Geological and Engineering‘Sweet Spots'in the Permian Lucaogou Formation,Jimusar Sag,Junggar Basin

Unconventional oil and gas resources require petrophysical logs to answer the question of how best to optimize geological and engineering‘sweet spots'.Therefore,the establishment of a key well with comprehensive descriptions of lithology,reservoir properties,hydrocarbon-bearing properties,electronic well log responses,source rock properties,brittleness,and in situ stress magnitude and direction is important for the effective exploration and production of unconventional hydrocarbon resources.Cores,thin sections,scanning electron microscopy(SEM)and comprehensive well log suites are used to build a key well for the Permian Lucaogou Formation,Jimusar Sag of the Junggar Basin.The results show that there are three main types of lithologies,including siltstone,mudstone and dolostone.Lithologies can be predicted using the combination of conventional well and image logs.The pore spaces consist of interparticle pores,intragranular dissolution pores and micropores.Nuclear Magnetic Resonance(NMR)T_(2)components longer than 1.7 ms are superposed as effective porosity.Permeability is calculated using the Coates model from NMR T_(2)spectra.The ratio of T_(2)components>7.0 ms to T_(2)components>0.3 ms is used to calculate oil saturation.TOC is calculated using theΔlog R method.Brittleness index is calculated using Poisson-Young's method,ranging from 13.42%-70.53%.In situ stress direction is determined,and in situ stress magnitudes(maximum horizontal stress SH_(max),minimum horizontal stress Sh_(min),vertical stress S_(v))are calculated using density and sonic logs.The strike-slip stress type(SH_(max)>S_(v)>Sh_(min))is encountered.The key well which comprehensively includes the above seven properties is established.Geological and engineering(geomechanical)‘sweet spots'are then optimized from the key well by fully analyzing lithology,reservoir property,oilbearing potential,in situ stress magnitude and brittleness.It is hoped that the results support engineers'and geologists'decisions for the future exploitation of unconventional hydrocarbon resources.

Genesis of granular calcite in lacustrine fine-grained sedimentary rocks and its indication to volcanichydrothermal events: A case study of Permian Lucaogou Formation in Jimusar Sag, Junggar Basin, NW China

Granular calcite is an authigenic mineral in fine-grained sedimentary rocks.Core observation,thin section observation,cathodoluminescence analysis,fluid inclusion analysis,scanning electron microscope(SEM),and isotopic composition analysis were combined to clarify the genesis of granular calcite in the lacustrine fine-grained sedimentary rocks of the Permian Lucaogou Formation in the Jimusar Sag,Junggar Basin.It is found that the granular calcite is distributed with laminated characteristics in fine-grained sedimentary rocks in tuffite zones(or the transitional zone between tuffite and micritic dolomite).Granular calcite has obvious cathodoluminesence band,and it can be divided into three stages.Stage-Ⅰ calcite,with non-luminesence,high content of Sr element,inclusions containing Cos,and homogenization temperature higher than 170℃,was directly formed from the volcanic-hydrothermal deposition.Stage-Ⅱ calcite,with bright yellow luminescence,high contents of Fe,Mn and Mg,enrichment of light rare earth elements(LREEs),and high homogenization temperature,was formed by recrystallization of calcareous edges from exhalative hydrothermal deposition.Stage-IlI calcite,with dark orange luminescence band,high contents of Mg,P,V and other elements,no obvious fractionation among LREEs,and low homogenization temperature,was originated from diagenetic transformation during burial.The granular calcite appears regularly in the vertical direction and its formation temperature decreases from the center to the margin of particles,providing direct evidences for volcanic-hydrothermal events during the deposition of the Lucaogou Formation.The volcanic-hydrothermal event was conducive to the enrichment of organic matters in fine-grained sedimentary rocks of the Lucaogrou Formation,and positive to the development of high-quality source rocks.The volcanic-hydrothermal sediments might generate intergranular pores/fractures during the evolution,creating conditions for the self-generation and self-storage of shale oil.

