鄂尔多斯盆地吴起油田长7储层岩石力学特征

吴起油田长7致密油勘探取得重大突破,23口详探井试油获工业油流。因该地区尚未规模开发,储层改造可借鉴资料不多,尤其是储层岩石力学特征有待试验和分析。利用多口探井的常规和密闭取心样品,通过扫描电镜、荧光薄片、铸体薄片、X射线衍射仪、岩石硬度测定仪、抗拉强度试验装置、单轴及三轴强度试验装置以及Kaiser效应声发射法等仪器和技术,开展了储层特征和岩石力学实验。结果表明:1)储层致密,呈特低孔渗特征,主要孔隙为粒间孔和长石溶孔;2)储层岩石为亲油性,储层具有较弱的速敏性和酸敏性,中等偏弱的水敏性、盐敏性及碱敏性特征;3)岩石硬度类别为硬,砂泥互层的抗拉强度大于纯砂岩抗拉强度;4)围压增大,轴向和径向压力增大,储层以水平主应力为主。实验结果对储层的储量计算、开发方案编制及体积压裂等作业具有重要参考意义。

Characteristics and control factors of feldspar dissolution in gravity flow sandstone of Chang 7 Member,Triassic Yanchang Formation,Ordos Basin,NW China

To clarify the formation and distribution of feldspar dissolution pores and predict the distribution of high-quality reservoir in gravity flow sandstone of the 7^(th) member of Triassic Yanchang Formation(Chang 7 Member)in the Ordos Basin,thin sections,scanning electron microscopy,energy spectrum analysis,X-ray diffraction whole rock analysis,and dissolution experiments are employed in this study to investigate the characteristics and control factors of feldspar dissolution pores.The results show that:(1)Three types of diagenetic processes are observed in the feldspar of Chang 7 sandstone in the study area:secondary overgrowth of feldspar,replacement by clay and calcite,and dissolution of detrital feldspar.(2)The feldspar dissolution of Chang 7 tight sandstone is caused by organic acid,and is further affected by the type of feldspar,the degree of early feldspar alteration,and the buffering effect of mica debris on organic acid.(3)Feldspars have varying degrees of dissolution.Potassium feldspar is more susceptible to dissolution than plagioclase.Among potassium feldspar,orthoclase is more soluble than microcline,and unaltered feldspar is more soluble than early kaolinized or sericitized feldspar.(4)The dissolution experiment demonstrated that the presence of mica can hinder the dissolution of feldspar.Mica of the same mass has a significantly stronger capacity to consume organic acids than feldspar.(5)Dissolution pores in feldspar of Chang 7 Member are more abundant in areas with low mica content,and they improve the reservoir physical properties,while in areas with high mica content,the number of feldspar dissolution pores decreases significantly.

鄂尔多斯盆地吴起地区长7页岩油烃源岩特征及生排烃潜力

目前吴起地区开发的主力层位侏罗系延安组下组合(延7—延10层)和三叠系延长组上组合(长4+5层和长6层)已到中后期,亟需寻找新的接替层位和接替能源满足油田持续高效稳产的战略目标,三叠系延长组长7段页岩油作为吴起采油厂新的接替层位,具有较大的勘探开发价值。为探明长7页岩油烃源岩的特征及勘探潜力区,进行了岩心分析、测井曲线研究、岩石热解分析、镜检显微组分分析、镜体反射率(R_(o))测试和生排烃潜力计算。结果表明:长7烃源岩的丰度总体上较高,有机碳含量(TOC)主要分布在0.49%~41.02%。长7层有机质类型以Ⅰ型和Ⅱ型为主,生油能力强。烃源岩镜质组表明吴起地区处在成熟阶段,并且以生油为主,反射率R_(o)样品分布集中在0.50%~1.15%,长7段烃源岩生烃强度为(200~600)×10^(4)t/km^(2),排烃强度大多为(200~300)×10^(4)t/km^(2)。综合吴起地区烃源岩厚度和生排烃强度,将长7段页岩油勘探潜力区划分为Ⅰ类、Ⅱ类和Ⅲ类,吴页平1井勘探钻探试油结果证明,烃源岩勘探潜力区是有利的页岩油开发层系和接替层。该研究结果将为吴起地区页岩油下一步勘探开发指明方向。

