High-production oil flow was obtained from Lower Cretaceous Qingshuihe Formation in Well Gaotan-1,which is located in the southern margin of Junggar Basin.The result proves that high-quality conglomerate reservoirs are developed in Qingshuihe Formation.In this paper it analyzes the rock minerals,physical properties,pore structure and diagenesis of the conglomerate of Qingshuihe Formation in Gaoquan structure zone,Sikeshu sag,by using cores and thin section data,porosity-permeability analysis and X-ray diffraction whole rock mineral analysis.The main controlling factors of high-quality conglomerate reseroirs were analyzed based on the result.The studies show that the tuffaceous gravels are the major content of the reservoir.The content of sandy grains is typically less than 50％.Based on the contact relationship of the gravels and the content of sandy grains,the conglomerate can be divided into grain supported conglomerate and matrix supported conglomerate.The reservoir space is strong in heterogeneity,which is dominated by primary pores.The development of reservoir space is affected by a variety of diagenesis,among which physical compaction is the major contributor to the porosity loss.The conglomerate reservoir has undergone the burial process of early long-term shallow burial and late rapid deep burial,and is currently in the mesogenesis stage A.The forming of high-quality conglomerate reservoir derives from the following controlling factors.Conglomerate from underwater distributary channels in fan-delta front is the foundation to form high-quality reservoir.Low geothermal gradient and the the burial process of early long-term shallow burial and late rapid deep burial are key contributors to the formation of the reservoir.The alkaline diagenetic environment in the early stage of diagenesis and later acid diagenetic environment,as well as the overpressure are also important to the formation of the reservoir.

为探讨大气淡水对不整合面上覆地层的渗滤效应,利用地震—地质综合剖面、储层物性、油—水等流体地球化学参数及试油、试采等资料,综合分析与不整合面有关的地层结构及压实—离心流分布特征,揭示了在"T/C-P不整合双地层结构"控制下,大气淡水通过压实—离心流方式对T/P不整合面上覆地层进行垂向渗滤,导致玛东斜坡区三叠系百口泉组油气充注程度较低.结果表明:玛东斜坡区T/P不整合面之上的百口泉组压实—离心流渗滤带的流体势方向与重力势方向相反,其成因与百口泉组底部富泥砂砾岩岩相及伴生的润湿水相的毛细管 自吸作用密切相关;大气淡水主要沿着T/P不整合面之上百口泉组富泥砂砾岩内部的微细孔喉向上渗滤,形成 自下而上流动的压实—离心流;压实—离心流垂向渗滤深度约为45 m,平面延伸距离约为28 km;压实—离心流的逆重力势方向流动特征导致百口泉组油气充注程度整体较低,油气主要富集于砂层组中上部物性较优的贫泥砂砾岩储层中.最后,"根据T/C-P不整合双地层结构"的压实—离心流渗滤作用与油气富集特征确定百口泉组油层测井定量识别标准为lgRT＞1.4 Ω·m(电阻率RT＞25 Ω·m)、纵波阻抗1MP＜9000 g·cm-3·m·s-1;利用RT-IMP联合约束油层定量预测图板预测了夏子街扇东翼(面积为98 km2)、玛东盐北扇(面积为104 km2)两个油气富集区.

准噶尔盆地腹部八道湾组是侏罗系潜在的勘探接替领域.通过分析盆1井西凹陷八道湾组低位体系域砂体形成条件、沉积特征,结合成藏条件研究,提出了坳陷湖盆坡折之下发育低位体系域砂体,低位体系域砂体成藏条件优越:①盆1井西凹陷八道湾组发育1个完整的三级层序,凹陷周缘发育坡折,来自东部物源体系的辫状河三角洲向凹陷方向进积,在坡折之下的凹陷区卸载沉积物,为凹陷区低位体系域砂体的发育创造了条件.②盆1井西凹陷八道湾组发育低位体系域砂体,低位体系域砂体呈砂泥互层,侧向与三角洲平原河漫滩泥岩接触,顶底板和侧向遮挡条件较好,岩性圈闭条件优越,具有形成规模岩性圈闭群的条件.③盆1井西凹陷发育低孔特低渗低位体系域砂岩储层,局部发育的微裂缝改善了储层物性;凹陷发育二叠系风城组和下乌尔禾组2套烃源岩,烃源条件较好.④盆1井西凹陷周缘发育深浅2组断裂,在垂向上沟通八道湾组低位体系域砂体与二叠系烃源岩,有利于油气聚集成藏,勘探潜力大,为准噶尔盆地下一步天然气规模发现的有利勘探领域.

