The influence of transgression and regression on the spatial and temporal distribution of diagenetic kaolin in the Upper Ordovician glaciogenic sandstones within a sequence stratigraphic framework, Murzuq Basin, SW Libya     

Mohamed A.K. El-ghali  Karima G. Tajori  Howri Mansurbeg 《Journal of Geochemical Exploration》2006,89(1-3):87

Linking diagenesis to depositional facies and sequence stratigraphy can provide a better understanding of some of the parameters that control the spatial and temporal distribution of diagenetic alterations and of their impact on reservoir quality. A study of the paralic, glaciogenic sandstones of the Melaz Shuqran and Mamunyiat formations (Late Ordovician) of the Murzuq Basin, SW Libya, reveals that the distribution of diagenetic kaolin can be constrained within depositional facies and sequence stratigraphy. Eogenetic kaolinite was formed by the dissolution of unstable detrital grains as a result of influx of meteoric waters into: (i) glacial, fluvial incised-valley lowstand systems tract (LST), glacial, tide-dominated estuarine transgressive systems tract (TST) during formation of overlying sequence boundary, (ii) paraglacial, tide-dominated deltaìc highstand systems tract (HST), paraglacial, foreshore to shoreface HST during progradation and basinward shift of the shoreline and/or formation of overlying sequence boundary, (iii) postglacial, Gilbert-type deltaic LST sandstones during relative sea level fall. On the other hand, formation of kaolinite immediately below maximum flooding surfaces is attributed to dissolution of unstable detrital grains by organic acids that were presumably derived from thermal alterations of organic matter, possibly during mesodiagenesis. The transformation of eogenetic kaolinite into dickite during mesodiagenesis is probably a consequence of low α_K⁺ / α_H⁺ ratio in the pore waters due to the scarcity of detrital K-feldspars.  相似文献   

新疆伊犁盆地南缘水西沟群沉积体系演化与赋铀性研究   总被引：1，自引：0，他引：1  

刘陶勇  毛永明 《新疆地质》2006,24(1):64-66

在分析伊犁盆地南缘水西沟群各地层岩石物性特征的基础上,结合盆地地形、地貌、沉积环境,建立和厘定了盆地水西沟群沉积体系,进而分析沉积体系的演化规律,指出在这一系列演化过程中砂体发育最好的是河流相及扇三角洲平原相至前缘相.结合层间氧化带砂岩型铀矿床成矿地质规律,分析了盆地铀成矿前景.  相似文献   

成岩作用对河流-三角洲相砂岩储层物性演化的影响--以延长油区上三叠统延长组长2砂岩为例   总被引：52，自引：5，他引：52  

罗静兰  张晓莉  张云翔  李玉宏  武富礼 《沉积学报》2001,19(4):541-547

延长油区上三叠统长 2地层河流相-三角洲相砂岩储层的物性明显受埋藏-成岩作用事件的影响。埋藏压实作用是导致砂岩孔隙丧失的主要原因,造成的平均孔隙度丧失为 17.8%。其中黑云母的早期成岩蚀变是造成原生孔隙丧失的一个重要原因。胶结作用造成的平均孔隙度丧失为 7.1%。其中碳酸盐胶结物和次生石英加大是造成砂岩物性降低的主要胶结物。碎屑颗粒周围绿泥石薄膜的存在阻止了一部分石英次生加大及碳酸盐胶结物的沉淀,使一部分原生粒间孔隙得以保存。晚期成岩阶段有机质分解形成的酸性流体及表生成岩作用阶段的大气降水是形成次生孔隙的主要原因,从而使长 2砂岩的物性得到改善  相似文献   

山东东营凹陷东部深层浊积扇储层的微观特征及影响因素   总被引：2，自引：1，他引：1  

夏景生王成明  王志坤陈 刚 朱 鑫 冀晓静 《中国地质》2008,35(5):975-983

东营凹陷东部深层浊积砂体以三角洲前缘的滑塌浊积砂体为主,储层岩性以长石细砂岩、岩屑细砂岩及粉砂岩为主,结构成熟度及成分成熟度均较低。储层微观特征研究表明,浊积砂体中主要发育剩余原生粒间孔、粘土矿物杂基内的微孔隙、粒间溶孔、粒内溶孔及微裂缝等储集空间类型;孔隙结构以低渗细喉型为主,为物性较差的中低孔、低渗型储层。通过对储层物性影响因素的研究得出,岩石组构、沉积微相、成岩作用和异常超压的形成与分布是影响本区浊积砂体储层物性的主要因素。其中成岩作用对浊积砂体物性的改造明显,压实和胶结作用是导致储层物性变差的主要原因;而溶蚀作用和成岩收缩作用则有利于储层孔渗性的改善。异常超压系统的存在、高的地温场及烃类的早期注入对该区浊积砂体储层物性起到了良好的保存和改善作用。  相似文献   

