In the preserved successions of clastic lacustrine systems receiving substantial sediment input from fluvial sources, the boundary between delta-plain and delta-front facies belts marks the position of ancient lacustrine shorelines. Placing and predicting the position of this boundary in nearshore lacustrine deposits of the Triassic Yanchang Formation (Ordos Basin, China) is of considerable applied significance, since sandstone deposits of this succession host numerous geological resources, yet delta-top and delta-front deposits differ fundamentally in terms of sandstone fraction, sandbody geometries, and petrophysical properties. However, established sedimentological criteria for shoreline identification relevant to marine environments are only partially applicable to this lacustrine setting. For example, in lacustrine systems, (i) water salinity can be considerably lower, (ii) tidal processes are negligible, (iii) wave activity is often limited and of local significance (e.g., distal and lateral delta-front fringes; transgressive periods of delta-lobe reworking), (iv) seasonal fluctuations in water chemistry and biogenic productivity may be common, and (v) the rate, frequency and magnitude of oscillations in base level differ from marine counterparts. Collectively, these factors hinder the differentiation of delta-plain and delta-front deposits in the Yanchang Formation. Yet the establishment of effective criteria with which to make such distinction is important for palaeogeographic restorations, and for resource exploration and exploitation. On the basis of detailed sedimentological descriptions of well cores and outcrop exposures of the Yanchang Formation in the southeastern Ordos Basin, sedimentary facies accumulated as part of different sub-environments and facies belts are studied. Delta-plain deposits can be readily differentiated from those of delta-front origin on the basis of criteria relating to sediment texture, sedimentary structures, palaeontological content, well-log profiles, and vertical facies successions. These criteria are summarized and applied to better characterize the deltaic setting and to reconstruct the evolution of lacustrine shorelines during accumulation of the Yanchang Formation, particularly for the northeastern area of the basin. A key outcome of this study is the development of a broadly applicable model for the recognition of sub-environments in river-dominated lacustrine deltaic successions. A generalized workflow is established to demonstrate how techniques in sedimentary facies analysis can be employed to reconstruct siliciclastic lacustrine delta shorelines, and thereby predict reservoir characteristics.

以南梁油田白211井区延10段为研究对象,充分利用钻井、岩心、测井等资料,开展地层细分、沉积相类型、砂体展布特征分析.结果表明,延10段地层可细分为延101、延102、延103、延104共4个小层;主要发育辫状河道、心滩及河漫滩等沉积微相;延10段砂体延伸方向近似南北向,油层组整体河道砂体较发育,厚度大,延伸远,连片性好.

基于现代沉积学理论,采用野外辫状河露头剖面观察实测的方法,并结合钻井资料,对延安组延10岩相类型、岩相组合和沉积特点进行详细研究,探讨研究区沉积相、微相和沉积模式.结果表明:研究区延10组发育4种岩相类型,包括槽状交错层理中粗砂岩相(St)、板状交错层理砂岩相(Sp)、平行层理砂岩相(Sh)和块状构造砂岩相(Sm)及辫状河岩相组合;另外,识别出辫状河沉积相以及心滩、泛滥平原2种沉积微相.研究结果对延安组辫状河岩相组合和沉积相具有一定的指导意义,同时为鄂尔多斯盆地其他层位辫状河沉积研究提供借鉴.

为研究鄂尔多斯盆地上三叠统延长组深湖重力流的沉积特征及其沉积模式,利用钻井岩心,周缘野外露头及钻井测井资料,识别出深水区的块状砂岩、具撕裂屑块状砂岩、平行层理砂岩、沙纹交错层理粉砂岩、同生变形构造粉砂岩、水平层理粉砂岩、块状泥岩等7种岩相类型,代表了浊流沉积(高密度、低密度)、碎屑岩、滑塌岩、深水原地沉积等成因类型;其沉积微相分为水道、堤岸/漫溢、前缘朵体和水道间/深湖泥4种.研究认为,鄂尔多斯盆地南部延长组为一种深湖水道型重力流,由斜坡区向顺着水道延伸方向(或者由水道轴部向侧翼方向),水道的下切侵蚀作用逐渐变弱,水道成因的中厚层砂体发育,且往往垂向上叠置;在水道前端发育朵状体沉积,且侧向迁移频繁,形成了大面积分布、垂向上叠置的中薄层砂体.该研究建立了研究区湖相水道-朵状体的浊流沉积模式,可为研究区深水区的砂体精细刻画提供依据,从而进一步追踪湖底水道砂体及(部分)朵状体沉积.

