Oil／Gas Accumulation Characteristics and Exploration Methods of the Deltaic Lithologic Reservoirs in Northern Shaanxi Area

There are large deltaic systems in the Triassic Yanchang Formation in the northern Shaanxi area of the Ordos Basin, and developed two sets of good source-reservoir-caprock assemblages and many sets of oil-bearing beds. Exploration experience demonstrates that the formation and distribution of the reservoir were controlled by the generative depression of the Yanchang Formation, and deltaic reservoir sand body is the material basis for large-scale oilfields. In addition, secondary laumontite in a low permeable area was dissolved and then a high permeable area was formed. The updip lithologic variety of reservoir sand bodies is favorable to the formation of subtle lithologic traps, and the deltaic reservoirs are characterized by large multi-beds of oil-generation and abundant hydrocarbon resources. In this paper, the petroleum geologic settings of the studied area are analyzed, and the accumulation characteristics and exploration methods of lithologic reservoirs are summarized. It is of theoretical significance for the study of the exploration theories of lithologic reservoirs, and also expedites the exploration steps of deltaic reservoirs in the northern Shaanxi area.

Dramatic changes in the horizontal structure of mangrove forests in the largest delta of the northern Beibu Gulf, China

The horizontal structure of mangrove forests is an important characteristic that reflects a significant signal for coupling between mangroves and external drivers.While the loss and gain of mangroves has received much attention,little information about how the horizontal structure of mangrove forests develops from the seedling stage to maturity has been presented.Here,remote sensing images taken over approximately 15 years,UVA images,nutrient elements,sediments,and Aegiceras corniculatum vegetation parameters of the ecological quadrats along the Nanliu Delta,the largest delta of the northern Beibu Gulf in China,are analyzed to reveal changes in the horizontal structure of mangroves and their associated driving factors.The results show that both discrete structures and agglomerated structures can often be found in A.corniculatum seedlings and saplings.However,the combination of seedlings growing into maturity and new seedlings filling in available gaps causes the discrete structure of A.corniculatum to gradually vanish and the agglomerate structure to become stable.The aggregated structure of seedlings,compared to the discrete structure,can enhance the elevation beneath mangroves by trapping significantly more sediments,providing available spaces and conditions for seedlings to continue growing.Furthermore,by catching fine sediments with enriched nutrients,the survival rate of A.corniculatum seedlings in the agglomerated structure can be much higher than that in the discrete structure.Our results highlight the significance of the agglomeration of A.corniculatum,which can be beneficial to coastal mangrove restoration and management.

三角洲前缘水下分流河道储集层构型及剩余油分布

以吉林扶余油田J19密井网区为例,结合现代浅水三角洲沉积模式,综合应用岩心、测井等资料,对三角洲前缘水下分流河道单砂体内部构型进行了精细解剖。水下分流河道内部构型要素主要可分为前积体和前积层2种,前积层根据被破坏程度的不同又可分为保留型、破坏型和混合型,随湖平面升降及沉积物供给速率与可容纳空间增加速率的比值不同,前积体可分为进积型、退积型和加积型,各自具有不同的成因及沉积演化模式。应用岩电标定、公式拟合、密井网、对子井等资料对前积层和前积体进行了定量识别描述,建立了水下分流河道单砂体内部的三维构型模型。剩余油分析表明:前积层对剩余油的垂向分布有较强的控制作用,而在前积体内部剩余油主要在前积体的上倾方向富集。

三角洲前缘露头储层层次分析——以鄂尔多斯盆地东缘潭家河剖面为例

通过对三角洲前缘露头的精细描述和解剖 ,建立了研究区 1 1种岩石相类型。依据层次分析法原理 ,将三角洲前缘共划分出 5个层次 ,分析了各级界面的岩石类型、分布特征及物性特征。分别探讨了岩石相层次实体的岩石学、结构、构造特征 ,结构要素层次实体的岩石学、岩石相组合及砂体空间形态特征 ,成因单元 (砂体 )层次实体的结构要素组成、岩石相组合特征及各单元的空间分布形态特征。在此基础上 ,运用随机模拟技术对剖面和河口坝砂体进行了层次建模。模拟结果表明 ,利用潭家河剖面建立地质知识库 ,采用随机模拟技术 ,分析沉积环境与潭家河相似的储层骨架模型 ,在井距达到 1 6 0m ,符合率达 80 %以上 。

准噶尔盆地庄1井区下侏罗统三工河组二段砂体成因

准噶尔盆地庄1井区下侏罗统三工河组二段砂体是重要的油气储集体,明确该套砂体的成因,建立该区的沉积相模式,对于该区的进一步勘探有重要指导意义。目前对此套砂体成因的认识不一。通过对庄1井区的岩心、岩相、岩相组合的细致分析,认为J1s21(下侏罗统三工河组二段上亚段)主要为曲流河三角洲前缘沉积,而J1s22(下侏罗统三工河组二段下亚段)主要为辫状河三角洲前缘沉积,且夹有滑塌浊流沉积。

