大布苏湖东岸“狼牙棒”地形成因探讨

经野外实地勘查研究,并采取土样进行易溶盐、孢粉分析,结合地貌形态特征与化验成果进行研究论证,认为“狼牙棒”地形的形成与其特殊的岩性条件和内、外动力地质作用相关,对“狼牙棒”地形形成机理进行探讨。     

东秦岭花岗岩的平均原子量及其与成岩成矿作用的关系

东秦岭不同构造单元中花岗岩类的平均原子量()有不同程度的差异。华北地台南缘为高值(20.65～21.15),秦岭褶皱系为中低值(20.35～20.43)。岩体的值与成岩物质来源和岩浆演化趋势有关,地台区花岗岩值介于“玄武岩地壳”平均值和“花岗岩地壳”平均值之间,而地槽区花岗岩则介于沉积壳层和花岗岩壳层之间。值东秦岭区域成矿作用分带与花岗岩的值分带有极明显的空间依存关系,成矿岩体的值远高于非成矿岩体,与金成矿作用有关岩体的值高于与铝多金属成矿作用有关的岩体。     

吉林省板石沟—旺文川绿岩带岩石地球化学特征及成岩环境分析

吉林省南部晚太古宙绿岩带位于龙岗古陆核南部边缘,它包括板石沟、四方山和旺文川绿岩带,其岩石主要为变质镁铁质火山岩和变质长英质火山岩,反映出具双峰式火山岩的特征。另外,本区绿岩带岩石的岩石化学和地球化学特征与龙岗古陆核北部边缘的夹皮沟绿岩带具有明显的差异,表明两者成岩环境不同。本区绿岩带斜长角闪岩属板内玄武岩,其成岩环境与大陆裂谷环境相似。     

Carbon and hydrogen isotope variation of plant biomarkers in a plant-soil system

Stable carbon (δ¹³C) and hydrogen (δD) isotopic compositions of n-alkanes, anteiso-alkanes, n-alkanoic acids, n-alkanols, phytol and sterols in raw leaves of Acer argutum and Acer carpinifolium, their fallen leaves, mold and soils from a natural Acer forest were measured in order to: (1) understand isotopic variation of the plant biomarkers in a plant-soil system and (2) evaluate which biomarker is the most effective recorder of soil vegetation. Long-chain (> C₂₄) n-alkanes, n-alkanoic acids and n-alkanols are gradually enriched in ¹³C up to 12.9‰ (average of 4.3‰) and depleted in D up to 94‰ (average of 55‰) from raw leaves to soils. However, anteiso-alkanes, phytol and sterols show little variation in both δ¹³C (< ± 1‰) and δD (< ± 2‰) from raw leaves to soils. These isotope signatures in a plant-soil system indicate that isoprenoid plant biomarkers such as sterols in soils faithfully preserve the isotopic compositions of dominant higher plants growing on the soils without a diagenetic effect upon the isotopic compositions. In contrast, long-chain n-alkyl molecules in soils undergo specific isotopic modification during biodegradation associated with early diagenesis and/or a significant contribution from heterotrophic reworking.     

四川盆地东部石炭系古岩溶储层成岩流体：来自流体包裹体、微量元素和C、O、Sr同位素的证据

相当Moscovian阶的石炭系黄龙组古岩溶储层是川东地区最重要的天然气储层类型之一。通过对石炭系古岩溶储层岩石组构、成岩演化序列以及铁锰锶微量元素、碳氧锶稳定同位素和流体包裹体综合研究,可将川东石炭系古岩溶型碳酸盐岩划分为古风化壳岩溶岩和埋藏岩溶岩两种成因类型,成岩流体可划分为三种类型:①古表生期大气水渗流-潜流成岩环境下的强氧化性低温大气水,流体具有富Fe和Mn、极低Sr含量、δ13C和δ18O值弱负偏以及极高87Sr/86Sr比值的性质;②中-深埋藏成岩环境下的强还原性深部混合热流体,属富Mn和Fe、贫Sr、δ18O值明显负偏性质的中-低温、含MgCl2-H2O、NaClMgCl2-H2O体系流体;③深埋藏成岩环境下的酸性压释水,属富Mn和Fe、δ13C值明显负偏性质的中-高温、含Na2SO4-H2O、Na2CO3-H2O、NaHCO3-H2O体系流体。各成岩流体对古岩溶储层发育具有重要的控制和影响作用,其中经强氧化性低温大气水的淋滤溶蚀形成孔、洞、缝非常发育的古风化壳型岩溶储层叠加后期的酸性压释水的溶蚀再改造,可大大改善储层的孔渗性,并在喜山期构造破裂作用下,最终形成川东石炭系规模性裂缝-孔隙型古岩溶储层。     

