Although numerous studies have shown that deformation within contractional fold-and-thrust belts is significantly affected by the spatial variation of stratum properties, due to the limitations of the available subsurface data quality, more specific research on how stratigraphic sedimentary facies changes influence structural styles is still scarce. Benefiting from the newly-acquired 2D and 3D seismic reflection, well-logging and core data during the hydrocarbon exploration and development, we conducted an integrated study to comprehensively depict the structural geometry and kinematic evolution in the northwestern Qaidam Basin, northern Tibetan Plateau. The interpretations of seismic reflection data indicate that the Lulehe Formation exhibits different deformation behaviors from the margin to the interior of the Qaidam Basin. By integrating well-logging and core data, we propose a depositional model that attributes the sedimentary facies changes in the upper part of the Lulehe Formation to the main controlling factor of the variable structural styles observed in the study area. Moreover, a detailed analysis of growth strata suggests a southwestward propagation of compressional deformation during the Cenozoic. Notably, this finding offers new insights into the structural evolution in the northwestern Qaidam Basin.

The saline lacustrine hybrid sedimentary rocks are complex in lithology and unknown for their sedimentary mechanisms. The hybrid sedimentary rocks samples from the Neogene upper Ganchaigou Formation to lower Youshashan Formation (N1-N21) in the Fengxi area Qaidam Basin, were investigated through core-log and petrology-geochemistry cross-analysis by using the core, casting thin section, scanning electron microscope, X-ray diffraction, logging, and carbon/oxygen isotopic data. The hybrid sedimentary rocks in the Fengxi area, including terrigenous clastic rock and lacustrine carbonate rock, were deposited in a shallow lake environment far from the source, or occasionally in a semi-deep lake environment, with 5 lithofacies types and 6 microfacies types recognized. Stable carbon and oxygen isotopic compositions reveal that the formation of sedimentary cycles is controlled by a climate-driven compensation-undercompensation cyclic mechanism. A sedimentary cycle model of hybrid sedimentary rocks in an arid and saline setting is proposed. According to this model, in the compensation period, the lake level rises sharply, and microfacies such as mud flat, sand-mud flat and beach are developed, with physical subsidence as the dominant sedimentary mechanism; in the undercompensation period, the lake level falls slowly, and microfacies such as lime-mud flat, lime-dolomite flat and algal mound/mat are developed, with chemical-biological process as the dominant sedimentary mechanism. In the saline lacustrine sedimentary system, lacustrine carbonate rock is mainly formed along with regression, the facies change is not interpreted by the accommodation believed traditionally, but controlled by the temporary fluctuation of lake water chemistry caused by climate change. The research results update the interpreted high-resolution sequence model and genesis of hybrid sedimentary rocks in the saline lacustrine basin and provide a valuable guidance for exploring unconventional hydrocarbons of saline lacustrine facies.

柴达木盆地昆北断阶带为大型山前压扭冲断构造带，该构造带上的昆北油田切12区下干柴沟组下段发育厚层冲积扇沉积的砂砾岩储层.明确储层微观特征及发育控制因素，对冲断带砂砾岩储层评价与油藏治理具有重要意义.运用铸体薄片、X-衍射、扫描电镜、常规压汞与恒速压汞等测试分析资料，系统研究冲积扇砂砾岩储层微观特征，明确储层发育的主控因素.结果表明，切12区砂砾岩储层具有成分成熟度低、结构成熟度低的岩石学特征，储集空间类型具双重孔隙介质特征，发育2类储层结构模态、4类储集空间类型、4类储层孔隙结构，储层物性为低孔、特低渗型储层，成岩作用阶段为早成岩阶段B期.在砂岩动力成岩作用相同的地质背景下，成岩作用对储层改造的影响是相对均衡的，储层发育程度的差异主要受控于沉积作用差异而导致的碎屑组成与结构差异，泥质含量是储层发育程度差异的主控因素，明确泥质含量上限为8%，颗粒分选对储层性质起重要控制作用.建立了基于泥质含量、物性、孔隙结构和产能指标的储层评价分类标准，将砂砾岩储层划分为4类；运用该认识指导油藏综合治理，并取得应用实效.

