Distribution, evolution and structural properties of Wushenqi paleo-uplift in Ordos Basin, NW China

This paper depicts the distribution of the Wushenqi paleo-uplift in the Ordos Basin by using the latest drilling and seismic data, and analyzes the tectonic evolution of the paleo-uplift with the support of Bischke curve and balanced section. The compressional Wushenqi paleo-uplift which developed in the Early Caledonian orogeny(Huaiyuan orogeny) is approximately a ellipse extending in S-N direction. Its long axis is about 194 km and short axis is about 55-94 km in nearly W-E direction. The denudation thickness and area of the Cambrian in the core are 170-196 m and 11 298 km^(2), respectively. It was mainly formed during the Huaiyuan orogeny according to the chronostratigraphic framework. It was in the embryonic stage in the Middle-Late Cambrian, denuded after developed obviously at the end of Late Cambrian. The paleo-uplift of the 3rd member of the Ordovician Majiagou Formation was reactivated and reduced in area. In the sedimentary period of the Ma 4 Member-pre-Carboniferous, the paleo-uplift experienced non-uniform uplift and denudation. It entered the stable period of burial and preservation in the Carboniferous and later period. The Wushenqi paleo-uplift was formed on the weak area of the basement and tectonic belts, into an compressional structure with irregular morphology, under the control of the non-coaxial compression in the south and north and the stress transmitted by the uplift in the basin. The Wushenqi paleo-uplift has a controlling effect on the sedimentary reservoirs and hydrocarbon accumulation.

Migration of paleo-uplift in southwestern Tarim Basin and its implications for orogenesis and reservoir development, NW China

Based on well horizon calibration,the typical seismic profiles in southwestern Tarim Basin were interpreted systematically,regional geological sections were established,and the regional denudation thickness of each tectonic period was restored.On this basis,the plane morphology maps of ancient structures of the Cambrian pre-salt dolomites in different periods were compiled,and the spatial distribution,development,evolution and migration of paleo-uplift in the late Early Paleozoic were analyzed.In the late Early Paleozoic,there existed a unified regional paleo-uplift widely distributed in southwestern Tarim Basin,which is called the southwestern Tarim plaeo-uplift.The“Tarim SW paleo-uplift”and“Hetian paleo-uplift”proposed in previous literatures are not independent,but the result of the spatio-temporal migration and evolution of the southwestern Tarim paleo-uplift identified in this paper.The southwestern Tarim paleo-uplift emerged at the end of Middle Ordovician,and took its initial shape with increased amplitude in the Late Ordovician.During the Silurian,the southwestern Tarim paleo-uplift rose steadily and expanded rapidly to the east,incorporating Pishan-Hetian and other areas,with the structural high locating in the Pishan-Hetian area.During the Devonian,the southwestern Tarim paleo-uplift began to shrink gradually,to a limited range in the Pishan-Hetian area in the southern part of the basin.During the Carboniferous,the southwestern Tarim paleo-uplift became an underwater uplift,that is,the paleo-uplift gradually died out.The southwestern Tarim paleo-uplift belongs to the forebulge of the southwestern Tarim foreland basin in the late Early Paleozoic,and its formation and evolution are related to the early Paleozoic orogeny of the West Kunlun orogenic belt in the south of the Tarim Basin.The migration of the southwestern Tarim paleo-uplift from the northwestern part of the southwestern Tarim Basin to the Pishan-Hetian area indicates the early Paleozoic orogenic process of the West Kunlun orogenic belt,which started in the western section at the end of Middle Ordovician and extended from west to east in a“scissor”style.The migration and evolution of the southwestern Tarim paleo-uplift controlled the development of unconformities at the end of Middle Ordovician,the end of Late Ordovician,and the end of Middle Devonian,and the spatial distribution of dissolved fracture-cave reservoirs in weathered crust below the unconformities in the southwest of Tarim Basin.The migration of the structural high of the southwestern Tarim paleo-uplift also played an important role in controlling the development of dissolved fracture-cave reservoirs in weathered crust.

