DIAGENESIS AND RESERVOIR DEVELOPMENT OF SANDSTONES IN THE TRIASSIC REWAN GROUP, BOWEN BASIN, AUSTRALIA

The non-marine Lower Triassic Rewan Group in the Bowen Basin, Australia, is mainly composed of lithic arenites containing high proportions of volcanic rock fragments. Sublitharenites are also present. The arenites are cemented by abundant authigenic quartz, carbonates and clay minerals. Three separate lithostratigraphic intervals can be identified: a conglomeratic unit at the base; a sequence dominated by lithic arenites in the middle; and a section dominated by sub-litharenites at the top. Petrographically, the sandstones can be divided into a facies whose quartz content is greater than 75% on a QFR diagram; and a labile or lithic facies which contains less than 75% quartz. There is a progressive change in clay mineral assemblage from one petrofacies to the other.
The volcanic fragments have undergone rapid diagenetic alteration under low temperatures andpressures. Alteration started with pore-space reduction by compaction and was followed by pore-fill cementation. Solution at depth, however, has caused secondary porosity to develop. Differences in clay mineralogy and in the overall proportion of clay within the Rewan Group can be explained by differences in permeability and fluid flux, with high permeabilities occurring in the conglomeratic and sublitharenitic intervals. Porosity is best developed where early silicification has enhanced grain support and has minimised the effects of later compaction, and where clay minerals have been leached.     

准噶尔盆地西北缘下二叠统油气储层中火山物质蚀变及控制因素

通过岩心分析、显微镜下观察（常规、铸体薄片和扫描电镜）、岩石地球化学分析测试等技术手段,以准噶尔盆地西北缘下二叠统油气储层为实例,研究了火山岩、火山碎屑岩和火山岩屑质砂砾岩中的火山玻璃、火山碎屑、长石以及辉石、角闪石等火山物质的低温-埋藏蚀变作用。镜下观察发现,在含火山物质油气储层中,常见对储集空间具有重要影响的自生矿物主要有绿泥石、沸石（包括方沸石、片沸石和浊沸石）、方解石、钠长石和自生的石英。结合共生关系、元素组成和元素迁移,分析了自生矿物的微观特征和成因,建立了火山物质蚀变的成岩演化序列,可以概括为：①火山玻璃水化—蒙脱石化—沸石化及各种沸石的转化——钠长石化;②铁镁矿物影响的绿泥石化;③长石蚀变向绿泥石和方解石转化,后期发生钠长石化。在研究区,火山物质的蚀变和自生矿物的析出与中-基性的母岩物质组成密切相关,并受地层温度、压力、孔隙水的化学性质控制。研究火山物质蚀变的产物、蚀变过程及控制因素,能够明确含火山物质的油气储层质量差异机理,为优质储层预测提供科学的依据。     

垦利10-1油田沙河街组储层自生矿物及溶蚀作用对物性的影响

垦利10-1构造沙河街组发育多套含油砂岩储集体,这些砂岩储层内的成岩现象十分丰富。应用扫描电镜、岩石薄片、粘土矿物及物性资料,对该储层成岩矿物成分、结构和产状进行了分类及特征分析。研究发现:垦利10-1南区沙河街组油层中自生粘土矿物含量高,它们以孔隙充填形式或薄膜包裹颗粒形式堵塞粒间孔隙和喉道,使储层渗透率降低;油层中自生石英加大发育,颗粒表面及粒间孔隙被较完整的石英自形晶面所充填,使储层渗透率降低;油层中碳酸盐胶结-交代现象明显,这种矿物以菱面晶体产状充填粒间孔隙,对油层物性影响较大。而该储层中长石的强烈溶蚀又改善了油层的储集性能,使这一探区具有上亿吨级的储量规模。     

内蒙乌兰格尔地区上古生界砂岩的成岩作用

内蒙乌兰格尔地区的上古生界厚逾400m,大部分砂岩属于致密型低孔渗性的岩体。本文主要论述这些砂岩的成岩作用及其对储层孔渗性的影响。记砂岩具有四个成岩阶段:1.机械压实作用和早期胶结作用;2.碳酸盆的胶结作用和交代作用;3.溶蚀作用;4.晚期自生粘土矿物的形成和早期粘土矿物的重结晶作用。其中强烈的机械压实作用减少砂岩的孔隙,碳酸盆矿物的胶结作用尤其显著地减少了孔隙度和渗透率。但是,胶结物和部分颗粒的后期溶蚀作用是改善某些层段储集性能的有利因素。      

