Further Recognition of Petroleum Exploration Potential of Marine Carbonates in Western Tarim Basin

A series of significant discoveries in marine carbonate rocks show great petroleum exploration potential in the Tarim Basin. However, the oil and gas fields discovered in the carbonate rocks are mainly distributed around the Manjiaer Sag in the eastern Tarim Basin. Some explorations occurred and no oil or gas field was discovered around the Awati Sag in the western Tarim Basin. Information from wells and outcrops reveals that there are excellent oil and gas source rock conditions around the Awati Sag. Transformed reef-shoal reservoirs could be formed in the Ordovician carbonate rocks with paleo-geographic background and hydrothermal conditions. Therefore, it is necessary to make a systematical study and overall evaluation of the potential of the periphery of the Awati Sag in terms of source rock evolution, resource potential, high-grade reservoir formation and distribution, and main factors controlling hydrocarbon migration and accumulation.

Combination Patterns and Depositional Characteristics of Ordovician Carbonate Banks in the Western Tarim Basin,China

The combination patterns and depositional characteristics of the carbonate banks are investigated based on outcrop sections, thin sections, and carbon isotopes of Ordovician in the western Tarim Basin, China. Four carbonate bank combination patterns are deposited in the Ordovician, western Tarim Basin, including： Reef-Bank Complex （RBC）, Algae-Reef-Bank Interbed （ARBI）, Thick-Layer Cake Aggradation Bank （TLCAB）, and Thin-Layer Cake Retrogradation Bank （TLCRB）. All combination patterns show clear periods vertically. The RBC is mainly composed of reefs and bioclastic banks, and the dimension of the RBC depends on the scale of the reefs. Bioclastic banks deposits surround the reefs. The range of the ARBI is determined by the scale of algae-reefs, algae peloid dolomite microfacies and algal dolomite microfacies deposit alternating vertically. TLCAB and TLCRB are deposited as layer-cakes stacking in cycles and extending widely with cross bedding developed. The grains of TLCAB and TLCRB are diverse and multi-source. With the impacting of relative sea level change, biological development and geomorphology, the ARBI, TLCAB or TLCRB, RBC are successively developed from the Lower Ordovician Penglaiba Formation to the Middle Ordovician Yijianfang Formation. The depositional environment analysis of Ordovician indicates that the RBC and ARBI can form effective oil and gas reservoirs, and the TLCAB and TLCRB have the potential to form the huge scale oil and gas reservoirs and to be the crucial targets of exploration for the Ordovician carbonate banks in the future.

Cretaceous-Paleocene Foraminiferal Communities from the Western Tarim Basin and Their Environmental Significance

Foraminifera is one of the most important fossil faunas of the marine Cretaceous and Paleocene in the Western Tarim Basin, which can be divided into 9 communities. This paper deals mainly with the changes of environments in which the foraminiferal communities existed,especially with the changes of temperature and salinity revealed by analyses of test composition and trace elements in the tests , and by statistic studies of species density, richness , diversity ,equitability and dominance .

Processes and causes of Phanerozoic tectonic evolution of the western Tarim Basin,northwest China

This paper addresses the Phanerozoic tectonic evolution of the western Tarim Basin based on an integrated stratigraphic,structural and tectonic analysis.P-wave velocity data show that the basin has a stable and rigid basement.The western Tarim Basin experienced a complex tectonic evolutionary history,and this evolution can be divided into six stages:Neoproterozoic to Early Ordovician,Middle Ordovician to Middle Devonian,Late Devonian to Permian,Triassic,Jurassic to Cretaceous and Paleogene to Quaternary.The western Tarim Basin was a rift basin in the Neoproterozoic to Early Ordovician.From the Middle Ordovician to Middle Devonian,the basin consisted of a flexural depression in the south and a depression that changed from a rift depression to a flexural depression in the north during each period,i.e.,the Middle-Late Ordovician and the Silurian to Middle Devonian.During the Late Devonian to Permian,the basin was a depression basin early and then changed into a flexural basin late in each period,i.e.,the Late Devonian to Carboniferous and the Permian.In the Triassic,the basin was a foreland basin,and from the Jurassic to Cretaceous,it was a downwarped basin.After the Paleogene,the basin became a rejuvenated foreland basin.Based on two cross sections,we conclude that the extension and shortening in the profile reflect the tectonic evolution of the Tarim Basin.The Tarim Basin has become a composite and superimposed sedimentary basin because of its long-term and complicated tectonic evolutionary history,highly rigid and stable basement and large size.