页岩油水平井全油藏立体开发理念及庆城油田大平台实践

目前国内页岩油开发尚处于起步阶段,其中,鄂尔多斯盆地庆城油田探索形成了全油藏立体开发理念,率先实现了国内陆相页岩油工业规模开发的成功。为阐明全油藏立体开发理念的内涵、形成条件和关键作用,根据陆相湖盆沉积模式和微地震资料,解剖刻画了长7页岩油油层展布特征和水平井压裂缝网轮廓形态,并对典型大平台开发效果进行了评价。结果表明,全油藏立体开发需要具备有地质储层条件和工程造缝能力,长7页岩油储层平面上大面积连片展布、纵向上砂泥叠置互层,源储一体使得油层在立体空间充分发育,压裂缝能够穿层延伸,缝网正视角呈近端高缝穿层、远端收敛的菱形,整体轮廓呈“棍子面包”形态,“W”型交错部署的水平井立体开发井网可实现全油藏储量一次性动用,因此庆城油田大平台开发能够取得成功。现阶段加大全油藏立体开发理念的实践应用,对提升国内陆相页岩油产量、助推页岩油革命具有重要意义。

Microfacies and diagenetic alteration in a semi-deep to deep lacustrine shale: The Yanchang Formation in the Ordos Basin, China

The mineralogical development and diagenetic sequence of lacustrine shales in the Chang 7 Member of the Yanchang Formation in the Ordos Basin are detailed studied.A model of their depositional system and a diagenetic diagram are proposed in this study.Through detailed petrographic,mineralogical,and elemental analyses,four distinct shale types are identified:argillaceous shale,siliceous shale,calcareous shale,and carbonate,clay,and silt-bearing shale.The main diagenetic process in argillaceous shale is the transformation of illite to smectite,negatively impacting shale porosity.Siliceous shale undergoes carbonate cementation and quartz dissolution,contributing to increased porosity,particularly in mesopores.Calcareous shale experiences diagenesis characterised by carbonate formation and dissolution,with a prevalence of siderite.In carbonate,clay,and silt-bearing shale,the dissolution of K-feldspar contributes to illitization of kaolinite.Argillaceous shale,characterised by more clay minerals and lower mesopore volume,is identified as a potential hydrocarbon seal.Siliceous shale,with the highest pore volume and abundant inter-mineral pores,emerges as a promising shale oil reservoir.These findings contribute to a comprehensive understanding of shale properties,aiding in the prediction of shale oil exploration potential in the studied area.

Volcanically Driven Terrestrial Environmental Perturbations during the Carnian Pluvial Episode in the Eastern Tethys

The Carnian Pluvial Episode(CPE)fingerprints global environmental perturbations and biological extinction on land and oceans and is potentially linked to the Wrangellia Large Igneous Province(LIP).However,the correlation between terrestrial environmental changes and Wrangellia volcanism in the Ordos Basin during the CPE remains poorly understood.Records of negative carbon isotopic excursions(NCIEs),mercury(Hg),Hg/TOC,and Hg enrichment factor(HgEF)from oil shales in a large-scale terrestrial Ordos Basin in the Eastern Tethys were correlated with marine and other terrestrial successions.The three significant NCIEs in the study section were consistently correlated with those in the CPE successions of Europe,the UK,and South and North China.The U-Pb geochronology indicates a Ladinian-Carnian age for the Chang 7 Member.A comprehensive overview of the geochronology,NCIE correlation,and previous bio-and chronostratigraphic frameworks shows that the Ladinian-Carnian boundary is located in the lower part of Chang 7 in the Yishicun section.HgEF may be a more reliable proxy for tracing volcanic eruptions than the Hg/TOC ratio because the accumulation rates of TOC content largely vary in terrestrial and marine successions.The records of Hg,Hg/TOC,HgEF,and NCIEs in the Ordos Basin aligned with Carnian successions worldwide and were marked by similar anomalies,indicating a global response to the Wrangellia LIP during the CPE.Anoxia,a warm-humid climate,enhancement of detrital input,and NCIEs are synchronous with the CPE interval in the Ordos Basin,which suggests that the CPE combined with the regional Qinling Orogeny should dominate the enhanced rate of terrigenous input and paleoenvironmental evolution in the Ordos Basin.

