Hydrocarbon migration and accumulation along the fault intersection zone-a case study on the reef-flat systems of the No.1 slope break zone in the Tazhong area, Tarim Basin

Understanding hydrocarbon migration and accumulation mechanisms is one of the key scientif ic problems that should be solved for effective hydrocarbon exploration in the superimposed basins developed in northwest China. The northwest striking No.1 slope break zone, which is a representative of superimposed basins in the Tarim Basin, can be divided into five parts due to the intersection of the northeast strike-slip faults. Controlled by the tectonic framework, the types and properties of reservoirs and the hydrocarbon compositions can also be divided into five parts from east to west. Anomalies of all the parameters were found on the fault intersection zone and weakened up-dip along the structural ridge away from it. Thus, it can be inferred that the intersection zone is the hydrocarbon charging position. This new conclusion differs greatly from the traditional viewpoint, which believes that the hydrocarbon migrates and accumulates along the whole plane of the No.1 slope break zone. The viewpoint is further supported by the evidence from the theory of main pathway systems, obvious improvement of the reservoir quality （2-3 orders of magnitude at the intersection zone） and the formation mechanisms of the fault intersection zone. Differential hydrocarbon migration and entrapment exists in and around the strike- slip faults. This is controlled by the internal structure of faults. It is concluded that the more complicated the fault structure is, the more significant the effects will be. If there is a deformation band, it will hinder the cross fault migration due to the common feature of two to four orders of magnitude reduction in permeability. Otherwise, hydrocarbons tend to accumulate in the up-dip structure under the control of buoyancy. Further research on the internal fault structure should be emphasized.

Controls of Acid-sensitive Minerals on Reservoir Sensitivity Testing： An Example from the Silurian Kepingtage Formation in Tazhong Area, Tarim Basin

The Silurian Kepingtage Formation in Tazhong area is regarded as an acid-sensitive hydrocarbon reservoir. However, formation mechanism of acid-sensitive of the reservoir cannot be interpreted by the existing acid-sensitive evaluation criterion based on damage rate. The contents of acid-sensitive minerals illustrated by bulk-rock XRD, scanning electron microscopy and clay mineral composition analysis exert the dominant control on acid-sensitive flow testing of the reservoir. The ironbearing minerals（including pyrite cements and chlorite cements） mainly deteriorate reservoir quality, while the iron-free minerals（including calcite cements and dolomite cements） mainly improve permeability. The permeability variation of the tested samples is controlled by the relative content of two acid-sensitive minerals. On the basis of newly established sensitivity mechanism and its influence on permeability, the corresponding ion（Fe^（2＋）） stabilizer was added to the acidizing fluids during the acidification reconstruction, which inhibited the negative factors of acid-sensitive minerals and improved the target layer quality effectively.

Characteristics of Paleozoic clastic reservoirs and the relationship with hydrocarbon accumulation in the Tazhong area of the Tarim Basin, west China

In order to predict favorable exploration areas of the Paleozoic, Carboniferous and Silurian clastic reservoirs in the Tazhong area of the Tarim Basin, west China, we studied the basic characteristics of Paleozoic clastic reservoirs in the Tazhong area based on a lot of data. Several issues about the hydrocarbon accumulation related to the reservoirs were also discussed. The results were concluded that： the high-value areas of the porosity and permeability of clastic reservoirs were located in the southeast of the Tazhong area; the content of cement （carbonate cement in particular） was the main factor controlling the porosity and permeability of clastic reservoirs; the hydrocarbon distributions of Carboniferous and Silurian clastic reservoirs were closely related to the porosity and permeability; the favorable hydrocarbon accumulation areas of the two sets of strata were located in the southeast of this area, especially in the updip pinch-out area.