三角洲前缘砂体骨架的随机模拟

鄂尔多斯盆地三叠系延长组长6段、长7段发育于大型正常河流三角洲前缘和湖相沉积环境。在陕西省延长县延河北岸的谭家河剖面,精细观察长6段、长7段出露较好的11条测线(间距为40m),建立原型模型和相应的地质知识库。分别将测线抽稀,间距为80m、120m、160m,用抽稀后的测线作为约束条件,采用顺序指示随机模拟方法,进行三角洲前缘砂体骨架随机模拟,每次抽稀模拟产生50个实现。将模拟实现的概率分布与实际岩性分布对比,结果表明,抽稀后建立的骨架模型是合理的。利用露头的原型模型建立地质知识库,在对井距较大的油藏建模时,利用原型模型给出不易求准的模拟参数,是建立储集层预测模型的有效手段。

海南油田东营三段沉积微相及其与油气的关系

海南油田储层东营组三段为三角洲前缘沉积 ,发育水下分支河道、分流间湾、河口砂坝及席状砂等 4个微相。其中 ,以水下分支河道、河口砂坝的油气储集性能为最好 ,席状砂次之 ,分流间湾较差。本区沉积微相决定了储层的性质与展布 ,进而控制油气的储集和分布。储层评价以下部储集层最好 (以水下分支河道为主 ) ,上部储集层次之 (以河口坝及水下分支河道为主 ) ,中部储集层较差 (以分流间湾、席状砂为主 )

华池油田三角洲前缘砂体展布的三维建模

目的利用三维建模方法预测三角洲前缘砂体有利储层的分布。方法利用序贯指示模拟法(SIS)对华池油田长3层段三角洲前缘水下分流河道及河口坝微相的砂岩岩相及砂体展布进行随机模拟。结果砂岩岩相模拟的三维实现表明,长31、长32、长33小层中以长33小层砂岩最为发育;砂体展布的三维模拟结果表明,长33小层砂体厚度最大,主砂体主要为东北—西南向展布的条带,主砂体向前伸展并演化为三条次级砂带。砂岩岩相与砂体的三维模拟结果在该区勘探实践中得到了较好的验证。结论在主砂体上砂岩厚度大、物性好,常常发育优质储层。

苏北盆地码头庄油田阜一段、阜二段湖泊-三角洲沉积模型

通过分析各种沉积体的岩性、结构、沉积构造、沉积序列和电性特征,划分了苏北盆地码头庄油田阜一段、阜二段沉积相;根据滩和坝在剖面、平面以及岩性上所呈现的特征,划分了滩和坝的类型,建立了各种相的沉积模式,分析了沉积模型的演化历史。据此指出:阜一段发育三角洲前缘亚相沉积,至下而上发育前缘席状砂、河口坝、水下分流河道、水下分流间湾和水下天然堤微相,呈现出三角洲进积的特点,三角洲前缘亚相在阜一段沉积末期消失;阜二段发育滨浅湖亚相沉积,分为生物滩、鲕粒滩、灰质滩、浅湖砂坝和滨浅湖泥微相,有开阔浅湖砂坝和水下隆起区碳酸盐岩滩2种沉积模式。

四川盆地志留系小河坝组海相碎屑岩勘探方向及潜力

四川盆地已在陆相碎屑岩和海相碳酸盐岩获得油气勘探发现,而海相碎屑岩还未获得突破,制约的关键因素是已有钻井未揭示良好的砂岩储层。基于露头、钻井和地震资料,从盆缘到盆内开展系统沉积演化特征的研究,刻画四川盆地志留系下统小河坝组三角洲展布,对比塔里木盆地东和砂岩地震相特征,预测小河坝组砂岩储层发育情况,分析四川盆地志留系小河坝组海相碎屑岩成藏条件和勘探潜力。研究揭示:①四川盆地志留系小河坝组沉积了浪控三角洲,发现了4个具大型前积结构、大型楔状构造的三角洲前缘砂体,面积4 550 km^2,为海相碎屑岩储层有利发育区。②川东地区志留系小河坝组具备有利成藏条件,下伏为龙马溪组优质烃源岩,上覆为韩家店组的广覆式厚层的泥岩盖层,形成良好的生储盖组合。川东地区小河坝组三角洲河口坝砂体与下伏龙马溪组厚层烃源岩发育区叠置,具备形成构造—岩性、岩性气藏条件;③志留系小河坝组海相碎屑岩有望成为四川盆地一个崭新勘探领域,可先寻找前积砂体与逆断层控制的断鼻构造配置的构造岩性圈闭;获得突破后,进一步探索斜坡区的单砂体岩性圈闭。

镰刀湾探区延长组长6油层组沉积体系特征分析

通过对镰刀湾探区近200口井的岩心观察及对镰2井、镰18井、化103井等的重点分析,结合野外露头、测井分析、砂体变化等资料,对镰刀湾探区延长组长6油层组沉积微相进行了研究.镰刀湾探区三叠系延长组长6油层组主要发育三角洲沉积体系,并以三角洲前缘沉积为主,研究区北部发育三角洲平原.研究区以三角洲前缘沉积为主,并进一步细分为水下分流河道、水下天然堤、河口坝及分流间湾等;三角洲平原沉积可细分为分流河道、决口扇、河漫滩等微相.