Structural Characteristics and their Significance for Hydrocarbon Accumulation in the Northern Slope of the Central Sichuan Paleo-uplift

Based on 2D and 3D seismic data,the latest drilling data and field outcrop data of the northern slope of the Central Sichuan paleo-uplift,the structural analysis method is used to analyze unconformity development characteristics and fault characteristics during the key structural transformation period,discussing the influence of the structural characteristics on the hydrocarbon accumulation of deep carbonate rocks.The results show that:(1)The two key unconformities of the Tongwan and Caledonian periods were primarily developed in deep carbonate rocks.Firstly,Tongwan’s unconformities are characterized by regional disconformities between the second and third members of the Dengying Formation,the top formation of the Sinian and the lower Cambrian,strips of which zigzag through the north and south sides of the study area.Secondly,the Caledonian unconformity is characterized by a regional unconformable contact between the lower Permian and the ower Paleozoic strata.From NE to SW,the age of the strata,which were subject to erosion,changes from new to old,the denudation distribution showing as a nose-shaped structure which inclines towards the ENE.(2)Boundary fault and transtensional strike-slip faults developed in the Sinian to Paleozoic strata.In profile,there are three types of structural styles:steep and erect,flower structures,’Y’and reversed’Y’type faults.In plane view,the Sinian developed extensional boundary faults extending in an almost NS direction,strike-slip faults developing and extending linearly in approximately EW,WNW and NE strikes in the Cambrian,with characteristically more in the south and less in the north.(3)The faults in the northern slope show obvious zonal deformations in transverse view as well as significant stages and stratified activity in a longitudinal direction.Among them,the activity of faults in the Sinian was the strongest,followed by the activity in the Cambrian period,the activity intensity of faults in the Permian period being the weakest.This fault activity can be divided into four periods:Sinian,Cambrian-Permian,the early Indosinian period and the late Indosinian-Himalayan period,the transtensional strikeslip faults being the products of oblique extensions of pre-existing weak zones in the Xingkai and Emei taphrogenesis,with a particular inheritance in the main faults.(4)Combined with hydrocarbon accumulation factors,it is considered that the epigenetic karstification of the Tongwan and Caledonian unconformities in the northern slope controlled the formation and distribution of carbonate karst reservoirs over a large area,also acting as a good pathway for oil and gas migration.The extensional faults developed at the margin of the NS trending rift,controlling the sag-platform sedimentary pattern in the Dengying Formation of the Sinian.Strike-slip faults in NE,WNW and ENE directions may control the microgeomorphological pattern inside the platform and intensify the differential distribution of grain beach facies.The multi-stage hereditary activity of strike-slip faults not only improved the porosity and permeability of the reservoirs,but also acted as the main channel of oil and gas migration,providing favorable conditions for the development of the current multi-layer gasbearing scenario in the northern slope of the Central Sichuan Basin.

Structural patterns of fault damage zones in carbonate rocks and their influences on petroleum accumulation in Tazhong Paleo-uplift, Tarim Basin, NW China

Based on the outcrop survey,3D seismic data interpretation,drilling data analysis,the structural patterns and distribution of fault damage zones in carbonate strata of Tazhong Paleo-uplift were established to reveal the oil and gas enrichment law in the fault damage zones.The following findings were reached:(1)Through the filed survey,the fault damage zone system consists of fault core,damage zone with branch fault and fracture network.Affected by the active nature of the major faults,the fault damage zones differ in planar pattern and scale along the major faults.(2)3D seismic profiles reveal that there are three types of fault damage zones in carbonate strata in Tazhong paleo-uplift,strike-slip fault damage zones,thrust fault damage zones and superimposed fault damage zones.Featuring3 flowers and 3 root belts in vertical,the strike-slip fault damage zone can be subdivided into linear type,oblique type,feather type and horsetail type in plane.Thrust fault damage zones can be further divided into fault anticline type,anticline type and slope type.As the superimposition result of the above two kinds of fault damage zones,superimposed fault damage zones appear in three patterns,intersect type,encompassment type and penetrating type.(3)Cores from wells and geochemical data show oil and gas may migrate along the major fault and laterally.The feather type in strike-slip fault system,fault anticline type in thrust fault damage zone and intersect type in superimposed fault damage zone are possible sites for high production and efficiency wells.