Acid-base alternation diagenesis and its influence on shale reservoirs in the Permian Lucaogou Formation, Jimusar Sag, Junggar Basin, NW China

The diagenesis and diagenetic facies of shale reservoirs in Lucaogou Formation of Jimusar Sag were studied by means of microscopic observation and identification of ordinary thin sections and cast thin sections,X-ray diffraction,scanning electron microscope and electron probe tests.The results show that alkaline and acidic diagenetic processes occurred alternately during the deposition of Permian Lucaogou Formation in Jimusar Sag.The evolution of porosity in the shale reservoirs was influenced by compaction and alternate alkaline and acidic diagenetic processes jointly,and has gone through three stages,namely,stage of porosity reduction and increase caused by alkaline compaction,stage of porosity increase caused by acid dissolution,and stage of porosity increase and reduction caused by alkaline dissolution.Correspondingly,three secondary pore zones developed in Lucaogou Formation.The shale reservoirs are divided into three diagenetic facies:tuff residual intergranular pore-dissolution pore facies,tuff organic micrite dolomite mixed pore facies,and micrite alga-dolomite intercrystalline pore facies.With wide distribution,good pore structure and high oil content,the first two facies are diagenetic facies of favorable reservoirs in Lucaogou Formation.The research results provide a basis for better understanding and exploration and development of the Lucaogou Formation shale reservoirs.

Classification and control factors of pore-throat systems in hybrid sedimentary rocks of Jimusar Sag, Junggar Basin, NW China

Aiming at the complicated problem of the genesis of high-quality hybrid sedimentary rocks,the pore-throat systems,controlling factors and fluid mobility of hybrid sedimentary rocks in the Permian Lucaogou Formation in Jimusar Sag were examined.The results show that the hybrid sedimentary rocks contain 5 types of pore-throat system,intergranular(Type A),mixed intergranular-dissolved-intercrystalline(Type B),dissolved(Type C),mixed dissolved-intercrystalline(Type D)and intercrystalline(Type E)ones.The pore-throat systems are controlled by 3 major factors,the component content and arrangement(CCA)of hybrid sedimentary rocks,sedimentary environment and diagenesis.CCA controls the matrix support mode of hybrid sedimentary rocks,and therefore controls the types and changes of pore-throat system.The sedimentary environment mainly controls the macroscopic distribution of pore-throat system,i.e.,hybrid sedimentary rocks deposited in the near source and high-energy environment are characterized by high content of coarse-grained component,granular/interbedded-support mode,and development of Type A and Type B pore-throat systems.Hybrid sedimentary rocks deposited in the medium-energy environment far from source are characterized by dolomitic/mud support mode and Type C and Type D pore-throat systems.Hybrid sedimentary rocks deposited in low-energy environment far from source have mainly Type E and Type D pore-throat systems.Diagenetic processes such as compaction and calcite cementation make the proportions of Type A and Type C pore-throat systems decrease further.In the hybrid sedimentary process of sandy-mud,pore-throat system types show a change of"A→B→C→D",in that of dolomite-sand,pore-throat system types show a change of"A→C→D→E"or"B→D→E",and in that of dolomite-mud,pore-throat system types show a change of"D→E",which are affected in details by the contents of coarse-grain component,feldspar and dolomite.The reservoir with Type A pore-throats has the best physical properties and fluid mobility,and the reservoirs with Type D and Type E pore-throats have the poorest.The movable fluid distribution is related to the matrix support mode,and the larger pores in hybrid sedimentary rocks of dolomite/mud support mode have no obvious advantage in fluid mobility.The findings of this study provide a geological basis for evaluating and building reasonable interpretation model of hybrid sedimentary rocks sweet spot.