利用钻井岩心、测井、地震和实验测试等资料,对柴达木盆地九龙山地区中侏罗统沉积特征及成藏条件进行分析.结果表明:①九龙山地区中侏罗统发育潮湿气候下的陆相含煤沉积建造,属于湿地型辫状河三角洲沉积.②中侏罗统发育3类岩相组合:第1类是浅灰色、棕灰色泥岩与砂岩、含砾砂岩、砂砾岩和砾岩互层;第2类是煤层、深灰色碳质泥岩与砂岩、含砾砂岩和砾岩互层;第3类是深灰色碳质泥岩、油页岩和泥岩互层.3类岩相组合分别对应辫状河三角洲的上平原、下平原—前缘和湖相沉积.③中侏罗统沉积时期河道较频繁迁移,砂体在平面上呈辫状、网状和朵状分布,具有多期叠置、侧向变化较快的特征.研究认为中侏罗统辫状河三角洲下平原与前缘河道砂体的油气成藏条件优越,是九龙山地区常规油气勘探的重要领域,湖相油页岩是九龙山地区非常规油气勘探的潜在领域.

In view of the key geological factors restricting reservoir development, the reservoir heterogeneity of an alluvial fan sandy conglomerate reservoir in the Qie12 block of Qaidam Basin, Northwest China, and its influence on remaining oil distribution, were studied according to geology, wireline logging data, and dynamic production data. This study illustrates that the difference in pore structures, which are controlled by different sedimentary fabrics, is the main cause of reservoir microscopic heterogeneity. Besides, the temporal and spatial distribution of architectural units in the alluvial fan controls reservoir macroheterogeneity. Our results show that the thick sandy conglomerate develops two types of pores, two types of permeability rhythms, two types of interlayers, two types of interlayer distribution, two types of effective sand body architecture, and four types of sand body connecting schemes. The strongest plane heterogeneity is found in the composite channel unit formed by overlapping and separated stable channels of the middle fan, and the unit’s permeability variation coefficient is >0.7. However, the variation coefficient in the range of 0.3–0.5 is found in the extensively connected body unit sandwiched with intermittent channels of the inner fan. The distributions of the remaining oil vary significantly in different architectural units because of the influence of reservoir heterogeneity, including distribution patterns of flow barriers, permeability rhythm, and reservoir pore structures. The composite channel unit formed by overlapping and separated stable channels, or the lateral alternated unit with braided channel and sheet flow sediment of the middle fan, is influenced by the inhomogeneous breakthrough of injection water flowing along the dominant channel in a high-permeability layer. The microscopic surrounding flow and island-shaped remaining oils form and concentrate mainly in the upper part of a compound rhythmic layer. Meanwhile, in the extensively connected body unit sandwiched with intermittent channels of the inner fan, poor injector–producer connectivity and low reservoir permeability lead to a flake-like enrichment of the remaining oil.

利用露头、钻井、地震及大量实验分析资料,从现今地层结构、沉降-沉积速率、古水体盐度、岩石组合及沉积相展布、烃源岩有机质类型等方面,论证了柴达木盆地腹部一里坪坳陷与柴西坳陷之间发育大型水下古隆起,并通过构造解析和古地貌恢复,分析其演化过程,最后从油气成藏角度阐述了古隆起对下一步油气勘探的意义.研究表明:①古新世早期,受早喜马拉雅挤压造山运动影响,形成了古隆起雏形,平面上呈北西—南东向展布,分隔了其东、西两侧的一里坪坳陷与柴西坳陷;始新世至渐新世,古隆起具有很好的继承性,下干柴沟组沉积时期隆起区最大面积约为3 500 km2;至中新世晚期,受柴西沉积中心向东迁移及南北向物源补给的影响,古隆起演变为宽缓斜坡.②古隆起对油气成储、成烃、成藏具有控制作用:古隆起南北两端近物源区发育规模三角洲砂体,而中心主体区远离物源,处于欠补偿咸化水体环境,发育规模湖相碳酸盐岩储层;受古隆起的分隔影响,西侧柴西坳陷下干柴沟组上段—上干柴沟组已证实发育优质咸化湖相烃源岩,东侧一里坪坳陷可能发育有效烃源岩;古隆起是油气运移有利指向区,有利于油气聚集成藏,可作为下一步有利勘探区带.