准噶尔盆地南缘侏罗系—白垩系储集层中裂缝较发育,本文基于地表露头、岩心、薄片和测井等资料,运用工业CT、激光共聚焦、扫描电镜等技术手段,系统研究了储集层多尺度裂缝类型、分布特征及成因,并对裂缝形成的控制因素进行了分析,认为南缘侏罗系—白垩系储集层裂缝可分为三级,分别是Ⅰ级宏观裂缝、Ⅱ级微细裂缝、Ⅲ级显微裂缝,再根据裂缝长度和成因将Ⅰ级宏观裂缝分为Ⅰ1,Ⅰ2两类,Ⅲ级显微裂缝分为Ⅱ1,Ⅲ2两类.研究结果表明:由天山造山带到盆地内部Ⅰ级宏观裂缝发育程度由强到弱,裂缝密度由第1排的1.6条/m到第3排的0.8条/m;Ⅱ级微细裂缝主要发育在各构造带的砂岩储集层中;Ⅲ级显微裂缝主要发育在第1排构造带的砂砾岩储集层中和北部斜坡带的砂岩储集层中.南缘侏罗系—白垩系储集层裂缝发育程度受构造应力、储集层岩性及岩矿组成、储集层厚度等因素控制.构造应力强则裂缝发育程度高,单层厚度较薄的细砂岩、中砂岩较粉砂岩、粗砂岩和砂砾岩更易发育裂缝.长英质碎屑颗粒、碳酸盐胶结物含量高的储集层更易发育裂缝.

为了明确坳陷湖盆古地貌对沉积体系的控制作用,认识沉积体系展布规律,优选下一步勘探领域,以准噶尔盆地中部侏罗系三工河组二段为例,采用地层厚度法恢复了古地貌,细化了古地貌单元,并通过岩芯观察,识别了沉积微相,在此基础上,通过古地貌单元与沉积微相叠合分析,提出了坳陷湖盆沉积期古地貌对沉积体系、沉积微相和岩性圈闭的形成具有重要的控制作用.研究结果表明:准噶尔盆地中部三工河期为隆凹相间的古地貌格局,具有水下古低凸、水下古沟槽、古坡折和水下古平台等4类古地貌单元,发育湖泊-三角洲沉积体系,可进一步识别出水下分流河道、分流间湾、席状砂和砂质碎屑流微相.水下古沟槽充填水下分流河道微相砂体,水下古低凸主体部位发育分流间湾相泥岩,古坡折之下的水下古平台发育砂质碎屑流砂体.水下古低凸翼部发育的水下分流河道砂体向低凸方向超覆尖灭,水下古平台发育的砂质碎屑流砂体呈"泥包砂"结构,储层性质较优,岩性圈闭条件好,成藏条件优越,为下一步最有利勘探领域.

准噶尔盆地玛湖凹陷二叠系风城组碱湖型页岩油资源丰富,是准噶尔盆地非常规油气勘探的重要领域.利用岩心、岩石薄片、X射线衍射、电子探针和扫描电镜等资料,研究了玛湖凹陷二叠系风城组页岩油储层的成岩作用、储集空间特征及其相互关系.结果表明:风城组页岩油储层包括粉砂岩类、泥页岩类、白云岩类等3类岩石;储集空间类型有残余粒间孔、溶蚀孔、晶间孔、泄水缝、层理缝和构造缝;不同类型岩石经受的成岩作用有变化,导致了差异化的储集空间发育特征.认为以微米级残余粒间孔及长石溶孔为主要储集空间的粉砂岩类物性最好,孔隙结构最优,是玛湖凹陷风城组页岩油最重要的"甜点"储层类型.风城组储层中普遍含凝灰质火山物质,火山玻璃的脱玻化与重结晶形成的晶间孔以及构造活动造成的破裂缝在3类岩石中均不同程度地发育,造成研究区页岩油储层常具有孔-缝双重介质特征.