陆相混合细粒岩沉积微相及其对甜点的控制作用——以吉木萨尔凹陷芦草沟组为例

【目的】吉木萨尔凹陷二叠系芦草沟组发育了一套陆相混积沉积体系,混积细粒岩沉积微相类型及甜点储层分布规律等研究的不足制约了该区页岩油高效开发。【方法】综合岩心、露头、测井、X射线荧光光谱(X-Ray Fluorescence,XRF)元素录井、分析化验和试油试采等资料,采用岩相构型、沉积微相耦合分析和动静结合等方法,开展了沉积微环境及微相类型划分、沉积模式及其对甜点的控制作用等研究。【结果】(1)研究区主要发育浪成交错层理、水平层理、同生变形构造、黄铁矿、方解石条带、鸟眼构造和结核、缝合线构造、含生物化石和白云岩溶蚀孔8类沉积构造。研究区分为半深湖—深湖、混合浅湖和碎屑浅湖亚相,细分为半深湖泥、云坪、混合滩坝、混合浅湖泥、浅湖砂坝和碎屑浅湖泥等6种微相,不同微相沉积特征及其沉积机制差异明显。(2)建立了咸化湖泊相混积细粒岩沉积微相模式。芦一段自下而上从深湖—半深湖—浅湖演化过程,发育了浅湖砂坝、混合滩坝与云坪微相。其中,云坪呈连片状大范围分布,混合滩坝呈土豆状分布,发育程度较高,不同层规模有差异,浅湖砂坝发育程度一般,呈断续状局限分布,垂向上呈薄储集层与厚层泥岩叠置状。芦二段以浅湖为主,微相类型与芦一段类似,但形态、规模与叠置样式差异较大。云坪和混合滩坝发育数量和规模大大减小,浅湖砂坝则发育程度较高,呈大规模分散土豆状发育,垂向上呈厚层叠置状。不同位置剖面微相的叠置样式不同。(3)甜点段XRF元素分析显示,目的层沉积时为干燥炎热的半咸水环境到咸水过渡环境,古生产力水平较高;下甜点段为富氧环境,上甜点段则为厌氧亚还原到还原环境。(4)沉积微相控制了甜点分布和开发对策。混合滩坝微相Ⅰ类甜点发育程度高,非均质性弱,开发效果最好,采用大规模部署水平井平台化作业进行效益开发。云坪微相Ⅲ类甜点发育,非均质性强,开发效果一般,是后续接替区域。浅湖砂坝Ⅱ类甜点发育,整体分散状,连续性较差,非均质性强,开发效果较好。【结论】后续应在沉积微相空间分布精细研究基础上,参考核磁曲线参数部署水平井开发。

孔喉微观润湿性对页岩油赋存的控制作用——以准噶尔盆地吉木萨尔凹陷二叠系芦草沟组纹层状页岩为例

针对页岩不同类型储集空间中孔喉微观润湿性对其控制作用仍不明确的问题,以准噶尔盆地吉木萨尔凹陷二叠系芦草沟组页岩油储集层为例,综合运用扫描电镜、多阶热解、储集层定量荧光、核磁共振等分析方法,开展纹层状页岩储集空间特征及孔喉微观润湿性对页岩油赋存控制作用的研究。结果表明:芦草沟组主要发育“富火山物质+陆源长英质”纹层状页岩和“富火山物质+碳酸盐”纹层状页岩,其中“富火山物质+陆源长英质”纹层状页岩发育长石溶蚀孔隙和粒间孔隙,孔喉周缘矿物组分主要为长英质矿物组分,呈亲水性特征,主要控制游离态页岩油。“富火山物质+碳酸盐”纹层状页岩发育碳酸盐晶间孔和有机质孔隙,孔喉周缘矿物组分主要呈亲油性特征,控制吸附态页岩油。孔喉周缘主要为油润湿碳酸盐组分时,利于原油的聚集,但使得游离态的油含量比例下降。芦草沟组页岩游离油主要赋存于“富火山物质+陆源长英质”纹层组合的陆源长英质纹层中,成熟度较高、油质较轻。

吉木萨尔凹陷陆相页岩油储层测井定量解释

以吉木萨尔凹陷二叠系芦草沟组陆相页岩油为研究对象,采用岩芯刻度测井和数据挖掘两种方法,分上、下甜点分别建立物性、含油性、微观孔隙结构及岩石力学等参数的测井定量解释模型,在矿场应用中储层评价精度得到大幅度提高,均达到85%以上。特别是多条曲线反演的渗透率模型,数据挖掘方法优选出3条测井曲线,既反映了绝对孔隙性对渗透率的贡献,又考虑了微观孔隙结构改造对渗透率的制约,用自然伽马和声波时差曲线分别表征泥质含量和压实胶结作用对渗流路径及渗流阻力的影响,相较于单因素模型,其计算精度提高了25.6%。另外,由于井眼环境、孔隙流体的重力分异以及地层在不同方向上的各向异性,水平井与直井测井曲线存在一定的偏差,基于直井测井曲线响应特征与岩芯分析资料建立的解释模型不能直接应用于水平井的储层评价。针对以上难题,建立两种测量方式测井曲线的转换图版和公式,在测井曲线转换的基础上,可以对水平段的储层进行定量解释。

