含片钠铝石砂岩的基本特征及地质意义

含片钠铝石砂岩是一种含片钠铝石自生矿物的砂岩,一般为富含长石的砂岩,与片钠铝石稳定共生的自生矿物主要为铁白云石、菱铁矿等碳酸盐矿物。砂岩中片钠铝石的含量变化较大,其存在与否不受砂岩结构的制约。含片钠铝石砂岩往往分布在断裂和岩浆岩体附近,既可以作为CO2气储层,又可以作为油气储层。含片钠铝石砂岩是一种具有特殊地质意义的砂岩,表现为：①含片钠铝石砂岩记录了深、浅部层圈之间及烃源岩—储层之间的物质转移;②在含油CO2气藏和油藏中,含片钠铝石砂岩记录了CO2与油气双重充注,其中含油CO2气藏中的含片钠铝石砂岩记录了CO2充注驱油现象;③含片钠铝石砂岩是进行CO2地下储存研究的理想的天然实验室。     

鸡西盆地下白垩统含煤层系低孔低渗砂岩的成因探讨

黑龙江鸡西盆地下白垩统城子河组和穆棱组是主要的含煤系地层,岩石类型为长石岩屑砂岩和岩屑长石砂岩,成岩作用主要为压实作用、胶结作用、溶蚀溶解作用及交代作用等,露头砂岩经历了表生成岩作用。压实作用和胶结作用是储层砂岩物性差的重要原因,二者相比,前者对该区孔隙度减少贡献更大。对比露头砂岩与岩芯砂岩,露头砂岩的储层物性更好。     

龙门山南段前陆盆地中-新生代砂岩特征及物源分析

龙门山南段前陆盆地发育了巨厚的陆源沉积岩,其中砂岩分布最广、含量最多。在详细观察描述砂岩宏观特征的基础上,通过薄片鉴定、粒度分析等方法,研究了中—新生代砂岩的物质成分及结构特征,指出砂岩的成分成熟度和结构成熟度均中等至低,并按成分—成因分类方法划分了砂岩的岩石类型。根据砂岩特征,分析岩石的组成物质来源于龙门山造山带,再结合前陆盆地充填地层的沉积特征,提出了砂岩的沉积模式。     

鄂尔多斯盆地白垩系含水砂岩的特征

最新水文钻孔和露头剖面调查测试资料对鄂尔多斯盆地白垩系含水砂岩的组分特征和空间分布综合研究表明,宜君-洛河含水岩组广泛分布于全盆地,为最主要的区域性含水岩组,以长石石英砂岩、长石砂岩、岩屑长石砂岩发育为主;华池-环河含水岩组分布广泛,也是很好的含水岩组,主要为长石砂岩、长石石英砂岩、岩屑长石砂岩：罗汉洞-泾川含水岩组仅局限于盆地北部和西部,是一套比较局部的含水层,主要为长石石英砂岩和岩屑石英砂岩。总体上,盆地北部白垩系含水砂岩极其发育,南部含水砂岩具多层分布的特点,厚度总体较小。     

Gravity erosion and lithology in Pisha sandstone in southern Inner Mongolia

Pisha sandstone is a soft rock found in the southern zone of the Inner Mongolia Autonomous Region of Inner Mongolia. The presence of soft Pisha sandstone in the middle reaches of the Yellow River coincides with large areas of bedrock erosion in the river's basin, with the average total erosion modulus as high as 44 570 t/(km~2·a). Such high levels of erosion are one of the main sources of coarse mud and sands in the Yellow River. Erosion by gravitational forces such as snow glide and landslip are the main erosion types in Pisha sandstone region. The gravity erosion modulus can be as high as 25 615 t/(km~2·a), accounting for 30.6% of the total average erosion. Our paper investigates the characteristics of Pisha sandstone in relation to the development of gravity erosion mechanisms. We conducted field investigations in Pisha sandstone region for original state rock sampling. Test results from analyses of the rock properties indicate that the mineral composition, structure and microstructure characteristics of Pisha sandstone determine its varying capacity to resist weathering. Degrees of weathering in slightly different lithological layers of Pisha sandstone lead to different erosion rates. In this way, erosion forces combined with the varying lithological strata in the rock aggravate gravitational erosion in Pisha sandstone.     