昆仑山前带古近系下干柴沟组下段是柴达木盆地油气勘探的重点目的层.受砂岩储层发育程度差异所控制,昆仑山前带不同地区油气富集程度存在差异.为了明确储层的差异性及形成机制,利用岩心、测井及分析化验等资料,对昆仑山前带的切6区、乌南斜坡带、东柴山地区及弯西构造带的储层特征及控制因素进行了分析,认为下干柴沟组下段储层在时空上的差异性明显.昆仑山前带下干柴沟组下段发育以原生粒间孔为主的碎屑岩孔隙型储层,储层砂体成因类型为辫状河三角洲相的平原分流河道、前缘水下分流河道、河口坝、席状砂及滨浅湖相的滩坝.沉积相及成岩作用的双重叠加影响导致昆仑山前带储层发育程度存在明显差异.在同等埋深条件下,受沉积微相控制的储层沉积组构差异与砂体规模差异是储层物性差异的主因,辫状河三角洲前缘水下分流河道储层物性最好,其次为河口坝、平原分流河道,滩坝与席状砂的储层物性较差.在不同埋深条件下,受最大古埋深和古地温梯度等因素影响而形成的差异压实作用是不同区带储层物性差异的主因,切6区和弯西构造带的储层物性最好,乌南斜坡带的储层次之,东柴山地区的储层物性差.

我国湖相碳酸盐岩储层分布广泛,具有极大的油气勘探前景.但该类储层陆源碎屑含量高、岩相种类多,导致岩相识别困难且严重制约了该领域勘探拓展和高效开发,这在埋藏深度普遍大于4000m的柴达木盆地英西地区古近系下干柴沟组上段(E32)尤为典型.以英西地区为例,充分利用区内大量岩心、薄片和实验分析资料,系统分析湖相碳酸盐岩岩相特征及测井响应特征,并建立了识别方法和图版.分析结果表明,英西地区E32发育颗粒灰云岩、泥晶灰云岩、纹层状灰云岩、泥质膏岩和灰云质泥岩等5种类型的岩相.基于测井响应特征分析,确定自然伽马、骨架密度、体积密度为岩相识别敏感参数,进而首次提出岩石结构因子(RFF)技术;利用计算得到的RFF参数,结合元素测井资料建立了岩相识别图版,将其应用于研究区48口井,在12口取心井中岩相解释平均符合率达到80.2％,应用效果较好.岩石结构因子技术提高了湖相碳酸盐岩岩相识别符合率,对研究储层分布规律、指导勘探开发具重要意义.

以柴达木盆地英雄岭构造带西段(英西地区)始新统为研究对象,综合岩心、全岩X衍射、铸体薄片、阴极发光、扫描电镜、碳氧同位素、溶蚀模拟实验等测试结果,探讨湖相混积型碳酸盐岩储层的基本特征、成因机制和发育模式.结果表明:研究区储层岩矿组成以碳酸盐矿物为主,并与陆源碎屑、蒸发岩矿物和黏土矿物等混积形成混积型碳酸盐岩;按岩性可分为颗粒灰云岩、含膏灰云岩、泥晶灰云岩、纹层状灰云岩和角砾状灰云岩5种;储集空间存在孔、洞、缝等多种形式,孔径尺寸范围从纳米级到厘米级.岩性的多样性决定了储集空间具有多种尺度和多种成因,可将储层划分为白云石晶间孔型、溶蚀孔型、裂缝-角砾间孔(洞)型3类储层.晶间孔型储层形成于准同生期的白云石化作用,是咸化湖盆周期性咸化的必然结果,该类储层分布广,是湖相混积型碳酸盐岩储层的主要类型;溶蚀孔型储层是准同生期大气淡水溶解蒸发岩矿物的结果,优先发育于洼中古隆起内含膏灰云岩和颗粒灰云岩中,分布相对局限.裂缝-角砾间孔(洞)型储层为构造成因,产生于狮子沟断层沿膏盐层发生大规模逆冲、滑脱变形的过程中,呈连片分布.

利用大量的岩心实验分析资料系统地研究了柴达木盆地西部同沉积体系和不同区带之间下干柴沟组下段碎屑岩储层物性差异的主控因素,指出沉积环境、岩石学特征、砂体厚度、地层埋藏史、地温梯度背景和湖水古盐度的不同是造成储层物性差异的重要因素.柴达木盆地西部下干柴沟组下段广泛发育的三角洲平原分流河道砂、三角洲前缘水下分流河道砂和滨浅湖滩坝砂是优质储层发育的基本条件.储层砂体厚度、杂基含量和碎屑粒径是储层物性的重要控制因素,成岩作用对储层的演化和储集性能具有决定性作用,其中压实作用对储层物性影响最大,胶结作用是局部区带储层物性重要控制因素.同沉积体系三角洲平原分流河道砂的碎屑颗粒分选和杂基含量控制储层压实程度的差异,三角洲前缘水下分流河道砂和滨浅湖滩坝砂厚度控制了储层胶结强度差异;不同区带地层埋藏史和地温梯度背景造成储层的较大压实差异,湖水古盐度沿盐湖中心环带状分布造成储层在平面上的胶结强度差异.