湖相细粒沉积岩中晶粒方解石成因及其对火山-热液活动的指示——以吉木萨尔凹陷二叠系芦草沟组为例

以准噶尔盆地吉木萨尔凹陷二叠系芦草沟组细粒沉积岩中晶粒方解石为研究对象,综合运用岩心观察、薄片观察、阴极发光分析、流体包裹体测试、扫描电镜、同位素组成分析等手段,对湖相细粒沉积岩中自生矿物的成因开展研究。结果表明:晶粒方解石呈层状分布于沉凝灰岩发育层段或沉凝灰岩与泥晶白云岩过渡层段的细粒沉积物中,方解石具有明显的阴极发光环带,可分为3期:Ⅰ期方解石不发光,含有较高的Sr元素,包裹体中包含羰基硫成分,均一温度超过170℃,由火山-热液喷流物质沉积形成;Ⅱ期方解石呈亮黄色光,含有较高的Fe、Mn、Mg元素,轻稀土元素富集,包裹体均一温度高,为热液喷流的钙质环边重结晶形成;Ⅲ期方解石呈暗橙色发光的环带,含有较高的Mg、P、V等元素,稀土元素无明显分异,包裹体均一温度低,为埋藏过程中成岩转化形成。晶粒方解石在垂向上规律性出现,并且其形成温度由颗粒中心向边缘降低,为芦草沟组沉积时期的火山-热液活动提供了直接证据。沉积期火山-热液活动有利于芦草沟组细粒沉积岩中的有机质富集,对优质烃源岩发育有正面效应,并且火山-热液喷流物质在演化过程中易形成晶间孔缝,为页岩油自生自储创造了条件。

致密油源储特征与聚集机理——以准噶尔盆地吉木萨尔凹陷二叠系芦草沟组为例

基于岩心观察、岩石样品薄片鉴定和X射线衍射矿物分析、烃源岩样品有机碳含量测定、岩石热解等方面的研究及储集岩高压压汞和核磁共振等分析,结合其埋藏及生烃史,分析准噶尔盆地吉木萨尔凹陷中二叠统芦草沟组烃源岩特征及储集岩特征,探究其源储组合及致密油聚集机理。芦草沟组烃源岩有机质类型总体上为Ⅰ型和Ⅱ型,TOC值平均为4.6%,整体上为优质烃源岩,处于低成熟—成熟阶段。烃源岩可划分为页岩、泥岩和粉砂质泥岩3类。芦草沟组储集岩整体上具有低孔低渗特征,高压压汞与核磁共振实验表明：纳米级孔喉（孔喉半径主体为50-500 nm）是储集空间的主体。储集岩可划分为泥质粉（细）砂岩、白云质粉（细）砂岩和砂屑白云岩3类。芦草沟组具有纵向上＂源储共生＂、横向上连续分布的源储组合关系,且烃源岩持续生烃。综合分析认为：自晚侏罗世至今,芦草沟组烃源岩大规模持续生烃增压为致密油聚集提供持续动力和物质供应,保障了石油在致密储集层中持续有效地充注聚集,形成大规模致密油资源。

吉木萨尔凹陷芦草沟组泥质岩类生烃潜力差异性分析

吉木萨尔凹陷芦草沟组为吉木萨尔凹陷最主要的烃源岩,该套烃源岩岩性多样,多为过渡性岩类,为了研究不同泥质岩类生烃潜力特征的差异性,以录井岩芯为基础,将泥质岩类划分为纯泥岩、砂质泥岩、灰质泥岩和云质泥岩四类,并主要从有机地球化学的角度对四类岩性泥岩的生烃潜力特征做出评价。结果表明,纯泥岩有机质丰度较云质泥岩、灰质泥岩、砂质泥岩略高;纯泥岩有机质类型最好,其次是灰质泥岩和云质泥岩,砂质泥岩干酪根类型最差。在此基础上,结合HI分析,认为纯泥岩生烃潜力最高,其次是云质泥岩、砂质泥岩,灰质泥岩生烃潜力最差。