Natural gas geology and exploration direction of the Cambrian Lower Canglangpu Member in central Sichuan paleo-uplift,Sichuan Basin,SW China

Based on drilling data of JT1 and CS1,outcrop profiles and seismic data,the sedimentary pattern,space configuration of source-reservoir-cap combinations and paleouplift evolution characteristics of the Cambrian Lower Canglangpu Member in the central Sichuan paleouplift have been investigated to determine the favorable exploration zones.Controlled by Deyang-Anyue rift,the Lower Canglangpu Member features differential characteristics from east to west in sedimentary framework.In the west side of the Deyang-Anyue rift,this member is composed of clastic sediments,while in the east side of the Deyang-Anyue rift,it is fresh water shelf sediments,with grain beaches occurring along edges of the depressions,shelf and lagoon.Among the beaches,the dolomitic ones are mainly distributed around the depression edge and in the north of the lagoon.The beach sediments could become high quality reservoirs under the effect of karstification.Underlying the Lower Canglangpu Member is the widespread source rock of the Qiongzhusi Formation,so oil and gas generated by the Qiongzhusi Formation source rock can directly charge into the beach reservoirs.The sandy mudstone of the Upper Canglangpu Member can serve as the caprock of the Lower Canglangpu Member reservoir.The dolomitic beaches are located at the higher part of the paleo-uplift during the main accumulation period,with good hydrocarbon accumulation elements.Blocks PT1-CS1,HT1-GT2 and east GT2 are favorable exploration zones.

鄂尔多斯盆地乌审旗古隆起的分布、演化及构造属性

基于最新钻井与地震资料,对鄂尔多斯盆地乌审旗古隆起的分布进行刻画,同时采用Bischke曲线、平衡剖面方法分析其形成演化。结果表明,乌审旗古隆起为加里东早期形成的挤压型古隆起,平面呈南北向展布的椭圆状,长轴约194 km,短轴近东西向,长55~94 km,核部寒武系被剥蚀的厚度与面积分别为170~196 m和11298 km^(2);利用年代地层格架剖面分析古隆起主体形成时间为怀远运动时期;中—晚寒武世为乌审旗隆起雏形期,晚寒武世末期隆起显著发育后被剥蚀,至奥陶纪马家沟组马三段沉积期隆起发生继承性活动,隆起面积减小,马四段沉积期—石炭系沉积前古隆起区地层发生非均一性抬升并遭受剥蚀,石炭纪及其之后进入埋藏保存的稳定期。乌审旗古隆起是在基底与构造薄弱带之上形成的,并受南部、北部的非共轴挤压以及盆内隆起传递的应力影响,发育成形态不规则的挤压型古隆起,该古隆起对沉积储集层和油气聚集具有一定控制作用。

鄂尔多斯盆地奥陶系盐下马家沟组四段天然气勘探突破及意义

鄂尔多斯盆地奥陶系马家沟组发育碳酸盐岩—膏盐岩共生体系沉积,马家沟组四段(马四段)是马家沟组沉积厚度最大的一套海侵碳酸盐岩沉积层,长期以来是天然气勘探关注的重点层位。基于地球物理、钻井岩心及有机地球化学等资料,重新认识了鄂尔多斯盆地奥陶系盐下古构造、储层分布、烃源岩和圈闭等成藏条件,并取得以下成果认识:(1)盐下马四段天然气为油型气,主要来自奥陶系盐下海相烃源岩,该套烃源岩生烃母质除常规干酪根外,还发育分散有机质、有机酸盐,生烃物质丰厚,具备规模生烃潜力;(2)奥陶纪鄂尔多斯盆地中东部坳陷存在乌审旗—靖边古隆起和东部盐下低隆两大次级构造单元,分别控制了盐下马四段台内滩、台内丘白云岩储层的发育,储集空间主要为白云岩晶间孔;(3)盆地中东部盐下马四段台内滩、台内丘白云岩上覆厚层膏盐岩封盖,上倾方向致密石灰岩侧向遮挡,海相烃源岩供烃,形成了大面积分布的自生自储式岩性气藏。在新的地质理论认识的指导下,针对鄂尔多斯盆地奥陶系盐下马四段部署的风险探井MT1井钻遇气层43.4m,采用水力加砂压裂新工艺,试气获35.24×10^(4)m^(3)/d的高产工业气流,实现了盆地战略接替领域的重大突破。

