Oil-bearing inclusions in vein quartz and calcite and,bitumens in veins: Testament to multiple phases of hydrocarbon migration in the Barrandian basin (lower Palaeozoic), Czech Republic     

V. Suchý  P. Dobeš  I. Sýkorová  V. Machovič  M. Stejskal  J. Kroufek  J. Chudoba  L. Matějovský  M. Havelcová  P. Matysová 《Marine and Petroleum Geology》2010

The petroleum charge history of the Barrandian basin was investigated by analysing quartz and calcite and organic phases that occur in veins and fractures cutting dolerite sills within the Liteň Formation (Silurian). The geochemical characteristics of fluid inclusions trapped in vein quartz and calcite, vein bitumens and adjacent potential source rocks when combined with burial and thermal history data reflect the presence of at least three separate hydrocarbon charge episodes. Solid highly reflecting (R_max = 0.92–1.49%) bitumen provides information on the first and oldest episode of oil migration. The precursor oil was probably derived relatively early during diagenesis from nearby organic-rich sediments and was subsequently thermally altered to form the solid bitumen.  相似文献   

Predictive permeability variations in a Hermod sand reservoir,Stine Segments,Siri Field,Danish North Sea     

Jesper Stokkendal  Henrik Friis  Johan B. Svendsen  Mette Lise K. Poulsen  Lars Hamberg 《Marine and Petroleum Geology》2009

The Hermod sand of the Stine Segments, Siri Field, Danish North Sea, displays large permeability variations (1–600 mD). These permeability variations represent horizontal layering in the reservoir, largely formed by diagenetic processes. They have a significant impact on reservoir performance, because horizontal producers in fairly thin reservoirs (∼30 m) are protected against bottom-water influx and can produce water-free for long periods of time.  相似文献   

Nature of fluids and regional implications for Lesser Himalayan carbonates and associated mineralization     

Rajesh Sharma 《Journal of Geochemical Exploration》2006,89(1-3):363

Fluid inclusion data are presented for the successive stages of limestone, dolomite, magnesite and sulphide-bearing quartz veins in Proterozoic carbonate rocks of the Lesser Himalaya. Subsurface fluids were H₂O–NaCl–KCl ± MgCl₂ ± CaCl₂ and showed successive increase in salinity and temperature. The salinity of the pore fluid during limestone diagenesis was in the range of 7.5–15 eq wt.% NaCl and the magnesite-forming fluids had a salinity of about 9 to 19 eq wt.% NaCl. This progressive rise in salinity is attributed to a more saline fluid in the deeper zones. The inverse relation between homogenization temperatures and final melting temperatures suggests mixing of the fluids during diagenesis, and highly depleted δ¹⁸O values rule out participation of magmatic fluid in the mixing. A late stage carbonic fluid is linked with talc formation. The low temperature of sulphide-forming epigenetic solutions, as obtained from fluid inclusions, is also substantiated by the chemical data from these sulphides. δ³⁴S values in galena infer that magmatic sulphur was probably not involved, and the sulphur of the galena is derived from an isotopically heavy source.  相似文献   

塔东北库鲁克塔格中上寒武统白云岩岩石学、地球化学特征与成因探讨——与加拿大西部盆地惠而浦(Whirlpoolpoint)剖面对比   总被引：3，自引：0，他引：3  

钱一雄  尤东华  陈代钊  卿海若  何治亮  马玉春  田蜜  席斌斌 《岩石学报》2012,28(8):2525-2541

通过对比研究塔里木盆地东北缘库鲁克塔格隆起的乌里格孜塔格剖面与加拿大西部盆地寒武系白云岩的岩石学、地球化学及流体包裹体等特征,阐明了前者经历了三次主要白云岩(化)作用事件.①成岩早期-浅埋藏的粉细晶白云岩作用,Sr为42.75×10-6,Mn为315×10-6 ～506×10-6,Fe为0.2650％ ～0.403％;δ13 CpDB=一0.47‰ ～-0.28‰,δ18OPDB=-7.3‰ ～-7.43‰,87Sr/86Sr=0.71085;平均REE=18.84×10-6,δEu平均为0.66、δCe平均为0.81,估算的形成温度分别为47.6℃和55.12℃;②中(深)埋藏的细晶及中(粗)晶白云岩化作用;Sr为56.27×10-6,Mn为312×10-6,Fe为0.13％;δ13CPDB=-1.5‰,δ18OPDB=-8.5‰,87Sr/86Sr=0.7100; REE=18.08×10-6,δEu平均为0.72、δCe平均为0.77,盐水包裹体中的均一温度平均为108.34℃,盐度变化为4％～13.7％ NaCleqv;③沿裂隙或溶洞形成的粗-巨晶或鞍形的热液白云岩(石)交代充填:Sr为29.1×10-6 ～49.9×10-6,Mn为498×10-6～754×10-6,Fe为0.15％ ～ 1.14％;平均δ13 CPDB=-0.48‰,δ18OPDB=-8.82‰,87Sr/86Sr=0.70996;平均REE=15.08×10-6,δEu平均为0.70、δCe平均为0.78;鞍形白云石中的盐水包裹体的均一温度120～150℃,盐度为5％ ～ 12％ NaCleqv;溶洞中的粗-巨晶白云岩盐水包裹体的均一温度140～180℃,盐度为5％ ～ 18％ NaCleqv;与西加盆地惠而浦(Whirlpool point)剖面典型的热液白云岩相比较,乌里格孜塔格剖面中寒武系白云岩中缝洞中的粗-巨晶及鞍形白云石中的碳氧同位素、稀土总量、轻重稀土比均要高,但有序度、δEu、δCe、盐水包裹体形成温度及盐度相对低;因而推断它与西加盆地典型的岩浆期后热液来源不同,其流体来源于沿深部伸展走滑断裂-再循环地层热卤水,与海西晚期或燕山期-喜马拉雅期强烈挤压后弱伸展引起的二期或以上的压扭-走滑构造有关.  相似文献   

