Origin of the unusually high dibenzothiophene concentrations in Lower Ordovician oils from the Tazhong Uplift,Tarim Basin,China

The origin of the unusually high dibenzothiophene （DBT） concentrations in Lower Ordovician oils from the Tazhong Uplift,Tarim Basin was studied by Fourier transform ion cyclotron resonance mass spectrometry （FT-ICR MS）.The most abundant sulfur compounds in the oils are S 1 species with doublebond equivalent （DBE） values of 1-19 and 11-48 carbon atoms.The range of the number of carbon atoms in the sulfur compounds detected by the FT-ICR MS （S 1 species with DBE=9） is about ten times larger than that for sulfur compounds detected by GC/MS （DBTs）.This suggests that FT-ICR MS is a much better approach than GC/MS for characterization of DBTs in crude oils.The abundance of S 1 species with DBE=1-8 decreased with increasing thermal maturity,while the abundance of S 1 species with DBE=9 （primarily DBTs） increased.Therefore,thermal maturity is an important factor in the formation of oils with high DBT concentrations.Unusually high abundances of S 1 species with low DBE values （1-8）,which include sulfide,thiophene and benzothiophene,were observed in several oils,especially the TZ83 （O 1） oil with high or very high thermal maturity.Thermochemical sulfate reduction （TSR） was thought to be the reason for the high abundance of these low DBE compounds in deep reservoirs,and thermochemical sulfate reduction could affect the distribution and composition of DBTs in the oils.According to the results of FT-ICR MS analysis,there are no signs that TSR is occurring or has occurred recently for most of the Lower Ordovician oils.

Distribution and Significance of Carbazole Compounds in Palaeozoic Oils from the Tazhong Uplift, Tarim

Carbazole compounds in crude oils from the Tazhong uplift of the Tarim basin have been fractionated and detected and successfully used to study petroleum migration and trace source rocks in the study area. Alkylcarbazoles have been found in large amounts in the oil samples analyzed and alkylbenzocarbazoles detected in a small concentration only in part of the samples, but alkyldibenzocarbazoles have not been found in oils. Based on the distribution of G1, G2 and G3 of C2-alkylcarbazoles, the ratio of C3-carbazoles to C2-carbazoles and the relative amounts of alkylcarbazoles and alkylbenzocarbazoles, one can know that the vertical oil migration in the Tazhong uplift is generally from below upward, i.e. from the Ordovician through the Silurian to the Carboniferous. Evidently, source rocks in the uplift should be lower Palaeozoic strata (Ordovician and Cambrian). This study shows that carbazoles are of great importance in the study of petroleum migration and source rocks.

Comparison of the Surface and Underground Natural Gas Occurrences in the Tazhong Uplift of the Tarim Basin

The oil, gas and water volumes revealed by the productivity of exploratory wells do not reflect the actual underground situations. Under the geologic conditions, a certain amount of dissolved natural gas is stored in oil or water. Based on the production test data of exploratory wells in the Tazhong uplift of the Tarim basin, this paper discusses in detail the differences in occurrence and distribution featrues between the surface and underground natural gases; presents a restoration of the surface gas occurrence to actual underground geologic conditions according to the dissolubility of natural gas under different temperature, pressure and medium conditions; and classifies the natural gas into three states, i.e. the oversaturated, saturated and undersaturated, according to its relative content underground. Through a comparative analysis of the differences in surface and underground occurrences of natural gas, it discusses the hydrocarbon reservoir formation mechanism and distribution rules, thereby providing guidances as new methods and technologies for the prediction of potential natural gas reservoir distribution in the study area.