内蒙乌兰格尔地区上古生界砂岩的成岩作用

内蒙乌兰格尔地区的上古生界厚逾400m,大部分砂岩属于致密型低孔渗性的岩体。本文主要论述这些砂岩的成岩作用及其对储层孔渗性的影响。记砂岩具有四个成岩阶段:1.机械压实作用和早期胶结作用;2.碳酸盆的胶结作用和交代作用;3.溶蚀作用;4.晚期自生粘土矿物的形成和早期粘土矿物的重结晶作用。其中强烈的机械压实作用减少砂岩的孔隙,碳酸盆矿物的胶结作用尤其显著地减少了孔隙度和渗透率。但是,胶结物和部分颗粒的后期溶蚀作用是改善某些层段储集性能的有利因素。     

鄂尔多斯盆地东部下奥陶统碳酸盐岩埋藏成岩事件研究

鄂尔多斯盆地东部下奥陶统碳酸盐岩埋藏成岩事件主要有埋藏白云岩化、埋藏溶解作用、埋藏胶结作用、埋藏去白云岩化、有机质成岩作用和粘土矿物转化作用等.不同类型的埋藏成岩事件的产物和岩石学及地球化学特征各异,对油气藏的最终形成起着不同的作用.有机质成岩作用和埋藏溶解作用产生的埋藏溶蚀孔洞缝构成区内主要的油气储集场所;埋藏胶结作用及成岩自生粘土矿物的形成作用是区内成岩圈闭和复合圈闭形成的必要条件;埋藏白云岩化和埋藏去白云岩化可提供部分油气储集空间.上述诸埋藏成岩事件的相互叠加对油气的形成、运移、聚集、圈闭和保存具有重要意义.     

松辽盆地徐家围子地区火山岩储层主要次生矿物研究

以松辽盆地北部徐家围子地区深层火山岩储层为研究对象,通过对徐深气田 50 多口井深层火山岩岩心观察得出,该区岩石类型从基性、中性到酸性岩均有分布,以酸性岩为主。火山熔岩有玄武岩、安山岩、粗面岩和流纹岩等;火山碎屑岩包括凝灰岩、流纹质熔结凝灰岩、火山角砾岩和集块岩。 通过岩石薄片显微镜下鉴定发现,各种火山岩均见不同程度的交代作用,如绿泥石化、碳酸岩化、高岭土化及硅化等。交代作用形成的次生矿物如石英、长石、绿泥石、浊沸石、碳酸盐矿物及黏土矿物,多充填在气孔和裂缝中。对以上几种次生矿物特征作了详细描述,并根据热力学第三定律对石英、绿泥石和浊沸石的形成进行了热力学模拟。根据石英、绿泥石和浊沸石 3 种矿物形成的反应方程式,并结合地层水资料中 K⁺,Ca⁺,Na⁺,H⁺,（Fe,Mg）²⁺ 和（Fe,Al）³⁺ 等离子的浓度,分别计算出它们各自形成的平衡常数K,再根据热力学公式ΔG_（⁰_T）＝ -R·T·lnK计算出它们各自在不同温压条件下的吉布斯自由能变量ΔG_（P,T）。 通过比较ΔG_（P,T）的大小判断出 3 种矿物沉淀的先后顺序为绿泥石→石英→浊沸石,与镜下观察到的成岩顺序一致,为研究火山岩储层次生矿物的成岩演化提供了热力学依据。     