川西须家河组超致密砂岩成岩作用与相对优质储层形成机制   总被引：8，自引：2，他引：6  

吕正祥  刘四兵 《岩石学报》2009,25(10):2373-2383

川西须家河组砂岩是我国重要的天然气储层和产层,同时也是我国埋藏深度最大和最为致密的碎屑岩储层之一,在其超致密背景下发育有对天然气聚集有利的相对优质储层.须家河组砂岩埋藏后经历了复杂的成岩作用,相对优质储层中次生孔隙与原生孔隙并存.本文基于对川西须家河组超致密砂岩的岩石学、矿物学、地球化学和其它储层特征研究,总结了川西深埋藏条件下须家河组砂岩的成岩作用特征及其相对优质储层的形成机制.  相似文献   

歧口凹陷沙河街组成岩史分析和成岩阶段预测   总被引：20，自引：7，他引：13  

肖丽华  孟元林  牛嘉玉  王志国  殷秀兰  祝文亮  张连雪  王昕 《地质科学》2005,40(3):346-362

渤海湾盆地歧口凹陷超压对有机质热演化、有机酸生成和水岩反应具有明显的抑制作用。在化学动力学模型中加入超压因子增加反应活化能,即可用于超压条件下有机质热演化和成岩作用的模拟。歧口凹陷深层(>3500m)主要为沙河街组(始新—渐新世)。在沙河街组沉积末期沙河街组三段(沙三段)就进入晚成岩阶段A₁期,烃源岩开始生烃,生、储、盖层发育史与圈闭发育史匹配良好,油气藏开始形成。在东营组沉积时期(渐新世)—新近纪,沙河街组大部分地层处于晚成岩阶段A₁—A₂期,是其主要成藏期。现今沙河街组一段、二段和三段的上部仍处于晚成岩阶段A₁—A₂期,有利于油气藏的形成。然而,沙三段的下部在歧口凹陷的北部地区已进入晚成岩阶段BC期,镜质组反射率Ro≥1.3%,烃源岩处于高过成熟阶段,储层物性较差,不利于成藏,但在南部地区的沙三段下部还处于晚成岩阶段A₁-A₂期,生、储、盖层发育,是油气聚集的有利地区。  相似文献   

Geology and geochemistry of the sediment-hosted Cheshmeh-Konan redbed-type copper deposit,NW Iran     