Control of facies and fluid potential on hydrocarbon accumulation and prediction of favorable Silurian targets in the Tazhong Uplift,Tarim Basin,China

Exploration practices show that the Silurian hydrocarbon accumulation in the Tazhong Uplift is extremely complicated.Our research indicates that the oil and gas accumulation is controlled by favorable facies and low fluid potential.At the macro level,hydrocarbon distribution in this uplift is controlled by structural zones and sedimentary systems.At the micro level,oil occurrences are dominated by lithofacies and petrophysical facies.The control of facies is embodied in high porosity and permeability controlling hydrocarbon accumulation.Besides,the macro oil and gas distribution in the uplift is also influenced by the relatively low fluid potential at local highs,where most successful wells are located.These wells are also closely related to the adjacent fractures.Therefore,the Silurian hydrocarbon accumulation mechanism in the Tazhong Uplift can be described as follows.Induced by structures,the deep and overpressured fluids migrated through faults into the sand bodies with relatively low potential and high porosity and permeability.The released overpressure expelled the oil and gas into the normal-pressured zones,and the hydrocarbon was preserved by the overlying caprock of poorly compacted Carboniferous and Permian mudstones.Such a mechanism reflects favorable facies and low potential controlling hydrocarbon accumulation.Based on the statistical analysis of the reservoirs and commercial wells in the uplift,a relationship between oil-bearing property in traps and the facies-potential index was established,and a prediction of two favorable targets was made.

Post-Triassic thermal history of the Tazhong Uplift Zone in the Tarim Basin, Northwest China: Evidence from apatite fssion-track thermochronology

The Tarim Basin is a representative example of the basins developed in the northwest China that are characterized by multiple stages of heating and cooling.In order to better understand its complex thermal history,apatite fission track （AFT） thermochronology was applied to borehole samples from the Tazhong Uplift Zone （TUZ）.Twelve sedimentary samples of Silurian to Triassic depositional ages were analyzed from depths coinciding with the apatite partial annealing zone （～60-120 ℃）.The AFT ages,ranging from 132 ± 7 Ma （from a Triassic sample） to 25 ± 2 Ma （from a Carboniferous sample）,are clearly younger than their depositional ages and demonstrate a total resetting of the AFT thermometer after deposition.The AFT ages vary among different tectonic belts and decrease from the No.Ten Faulted Zone （133-105 Ma） in the northwest,the Central Horst Zone in the middle （108-37 Ma）,to the East Buried Hill Zone in the south （51 25 Ma）.Given the low magnitude of post-Triassic burial heating evidenced by low vitrinite reflectance values （Ro ＜ 0.7％）,the total resetting of the AFT system is speculated to result from the hot fluid flow along the faults.Thermal effects along the faults are well documented by younger AFT ages and unimodal single grain age distributions in the vicinity of the faults.Permian-early Triassic basaltic volcanism may be responsible for the early Triassic total annealing of those samples lacking connectivity with the fault.The above arguments are supported by thermal modeling results.

Strike-Slip Faults and Their Control on Differential Hydrocarbon Enrichment in Carbonate Karst Reservoirs: A Case Study of Yingshan Formation on Northern Slope of Tazhong Uplift, Tarim Basin

Objective Oil and gas are abundant in the Ordovician Yingshan Formation carbonate karst reservoirs on the northern slope of Tazhong uplift in the Tarim Basin, and have extremely complicated oil-gas-water distribution, however. The difference in burial depth of the reservoirs between east and west sides is up to 1000 m. Water-bearing formations exist between oil- and gas-bearing formations vertically and water-producing wells are drilled between oil- and gas-producing wells. Macroscopically, oil and gas occur at low positions, while water occurs at high positiona on the northern slope of Tazhong uplift. The mechanism of differential hydrocarbon enrichment in heterogeneous reservoirs is by far not clarified, which has affected the efficient exploration and development of oil and gas fields in this area.