鄂尔多斯盆地旬邑地区三叠系延长组长9储层成岩作用及成岩相

通过铸体薄片、扫描电镜、高压压汞等方法对鄂尔多斯盆地旬邑地区三叠系延长组孔隙演化,并对储层成岩相进行划分。结果表明：旬邑地区长9 储层主要以长石砂岩和岩屑长石砂岩为主。压实作用及胶结作用是造成储层物性变差的主要原因,压实作用造成孔隙度降低约15.5%,胶结作用造成孔隙降低约13.6%。溶蚀作用对储层孔隙改善不明显,仅增加孔隙度约为1.98%。通过分析影响储层物性的主要成岩作用,综合实验测试数据将长9储层划分为4种成岩相：绿泥石膜-粒间孔相、长石溶孔-粒间孔相、碳酸盐致密胶结微孔相及塑性岩屑压实致密相等。其中绿泥石膜-粒间孔相、长石溶孔-粒间孔相为有利的成岩相带,主要分布在砂体中部区域。     

四川盆地开江-梁平台棚东侧长兴组礁白云岩沉积-成岩-成藏系统

长兴组礁白云岩是川东北地区最重要的天然气储层类型之一。通过对开江-梁平台棚东侧长兴组礁白云岩岩石组构、成岩演化序列、铁锰锶微量元素、碳氧锶稳定同位素、流体包裹体、油气性质及来源综合研究,认为古地貌格局控制了开江-梁平台棚东侧不同类型台缘生物礁的展布,古海平面的"升降"控制了生物礁形态及规模,台缘礁坪/礁盖滩微相及部分毗邻发育的骨架礁相带控制了优质储层发育位置和空间展布规律;可将长兴组白云岩划分为准同生白云岩和埋藏白云岩两种成因类型,优质的礁、滩相白云岩储层仅与多期次埋藏白云石化作用有关,推测成岩流体主要来源于封存地层中的早-中三叠世蒸发岩溶解产生的具低Mn含量、较低Fe含量、高Sr含量、较高δ~(13)C值、较高~(87)Sr/~(86)Sr比值特点的高盐度埋藏循环海源孔隙水,并有长兴期同生卤水和深部有机酸热液混入;按水文体制,将长兴组白云岩成岩系统划分为4类,分别为海源同生卤水、封存卤水、混源热卤水和深源混合热卤水成岩系统,认为混源热卤水成岩系统埋藏白云石化和溶蚀作用是提高储层质量的关键;论证了开江-梁平台棚东侧长兴组存在同一流体输导体系控制的埋藏白云石化作用与油气充注成藏的统一"成岩-成藏"系统,揭示了长兴组白云岩沉积-成岩-成藏耦合关系,为该地区下一步天然气勘探目标优选提供地质依据。     

Diagenetic alterations and reservoir heterogeneity within the depositional facies: A case study from distributary-channel belt sandstone of Upper Triassic Yanchang Formation reservoirs (Ordos Basin,China)

Diagenesis is of decisive significance for the reservoir heterogeneity of most clastic reservoirs. Linking the distribution of diagenetic processes to the depositional facies and sequence stratigraphy has in recent years been discipline for predicting the distribution of diagenetic alterations and reservoir heterogeneity of clastic reservoirs. This study constructs a model of distribution of diagenetic alterations and reservoir heterogeneity within the depositional facies by linking diagenesis to lithofacies, sandstone architecture and porewater chemistry during burial. This would help to promote better understanding of the distribution of reservoir quality evolution and the intense heterogeneity of reservoirs. Based on an analogue of deltaic distributary channel belt sandstone in Upper Triassic Yanchang Formation, 83 sandstone plug samples were taken from 13 wells located along this channel belt. An integration of scanning electron microscopy, thin sections, electron microprobe analyses, rate-controlled porosimetry (RCP), gas-flow measurements of porosity and permeability, and nuclear magnetic resonance (NMR) experiments, together with published data, were analysed for the distribution, mineralogical and geochemical characteristics of detrital and diagenetic components and the distribution of reservoir quality within the distributary channel belt.Distribution of diagenetic alterations and reservoir heterogeneity within the distributary channel belt sandstones include (i) formation of high quality chlorite rims in the middle part of thick sandstones with coarser grain sizes and a lower content of ductile components resulted from the greater compaction resistance of these sandstones (providing larger pore spaces for chlorite growth), leading to formation of the intergranular pore – wide sheet-like throat and intergranular pore - intragranular pore – wide sheet-like throat (Φ>15%, k>1mD) in the middle part of thick sandstones; (ii) formation of thinner chlorite rims in the middle part of thinner sandstones is associated with the intergranular pore - intragranular pore – narrow sheet-like throat (9%<Φ<14%, 0.2mD<k<0.8mD); (iii) strong cementation by kaolinite in the more proximal sandstones of distributary channel owing to the strong feldspar dissolution by meteoric water, resulting in the intragranular pore - group of interstitial cement pores – narrow sheet-like throat/extremely narrow sheet-like throat (8%<Φ<11%, 0.1mD<k<0.3mD) due to the pore-filling kaolinite occluding porosity; (iv) formation of dense ferrocalcite zones (δ¹⁸O_VPDB = −23.4‰ to −16.6‰; δ¹³ C_VPDB = −4.0‰ to −2.3‰) favoured in the top and bottom of the channel sandstone which near the sandstone-mudstone bouding-surface, destroying pore space (Φ<8%, k<0.1mD); (v) strong compaction in sandstone of distributary channel edge laterally as a result of fine grain size and high content of ductile components in those sandstones, forming the group of interstitial cement pores – extremely narrow sheet-like throat with porosity values less than 8%.     