《Ore Geology Reviews》2017

The several-hundred-m-thick Miocene Upper Red Formation in northwestern Iran hosts stratiform and fault-controlled copper mineralization. Copper enrichment in the percent range occurs in dm-thick carbonaceous sandstone and shale units within the clastic redbed sequence and consists of fine-grained disseminated copper sulfides (chalcopyrite, bornite, chalcocite) and supergene alteration minerals (covellite, malachite and azurite). The copper mineralization formed after calcite cementation of the primary rock permeability. Copper sulfides occur mainly as replacement of diagenetic pyrite, which, in turn, replaced organic matter. Electron microprobe analysis on bornite, chalcocite and covellite identifies elevated silver contents in these minerals (up to 0.12, 0.72 and 1.21 wt%, respectively), whereas chalcopyrite and pyrite have only trace amounts of silver (<0.26 and 0.06 wt%, respectively). Microthermometric data on fluid inclusions in authigenic quartz and calcite indicate that the Cu mineralization is related to a diagenetic fluid of moderate-to low temperature (Th = 96–160 °C) but high salinity (25–38 wt% CaCl₂ equiv.). The range of δ³⁴S in pyrite is −41.9 to −16.4‰ (average −31.4‰), where framboidal pyrite shows the most negative values between −41.9 and −31.8‰, and fine-grained pyrite has relatively heavier δ³⁴S values (−29.2 to −16.4‰), consistent with a bacteriogenic derivation of the sulfur. The Cu-sulfides (chalcopyrite, bornite and chalcocite) show slightly heavier values from −14.6 to −9.0‰, and their sulfur sources may be both the precursor pyrite-S and the bacterial reduction of sulfate-bearing basinal brines. Carbonates related to the ore stage show isotopically light values of δ¹³C_V-PDB from −8.2 to −5.1‰ and δ¹⁸O_V-PDB from −10.3 to −7.2‰, indicating a mixed source of oxidation of organic carbon (ca. −20‰) and HCO₃⁻ from seawater/porewater (ca. 0‰). The copper mineralization is mainly controlled by organic matter content and paleopermeability (intragranular space to large fracture patterns), enhanced by feldspar and calcite dissolution. The Cheshmeh-Konan deposit can be classified as a redbed-type sediment-hosted stratiform copper (SSC) deposit.  相似文献   

库车坳陷阳霞地区下侏罗统阿合组储层特征及储层发育的主控因素          下载免费PDF全文

刘卫红  高先志林畅松王鹤叶信林冉启贵 《地质科学》2017,(2):390-406

通过岩心及薄片观察,结合储层物性资料、粒度分析、扫描电镜、包裹体测温、粘土矿物X-衍射分析等多种资料和手段,对阿合组储层特征进行分析,定量研究了不同成岩作用对储层物性的影响,并对储层的影响因素做了进一步的探讨。结果表明阿合组储集空间主要为杂基微孔隙,其次为长石颗粒溶孔及粒内溶孔、粒间孔及粒间溶孔;储层物性差,为典型的特低孔-超低渗型储层;岩性是储层发育的物质基础,成岩作用中的压实作用是孔隙度减小的主要因素,胶结作用次之,溶蚀作用及矿物转化对储层物性有一定的改善作用;构造幅度的差异使得所处的成岩阶段具有差异性,进而造成阳霞地区北斜坡东部储层物性优于中西部。构造背斜转折端,孔隙度有所增大的同时,渗透率也有所增大,而背斜翼部微裂缝发育,孔隙度有所增加,渗透率变化不大。指出较好储层的分布地区和构造部位及其主控因素,对该区的油气勘探具有一定的理论指导意义。  相似文献   

Controls on reservoir quality in exhumed basins – an example from the Ordovician sandstone,Illizi Basin,Algeria     

《Marine and Petroleum Geology》2017

Petroleum exploration in many North African intracratonic basins targets Early Paleozoic sandstones as the primary reservoir objective. These sandstones are often characterized by highly variable reservoir quality (0.0001–1000 mD), and the ability to predict and selectively target areas of enhanced porosity and permeability is crucial to unlock the hydrocarbon potential. The objective of this study is to characterize the primary controls on reservoir quality in an Ordovician field in the Illizi Basin of Algeria through detailed core and petrographic analysis, and establish if variations in thermal history across the field have a material impact on reservoir quality. The best reservoir quality is observed in facies where primary intergranular porosity has been preserved in fine to coarse grained quartzarenites with less than 1% fibrous illite. These lithologies are most commonly found within the high-energy, tidally reworked, post-glacial facies sandstones of the uppermost Ordovician succession. Observed differences in quartz cement volume within compositionally and texturally similar samples from the southern and northern parts of the field are interpreted to reflect variations in thermal exposure due to deeper burial. This interpretation is supported by field-wide numerical modelling of sandstone diagenesis. This study indicates that subtle variations in thermal history can have a material impact on the spatial trends in reservoir permeability. Thermal history, therefore, is an important consideration in reservoir quality studies in exhumed basins where variations in present-day burial depth will be a poor guide for evaluating reservoir quality risk across a basin or play.  相似文献   

Overpressure preventing quartz cementation? – Comment to Stricker et al. (2016)     

《Marine and Petroleum Geology》2017

There is increasing evidence that quartz cementation can be viewed as a process controlled by temperature and insensitive to effective stress. This view of quartz cementation in sandstones is often referred to as the illite-mica induced dissolution model (IMID), which assumes quartz dissolution to occur along stylolites and clay laminae rather than at quartz-quartz grain contacts. In the present comment it is argued that the exceptional reservoir quality in the Skagerrak Formation of the Heron Cluster, North Sea, is due to grain coatings and rapid Cenozoic burial limiting the exposure to quartz cementation. This line of reasoning implies overpressure has had neglectable porosity preserving effect in the Heron Cluster.  相似文献