鄂尔多斯盆地姬塬地区延长组长4+5低渗透储层成因

碎屑岩储层成岩作用复杂而强烈,对储层物性有着重要影响。应用岩相学研究方法,在对鄂尔多斯盆地姬塬地区延长组长4+5低渗砂岩储层成岩作用及其对物性影响定量研究基础上,探讨了低渗储层成因机理。成岩作用和孔隙演化研究表明,压实作用虽然造成12%～20%的孔隙度损失,但是压实后剩余孔隙度仍高达15%～23%,早期胶结作用使孔隙度损失很小,压实作用和早期胶结作用并没有使储层致密,不影响油气渗流。溶蚀作用进一步改善了储层,晚成岩阶段A期-B期形成的钠长石、亮晶方解石、白云石、自生高龄石和铁绿泥石等大量胶结物的晚期胶结作用使储层孔隙度仅有4%～6%,储层因此而致密,由此影响油气渗流。晚期裂隙作用对储层孔隙度贡献为6%～8%,改善了储层物性而使其成为有效储层。盆地演化及与之对应的成岩事件研究认为,印支运动前,姬塬地区长4+5储层处于浅埋藏阶段,经历压实作用和早期胶结作用,早-中侏罗世长 7烃源岩进入未成熟-低熟阶段,形成富含有机酸流体进入储层而发生溶蚀作用,早白垩世中-晚期进入深埋藏成岩阶段,晚期胶结物大量形成而使储层致密。生烃增压作用导致的裂隙以及晚白垩世以来的构造运动形成的裂缝对研究区长4+5有效储层形成具有非常重要意义,同时对低渗油气藏勘探也具有指导意义。     

Diagenesis of early Permian high‐latitude limestones,Lower Parmeener Supergroup,Tasmania

The Darlington (Sakmarian) and Berriedale (Artinskian) Limestones are neritic deposits that accumulated in high‐latitude environments along the south‐eastern margin of Pangea in what is now Tasmania. These rocks underwent a series of diagenetic processes that began in the marine palaeoenvironment, continued during rapid burial and were profoundly modified by alteration associated with the intrusion of Mesozoic igneous rocks. Marine diagenesis was important but contradictory; although dissolution took place, there was also coeval precipitation of fibrous calcite cement, phosphate and glauconite, as well as calcitization of aragonite shells. These processes are interpreted as having been promoted by mixing of shelf and upwelling deep ocean waters and enabled by microbial degradation of organic matter. In contrast to warm‐water carbonates where meteoric diagenesis is important, the Darlington and Berriedale Limestones were largely unaffected by meteoric diagenesis. Only minor dissolution and local cementation took place in this diagenetic environment, although mechanical compaction was ubiquitous. Correlation with burial history curves indicates that chemical compaction became important as burial depths exceeded 150 m, promoting precipitation of extensive ferroan calcite. This effect resulted from burial by rapidly deposited, overlying, thick, late Permian and Triassic terrestrial sediments. This diagenetic pathway was, however, complicated by the subsequent intrusion of massive Mesozoic diabases and associated silicifying diagenetic fluids. Finally, fractures most probably connected with Cretaceous uplift were filled with late‐stage non‐ferroan calcite cement. This study suggests that both carbonate dissolution and precipitation occur in high‐latitude marine palaeoenvironments and, therefore, the cold‐water diagenetic realm is not always destructive in terms of diagenesis. Furthermore, it appears that for the early Permian of southern Pangea at least, there was no real difference in the diagenetic pathways taken by cool‐water and cold‐water carbonates.     

Diagenesis of the black river (middle ordovician) limestones in Southern Ontario,Canada

The diagenetic history of the Black River Limestone Group is discussed with special reference to solution (leaching), cementation, neomorphism, authigenesis, pressure solution, compaction and dedolomitization.Formation of recrystallization textures (microspar and pseudospar) was controlled by original sediment grain size and occurred during both early and late stages of diagenesis.Dolomite, celestite and pyrite were the chief developments of late diagenetic minerals in the Black River carbonates. Pressure-solution (stylolitization) phenomena occurred at a very late diagenetic stage. Compaction played a minor role in the diagenesis of the rocks.Dedolomitization is a surface phenomenon related to weathering.     