Mineral types and organic matters of the Ordovician-Silurian Wufeng and Longmaxi Shale in the Sichuan Basin,China: Implications for pore systems,diagenetic pathways,and reservoir quality in fine-grained sedimentary rocks

Mineral types (detrital and authigenic) and organic-matter components of the Ordovician-Silurian Wufeng and Longmaxi Shale (siliceous, silty, argillaceous, and calcareous/dolomitic shales) in the Sichuan Basin, China are used as a case study to understand the control of grain assemblages and organic matter on pores systems, diagenetic pathway, and reservoir quality in fine-grained sedimentary rocks. This study has been achieved using a combination of petrographic, geochemical, and mercury intrusion methods. The results reveal that siliceous shale comprises an abundant amount of diagenetic quartz (40–60% by volume), and authigenic microcrystalline quartz aggregates inhibit compaction and preserve internal primary pores as rigid framework for oil filling during oil window. Although silty shale contains a large number of detrital silt-size grains (30–50% by volume), which is beneficial to preserve interparticle pores, the volumetric contribution of interparticle pores (mainly macropores) is small. Argillaceous shale with abundant extrabasinal clay minerals (>50% by volume) undergoes mechanical and chemical compactions during burial, leading to a near-absence of primary interparticle pores, while pores preserved between clay platelets are dominant with more than 10 nm in pore size. Pore-filling calcite and dolomite precipitated during early diagenesis inhibit later compaction in calcareous/dolomitic shale, but the cementation significantly reduces the primary interparticle pores. Pore-throat size distributions of dolomitic shale show a similar trend with silty shale. Besides argillaceous shale, all of the other lithofacies are dominated by OM pores, which contribute more micropores and mesopores and is positively related to TOC and quartz contents. The relationship between pore-throat size and pore volume shows that most pore volumes are provided by pore throats with diameters <50 nm, with a proportion in the order of siliceous (80.3%) > calcareous/dolomitic (78.4%) > silty (74.9%) > argillaceous (61.3%) shales. In addition, development degree and pore size of OM pores in different diagenetic pathway with the same OM type and maturity show an obvious difference. Therefore, we suggest that the development of OM pores should take OM occurrence into account, which is related to physical interaction between OM and inorganic minerals during burial diagenesis. Migrated OM in siliceous shale with its large connected networks is beneficial for forming more and larger pores during gas window. The result of the present work implies that the study of mineral types (detrital and authigenic) and organic matter-pores are better understanding the reservoir quality in fine-grained sedimentary rocks.     

歧口凹陷西坡白水头构造沙一段下部油气成藏期次研究

根据储层的成岩序次、油气包裹体特征及含烃盐水包裹体均一温度,结合构造活动特征及烃源岩的演化史,对歧口凹陷西坡白水头构造沙一段下部油气藏进行了成藏期次综合研究。认为该油气藏有三期油气充注过程:第一期发生在馆陶组末到明化镇组下段沉积早中期,约为11.5～8Ma,源区沙三段烃源岩有机质处于低成熟阶段,油气来源不足,成藏规模小;第二期发生在明化镇下段沉积末期到明化镇上段沉积初期,约为5Ma±,白水头构造各主要断层活动强烈,沙三段烃源岩开始进入生排烃高峰,油气运聚规模较大;第三期发生在明化镇上段沉积中晚期到第四系初期,约为3.5～2Ma,烃源岩整体处于生排烃高峰,各大断层活动有所减弱,但仍控制着油气的大规模垂向运移,成藏规模大。