Lead isotope geochemical characteristics of Pb-Zn-Cu deposits on the southwestern margin of Tarim,and their significance

The polymetallic(Pb,Zn,Cu,etc) ore belt on the southwestern margin of Tarim is one of the major regions with the greatest prospecting potential in Xinjiang.Reported in this paper are the lead isotope data for 66 sulfide samples(including 50 galena samples,15 chalcopyrite samples and 1 pyrite sample) collected from such representative deposits as Tamu,Tiekelike,Kalangu,Abalieke,etc.in this ore belt.The Pb isotopic ratios of 206 Pb/204 Pb,207 Pb/204 Pb and 208 Pb/204 Pb in the galena samples range from 17.931 to 18.176,15.609 to 15.818 and 38.197 to 38.944,with the average values of 18.017,15.684 and 38.462,respectively.Those in the chalcopyrite samples range from 17.926 to 18.144,15.598 to 15.628 and 38.171 to 38.583,with the average values of 18.020,15.606 and 38.262,respectively.The pyrite sample has the Pb isotopic ratios of 206 Pb/204 Pb,207 Pb/204 Pb and 208 Pb/204 Pb to be 17.980,15.604 and 38.145,respectively.In combination with the previous Pb isotope data for sulfides,it is found that there is only a slight variation in the Pb isotopic composition of galena,chalcopyrite,sphalerite and pyrite in the ore belt.However,there is some difference in Pb isotopic characteristics between galena and chalcopyrite,especially the Pb isotopic composition of galena shows an obvious linear correlation with some other relevant parameters(e.g.β and γ).The comprehensive analysis suggested that lead in galena(maybe including sphalerite and pyrite) was derived principally from wall rocks and underlying basement,and that in chalcopyrite only originated from the basement.The single-stage model ages of these sulfides couldn't indicate the time limit of metallogenesis(Pb,Zn,Cu,etc.),and the positive linear correlations for the Pb isotopic composition of galena are of no single-stage and two-stage Pb-Pb isochron significance.Furthermore,there are significant differences in Pb isotopic composition characteristics between the genetic type of deposits in this polymetallic ore belt and the Mississippi Valley type(MVT).In addition,the authors also pointed out that there is a phenomenon of differentiation(not paragenesis) for lead and copper elements during the process of metallogenesis in this ore belt.

Types of the Cambrian platform margin mound-shoal complexes and their relationship with paleogeomorphology in Gucheng area,Tarim Basin,NW China

Based on the observation of outcrops and cores,thin section identification,restoration of paleogeomorphology by residual thickness method,fine description of seismic facies,etc.,the coupling relationships between the development patterns of various types of Cambrian platform margin mound-shoal complexes and paleogeomorphology in the Gucheng area of Tarim Basin have been examined.The Cambrian platform margin mound-shoal complex is divided into mound base,mound core,mound front,mound back and mound flat microfacies,which are composed of dolomites of seven textures with facies indication.The different paleogeomorphology before the deposition of mound-shoal complex in each period was reconstructed,and three types of mound-shoal complex sedimentary models corresponding to the paleogeomorphologies of four stages were established:namely,the first stage of gentle slope symmetric accretion type,the second stage of steep slope asymmetric accretion type and the third and fourth stages of steep slope asymmetric progradation type.Their microfacies are respectively characterized by-mound base-mound back+(small)mound core+mound front-mound flat"symmetric vertical accretion structure,"mound base-(large)mound core+mound front-mound flat"asymmetric vertical accretion structure,"mound base-(small)mound core+mound front-mound flat"asymmetric lateral progradation structure.With most developed favorable reservoir facies belt,the steep slope asymmetric accretion type mound-shoal complex with the characteristics of"large mound and large shoal"is the exploration target for oil and gas reservoir.