Depositional Environments and Diagenesis of the Kuldhar and Keera Dome Carbonates (Late Bathonian–Early Callovian) of Western India

This paper describes 11 microfacies types in late Bathonian–Early Callovian carbonates of the Kuldhar Member of the Jaisalmer Formation (Rajasthan) and the Keera Golden Oolite Member of the Chari Formation (Kachchh Mainland) western India. The different microfacies associations reported in this study reflect an ideal shallowing upward sequence, representing a system of bioclastic bars developed on the lower ramp, evolving into an oolitic bar-to-bank system separating restricted lagoonal—from lower ramp environment. Four main types of cements, i.e. bladed, fibrous, syntaxial overgrowth and blocky cement (characterized in a few cases by ferroan calcite and anhydrite II) occur in these carbonates. The study also reveals that chemical compaction followed the two phases of early mechanical compaction that largely governed porosity of these limestones. However, micritization and neomorphism also contributed significantly in this respect. Diagenetic signatures in these carbonates suggest that marine phreatic and fresh water phreatic environments dominated, but deep burial diagenesis also played its role in shaping these rocks. The early and late diagenetic changes have been controlled by the depositional facies evolving in a basin riddled with rifting in an extensional tectonic regime forcing regional-scale sea level fluctuations.     

Halite cementation and carbonate diagenesis of intra-salt reservoirs from the Late Neoproterozoic to Early Cambrian Ara Group (South Oman Salt Basin)

Late Neoproterozoic to Early Cambrian carbonates of the Ara Group form important intra‐salt ‘stringer’ reservoirs in the South Oman Salt Basin. Differential loading of thick continental clastics above the six carbonate to evaporite cycles of the Ara Group led to the formation of salt diapirs, encasing a predominantly self‐charging hydrocarbon system within partly highly overpressured carbonate bodies (‘stringers’). These carbonates underwent a complex diagenetic evolution, with one stage of halite cementation in a shallow (early) and another in a deep (late) burial environment. Early and late halite cements are defined by their microstructural relationship with solid bitumen. The early phase of halite cementation is post‐dated by solid reservoir bitumen. This phase is most pervasive towards the top of carbonate stringers, where it plugs nearly all available porosity in facies with initially favourable poroperm characteristics. Bromine geochemistry revealed significantly higher bromine contents (up to 280 p.p.m.) in the early halite compared with the late halite (173 p.p.m.). The distribution patterns and the (high) bromine contents of early halite are consistent with precipitation caused by seepage reflux of highly saturated brines during deposition of the overlying rock salt interval. Later in burial history, relatively small quantities of early halite were dissolved locally and re‐precipitated as indicated by inclusions of streaky solid bitumen within the late halite cements. Late halite cement also seals fractures which show evidence for repeated reopening. Initially, these fractures formed during a period of hydrothermal activity and were later reopened by a crack‐seal mechanism caused by high fluid overpressures. Porosity plugging by early halite cements affects the poroperm characteristics of the Ara carbonates much more than the volumetrically less important late halite cement. The formation mechanisms and distribution patterns of halite cementation processes in the South Oman Salt Basin can be generalized to other petroliferous evaporite basins.     

Petrofacies, provenance and diagenesis of the dhosa sandstone member (Chari Formation) at Ler, Kachchh sub-basin, Western India

The sandstones of the Dhosa Sandstone Member of Late Callovian and Early Oxfordian age exposed at Ler have been analyzed for their petrofacies, provenance, tectonic setting and diagenetic history. These sandstones are fine to medium grained and poorly- to well sorted. The constituent mineral grains are subangular to subrounded. These sandstones were derived from a mixed provenance including granites, granite–gneisses, low- and high-grade metamorphic and some basic rocks of the Aravalli Range and Nagarparkar Massif. The petrofacies analysis reveals that these sandstones belong to the continental block-, recycled orogen- and rifted continental margin tectonic regime.The imprints of early and deep burial diagenesis of these sandstones include different stages of compaction, cementation, change in crystal boundaries, cement–cement boundaries, chertification and neomorphism. The sequence of cementation includes precipitation of calcite and its subsequent replacement by Fe calcite and silica cements. The typical intermediate burial (2–3 km depth) diagenetic signatures of these sandstones are reflected in the formation of suture and straight-line boundaries, and triple junctions with straight-line boundaries. The depositional environment, relatively low-energy environment that was below storm wave base but subjected to gentle currents, of the Dhosa Sandstone Member controlled the early diagenesis, which in turn influenced the burial diagenesis of these sandstones.     

