砂岩储层中原生孔隙的破坏与保存机制研究进展

埋藏条件下原生孔隙的破坏与保存机制是含油气盆地砂岩储层质量研究的一个核心领域,其在油气地质学研究中的意义不言而喻。与次生孔隙的形成与保存机制相比,影响原生孔隙破坏与保存的因素有着其特殊的复杂性和多样性。在总结国内外研究进展的基础上,试图深入理解不同成岩机制在砂岩储层原生孔隙破坏与保存中的意义和作用,包括破坏机制（如机械压实、胶结作用等）和保存机制（如地层超压、颗粒包膜、盐体侵位和烃类占位等）。目前难以实现砂岩储层质量钻前准确预测的一个困难在于无法明确原生孔隙演化的动力和过程,将来成岩作用、流体作用、沉积过程和盆地演化的更紧密结合可能是解决砂岩储层原生孔隙破坏与保存机制研究中最有希望的发展方向之一。     

松辽盆地北部泉三、四段储层物性影响因素分析

发育于泉头组三、四段的扶余油层和杨大城子油层是松辽盆地的主力油层之一,该油层低孔特低渗的物性特征制约了扶杨油层的勘探开发.为了研究松辽盆地北部泉三、四段储层物性的影响因素和低渗透储层的成因,本文以12 062组实测孔隙度和渗透率数据为基础,讨论了泉三、四段的物性影响因素.结果表明,总体上影响泉三、四段储层物性的主要因素...     

Composition, porosity, and reservoir potential of the Middle Jurassic Kashafrud Formation, northeast Iran

In the Kopet-Dagh Basin of Iran, deep-sea sandstones and shales of the Middle Jurassic Kashafrud Formation are disconformably overlain by hydrocarbon-bearing carbonates of Upper Jurassic and Cretaceous age. To explore the reservoir potential of the sandstones, we studied their burial history using more than 500 thin sections, supplemented by heavy mineral analysis, microprobe analysis, porosity and permeability determination, and vitrinite reflectance.The sandstones are arkosic and lithic arenites, rich in sedimentary and volcanic rock fragments. Quartz overgrowths and pore-filling carbonate cements (calcite, dolomite, siderite and ankerite) occluded most of the porosity during early to deep burial, assisted by early compaction that improved packing and fractured quartz grains. Iron oxides are prominent as alteration products of framework grains, probably reflecting source-area weathering prior to deposition, and locally as pore fills. Minor cements include pore-filling clays, pyrite, authigenic albite and K-feldspar, and barite. Existing porosity is secondary, resulting largely from dissolution of feldspars, micas, and rock fragments, with some fracture porosity. Porosity and permeability of six samples averages 3.2% and 0.0023 mD, respectively, and 150 thin-section point counts averaged 2.7% porosity. Reflectance of vitrinite in eight sandstone samples yielded values of 0.64-0.83%, in the early mature to mature stage of hydrocarbon generation, within the oil window.Kashafrud Formation petrographic trends were compared with trends from first-cycle basins elsewhere in the world. Inferred burial conditions accord with the maturation data, suggesting only a moderate thermal regime during burial. Some fractures, iron oxide cements, and dissolution may reflect Cenozoic tectonism and uplift that created the Kopet-Dagh Mountains. The low porosity and permeability levels of Kashafrud Formation sandstones suggest only a modest reservoir potential. For such tight sandstones, fractures may enhance the reservoir potential.     

Microfacies and diagenesis of older Pleistocene (pre‐last glacial maximum) reef deposits,Great Barrier Reef,Australia (IODP Expedition 325): A quantitative approach