THE SEQUENCE OF PALEOENVIRONMENTAL CHANGES SINCE ABOUT 4KA B.P., RECORDED BY NIYA SECTION IN SOUTHERN MARGIN OF TARIM BASIN

Through synthetic researches of multi-index geological records of Niya section, which are of high resolution in southern margin of Tarim Basin, this paper has reconstructed the sequences of paleoclimate in this region during historical times (since about 4000a B.P.). During the last 4000 years, the area has experienced alternations of relative cold-moisture and relative warm-dry periods. Three evident cold-moisture periods and three warm-dry periods are identifing. The study shows that the human activities have an intimate relation with the evolution of paleoclimate in the southern Xinjiang. Paleoclimate has played very important role in influencing human being′s agricultural activities.

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.

Distribution of Nanhua-Sinian rifts and proto-type basin evolution in southwestern Tarim Basin, NW China

Based on seismic data,outcrop evidence,logging data and regional aeromagnetic data,the distribution of Nanhua–Sinian rifts in the southwestern Tarim Basin was analyzed,and on the basis of restoration of lithofacies paleogeography in different periods of Neoproterozoic–Cambrian,the evolution model of the proto-type rift basin was discussed.The Neoproterozoic Rodinia supercontinent split event formed the trigeminal rift system at the edge and inside of the craton in the southwestern Tarim Basin located in the Kunlun piedmont and Maigaiti slope.The rift in Kunlun piedmont zone was distributed along the E-W direction and was the oceanic rift in the trigeminal rift system.Two decadent rifts in N-E strike developed in the Luonan and Yubei areas of Maigaiti slope,and the interior of the rifts were characterized by a composite graben-horst structure composed of multiple grabens and horsts.The Neoproterozoic–Cambrian proto-type basin evolution in the southwestern Tarim Basin can be divided into three stages:rift in the Nanhua,embryonic passive continental margin in the Sinian,and stable passive continental margin in the Cambrian.Despite the regional tectonic movements in the end of Nanhua and Sinian,the tectonic framework of the southwestern Tarim Basin had not changed significantly,the sedimentary center of Nanhua rift basin showed the characteristics of succession in the Sinian–Early Cambrian.The Nanhua rift in Kunlun piedmont evolved into a craton marginal depression during the Sinian–Early Paleozoic,while the Luonan decadent rift in the midsection of Maigaiti slope evolved into a sag inside platform in Early Cambrian,constituting the paleogeographic framework of"two paleouplifts and one sag"with the paleouplifts in east and west sides of the slope.The later evolution of the Luonan decadent rift in the midsection of the Maigaiti slope formed two sets of reservoir-forming assemblages,the Sinian and the Lower Cambrian ones,which are important exploration targets in future.

Determining the Main Gas-generation Phase of Marine Organic Matters in Different Occurrence States using the Kinetic Method

This paper probes the determination of the main gas-generation phase of marine organic mattes using the kinetic method. The main gas-generation phase of marine organic matters was determined by coupling the gas generation yields and rates in geological history computed by the acquired kinetic parameters of typical marine organic matters （reservoir oil, residual bitumen, lowmaturity kerogen and residual kerogen） in both China and abroad and maturity by the EasyRo（%） method. Here, the main gas-generation phase was determined as Ro%=1.4%-2.4% for type Ⅰ kerogen, Ro%=1.5-3.0% for low-maturity type Ⅱ kerogen, Ro%=1.4-2.8% for residual kerogen, Ro%=1.5-3.2% for residual bitumen and Ro%=1.6-3.2% for reservoir oil cracking. The influences on the main gas-generation phase from the openness of the simulated system and the ＂dead line＂ of natural gas generation are also discussed. The results indicate that the openness of simulation system has a definite influence on computing the main gas-generation phase. The main gas-generation phase of type Ⅱ kerogen is Ro%=1.4-3.1% in an open system, which is earlier than that in a closed system. According to our results, the ＂dead line＂ of natural gas generation is determined as Ro=3.5 % for type Ⅰ kerogen, Ro=4.4-4.5% for type Ⅱ kerogen and Ro=4.6% for marine oil. Preliminary applications are presented taking the southwestern Tarim Basin as an example.

