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.

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.

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.

Lacustrine carbonate reservoirs, extensively distributed in China, have extensive oil and gas exploration potential. However, such reservoirs are characterized by high content of terrigenous debris and complex lithofacies, and the resultant high difficulty in lithofacies identification severely restrains exploration expansion and efficient development, especially for the Upper Member of the Paleogene Lower Ganchaigou Formation (E32) of the Yingxi area in the Qaidam Basin, with burial depths generally greater than 4000 m. This research targets this area and develops a methodology for detailed lithofacies identification, after systematically investigating the characteristics of lithofacies and well log responses of lacustrine carbonate rocks, on the basis of a massive volume of data of cores, thin sections, and experiments of the study area. The analysis identified lithofacies in the Upper Member of the Paleogene Lower Ganchaigou Formation of the Yingxi area, namely, pack-wackestone, mudstone, laminated carbonate, muddy gypsum, and limy claystone. The analysis of well log response characteristics suggested that natural gamma ray, matrix density, and bulk density were sensitive to lithofacies. Then, for the first time, the rock fabric factor (RFF) method was proposed, and the lithofacies identification plot was based on the calculated RFF and high-definition spectroscopy log. The presented methodology was applied to 55 wells in the study area. The average accuracy of lithofacies interpretation in 14 cored wells reached 82.4%, indicating good application performance. This method improves the lithofacies identification accuracy of lacustrine carbonate rocks, which is of great significance for investigating the reservoir distribution law and guiding exploration and development.

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.

Based on the data of field outcrops, drilling cores, casting thin sections, well logging interpretation, oil/gas shows during drilling, and oil/gas testing results, and combined with modern salt-lake sediments in the Qinghai Lake, the Neogene saline lake beach-bars in southwestern Qaidam Basin are studied from the perspective of sedimentary characteristics, development patterns, sand control factors, and hydrocarbon accumulation characteristics. Beach-bar sand bodies are widely developed in the Neogene saline lake basin, and they are lithologically fine sandstone and siltstone, with wavy bedding, low-angle cross bedding, and lenticular-vein bedding. In view of spatial-temporal distribution, the beach-bar sand bodies are stacked in multiple stages vertically, migratory laterally, and extensive and continuous in NW-SE trending pattern in the plane. The stacking area of the Neogene beach-bar sandstone is predicted to be 3000 km(2). The water salinity affects the sedimentation rate and offshore distance of beach-bar sandstone, and the debris input from the source area affects the scale and enrichment of beach-bar sandstone. The ancient landform controls the morphology and stacking style of beach-bar sandstone, and the northwest monsoon driving effect controls the long-axis extension direction of beach-bar sandstone. The beach-bars have a reservoir-forming feature of "one reservoir in one sand body", with thick beach-bar sand bodies controlling the effective reservoir distribution and oil-source faults controlling the oil/gas migration and accumulation direction. Three favorable exploration target zones in Zhahaquan, Yingdong-eastern Wunan and Huatugou areas are proposed based on the analysis of reservoir-forming elements.