塔北隆起哈拉哈塘凹陷东河砂岩成岩作用及其控制因素

通过岩心及薄片的观察,结合扫描电镜阴极发光等资料分析,对哈拉哈塘地区东河砂岩成岩作用进行了研究。结果表明：东河砂岩以岩屑石英砂岩为主,成岩作用类型有压实作用、胶结作用、溶解作用及交代作用。综合成岩作用的组合类型及其演化序列,认为本区东河砂岩主体处于中成岩阶段A期。分别讨论了沉积相、埋藏作用和层序地层等对成岩作用的控制,研究区东河砂岩在低温背景下,长期浅埋且晚期短暂快速深埋,总体上压实程度中等;主要发育滨岸和浪控三角洲沉积体系,在高精度层序界面附近,相对海平面上升,可容纳空间增大,沉积物沉积速率相对较低,且停留时间长,在同生成岩和早成岩阶段容易形成广泛分布的碳酸盐胶结。     

Diagenetic alterations of the upper Jurassic scleractinian corals,Hanifa Formation,Jabal Al-Abakkayn,central Saudi Arabia

During diagenetic stages, the aragonitic skeletons and the inter/intra-corallite cement of the upper Jurassic corals of Hanifa Formation either dissolved or subjected to diagenetic alterations including cementation, micritization, recrystallization, silicification, dolomitization and dedolomitization. The proposed sequence of diagenetic stages is as follows: early marine diagenesis, early meteoric and mixing zone diagenesis, late meteoric diagenesis, and shallow burial diagenesis. Each stage is characterized by certain diagenetic processes. The source of sulfate solutions for dedolomitization in the studied corals is the dissolved anhydrite deposits of the Arab–Hith Formations, sometime before their erosion. A possible source of silica, needed for the formation of chert and chalcedony, is the sponge spicules dispersed in many carbonates of the Hanifa Formation.     

歧口凹陷沙河街组火山岩成岩作用及对储集性能的控制

根据岩心观察资料,利用偏光显微镜、扫描电镜等对歧口凹陷沙河街组火山岩的成岩作用进行了详细地研究,把成岩作用类型分为早期和晚期两个阶段、13种成岩作用类型。根据成岩作用阶段划分依据,结合盆地埋藏-热演化史和烃类充注史等资料,将歧口凹陷沙河街组火成岩成岩作用阶段划分为早期和晚期两个阶段。火成岩共发生了3期溶蚀作用、2期构造作用、2期油气充注作用,以及绿泥石、硅质、碳酸盐等胶结作用。主要成岩序列为溶蚀作用Ⅰ→构造作用Ⅰ→栉壳状绿泥石→细纤维状绿泥石→硅质Ⅰ→较粗纤维状绿泥石→烃类充注Ⅰ→硅质充填Ⅱ→亮晶方解石Ⅰ→构造作用Ⅱ→溶蚀作用Ⅱ→烃类充注Ⅱ→亮晶方解石Ⅱ→铁方解石→硅质充填Ⅲ→溶蚀作用Ⅲ。成岩作用对储集性能的控制具有改善和破坏的双重作用,对储集性能具有改善作用的成岩作用类型有挥发分逸出作用、熔蚀作用、冷凝收缩作用、脱玻化作用、机械压实破裂作用、风化淋滤溶蚀作用、次生溶蚀作用。对储集性能具有破坏作用的成岩作用类型有熔结作用、充填作用、机械压实压溶作用、胶结作用。     

Diagenesis of Barremian-Aptian platform carbonates (the Urgonian Limestone Formation of SE France): near-surface and shallow-burial diagenesis