The Depositional Environment of the Cretaceous Kizilsu Group in Xinjiang——With a Discussion of the Lowermost Marine Horizon of the Cretaceous in the Western Tarim Basin

In this paper. it is demonstrated that there exist marine horizons in the upper part of the lower subcycleand the upper subeycle of the Kizilsu Group in Xinjiang. based on new evidence of authigenic glauconite.boron content. carbon and oxygen stablc isotopic analyses. and lithological and sedimentary features. The up-per part of the lower subeycle is the lowermost marine horizon of the Cretaceous in the western Tarim Basin,which is inferred to be of Barremian age.

Geochemistry of Brines from Salt Ore Deposits in Western Tarim Basin

In the geological evolution of the Tarim Basin, many transgressions and relictions happened. So there have been plentiful sources of salt. Moreover, because of uttermost drought, a lot of salt has been deposited. It is possible to find potash salt in this area. In our fieldwork, we have found salt and brine in western Tarim Basin. Based on a geological survey and the characteristics of sedimentary facies and paleogeography, this paper deals with the geochemical parameters and discusses the possibility of formation of potash salt in terms of the chemical analyses of samples collected from western Tarim Basin. Results of brine analysis lead to some conclusions: most of these salt brines have eluviated from very thick halite beds, mainly chloride-type salt and this kind of halite does not reach the stage of potash deposition in all aspects; WKSL (Wukeshalu) occupies a noticeable place, and we should attach importance to this district because there have been some indicators of the occurrence of potash deposits as viewed from the contents of Br and K. Finally, low Br contents are recognized in the Tarim Basin as a result of salt aggradation, and this point of view has been proved by the results of this experiment and the data available. It cannot depend upon the index of Br to judge the evolution stage of halite. We must look for other facies of potash except marine facies.

Orbital and Millennial-Scale Climate Variability over the Past 76 ka in the Western Tarim Basin, Northwest China

Paleoclimate changes during the last glacial in the arid central Asia are not as well understood as the monsoon-dominated areas of Asia. Here we report a 75-m-long sediment core over past 120 kyr based on astronomical tuning combined with the optically stimulated luminescence(OSL) dating in the Kashi depression of the western Tarim Basin, Northwest China. Analysis of grain size and highresolution gamma ray(GR) logs from the KT11 borehole across the last glacial period yields a climate history for the Tarim Basin which reflects the variations of its temperature and the hydrological cycles. Comparison of these records with north hemisphere summer insolation, the Greenland ice core temperature, stalagmites and the loess from the nearby region indicates that the deposits in the fluvio-lacustrine system of the Kashi depression responded to climate change at the Younger Dryas(YD), six Heinrich cooling events and the Dansgaard-Oeschger cycles. Our work indicates that the alternations between warm-humid and cold-dry climates were prevalent in the western Tarim Basin during the last glacial period, showing an in-phase pattern with the climate variations of the East Asian Monsoon, controlled ultimately by precession and North Atlantic Ocean climate variability on orbital-millennial time scales.

Integrated geophysical evidence for a new style of continent-continent collision beneath the western Kunlun in the northwestern China

Along the western Kunlun-Tarim-Tianshan geoscience transect in the northwestern China, an integrated geophysical investigation was carried out. Owing to the abominable natural conditions there, the sounding profile could not cross the whole transect, consequentially, a variety of velocity structures in the transverse and vertical orientations beneath the whole transect were not obtained, such as the case within the western Kunlun orogenic belt. To supply a gap of deep seismic soundings within the western Kunlun orogenic belt, we used the Bouguer gravity anomaly data and the relationship between the compressive wave and the density to obtain the density structure of the crust beneath the western Kunlun and the southern Tarim basin by a forward fitting of gravity anomalies within the two-dimensional polygonal model of uniform medium. The crust of the Tarim basin with a rigid basement was like an asymmetrical arc, whose surface feature was the Bachu uplift in the middle of the Tarim basin. Beneath the conjoint area between the Tarim basin and the western Kunlun belt, there was a V-shape structure located just up to the top of the uplifted Moho. The multi-seismological structures jointly revealed that the face-to-face continent-continent collision beneath the western Kunlun is a new structural style within the continent-continent collision zone, which is a real model proved by the numerical modeling.