To identify the developmental characteristics and controlling factors of the beach‐bar sandstone in saline lake basins in the Qaidam Basin, China, the lithology and bedding structure of some representative outcrops of the Neogene saline lake basins were comprehensively investigated by means of experimental test data of local drilling cores, casting thin sections, and grain size, together with field outcrops in the basin and the modern salt lake deposition record of Qinghai Lake. Two types of sand bodies in the saline lake basins, that is, delta sand bodies and shore‐shallow lake beach‐bar facies were revealed. Neogene saline lake basins were found to host widespread beach‐bar sand bodies. Lithologically, the sand bodies were composed of fine‐grained sandstone and siltstone, with wavy bedding, low‐angle cross‐bedding, and bimodal cross‐bedding. The beach‐bar sandstone was characterized by multi‐layer superimposition, lateral migration, and NW–SE wide‐coverage continuation. Drilling data showed that beach‐bar sand bodies extended from 10 to 35 km in width and most of them occurred 3–15 km away from braided river delta front. It has been predicted that the total area of beach‐bar sand bodies of 14 sand groups in the Neogene spread across 5,000 km2. Four factors, that is, lake water salinity, terrigenous input, palaeogeomorphology, and monsoons, controlled the construction of the beach‐bar sand bodies developed in the Neogene saline lake of the Qaidam Basin. We can conclude that the settling velocity and transport distance of the sand bodies were affected by the water body salinity in such saline lake basins. Also, the distribution range of the beach‐bar sand bodies was affected by the clastic input from a terrigenous provenance. Furthermore, the wide‐coverage distribution and local enrichment of the beach‐bar sandstone were affected by palaeogeomorphology, and the distribution direction of the beach‐bar sandstone was affected by the driving effect of NW monsoons. We propose a deposition model of the beach‐bar sandstone in saline lake basins that can predict favourable beach‐bar sand body regions, to support the major discoveries of lithologic traps in southwestern Qaidam, China.

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.

为明确英雄岭构造带油气成藏条件、探究油气勘探领域及勘探方向,利用钻井油气显示、有机地球化学、铸体薄片鉴定、实验测试、地球物理、试油气等资料,开展英雄岭构造油气成藏条件分析与有利勘探区带预测.结果表明:油气成藏条件上,明确发育多套烃源岩,主要烃源岩分布在古近系下干柴沟组上段、新近系上干柴沟组;存在碎屑岩、湖相碳酸盐岩和混积岩3类油气储集体;形成源储一体型、上生下储型、下生上储型3种源-储组合关系;英雄岭构造带具有烃源岩条件优越、油气资源基础好,储层类型多样、储集性能优越,晚期构造活动与油气生排烃期匹配性好、油气持续充注条件优越等有利的油气成藏条件.有利勘探区带及领域上,提出古近系碎屑岩(三角洲前缘砂体)勘探方向在构造带的花土沟-红柳泉、油砂山-尕斯等地区,碳酸盐岩勘探方向在构造带的英西-游园沟和尕斯-跃进等地区;新近系碎屑岩(滨浅湖滩坝砂)勘探方向在构造带的狮子沟-花土沟-游园沟-油砂山-英东及其以西地区,碳酸盐岩(藻灰岩、混积岩及灰云岩)勘探方向在构造带东侧的油泉子-开特-黄瓜峁等地区.该研究成果表明英雄岭构造带具有多层系、多类型的立体勘探特征,是发现大型油气田的有利勘探区带.

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.

为了明确柴达木盆地新生代湖相碳酸盐岩类型特征及发育规律,利用野外露头、钻井取芯、显微结构特征等资料,按照碳酸盐岩成因分类法,对碳酸盐岩类型进行划分.结果 表明,柴达木盆地新生代发育两种成因类型碳酸盐岩储层,即生物成因和机械-化学复合成因.生物成因碳酸盐岩为藻灰/云岩类;机械-化学复合成因碳酸盐岩为颗粒灰/云岩类和泥晶灰/云岩.柴达木盆地碳酸盐岩发育颗粒滩-灰/云坪、颗粒滩(鲕粒滩)-藻丘、藻席-灰/云坪、颗粒滩-藻丘(席)-灰/云坪4种类型组合样式;灰/云坪储层在柴达木盆地西部地区大面积分布,颗粒滩储层分布于水体较浅、水动力条件相对较强的滨浅湖亚相带中,藻丘(席)分布在滨浅湖亚相内的清水、富氧环境中.