Two stages of subsidence and its formation mechanisms in Mid-Late Triassic Ordos Basin,NW China

Based on a large number of newly added deep well data in recent years,the subsidence of the Ordos Basin in the Mid-Late Triassic is systematically studied,and it is proposed that the Ordos Basin experienced two important subsidence events during this depositional period.Through contrastive analysis of the two stages of tectonic subsidence,including stratigraphic characteristics,lithology combination,location of catchment area and sedimentary evolution,it is proposed that both of them are responses to the Indosinian Qinling tectonic activity on the edge of the craton basin.The early subsidence occurred in the Chang 10 Member was featured by high amplitude,large debris supply and fast deposition rate,with coarse debris filling and rapid subsidence accompanied by rapid accumulation,resulting in strata thickness increasing from northeast to southwest in wedge-shape.The subsidence center was located in Huanxian–Zhenyuan–Qingyang–Zhengning areas of southwestern basin with the strata thickness of 800–1300 m.The subsidence center deviating from the depocenter developed multiple catchment areas,until then,unified lake basin has not been formed yet.Under the combined action of subsidence and Carnian heavy rainfall event during the deposition period of Chang 7 Member,a large deep-water depression was formed with slow deposition rate,and the subsidence center coincided with the depocenter basically in the Mahuangshan–Huachi–Huangling areas.The deep-water sediments were 120–320 m thick in the subsidence center,characterized by fine grain.There are differences in the mechanism between the two stages of subsidence.The early one was the response to the northward subduction of the MianLüe Ocean and intense depression under compression in Qinling during Mid-Triassic.The later subsidence is controlled by the weak extensional tectonic environment of the post-collision stage during Late Triassic.

The formation and evolutionary characteristics of organic matter and pyrites in the continental shales of the 3^(rd)submember of Chang 7 Member,Yanchang formation,Ordos Basin,China

Through microscopic analyses(e.g.,organic macerals,thin section observation,scanning electron microscope(SEM)imaging of fresh bedding planes via argon ion milling,and energy spectrum tests)combined with Rock-Eval analyses,this study systematically investigated the organic matter and pyrites in the continental shales in the 3^(rd)submember of the Chang 7 Member(Chang 7^(3)submember)in the Yanchang Formation,Ordos Basin and determined their types and the formation and evolutionary characteristics.The results are as follows.The organic matter of the continental shales in the Chang 7^(3)submember is dominated by amorphous bituminites and migrabitumens,which have come into being since the early diagenetic stage and middle diagenetic stage A,respectively.The formation and transformation of organic matter is a prerequisite for the formation of pyrites.The Ordos Basin was a continental freshwater lacustrine basin and lacked sulphates in waters during the deposition of the Chang 7 Member.Therefore,the syndiagenetic stage did not witness the formation of large quantities of pyrites.Since the basin entered early diagenetic stage A,large quantities of sulfur ions were released as the primary organic matter got converted into bituminites and,accordingly,pyrites started to form.However,this stage featured poorer fluid and spatial conditions compared with the syndepositional stage due to withdraw of water,the partial formation of bituminites,and a certain degree of compaction.As a result,large quantities of pyrrhotite failed to transition into typical spherical framboidal pyrites but grew into euhedral monocrystal aggregates.In addition,pyrites are still visible in the migrabitumens in both microfractures and inorganic pores of mudstones and shales,indicating that the pyrite formation period can extend until the middle diagenetic stage A.