准噶尔盆地玛湖凹陷西斜坡区百口泉组发育低孔、低渗强非均质性砂砾岩储层,溶蚀作用显著,但溶蚀作用影响因素不明确.采用质量浓度2％的乙酸溶液代替埋藏条件下的有机酸,开展开放体系、高温高压溶蚀物理模拟实验.为研究有机酸溶蚀砂砾岩后储层物性、孔隙结构的变化,以及温度和泥质含量对溶蚀作用的影响,开展了两组溶蚀实验.结果表明:1)开放体系高温高压条件下,有机酸溶蚀砂砾岩中长石组分可以有效提高储层孔隙度以及渗透率,溶蚀显著增加半径10μm左右的小孔隙和小喉道,对渗透率的改善效果尤为显著;2)有机酸溶蚀模拟实验反应后溶液中析出的主要阳离子(Al3+、Si4+、Na+、K+、Ca2+)表明斜长石和钾长石发生溶蚀,并且温度越高,泥质含量越低,长石溶蚀量越大.综合分析认为,在开放体系下,较高地温、较低泥杂基含量的砂砾岩有机酸溶蚀增孔效率更高,这一认识可为下一步寻找有利储层发育区提供理论支撑.

准噶尔盆地南缘中段HT1井在白垩系清水河组底部砂岩储层中获得了高产气流,证实该套储层是一套相对优质储层.利用薄片观察、孔渗分析、压汞分析、场发射扫描电镜观察、激光共聚焦显微成像等多种分析测试手段,对清水河组砂岩样品开展了岩石矿物、物性、孔隙结构等分析,并结合埋藏史开展成岩演化研究.结果表明:①南缘中段清水河组储层岩石类型主要为长石岩屑砂岩,结构成熟度较高.②储层中胶结物含量中等,残余粒间孔和裂缝发育,现今处于中成岩B阶段.③相对优质储层的形成受控于四大因素:远源辫状河三角洲沉积体系使砂岩的结构成熟度较高;较低的地温梯度减弱了砂岩热压实效应;深层流体膨胀作用导致的异常高压有利于粒间孔隙的保存;裂缝提高了砂岩储层的渗流能力.

为明确准噶尔盆地南缘冲断带深层储集层特征,在露头剖面观测基础上,结合录井、微量元素及重矿物资料,对准噶尔盆地南缘侏罗系喀拉扎组沉积相标志、沉积相类型、物源方向、沉积相展布及沉积模式开展研究.研究区喀拉扎组主要发育冲积扇和辫状河三角洲2种沉积相,平面上发育3个大型沉积体系,自西至东分别是齐古断褶带中段的冲积扇—辫状河三角洲沉积体系、齐古断褶带东段头屯河地区的辫状河三角洲沉积体系和阜康断裂带的辫状河三角洲沉积体系;纵向上,喀拉扎组表现为进积沉积序列,自下而上发育4个沉积旋回.喀拉扎组沉积相类型及平面展布主要受侏罗纪晚期天山造山带活动的控制,3个大型沉积体系在盆地内部形成了厚度超过200 m的砂岩储集层,特别是辫状河三角洲前缘砂体分选好,厚度大,分布面积广,可与深层大型背斜构造相匹配,成为有利的勘探目标区.

为了明确准噶尔盆地白垩系清水河组是否发育低位体系域砂体、低位体系域砂体是否具有勘探潜力,对阜康凹陷清水河组低位体系域砂体形成条件、沉积特征和沉积模式进行了分析,并对成藏条件进行研究.结果 表明:准噶尔盆地白垩系清水河组底部为三级层序界面,且阜康凹陷沉降中心附近发育多级坡折,为低位体系域砂体发育创造了条件,并提出大型坳陷湖盆坡折之下发育多期低位体系域砂体,岩性圈闭条件优越.低位体系域砂体厚度大、面积广、储层优,侧向封堵条件优越,且研究区发育深层和浅层两组断裂,在垂向上构成"Y"形组合,可沟通烃源岩和低位体系域砂体,证实研究区低位体系域砂体成藏条件优越,为下一步岩性油藏最有利勘探领域.