塔里木盆地顺北西部地区火成岩侵入体发育特征及其与断裂耦合关系

塔里木盆地顺北西部地区火成岩侵入体分布广泛,对地层和含油气系统改造作用明显,但该地区火成岩侵入体发育特征及其与深部走滑断裂带之间的耦合关系并不十分清楚。基于顺北西部地区最新二维和三维地震资料,精细刻画了火成岩侵入体形态特征,划分了火成岩侵入体不同类型及组合关系,判别了火成岩侵入体发育期次,确定了火成岩侵入体与深部走滑断裂耦合关系。结果表明:(1)顺北西部地区火成岩侵入体具有“一”字形、舌形、碟形以及半碟形几种形态类型。(2)单一侵入岩床通过相接、相连及错断组合形成岩床复合体。(3)火成岩侵入体主要分布于中-下奥陶统顶面至中-下泥盆统顶面之间,侵入岩床活动类型包括单期单层、单期多层和多期多层3类。(4)不整合面和断裂作为岩浆侵入的通道,控制了火成岩侵入体发育数量和规模,导致研究区南部和北部侵入作用存在明显差异。(5)研究区北部深部走滑断裂作为岩浆主要侵入通道,纵向侵入作用较强;南部岩浆以不整合面为主要侵入通道,横向侵入作用更强。

塔里木盆地西北缘乌什西次凹的地层系统和构造特征

乌什西次凹位于塔里木盆地西北缘,隶属于库车坳陷的乌什凹陷。它位于南天山主山脉(哈尔克山)和塔里木盆地柯坪—温宿凸起之间。区域构造格局上,这里是塔里木克拉通向西北自然延伸的部分。次凹北缘的阿合奇断裂是南天山造山带和塔里木克拉通的分界。乌什西次凹内发育与柯坪—温宿凸起相似的晚前寒武纪—古生代地层系统,包括寒武系、奥陶系和石炭系的烃源岩。新近系—第四系碎屑岩建造直接不整合于变形的古生代被动大陆边缘碎屑岩—碳酸盐岩沉积建造之上;剖面上,向南天山方向加厚,向塔里木克拉通方向减薄,呈现典型的前陆盆地剖面结构特征。这是一个晚新生代陆内前陆盆地,叠加在晚海西期—燕山期古隆起之上。这里的构造变形主要有3期,分别是中海西期、晚海西期—印支期和晚喜山期。变形以厚皮冲断构造及其相关褶皱为主,薄皮构造不发育。平面上,主构造线走向NE-SW。剖面上,以南天山向塔里木冲断为主。

塔里木盆地西缘西域组的底界、时代、成因与变形过程的初步研究

通过对塔里木盆地西缘代表性剖面的岩石地层和磁性地层研究 ,以多重地层划分概念为指导 ,讨论了西域组地层的内涵、外延及变形过程。西域组为一套冲洪积扇相深灰色巨厚层块状砾岩堆积。与下伏阿图什组河流相苍棕色粉砂岩、泥岩层呈整合接触。西域组的顶、底界均具有穿时特征 ,其地质年龄在不同地点是不一致的。与阿图什组相比 ,西域组的古水流方向、沉积物源、沉积相和沉积速率均发生了明显变化 ,这一变化及大面积西域砾岩的出现 ,代表了后陆的强烈隆升和剥蚀 ,但此时前陆盆地则未发生明显构造变形 ,以强烈沉陷和沉积为主。阿图什组 -西域组的强烈褶皱变形即西域运动的起止时间及变形强度在塔里木盆地不同地点可能是不同的 ,在盆地西北缘的博古孜河约为 1 6～ 1 0MaB .P .,盆地北缘的库车河剖面约为 2 58～ 1 5MaB .P .,盆地西南缘的叶城剖面约为 3 6～ 1 3MaB .P .。这表明塔里木盆地南北缘的晚新生代构造变形在时空上可能存在不均一性。