一种适用于延长油田长7页岩油水平井产量预测的改进经验模型

延长油田长7陆相页岩油水平井产量前期快速递减、后期缓慢递减。在采用常见的页岩油气经验模型YM-SEPD和Duong法拟合月产和累产数据的基础上,通过定义“截距累产”,引入新的中间变量,在线性拟合中间变量时将拟合月产改为拟合累产,提出了一种新的改进Duong模型,并与另外一种改进Duong模型(WK-Duong模型)进行了对比。结果表明:1)YM-SEPD和Duong模型受月产数据波动影响较大,其中YM-SEPD累产拟合误差的正负值随时间的增加而改变,而Duong模型拟合误差逐渐增大;2)采用WK-Duong模型拟合关键参数q_(1)时,认为拟合直线截距为0,与延长油田陆相页岩油实际生产情况不符,影响拟合精度;3)新的改进Duong法通过拟合累产与相关参数关系,减小了月产数据波动对线性拟合的影响,优化了后续求解过程,与其他几种方法相比拟合精度最高。改进后的Duong方法可用于准确拟合和预测延长油田长7页岩油水平井产量,对陆相页岩油的产量评价具有参考意义。

鄂尔多斯盆地长7致密油储层储集空间特征及其意义

通过对长7致密油储层的核磁共振测试,研究鄂尔多斯盆地长7致密油储层储集空间特征。结果表明:鄂尔多斯盆地长7致密油储层孔隙孔径分布范围宽,储层中大孔、中孔、小孔、微孔及纳米孔孔隙类型均发育,且孔径分布范围、孔隙类型和主体孔隙类型受储层致密程度的控制作用明显;长7致密油储层大孔至纳米孔孔隙均含油,且微孔至纳米孔孔隙含油饱满。长7致密油储层微孔、纳米孔孔隙类型的识别及其含油的认识对鄂尔多斯盆地非常规油气资源的勘探与开发具有一定的启示意义。

鄂尔多斯盆地延长组长7油层组石油成藏条件分析

鄂尔多斯盆地长7油层组沉积期是湖盆发育的鼎盛期,不但沉积了大面积分布的优质烃源岩,而且还发育一定规模的储层。对储层所处沉积环境、储层特征、成岩相及生、储、盖组合等综合地质条件进行分析研究,结果表明,长7储层烃源条件优越,有利储集体主要为三角洲前缘的水下分流河道及半深湖—深湖相浊积岩,岩石类型以低成分成熟度的岩屑长石砂岩和长石岩屑砂岩为主,储层物性差,孔隙度平均8.45%,渗透率平均0.12×10-3μm2,属超低孔低渗储层;发育5种成岩相类型。最有利成岩相为胶结作用—微孔粒间孔和溶蚀作用—溶孔微孔成岩相,分布面积有限;储层物性最差的为压实胶结—微孔成岩相,分布面积较广。半深湖—深湖沉积环境导致长7储层横向连通性差,纵向隔夹层多,油气只能通过垂向和短距离的侧向运移,在遇到泥岩遮挡层或致密砂岩遮挡时在相对物性较好的储层中聚集成藏。

鄂尔多斯盆地延长组长7段致密油储层应力敏感性及影响因素

致密油采用准自然能量开发方式下,对储层的应力敏感性及其控制因素进行研究具有重要的意义。基于地层压力条件下的应力敏感性实验,明确了鄂尔多斯盆地延长组长7段致密油储层主要表现为渗透率的应力敏感性,应力敏感性属弱到中等强度。利用铸体薄片、恒压和恒速压汞、场发射扫描电镜、微米CT成像等测试手段,对长7段不同应力敏感性类型储层的岩石学特征、微观孔隙结构进行系统分析和对比研究,揭示塑性组分含量、填隙物类型及其含量、孔喉尺度是长7段致密油储层应力敏感性不同的主要控制因素。基于长7段致密油开发先导试验区生产实践和储层特征的综合分析,认为在长7段致密油水平井压裂裂缝改造区域,地层压力的快速下降致使应力敏感性对水平井的石油产量和递减率产生显著的影响;同时,在长7段致密油开发过程中,应针对不同物源体系、不同成因类型、不同物性的储层制定不同的开发技术方案,以降低应力敏感性对致密油产能的影响程度。