Differences and controlling factors of composite hydrocarbon accumulations in the Tazhong uplift, Tarim Basin, NW China

Based on three-dimensional seismic interpretation, structural and sedimentary feature analysis, and examination of fluid properties and production dynamics, the regularity and main controlling factors of hydrocarbon accumulation in the Tazhong uplift, Tarim Basin are investigated. The results show that the oil and gas in the Tazhong uplift has the characteristics of complex accumulation mainly controlled by faults, and more than 80% of the oil and gas reserves are enriched along fault zones. There are large thrust and strike-slip faults in the Tazhong uplift, and the coupling relationship between the formation and evolution of the faults and accumulation determine the difference in complex oil and gas accumulations. The active scale and stage of faults determine the fullness of the traps and the balance of the phase, that is, the blocking of the transport system, the insufficient filling of oil and gas, and the unsteady state of fluid accumulation are dependent on the faults. The multi-period tectonic sedimentary evolution controls the differences of trap conditions in the fault zones, and the multi-phase hydrocarbon migration and accumulation causes the differences of fluid distribution in the fault zones. The theory of differential oil and gas accumulation controlled by fault is the key to the overall evaluation, three-dimensional development and discovery of new reserves in the Tazhong uplift.

Geochemistry and possible origin of the hydrocarbons from Wells Zhongshen1 and Zhongshen1C, Tazhong Uplift

In 2013, a great breakthrough of deep petroleum exploration was achieved in the Cambrian pre-salt intervals of Wells Zhongshen1(ZS1) and Zhongshen1C(ZS1C), Tazhong Uplift. However, the hydrocarbon discovery in the Cambrian pre-salt intervals has triggered extensive controversy regarding the source of marine oils in the Tarim Basin. The geochemistry and origin of the Cambrian pre-salt hydrocarbons in Wells ZS1 and ZS1 C were investigated using GC, GC-MS and stable carbon isotope technique. These hydrocarbons can be easily distinguished into two genetic families based on their geochemical and carbon isotopic compositions. The oil and natural gases from the Awatage Formation of Well ZS1 are derived from Middle-Upper Ordovician source rocks. In contrast, the condensate and gases from the Xiaoerbulake Formation of Wells ZS1 and ZS1 C probably originate from Cambrian source rocks. The recent discovery of these hydrocarbons with two different sources in Wells ZS1 and ZS1 C suggests that both Middle-Upper Ordovician-sourced hydrocarbons and Cambrian-sourced petroleums are accumulated in the Tazhong Uplift, presenting a great exploration potential.

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.

塔里木盆地塔中隆起中北部地区断裂构造特征及演化

为系统揭示塔里木盆地塔中隆起中北部地区断裂构造特征及其成因演化,通过对该区大连片三维地震工区精细构造解析和相干体等分析,并结合区域动力背景,系统论述了该区的断裂构造类型、几何学特征、差异活动机制及其构造演化过程。研究结果表明,塔中隆起中北部发育了4类7期断裂构造,其中逆冲断裂和走滑断裂尤其发育。平面上北西向弧形逆冲断裂与北东向、北西向及南北向走滑断裂相互交切与耦合;垂向上断裂分层差异活动特征明显,下奥陶统及其以下地层,断裂发育数量多且以线形为主,中奥陶统-中下泥盆统多呈雁列式,上泥盆统-二叠系仅在塔中Ⅱ号断裂带、顺北5号断裂带西南端等地区发育少量断裂。研究区断裂活动受多期、多方向不同性质应力场所控制,经历了极其复杂的演化历史:加里东早期以塔中Ⅱ号断裂带等少量北倾正断层活动为主;加里东中期Ⅰ幕断裂活动强烈,表现为逆冲断裂与走滑断裂协同演化和相互耦合特征,走滑断裂对逆冲断裂的切割或限制作用明显;加里东中期Ⅲ幕断裂活动基本继承了加里东中期Ⅰ幕的构造格局,但在工区北部的顺北4号、5号等断裂带张扭性断裂活动特征显著;加里东晚期-海西早期,部分断裂发生继承性活动且张扭断裂发育范围进一步向南扩大;印支-燕山期,仅有少数断裂发生继承性活动;喜山期该区构造比较稳定,早期形成的复杂断裂构造进入深埋阶段。

Geochemical significances of 8,14-secohopanes in marine crude oils from the Tazhong area in the Tarim Basin,NW China

