and log facies, 9 sedimentary systems, 20 depositional assemblages and many genetic facies have also been recognized and investigated. Based on the studies mentioned above, the favorable source and reservoir facies of gas and petroleum are indicated.

西湖凹陷花港组浅水三角洲平原分流河道沉积构型

渐新统花港组上段是东海陆架盆地西湖凹陷中南部地区的主要产油气层位,但对其沉积体系的认识一直存在争议,砂体构型特征及控制因素的研究也相对匮乏。综合运用岩心、测井及地震等资料,研究渐新统花港组上段沉积环境、沉积微相类型、砂体沉积构型特征及其控制因素。结果表明:西湖凹陷中南部花港组上段以浅水三角洲平原沉积为主,分流河道是最主要的砂体类型。根据弯曲度差异,可将分流河道划分为辫流型(弯曲度1~1.05)、曲流型(弯曲度大于1.15)和辫-曲转换型(弯曲度1.05~1.15)3种类型,其中辫流型分流河道砂体“宽而厚”,平面组合呈交织宽条带状,心滩呈斑点状排列,砂体垂向叠置样式以切叠型为主;曲流型分流河道砂体“窄而薄”,平面样式为单一条带型或分叉-合并型,厚砂以点坝的形式分布在河道边缘,砂体垂向叠置样式以“孤立型”为主;辫-曲转换型分流河道是辫流型和曲流型的过渡类型,河道砂体规模中等,河道内心滩和点坝同时发育。3类分流河道的厚度与宽度呈对数正相关,宽厚比具有辫流型>辫-曲转换型>曲流型的特征。推测古地貌和基准面变化是影响浅水三角洲分流河道构型特征的主要因素,其中古地貌控制了分流河道的河型变化,较陡的地形有利于低弯度辫流型分流河道的形成,而长期基准面上升造成了分流河道规模逐渐下降,中期基准面的上升造成了分流河道砂体叠置样式发生切叠型→叠加型→孤立型的演变。研究成果完善了浅水三角洲的沉积构型知识库,对地下浅水三角洲分流河道储集层的预测及开发具有重要的指导意义。

西湖凹陷木广迎地区断陷层地质结构与油气勘探意义

西湖凹陷是东海陆架盆地内规模最大的富油气凹陷,保俶斜坡带是凹陷内油气勘探的主要地区。近期勘探实践表明,斜坡带深层构造—岩性领域具有良好的勘探前景。开展斜坡带北部木广迎地区深部断陷层地质结构与油气勘探潜力分析,对于明确西湖凹陷构造—岩性领域下步有利突破方向具有重要意义。本文综合利用高精度三维地震和钻井资料,开展木广迎地区精细的构造和层位解释。根据解释结果进行埋藏史—热演化史模拟,并系统分析区内油气地质条件。研究表明,木广迎构造带整体表现为东倾斜坡,北部发育古新统厚度中心;区内发育走向为NE、NNE和NW向的3组断裂,多数断裂的主活动时期为古新世—始新世,活动强度逐渐减弱;木广迎地区现今古新统残留厚度为200~1500 m,暗色泥岩厚度为100~700 m,最厚可达700 m以上,其主体于宝石组沉积时期进入成熟阶段;宝石组内发育大套厚层砂岩,且物性较好,可作为有利储层。研究认为,木广迎地区发育良好的生—储—盖组合和有效的源—储配置,是西湖凹陷斜坡带构造—岩性领域勘探的有利方向。

西湖凹陷龙井运动构造递进变形特征与机制

龙井运动是东海陆架盆地西湖凹陷新近纪以来的关键构造运动,但对龙井运动幕次及起止时间认识不清。依托三维地震资料,运用生长地层法、平衡剖面等技术,细致刻画了龙井运动的幕次和各幕次的起止时间,总结了构造递进变形特征,结合物理模拟实验,探讨变形机制。研究表明:①龙井运动可划分为早、中和晚3个幕次,其中龙井运动早幕是构造运动主幕,持续时间长(T_(15)—T_(11)),龙井运动中幕和晚幕持续时间短(T_(10)、T_(5));②西湖凹陷龙井运动东西方向上存在构造递进变形特征,东部早反转晚结束,持续时间长,变形强度大;西部晚反转早结束,持续时间短,变形强度弱;③西湖凹陷构造递进变形特征受控于东侧挤压作用向西传递过程中的衰减作用。本次研究成果对于西湖凹陷油气成藏期厘定、埋藏史恢复等均具有重要参考价值。