Quantitative assessment of gas washing of oils in the Tazhong area of the Tarim Basin,Northwest China

Gas washing has been known in the Tazhong area of the Tarim Basin,but its quantitative assessment has not yet been reported.Here the influence of gas washing fractionation in the area was discussed based on the gas chromatogram data of 68 oils and the results of the mixing experiments of a black oil and a condensate.The results show that the intensity of gas washing fractionation decreased generally from northern to southern part and vertically from deep reservoirs to shallow reservoirs.The gas washing fractionation was mainly controlled by fault systems in this area,with the increase of n-alkane mass depletion positively correlated to the number and scale of faults.Gas washing fractionation appears to have affected the hydrocarbon property,and as a result the diversity of the crude oils is markedly controlled by gas washing.In addition,the occurrence of waxy oil in this area may be resulted from multiple factors including gas washing,mixed filling and migration fractionation.

低能环境下核形石组构特征及成因——以中15井上奥陶统良里塔格组核形石为例

【目的】奥陶纪时期全球发生了一次生物大辐射,核形石研究对于揭示该期古环境特征及演化具有重要意义。【方法】以塔里木盆地塔中地区中15井核形石为研究对象,通过详细地岩心观察和室内薄片、扫描电镜鉴定,统计、分析核形石宏观形态、微观组构特征,探讨了其形成环境、成因及地质意义。【结果】塔里木盆地塔中地区中15井上奥陶统良里塔格组泥质条带灰岩段为开阔台地的台内洼地沉积,中上部发育一套厚约12.3 m的深灰色含泥质条带核形石灰岩、含生屑泥晶核形石灰岩,核形石粒径大、丰度高。核心为早期台缘生屑、团块;包壳厚度大,富含细菌纹层;基质中多充填灰泥、细生屑,普遍发育泥质条带;代表了一种水体搅动及搬运作用不强烈的原地或近距离搬运沉积成因。核形石可分为球状、帽状、板条状、椭球状等四类,以帽状、球状为主。垂向上为三个核形石发育段,单个旋回含量、粒度呈变大趋势。【结论】球状、帽状核形石形成于水体搅动和静止相交替状态的环境,板条状核形石形成于弱搅动的低能环境。中15井核形石的产出受奥陶纪全球海平面上升以及生物大辐射影响,具体为丰富的核心物质来源(相邻台缘带生屑、团块)、发育程度高的细菌黏附生长、稳定或弱波动的沉积环境等因素的有机耦合。

Reservoir geochemistry of the Tazhong oilfield in the Tarim Basin, China, Part I. Geochemical characteristics and genetic classification of crude oils

According to the assemblage characteristics of saturated hydrocarbon biomarkers in crude oils and their geochemical implications, this study has proposed, for the first time, the criteria for the genetic classification of crude oils in the Tazhong area of the Tarim Basin, China. Crude oils from the area studied are classified as three genetic types: type-I is characterized by the low contents of C29 norhopane, extremely abundant contents of gammacerane, low contents of rearranged sterane and relatively high contents of regular C28 sterane; the geochemical properties of type-II crude oils are opposite to those of type-I crude oils; the parameters for type-III crude oils are intermediate between type-I and type-II. Results of oil correlation indicated that type-I crude oils were derived from Cambrian-Lower Ordovician hydrocarbon source rocks, type-II curde oils originated from Middle-Upper Ordovician hydrocarbon source rocks and type-III crude oils are of mixed origin.

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。

塔中西北部奥陶系碳酸盐岩埋藏溶蚀作用

对塔中西北部奥陶系碳酸盐岩埋藏溶蚀发育的地质背景、充填矿物（岩石）学-地球化学特征进行了研究,埋藏溶蚀作用在碳酸盐岩储层发育中有重要作用.塔中西北部多期次构造活动和中-晚二叠世为主的岩浆-热液活动是埋藏溶蚀产生的基本条件;深埋或热液作用是以黄铁矿、绿泥石、石英、铁方解石、萤石等标型矿物和具有能发出明亮桔黄色光的富锰贫铁方解石胶结物、生长环带、铁白云石溶蚀等特征.方解石充填物中富含铁、锰、镁、锶等元素,δ18OPDB平均值为-6.6‰,δ13CPDB平均值为-2.0‰;流体包裹体均一温度为115～130℃和170～210℃,盐度为5%～7%、8%～9%和12%～13%,反映了埋藏成岩作用中有深部流体或循环流体参与.