8,14-secohopanes in the marine oils from the Tazhong area in the Tarim Basin are detected by gas chromatography-mass spectrometry(GC-MS)and gas chromatography-mass spectrometry-mass spectrometry(GC-MS-MS),and their distributions and compositions are compared in order to study their potential significances in oil-source correlation.C35+extended hopane series and three series of extended 8,14-secohopanes can be detected in two kinds of end-member oils in the Tazhong area in the Tarim Basin,and they are different in distribution,suggesting that they may have some special geochemical significance.The presence of 8,14-secohopanes in two kinds of end-member oils in the Tarim Basin suggests that these biomarkers are primary,and not related to biodegradation.The relative abundance of 8,14-secohopanes in the type-A oil is much less than that in the type-B oil,and the 8,14-secohopanes content in end-member oils is much less than that in the corresponding mixed oils.Based on the relative contents of 8,14-secohopanes and the compositions of common steranes and triterpanes,it is very effective to distinguish different crude oils from the Tazhong area.The great difference in the relative abundance of 8,14-secohopanes between the type-A oil and type-B oil suggests that their formation may require some specific geological-geochemical conditions.

塔北-塔中隆起奥陶系富油气三角带断裂特征及控藏分析

针对塔北-塔中奥陶系碳酸盐岩富油气三角带断裂控储控藏欠缺系统性认识的问题,通过地震精细解释和构造力学机制分析,对塔北-塔中地区走滑断裂和油藏分布特征进行系统性研究,尤其从断层形成的力学机制、断层规模、断层分段性及断层组合样式等方面,剖析富油气三角带的发育特征及油气富集机制。研究表明:塔北-塔中地区的油气受控于2条区域级走滑断裂,其组合形成的富油气三角带内各断裂级别差异明显,且存在明显分段特征;塔中地区断裂带一般分为线性段、斜列段和羽状段,塔北地区断裂带可分为辫状堑垒段、拉分段和羽状段;断裂分段性导致同一断裂不同段油气富集特征具有明显差异,针对不同段可采用不同程度的开发方式,能有效提高储量整体动用程度。该研究可为国内外相似地质条件的碳酸盐岩油气藏勘探提供有益的借鉴。

塔里木盆地顺北5号走滑断裂隆起段发育特征与演化机制

顺北5号带作为一条贯穿两大古隆起的主干走滑断裂带,可分为四段:北段、中段、南段以及隆起段,一直以来是塔里木盆地顺北地区及邻区走滑断裂体系形成及演化的研究重点。利用最新采集处理的高精度三维地震资料,开展顺北5号带隆起段精细解析,厘定其几何学和运动学特征,揭示顺北5号带形成演化过程。基于走向角度变化与分段变形样式,可将隆起段分为3段:隆Ⅰ“平移”段(NE16°)、隆Ⅱ“拉分”段(NE19°)、隆Ⅲ“压隆”段(NE25°)。隆起段自下而上发育高陡走滑断层与多套雁列正断层组合的分层变形样式,共经历了加里东中期、加里东晚期、海西中-晚期和印支期—喜马拉雅早期多期走滑活动,在研究区内表现为“隆Ⅱ、Ⅲ段强,隆Ⅰ段弱”的活动特征。受SN差异应力传递影响,顺北5号断裂隆起段和南段初期以塔中Ⅰ号断裂带为界自南向北左行走滑,北段和中段自北向南右行活动,最大主应力发生了NW向到NE向偏转;加里东晚期后,顺北5号断裂整体左行走滑;印支期—喜马拉雅早期,顺北5号断裂隆起段反转为右行走滑活动,最大主应力方向由NW向转为NE向。