The diagenesis of carbonate platform sediments is controlled by the original facies and mineralogy, climate, sea-level changes and burial history; these controls are clearly seen in the diagenesis of the Urgonian platform carbonates of SE France. Early diagenesis in the Urgonian platform included the precipitation of marine cements, dissolution of rudist shells and minor karstification. Diagenetic features produced during this phase were controlled by several falls in relative sea-level during the Barremian to mid-Aptian punctuating platform sedimentation, the original mineralogy of the sediment and the prevailing semi-arid/arid climate in the region at this time. Following a relative sea-level rise and further sedimentation, progressive burial of the platform led to minor compaction, followed by precipitation of coarse, equant, zoned to non-luminescent, calcite cement. This cement was cut by later stylolites, suggesting a relatively shallow-burial origin. Stable isotope (mean values - 7.94%δ¹⁸O and 0.36%δ¹³C) and trace element (mean values of Fe 334 ppm, Mn 92 ppm and Sr 213 ppm) data suggest that these cements precipitated from meteoric fluids at temperatures slightly elevated relative to depositional temperatures. A variable thickness of replacive dolomite which occurs preferentially within the shelf-margin facies of the lower part of the Urgonian post-dates mechanical fracturing and chemical compaction, but pre-dates the main phase of stylolitization. It is probable that the dolomitizing fluid was sourced by the early compaction-driven release of connate fluids held within the underlying muddy units. The burial history of these rocks suggests that calcite cementation and dolomitization took place at relatively shallow burial depths (1–1.5 km). The overall diagenetic history of the Urgonian Limestone Formation is a reflection of the pre-conditioning of the platform limestones by climate, sea level, tectonics and the shallow burial depths experienced by the platform during the later Mesozoic.     

鲁西隆起区奥陶系碳酸盐岩成岩作用及其对储集性的控制作用

以鲁西隆起区奥陶系碳酸盐岩沉积旋回与不整合面分析为基础, 应用薄片、铸体和阴极发光等室内分析技术, 对其成岩作用、成岩序列、孔隙演化及其特征进行了详细研究。研究区的成岩作用分为两类: 建设性成岩作用和破坏性成岩作用, 前者包括白云石化、压溶、去石膏化、溶蚀和破裂等作用; 后者以重结晶、胶结、压实、硅化和充填作用为主。奥陶系碳酸盐岩经历了多期次和多种类型的成岩作用演化, 与马家沟组相比, 三山子组多经历了一次其沉积后的短期表生和随后的埋藏作用。三山子组白云岩、马家沟组东黄山段、土峪段和阁庄段粉细晶白云岩以及八陡段不整合面以下的溶蚀角砾岩段发育次生孔洞缝系统, 是较为有利的储集层段。     

塔中地区良里塔格组碳酸盐岩储层特征及成岩作用

塔中地区良里塔格组发育巨厚的礁滩相碳酸盐岩,为碳酸盐岩储层的形成提供了有利条件。通过对钻井岩心和薄片分析,系统研究了研究区良里塔格组碳酸盐岩的储层岩石学、成岩作用类型和特征,总结了各类成岩作用的识别标志、发育规律及对储集体形成的影响。研究区碳酸盐岩储层的成岩作用包括泥晶化作用、白云石化作用、方解石胶结作用、溶蚀作用、硅化和硅质充填作用,以及压实、压溶作用、破裂作用和自生黄铁矿作用。在此基础上,总结了良里塔格组碳酸盐岩成岩序列及储层孔隙演化规律,认为早期强烈的方解石胶结作用和压实压溶作用降低了储层的孔隙度和渗透率,而溶蚀作用和构造破裂作用对良里塔格组礁滩相碳酸盐岩优质储层的形成具有明显控制作用。     