东海陆架盆地丽水-椒江凹陷构造演化特征及其与油气成藏的关系

东海陆架盆地丽水-椒江凹陷经历了复杂的构造运动过程,目前已发现多个含油气构造,但仍未取得大规模商业油气发现,油气勘探未能突破的主要原因在于对其构造演化特征认识不清。基于最新采集的三维地震和钻井资料,通过断裂特征的精细刻画、平衡剖面恢复、已钻井地球化学特征分析等方法,对丽水-椒江凹陷的构造演化特征及其与油气成藏的关系进行了深入分析。结果表明:丽水-椒江凹陷主要发育3套断裂系统,包括深部断裂系统、浅部断裂系统和贯穿断裂系统,控制了凹陷整体东断西超,内部南北分区东西分带的构造格局;凹陷演化共经历4个阶段,包括晚白垩世—古新世断陷期、始新世初期坳陷期、始新世末期—渐新世抬升剥蚀期以及新近纪—第四纪沉降期,不同断裂系统形成于不同演化阶段,并对凹陷结构具有差异控制作用;断陷期发育的灵峰组厚层泥岩阻挡了油气的垂向运移,且深部断裂与浅部断裂在纵向上各自独立,互不连通,油气垂向运移不畅,限制了油气在烃源岩及邻近层位成藏,确定了丽水-椒江凹陷“近源下洼”的油气勘探方向。研究成果可为丽水-椒江凹陷的油气勘探提供基础理论支撑。

东海陆架盆地中部隆起带北西向大断层识别及成因机制

东海陆架盆地不同地区均揭示有局部北西走向断层的存在,但由于对断层缺乏盆地整体研究,导致断层运动学和动力学认识存在争议。以中部隆起带为重点研究区,通过对区域重磁和地震资料的综合分析开展了盆地尺度北西向大断层识别和分布规律研究,探讨了区域北西向大断层构造演化过程及成因机制。结果表明:①中部隆起带发育有10条北西向大断层,该类断层具有分布范围广,断层规模“南大北小”和断面相对低角度的特点,并控制了区域内中生界及古新—中下始新统厚度的南北差异;②北西向大断层形成时间早于北东、北北东向断层,主要经历中生代燕山期正断层发育、中生代末期至早中始新世伸展-转换断层发育、中晚始新世到渐新世断层整体消亡和中—上新世至今断层局部活化四个演化阶段;③北西向大断层的形成与中国东部印支—燕山期先挤压逆冲、后伸展回滑作用有关,反映印支期华南与华北板块南北碰撞向东南方向深入影响至东海陆架盆地区域,形成大量北西走向低角度逆冲断层,燕山期在北西—南东向区域挤压及地壳增厚背景下,存在广泛的北北东—南南西向伸展逃逸,最终控制了北西向低角度正断层的形成。上述研究为区域内深层及基底潜山领域的油气勘探研究提供了支撑。

东海陆架盆地新生界咸水层二氧化碳封存地质条件及封存前景

目前可用于封存二氧化碳的地质体包含深部咸水层、枯竭油气田、玄武岩等,其中,深部咸水层广泛分布于全球大多数沉积盆地,具有封存能力大、技术成熟、安全性高、成本低等优点,是一种重要的二氧化碳封存地质体。相较于陆域,海域碳封存具有封存潜力大、安全性高、环境影响小、封存周期长等优点,是实现“双碳”目标的重要途径。东海陆架盆地面积大,盆地构造稳定性较高,属于次冷-次热盆地,碳封存目标层厚度大、分布广,具有良好的咸水层二氧化碳封存地质条件,且盆地油气勘探开发程度较高,实施二氧化碳咸水层地质封存的工程条件成熟。在中国海域含油气盆地中,东海陆架盆地咸水层二氧化碳地质封存适宜性为高适宜。综合考虑勘探开发程度、区域构造稳定性、地热条件、二氧化碳咸水层地质封存物质条件和地质封存工程实施条件等可影响二氧化碳地质封存前景评价的参数,分别评价了各区带二氧化碳封存前景。其中,台北坳陷和浙东坳陷碳封存前景最好,适宜实施二氧化碳地质封存;长江坳陷和海礁隆起碳封存前景较好,可作为实施二氧化碳地质封存的备选区带。