鄂尔多斯盆地陇东地区长7段烃源岩排烃机制及成藏意义

通过鄂尔多斯盆地陇东地区延长组泥岩综合压实曲线对比,明确研究区长7段烃源岩普遍存在欠压实现象,利用等效深度法计算了泥岩最大埋深时期的过剩压力,结果表明,欠压实产生的过剩压力是长7段烃源岩排烃的重要动力。由此,根据过剩压力的纵向分布特征划分了3种排烃方式,并叠合烃源岩的分布、源储压力差得出长7段烃源岩向其上下地层有利的排烃范围。结果表明,当源储压力差不小于储层的毛管压力时,排烃才可能发生;有利的排烃区受优质烃源岩分布、排烃方式和动力条件的综合控制;长7段烃源岩向下伏地层排烃的条件优于向上覆地层,是现今油藏选择在长8段大规模分布的主要原因;长6段小规模的油藏基本分布在长7段烃源岩向上有利排烃范围之内。

鄂尔多斯盆地三叠系延长组原油中性含氮化合物的分布特征及油气运移

利用长7—长10油层组原油中性含氮化合物的分布特征探讨鄂尔多斯盆地油气运移问题,以期为该区进一步的勘探决策提供油气运移方面的依据。结果表明,延长组原油的中性含氮化合物在平面和剖面方向均存在着明显的运移分馏效应。咔唑类化合物总含量等含氮化合物的运移参数值表明,研究区原油在平面上由峰2井和白165井向元城地区运移,盆地中心原油向富县地区和盆地南部的正10井和长20井运移;在垂向上原油由长7向长10油层组运移,长9油层组原油来自长7油层组烃源岩。

深水碎屑流与浊流混合事件层沉积特征及分布——以鄂尔多斯盆地西南长7油层组为例

采用岩石学、深水沉积学等方法,解剖野外露头及重点钻井岩心,结合测井、分析化验等资料,研究鄂尔多斯盆地西南延长组长7油层组深水碎屑流与浊流混合事件层的沉积特征及分布。结果表明:研究区长7油层组发育下部砂质碎屑流上部浊流混合事件层、下部浊流上部泥质碎屑流混合事件层(分为下部浊流上部富泥质碎屑和下部浊流上部贫泥质碎屑混合事件层)、泥质碎屑流和浊流频繁互层混合事件层3种类型。其中,下部砂质碎屑流上部浊流、下部浊流上部富泥质碎屑混合事件层发育于重力流沉积区的近端和远端,下部浊流上部贫泥质碎屑、泥质碎屑流和浊流频繁互层混合事件层主要分布于重力流沉积区的远端。研究区长7油层组深水重力流沉积具有近端呈条带状分布、水道化特征显著,远端相邻朵体沉积物相互叠置、连片、呈环带状分布的特征。该结果对完善深水重力流沉积理论及开展非常规油气勘探、开发具有指导意义。