准噶尔盆地莫索湾地区清水河组深层优质储层特征及其物性控制因素

为了明确准噶尔盆地腹部莫索湾地区清水河组储层特征及其成因,综合利用铸体薄片、扫描电镜、物性、X衍射等多种分析测试手段,并结合钻测井、地层测试资料及区域埋藏史、古地温、沉积体系等相关研究成果,详细分析了清水河组储层成岩作用特征及其物性控制因素,并在此基础上总结成岩模式。研究结果表明:清水河组储层具有低成分成熟度、高塑性岩屑含量及高结构成熟度的"一低两高"特征;尽管储层主体埋深在3 500m以下,但储集空间仍以原生粒间孔为主,平均孔隙度为15.47%,平均渗透率可达226.6mD,为典型的深层优质储层;储层成岩作用总体表现为"中压实中强压实、强溶蚀、弱胶结"的特征,尽管储层埋深较大,但成岩阶段整体仍处于中成岩A1亚期;区域连片的厚层辫状河三角洲前缘水下分流河道及河口坝中细砂岩及中粗砂岩是形成深层优质储层的基础,而成岩过程中储层物性保存主要受控于早期碳酸盐胶结抗压实、绿泥石包壳及后期酸性成岩流体条件下的溶蚀增孔作用;除上述沉积、成岩控制因素外,地层超压的存在使得储层在深埋条件下压实强度显著降低,是储层物性保存的关键,同时在储层成岩演化过程中及现今盆地不断降低的地温梯度也有效延缓了储层的成岩进程。     

鄂尔多斯盆地LX地区山西组储层成岩演化及成岩相研究

利用鄂尔多斯盆地LX地区山西组铸体薄片、扫描电镜、阴极发光、地球化学资料等,通过统计、计算等方法,对该区山西组储层岩石学特征、成岩作用类型、成岩演化阶段及成岩演化过程进行研究,在此基础上建立研究区山西组成岩相类型及划分标准,并最终确定了该区山西组成岩相平面展布特征。研究表明:压实和胶结作用是研究区山西组储层砂岩致密化的主要原因;成岩阶段主体已经进入中成岩B期;其成岩演化过程为早成岩A期的压实及少量胶结阶段,早成岩B期的压实及少量溶蚀及胶结阶段,中成岩A期的大量溶蚀和胶结阶段以及中成岩B期的碳酸盐胶结阶段;成岩相类型分为4类:中等压实-弱胶结-溶蚀相,中等压实-中等胶结-溶蚀相,中等压实-强胶结相,强压实-杂基强充填相;有利成岩相在研究区分布面积较广,说明研究区具备了良好的勘探潜力,尤其是发育在研究区的中等压实-弱胶结-溶蚀相区域,可作为该区山西组下一步勘探开发的重点。     

鄂尔多斯盆地姬塬西部三叠系延长组长8油层组成岩作用与致密化过程*

利用岩心、铸体薄片、扫描电镜、碳氧同位素及流体包裹体等资料,对鄂尔多斯盆地姬塬西部三叠系延长组长8油层组致密储集层特征进行了研究,重点分析了储集层成岩作用特征和储集层致密化成因机制及过程。研究区长8油层组砂岩主要为岩屑长石砂岩和长石岩屑砂岩,经历了压实—压溶、胶结、交代、溶蚀及构造破裂等成岩作用,整体处于中成岩A期晚期。典型成岩序列依次为机械压实、绿泥石黏土膜、早期(泥晶)方解石胶结、石英次生加大、长石、岩屑溶蚀、自生高岭石胶结、自生石英胶结、中期(含)铁方解石胶结。综合研究认为:(1)近物源伴随湖平面快速上升的沉积环境提供了储集层致密化的物质基础,不同沉积微相储集层物性差别较大,分流河道最好,分流间湾最差;(2)长8油层组原始孔隙度为41.35%,压实作用损孔率为50.67%,造成储集层孔隙度急剧降低,胶结作用损孔率为37.48%,导致孔隙度进一步减小,溶蚀作用仅增加了3.26%的孔隙度,难以有效改善储集层质量;(3)上述沉积与成岩因素共同导致储集层致密,致密化过程可分为压实孔隙骤减阶段、早期胶结减孔阶段、溶蚀作用增孔阶段和晚期胶结致密阶段共4个阶段;(4)油气大量充注期储集层孔隙度远低于10%,长8油层组先致密后成藏。     

伦坡拉盆地下第三系储层的成岩作用和储集性能的成岩控因

区内下第三系储层经历了压实、胶结、溶蚀、破裂等一系列成岩作用,成岩作用十分复杂,成岩现象也十分丰富,特征十分明显。储层储集性能的成岩控因研究表明,压实作用、胶结作用是使储层物性变差、孔隙度降低的两个重要成岩控因;而溶蚀作用,特别是深埋溶蚀作用是改善储层储集性能、使储层物性变好的成岩控因之一。     