鄂尔多斯盆地乌审旗地区煤层气富集主控因素及其勘探方向

乌审旗地区是鄂尔多斯盆地的重要含煤区，也是近几年低煤阶煤层气勘探的热点地区。但该区前期煤层气钻探总体效果并不理想，迫切需要认清该区煤层气富集规律，以便有效开展煤层气勘探及开发利用。为此，对该区煤层分布特征、聚煤期沉积环境、煤岩特征及储层物性、煤层含气性等地质条件进行了分析，发现该区煤岩演化程度低，以低堞阶长焰煤为主，煤层厚5～30n3，大部分地区煤层埋深小于1000m且分布稳定，具有一定的煤层气勘探潜力。但煤层气钻井揭示该区煤层含气性变化大，煤层含气量介于0．19～6．7m^3／t，部分地区煤层气组成中CH4含量小于25％，说明煤层早期成岩时生成吸附的甲烷已被破坏逸散。进一步分析影响该区煤层气富集的主控因素后认为：在煤层直接盖层为砂岩、保存条件差的地区，煤层含气性差，反之，则含气性好，如果有后期生物气的补充，则可以富集成藏。最后指出：该区北部的乌审召区块和南部的纳林河区块，煤层气保存条件好、含气量高、勘探潜力大，可作为下一步煤层气勘探的有利目标区。

鄂尔多斯盆地乌审旗气田中二叠统下石盒子组盒8段下亚段滩坝砂体沉积特征

鄂尔多斯盆地乌审旗气田中二叠统下石盒子组盒8段下亚段中下部岩石为石英砂岩类砂岩,即“骆驼脖砂岩”,上部岩石为暗色粉砂质泥岩或碳质泥岩。“骆驼脖砂岩”广布于华北地台,在鄂尔多斯盆地呈“满盆砂”现象,是盆地的主要储层之一。以往学者多认为盒8段下亚段是河流相或三角洲相沉积。通过对众多取心井盒8段下亚段岩心的观察,结合对砂岩岩性、剖面结构、沉积构造、测井曲线特征及砂体空间展布规律的综合研究,提出了盒8段下亚段中下部是滩坝相沉积,上部是沼泽相或沼泽相为主夹小河道沉积。盒8段下亚段可发育一段或两段滩坝相石英砂岩类砂岩,其成分和结构成熟度较高,两段砂岩间夹若干米半深湖相的暗色粉砂质泥岩或沼泽相的碳质泥岩。发育<10°的冲洗交错层理、互成180°相交的板状和楔状层系组,具丘状和洼状交错层理的风暴岩。自然伽马曲线呈箱形或带齿的箱形。众多厚度较大的砂岩组成的若干列近东西向展布的长条透镜体状砂体,大致平行于古岸线。

RP-HPLC测定五参芪口服液中人参皂苷Rg1和人参皂苷Re的含量

目的：建立测定五参芪口服液（人参，黄芪，女贞子等）中人参皂苷Rg1和人参皂苷Re含量的反相高效液相色谱分析疗法。方法：色谱柱：Hypersil—C18（5μm，200mm×4．6mm I．D），柱温30℃，流动相为乙腈-0．05％磷酸水溶液（103：400），枪测波长203nm，流速1．0mL/min。结果：人参皂苷Rg1和人参皂苷Re分别在0．188～6．016μg（r=0．9999）和0．1976～6．3232beg（r=0．9999）范围内线性关系良好。平均叫收率分别为99．53％和99．13％。RSD分别为0．96％和0．62％。结论：本法操作简便、结果准确，重现性好，可用于五参芪口服液中人参皂苷Rg1和人参皂苷Re的含最测定。

陕甘宁盆地乌审旗气田上古生界高产控制因素研究

储层裂缝分布规律和单砂体时空展布特征是孔隙-裂缝型储层研究的重点,也是陕甘宁盆地上古生界中部气田获得高产的主要控制因素。通过研究作者认为,储层构造裂缝的发育与单砂体的岩性、厚度及储层所处的构造位置均有明显关系,鼻状构造高部位且岩性较粗的储层,裂缝最为发育。根据这一认识,作者对裂缝平面的分布规律进行了预测。同时文中在高精度、等时地层格架建立的基础上,从储层沉积相和沉积微相入手,研究了单砂体的展布规律和储集性能的时空变化,并对有效储层的分布进行了预测。