塔里木盆地西部喀什地区新生代褶皱冲断带构造解析

基于纵贯喀什地区4条地震剖面的精细构造解析,建立了喀什地区新生代褶皱冲断带的构造地质模型,认为该区新生代晚期不仅受南天山造山带南冲挤压的控制,也受到来自西昆仑的北冲推覆作用的影响,从而将喀什地区的冲断构造划分为北部的"南天山前陆冲断系统"(西段可称"阿图什前陆褶皱冲断带")和南部的"西昆仑前陆冲断系统"两部分。通过平衡恢复技术,定量计算了这两部分的最小水平构造缩短量分别为43.7 km和4 km,剖面总的缩短率为50%。综合构造演化序列和保存条件分析,认为北部深层成藏条件较好,优质储层是否发育是钻探成功的关键因素。

塔里木盆地西部巴什托普断裂的主要特征及其油气勘探意义

巴什托普断裂经历了两期变形。早期变形发生在中生代(或中生代末),沿中寒武统膏盐层发生的顺层滑动在上盘形成断层转折褶皱,之后发生冲断并伴有断层传播褶皱发育。由于南天山冲断带向南扩展(始自始新世晚期在中新世达到高潮)时该断裂带不活动,巴楚断隆南界的西段由中生代的巴什托普断裂北移至色力布亚断裂带。晚期变形发生在更新世,向南冲断,属西昆仑前陆褶皱冲断带中低级别的背冲断层。该地的生储盖条件较好,是相对的低应变区,因而是有利的油气勘探区。

塔里木盆地西部的新生代断裂活动

研究区以塔里木盆地西部的巴楚隆起为核心,包括其南侧的麦盖提斜坡和北侧的北部坳陷（阿瓦提凹陷）。这里新生代断裂异常发育。以鸟山-古董山地区为重点,通过精细的地震剖面解释,在塔里木盆地西部识别出5期新生代断裂活动,分别发生于：白垩纪末-古近纪初（ca.65Ma）、中新世末-上新世初（ca.5Ma）、上新世末-更新世中期（ca.3～1.5Ma）、更新世中-晚期（ca.1～0.1Ma）和全新世（ca.0.01Ma）。中寒武统和古近系膏盐层构成了研究区的2个主滑脱面。ca.65Ma的冲断受控于基墨里中间大陆与亚洲大陆碰撞的远程效应;ca.5Ma、ca.3～1.5Ma、ca.1～0.1Ma和ca.0.01Ma的断裂活动（包括滑脱断层、冲断层、走滑断层和正断层）均受控于印度-亚洲碰撞的远程效应。晚新生代（中新世以来）的断裂活动以脉动式冲断为特征,两次相邻脉动式冲断之间为时间不等的短暂的构造间歇期;间歇期构造平静,甚至可以形成正断层。

塔里木盆地下寒武统肖尔布拉克组北部台缘带展布及其油气勘探意义

礁滩型白云岩是世界范围内油气勘探开发效果最好的领域之一。塔里木盆地震旦—寒武系具备规模礁滩型白云岩发育基础,但其特征与分布研究基础十分薄弱。本文采用野外剖面观察、单井资料分析、地震资料刻画等手段,落实了柯坪—塔北西部存在下寒武统台缘带,命名为北部台缘带,该台缘带呈北东走向,长约330 km,宽约7 km。野外露头资料显示,下寒武统北部台缘带发育两期微生物礁,岩性以针孔状白云岩为主,溶蚀孔洞发育;地震剖面上,可见丘状前积反射特征。北部台缘带具有得天独厚的生储盖配置优势,位于长期继承性发育的古隆起之上,具备形成大油气田的有利条件。北部台缘带的展布特征为该区下古生界白云岩的区带评价及目标优选指明了方向。

塔里木盆地西部吐木休克断裂带的主要特征和构造演化

塔里木盆地西部的吐木休克断裂带是中央隆起(前身是晋宁期碰撞造山带)的次级单元巴楚断隆与北部坳陷的次级单元阿瓦提凹陷之间的分界。本文以大量的地质和地球物理证据,证明它是一条内部结构复杂且切穿地壳的深断裂。结合区域构造演化恢复了断裂发育史,指出它经历过三期重大的冲断活动,分别发生在加里东期、海西期和新近纪。新近纪的冲断与巴楚断隆的南界断裂带有相同的构造样式,可分为两幕:中新世的冲断受制于南天山前陆冲断带的向南扩展,更新世的冲断主要受制于西昆仑前陆冲断带的向北扩展。吐木休克断裂带的东西走向段和北西走向段的构造特征尚有若干差异,前者在加里东期活动较强,反映了构造的继承性;北西走向段则是加里东期出现的新生构造,在海西期进一步发展,更新世时因被卷入西昆仑的前陆冲断作用,表现出强烈而复杂的变形。