Taking the mixed pre-salt carbonate rocks in the upper member of Eocene Xiaganchaigou Formation (E32) of Yingxi area in the Qaidam Basin as an example, the lithofacies and controlling mechanisms of reservoir formation are analyzed based on a large dataset of cores, thin sections and geochemical analysis. The reservoirs in E32 pre-salt layers have five types of lithofacies, of them, mixed granular calcareous dolostone, massive calcareous dolostone, plaque calcareous dolostone, and laminated dolomtic limestone are of sedimentary origin, and breccia calcareous dolostone is of tectonic origin. The four types of sedimentary lithofacies are divided into two types of saline sedimentary sequence lithofacies combinations, low-energy type in the sag area and low to high-energy type in the slope and paleo-uplift zone in the depression. Affected by high-frequency supply of continental clastic material, the two types of salty sedimentary sequences are mostly incomplete subtypes of lithofacies. Lithofacies have strong impacts on pre-salt reservoirs in E32: (1) Lithofacies type and sedimentary sequence controlled the formation and distribution of dolomite intercrystalline pores and dissolved pores during the pene-sedimentary period. (2) The structure of laminated dolomitic limestone controlled the formation of large-scale laminated fractures and high permeability channels during the diagenetic period. (3) Granular, massive, plaque calcareous dolostones have low mud content and strong brittleness, in the late tectonic reactivation period, the distribution of the three types of lithofacies, together with their distance from the top large slip faults and secondary faults, controlled the formation and distribution of high-efficiency fracture-cave brecciaed calcareous dolostone reservoirs. The above research led to the composite lithofacies-tectonic formation model of pre-salt reservoir in E32 of Yingxi area. The tempo-spatial distribution of tectonic breccia calcareous dolostone reservoirs, laminated dolomitic limestone shale oil reservoirs and granular, massive calcareous dolostone dissolved-intercrystalline pore tight reservoirs in various structural belts of the studied area have been figured out. These findings gave new insights into tight-shale oil accumulation theory in mixed carbonate successions from saline lacustrine basins, aiding in high efficient exploration and development of petroleum in the studied area.

精细刻画砂岩储层内部结构,可为柴达木盆地西部(柴西)斜坡区古近系下干柴沟组下段岩性油气藏勘探开发指明方向.以高精度层序地层学、砂体构型分析理论和方法为指导,以3D地震、钻/测井、岩心资料为基础,井震联合标定,综合分析了柴西斜坡区下干柴沟组下段层序地层发育规律与层序格架内砂体结构特点.结果表明,柴西斜坡区下干柴沟组下段整体为一个区域性湖侵序列,内部可划分为2个三级层序,4个四级层序(EMSQ1～4).下干柴沟组下段沉积期,由早至晚,A/S(可容纳空间与沉积物供给比值)持续增大,四级层序结构由向上变深的半旋回型逐渐转变为向上变浅为主、向上变深为次的非对称型.沉积相则由辫状河三角洲平原演变为前缘、滨浅湖亚相.研究区主要发育分流河道、水下分流河道、滩坝3类储层砂体,砂体叠加样式和分布规律与四级层序结构相关.三角洲平原分流河道砂体主要发育于EMSQ1中,砂体相互切割和叠置程度高,连通性好;三角洲前缘分流河道砂体主要发育于EMSQ2～3中,多呈叠加-孤立型,连通性差;滨浅湖滩坝砂体主要发育EMSQ4中,砂体呈孤立状,层内连通性佳,层间连通性差.指出现阶段岩性油气藏勘探应重点围绕EMSQ4层序内发育的滨浅湖滩坝砂体展开.