塔中Ⅰ号断裂坡折带构造特征及勘探领域

利用新的三维地震资料,综合运用等时地层格架及构造解析方法,分析了塔中Ⅰ号构造带复杂的构造特征及油气富集的差异性。研究结果表明:塔中Ⅰ号构造带是早奥陶世末至晚奥陶世早期形成的大型逆冲断裂带,在上奥陶统沉积前遭受长期侵蚀而形成复杂的断裂坡折带。在上奥陶统良里塔格组沉积时,沿高陡断裂坡折带发育台地边缘礁滩复合体,形成碳酸盐岩沉积坡折带。塔中Ⅰ号断裂坡折带在横向上具有分段性,其间通过构造变换带的调节作用分为结构与形成演化各具特征的5 段,各段油气富集具有明显的差异性。塔中44井区礁滩复合体发育,是实现碳酸盐岩高产、稳产勘探的首选领域;塔中45 井区构造作用与岩溶作用强烈,是寻找大规模缝洞系统的有利领域。这2个区带是在塔中Ⅰ号断裂坡折带寻找大油气田的主攻目标。

塔里木盆地塔中地区地层水化学特征及其石油地质意义

塔中地区主要含油层系奥陶系、志留系和石炭系地层水化学研究结果表明，奥陶系、志留系和石炭系地层水矿化度很高，是阴、阳离子分别以Cl-和K＋Na＋为主的氯化钙型水，钠氯系数平均值在0．73-0．87，脱硫酸系数平均值在1．54-9．29，变质系数平均值在5．54-12．80。剖面上，奥陶系、志留系和石炭系地层水化学成分和离子比值随深度表现为反向型、正向型和稳定型3种变化类型；平面上，石炭系地层水化学相对变化不大，而奥陶系地层水化学变化比较复杂。奥陶系、志留系和石炭系现今地层水总体处于封闭的流体动力环境，但奥陶系、志留系和石炭系CⅢ油组内部的流体动力环境相差较大，油气的聚集和保存条件也相差较大；而石炭系CI和CⅡ油组内部的流体动力环境相差较小，有利于油气的聚集与保存。平面上，在古隆起和沟通浅部地层的断层附近，地层水的矿化度比较低，封闭性相对较差。奥陶系和志留系地层水在地质历史时期曾经遭受过比较强烈的大气降水的入渗，为开放的流体动力环境。其中，志留系地层水曾经处于明显的开放流体动力环境，对油气的聚集和保存极为不利；而石炭系地层水一直处于相对封闭的流体动力环境，有利于油气的聚集和保存。

塔中地区深部流体对碳酸盐岩储层的改造作用

塔中地区岩石及原油的稀土元素分析、二氧化碳碳同位素分析以及储层流体包裹体测温证实了深部流体的存在。盆地基底以下的深部流体通过深大断裂及火山活动进入盆地内,通过物质和能量交换对碳酸盐岩储层进行溶蚀和交代,使碳酸盐岩储集层的孔、渗结构发生改变,从而形成深埋改造型的优质碳酸盐岩储层。塔中西部地区沿大断裂及火山活动区发现的萤石矿带是深部流体作用的产物,是塔中45油田的主要储集层类型。深部流体的来源及活动范围与深大断裂以及火山活动密切相关,深大断裂以及火山岩发育区可以作为寻找深部流体改造型储层的标志。