Types,structural evolution difference and petroleum geological significance of Cambrian-Ordovician carbonate platforms in Gucheng-Xiaotang area,Tarim Basin,NW China

Based on the latest drilling cores,thin sections,and 3D seismic data,types,features,and evolution processes of Cambrian-Ordovician carbonate platforms in the Gucheng and Xiaotang areas are studied,and favorable exploration zones in this area are also discussed.There are two types of carbonate platforms developed in the Cambrian-Ordovician in the Gucheng-Xiaotang area,namely,carbonate ramp and rimmed platforms,and the evolution process of the platform in the Gucheng area is different from that in Xiaotang area.In the Early Cambrian,the study area was a homoclinal carbonate ramp.During the Middle to Late Cambrian,it evolved into a rimmed platform,with 5 phases of mound shoals developed.In the southern area,mound shoals were in progradational arrangement and the third and fourth stages of mound shoals suffering exposure and further developed abundant karst vugs.In the northern area,the mound shoals appeared in a superposition of aggradation-weak progradation,the third,fourth,and fifth stages of mound shoals suffered exposure and dissolution,and the platform slope developed gravity flow deposits.In the Early to Middle Ordovician,the southern area gradually evolved into a distally steepened carbonate ramp,where retrogradational dolomitic shoal developed;while the northern part experienced an evolution process from a weakly rimmed platform to a distally steepened carbonate ramp,and developed two or three stages of retrogradational mound shoals.The high-frequency oscillation of sea level and local exposure and dissolution were beneficial to the formation of mound or shoal reservoirs in platform margin and ramp,and the configuration of these reservoirs with low energy slope-basin facies source rocks could form good oil-gas enrichment zones.The dolomitic shoal in the Ordovician platform ramp is the practical exploration field for increasing reserve and production in the Gucheng area.The mound shoal at the Cambrian rimmed platform margin is the key exploration object in the Xiaotang area.In addition,the Cambrian slope gravity flow deposits can be taken as the favorable exploration fields in the study area.

The U-Pb chronologic evidence and sedimentary responses of Silurian tectonic activities at northeastern margin of Tarim Basin

U-Pb ages of Devonian detrital zircons from Tabei Uplift have been determined through LA-ICP-MS test technology.The results revealed that most zircon ages concentrate on 460-414 Ma,especially around 436-423 Ma,indicating possible occurrences of strong tectonic events at the northern margin of Tarim Basin during that period.Combined with previous researches on the basin marginal orogenic belts,intense tectonic activities developed at the northeast margin of Tarim Basin and its obvious sedimentary responses in basin during the end of Ordovician to Early-Middle Silurian are discussed.These include(1) several unconformities within the Late Ordovician-Silurian,showing truncation,erosion,and onlap characteristics,which reflected the local uplift formed during the surrounding extrusion process;(2) the Silurian fluvial delta system from northeast to southwest in Keping,Yingmaili,Hade,and Caohu areas,which reflected the partial uplift at the northeast margin and provided clastic supply to basin;and(3) as indicated by heavy mineral analysis,the Silurian sediments came mainly from the recycles of orogenic belts provenance,which indicated the compress tectonic setting.In addition,a wide range of red mudstone layer distribution in the upper part of the Silurian may be closely related to the surrounding tectonic uplift and the rapid decline of sea levels.