针对塔里木盆地库车坳陷依奇克里克地区中—下侏罗统深层砂岩储层成岩作用复杂、非均质性强、储层特征及其成因不明确的特点,综合利用铸体薄片、扫描电镜、物性分析、X射线衍射、CT扫描等多种分析手段,并结合区域地层埋藏史、古地温史、Ro演变史、沉积相等相关研究成果,详细分析了中—下侏罗统储层成岩作用演化阶段及其物性控制因素。研究结果表明:①中—下侏罗统储层具有低成分成熟度、高塑性岩屑含量及中等结构成熟度的特征。②储层现今主体埋深为4000～5000m,储层储集空间以次生溶蚀孔和裂缝为主,平均孔隙度为7.21%,平均渗透率为9.15mD,总体为低孔低渗储层,部分储层由于发育构造裂缝而渗透率较高。③储层成岩演化可分为两个阶段:第一阶段发生在新近纪之前,成岩作用为初期沉积埋藏压实减孔和长期浅埋藏期腐殖酸溶蚀增孔;第二阶段发生在新近纪之后,发生的成岩作用为储层快速深埋侧向挤压压实减孔和大量伊利石生成胶结减孔,并伴随发育大量裂缝改善储层渗透率。④优质储层物性主控因素为沉积水动力条件、后期成岩作用和构造裂缝发育。富含石英等刚性颗粒的粗砂级辫状河河道和水下分流河道砂岩有较强的抗压实能力,是优质储层形成的沉积基础。裂缝的发育大大改善了研究区储层的渗透率,是优质储层发育的主要控制因素。

Understanding the sedimentary sequence and architecture is important for planning the development strategy. We illustrate a case study of analyzing the sequence and architecture of a sandy conglomerate reservoir by integrating geology, petrophysics, seismic, and development data. The analysis indicates that the depostional environment of the target lower part of the Ganchaigou Formation is an alluvial fan. We defined eight lithofacies according to the core analysis and five sedimentary microfacies by integrating the core and petrophysical data. We next propose four sedimentary architectural models by integrating the lithofacies result, microfacies analysis, and high frequency sequence models. The four architecture models include the extensively connecting body sandwiched with intermittent channels, the composite channel formed by the overlapping and separation of stable channels, the lateral alternated braided channel and sheet flow sediment, and the runoff channel inlaid in flood plain mudstone. We finally build an architecture model for the alluvial fan. The model of the alluvial fan overall shows an upward-fining grain-size features and this feature indicates that the alluvial fan belongs to a retrograding sequence. The built model consists of six alluvial fan bodies that migrates from north.

塔里木盆地塔北隆起西部温宿凸起周缘-英买力隆起地区库姆格列木群底砂岩段是近年来岩性油气藏勘探的热点层位,且玉东1井区已获得了规模的油气产量,但底砂岩段高精度层序地层特征、沉积微相类型及其时空演化规律有待落实.综合利用岩心、钻井、测井和地震资料,识别可以等时追踪对比的标志层、层序界面和湖泛面,构建底砂岩段的高精度层序地层格架,分析各高频层序单元的沉积微相类型和特征,并揭示沉积相的时空演化规律.库姆格列木群底砂岩段为三级层序ESQ1的上升半旋回,可分为4个准层序组,从下到上依次为4砂组、3砂组、2砂组和1砂组.库姆格列木群底砂岩段沉积时期为湖水不断变深、湖盆逐渐扩大的"水进砂退"的沉积背景,发育扇三角洲、辫状河三角洲和湖泊3种沉积相类型,其中4砂组至3砂组沉积时期,为低可容纳空间的低位域体系,物源供给充足,且湖平面上升缓慢,温宿凸起物源区和英买力隆起物源区均发育较大规模的三角洲,英买力隆起物源区还发育规模较大的滨浅湖砂坝.2砂组至1砂组沉积时期,为高可容纳空间的湖侵域体系,湖水迅速变深,温宿凸起物源区沉积物供给迅速减少,扇三角洲迅速向盆地边缘退积迁移,湖水将早期砂体淘洗再沉积形成小型砂坝.英买力隆起物源区三角洲逐渐萎缩,滨浅湖砂坝规模显著变小.

柴达木盆地昆北油田切12区发育厚层砂砾岩油藏.砂砾岩成因类型及分布规律认识不清是制约油藏开发的关键地质因素.综合利用地质、测井、地震及开发动态等资料,在等时层序地层格架内,系统研究砂砾岩的成因类型、分布规律及其对油气富集的控制作用.研究结果表明,切12区下干柴沟组下段发育冲积扇沉积,可划分出辫状水道、泥石流、漫流沉积、径流水道及洪泛平原5种沉积微相类型,可建立“泛连通体”夹间歇性水道、稳定水道形成的叠置分隔复合水道、辫状水道与漫流沉积侧向相间、径流水道镶嵌于洪泛平原泥岩4个沉积构型单元.垂向上,冲积扇整体表现为粒度下粗上细、湖进退积型的沉积序列;平面发育6个冲积扇体,呈由北向南迁移的规律.沉积相带对油气分布具明显控制作用,沉积构型单元控制油气纵向富集,扇体变迁控制油气平面聚集.