礁滩相碳酸盐岩岩溶作用及其对孔隙分布的控制——以塔中东部上奥陶统良里塔格组为例

利用岩心、薄片、测井等资料，研究塔中东部地区上奥陶统良里塔格组礁滩相碳酸盐岩的岩溶作用类型、特征及对孔隙分布的控制机理。研究区经历了同生岩溶及早成岩近地表岩溶作用。在良三段-良一段礁滩复合体沉积期，同生岩溶形成具有大量选择性溶蚀孔隙的大气淡水成岩透镜体，发育于各期礁、滩沉积旋回的中上部，单个孔隙（洞）层厚10-30m，可增加3％～4％的绝对孔隙度。沉积期后，沉积物未经历埋藏期成岩作用就抬升、暴露，受到早成岩近地表岩溶作用，沉积地貌转换为岩溶古地貌，在距良里塔格组顶部100m深度内形成了4个岩溶带，表层岩溶带与径流岩溶带孔隙有效性、连通性较好，可增加4％～8％的绝对孔隙度。两种岩溶作用成岩阶段具有连续性、形成的孔隙空间分布具有继承性，良好的时空耦合关系是研究区有效孔隙集中发育在良三段一良一段的关键因素。

塔中地区走滑断裂特征、成因及地质意义

通过对塔中地区构造解析,识别出多条具一定规模的NE向走滑断裂体系,主要活动时期为加里东末期—海西早期,其形成与加里东末期塔里木克拉通南、北两侧发生的强烈碰撞作用以及盆地基底存在的北东向构造有关。走滑断裂对碳酸岩储层改造、火山活动、圈闭形成、油气运移以及成藏有控制作用。

塔中地区北部斜坡带下奥陶统碳酸盐岩风化壳油气富集特征

塔里木盆地塔中地区北部斜坡带下奥陶统发育大型碳酸盐岩风化壳。对风化壳储层及其成藏条件的研究表明,风化壳储层类型以次生溶蚀孔洞形成的低孔、低渗储层为主,储层主要发育于下奥陶统顶部,分布范围与古构造活动形成的不整合面形态具有较好的对应关系。断裂及裂缝的发育对改善风化壳储层具有重要作用,形成了纵向上叠置、横向连片、沿岩溶斜坡部位广泛分布的风化壳储层。断裂和不整合面构成的输导体系控制了风化壳的油气运聚成藏,储层发育程度控制了风化壳的油气富集程度,多期油气充注与风化壳储层非均质性造成了风化壳油气赋存的差异性。

塔中卡塔克区块古岩溶储层地震预测技术

塔里木盆地塔中地区奥陶系古岩溶储层具有埋藏深、非均质性强等特点,但其测井和地震响应较为明显。为此,利用地震、测井和地质资料及地震资料叠后波阻抗反演、属性分析和叠前双相介质储层物性参数反演技术,对该区东南部卡塔克区块下奥陶统古岩溶缝洞型储层进行了识别、预测和含油气检测分析。结果表明,卡塔克区块有5个古岩溶储层发育区带,并综合评价出4个有利钻探目标。优选其中一个目标进行钻探,证实了预测结果的可靠性。

塔里木盆地塔中奥陶系天然气的非烃成因及其成藏意义

塔里木盆地塔中北部斜坡带奥陶系海相碳酸盐岩油气勘探取得了重大突破,发现了台缘坡折带礁滩复合体大型凝析气藏和台内岩溶风化壳大型油气藏。利用有机地化指标与构造沉积演化紧密结合对有效烃源岩及成藏过程的研究取得了较好成果,但随着勘探的纵深发展,流体分布复杂的问题日趋突出,通过天然气组分以及相关同位素等分析化验数据,进行塔中北部斜坡带奥陶系油气成藏研究,建立了"三期成藏、两期调整,早期成油、晚期注气,复式聚集、普遍含油"成藏模式,明确了塔中天然气以原油裂解气为主,强调晚期气侵是形成塔中大型天然气田的关键。

塔里木盆地塔中地区中、上奥陶统生物礁滩特征及储集体预测

塔里木盆地塔中地区中、上奥陶统发育生物礁滩,主要包括生物礁、生屑滩和灰泥丘3种,在测井曲线上表现为低自然伽马、低声波时差和高电阻率性质,在地震反射记录上有直接或间接特征。纵向上礁滩发育分为两个期次,由早期礁滩向晚期丘滩转化,并有向台内迁移的趋势;平面上多呈带状分布于构造发育带、断层上盘、台地边缘、古地貌凸起、台内缓坡以及地貌坡折带附近。早期礁滩主要分布于塔中1号断裂带附近的台缘相,在Z1井—TZ23井的台内低隆处见台内礁滩,偶见台内点礁(TZ35井),在地貌上发育于古凸起、台内缓坡或者地貌变化坡折带;晚期丘滩主要分布于10号断裂带附近的台缘相,在台内低隆亦见台内滩(TZ23井—Z1井),古地貌上发育于塔中凸起或台内低隆等部位。