Deep structure at northern margin of Tarim Basin

In this paper, a 2D velocity structure of the crust and the upper mantle of the northern margin of the Tarim Basin (TB) has been obtained by ray tracing and theoretical seismogram calculation under the condition of 2D lateral inhomogeneous medium using the data of seismic wide angle reflection/refraction profile from Baicheng to Da Qaidam crossing the Kuqa Depression (KD) and Tabei Uplift (TU). And along the Baicheng to Da Qaidam profile, 4 of the 10 shot points are located in the northern margin of the TB. The results show that the character of the crust is uniform on the whole between the KD and TU, but the depth of the layers, thickness of the crust and the velocity obviously vary along the profile. Thereinto, the variation of the crust thickness mainly occurs in the middle and lower crust. The Moho has an uplifting trend near the Baicheng shot point in KD and Luntai shot point in TU, and the thickness of the crust reduces to 42 km and 47 km in these two areas, respectively. The transition zone between the KD and TU has a thickest crust, up to 52 km. In this transition zone, there are high velocity anoma-lies in the upper crust, and low velocity anomalies in the lower crust, these velocity anomalies zone is near vertical, and the sediment above them is thicker than the other areas. According to the velocity distributions, the profile can be divided into three sections:KD, TU and transition zone between them. Each section has a special velocity structural feature, the form of the crystalline basement and the relationship between the deep structure and the shallow one. The differences of velocity and tectonic between eastern and western profile in the northern margin of the Tarim Basin (NMTB) may suggest different speed and intensity of the subduction from the Tarim basin to the Tianshan orogenic belt (TOB).

Petrography and tectonic provenance of the Permian Tunas Formation:Implications on the paleotectonic setting during the ClaromecóForeland Basin evolution,southwestern Gondwana margin,Argentina

The Claromec o Basin is located at the south-western sector of the Buenos Aires province,Argentina.This basin is considered a foreland basin closely related to the evolution of the southwestern Gondwana margin.This contribution focuses on the provenance analysis of the Tunas Formation(Permian,Pillahuinc o Group),which represents the last filling stage for the Claromec o Foreland Basin.Petrographic and tectonic provenance analyses were performed in sandstones recovered from subsurface(PANG 0001 and PANG0003 exploration wells)and outcrops located close to the basin center(Gonzales Chaves locality).In the subsurface,the analyzed succession is composed of medium-to fine-grained sandstones interbedded with tuffs,mudrocks,carbonaceous mudrocks and coal beds.In outcrops,the succession is dominated by mediumto fine-grained sandstones interbedded with siltstones.Modal composition patterns are distributed into the recycled orogen and transitionally recycled to mixed fields.Petrographic analyses,in addition to provenance and sedimentological studies,confirm that sedimentary material was derived from a mixed source,which largely comes from the Sierras Australes fold and thrust belt,located towards the W-SW,where the sedimentary succession is interbedded with volcanic material.The Tunas Formation shows clear differences in its modal composition,paleocurrent direction and paleoenvironmental conditions with respect to the underlying units of the Pillahuinc o Group(Sauce Grande,Piedra Azul and Bonete formations).Source areas changed from cratonic to mixed fold belt/arc-derived material,suggesting variations in the Claromec o Basin configuration during the Late Paleozoic.Changes in the paleotectonic scenario during the deposition of the Tunas Formation have been interpreted as a consequence of a compressive post-collisional deformation event,the product of adjustment,accommodation and translation of terrains towards the equator during the Permian-Triassic to form Pangea.

塔里木盆地西南部寒武系充填层序及沉积样式演化

针对塔里木盆地西南部寒武系存在的古隆起陆棚相分歧,利用锆石U-Pb(铀-铅同位素测年)年龄、井-震联合开展了寒武系层序充填与沉积演化的研究。研究表明:在巴楚隆起,寒武系直接覆盖在克拉通结晶基底之上,寒武系沉积充填与前寒武系结构呈“镜像”关系。受前寒武系地形、构造运动和海平面升降控制,塔里木盆地西南部寒武系发育4个Ⅱ级层序,分别为寒武系层序1(玉尔吐斯组—肖尔布拉克组)、寒武系层序2(吾松格尔组—沙依里克组)、寒武系层序3(阿瓦塔格组)、寒武系层序4(下丘里塔格群),共包含7个沉积相、10个沉积亚相。塔里木盆地西南部寒武系层序1—寒武系层序3早、中寒武世巴楚隆起—麦盖提斜坡—塔西南坳陷沉积相为台地—缓坡—斜坡—深水陆棚相沉积,表现为向海凝缩减薄的沉积特征并发育寒武系烃源岩;寒武系层序4晚寒武世塔里木盆地西南部主体演化为局限台地,塔里木盆地西台东盆沉积格局正式形成。