Santanghu basin in Northwest China is a petroliferous basin. In recent years, researchers have discovered tuff tight reservoirs in the Tiaohu formation of Malang sag. Thin section, scanning electron microscopy, electron probe, X-ray diffraction, and CT scanning analysis are applied to reveal the petrological characteristics, physical properties, and pore texture of tuff tight reservoirs. Major controlling factors of the formation of high-quality tuff tight reservoirs are also discussed. The results show that the tight reservoir is intermediate-acidic crystal-vitric tuff. The main component of tuff reservoir is felsic vitroclastic, followed by crystal fragment and a small amount of bioclast, and trace clay content. Mercury injection and CT scanning show that the tight oil reservoir is characteristic of medium-high porosity, ultra-low permeability, and high oil saturation, which is controlled by its pore texture. There are four types of micropores in tuff reservoir, among which the principal reservoir space is devitrified micropores and crystal fragment dissolution micropores. Micropores are distributed universally in the tight oil reservoir, and the throat is nano-scale throat. It is considered that the tuff in the study area is formed by the deposition of volcanic ash in stable water after long-distance drifting in the air. The formation of high-quality tuff tight oil reservoir derives from 3 key factors: (1) shallow-semi-deep lacustrine environment, which is less affected by terrigenous input; (2) intermediate-acidic volcanic ash which forms the tuff reservoir; (3) devitrification and dissolution during the diagenesis.

Jurassic Sangonghe sandstones (J(1)s) are prolific oil reservoirs in the Mosuowan area of the Junggar Basin. However, hydrocarbon exploration in deep-buried sandstones with depths > 4km would be highly risky due to the reservoir quality. Analysis of diagenesis can provide insight into controls on reservoir quality, which helps to reduce exploration risks and predict reservoir quality in perspective area. Routine core analyses and petrographic data were used to investigate diagenesis and their impact on reservoir quality of the J(1)s sandstones. J(1)s sandstones are mostly feldspathic litharenite and litharenite with an average composition of Q(36)F(20)R(44). A wide range of porosity from 5.3 to 16% (average 11.6%) and permeability from 0.14 to 566mD (average 6.27mD) indicate that the reservoir has strong heterogeneity. Eodiagenetic events are characterized by mechanical compaction, chlorite grain coating, and calcite cementation. Mesodiagenetic events include feldspar dissolution, quartz overgrowth, kaolinite and illite precipitation, and ferrocalcite cementation. Mechanical compaction played a more prominent role in the reduction of porosity than cementation. Grain size and detrital component influence diagenetic compaction process which resulted in the difference in sandstone porosity reduction and variance in porosity-permeability correlation. Secondary porosity was generated mainly by feldspar dissolution. However, mass-balance calculations suggest almost equilibrium in aluminum of the system, indicating that burial dissolution contributes few to net porosity increase. Coarser-grained sandstones with more rigid grains and fewer ductile rock fragments are subject to less mechanical compaction which can preserve more intergranular pores. The coarser-grained sandstones have better reservoir quality than finer sandstones, which can be reflected by the higher slope in the porosity-permeability correlation.

为探讨沉积间断时间、风化古土壤层发育程度、高放射性砂砾岩、低含油饱和度油藏之间的成因联系,以碎屑锆石U-Pb同位素、孢粉化石、自然伽马能谱等资料综合分析为基础,对玛南地区T1 b/P3w,P3w/P2w两大不整合面分隔的T1b,P3w,P2w这3套地层中的高放射性砂砾岩分布差异开展对比分析,认为高放射性厚层块状砂砾岩有利于低含油饱和度油藏的形成.研究结果表明:古气候、沉积间断时间共同控制风化古土壤的发育规模及吸附放射性元素的能力,二叠系沉积、三叠系沉积之间约4.2 Ma的较长沉积间断强化了母质、气候、生物等因素在古土壤形成过程中的作用强度及影响程度,最终在T1b/P3w不整合面之下形成规模风化古土壤层.风化古土壤层中钍(Th)、铀(U)、钾(K)3种放射性元素的垂向淋滤下渗形成低放射性风化古土壤层,其中,铀(U)元素的垂向淋滤下渗是在下伏P3w地层中形成高放射性砂砾岩带的主要原因;高放射性砂砾岩带内部发育高放射性砂砾岩、常规砂砾岩、沉积泥岩、渗滤泥岩4种岩性结构单元.该带的整体高放射性背景影响着内部沉积泥岩、渗滤泥岩的测井响应.以GR值66 API为界可以区分出常规砂砾岩单元、高放射性砂砾岩单元.较之于常规砂砾岩单元,高放射性砂砾岩单元的RT值(14.52～22.79Q·m,均值为17.66 Ω·m)相对较低,其原因与高放射性砂砾岩单元含油饱和度(41％～53％,均值为44％)相对较低有关;高放射性砂砾岩带主要分布于构造高部位断裂带的厚层块状砂砾岩中,为低含油饱和度油藏的形成奠定物质基础及储层条件.