烃源岩特征与生烃动力学研究——以准噶尔盆地吉木萨尔凹陷芦草沟组为例

准噶尔盆地吉木萨尔凹陷二叠系芦草沟组含有丰富的油气资源,其烃源岩主要有页岩、碳酸盐质页岩和粉砂质泥岩,它们均具有有机质丰度高、生烃潜力大、当前处于低成熟至成熟阶段、有机质类型以Ⅰ型和Ⅱ型为主的特征,在对其特征进行评价的基础上,选取中—低成熟度、有机质丰度较高的烃源岩进行开放体系条件下的热解实验和动力学模拟实验,进而研究烃源岩样品的生排烃特征。结果表明,芦草沟组烃源岩活化能主要为210 k J/mol;上述3种烃源岩中,页岩具有最高的生烃量和排烃效率,碳酸盐质页岩次之,而粉砂质泥岩的生烃量和排烃率均最低,但前两者却具有较高的滞留烃含量。综合前人的研究成果,最终认为芦草沟组烃源岩生烃增压作用是烃源岩排烃和致密油气聚集的主要动力,页岩和碳酸盐质页岩段是致密油勘探的目标层段。

利用电子束荷电效应评价致密储集层储集空间——以准噶尔盆地吉木萨尔凹陷二叠系芦草沟组为例

根据对致密储集层含油样品荷电现象的研究,提出基于电子束荷电效应的扫描电镜背散射截面二次成像法,研究储集层中残留油(未在实验真空条件下散失的原油)分布,并采用荷电显影剂注入法研究致密储集层孔隙连通性,形成有效储集空间的定量评价方法。对准噶尔盆地吉木萨尔凹陷二叠系芦草沟组致密油储集层样品进行研究发现,储集层含油样品强烈的荷电效应来源于孔隙中填充的残留油,有机质裂解生成的原油广泛存在于有机质附近孔隙中,贫有机质区也有残留油存在。背散射截面二次成像法分析面积大,能克服样品非均质性导致的分析区代表性差的问题。荷电显影剂注入法刻画孔隙连通性更加准确有效,芦草沟组致密储集层含油样品总面孔率为12.56%,总孔隙连通率达90%,储集空间有效性好。

准噶尔盆地吉木萨尔凹陷混积岩孔喉系统分类及控制因素

针对混积岩优质储集层成因复杂的难题,进行准噶尔盆地吉木萨尔凹陷二叠系芦草沟组混积岩孔喉系统、控制因素及流体可动性研究。结果表明,混积型储集层发育粒间孔喉系统(A型)、粒间-溶蚀-晶间混合孔喉系统(B型)、溶蚀孔喉系统(C型)、溶蚀-晶间混合孔喉系统(D型)和晶间孔喉系统(E型)5类。混积岩孔喉系统有3个主要主控因素:混积岩组分含量及排列方式、沉积环境和成岩作用。混积岩组分含量及排列方式控制孔喉系统类型及变化;沉积环境主要控制孔喉系统的宏观分布,近源、高能环境混积岩粗粒组分多,颗粒或互层型支撑,发育A型和B型孔喉;远源、中能环境混积岩过渡为云泥支撑,发育C型和D型孔喉;而远源、低能环境混积岩孔喉主要为E型和D型。压实和方解石胶结等成岩作用进一步破坏粒间、溶蚀孔喉占比。在砂泥混积时,孔喉系统类型为“A→B→C→D”变化,云砂混积时孔喉系统类型为“A→C→D→E”、或“B→D→E”变化,云泥混积时孔喉系统类型为“D→E”的变化,细节受偏砂粒、长石和白云石含量影响。其中,A型孔喉的物性及可动性最好,D型和E型最差;可动流体分布与支撑方式有关,云泥支撑型混积岩大孔可动优势不明显。研究成果为混积型储集层甜点评价及解释模型的合理构建提供了地质依据。图15表1参19。