塔西南山前地区柯克亚周缘叶探1井油气勘探重大突破及意义

塔西南山前西昆仑冲断带柯东构造带叶探1井在二叠系普斯格组获得重大突破,标志着塔西南山前地区发现一个重要的勘探接替层系。结合区域地质资料,根据野外露头、钻井、地震等综合研究,对柯克亚周缘二叠系普斯格组的成藏条件进行再认识。研究认为,研究区内二叠系普斯格组发育陆相湖泊—三角洲沉积体系,上段发育半深湖—深湖相烃源岩,面积1.0×10^(4)km^(2),厚度最大达到800m,集中段有机质丰度为0.92%~1.16%,以菌藻类生源为主,有机质类型主要为Ⅱ型,有机质丰度高;普斯格组下段发育三角洲前缘、滨浅湖沙坝优质砂岩储层,砂体厚度为42.5~63m,砂地比为27%~47%,是一套分布较广的区域性储层,与普斯格组上段泥岩组成优质储盖组合;柯克亚周缘发育印支期、喜马拉雅期两期构造变形,古生界叠瓦冲断、强烈逆掩叠置,圈闭成排成带,喜马拉雅期进一步挤压抬升改造,局部复杂化,形成的叠瓦冲断带为勘探有利区。根据普斯格组天然气干燥系数分析,折算Ro为1.31%~1.42%,与下盘烃源岩成熟度相当,表明油气来自下盘逆掩叠置烃源岩,经历早油晚气的成藏过程,成藏具有“逆掩叠置下盘供烃、下生上储、断裂输导”的特点。综合分析认为该地区二叠系普斯格组圈闭成排成带分布,已发现圈闭9个,面积301km^(2),天然气资源量约为2930×10^(8)m^(3),凝析油资源量约为2×10^(8)t,具有较好的勘探前景。

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。

塔里木盆地西南部晚白垩世——早古新世沉积环境演化:来自皮山PBX1井的地化证据

【研究目的】白垩纪与古近纪之交发生过地质历史上重大的灾变和异常事件,致使K/Pg界线成为全球最重要的地质界线之一。通过对塔里木盆地晚白垩世—早古新世沉积环境的研究,有助于重建特提斯北部盆地群塔里木盆地的古环境。【研究方法】本文通过塔里木盆地西南部PBX1井岩心的地球化学元素敏感指标研究K/Pg上下环境的变化。【研究结果】晚白垩世晚期古气候属于干热型,早古新世呈现短暂温湿型。古盐度由晚白垩世正常海洋环境向早古新世半咸水、海陆过渡盐湖环境转换,K/Pg界线位置处,古盐度达到最低值。氧化-还原环境由晚白垩世富氧→贫氧的弱氧化-弱还原环境经历了K/Pg事件之后短暂向早古新世富氧环境转化,而后整体上由贫氧的弱氧化-弱还原环境向极贫氧的还原环境演化。【结论】PBX1井地球化学元素敏感指标揭示了中生代—新生代之交灾变异常事件在塔里木盆地响应特征,也是特提斯洋北部盆地群晚白垩世—早古新世沉积环境演化的有效证据。