利用地层孔隙热压生排烃模拟实验方法,开展叠层石灰岩从低熟-成熟-高成熟系列的热演化模拟实验.结果表明:叠层石灰岩单位有机碳的生油产率随着温度增加先增后降,生油高峰约在360℃,对应最大生油产率约为379.99 kg/t,排油率为34％ ～68％;模拟气体产物中以二氧化碳产率最大,其次为氢气产率,烃气产率最小,烃气生成高峰约在380℃,对应最大烃气质量产率为101.74 kg/t;模拟所得残留油和排出油总体上表现为高含非烃和沥青质、低含饱和烃和芳香烃的特点;在含相同有机碳数量的背景下,叠层石灰岩最大生烃产率小于灰质白云岩和灰色泥岩,但高于泥灰岩,尤其是叠层石灰岩具有更高的烃气产率和更低的有效烃源岩有机碳下限.

英雄岭构造带位于柴达木盆地西部地区,先后发现了狮子沟、花土沟、油砂山、英东等多个新近系油气田,是柴达木盆地石油勘探的主战场.为了拓展英雄岭构造带新近系碎屑岩岩性油气藏勘探领域,通过野外露头、钻井岩心、粒度测试等资料的综合分析,明确新近系碎屑岩发育滨浅湖滩坝、辫状河三角洲水下分流河道两种类型砂体.在湖退沉积背景下,受西部物源控制的辫状河三角洲水下分流河道砂体逐步向湖盆进积,北西—南东向斜列式分布的滨浅湖滩坝砂体向湖盆迁移;上干柴沟组辫状河三角洲水下分流道砂体发育在构造带以西地区,滩坝砂体发育在构造带西翼及核部;下油砂山组辫状河三角洲水下分流河道砂体发育在构造带西翼及核部,滩坝砂体分布在构造带核部及东翼.构造演化特征表明,新近系上干柴沟组、下油砂山组沉积时期储层砂体分布在斜坡区,而现今的英雄岭构造带为新近系狮子沟组沉积末期形成的晚期反转构造,早期沉积的砂体在构造反转背景下可形成上倾尖灭岩性圈闭、砂岩透镜体岩性圈闭,是寻找规模岩性油藏的有利勘探目标区.

To examine the reservoir type and distribution regularity of high- and stable-yield lacustrine carbonates in the upper Member of Paleogene Xiaganchaigou Formation of Yingxi region and to determine the high-efficiency hydrocarbon exploration direction, the origin and significance of carbonate breccia in this area were investigated based on comprehensive analysis of a large number of well cores, thin sections, rock and mineral testing and log-seismic data. The study reveals that the carbonate breccia has three origins: (1) Sedimentary breccia, formed by the event-related collapse, fragmentation and re-deposition of the early weakly consolidated carbonate rock in the steep slope of underwater paleohighs due to short-term high-energy water body reformation and other geological processes. (2) Diagenetic breccia, with breccia-like structure, formed by deformation or breaking of host rock due to growth of idiomorphic and coarse crystalline gypsum-salt minerals in the weakly consolidated argillaceous carbonate rock of the penecontemporaneous period. (3) Tectonic breccia, can be further divided into fault breccia and interlayer slip breccia according to their occurrence characteristics, both of which are closely related to activity of the Shizigou thrust Fault. With a large number of partially filled pores, vugs and fractures between breccia, the two types of tectonic breccia are high- and stable-yield reservoirs in deep Yingxi region, and may occur extensively under gypsum-salt detachment layers of adjacent areas, so they are the exploration targets in the next step. Sedimentary breccia and diagenetic breccia are of great significance in searching for large-scale carbonate reservoirs.

The study of sedimentary characteristics and reservoir development of shallow delta-lacustrine system is very important for the petroleum exploration and development of continental lacustrine basin.Based on a large number of drilling cores,logging and experimental analysis,the sedimentary microfacies types,sedimentary characteristics,the distribution and evolution characteristics of delta-front and shore-shallow lacustrine sediments in Youshashan Formation of Yingdong Area are summarized.The result shows that there is a big difference between the delta front and the shore-shallow lacustrine deposits in the sand ratio,stratum structure,microstructure,logging curve combination form and so on.The Pliocene successively developed the progradation sequence of shore-shallow lacustrine deposit,the transition of shore-shallow lacustrine and delta-front deposit.Under the control of deposition,reservoir maturity is not high and diagensis is of alkaline diagenetic characteristics.Microfacies and cement content are the key factors affecting reservoir physical properties.