碳酸盐岩成岩作用与孔隙演化

在总结我国碳酸盐岩沉积和成岩基本特征的基础上,阐明有利于孔隙形成的白云石化、去膏、去云化、淡水和埋藏溶解等作用,以及破坏性成岩作用的特征和识别标志。成岩地质体是成岩环境的产物,可根据成岩组构、地球化学和发光特征等加以鉴别。成岩模式是成岩组合、成岩特征和孔隙演化的总概括,以滩相成岩模式展示了成岩相与孔隙的关系。     

东营凹陷古近系孔店组成岩特征及对储层的控制

通过岩石薄片、扫描电镜、镜质体反射率、X衍射、物性分析等资料,对东营断陷盆地古近系孔店组成岩作用进行研究。结果表明:原始碎屑组分和化学沉积分异作用引起的早期胶结物性质决定了后期的成岩演化;典型成岩现象有强烈压实作用、硬石膏胶结、多期次碳酸盐胶结、多期次粘土矿物胶结、硅质强烈胶结、矿物强烈穿插交代、碎屑颗粒和胶结物的溶解作用,各种成岩现象对深部碎屑岩储层均产生重要影响。同时也证实:压实作用是引起深部碎屑岩强烈致密化的主要原因;硬石膏胶结、碳酸盐胶结和硅质胶结是引起致密化的又一重要原因;长石、碳酸盐胶结物的溶解作用是引起该地区储层改善的主要成岩因素。      

海拉尔盆地贝尔凹陷铜钵庙组成岩作用及其对孔隙演化的影响

海拉尔盆地贝尔凹陷铜钵庙组发育一套火山碎屑岩类、火山-沉积岩类和少量的陆源碎屑岩岩石组合。其中,火山碎屑岩类、火山-沉积岩类成岩作用受火山碎屑物质控制作用明显。典型的成岩作用类型包括压实作用,胶结作用和溶蚀、溶解作用等。成岩阶段属中成岩A期。通过孔隙演化研究发现,压实作用是该区原始孔隙损失的最主要因素;其次为胶结作用。早期压实作用和胶结作用共损失83%以上的原生孔隙,晚期岩屑溶蚀和长石溶蚀作用增加6.53%的孔隙度,有效地改善了储层的物性特征。此外,不同岩石类型成岩作用特征及其对孔隙的影响差异较大。     

Diagenetic evolution vis-a-vis reservoir characteristics of Dhosa sandstones,Ler dome,Kachchh, western India

The detrital mineralogy as well as diagenetic characters of the Dhosa Sandstone Member of Chari Formation exposed at the Lerdome, south of Bhuj was studied. In order to assess the potential of the Dhosa Sandstone as a reservoir, it is substantial to understand the diagenetic processes that are controlled largely by post-depositional cementation and compaction in addition to framework composition and original depositional textures. The petrologic analysis of 33 thin sections was carried out to discern primary composition and diagenetic features including primary and secondary porosity patterns. Monocrystalline quartz dominates the detrital mineralogy followed by polycrystalline quartz. Among the polycrystalline variety recrystallized metamorphic quartz surpasses stretched metamorphic quartz in terms of abundance. Feldspars comprise microcline and plagioclase where the former is dominant over the latter. Orthoclase too comprises a very small percentage. Mica, chert, rock fragments, and heavies form the remaining detrital constituent in descending order of their constituent percentage. The diagenetic precipitates are mainly carbonate (8.30%) and iron (7.80%) followed by clay (0.66%) and silica (0.88%) that are minor constituent of the total cementing material. The main paragenetic events identified are early cementation, mechanical compaction, late cementation, dissolution, and authigenesis of clays. The overall reservoir quality seems to be controlled by compaction and authigenic carbonate cementation. The minus cement porosity average 29.4%. The porosity loss due to compaction is 21.92% and by cementation is 29.71%. The loss of original porosity was due to early cementation followed by moderate mechanical compaction during shallow burial. Preservation of available miniscule primary porosity was ascribed to dissolution of carbonates and quartz overgrowth which resisted chemical compaction during deep burial. The studied sandstones may have low reservoir quality owing to existing porosity of less than 9%. More carbonate dissolution and its transformation in dolomite in sub-surface condition and macro-fracture porosity may result in enhanced secondary porosity and good diagenetic traps.