崩解性砂软岩改良弱膨胀土性状实验研究

引江济淮河(航)道工程引江济巢段和江淮沟通段地层连续分布弱膨胀土和具有崩解性的砂软岩,为资源化利用河道开挖弃渣开发非膨胀土来源,实验研究利用崩解性软岩改良弱膨胀土的可行性。研究表明:崩解性砂软岩易粉碎、无膨胀性、天然含水率低,具备作为改性材料的条件;弱膨胀土掺入崩解性砂岩后其膨胀率、膨胀力、最优含水率与掺入量负相关,最大干密度、渗透系数与掺入量正相关;弱膨胀土掺入崩解性砂岩后其内摩擦角随掺量呈反S型曲线规律发展,黏聚力随掺量增加近似呈二次曲线规律衰减,掺量高于30%时,改良土的抗剪强度可能低于天然弱膨胀土;在砂岩掺量及粒径范围相同情况下,砂岩粗颗粒含量越高,改良土的黏聚力越高和摩擦角越低;砂岩改良土在干湿循环条件下的强度稳定性得到改善,且水化砂岩的改良效果优于机碎砂岩。以弱膨胀土改良后强度不损失为标准,确定砂岩合理掺量为30%,并须合理控制砂岩改良土施工过程中机碎砂岩中粗粒组的含量。     

南海北部白云深水区高变地温梯度砂岩渗透率定量预测

地温梯度如何影响砂岩成岩演化和储层物性变化是地学界的热点问题. 以具有高变地温梯度特征的白云深水区为例,通过分析大量不同地温梯度地区的样品,以地温梯度0.1~0.2 ℃/100 m为递进间隔,对比分析了不同地温梯度区间内不同粒度砂岩储层渗透率随埋藏深度变化的趋势,建立了砂岩渗透率的定量地质预测模型,展示了砂岩渗透率与地温梯度之间的内在联系. 结果表明,一定埋深范围内,随地温梯度升高,渗透率每下降一个数量级,砂岩埋深下限差异呈台阶式减少;相同地温梯度区间内,高成分成熟度、低塑性岩屑含量的含砾砂岩、粗粒砂岩、中粒砂岩和细粒砂岩的渗透率下降程度不同,相邻粒径砂岩等效渗透率埋深下限差异相近,随地温梯度增加,相邻粒径砂岩等效渗透率下限埋深差异呈规律性减小;低渗与特低渗砂岩储层的地层深度段随地温梯度升高而明显变小,粗粒砂岩特低渗储层的埋深下限可作为白云深水区常规油气勘探的极限深度. 研究成果对于揭示地温梯度对砂岩成岩演化作用的影响及物性演变效应具有重要的意义,对油气勘探有积极的指导作用.      

Architecture of a tide-influenced river delta in the Frontier Formation of central Wyoming, USA

The Frewens sandstone is composed of two elongate tide-influenced sandstone bodies that are positioned directly above and slightly landward of a more wave-influenced lobate sandstone. The 20-km-long, 3-km-wide Frewens sandstone bodies coarsen upwards and fine away from their axes, have gradational bases and margins and have eroded tops abruptly overlain by marine shales. These sandstones are superbly exposed in large cliffs on the banks of the South Fork of the Powder River in central Wyoming, USA. The deposits change upwards from thinly interbedded sandstones and mudstones to metre-thick heterolithic cross-strata and, finally, to metres-thick sandstone-dominated cross-strata. There is abundant evidence for tidal modulation of depositional flows; however, palaeocurrents were strongly ebb-dominated and nearly parallel the trend of sandstone-body elongation. Detailed mapping of stratal geometry and facies across these exposures shows a complex internal architecture. Large-scale bedding units within sandstone bodies are defined by alternations in facies, bed thickness and the abundance of shales. Such bedsets are inclined (5°–15°) in walls oriented parallel to palaeoflow and gradually decrease in dip over hundreds of metres as they extend from the sandstone-dominated deposits higher in a sandstone body to muddier deposits lower in the body. Where viewed perpendicular to palaeoflow, bedsets are 100-metre-wide lenses that shingle off the sandstone-body axis towards its margins. The sandstone bodies are interpreted as sand ridge deposits formed on the shoreface of a tide-influenced river delta. Metres-thick cross-strata in the upper parts of sandstone bodies resemble deposits of bars (sandwaves) formed where tidal currents moved across shallows and the tops of tidal ridges. Heterolithic deposits lower in sandstone bodies record fluctuating currents caused by ebb and flood tides and varying river discharge. Erosion surfaces capping sandstone bodies record tidal ravinement. The tidal ridges were abandoned following transgression and covered with marine mud as waters deepened.     