CONTROLS ON RESERVOIR DIAGENESIS IN THE LOWER GORU SANDSTONE FORMATION,LOWER INDUS BASIN,PAKISTAN

Sandstones in the Lower Cretaceous Lower Goru Formation in the Lower Indus Basin, Pakistan, are important reservoir rocks for oil, gas and gas‐condensates. For this study, nine metres of core from depths of more than 3400m from well X‐1 in the north‐central part of the basin were analysed for major variations in porosity and permeability in two Lower Goru sandstone units referred to as the Basal and Massive Sands. The Lower Goru Basal Sand was deposited in lower shoreface to inner shelf settings at the well location, while the Massive Sand was deposited in a middle to lower shoreface setting. In both units, intervals with moderate to good (> 15%) porosities alternate with intervals with very low porosity (<5%), and similar variations in core permeability were observed. In this paper, the reasons for this reservoir quality variation at well X‐1 are investigated. Specifically, the study addresses the influence of different clay types on reservoir porosity and permeability within the Lower Goru sands and the distribution and impact of hard cements such as calcite and quartz. A range of petrographical data is integrated including thin sections, whole rock and clay XRD results and SEM images, which together provide some insights into the causes of reservoir quality variation and into the paragenetic relationships between the authigenic minerals. Chlorite grain coats are present in the higher‐porosity sandstones and are interpreted to have inhibited the formation of quartz overgrowths. Dissolution of feldspar and volcanic rock fragments in both the Basal and Massive Sands has contributed to an increase in overall porosity at well X‐1. Relatively low porosity intervals in the Massive Sand are associated with the absence of chlorite grain coats and the presence of abundant quartz overgrowths. By contrast, low porosity intervals in the Basal Sand have undergone early poikilotopic calcite cementation. The formation of authigenic illite resulted in a significant decrease in permeability in both the Basal and Massive Sands. Chlorite and kaolinite also reduced the permeability. The chlorite originated mainly from the dissolution of volcanic rock fragments or from precursor depositional berthierine clay. The transformation of K‐feldspar to illite is suggested to be the main reaction responsible for the formation of both authigenic illite and quartz overgrowths in the two reservoir units; the observed pressure solution will also have contributed to development of quartz overgrowths.     

中国含油气盆地砂泥岩黏土矿物的组合类型

通过对国内15个含油气盆地10余万块砂，泥岩样品黏土X射线衍射分析资料和地质特征的分析，将我国含油气盆地的黏土矿物组合划分为两大类共12种，分别代表不同的沉积和成岩环境，常见黏土矿物组合类型中，组合1～5分别代表早成岩A、B及晚成岩A、B、C等5种不同的成岩环境，组合6常见于高渗透储集层或煤系地层，组合7多见于生油凹陷中的低渗透储集层；特殊黏土矿物组合类型中，组合8反映膨润土夹层，组合9层映造山带深部地层不断剥蚀的快速堆积环境，组合10反映基性火山岩物源，组合11反映快速剥蚀堆积或富钾的沉积环境，组合12反映于旱富镁的沉积环境。     

吉木萨尔凹陷仓房沟群火山砂岩的典型成岩反应及其物性特征

近地表碳酸盐化和浅埋藏水化水解,使火山砂岩在压实前固结,其中的粒间孔隙被以蒙脱石为主的自生粘土矿物充填或分割。决定孔隙水性质和形成自生粘土矿物及沸石等离子,来自火山砂岩本身。火山砂岩的典型成岩反应是水化水解和脱水反应,决定了孔隙水的性质、成岩矿物组合和储层的物性。     

CO2与砂岩相互作用机理与形成的自生矿物组合

当CO₂以天然方式或人工方式注入到含水砂岩时,成岩流体将转变成弱酸性流体,引起宿主砂岩中不稳定矿物(如碳酸盐、长石)的分解和新矿物的沉淀,进而使砂岩的孔隙度、渗透率和地层水地球化学特征发生改变。CO₂注入砂岩后,仅有少量CO₂溶解于水中以气体形式存在,大部分CO₂以次生矿物形式(如方解石、白云石、菱铁矿等)被“固化”在宿主砂岩中,形成的典型自生矿物组合为:片钠铝石±含铁碳酸盐矿物±其它碳酸盐矿物组合和铁白云石+高岭石+自生石英组合。其中,前一种矿物组合是示踪CO₂运移、聚集的典型自生矿物组合。CO₂与砂岩相互作用机理及形成的自生矿物组合研究不仅拓宽了沉积盆地中流体-岩石相互作用研究领域,揭示了深部流体与浅部储集层之间、浅部烃源岩或其它岩石与附近储集层之间的物质转移,而且为储集砂岩品质评价、CO₂气藏(田)预测、CO₂地下储存等研究提供了基础地质信息。     