New understandings on gas accumulation and major exploration breakthroughs in subsalt Ma 4 Member of Ordovician Majiagou Formation,Ordos Basin,NW China

Geological conditions and main controlling factors of gas accumulation in subsalt Ma 4 Member of Ordovician Majiagou Formation are examined based on large amounts of drilling,logging and seismic data.The new understandings on the control of paleo-uplift over facies,reservoirs and accumulations are reached:(1)During the sedimentary period of Majiagou Formation,the central paleo-uplift divided the North China Sea in central-eastern of the basin from the Qinqi Sea at southwest margin of the basin,and controlled the deposition of the thick hummocky grain beach facies dolomite on platform margin of Ma 4 Member.Under the influence of the evolution of the central paleo-uplift,the frame of two uplifts alternate with two sags was formed in the central-eastern part of the basin,dolomite of inner-platform beach facies developed in the underwater low-uplift zones,and marl developed in the low-lying areas between uplifts.(2)From the central paleo-uplift to the east margin of the basin,the dolomite in the Ma 4 Member gradually becomes thinner and turns into limestone.The lateral sealing of the limestone sedimentary facies transition zone gives rise to a large dolomite lithological trap.(3)During the late Caledonian,the basin was uplifted as a whole,and the central paleo-uplift was exposed and denuded to various degrees;high-quality Upper Paleozoic Carboniferous-Permian coal measures source rocks deposited on the paleo-uplift in an area of 60000 km^(2),providing large-scale hydrocarbon for the dolomite lithological traps in the underlying Ma 4 Member.(4)During the Indosinian-Yanshanian stage,the basin tilted westwards,and central paleo-uplift depressed into an efficient hydrocarbon supply window.The gas from the Upper Paleozoic source rock migrated through the high porosity and permeability dolomite in the central paleo-uplift to and accumulated in the updip high part;meanwhile,the subsalt marine source rock supplied gas through the Caledonian faults and micro-fractures as a significant supplementary.Under the guidance of the above new understandings,two favorable exploration areas in the Ma 4 Member in the central-eastern basin were sorted out.Two risk exploration wells were deployed,both revealed thick gas-bearing layer in Ma 4 Member,and one of them tapped high production gas flow.The study has brought a historic breakthrough in the gas exploration of subsalt Ma 4 Member of Ordovician,and opened up a new frontier of gas exploration in the Ordos Basin.

Distribution and exploration direction of medium-and large-sized marine carbonate gas fields in Sichuan Basin, SW China

Based on the analysis of the basic characteristics of medium-and large-sized marine gas fields in Sichuan Basin, combined with the division of major reservoir forming geological units in the marine craton stage and their control on key hydrocarbon accumulation factors, the distribution law of medium-and large-sized marine carbonate gas fields in the basin was examined and the exploration direction was pointed out. Through the analysis of the periodic stretching-uplifting background, it is concluded that five large scale paleo-rifts, three large scale paleo-uplifts, five large scale paleo erosion surfaces were formed in the marine craton stage of Sichuan Basin, and these geological units control the key reservoir forming factors of medium and large sized gas fields:(1) Large-scale paleo-rifts control the distribution of high-quality hydrocarbon generation centers.(2) The margin of large-scale paleo-rifts, high position of paleo-uplifts and paleo erosion surfaces control the distribution of high-quality reservoirs.(3) Large-scale paleo-rifts, paleo-uplifts, paleo erosion surfaces and present tectonic setting jointly control the formation of many types of large and medium-sized traps.(4) Natural gas accumulation is controlled by the inheritance evolution of traps in large geological units. Based on the comparative analysis of the distribution characteristics of medium-and large-sized gas fields and large geological units, it is proposed that the superimposition relationship between single or multiple geological units and the present structure controls the distribution of medium-and large-sized gas fields, and the "three paleo" superimposed area is the most advantageous. According to the above rules, the main exploration fields and directions of medium-and large-sized marine carbonate gas fields in Sichuan Basin include periphery of Deyang-Anyue paleo-rift, eastern margin of Longmenshan paleo-rift, margins of Kaijiang-Liangping oceanic trough and Chengkou-western Hubei oceanic trough, the high part of the subaqueous paleo-uplifts around Central Sichuan, paleo erosion surfaces of the top boundary of Maokou Formation in eastern and southern Sichuan Basin, paleo erosion surfaces of the top boundary of the Leikoupo Formation in central and western Sichuan Basin.