Sedimentology of a late Cambrian regressive sequence (bowers group), Northern Victoria land,Antarctica

The late Cambrian Bowers Group is regressive marine to non-marine. On the basis of associations of textures and sedimentary structures (both primary and biotic), and of palaeocurrent measurements, the sediments of the newly defined Mariner Formation appear to have accumulated on a platform or continental shelf of low gradient and narrow tidal range. Trilobite- and brachiopod-bearing fissile mudstone with sparse channels and scattered stratified sandstone (open marine) is succeeded by wavy-bedded and lenticular-bedded mudstone, muddy sandstone, and rippled sandstone with bands rich in brachiopods (shallow open marine), then mudstone and laminated sandstone with lenticular bodies of oosparite (open marine shoals and protected inner shelf), and red and green, ripple- and parallel-laminated sandstone, interbedded with burrowed muddy sandstone and mudstone, with lenticular bedding (tidal flat). The sharply overlying Camp Ridge Quartzite of cross-bedded sandstone, pebbly sandstone, and sandy pebble conglomerate, is regarded as braided channel alluvium.The detritus appears to have been derived from veined low-grade metamorphic rocks and fine-grained detrital sedimentary rocks that lay south of the area.     

风化砂岩的力学特性及本构关系研究

以不同风化程度的砂岩试件为研究对象,对其单轴、三轴力学强度进行了试验研究。结果表明,随着风化程度的增加,砂岩的力学强度逐渐降低;三轴曲线的主应力差 对砂岩强度的影响基本呈线性;不同风化程度的砂岩试件的内摩擦角随着风化程度的增加,摩擦角逐渐增大;而凝聚力则随着风化程度的增加而减小。建立了岩石三轴受力的抛物曲线-线弹性-Duncan双曲线-塑性软化-残余理想塑性5段式模型,模型能够正确反映砂岩三轴受力变形特点。     

塔里木盆地古生界砂岩热成熟度与有效储层的预测

根据砂岩热成熟的概念，认为塔里木盆地古生界砂岩的孔隙度主要受控于与地热场、埋藏时间和盆地沉降有关的砂岩热成熟度。用热成熟度比用深度可更合理地解释砂岩孔隙度的发育特征及其成因。ＴＴＩ值可综合反映热成熟程度，ＴＴＩ值越大，砂岩的热成熟度越高，成岩强度越大，被保存的孔隙度越小。若已知盆地的地温梯度，可计算出预测储层的ＴＴＩ值，并可用本文提出的砂岩热成熟度－－孔隙度和热成熟度－－深度的两个定量关系预测砂岩     

The Effects of Diagenesis on the Reservoir Characters in Ridge sandstone of Jurassic Jumara dome,Kachchh, Western India

Ridge sandstone of Jurassic Jumara dome of Kachchh was studied in an attempt to quantify the effects of diagenetic process such as compaction, cementation and dissolution on reservoir properties. The average framework composition of Ridge sandstone is Q₈₀F₁₇L₃, medium-to coarse grained and subarkose to arkose. Syndepositional silty to clayey matrix (3% average) is also observed that occurs as pore filling. The diagenetic processes include compaction, cementation and precipitation of authigenic cements, dissolution of unstable grains and grain replacement and development of secondary porosity. The major cause of intense reduction in primary porosity of Ridge sandstone is early cementation which include silica, carbonate, iron, kaolinite, illite, smectite, mixed layer illite-smectite and chlorite, which prevents mechanical compaction. The plots of COPL versus CEPL and IGV versus total cement suggest the loss of primary porosity in Ridge sandstone is due to cementation. Cements mainly iron and carbonate occurs in intergranular pores of detrital grains and destroys porosity. The clay mineral occurs as pore filling and pore lining and deteriorates the porosity and permeability of the Ridge sandstone. The reservoir quality of the studied sandstone is reduced by clay minerals (kaolinite, illite, smectite, mixed layer illitesmectite, chlorite), carbonate, iron and silica cementation but on the other hand, it is increased by alteration and dissolution of the unstable grain, in addition to partial dissolution of carbonate cements. The potential of the studied sandstone to serve as a reservoir is strongly related to sandstone diagenesis.     