鄂尔多斯盆地柳沟油区北区长6~1储层岩石特征分析

鄂尔多斯盆地柳沟油区北区长6~1油层是该区的主要产层之一。对该层岩石特征进行分析,该区研究层位属于三角洲前缘沉积环境,岩石类型主要为细粒-极细粒长石砂岩、岩屑长石砂岩,石英含量较低,长石含量高。填隙物主要由绿泥石、方解石、水云母组成,次生胶结矿物绿泥石含量高,平均达4.3%,填隙物含量高是直接影响研究区砂岩储层物性差的关键因素之一。砂岩颗粒磨圆度以次棱角状为主,砂岩的分选性普遍较好,胶结类型主要为薄膜型、薄膜-孔隙型及少量的孔隙型,以细砂岩为主。

The Formation Conditions and Distribution Regularities of Lithologic Reservoirs in the Songliao Basin

The geological background of the fluvial and lacustrine depository system in the large mid-shallow layered depressed lake in the Songliao Basin has been proven to have the geological conditions for the formation of lithologic reservoirs over a large area. Because the rise and fall of the base level caused considerable differences in the space at different periods, the types of sand bodies varied in different geologic periods; but at the same time, because of the differences in burial depths and the relative differences in positions of the siltstones and source rocks, the formation conditions and distributive regularities for oil-bearing groups of subtle reservoirs also vary accordingly. In view of the reality of the thinly-interbedded lithologic reservoir in the deltaic frontal facies belt, we have conducted a series of research to study the thinly-interbedded subtle reservoirs with the help of high resolution sequence stratigraphy, pattern recognition and the geophysical recognition and prediction techniques for thinly-interbedded subtle reservoirs, thus achieving a better effect and optimizing several exploration target areas, each of which has an oil reserve of about 100 million tons. This has shed light on further exploration of new subtle reservoirs.

非线性定量预测技术在渤南洼陷扇三角洲前缘砂体预测中的应用

针对渤南洼陷中深层扇三角洲前缘致密储层地震资料分辨率低、砂泥岩速度差异小、纵向含油层系多层薄、横向储层变化快、储层展布认识不清的难点,在地质沉积模式指导下,运用多体联合解释技术,建立地层等时格架,进行优势属性提取和分析。运用进化型神经网络技术,建立地震属性和砂地比的非线性关系,实现了对薄互层砂体的定量预测,预测结果既保证了与井点的吻合度,也保持了地震资料对沉积特征的反映能力。该方法可以为中深层薄互层储层预测提供借鉴,并指导了该块油藏开发。

The world’s oldest fossil seal record

A femur fragment with an Early Lutetian (early Middle Eocene) age is the world’s oldest fossil record from a seal, and, is described as Praephoca bendullensis nov. gen. nov. spec. This find pushes back the earliest evolution of seals into the Paleocene epoch. The femur has plesiomorphic terrestrial mammal characteristics but has a morphology that is already closer to that of Miocene and present day seals. The Eocene seal femur was found at Fürstenau-Dalum in north-west Germany, in a conglomerate rich in shark teeth that was deposited in a coastal delta environment to the north-west of the central European Rhenish Massif mainland, in the southern pre-North Sea Basin. This discovery has led to a revision of the theory that phocids originated along the coastline of the North American continent. Instead they can now be interpreted to have originated in the tropical Eocene climate of central Europe. Although the fossil records of pinnipeds in Europe during the Eocene, Oligocene and Miocene are extremely sparse, they appear to have inhabited the pre- North Sea basin, within the influence of temperate and arctic upwellings. The distribution of abundant teeth from white and megatooth sharks of two different lineages appears to correlate with that of the seals, which the sharks most probably hunted;providing supporting evidence that the phocids were already adapted as shallow marine coastal inhabitants by this time.