Reservoir prediction of deep-water turbidite sandstones with seismic lithofacies control —A case study in the C block of lower Congo basin     

《Marine and Petroleum Geology》2016

Currently, conventional forecasting methods of well-to-seismic integration are unable to identify turbidite channel sandstones due to scarcity of well data in deepwater areas, small geophysical differences between sandstones and mudstones of turbidite channels and strong sandstones heterogeneity. The reservoir prediction of deep-water turbidite channels is still a difficult issue in deep-water research. On the basis of previous studies, we propose a new technology named “reservoir prediction of deep-water turbidite sandstones with seismic lithofacies control” in view of the characteristics of deep-water turbidite sandstones. This new technology improves the reservoir prediction of complex sedimentary systems after classifying seismic lithofacies and connecting lithofacies with rock-physics. Furthermore, it can accomplish the genetic classification statistics of rock-physics, improve conversion accuracy of seismic elastic parameters/reservoir parameters and achieve the quantitative reservoir prediction under the double control of seismic geomorphology and seismic lithofacies. The C block of Lower Congo Basin is characterized by few well data, complex lithology but high resolution-seismic. We use the technology to predict the reservoirs of this area and have achieved excellent results. This has great significance for the later exploration.  相似文献   

Controls on reservoir quality of Lower Cretaceous tight sandstones in the Laiyang Sag,Jiaolai Basin,Eastern China: Integrated sedimentologic,diagenetic and microfracturing data     

《Marine and Petroleum Geology》2016

The Jiaolai Basin (Fig. 1) is an under-explored rift basin that has produced minor oil from Lower Cretaceous lacustrine deltaic sandstones. The reservoir quality is highly heterogeneous and is an important exploratory unknown in the basin. This study investigates how reservoir porosity and permeability vary with diagenetic minerals and burial history, particularly the effects of fracturing on the diagenesis and reservoir deliverability. The Laiyang sandstones are tight reservoirs with low porosity and permeability (Φ < 10% and K < 1 mD). Spatial variations in detrital supply and burial history significantly affected the diagenetic alterations during burial. In the western Laiyang Sag, the rocks are primarily feldspathic litharenites that underwent progressive burial, and thus, the primary porosity was partially to completely eliminated as a result of significant mechanical compaction of ductile grains. In contrast, in the eastern Laiyang Sag, the rocks are lithic arkoses that were uplifted to the surface and extensively eroded, which resulted in less porosity reduction by compaction. The tectonic uplift could promote leaching by meteoric water and the dissolution of remaining feldspars and calcite cement. Relatively high-quality reservoirs are preferentially developed in distributary channel and mouth-bar sandstones with chlorite rims on detrital quartz grains, which are also the locations of aqueous fluid flow that produced secondary porosity. The fold-related fractures are primarily developed in the silt–sandstones of Longwangzhuang and Shuinan members in the eastern Laiyang Sag. Quartz is the most prevalent fracture filling mineral in the Laiyang sandstones, and most of the small-aperture fractures are completely sealed, whereas the large-aperture fractures in a given set may be only partially sealed. The greatest fracture density is in the silt–sandstones containing more brittle minerals such as calcite and quartz cement. The wide apertures are crucial to preservation of the fracture porosity, and the great variation in the distribution of fracture-filling cements presents an opportunity for targeting fractures that contribute to fluid flow.  相似文献   

致密砂岩天然气藏地质特征——川西深井钻探的启示   总被引：1，自引：0，他引：1  

曹伟  王允诚 《矿物岩石》1998,18(3):39-44

四川盆地西部是我国重要的天然气基地,属致密砂岩非常规天然气藏,具有独特的天然气地质学特征。依据钻达上三叠统的４０余口钻井资料,通过对油气显示、产层特征及测试等综合分析,总结和揭示了川西上三叠统的储、产层特征及其与天然气产出的关系,为老井挖潜和进一步勘探部署提供了参考意见。  相似文献   