碳酸盐团簇同位素约束下塔中隆起奥陶系热历史

碳酸盐团簇同位素是近年来兴起的一种新型古温标,其有效地解决了碳酸盐岩沉积盆地缺乏常用古温标的现状,对于沉积盆地热史恢复具有重要意义.本文采集了塔中地区奥陶系碳酸盐岩钻井取芯样品,利用一阶近似模型模拟了塔中隆起碳酸盐团簇同位素温度(T_(Δ47))热演化路径,并结合等效镜质体反射率约束了塔中隆起的热历史.塔中隆起大地热流自奥陶纪到现今总体呈降低趋势,自60~70 mW·m^(-2)降低至40~50 mW·m^(-2),二叠纪由于火成岩入侵造成热流短暂升高至60~70 mW·m^(-2).模拟结果认为,北部斜坡带及潜山构造带受火成岩影响显著,北部斜坡带及潜山构造带在二叠纪最高温度分别达到160~170℃及180~190℃;而塔中南缘未受影响,中生代或者现今为最高温度130~140℃.总的来说,碳酸盐团簇同位素在热史领域的研究目前还处于探索阶段,未来有望在重排规律、T_(Δ47)影响因素以及模型理论方面有待进一步完善,团簇同位素也将在热史领域的研究中产生愈加重大的影响力.

塔里木盆地中央隆起带断裂系统分析

本文以地震剖面解释为基础,深入分析塔里木盆地中央隆起带主要断裂带的构造样式和变形特征,确定不同时期断裂系统的分布规律,并试图建立中央隆起带断裂系统发育与周缘造山带演化之间的联系,进而阐明其发育的动力学背景。论文提出了塔里木盆地中央隆起带断裂构造变形样式分类体系;在巴楚隆起的南部边缘,识别出两套区域性的盖层滑脱构造系统,其中浅层色力布亚-玛扎塔格滑脱冲断层逆冲到巴楚南部边缘之上,并构成了现今塔西南前陆冲断系的锋缘断裂;发现了分布在塘古巴斯坳陷的中东部和塔中隆起东部的、规模巨大的、向北西方向凸出的弧形逆冲断裂系统。该弧形逆冲断裂系统的东南部以车尔臣断裂为界,主要形成于晚奥陶世末期,锋缘断裂以盖层滑脱逆冲为特征,与早奥陶世末期发育的、呈NW向展布的塔中Ⅰ号断裂带、塔中10号断裂带、塔中2号断裂带和塔中22号断裂带等构成的基底卷入式逆冲断裂形成明显的交切关系;论文将周缘造山带的重大构造运动事件与塔里木盆地内部不同时期发育的断裂系统相对比,在塔里木盆地内划分出分别与西昆仑造山带、阿尔金造山带和南天山造山带相关的三套断裂系统。

塔中隆起海相碳酸盐岩大型凝析气田成藏特征与勘探

多次资评与勘探实践表明塔中隆起成藏条件优越,海相碳酸盐岩油气资源丰富,奥陶系油气藏集中赋存于上奥陶统礁滩体与下奥陶统风化壳储层中,缝洞系统控制了大型凝析气藏纵向多套叠置-横向准层状分布规律。多学科、动静态一体化研究表明,形成塔中海相碳酸盐岩大型凝析气田主力烃源岩为寒武-奥陶系两套碳酸盐岩,原油具有明显的混源特征,天然气主要来源于中-下寒武统高成熟度原油裂解气。奥陶系海相碳酸盐岩凝析气藏是古油藏在喜山期被寒武系来源的原油裂解气气侵的结果,经历了三期成藏过程,即中晚加里东期、晚海西期原油充注,喜山期注气。两套烃源岩长期供烃是形成塔中奥陶系海相碳酸盐岩大型凝析气田的物质基础,构造作用、岩溶作用是形成了塔中奥陶系多套优质碳酸盐岩储集体的主控因素,断裂、不整合面、缝洞发育带构建的网状油气输导体系是塔中海相碳酸盐岩复式聚集混源成藏的重要保障。塔中奥陶系海相碳酸盐岩具备10亿吨当量的油气资源潜力。