During Integrated Ocean Drilling Program Expedition 325, 34 holes were drilled along five transects in front of the Great Barrier Reef of Australia, penetrating some 700 m of late Pleistocene reef deposits (post‐glacial; largely 20 to 10 kyr bp ) in water depths of 42 to 127 m. In seven holes, drilled in water depths of 42 to 92 m on three transects, older Pleistocene (older than last glacial maximum, >20 kyr bp ) reef deposits were recovered from lower core sections. In this study, facies, diagenetic features, mineralogy and stable isotope geochemistry of 100 samples from six of the latter holes were investigated and quantified. Lithologies are dominated by grain‐supported textures, and were to a large part deposited in high‐energy, reef or reef slope environments. Quantitative analyses allow 11 microfacies to be defined, including mixed skeletal packstone and grainstone, mudstone‐wackestone, coral packstone, coral grainstone, coralline algal grainstone, coral‐algal packstone, coralline algal packstone, Halimeda grainstone, microbialite and caliche. Microbialites, that are common in cavities of younger, post‐glacial deposits, are rare in pre‐last glacial maximum core sections, possibly due to a lack of open framework suitable for colonization by microbes. In pre‐last glacial maximum deposits of holes M0032A and M0033A (>20 kyr bp ), marine diagenetic features are dominant; samples consist largely of aragonite and high‐magnesium calcite. Holes M0042A and M0057A, which contain the oldest rocks (>169 kyr bp ), are characterized by meteoric diagenesis and samples mostly consist of low‐magnesium calcite. Holes M0042A, M0055A and M0056A (>30 kyr bp ), and a horizon in the upper part of hole M0057A, contain both marine and meteoric diagenetic features. However, only one change from marine to meteoric pore water is recorded in contrast with the changes in diagenetic environment that might be inferred from the sea‐level history. Values of stable isotopes of oxygen and carbon are consistent with these findings. Samples from holes M0032A and M0033A reflect largely positive values (δ¹⁸O: ?1 to +1‰ and δ¹³C: +1 to +4‰), whereas those from holes M0042A and M0057A are negative (δ¹⁸O: ?4 to +2‰ and δ¹³C: ?8 to +2‰). Holes M0055A and M0056A provide intermediate values, with slightly positive δ¹³C, and negative δ¹⁸O values. The type and intensity of meteroric diagenesis appears to have been controlled both by age and depth, i.e. the time available for diagenetic alteration, and reflects the relation between reef deposition and sea‐level change.     

Modern halite sedimentation processes and depositional environments,Hutt Lagoon,Western Australia

Abstract

Contemporary layered halite in the Hutt Lagoon, Western Australia, forms distinct precipitational and clastic fades, which are ascribed to seasonal ponding and playa development in the lagoon respectively. Field and laboratory documentation of the halite types and monitoring of surface water chemistry for several annual hydrologic cycles indicate that following evaporative concentration of ponded seawater halite layers, characterized by zoned and clear halite crystal varieties, are developed. During early stages of annual playa development, vadose solution and precipitation appear to be most active within and above the capillary fringe zone, causing diagenetic modification of the halite textures, fabrics and structures. Ultimately, clastic halite facies are produced by wind reworking of the earlier deposits, in response to progressive evaporative drawdown of the brine level in the main depression area of the lagoon.

The co-existence of the halite precipitates and clastites is related to a dynamic equilibrium in the water budget of the Hutt Lagoon. This equilibrium is best exemplified by limitation of brine level fluctuations to a narrow repetitive zone. Identification of similar early diagenetic features, such as vadose solution, precipitation, overgrowth, replacement and mechanical reworking of surface halite sediments, in ancient evaporite deposits may aid in a better understanding of the role of brine level fluctuation on genesis and diagenesis of subaqueous/subaerial halite.     

云南祥云马厂箐斑岩微量元素与稀土元素特征

马厂箐斑岩体与铜、钼、金等多金属矿成矿关系密切.斑岩体微量元素与稀土元素显示斑岩体物质来源具有壳幔混合特征.     