库车坳陷东部下侏罗统煤系地层中酸性流体对长石的溶蚀作用普遍存在,薄片显示长石和岩屑颗粒中发育大量次生溶孔.不同的成岩作用条件下,长石溶蚀作用强弱、长石溶蚀产物类型和长石溶蚀产物量不同,对储集层物性影响具有差异性.以普通薄片、铸体薄片和扫描电镜资料为基础,利用全岩分析、黏土矿物分析和流体包裹体数据,分析了储集层中长石溶蚀作用、溶蚀成岩环境和不同成岩环境中长石溶蚀产物差异性及对储集层物性的影响.研究表明,库车坳陷东部迪北地区下侏罗统储集层中,长石溶蚀作用发生在相对封闭的高温成岩环境中,高温条件下长石溶蚀速率大,而封闭成岩环境中流体流动速度慢,因此,长石溶蚀产物就近大量沉淀于粒间孔隙和粒内孔隙中.当埋深小于4000m(温度小于110℃)时,长石溶蚀产物主要是硅质和高岭石,高岭石呈分散质点武分布,未把孔隙充填满,晶间孔发育且连通性好,一定程度上改善了储集层的物性;当埋深大于4000m(温度大于110℃)时,长石溶蚀产物主要是硅质和伊利石,毛发状和片状的伊利石以孔隙搭桥武把砂岩孔隙充满,基本未剩下孔隙空间,且易形成碎片堵塞孔喉,降低了储集层的孔隙度和渗透率.吐格尔明地区下侏罗统储集层长石溶蚀发生在相对开放且埋藏较浅的成岩环境中,长石溶蚀产物能被有效带出溶蚀区,仅沉淀少量硅质和高岭石,长石溶蚀对储集层的增孔作用明显好于迪北地区,为有利的溶蚀成岩区.

以柴达木盆地切12区冲积扇砂砾岩油藏为例,针对制约油藏开发的关键地质因素——储层非均质性,运用地质、测井及生产动态等资料,深入剖析砂砾岩储层非均质特征及其对剩余油分布的影响,认为沉积组构差异控制形成的储层孔隙结构差异是储层微观非均质性的主因,冲积扇沉积构型单元时空分布是储层宏观非均质性的主控因素.研究结果表明:厚层砂砾岩发育2类储层孔隙结构、2类渗透率韵律类型、1种夹层类型、2类夹层分布样式、2种有效砂体结构、4类有效砂体连通模式,扇中复合水道平面非均质性最强,渗透率变异系数大于0.7,扇根“泛连通体”平面非均质性中等,渗透率变异系数介于0.3～0.5.储层非均质性主要通过沉积构型单元的渗流屏障分布样式、渗透率韵律性、储层孔隙结构等方面影响剩余油的分布,导致不同构型单元剩余油分布规律不同.在扇中复合水道及水道萎缩期单元内,受注入水沿高渗层大孔道非均匀突进的影响,形成绕流、孤岛状等微观剩余油,且富集于复合韵律层的上部;在扇根“泛连通体”单元内,受注采连通性差和储层低渗透性的影响,剩余油片状富集.

Using a large amount of drilling and experimental analysis data, this paper evaluates four potential fields of tight oil exploration in western Qaidam Basin from comprehensive analysis of geological conditions such as sedimentary environments, source rock evaluations, reservoir characteristics, and source-reservoir relationships. Influenced by continuous uplift of Tibet Plateau since Paleogene, the sedimentary environment of the western Qaidam Basin exibits three characteristics: (1) a paleo-topographic configuration consisted of inherited slopes, depressions and paleohighs; (2) frequent alternation of relative humid and arid paleoclimate; and (3) oscillation of salinity and level of the paleo-lake water. Preferential paleo-environment resulted in two sets of large-scale source rocks with high efficiency and two types of large-scale tight reservoir rocks (siliclastic and carbonate), deposited during the late Paleogene to early Neogene. The above source and reservoir rocks form favorable spatial relationships which can be classified into three categories: symbiotic, inter and lateral. Based on sedimentary environments and reservoir types, tight oil resource in western Qaidam Basin can be divided into four types, corresponding to four exploration fields: salty lacustrine carbonate tight oil, shallow lake beach-bar sandstone tight oil, delta-front-sandstone tight oil and deep lake gravity-flow-sandstone tight oil. The temporal and spatial distribution of tight oil has characteristics of layer concentration, strong regularity and large favorable area, in which the saline lacustrine carbonate and shallow lake beach-bar sandstone tight oil are the best exploration targets in the western Qaidam Basin.