塔中隆起原油特征与成因类型

塔里木盆地塔中隆起油气性质多样、分布与成因复杂,为揭示油气的特征与成因,对塔中及外围104个原油样品进行了精细地球化学研究.依据单体烃碳同位素、特征生物标志物分析,将塔中原油分为4种类型:(1)寒武系成因原油,具有较重正构烷烃单体烃碳同位素(-29.6‰^-29.1‰)、甲藻甾烷较发育及C27、C28、C29规则甾烷呈反"L"型或线型分布等特征;(2)中、上奥陶统成因原油,具有较轻的正构烷烃单体烃同位素(-34‰^-35.6‰)、甲藻甾烷等不太发育与C27、C28、C29规则甾烷呈"V"型分布等特征;(3)富含含硫芳烃-二苯并噻吩原油,主要分布于塔中4井区;(4)混源油,单体烃碳同位素特征界于Ⅰ、Ⅱ类原油之间,是塔中最为主要的原油类型.油-油对比与油气性质分析表明,塔中地区至少有两套主力烃源岩供烃.塔中部分原油生物标志物显示寒武系-下奥陶统成因特征,而单体烃碳同位素却与中上奥陶统成因原油更为接近,这种不同馏分的不一致现象系不同成因原油混源的结果,反映单一应用生物标志物指标有其局限性.塔中油气性质具有分带、分块、分层特征,反映叠合盆地多源、多期成藏、储层非均质性等多种特性.

塔里木盆地塔中隆起断控复式油气聚集的差异性及主控因素

基于三维地震精细解释、构造与沉积特征剖析、流体性质及生产动态研究,探讨塔里木盆地塔中隆起油气成藏规律及主控因素。研究结果表明,塔中隆起油气具有以断裂为主控因素的复式成藏特征,80%以上油气储量沿断裂带富集;塔中隆起发育大型逆冲及走滑断裂,断裂形成演化与成藏耦合关系决定了复式油气聚集的差异性,断裂活动规模与期次决定了圈闭的充满程度与相态平衡,即输导体系的不畅通、油气充注的不充分、流体聚集的非平衡等受控于断裂,多期构造沉积演化控制了断裂带圈闭条件的差异性,多期油气运聚成藏控制了断裂带流体分布的差异性。断控复式油气差异性聚集理论是塔中隆起整体评价、立体开发与增储上产的关键。

塔中北围斜区北东向走滑断裂特征及其控油作用

塔里木盆地塔中北围斜区发育一系列北东走向的走滑断裂,主要发育花状构造、平行高陡断裂带、雁列构造等多种构造样式。加里东中期塔中Ⅰ号断裂、南缘断裂活动剧烈,北西向的逆掩岩片或滑动块体中由于差异运动而形成了北东走向的撕裂断层-调节断层。加里东末期塔中地区受到东南向强烈斜向挤压作用是走滑断裂形成的动力机制,在基底薄弱带的基础上,塔中地区发生了右旋走滑特征。在这种板内挤压转换构造背景下,形成了一些连接北西向逆冲断层的北东向走滑断裂。加里东晚期—海西早期断裂基本上沿着加里东中期的调节断层带的基础上继承发育,具有多期活动的特征。走滑断裂对碳酸盐岩储集层具有强烈的改造作用,还控制了古生界碎屑岩构造圈闭的发育,并作为重要的油气运移通道。

塔中北斜坡志留系岩性油藏形成条件与勘探方向

对塔中志留系的整体评价与综合研究表明,长期稳定的斜坡背景有利于岩性地层圈闭的形成,潮坪相沉积的砂泥岩薄互层是形成岩性圈闭的地质基础,多期油气充注与调整造成了普遍含油的格局,塔中志留系具有形成大面积、低丰度岩性油藏的地质条件。塔中志留系的勘探要突破局部构造控油的思路,把岩性油藏作为志留系的主要勘探对象;岩性上倾尖灭区是有利的成藏领域;东部志留系岩性相变带、地层超覆带是石油勘探的主战场。