Testing of Sydney dimension sandstone for use in the conservation of heritage buildings

This paper deals with the scientific assessment of the physical properties of sandstone used in the conservation of Sydney's historic heritage sandstone buildings. The local Hawkesbury Sandstone has been widely used for all manner of constructions since the early days of the first settlement. In the nineteenth century, dimension sandstone quarries existed all over the Sydney region, and the demand for the stone was great. During this time, a true ‘freestone’ known as ‘yellow block’ sandstone, in which bedding planes were absent, was quarried extensively. This sandstone is also known as a ‘self-colouring’ sandstone, where the rock, although grey when quarried, turns a yellow–brown after a few months exposure to the atmosphere. It can be easily carved and was eminently suitable for the ornate Victorian architecture of the time. There are very few quarries within the Sydney region today capable of producing ‘yellow block’ sandstone. Whenever possible, sandstone from suitable building excavations, particularly on the Pyrmont Peninsula, is used for this work. Conservation work is extremely expensive and the building elements that most need replacement, the overhanging and decorative elements, are usually those that cost the most. It is essential that the most durable replacement stone be selected. Thus, a strict regime of scientific testing is used for any major conservation project, in order to determine the physical properties of possible replacement stone. This is the province of the geologist and involves visual observation in the quarry or excavation, which is a simple, cost-effective means of weeding out poor quality stones, followed by laboratory engineering tests to establish the physical parameters of a sandstone and finally, petrographic analysis. The results of such tests, combined with careful sampling, ensure the best possible quality of replacement material.     

煤层顶板砂岩富水性AVO预测技术

煤层顶板砂岩富水性预测是有待解决的重要问题。以实际测井曲线数据为输入,利用Gassmann方程和AVO（Amplitude Variation with Offset）技术探讨煤层顶板砂岩富水性的预测方法。首先,利用实际测井曲线计算顶板砂岩的纵波速度、孔隙度和泥质含量;其次,以Han经验公式为基础,曲面拟合纵波速度、孔隙度和泥质含量间的关系式,并导出砂岩骨架纵波速度;再次,利用Castagna经验公式计算砂岩骨架的横波速度,并建立14种顶板砂岩模型;最后,利用Gassmann方程进行流体替换,计算各模型的纵横波速度和密度,从而正演模拟顶板砂岩的AVO响应。结合理论分析和实例预测,发现截距-梯度交会图可以区分砂岩孔隙度和干湿性,是顶板砂岩富水性预测的一种有效手段。      

Numerical Simulation of the Influence of Pore Structure on Resistivity,Formation Factor and Cementation Index in Tight Sandstone

Tight sandstone,with severe diagenesis and complex pore structure,differs greatly from conventional sandstone in terms of rock electrical parameters.In subsurface rock electrical experiments,various electrical parameters are confounded and can only be analyzed qualitatively.The lack of quantitative analysis for each individual electrical parameter presents a challenge for the evaluation of oil and gas saturation in tight sandstone.Based on the 2D pore-throat model and the features of pore structure in the tight sandstone of the Penglaizhen and Shaximiao Formations in the upper and middle Jurassic of the Western Sichuan Depression,this paper presents 3D micro pore-throat models for three types of tight sandstone.It proposes a finite element-based rock electrical simulation method to analyze the influence of pore structure parameters,such as throat radius and throat tortuosity,on electrical parameters such as resistivity,formation factor,and cementation index quantitatively.The research revealed the following results:(1)Throats of tight sandstone usually have lamellar or curved lamellar shapes that are slender and narrow.The lamellar throat used in the proposed porethroat model is more consistent with the features of tight sandstone than the tubular throat used in the original model.(2)The throat determines the conductivity of tight sandstone.The throat parallel to the electric potential has the greatest influence on conductivity,and the throat perpendicular to the potential has the least influence.(3)In tight sandstone grades I to III,as the porosity decreases,the formation factor increases and the cementation index decreases.(4)The results of the rock electrical simulation are consistent with the results of the rock electrical experiment,which indicates that the proposed rock electrical simulation method of tight sandstone is effective and accurate.     

不同埋深条件下砂泥岩互层中砂岩储层物性变化规律

砂泥岩组合方式在不同埋深条件下影响了砂泥岩界面附近储层的物性。在浅—中等埋藏条件下(深度 <2 5 0 0 m )砂泥岩界面附近的砂岩物性好于内部 ;在深埋藏条件下 ,砂泥岩组合方式、与砂岩接触的泥岩厚度以及砂泥岩的相对厚度比例对砂泥岩界面附近的砂岩物性影响很大。在泥岩夹砂岩的情况下 ,当砂岩厚度极薄、比例极低时砂岩物性很差 ;当砂岩厚度增大到中—厚层时 ,则从砂岩内部某一点开始向砂泥岩界面 ,物性逐渐降低 ,顶底界面都存在一个约为砂层厚度 1/ 5～ 1/ 4的物性过渡带 ;在上泥下砂或下泥上砂的情况下 ,仅在与厚层泥岩接触一侧的砂岩界面处出现物性过渡带。在砂泥岩近于等厚互层的情况下砂岩界面附近物性仍比内部差 ,且随着砂岩单层厚度减薄、厚度比例降低 ,泥岩比例增高 ,砂岩的物性越来越差。在砂岩夹泥岩的情况下 ,砂泥岩界面附近与砂岩内部物性趋于一致 ,物性过渡带消失。这一现象与泥岩的成岩演化密切相关 ,浅—中等埋藏条件下泥岩排出的为低矿化度、富含有机酸的流体 ,在砂泥岩界面附近溶蚀作用强于内部 ;在深埋条件下 ,从泥岩内排出的 K 、Na 、Ca2 、Mg2 、Fe3 与 Si4 等物质以沉淀为主 ,砂泥岩界面附近胶结强于内部 ,泥岩的厚度越大 ,影响就越强     