三塘湖盆地马朗凹陷牛圈湖—牛东构造带上石炭统火山岩黏土矿物特征及其对储层物性的影响

三塘湖盆地马朗凹陷牛圈湖—牛东构造带上石炭统哈尔加乌组和卡拉岗组发育低孔、特低渗强非均质性火山岩储层.基于黏土矿物类型、含量、赋存状态、分布特征及其成因与转化的系统分析,讨论了黏土矿物对火山岩储层储集物性的影响.上石炭统火山岩储层为低孔、特低渗储层,主要发育气孔、半充填杏仁孔、晶间孔、粒间孔等原生孔隙和微晶溶孔、基质溶...     

四川盆地上三叠统砂岩成岩作用及其对孔隙的控制

四川盆地上三叠统不仅是一个含煤层系,也是一个有良好前景的含油(气)组合,已在多处获得工业油、气井(藏)。储集岩主要是须家河组的须二段和须四段的砂岩,其次是须三段、须五段和小塘子组的砂岩。近6000块砂岩物性分析,平均孔隙度6.8%,渗透率0.7毫达西,通常小于1毫达西。对某气田70余块砂岩所做的压汞分析,平均孔喉直径0.566微米。显然,它们主要属于细-微毛细管孔隙类型。何以形成如此低的孔、渗性呢?与其沉积环境和成岩作用有关。     

英买力沥青砂岩自生伊利石K-Ar测年与成藏年代

利用沉降、离心和微孔滤膜真空抽滤相结合的综合分离提纯技术,分别提取不同粒级的自生伊利石进行K-Ar年龄测定,据此对塔里木盆地英买力地区志留系沥青砂岩油气藏的成藏年代进行分析与研究,并在盆地内进行对比.除局部地区外,英买力志留系沥青砂岩中的黏土矿物均主要为伊利石/蒙皂石(I/S)有序间层,具明显的自生成因特征,属自生伊利...     

七里村油田长 6 油层组储层特征及孔隙演化

通过孔渗、压汞、薄片鉴定和扫描电镜等分析资料,以鄂尔多斯盆地七里村油田三叠系延长组长 6油层组储层为研究对象,系统开展了储层特征及孔隙演化等研究。 结果表明：研究区长 6 油层组储层砂岩以细粒长石砂岩为主,矿物成分成熟度低,结构成熟度高;储层呈现出低孔、低渗-特低渗特征。 长 6 储层砂岩总体处于晚成岩 A 期,其经历了强烈的成岩作用改造,孔隙度与渗透率相关性较差。 影响储层物性及孔隙演化的主要因素是机械压实作用、溶蚀作用及胶结作用。 机械压实作用在早成岩期对储层物性影响最大,可使粒间孔隙急剧减小,物性变差。 主要的胶结类型为碳酸盐胶结、石英次生加大及黏土矿物胶结,它们均使得物性进一步变差,而长石、岩屑颗粒及浊沸石胶结物的溶蚀作用改善了碎屑的孔喉结构,加大了次生孔隙空间,是物性得以改善的根本原因。     

永安镇油田沙四段自生粘土矿物及其对储层特性的影响

通过对永安镇油田沙四段砂岩储层中6口井的薄片、电镜及X衍射分析,研究了该储层中自生粘土矿物的分布产状、构成因素和成岩特征。根据自生粘土矿物在孔隙壁和孔隙喉道中的位置及分布状态,可将其分为孔隙分散粘土、孔隙衬边粘土和孔隙桥接粘土3种。研究区内自生粘土矿物的成岩相可划分为早成岩A期、B期及晚成岩A期和B+C期。在4个不同的成岩时期,自生粘土矿物的组合形式也不同。其垂向演化可以划分为3个带,即浆脱石带、I/S混层带和伊利石带。不同的转化带,自生粘土矿物的分布产状也不同,其中孔隙桥接粘土对孔隙度和渗透率影响最大。自生粘土矿物的存在,既可导致微粒的迁移,吸收或释放某些阳离子形成不溶沉淀物,堵塞孔隙喉道,改变储层孔隙结构,又可影响测井结果。为了减少自生粘土矿物对储层特性和测井结果的影响,文中提出了一些保护油层的措施。     