随着合水地区致密油藏的深入勘探与开发,现有的沉积成因分类已不足以支撑重力流类型的准确划分.为了进一步细分沉积成因类型,以便实现重力流类型的准确划分,通过构型要素分析的方法对合水地区长7段的重力流沉积微相进行了精细刻画.研究认为,合水地区长7段主要发育深水重力流沉积体系,可划分为内扇、中扇和外扇3种沉积亚相.在内扇亚相,发育近源限制性水道沉积微相;在中扇亚相,发育远源水道和溢岸沉积微相;在外扇亚相,发育浊积朵叶体微相.

基于多年对鄂尔多斯盆地白垩纪的研究成果,结合大量野外剖面实测、钻井资料分析,利用沉积相及古地理恢复技术,从沉积体系类型及特征、古地理演化等方面,对研究区白垩纪的古地理及沉积演化进行研究.研究后认为,研究区白垩纪发育的沉积体系有冲积扇、河流、湖泊、三角洲及沙漠沉积体系.在古地理演化过程中,宜君期仅在南缘的宜君—彬州一带发育有冲积扇;洛河期气候干旱,沉积范围大,主要发育沙漠相沉积,其次发育冲积扇、河流、滨浅湖及丘间(沙漠湖);环河—华池期,沉积范围较早期要小,以辫状河、湖泊、(辫状河)三角洲沉积为主,是湖泊发育的鼎盛期;罗汉洞期,盆地再次抬升,气候又转向干旱.边部发育冲积扇、河流相,向盆地西南中心逐渐过渡为沙漠相、河流及湖泊相;泾川期,地层分布范围非常局限,残留厚度也不大.气候转向温润,主要发育湖泊相,其次为河流相.同时,本研究绘制了鄂尔多斯盆地白垩纪各期的沉积相平面展布图,为白垩纪鄂尔多斯盆地原始沉积面貌的恢复提供了新的依据.

某油田西区油藏作为主力开发地区,到了开发中后期主要产油区含水率增加,剩余油分布不能明确刻画.采用深化沉积相研究,明确沉积河道走向,找寻剩余油富集区,进而提出改进措施,实现精细开采,提高本区块的开采率,提高石油产量.

根据大量岩石薄片观察、扫描电镜和X?衍射分析,研究陇东地区典型区块三叠系延长组长6—长8段特低渗透—致密砂岩的岩石学特征、孔隙成因等,探讨成岩作用类型及主要控制因素,剖析延长组长6与长8成岩作用的差异性.研究表明:该区砂岩经历的成岩作用主要有压实作用、胶结作用、溶解作用等,建立了三角洲和重力流成岩演化模式序列,研究区目前处于中成岩A?B期;并从储层形成的物源、沉积环境、古气候等方面的差异性,探讨了华庆区块长63和马岭区块长81成岩作用差异性的成因.由于长6较长8粒度细、杂基含量较高,其压实作用强,原生粒间孔保存较少,早期绿泥石膜胶结不发育,含铁碳酸盐胶结物及自生伊利石含量高,砂岩储层物性较差.

根据典型露头剖面的沉积学研究,采用野外观察与室内研究相结合的方法.分析不同成因砾屑灰岩的识别特征,查明鄂尔多斯南缘奥陶系的沉积体系、岩相古地理特征及沉积模式.研究可知,研究区奥陶系平凉组、背锅山组主要发育开阔海台地、台地边缘礁滩相、台地前缘斜坡相、以及深水斜坡-海槽相;不同成因砾屑灰岩在构造背景、砾屑特征、背景岩石类型等方面具有明显的差异,从而准确地识别和划分了浅水台地与深水斜坡;在此基础上,恢复了平凉期及背锅山期的沉积体系展布,明确了奥陶系岩相古地理的演化,构筑了发育浅水台地、深水斜坡和深水盆地沉积体系的塌积边缘型沉积模式.研究后认为,在继续重视马家沟组古岩溶及白云石化有关储层的同时,也要加强浅水台地礁滩相和深水斜坡区重力流颗粒灰岩储层的勘探.

In order to understand tight sandstone characteristics and formation mechanism,the authors analyzed the distribution and formation mechanism of carbonate cements in terms of petrological and geochemical characteristics of the samples by means of casting thin sections,cathodoluminescence and scanning electron microscopy in the samples,take the Chang 63 sub-member reservoir of Triassic Yanchang Formation in Huaqing area of Ordos Basin as the study object.The result shows that the main types of carbonate minerals are calcite,ferrocalcite,dolomite and ferrodolomite,and different areas show great difference in type distribution,being higher in content in southwest and lower in northeast.The content and type are related to the provenance and the source of calcium ions in aqueous medium,which can be divided into authigenic carbonate and exogenous carbonate.As the pore volume was plugged up by the carbonate cement on a large scale and the later dissolution was lacking,the sandstone of Chang 63 sub-member of Yanchang Formation became densified.On the basis of drawing the contour map of ferrocalcite and ferrodolomite cement in study area,the mechanism of carbonate cements was investigated.It is held that the carbonate cements were mainly formed by the dissolution-reprecipitation of carbonate rock debris and feldspar dissolution-precipitation.The results obtained by the authors can provide reference for fa-vorable prediction of tight oil of Yanchang Formation in Huaqing area,and can also provide reference for microscopic characteristics study of tight hydrocarbon reservoir both in China and abroad.