湖相混积岩碳酸盐组分成岩作用及其孔隙结构特征——以新疆吉木萨尔凹陷二叠系芦草沟组为例

利用普通薄片、铸体薄片、X衍射、扫描电镜、高压压汞等测试分析资料,对研究区混积岩碳酸盐组分成岩作用、孔隙结构特征及其对渗透率的贡献等进行了研究。结果表明:在酸碱交替成岩环境中,碳酸盐组分成岩作用主要包括压溶作用、酸性溶蚀作用、白云石化与去白云化作用和重结晶作用等;芦草沟组混积岩储层目前处于中成岩阶段A2期;研究区碳酸盐岩类储层可分为泥晶白云岩和砂质/泥质泥晶白云岩,孔隙类型主要为溶蚀形成的粒间溶孔,长石颗粒发生溶蚀形成的粒内溶孔、晶间孔、微裂缝,以及少量的鲕粒间溶孔、生物格架内孔隙等类型,主要发育纳米级孔喉系统;2类碳酸盐岩类储层的主要渗流能力来源于0.01~0.20μm的纳米级孔喉。

新疆芦草沟组致密油赋存形式及可动用性评价

在对准噶尔盆地吉木萨尔凹陷二叠系芦草沟组致密油微观赋存形式、流动喉道下限及可动用性开展的研究中,利用铸体薄片、扫描电镜技术确定致密油在储集层中有可动油、束缚油两种赋存类型,可观察到薄膜状、颗粒状等六种微观赋存形式。利用水膜法、比表面法、启动压力梯度法等方法初步确定致密油流动喉道直径下限为100 nm;利用核磁共振、常规压汞、高压压汞技术定量评价致密油可动用程度主要集中在20%~40%。结论认识对研究区致密油储层评价、有效开发具有积极的指导作用。

吉木萨尔凹陷芦草沟组致密油地质特征及有利区分布

芦草沟组是现阶段准噶尔盆地致密油勘探开发的主要层位,为分析其地质特征及有利区分布,从“源-储”配置条件出发,通过有机质类型、总有机碳(total organic carbon,TOC)含量、成熟度、储集岩类型及孔渗性分析,结合成藏埋藏下限进行有利区划分。研究表明:芦草沟组有机质干酪根类型以Ⅰ型及Ⅱ_(1)型为主,TOC含量介于0.16%~13.86%,平均含量在3.0%以上,灰质泥岩平均含量为3.79%。有机质成熟度介于0.55%~1.35%,主体分布在0.8%以上,由西向东,有机质成熟度逐渐降低,具有分布范围广、厚度大的特点,包括上、下两个“烃源甜点层”,“下甜点”厚度大于“上甜点”层。储层岩石类型多样,优质储层集中于过渡性岩类中发育,白云质粉砂岩是最主要的储层岩石类型,孔隙结构以微细孔喉发育为主,为典型的低孔特低渗储层,孔喉连通性好,储层孔渗相关性良好。结合致密油成藏深度下限,划分上芦草沟组一段及二段有利勘探区,其中芦草沟组二段Ⅰ类有利区集中分布在凹陷东南部J32-H-J25-J32-J22井区,芦草沟组一段Ⅰ类有利区分布在凹陷中南部J251-J32-J174井区。