油气成藏条件下低渗透砂岩石油运移的渗流特征实验研究

在室内低速渗流实验的基础上,采用恒压测试法,对成藏条件下石油在低渗透砂岩中的运移渗流规律及影响因素进行了研究。结果表明：(1)石油在低渗透砂岩中低速渗流时存在着启动压力梯度,非达西渗流特征明显。(2)低渗透砂岩中石油非达西渗流曲线主要有两种基本类型,视流度≤1时,非达西渗流曲线表现为上凹型曲线;视流度＞1时,表现为变性达西流曲线。(3)低渗透砂岩的物性、石油性质以及它们的相互作用对渗流曲线的位置、非线性段的曲率和变化范围以及直线段在压力梯度轴的截距具有重要影响。(4)随着低渗透砂岩渗透率的降低和石油粘度的增加或视流度的减小,石油在低渗透砂岩储层的非达西渗流特征更加明显。     

Cyclicity in early Permian fluviatile Gondwana coal measures: An example from Giridih and Saharjuri basins,Bihar, India

The Karharbari and Barakar coal measures of Giridih and Saharjuri basins of Bihar, eastern India, comprise an interbedded assemblage of sandstone, shale and coal in variable abundance. The lithofacies composition records a progressive decrease in sandstone and enrichment of shale and coal from Karharbari up to Barakar. Application of first-order embedded Markov-chain statistics to subsurface data of Karharbari (52 borehole logs) and Barakar (10 borehole logs) reveals that deposition in both the coal measures followed a Markovian mechanism with variable probability, to yield a sequence of upward transition from sandstone through shale to coal. The repetitive fining-upward cycles are asymmetrical, i.e. sandstone → shale → coal → sandstone in the case of Karharbari, but symmetrical as sandstone → shale → coal → shale in Barakar.The abundance of sandstone and the asymmetrical nature of Karharbari cycles are attributed to abrupt shifting of channel bars in low-sinuosity anabranching streams. By contrast, the subequal amount of sandstone, shale and coal forming symmetrical cycles in the overlying Barakar Formation is due perhaps to a slow and gradual shift of the stream channels over and across the adjacent subenvironments of the flood plain.     

滇东威信地区龙潭组致密砂岩矿物组成特征及其油气地质意义

致密气是发育于低孔、特低渗透砂岩中的一种非常规资源,具有丰富的潜在油气储量,但由于其致密低渗透性,压裂改造是致密气高效开发的必须手段,而砂岩储集特征及物质组成对初步评价致密砂岩储层的资源潜力和生产能力有重要意义.运用X射线衍射、显微镜及扫描电镜等技术手段,对滇东威信地区二叠系龙潭组10个致密砂岩露头样品进行定性和定量分...     

库车坳陷依南2“连续型”致密砂岩气藏成藏临界物性条件

“连续型”致密砂岩气藏是一种重要的非常规油气资源.恢复储层临界物性条件的演化对于揭示致密砂岩气成藏机理及成藏过程具有重要的理论意义.以库车坳陷依南2“连续型”致密砂岩气藏为例,利用数值模拟方法结合盆地模拟技术,恢复了储层临界物性的演化过程,并根据临界物性条件和储层演化的耦合关系,确定了该地区“连续型”致密砂岩气藏可以成藏的最早时间.研究表明,“连续型”致密砂岩气成藏临界物性并不是固定不变的,它随着地质条件的变化而不断发生改变.依南2“连续型”致密砂岩气藏最早的形成时间为距今9 Ma,对应的临界孔隙度为6.95%;现今储层临界孔隙度为7.26%.结合实际地质情况进一步证实了依南2气藏为“连续型”致密砂岩气藏.