FUNDAMENTAL CHARACTERISTICS OF THE ANASTOMOSING FLUVIAL SYSTEM ON COMPLEX DELTAIC PLAIN

The anastomosing fluvial system was considered as the same term of the braided fluvial system. Smith and others have recognized the difference between them. They described the anastomosing fluvial system as 'a low energy complex of several interconnected channels of variable sinuosity crossing a wetland and forming many elongate vegetated islands', and established a depositional model of anastomosing fluvial system based on their

Testing optically stimulated luminescence dating on sand-sized quartz of deltaic deposits from the Sperchios delta plain, central Greece

This study reports on the first investigation into the potential of luminescence dating to establish a chronological framework for the depositional sequences of the Sperchios delta plain, central Greece. A series of three borehole cores(20 m deep) and two shallow cores(4 m deep), from across the delta plain, were extracted, and samples were collected for luminescence dating. The luminescence ages of sand-sized quartz grains were obtained from small aliquots of quartz, using the Single-Aliquot Regenerative-dose(SAR) protocol.The equivalent dose determination included a series of tests and the selection of the Minimum Age Model(MAM) as the most appropriate statistical model. This made it possible to confirm the applicability of quartz Optically Stimulated Luminescence(OSL) dating to establish absolute chronology for deltaic sediments from the Sperchios delta plain.Testing age results of the five cores showed that the deltaic sediments were deposited during the Holocene.A relatively rapid deposition is implied for the top14 m possibly as a result of the deceleration in the rate of the sea-level rise and the transition to terrestrial conditions, while on the deeper parts, the reduced sedimentation rate may indicate a lagoonal or coastal environment.

Seed germination traits of two plant functional groups in the saline deltaic ecosystems

Aims Salt stress resulting from soil salinization is one of the driving forces of the land degradation throughout the world.The modern Yellow River delta is one of the most saline areas in China.Phytoremediation can be an effective way to restore the salinized ecosystems,which requires selecting appropriate plant species.This study explored the germination responses of common plant species from contrasting habitats in the Yellow River delta to varying salinity,offering experimental information for ecosystem restoration in the Yellow River delta.Methods In this study,15 common plant species from the Yellow River delta were divided into two groups(high-salinity and low-salinity groups)by their natural habitats using Canonical Correlation Analysis.Seeds of each species were treated with five salinity levels(0,5,10,20 and 30 ppt),using a randomized complete block design,and germinated seeds were counted and removed daily for 28 days to calculate the final germination proportion and mean time to germination.The germination responses of seeds to salinity treatments were compared between the two groups.Important Findings In relation to salinity,seed germination behavior of the test species was closely related to the salinity level of the habitats over which they were distributed.Species from the habitats with higher salinity had generally higher final germination proportion but shorter mean time to germination than those from the habitats with lower salinity in all of five salinity treatments used.The final germination proportion and mean time to germination of low-salinity group species were more sensitive to salinity than those of high-salinity group species.Selecting the species with high final germination proportion and short mean time to germination is important for restoration of salinized land.

Oil in Louisiana's estuarine environments: A development model

Coastal erosion, accelerated by sea level rise, and subsidence are major Louisiana issues. With current sea-level-rise projections, coupled with the state’s eroding barrier islands and coastal wetlands, the region’s estuarine environments are in jeopardy of being lost, redefined, or permanently altered. As the coast erodes, Louisiana is endangered of losing valuable wetland’s habitat. In addition, if the barrier islands disappear, the region’s wetland-oriented oil and gas wells and associated infrastructure will be at risk to open Gulf conditions. If this should occur, each well, pipeline, and storage battery represents a potential environmental catastrophe.

Sedimentology and sequence stratigraphy of the Nkporo Group(Campanian-Maastrichtian),Anambra Basin,Nigeria

Integration of sedimentologic and sequence stratigraphic interpretations of the Nkporo Group has provided the basis for a basin-wide framework for prediction of potential source,seal and reservoir rocks in the Anambra Basin,Nigeria.Lithofacies and biostratigraphic data show that the Nkporo Group in the Anambra Basin contains three main facies associations(fluvio deltaic facies,estuarine central basin/shallow shelf facies and estuarine channel fill facies) that determine the reservoir containers,flow units and seals.The units are arranged to form two stratigraphic sequences represented by the Nkporo Shale-Owelli Sandstone and Owelli Sandstone-Enugu Shale successions,respectively.The transgressive systems tract in each sequence comprises coarse grained fluvio deltaic sandstone and an overlying open marine black carbonaceous mud rock.The highstand systems tracts comprise delta front deposits with average porosity,permeability and net-to-gross values estimated in the ranges of 30%,3000 md and 0.9,respectively.The fluvio deltaic and delta front facies which are encased in organically rich estuarine central basin/shallow shelf mud rocks are likely the potential reservoirs.Trapping capacity is enhanced by the presence of several N-S trending normal faults,and other microstructures related to the post-Santonian tensional regime in the Benue.The new information presented in this paper on potential seal,source and reservoir lithofacies within the Nkporo Group should serve as a useful contribution to the geological modelling of reservoirs within the Late Cretaceous-Paleocene succession in the Anambra Basin.