在对大量钻井岩心观察分析的基础上,结合鄂尔多斯盆地区域地质背景,利用岩性、古生物、沉积构造、粒度分析、地球化学特征等鉴别沉积标志特征,分析鄂尔多斯盆地子洲地区晚古生代各时期沉积相特征,总结其演化规律.晚古生代研究区共发育5种沉积体系,分别是障壁海岸沉积体系、浅海陆棚沉积体系、曲流河三角洲沉积体系、辫状河三角洲沉积体系以及湖泊沉积体系.研究区晚古生代沉积演化经历两大阶段.重点分析山西期与石盒子早期盒8期沉积环境,子洲地区山西组沉积为水下还原环境,受河流三角洲作用控制,仅在山西组早期研究区南部受到短期海泛的影响;石盒子早期研究区处于完全的淡水环境,受辫状河三角洲作用控制.晚古生代沉积时气候特点体现出由温暖潮湿气候向半干旱—干旱气候转变,沉积体系表现为由海相、海陆过渡相向陆相过渡转变的特点.

近年来,鄂尔多斯盆地石油勘探在延长组下组合长9油层组获得了新发现,但对该致密油藏的研究仍处于起步阶段,认识的不足严重制约了致密油藏勘探开发。根据钻井、测井及分析测试资料,对王洼子地区长9致密砂岩油藏成藏条件进行了分析,探讨了油藏富集规律及其勘探潜力。研究表明,该区长9油层组具有较好的成藏条件,长91和长93已见多口高产井,石油勘探已有较大的突破。烃源岩、沉积微相、优质砂体、鼻状隆起等几个因素的优化匹配是长9致密砂岩油藏勘探能够取得突破的关键。据综合分析,洼4井区及洼14—洼11井区成藏条件较好,为下一步的有利勘探区。

The palaeogeomorphic shape of the pre-Jurassie, which is mainly composed of paleochannel, slope ridge and trench, was reconstructed with the mold method. The sedimentation of early Jurrasic was controlled by pre-Jurassic palaeogeomorphology. In the period of Yan 10 deposition, the microfacies were mostly channel sandbar and overbank swamp of braided river subfacies, and in the period of Yan 9 deposition, the microfacies were distributary channels, overbank swamp of delta plain subfacies. In general, the channel sand body was mainly in direction of NW-SE, influenced by the northwest provenance. The relationship of pre-Jurassic sedimentary paleogeomorphology with Yan 10 and Yan 9 petroleum reservoir was analyzed, and the reservoir was mainly distributed in relatively high zone such as slope being adjacent to elevation. The formation and distribution of the reservoir is controlled by the development of channel sand bodies and the exploration area is located in the palaeogeomorphic slope position. The incised valleys of the north paleochannel can serve as the passageway for gas and upward oil migration, produced by Yanchang formation source rocks. Thus, Jurassic petroleum pool may have been well developed in study area and the overlapping area of the pre-Jurassie slope ridge and channels sandbody of Yan 10 and Yan 9 should be the exploration targets in the near future.

Since the exploration objects gradually changed from shallow?water to deep?water area in lacustrine basinsfor China’ s Meso-Cenozoic lacustrine basins, it will break the concept that the deep?water area is a for?bidden zone for hydrocarbon exploration. Fine?grained deposits in the deep?water area were poorly studied in the past, and mainly focusing on the hydrocarbon?generating potential of source rocks. In order to determine the types and origins of the fine?grained deposits in the deep?water area, and to guide unconventional hydrocarbon explora?tions, a case study was made in the Yanchang Formation of the Ordos Basin. Based on a large amount of previous data and combined with modern testing techniques, the sedimentary facies and origins of rocks in the deep?water area were analyzed, especially the characteristics and origins of deep?water autochthonous sedimentation, tuff, deep thermal fluid, distal turbidite and radioactive uranium. It was emphasized that rock and mineral analysis together with geochemical analysis were the main methods to realize fine?grained deposits, among which nano?technology would be the main research method in current and the future. A certain amount of pores developed in the fine?grained deposits in the deep?water area, which were close to source rocks, hence were favorable for hydrocarbon accumulation and exploration.