塔里木盆地西北缘克孜勒布拉克南沟乌拉尔统巴立克立克组生物礁地质特征

塔里木盆地西北缘二叠系巴立克立克组广泛发育具有油气勘探意义的巨厚台地边缘生物礁,本文对塔西北克孜勒布拉克南沟出露的典型的二叠系巴立克立克组生物礁进行了详细的宏微观研究。该套生物礁以生屑滩为礁基,礁核下部主要为蓝绿藻建造的各类微生物岩,其结构组分主要为凝块及破碎的微凝块,次为叠层石,此时的水体能量较低;礁核上部局部发育叶状藻礁,并伴生大量的海生底栖动物,此时礁体开始暴露在浪基面之上,大量发育角砾状灰岩,并遭受大气淡水岩溶的改造。除了台缘带外,塔西北柯坪地区同期的局限台地中也发育小规模的、具微生物岩特征的台内礁滩体,说明该时期区域上的环境条件普遍适宜造礁。巴立克立克组的该套礁滩体的形成时间为乌拉尔世阿瑟尔期晚期—萨克马尔期,这与乌拉尔世塔里木大火成岩省早期阶段相当,因此,推测该套礁滩体的形成和当时的火山活动产生的火山灰导致南天山洋残余海盆的海水“富营养化”有关。藻类的爆发使得巴立克立克组礁滩体的δ^(13)C值较之康克林组的碳酸盐岩呈现显著正偏移。但是,巴立克立克组的礁滩体受胶结作用等建设性成岩作用的改造程度较深,利于“成岩”,不利“成储”,使得区域上巴立克立克组的礁滩体尽管相带较好,但储渗性极差,唯有受构造裂缝改造部分可发育高渗层。因此,可以确定:塔西北乌拉尔世巴立克立克组的礁滩储层基本不受相控,主要发育裂缝型储层。因此,今后对于塔西北二叠系礁滩油气藏的勘探应重点关注构造裂缝发育段。本研究对今后塔西北巴立克立克组生物礁优质储层预测提供了科学依据,对于我国乃至世界范围内二叠系微生物岩的研究也有一定助益。

塔里木盆地塔西南山前带地震技术攻关进展及发展方向

塔里木盆地西南坳陷复杂山地山前带处于西昆仑造山带与天山造山带的交汇处,强烈挤压作用造成地下构造高陡破碎,与复杂多变的近地表地震地质条件共同造成地震原始数据信噪比极低,构造成像困难,是国内少有的超高难度探区。受地震资料品质影响,该区油气勘探长期未取得实质性突破。近年来持续开展了地震勘探攻关,采集方面加强近地表调查及激发接收参数优选,优化观测系统设计,开展线束地震及高密度宽方位三维地震采集技术攻关;处理方面探索多重联合约束初至层析反演、黄土区“黑三角”带强能量噪声压制、真地表速度建模和深度偏移成像等技术。经过技术攻关,地震资料品质不断得到提高,发现和落实了一批钻探目标,首次在侏罗系砂岩和石炭—二叠系碳酸盐岩取得两项重大突破,打开了塔西南山前带油气勘探新局面。

塔西南石炭系卡拉沙依组烃源岩评价与优选

塔西南地区石炭系油气显示丰富,为明确塔西南石炭系卡拉沙依组烃源岩生烃潜力,通过干酪根镜鉴、有机碳测试及盆地模拟等技术方法,对卡拉沙依组烃源岩进行研究评价,结果显示:卡拉沙依组烃源岩主要为Ⅲ型干酪根,TOC(总有机碳)含量介于0.2%~2.8%,平均值为1.0%,Ro(镜质体反射率)均超过0.7%。但烃源岩热演化过程存在差异,巴楚地区石炭系烃源岩仅在海西晚期一次生烃,麦盖提斜坡石炭系烃源岩存在海西晚期和喜山期两期生烃,结合烃源岩厚度、TOC、成熟度和生排烃史等多种因素,认为麦盖提斜坡区卡拉沙依组烃源岩均已成熟并持续生烃,西部山前带烃源岩品质及生烃强度最优。