东海陆架盆地咸水层CO_(2)封存地质条件适宜性评价

系统分析了东海陆架盆地咸水层CO_(2)封存的关键地质要素,认为在构造和沉积演化的控制下盆地表现出“整体封存有利、东西封存差异”的特征,东部坳陷裂陷充分,构造单元面积大、沉积厚并且地层发育全,潜在封存层系为中新统和渐新统;西部坳陷裂陷早,构造单元面积相对小、地层薄并且地层时代老,CO_(2)封存的有利储盖组合为古新统—始新统。对各二级构造单元咸水层CO_(2)的封存量进行了计算,结果表明,东海陆架盆地D级咸水层CO_(2)封存量为636.2亿t,其中东部坳陷的西湖凹陷和基隆凹陷封存量最大,均超过100亿t,其次为西部坳陷的瓯江凹陷,达到64亿t。结合关键封存要素建立了东海陆架盆地D级CO_(2)地质储存适宜性评价指标体系,并对各评价单元进行了适宜性评价,结果表明西湖凹陷和瓯江凹陷CO_(2)封存适宜性最好,为东海陆架盆地CO_(2)封存的有利远景区。

东海陆架盆地CO_(2)地质封存适宜性评价

温室气体过量排放引起了明显的全球气候变化及诸多次生灾害,CO_(2)捕集与地质封存技术应运而生。中国东海沿岸CO_(2)排放源众多,但陆上盆地面积狭小,无法满足巨量CO_(2)封存的需求。根据相关学者做出的中国全海域级碳封存适宜性评价,东海陆架盆地在中国近海盆地中碳封存适宜性排名第3,面积宽广且封闭性好,因此,在此基础上对东海陆架盆地开展了盆地级碳封存适宜性评价。结合专家意见和相关学者研究成果,利用模糊综合评价法和层级分析法确立了适宜性评价指标体系及指标权重,再根据盆地内各二级构造单元的相关地质资料,按照评价指标分级赋分表对各单元的每个评价指标进行评分,结合权重计算出综合适宜性评分。综合考虑碳封存容量、封闭性及可操作性的评价结果认为,台北坳陷为盆地中碳封存综合适宜性最好的单元,可作为优先实验性封存区。

地震沉积学在东海陆架盆地西湖凹陷河流-三角洲相储集层刻画中的应用

针对东海陆架盆地西湖凹陷渐新统花港组河流-三角洲相储集层横向变化快、常规切片属性形态差、储集层预测难度大、难以满足岩性油气藏的后续勘探开发的问题应用分频解释、反演-常规-90°相移联合构建地震岩性体、非线性切片、古地貌恢复、多属性融合等特色技术对传统地震沉积学方法进行优化。研究发现花港组发育辫状河、曲流河和浅水三角洲3类沉积体,垂向沉积演化受中期基准面旋回和古地貌联合控制。在中期基准面旋回上升阶段的早—中期以辫状河道沉积为主,发育垂向叠置型砂体;在上升半旋回晚期和下降半旋回的早期以曲流河沉积为主,发育孤立型砂体;在中期基准面下降半旋回的中—晚期以浅水三角洲沉积为主,发育迁移型中—厚层砂体。限定性古地貌对砂体展布具有控制作用,非限定性古地貌对砂体展布影响较小。在储集层刻画的基础上,提出断层封堵型和储集层上倾尖灭型构造岩性圈闭是西湖凹陷下一步滚动挖潜的主力方向。

东海陆架盆地西湖凹陷天台斜坡构造变换带发育特征及形成机理

东海陆架盆地西湖凹陷天台斜坡构造位置特殊,深层NW向断裂带从斜坡区通过,并对斜坡南、北部新生界的构造特征起到了明显的调节和变换作用。通过三维地震资料精细解释和平衡剖面复原,建立了天台斜坡深层NW向断裂和浅层断裂的发育模式,厘定了NW向变换带的构造属性,同时结合区域地质背景,探讨了构造变换带的演化过程和形成机理。结果表明:天台斜坡中生界发育包括天台西断裂和孤山断裂在内的NW向伸展滑脱断层,并对斜坡南、北部新生界地质结构、断裂发育和伸展强度等起到了明显的调节和变换作用。天台斜坡北部和南部分别表现为缓坡和陡坡结构特征,北部断裂密集发育,而且孤山断裂上盘发育弧形断裂,北部伸展强度也要明显大于南部。发育于天台西断裂和孤山断裂之间的NW向构造变换带明显不同于伸展背景下的变换构造,属于离散构造变换带。受秦岭-大别造山后碰撞伸展作用与欧亚板块和太平洋板块的碰撞、俯冲过程影响,天台斜坡构造变换带主要经历了晚侏罗世—早白垩世初期变换带孕育期、早白垩世中期—早始新世变换带雏形期、中晚始新世—渐新世早期变换带成熟期和渐新世晚期—现今变换带静止期4个演化阶段。