东营凹陷古近系红层储层成岩作用特征及形成机制

东营凹陷古近系孔店组一段（简称孔一段）-沙河街组四段下亚段（简称沙四下亚段）沉积时期发育了规模巨大的干旱气候条件下形成的红层沉积。综合利用钻井岩心、铸体薄片、物性及黏土矿物资料,并结合盆地埋藏演化史,对储层成岩作用特征及成因机制进行了系统研究。储层具有多重碱性成岩环境和酸性成岩环境作用特征。压实作用中等偏强,热压实效应明显。胶结物类型主要包括碳酸盐、铁碳酸盐、石膏、硬石膏和自生石英等,胶结作用在砂体边缘强,砂体内部较弱,砂体中部胶结物含量由断块下部向断块上部逐渐增加。溶解作用主要为碱性环境下形成的石英溶解和酸性环境下形成的长石、碳酸盐胶结物溶解,溶蚀孔隙含量由砂体边缘向砂体内部逐渐增加,由断块下部向断块上部逐渐降低。交代作用主要为碳酸盐、硫酸盐胶结物交代石英、长石颗粒及石英加大、铁碳酸盐交代碳酸盐。红层储层经历了早期碳酸盐及石膏胶结、早期石英溶解→长石及碳酸盐胶结物溶解、自生石英胶结→晚期碳酸盐及硬石膏胶结、晚期石英溶解→晚期少量碳酸盐胶结物、长石溶解的成岩演化序列。多重碱性及酸性成岩环境交替演化和上升流作用机制控制了储层的发育。     

沾化凹陷下第三系砂岩次生孔隙纵向分布规律

根据铸体薄片、扫描电镜、碳酸盐含量、镜质体反射率、粘土矿物以及储层物性等数据,研究了沾化凹陷下第三系砂岩次生孔隙的纵向分布规律。在小于1900m的深度,砂岩的孔隙主要为压实和胶结之后的原生粒间孔隙;在埋深达1900m以后开始出现少量次生孔隙,在1900～2200m深度范围形成原生孔隙与次生孔隙并存的混合孔隙带;大量的次生孔隙出现在2200～3500m的深度段。200多口井15000余个砂岩的孔隙度和渗透率在纵向上的变化关系也间接证实了这一点。次生孔隙主要为长石溶蚀成因,碳酸盐胶结物溶蚀是次要的,这是由有机酸对长石和碳酸盐胶结物的化学反应自由能所决定的。有机酸溶蚀长石的化学反应自由能(-154.49～-17.92kJ/mol)低于溶蚀碳酸盐(46.89kJ/mol)。在2200～3500m深度,沾化凹陷烃源岩成熟产生大量有机酸和泥岩中的粘土矿物迅速脱水是产生溶蚀作用形成次生孔隙的直接原因。     

PORE‐LINING CHLORITE CEMENTS IN LACUSTRINE‐DELTAIC SANDSTONES FROM THE UPPER TRIASSIC YANCHANG FORMATION,ORDOS BASIN,CHINA

Non‐marine sandstones in the upper Triassic Yanchang Formation constitute an important reservoir rock in the Zhenjing area of SW Ordos Basin, Central China. A study of the diagenetic history of these sandstones, including the formation of pore‐lining chlorite cements, was undertaken to investigate controls on reservoir quality. Data came from the petrographic analysis of cores from five wells. The sandstones were deposited in a lacustrine‐deltaic setting and consist of fine‐to medium‐grained feldspathic litharenites and lithic arkoses, and in general have low porosity and permeability. The principal diagenetic processes observed were compaction, cementation, dissolution and replacement. Mechanical compaction and calcite cementation caused a reduction in reservoir quality. The precipitation of pore‐lining chlorite inhibited quartz cementation and preserved porosities of up to 16%. The chlorite occurs in a double layer which lines pore spaces, particularly in distributary channel sandstones. Both chlorite layers grew by precipitation from pore waters containing the products of dissolution of volcanic rock fragments, biotites and feldspars. An increase of temperature during diagenesis was probably the cause of the two generations of chlorite cement, and also of the observed variations in elemental concentrations between the earlier‐ and later‐formed chlorite. The chlorite was precipitated after early compaction but before other diagenetic phases.