鄂尔多斯盆地长7油层组深水重力流沉积分布特征及成因

鄂尔多斯盆地长7油层组广泛发育大规模重力流沉积砂体,对盆地周缘露头及几百口井取心井进行了系统沉积相综合研究。研究结果表明,长7油层组沉积期,湖盆西南及湖盆中部重力流沉积主要为滑塌、砂质碎屑流和浊流,以砂质碎屑流沉积为主;在纵向上,砂质碎屑流沉积和浊流沉积不同组合的多期叠置形成了6种纵向组合类型,并在平面上呈一定的规律性分布;受沉积底形控制,在斜坡区以砂质碎屑流沉积为主,顺斜坡呈带状分布,平面分布规模小;在湖盆中部的坡脚及湖底平原,由于能量减弱,沉积物大量沉积,形成以砂质碎屑流为主的大规模重力流沉积,构成湖盆中部砂体的主体;再往湖盆中心,则主要发育薄层的浊流沉积。成因分析认为,盆地西南较陡的湖盆底形、细粒沉积物的高速率供应和高频次地震促发是重力流砂体发育的重要条件。

利用多参数组合产能系数预测安83井区长7储层的产能方法研究

鄂尔多斯盆地安边地区安83井区长7油藏储层属于典型的致密油藏,影响其产能因素很多,对该区进行产能预测有诸多困难。如何有效利用测井资料来评价致密储层的产能是亟待解决的问题。以测井资料为基础,利用影响每口井储层产能的关键因素(储层有效厚度、渗透率、孔隙度、含油饱和度、电阻率和泥质含量)为主要评价参数建立4种多参数组合产能系数预测模型,对该区进行产能预测,将该区致密储层分为低渗和超低渗储层两类。实践结果表明,该区进行产能预测应用取得较好的实用效果,达到利用测井资料预测该区致密储层产能和指导油田勘探开发目的。

鄂尔多斯盆地三叠系长7致密油藏开发技术探讨

胡尖山地区长7层新出现出油井点多,油层连续性好,油藏规模大的特征,展现出良好的勘探开发前景,是长庆油田在该区的主力区块。该区长7油藏平均孔隙度8.9%,渗透率0.19 mD,属致密油藏,2010年开始进行开发试验,暴露出注水有效驱替系统难建立,递减快,单井产能低,油井见水等问题。本文通过对比分析近年进行的多项开发试验效果,着重从水平井井网形势、储层改造参数等角度对该区长7油藏开发技术进行探讨。

富县地区长7页岩油气富集特征与主控因素

为了摸清富县地区长7页岩油气富集特征与主控因素,以富县地区长7页岩油气勘探实践为基础,结合前人的研究成果,通过分析成藏地质背景、页岩层系内部油气运聚特征以及页岩油气富集特征及模式,对油气富集主控因素进行研究,研究结果表明:1)长7砂岩油藏类型主要为透镜体油藏和上倾尖灭型油藏,已发现油藏主要分布在长7顶部,在研究区东部长7底部发育少量油藏;纵向上烃源岩底部、顶部的砂体、夹在两套烃源岩中间的砂体往往是有利的勘探目标。2)平面上,在研究区中西部长7油藏主要沿三角洲前缘砂体的环古湖岸线、主分流河道分布,在研究区东部油藏主要分布于位于流线汇聚区及流线与砂体大角度相交区域。3)总体来看,页岩段中部、中下部油气含量要高于页岩段上部的油气含量。影响页岩油气含量的因素复杂,主要有TOC、有机质成熟度、黏土矿物含量、孔隙及孔隙结构等,该成果为富县地区长7页岩油气下一步的高效开发,具有一定的指导意义。

鄂尔多斯盆地长7致密油储层储集空间特征及其意义探讨

鄂尔多斯盆地长7致密油储层具相对高孔低渗特征，孔隙类型复杂，常规的测试技术无法识别和表征储集空间特征。通过对长7致密油储层的核磁共振测试和研究，表明盆地长7致密油储层孔隙孔径分布范围宽，储层中大孔、中孔、小孔、微孔及纳米孔隙类型均发育，且孔径分布范围、孔隙类型和主体孔隙类型受储层致密程度的控制作用明显；长7致密油储层大孔隙至纳米孔孔隙均含油，且微孔至纳米孔隙含油饱满。长7致密油储层微孔、纳米孔孔隙类型的识别及其含油的认识对鄂尔多斯盆地非常规油气资源的勘探与开发具有一定的启示意义。