塔里木盆地西部鸟山地区断裂的主要特征和活动时代

基于一系列地震剖面解释,发现塔里木盆地西部东西向的鸟山深部断裂(及其北的罗斯塔格深部断裂)白垩纪发生向北的冲断,向下收敛于中—下寒武统膏盐层;鸟山浅部断裂更新世向北冲断,可延至全新世。鸟山东断裂主要在白垩纪发生右行剪切,与北西向的海米塔格深部断裂共同构成东西向冲断带中的变换构造带。鸟山北断裂中新世发生右行走滑,在北西向断裂的冲断活动中起了剪切变换作用。鸟山及邻区晚中生代以来的构造样式,可总结为2套不同方向的冲断系及与之配套的2套剪切变换系。据此认为该地区的油气前景不容乐观,并对断裂发育区的油气勘探提出了若干建议。

塔里木盆地西部康克林组沉积期沉积相及相模式

塔里木盆地西部石炭-二叠系发育具有良好油气勘探前景的生物礁滩体。在对塔西地区康克林组沉积期沉积体进行深入研究的基础上,详细分析了该区康克林组沉积期的岩性、岩相、沉积序列及相带的横向展布规律,建立了碳酸盐岩缓坡沉积模式。认为:塔西地区康克林组沉积期可划分出台地边缘礁滩、局限台地、潮坪3个沉积相带;塔西地区康克林组沉积早期与晚期具相异的沉积环境,区域相带的迁移特征反映了海平面升降变化和古地形对沉积格局的控制;康克林组沉积期礁滩体发育,横向上具良好的可对比性,分布范围广阔,是塔里木盆地西部重要的勘探目标层系之一。

塔里木盆地轮古西地区奥陶系断裂特征及其对油气富集的控制作用

针对塔里木盆地轮南古潜山轮古西地区奥陶系断裂解释存在的难点,利用最新的三维地震资料,结合区域构造背景,采用平面上参考相邻塔河地区的断裂发育规律,纵向上参考多层地震属性,对断裂进行了精细刻画和认识。结果表明:轮古西地区奥陶系断裂按形成时间分为中晚加里东期、海西期,按规模分为Ⅰ级、Ⅱ级、Ⅲ级;同时,断裂对潜山地貌、沟谷水系、岩溶储层具有重要的控制作用,进而影响油气的富集成藏;断裂对油气富集的控制作用主要表现在Ⅰ级及部分Ⅱ级断裂控制油气的垂向运移通道,并通过控制古地貌影响油气的平面优势运移方向,而Ⅲ级及另外部分Ⅱ级断裂通过影响岩溶作用进而控制着碳酸盐岩缝洞型储层的发育和分布。该认识对轮古西地区碳酸盐岩油气藏的勘探开发具有一定的指导意义。

塔里木盆地西部康克林组沉积期生物礁滩体——以柯坪地区苏巴什露头剖面为例

塔里木盆地西部石炭纪—二叠纪发育具有良好油气勘探前景的生物礁滩体。以柯坪小区苏巴什剖面中发育的康克林组为例,并结合麦盖提小区莎车县和什拉莆剖面、阿合奇小区阿克苏四石厂剖面,对生物礁滩体类型及特征做了深入的研究,在横向上对康克林组或相当于康克林组发育的礁滩体进行了详细的岩性、岩相对比研究,在此基础上建立了研究区礁滩发育的碳酸盐岩沉积模式。研究结果认为:(1)柯坪苏巴什剖面康克林组中发育的生物礁灰岩属于原生礁岩,为台地边缘和台内浅滩生物礁滩相带沉积,分布范围广阔;(2)塔西地区康克林组沉积早期与晚期具相异的沉积环境,区域相带的迁移特征反映了海平面升降变化和古地形对沉积格局的控制;(3)康克林组沉积期生物礁滩体在塔西地区广泛发育,横向上具良好的可对比性,是塔里木盆地西部重要的勘探目的层系之一。