塔里木盆地塔中地区奥陶系碳酸盐岩礁滩复合体油气来源与运聚成藏研究

近年来对塔里木盆地海相层系油气的勘探进展很快,在塔中地区围绕塔中I号坡折带有重要发现,特别是发现了上奥陶统碳酸盐岩礁滩复合体大面积富含油气。认为该区上奥陶统碳酸盐岩礁滩复合体储层存在多期油气运移聚集,包括晚加里东期油气的聚集、晚海西期古油藏油气的调整转移和直接从烃源岩生成油气的补充以及喜山期古油藏裂解天然气对早期油藏的气侵;塔中地区原油和凝析油主要来源于寒武系-下奥陶统烃源岩,上奥陶统中聚集的油气是沿断裂垂向运移与沿多套储层横向运移面来;塔中奥陶系油气藏之所以表现出外带为凝析气藏、内带为油藏的分布特征,主要与来源于外带下伏的的寒武系-下奥陶统古油藏的裂解气有关,也与I号坡折带北侧的良里塔格组斜坡相古油藏的裂解气有关,这些天然气沿I号坡折带向上运移,补充到位于I号坡折带附近的礁滩复合体油气藏中,并对原来的油藏产生气侵,气侵程度的不同,或者形成凝析气藏,或者仍然保持油藏。

塔中地区上泥盆统东河砂岩和志留系砂岩的锆石特征、SHRIMP U-Pb年龄及地质意义

对塔中地区中1井等6口探井的东河砂岩和志留系砂岩中的25件重砂矿物中的锆石进行了一般特征分析,并选择了9件样品中的1666个单颗粒锆石进行了内部特征和72次微区U-Pb同位素测龄研究。研究表明:塔中东河砂岩中的锆石一般具有较高的磨圆度、相对高比例的岩浆岩来源和稳定的再循环沉积来源特征,反映了较高成熟度和较稳定构造-沉积环境;志留系下砂岩中的锆石来源差异较大,除了再循环沉积岩和岩浆岩来源外,还有变质岩锆石,但它又不具有典型变质锆石的Th/U含量的特征,有二种可能性:一是岩浆型锆石形成后经历了重结晶作用;二是原岩锆石受岩浆或岩浆期后热液影响。锆石的地质年代主要分为:(1)太古宙-古元古代(1.8Ga、2.2Ga和2.6Ga);(2)中新元古代(0.84Ga)和(3)早古生代(477～439.8Ma、431.6～421.1Ma)。上述锆石原岩形成时代及其环境可能是一系列的大陆构造动力学事件的时代响应。

塔里木盆地塔中地区Ⅰ号断裂带上奥陶统良里塔格组储集层类型及有利区带预测

塔里木盆地塔中地区Ⅰ号断裂带上奥陶统良里塔格组为目前国内较典型的碳酸盐岩油气储集层,且有巨大的勘探潜力,深入研究该套储集层的类型及分布对塔中地区的下一步勘探将具有重要的指导意义。通过大量岩心分析,根据孔隙度—渗透率相关关系将塔中地区Ⅰ号断裂带上奥陶统良里塔格组碳酸盐岩储集层划分为3种主要类型:孔隙型、裂缝型、裂缝—孔隙型。根据各单井储集层类型,结合沉积相及断裂等储集层影响因素,推断了良里塔格组3个岩性段的不同类型储集层的分布范围,认为裂缝型储集层最为发育,而最有利于油气成藏的裂缝—孔隙型储集层主要发育于良二段,孔隙型储集层分布范围较小。最后认为塔中Ⅰ号断裂带塔中82井区—塔中24井区为油气勘探最有利区。