早期碳酸盐胶结作用对砂岩孔隙演化的影响——以塔里木盆地满加尔凹陷志留系砂岩为例   总被引：11，自引：4，他引：7  

钟大康  朱筱敏  李树静  谢楠 《沉积学报》2007,25(6):885-890

塔里木盆地满加尔凹陷志留系砂岩为无障壁的潮坪、滨岸及辫状河三角洲沉积的岩屑砂岩和岩屑质石英砂岩,对满北和满东、满南地区志留系砂岩成岩作用序次尤其是碳酸盐胶结的时间、方式和特征、物性的对比研究认为:砂岩中碳酸盐胶结的时间早晚对砂岩孔隙演化具有重要影响,满北地区志留系砂岩发育有大量早期泥晶碳酸盐胶结,显微镜下研究表明这种胶结作用发生在岩石受到充分压实之前,呈基底式胶结,岩石颗粒呈点接触或漂浮状分布于早期碳酸盐胶结物之中,这种胶结作用抑制了岩石后期的压实作用。尽管目前其埋藏达5 000～6 500 m,但其经历的压实作用并不强烈,粒间发育大量早期的碳酸盐胶结物,后来这些胶结物被溶蚀,形成了大量次生孔隙。而在满东和满南地区的志留系砂岩,碳酸盐胶结发生在岩石经过充分压实之后,晚期的碳酸盐胶结物仅分布于岩石经充分压实后的粒间孔隙中,含量较前者低,后期可供溶蚀的碳酸盐比前者少,因而溶蚀形成的次生孔隙有限。因此,尽管满东满南地区志留系埋藏比满北浅（3 700～5 000 m）,碳酸盐胶结物含量也低,也发育晚期碳酸盐胶结物的溶蚀,但岩石的压实作用比满北强,物性比满北低差。这主要与碳酸盐胶结的早晚有关,早期碳酸盐胶结对孔隙演化具有明显控制作用,有利于岩石孔隙的保存,为后来的溶蚀形成次生孔隙提供了条件。  相似文献   

Diagenesis and reservoir quality analysis in the Lower Cretaceous Qishn sandstones from Masila oilfields in the Sayun–Masila Basin,eastern Yemen     

Nabil M. Al Areeq  Mohamed A. Soliman  Mahmoud A. Essa  Nabeel A. Al‐Azazi 《Geological Journal》2016,51(3):405-420

Lower Cretaceous sandstones of the Qishn Formation have been studied by integrating sedimentological, petrological and petrophysical analyses from wells in the Masila oilfields of eastern Yemen. These analyses were used to define the origin, type of diagenesis and its relation to reservoir quality. The sandstones of the Qishn Formation are predominately quartz arenite to subarkose arenite with sublitharenite and quartz wackes displaying a range of porosities, averaging 22.33%. Permeability is likewise variable with an average of 2844.2 mD. Cementation coupled with compaction had an important effect on porosity destruction after sedimentation and burial. The widespread occurrence of early calcite cement suggests that the sandstones of the Qishn Formation lost significant primary porosity at an early stage of its diagenetic history. In addition to poikilotopic calcite, several different cements including kaolinite, illite, chlorite and minor illite–smectite occur as pore‐filling and pore‐lining cements, which were either accompanied by or followed the development of the early calcite cement. Secondary porosity development occurred due to partial to complete dissolution of early calcite cements and feldspar grains. The new data presented in this paper suggest the reservoir quality of Qishn sandstones is strongly linked to their diagenetic history; hence, the reservoir quality is reduced by clay minerals, calcite and silica cements but is enhanced by the dissolution of the unstable grains, in addition to partial or complete dissolution of calcite cements and unstable grains. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Formation of Hengchun Accretionary Prism Turbidites and Implications for Deep‐water Transport Processes in the Northern South China Sea     

CUI Yuchi  SHAO Lei  YU Mengming  HUANG Chiyue 《《地质学报》英文版》2021,95(1):55-65

Located at the end of the northern Manila Trench,the Hengchun Peninsula is the latest exposed part of Taiwan Island,and preserves a complete sequence of accretionary deep-sea turbidite sandstones.Combined with extensive field observations,a’source-to-sink’approach was employed to systematically analyze the formation and evolutionary process of the accretionary prism turbidites on the Hengchun Peninsula.Lying at the base of the Hengchun turbidites are abundant mafic normal oceanic crust gravels with a certain degree of roundness.The gravels with U-Pb ages ranging from 25.4 to23.6 Ma are underlain by hundreds-of-meters thickness of younger deep-sea sandstone turbidites with interbedded gravels.This indicates that large amounts of terrigenous materials from both the’Kontum-Ying-Qiong’River of Indochina and the Pearl River of South China were transported into the deep-water areas of the northern South China Sea during the late Miocene and further eastward in the form of turbidity currents.The turbidity flow drastically eroded and snatched mafic materials from the normal South China Sea oceanic crust along the way,and subsequently unloaded large bodies of basic gravel-bearing sandstones to form turbidites near the northern Manila Trench.With the Philippine Sea Plate drifting clockwise to the northwest,these turbidite successions eventually migrated and,since the Middle Pleistocene,were exposed as an accretionary prism on the Hengchun Peninsula.  相似文献