The dating and temperature measurement technologies for carbonate minerals and their application in hydrocarbon accumulation research in the paleouplift in central Sichuan Basin, SW China

A new method for reconstructing the geological history of hydrocarbon accumulation is developed, which are constrained by U-Pb isotope age and clumped isotope((35)47) temperature of host minerals of hydrocarbon-bearing inclusions. For constraining the time and depth of hydrocarbon accumulation by the laser in-situ U-Pb isotope age and clumped isotope temperature, there are two key steps:(1) Investigating feature, abundance and distribution patterns of liquid and gaseous hydrocarbon inclusions with optical microscopes.(2) Dating laser in-situ U-Pb isotope age and measuring clumped isotope temperature of the host minerals of hydrocarbon inclusions. These technologies have been applied for studying the stages of hydrocarbon accumulation in the Sinian Dengying gas reservoir in the paleo-uplift of the central Sichuan Basin. By dating the U-Pb isotope age and measuring the temperature of clumped isotope((35)47) of the host minerals of hydrocarbon inclusions in dolomite, three stages of hydrocarbon accumulation were identified:(1) Late Silurian: the first stage of oil accumulation at(416±23) Ma.(2) Late Permian to Early Triassic: the second stage of oil accumulation between(248±27) Ma and(246.3±1.5) Ma.(3) Yanshan to Himalayan period: gas accumulation between(115±69) Ma and(41±10) Ma. The reconstructed hydrocarbon accumulation history of the Dengying gas reservoir in the paleo-uplift of the central Sichuan Basin is highly consistent with the tectonic-burial history, basin thermal history and hydrocarbon generation history, indicating that the new method is a reliable way for reconstructing the hydrocarbon accumulation history.

Cenozoic structural deformation in the Yuqia-Jiulongshan region, northern Qaidam Basin, China

Based on field geological survey, interpretation of seismic reflection profile and thermochronology dating, this paper systematically studied the structural deformation of the Yuqia-Jiulongshan region in northern Qaidam Basin during the Cenozoic. The results show that the area is primarily dominated by a large box-shaped anticline, with steep limbs and a wide and gently-deformed core. The Mahaigaxiu and Jiulongshan anticlines are secondary folds controlled by secondary faults in the limbs of the box-shaped anticline. Whereas the Yuqia and the Northern Yuqia anticlines are secondary folds within the wide core of the box-shaped anticline. The geometry of the box-shaped anticline is mainly controlled by some high-angle reverse faults with certain right-lateral strike-slip components, displaying distinct positive flower structures in section view. Combining the sedimentary correlation and detrital apatite fission track analysis, we believe that the Yuqia-Jiulongshan region was a paleo-uplift that developed slightly in the early Cenozoic, resulting in the relatively thin Cenozoic strata. The intense deformation that shaped the present-day structural framework occurred in or after the sedimentary period of Shizigou Formation. The Yuqia – Jiulongshan paleo-uplift is adjacent to the Sainan depression that is rich in Lower-Middle Jurassic source rocks, and thus has high potential for future hydrocarbon exploration.

The formation and evolution of Chepaizi-Mosuowan paleo-uplift and its control on the distributions of sedimentary facies in the Junggar Basin