利用岩石薄片、铸体薄片、X射线衍射全岩矿物分析、扫描电镜、物性等资料,对准噶尔盆地莫北—莫索湾凸起下侏罗统八道湾组致密储集层岩石学特征、物性特征和成岩作用特征进行研究,并在此基础上分析了八道湾组储集层致密化机理.结果表明,八道湾组储集层具有低成分成熟度、低填隙物含量和高塑性岩屑含量的特征,经历了强压实作用、弱胶结作用和普遍的溶蚀作用;压实作用强是八道湾组储集层致密化的最主要因素,而八道湾组煤系酸性成岩流体造成的强流体压实效应,以及高塑性岩屑含量造成的强静岩压实效应是导致八道湾组强压实作用的主要原因;中粗砂岩—粗砂岩塑性岩屑含量低,虽然流体压实效应较强,但静岩压实效应弱,储集层物性好,是最有利的储集砂体.

近年来对扇三角洲相带及沉积模式的研究有力地支撑了油气勘探大发现,因而扇三角洲类型细化研究受到越来越多的重视.依据23口井岩心资料、大量录测井资料、古地貌和地震等资料,分析了准噶尔盆地玛湖凹陷上乌尔禾组河控型扇三角洲沉积特征和控制因素.结果表明:(1)玛湖凹陷上乌尔禾组发育3大类、8亚类、23细类岩相类型,牵引流成因的岩相比例高,砾石间多为砂质充填或是半充填;(2)可分为辫状河道、碎屑流带、水下分流河道、河口坝等10个微相,以辫状河道与水下分流河道微相为主;(3)河控型扇三角洲平面形态多呈长轴扇形,玛湖凹陷上乌尔禾组发育中拐、克拉玛依、白碱滩、达巴松4个长轴形扇体;(4)河控型扇三角洲的沉积受潮湿气候和古地貌因素控制.在此基础上,建立了上乌尔禾组河控型扇三角洲沉积纵向相带序列模式和沉积模式,可为扇三角洲具体类型的判别以及类似盆地的油气勘探提供地质依据.

为了进一步了解玛湖凹陷下二叠统风城组沉积环境,通过现代碱湖和主要碱矿进行调研,系统梳理了现代碱湖沉积特征,并与风城组沉积特征进行了对比研究,提出了现代碱湖沉积对玛湖凹陷风城组沉积环境具有可对比性.研究结果表明:玛湖凹陷风城组沉积期为一大型碱湖盆地,与世界上典型碱湖特征基本相近,自生矿物、沉积组合与演化过程大致相同,为形成于半干旱气候环境的闭流盆地,含碱层段一般为浅水环境成因,是碳酸盐型湖水蒸发浓缩的产物,与碱层互层的暗色细粒岩石不全为深水沉积产物.