Palaeogeomorphology is one of the main factor controlling the sedimentary facies type and its distribution in petroliferous basin,and in certain extent,controlling the reservoir and cap combination.Therefore,accurate palaeogeomorphology reconstructions is vital to petroleum exploration,which becomes a study hotspot in the field of international sedimentology.Continental petroliferous basin was selected as the analysis object in this paper,such methods as sedimentology,layer adequation and high resolution sequence stratigraphy were summaried combining with study example,and the control of palaeogeomorphology on sedimentary system was discussed in faulted and depression lake basin,respectively.emphasizing the importance of palaeogeomorphology model reconstructions using 3D reservoir modeling technique.By palaeobathymetric calibration,improving burial history,in order to reconstruct absolute palaeogeomorphology and improve study accuracy,high resolution sequence stratigraphy should be forther emphasized on the research of palaeogeomorphology reconstructions in the near future.

Paleoclimate is important in paleogeographic reconstructions,which is the factor affecting various geologic processes,and formation of deposition and sedimentary mineral deposit.Such methods as petrology,palaeontology,geochemistry,palaeomagnetism physics of the earth are discussed,great potential of methods of geochemistry and physics of the earth in the near future is pointed out,meanwhile,these advanced methods should be closely combined with traditional methods in order to draw reasonable conclusion.

Aim To correctly divide the strata of Yan′an Formation,which is the basis for sedimentary facies and sequence stratigraphy.Methods Based on comprehensive analysis of cuttings debris,logging,outcrop observation,etc,a research is maded on the marker beds′ characteristic of Yan′an Formation.Results Such marker beds as structure isochronous surface in origin,coal bed and carbargiliteor oil shale,large scale sandbody and scouring surface are well developed in Yan′an Formation,which carry obvious characteristic of lithology and electrical property,can be good marker beds for strata division and comparison.Coal bed or oil shale are formed during late period of transgression system tract and early stage of high system tract of the three third-grade sequence in Yan′an Formation.Lithology,thickness and distribution feature of marker beds are controlled by sedimentary facies.Conclusion In view of the fact that thickness in lower part and upper part of Yan′an Formation changing quickly in short distance,in order to correctly divide strata,such factors as marker beds,adjacent well comparison,palaeogeomorphology before Jurassic deposition and denuding upper part of Yan′an Formation should be sufficiently considered.

湖盆古水深的恢复是古湖盆的重要研究内容,对恢复湖盆古水深的沉积学方法、地球化学方法(Th/U比值法)、古生物方法及定性的相对古水深曲线方法等进行了阐述.目前古水深研究多以定性为主,运用古生物资料根据古生物分异度与水深的关系定量恢复古水深,以及根据沉积微相的横向和纵向的相序关系来计算古水深是今后研究的重点.

The provenances of Ordos Basin and its surrounding regions, which all comes from the upper crust, are dominated by felsic rocks, which consist of ancient metamorphic rocks, such as metamorphic volcanic rocks and sedimentary rock of Archaeozoic and Proterozoic, and certain amount of granite and alkali basalt. But compositions of source and structural setting of provenances in the north and south are different. Compositions of major and rare earth elements suggest that sedimentary rocks in both north and south show some differences in area and stratum, and the changes of major element, REE and Eu anomaly are in accordance with the variation trend from oceanic island arc, continental island arc, and active continental margin to passive continental margin. Analysis of major elements indicates that the north provenance derived mainly from plate subduction zones and were related to active continental margin and passive continental margin, with minor related to the island arc of passive continental margin, and were related to tectonic setting of active continental margin and passive continental margin until middle-late Paleozoic. REE contrast analysis shows that the source for the northern basin has affinities to Archeozoic and Proterozoic metamorphotic rocks, such as granitic gneiss, diorite gneiss, adamellite, metamorphotic litharenite, phyllite, etc; that for the southern basin was deeply affected by passive continental margin source, characterized by high SiO2 , low Na2O features, and K2O/Na2O1. All these features are consistent to those (high SiO2 and K2O/Na2O1) of rocks of Archean-Proterozoic Taihua Group, Qinling Group and Kuanping Group. Until the end of Late Paleozoic, the provenance was not affected gradually by active continental margin. Beiqinling intermontane basins characterized by rapid accumulation m langes belong to the outer margin of Ordos Basin and have continuous transitional relationship with the basin. Therefore, both show some inherited relation. The Gd content and (Gd/Yb)N ratios of the Late Paleozoic sedimentary rocks in the Ordos basin vary with time changing, and the analysis shows that the northern source area in Taiyuan period was in rapid tectonic activity period, while the southern source area in Shanxi period was fast active period. This is consistent with the regional tectonic evolution, i.e. the uplift of the northern source area was earlier than that in the south.