Redox status and heavy metal risk in intertidal sediments in NW Spain as inferred from the degrees of pyritization of iron and trace elements

Mariculture is an important economic activity in shallow marine areas of the Rías Baixas (Galicia, NW Spain). The maintenance of high product quality requires surveillance of environmental quality, including the risk of metal toxicity. In this study the redox status of intertidal sediments in the Bay of San Simón, and the risk of toxicity posed by their As, Cd, Cr, Cu, Mn, Ni, Pb and Zn contents, were evaluated by determination of operationally defined reactive, silicate-bound, organic and pyrite-related fractions of these elements and of Fe. The large silicate-bound fractions of most of these metals indicate their lithogenic origin; the main exception is Pb, which in all respects exhibits singular behaviour associated with its predominantly anthropogenic origin in a ceramics factory. In sediments with larger fine-grained particle contents, which are oxic only in the top few centimetres, greater proportions of the trace elements are present as sulphides or associated with sulphide minerals: the degree of pyritization of Fe (DOP) is 46% overall, and the pyrite fraction of some elements doubtless increases at the expense of the reactive fraction, most overall degrees of trace metal pyritization (DTMPs) lying in the range 10-50%. A decline in pyrite genesis at depths below about 18 cm in these sediments is attributed to the exhaustion of organic matter susceptible to metabolization by sulphide-generating bacteria. In coarse-grained, oxic sediments the oxidation of sulphides makes pyrite-related fractions very small, and reactive and silicate-bound fractions are negatively correlated; reactive fractions associated with Fe-Mn oxyhydroxides are large, and DOP and DTMPs are low (generally much lower than in mud-rich sediments), except for Pb. Most of the elements studied are mainly present in forms that are neither bioavailable nor potentially bioavailable, and so do not constitute a significant environmental threat. However, the high DTMPs of Cu and Pb indicate significant potential bioavailability, which should be taken into account in evaluations of environmental quality and the risk to bivalve cultures.     

Cadmium distribution in coastal sediments and mollusks of the US

Cadmium (Cd) concentrations in the coastal United States were assessed using the National Status and Trends (NS&T) Mussel Watch dataset, which is based on the analysis of sediments and bivalves collected from 280 sites since 1986. Using the 1997 sediment data, Pearson correlation (r = 0.44, p < 0.0001) suggested that Cd distributions in sediment can, be to some extent, explained by the proximity of sites to population centers. The 2003 tissue data indicated that “high” Cd concentrations (greater than 5.6 μg/g dry weights [dw] for mussel and 5.4 μg/g dw for oysters) were related to salinity along the East and Gulf coasts. Along the West coast, however, these “high” sites appeared to be related to upwelling phenomenon. Additionally, sedimentary diagenesis was found to be the most likely explanation of why sediment and mollusk Cd content were not well correlated.     

含油气盆地成岩作用的科学问题及研究前沿

1990年代以来成岩作用研究在国际沉积学中的地位已经发生重要转变,成岩作用研究群体或"共同体"已经初步形成。从岩石类型、地理-气候环境类型、成岩演化阶段、盆地类型等不同方面,本文概括和论述了成岩作用的知识体系,在此基础上提出了当今含油气盆地成岩作用的核心科学问题,即"盆地动力学过程控制的流体-岩石相互作用系统及其时空演变机制"。围绕该科学问题,并结合本专辑讨论的热点,进一步分析了成岩作用的盆地动力学背景、流体-岩石作用机制和分布、成岩圈闭和成藏条件、油气勘探开发应用等研究前沿及其存在问题,特别针对性地指出了我国含油气盆地成岩作用研究应该加大投入的领域。     

松辽盆地南部扶余油层砂岩成岩作用研究——以扶余油田和新立油田为例

对松辽盆地南部扶余油田和新立油田扶余油层砂岩岩石学特征和各成岩作用类型进行了细致分析,研究表明,扶余油田和新立油田的扶余油层主要类型分别为长石砂岩和长石岩屑砂岩,并经历了中等压实作用、自生石英胶结作用、自生粘土矿物胶结作用、碳酸盐胶结作用、交代和溶解作用等,达到晚成岩阶段A2亚期。该油层砂岩中碳酸盐胶结物主要为成岩早期的产物,当碳酸盐胶结物含量大于8%时,直接影响岩石的机械压实作用和油层的孔隙度。扶余油田扶余油层砂岩中长石含量相比新立油田高,可能导致该地区扶余油层砂岩的交代和溶解作用相对发育,从而抑制其内石英颗粒的次生加大,并形成高含量的自生高岭石,及因长石溶解所至的两个自生高岭石峰值特征等。