为了弄清准噶尔盆地凹陷区是否发育有效砂体、岩性圈闭是否落实,基于岩心观察、重矿物分析、储层表征和地震反射特征分析等方法,分析了该盆地盆1井西凹陷下侏罗统三工河组二段(以下简称三二段)古地貌、沉积微相、储层性质和含油气性,评价了砂质碎屑流砂体的岩性圈闭条件,明确了准噶尔盆地三工河组下一步天然气勘探的方向.研究结果表明:①盆1井西凹陷周缘三二段发育坡折带,坡折带之上三角洲前缘砂体发育,在燕山期构造活动的触发下,滑塌至坡折带之下的半深湖形成砂质碎屑流砂体;②砂质碎屑流砂体厚度大,垂向上具有“泥包砂”结构,侧向与前缘相砂体之间存在泥质分隔带,封堵条件较好,岩性圈闭条件优越;③砂质碎屑流砂体储层物性好,属于中等—较好的储集层,砂质碎屑流砂体整体含油气性较好.结论 认为:①准噶尔盆地三工河组发育砂质碎屑流砂体,岩性圈闭条件优越,具有重要的油气勘探意义;②基于该研究成果,通过新钻井已取得了油气勘探重大突破,证实坡折带之下砂质碎屑流砂体岩性油气藏成藏条件优越,是该区下一步最有利的天然气勘探新领域.

浊沸石是准噶尔盆地二叠系砂砾岩储层常见的胶结物,成岩成储作用复杂.以玛湖凹陷东斜坡下乌尔禾组为例,分析岩心、铸体薄片资料,采用X线衍射、电子探针能谱及RT—DEN联合约束反演等方法,构建含浊沸石砂砾岩储层测井定量识别图版,优选浊沸石溶孔砂砾岩储层油气富集区.结果表明:对于更靠近研究区湖盆中心的P2 w31油层,规模浊沸石溶孔储层的发育程度及油气富集条件更佳.含浊沸石砂砾岩储层预测标准为电阻率不小于20.0Ω·m,密度不大于2.46 g/cm3,按照"垂向上,累计含浊沸石砂砾岩储层厚度大于6 m;平面上,单块面积大于40 km2;含浊沸石砂砾岩储层厚度—主成藏期古鼻凸—通源断裂综合配置佳"的约束原则,P2 w31油层优选规模浊沸石溶孔油气富集区块4个、总面积201 km2.其中,B、C区块为Ⅰ类潜在油气富集区;A区块西侧低井控区及D区块为Ⅱ 类潜在油气富集区.该结果为玛湖凹陷斜坡区及其他盆地浊沸石溶孔储层定量预测提供借鉴.

准噶尔盆地南缘四棵树凹陷白垩系清水河组底部砂岩储集层获得了日产千方的高产油气流,证明该套储集层是一套优质储集层.在对多条露头剖面和多口钻井资料分析基础上,利用偏光显微镜、孔渗分析仪、激光共聚焦显微镜等实验仪器,对清水河组砂岩样品开展了岩石矿物、物性、孔隙结构等方面的分析,并结合埋藏史开展成岩演化研究.结果 表明,研究区清水河组砂岩主要为长石岩屑砂岩和岩屑砂岩,储集层杂基含量不高,胶结物含量中等,剩余粒间孔发育;清水河组砂岩储集层处于中成岩阶段A期,压实作用是主要减孔作用.综合分析认为,清水河组优质储集层的形成受控于早期长期浅埋晚期快速深埋、裂缝发育以及地层异常高压3个关键因素,早期长期浅埋晚期快速深埋的埋藏方式有助于储集层原生孔隙的保存;粒内微裂缝和层理缝共同发育有助于砂岩储集层中高效渗流通道的形成;地层异常高压有助于粒间孔的保存及裂缝的开启.

准噶尔盆地南缘齐古断褶带中-下侏罗统发育多套砂岩储集层.基于齐古断褶带露头剖面和钻井资料分析,利用偏光显微镜、孔渗分析仪、扫描电镜等实验仪器对中-下侏罗统砂岩样品开展了岩矿特征、成岩作用、成岩相、物性特征等方面的分析,并对储集层进行了分类和评价.结果 表明,齐古断褶带中-下侏罗统砂岩主要为长石岩屑砂岩和岩屑砂岩,结构成熟度中等,成分成熟度低;成岩作用主要有压实作用、胶结作用和溶蚀作用,可分为少杂基弱胶结成岩相、不稳定矿物溶蚀成岩相、碳酸盐矿物胶结成岩相和杂基充填-压实成岩相4种成岩相类型,成岩相直接影响了储集层物性,中-下侏罗统储集层可分为2大类6小类,部分含油气层为致密砂岩储集层.