对柴西地区渐新统膏盐岩的形成环境、成因及分布规律认识不清,制约了油气勘探进展.利用沉积岩石学和地球化学等方法,研究膏盐岩岩石类型及特征、沉积时期水体性质、时空分布特征及发育模式.结果表明:柴西地区渐新统下干柴沟组上段膏盐岩以层状石盐为主,其次为石膏岩和少许钙芒硝及芒硝,膏盐晶体自形程度高,为原生沉积作用形成;膏盐岩主要发育于水退浓缩沉积序列的晚期,古水体环境具有半咸化-咸化、还原、深水和低温等特征,表明湖水蒸发浓缩过饱和结晶是膏盐岩的形成机制.膏盐岩纵向分布受控于湖平面升降,发育6个集中成盐期;平面分布受控于湖底沉积古地貌,呈局限环带状分布且存在多个次级聚盐中心.根据柴西地区渐新统湖盆古水体的演化阶段,将膏盐岩发育模式分为咸化阶段晚期和广盐湖期2种.早期膏盐岩的平面分布相对局限,主要形成于洼陷区;晚期拓展至低隆起区,分布广泛.

The Paleogene Lower Ganchaigou Formation in the west of Yingxiong ridge,Qaidam Basin is originated from saline lacustrine-basin sedimentation with the development of multiphase rock salt (layered halite),of which the origin and development mode is a hot issue to be solved at present.The core data reveal that the complete salt-formation single-phase cycle is an evaporation sedimentary sequence.The lithological sequence assemblage characteristics of prospecting wells show that the lacustrine basin experienced three evolutionary stages,i.e.,semi-saline,salinizing and saline lake.Through the petrography analysis,homogenization temperature test and composition research of the inclusions as well as the analyses of the sulfur,carbon and oxygen isotopes of salt-bearing strata,it is explicitly put forward that the rock salt was generated through low temperature underwater concentration and crystallization,and formed in the confined continental environment with intense evaporation;the material source was carried by terrestrial surface water.Two kinds of salt forming modes were developed in the midlate saline stage and euryhalinous lake stage,and each mode is divided into three evolutionary stages,i.e.,initial saline stage,saline stage and salt forming stage.The comparison and analysis of joint wells indicate that five rock-salt concentration development periods existed,when the saline lake experienced three evolutionary processes,i.e.,the initial stage,peak stage and shrinking stage.The saline lake center had the maximum thickness with limitations in plane distribution,and multiple secondary salt depression centers were formed due to the control of paleo-terrain.The vertical development of multiphase salt rock was caused by the frequent seasonal fluctuation of lake level in terrigenous lake basin.

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.

柴达木盆地目前所发现的油气都围绕着侏罗系、古近—新近系及第四系富烃洼陷区分布.近年来,围绕“富烃洼陷”油气勘探,发现了昆北和英东两个“亿吨级”油田、阿尔金山前东段“千亿方”天然气及扎哈泉“亿吨级”致密油勘探区,勘探成效显著.随着柴达木盆地建设千万吨高原油气田及新区、新领域勘探的迫切需求,借助于中国石油重大科技专项,利用硼元素及黏土矿物资料,引用科奇公式开展古水体盐度恢复,明确柴达木盆地新生界为咸化湖盆沉积.从柴达木盆地新生界咸化特征及与已知富烃洼陷进行类比,结合—里坪坳陷周缘有机地球化学测试资料,提出一里坪坳陷为潜在的生烃洼陷,可能为新的富烃洼陷,围绕该洼陷进行油气勘探将是一个新的接替领域,对柴达木盆地油气勘探具有重大战略意义.