塔里木盆地富满油田富东1井奥陶系重大发现及意义

位于塔里木盆地阿瓦提凹陷—满加尔凹陷过渡带的富东1井在奥陶系鹰山组2段台缘高能滩获得重大突破,对碳酸盐岩内幕区成藏具有重要意义。通过对富东1井成藏条件、储层特征、油气来源的深入研究,明确了富满油田东部深层寒武系玉尔吐斯组供烃、台缘高能滩成储、上覆致密碳酸盐岩成盖的生储盖组合,并建立了“寒武系供烃、次级网状断裂沟通油源、纵向输导、断控台缘高能滩复合油气成藏”新模式。富东1井的成功钻探,证实了台缘高能滩叠合次级网状断裂改造具备成储成藏能力,突破了早期认为的8000m以下超深层碳酸盐岩高能滩的勘探禁区,拓展了断控碳酸盐岩油气藏模式。同时,也是以台缘高能滩体+次级网状断裂油气藏为勘探思路的成功实践,打开了轮南—富满台缘带勘探新局面,有望引领塔里木盆地超深层复杂海相碳酸盐岩的勘探。

塔西南山前地区恰探1井石炭系—二叠系重大突破与勘探前景

塔西南山前地区西天山冲断带乌恰构造带恰探1井在石炭系—二叠系碳酸盐岩获得重大突破,标志着塔西南山前地区发现一个重要的勘探接替层系。结合区域地质资料,根据野外露头、钻井、地震等研究,以及恰探1井、昆探1井等分析化验资料的综合分析,对塔西南山前地区石炭系—二叠系的成藏条件进行再认识。研究认为,塔西南山前地区晚石炭世—早二叠世发育宽缓的“马蹄形”台缘带,形成了呈带分布的高能滩有利沉积相带,区内二叠系棋盘组发育海湾潟湖相烃源岩,厚度最大达到500m,有机质类型为Ⅰ—Ⅱ型,有机质丰度高;受沉积相带和岩溶作用双重控制,在晚石炭世—早二叠世形成裂缝—孔洞型碳酸盐岩储层,与上覆二叠系棋盘组厚层泥岩构成有利生储盖组合,进而建立了“下生上储、断裂输导、近源成藏”的油气成藏新模式。综合分析认为,该地区石炭系—二叠系断背斜圈闭成排成带分布,具有近源成藏优势,评价优选出了叶探1井、阿北1JS井等多个有利勘探目标方向,具有良好的勘探前景,可成为规模天然气勘探发现的重要接替领域。

塔里木盆地西南地区前寒武纪基底结构及其演化

随着塔里木盆地西南地区深层油气勘探的深入,其前寒武纪基底结构和演化如何影响前寒武纪地层发育及其分布的相关研究具有重要的意义。目前对塔西南前寒武纪基底结构特征缺乏系统全面的认识,制约着该区超深层油气勘探的进一步推进。基于前人的研究成果,采用地质-地球物理综合研究方法,结合前寒武纪基底测年结果,对塔西南地区前寒武纪基底岩性、年龄、结构和演化进行了分析。塔西南前寒武纪基底结构在巴楚隆起区表现为古生界直接上覆在古元古界变质岩/花岗岩之上,在麦盖提斜坡—西南坳陷表现为典型的三层结构,最底部为古元古代变质岩/花岗岩,上覆为南华纪裂陷—震旦纪坳陷演化过程的沉积建造。塔西南前寒武纪基底演化主要经历了5个阶段,即哥伦比亚大陆裂解期(>1.1 Ga)、塔西南地块与澳大利亚板块聚合期(约1.0 Ga)、南—北塔里木地块聚合期(900~800 Ma)、南华纪裂陷期(760~640 Ma)和震旦纪坳陷期(<635 Ma)。其中,南华纪裂陷期的隆坳结构控制了震旦系—下寒武统的发育。对塔西南地区前寒武纪基底结构和演化的认识,可为该区深层油气勘探提供重要的理论基础,有助于推动超深层油气勘探的进一步发展。