准噶尔盆地吉木萨尔凹陷二叠系芦草沟组致密油储层成岩作用与储集空间特征

利用岩芯观察、铸体薄片及荧光薄片鉴定,结合激光共聚焦显微镜、扫描电镜、X射线衍射、恒速压汞等分析测试手段,分析了准噶尔盆地吉木萨尔凹陷二叠系芦草沟组致密油储层成岩作用与储集空间特征及其相互关系。结果表明:吉木萨尔凹陷芦草沟组致密油储层主要发育碳酸盐岩类、陆源碎屑岩类、火山碎屑岩类和混积岩类等4种岩石类型,储集空间可分为次生溶孔、晶间孔和微裂缝3类;不同岩石类型经历了不同的成岩作用过程,发育了不同类型的储集空间。①碳酸盐岩类中,泥晶云岩成分单一,压实致密,胶结作用弱,储集空间以白云石晶间孔为主;随着粉砂质和凝灰质含量增加,压实作用变弱,长石和凝灰质发生强溶蚀,粉砂质砂屑云岩及凝灰质云岩的储集空间以长石粒内孔、铸模孔及凝灰质溶蚀孔为主。②陆源碎屑岩类中,凝灰质粉砂岩的压实作用中等,粉砂级长石颗粒粒内及边缘、分散状凝灰质溶蚀,且溶蚀孔中有大量的黏土矿物充填,储集空间以蜂窝状长石溶蚀孔、凝灰质溶蚀孔为主;而云质泥岩压实作用强,溶蚀作用不发育,仅可见晶间孔及微裂缝。③火山碎屑岩类中,粉砂质凝灰岩、云质凝灰岩压实作用中等,长石、凝灰质易溶,但胶结物种类较多,储集空间以次生溶蚀孔为主,发育少量的晶间孔。

吉木萨尔页岩油“甜点”预测方法

针对吉木萨尔凹陷二叠系芦草沟组页岩油"甜点"变化快、水平井钻遇率低等问题,从测井和地震2个方面展开分析。纵向上,将二叠系芦草沟组页岩油"甜点"分为上"甜点"和下"甜点"2个部分,类型上划分为Ⅰ、Ⅱ、Ⅲ共3类,并明确了上、下"甜点"的地震反射特征。在此基础上,通过敏感参数交会分析,确定了基于地震地质统计学模拟的"甜点"预测方法,预测精度得到了有效提高,预测"甜点"识别厚度由前期的20 m提至6 m,"甜点"钻遇率由87%提高至92%以上,从而实现了完钻水平井规模压裂及高效开发。通过上述研究,形成了一套针对陆相页岩油"甜点"的地震预测方法,并在生产实践中得到了验证,为页岩油水平井高效开发提供了技术支撑。

吉木萨尔凹陷芦草沟组致密油储层初步研究:岩性与孔隙特征分析

通过岩心观察、薄片鉴定、电子探针观测，结合野外剖面及测井和地震等资料，分析吉木萨尔凹陷芦草沟组致密油储层岩性与孔隙特征。结果表明致密储层段由呈韵律互层产出的白云岩类／粉砂岩类与泥岩类构成，一般由3-5个韵律组成，具有一定的非均质性。储层岩石类型主要为白云质粉砂岩，粉砂质白云岩、砂屑白云岩以及泥晶白云岩。其中白云质粉砂岩／粉砂质白云岩分布最广，为芦草沟组上、下储层段（“甜点”）最主要储集岩，砂屑白云岩只分布于上储层段，泥晶白云岩以薄的夹层形式分布于上、下储层段。电子探针微区观测表明，储集空间以溶蚀型孔隙为主，孔径大小从几μm到30μm，可分为粒间／晶间溶孔、粒内溶孔以及部分裂缝型孔隙，发生溶蚀作用的矿物以钠长石为主，白云石次之。定量分析表明，白云质粉砂岩／粉砂质白云岩主要由钠长石、白云石以及少量钾长石等矿物组成，砂屑白云岩主要由微晶白云石和少量钠长石等矿物组成，泥晶白云岩主要由微晶白云石和少量石英、钠长石等矿物组成。

准噶尔盆地吉木萨尔凹陷东斜坡二叠系梧桐沟组储层特征及影响因素

依据储层地质学的基本理论和研究方法,综合运用钻井、测井以及分析化验资料,对准噶尔盆地吉木萨尔凹陷东斜坡二叠系梧桐沟组进行了储层特征研究和影响因素分析。研究表明,储层孔隙度相对较高,而渗透率相对较低;孔喉类型主要为中孔-细喉型,且连通性相对较差;储层物性的影响因素为沉积相和成岩作用,其中压实作用是最主要的减孔因素,胶结作用是造成储层渗透率低的主要原因;相对优质储层发育的有利区带为辫状河三角洲平原的辫状河道砂体和辫状河三角洲前缘的水下分流河道砂体。