The Chepaizi-Mosuowan paleo-uplift is a large-scale uplift stretching across the Junggar Basin formed during the Yanshanian. It has experienced four evolutionary stages: the initial forming stage (J1), the intense development stage (J2+3), the waning and burial stage (K-E), and the tilting and extinction stage (N-Q). The most intense period of activities is the Middle Jurassic. Dur-ing the Early Jurassic, the Chepaizi-Mosuowan paleo-structure was a low amplitude uplift. Because of the subsequent strong uplifting during Middle-Late Jurassic, the Middle and Upper Jurassic were eroded. With the evolution of the Chepaizi-Mosuowan paleo-uplift, the sedimentary pattern of the basin changed, and the paleo-uplift separated the northern depositional systems from those in the south side. As a result, the basin tectonics controlled the distribution and evolution of the depositional systems. During Early Jurassic, while the paleo-uplift was low, its controlling effect on depositional systems was limited and sediments coming from the northwest could reach the central and southern parts of the basin. With the strong uplifting of the Chepaizi-Mosuowan paleo-structure during Middle-Late Jurassic, sediments from the northwest provenance could only deposit in the northern graben of the paleo-uplift. The intense erosion of the Middle-Upper Jurassic also changed the former sedimentary center of the basin into a source area, supplying sediments for grabens on both sides of the paleo-uplift. In the Cretaceous, regional subsidence caused the paleo-uplift to be buried again and subsequently sediments accumulated on top of it. The depositional facies are dominated by fluvial in the Early Cretaceous and shallow lacustrine to deltaic in the Late Cretaceous. In the history of the long-lasting development of this paleo-uplift, large-scale erosions of the paleohigh not only provided sufficient sediments to the center of the Junggar Basin, but also created favorable conditions for the formation of various subtle traps such as lithologic and stratigraphic traps.

Temporal and Spatial Evolution Analysis:The Early Paleozoic Paleo-Uplifts in the Tarim Basin

ABSTRACT： Twenty unconformities, primarily superimposed types, were identified based on inter pretation of a 46 000 km seismic profile combined with data from over 40 drilling wells. These respec tively correspond to the main tectonic evolution stages and the boundaries between those stages. Re construction of the original depths of eroded strata was conducted for the Middle Caledonian, Early Hercynian, Late Hercynian, Indosinian, Early Yanshanian and Late Yanshanian unconformities using the virtual extrapolation of seismic reflection. Eroded strata thicknesses were also calculated for indi vidual periods and intervals. Based on the reconstructed data, in combination with data from research on sedimentary facies, a paleogeomorphological profile was constructed for different tectonic evolution stages of the basin during the Early Paleozoic. The profile indicates the presence of obvious regularity in the temporal and spatial evolution of these unconformities. Based on the characteristics of paleouplift evolution and postlayering reconstruction, the paleouplifts were divided into inherited （e.g., Tazhong （塔中）, residual （e.g., North Tarim） and active （e.g., Southwest Tarim and Bachu （巴楚） types. The huge North Tarim uplift represents a typical form of residual paleouplift. The Paleozoic strata in the upper layers of the uplift is in poor condition for reservoir accumulation and preservation; however, the Upper MesozoicCenozoic structural layer can form a secondary reservoir that is rela tively rich in oil and gas. Furthermore, the flank slope area of the uplift is always a key source for oil and gas collection and the most advantageous position for the formation of the original reservoir. The Tazhong paleouplift has been stable since its formation in the Late Ordovician, where petroleum accumulation has been distributed not only in the uplift, but also in the deep and slope belts of the uplift. Important breakthroughs in petroleum exploration of the slope break in the North Tazhong area datingback to the Paleozoic have further confirmed the enrichment of oil and gas in this type of uplift. The Southwest Tarim paleouplift is a buried type, which has given it favorable properties for hydrocarbon migration over a long time. An open question is whether the large amount of oil and gas accumulated here was transported to the current Bachu uplift.

Controlling factors of Dengying Formation reservoirs in the central Sichuan paleo-uplift

Macroscopic and microscopic characteristics revealed that the Dengying Formation reservoir in the central Sichuan paleo-uplift belonged to the compound genetic reservoir of the mound-shoal facies and karst.Development of the reservoir was controlled by the mound-shoal facies,and dissolution-enlarged or added pores(vugs)due to superimposed karstification modification were favorable reservoir spaces.The karst of the Dengying Formation in Tongwan stage was the stratabound-weathered crust karst of the early diagenesis stage,the extensive superimposition of mound-shoal facies and regional karstification in the central Sichuan paleo-uplift area was the key to develop the large-scale continuous Dengying Formation reservoirs.Due to differences in the development degree of mound-shoal facies and in the intensity of karst modification,the reservoir development degree varied in different zones in the paleouplift area.The NS-extending zone on the western side of the Gaoshiti-Moxi area was the sweet spot for reservoir development.Effective identification of mound-shoal facies and fine depiction of karst landform was the key for reservoir prediction of the Dengying Formation to discovery the superimposed area of the mound-shoal facies and the karst monadnock-karst steep slope which similar to Moxi-Gaoshiti area.