Effect of image segmentation & voxel size on micro-CT computed effective transport & elastic properties     

《Marine and Petroleum Geology》2017

Digital rock technology is rapidly evolving interdisciplinary field with many promises, including fast turnaround times for core analysis, repeatable analysis, and multiphysics simulation. We study the impact of the image segmentation threshold and image voxel size on image-computed permeability, elastic moduli, and electrical conductivity. Improved quantitative understanding of such effects is critically important when comparing laboratory-measured rock properties with those computed on digital images of rocks. We analyze properties of over 500 binary microstructures (each of size 1024³ voxels) segmented using different segmentation algorithms. We find that uncertainty in computed rock properties, induced due to the choice of segmentation threshold, increases with coarsening of image voxels. Segmentation of the same rock, acquired with different voxels sizes, lead to small variations in porosity but induces relatively large variation in flow and electrical rock properties. This uncertainty is larger for rocks of lower porosity. We find that coarsening of image voxels also leads to rounding and smoothing of pore throats and a sharp decline in specific surface area which results in an increase in computed permeability. We propose simple models to remove the bias in rock properties when image-derived porosity is either overestimated or underestimated due to the choice of the segmentation threshold. This approach is particularly useful when comparing laboratory-measured rock properties to those derived from digital rocks since often the image calculated porosity and the laboratory-measured porosity are not the same. Even after such corrections, the impact of finite image voxel size would still need to be compensated.  相似文献   

墨西哥中——新生代成矿系列和成矿带划分及其大地构造意义   总被引：1，自引：0，他引：1  

王翠芝  雷华  姚仲友  赵珍梅  谢其锋  王力圆  林木森  范明森  陈丽华 《地质通报》2017,36(12):2116-2123

墨西哥是矿产资源大国,其中产量最高的包括银、铜、铁、铅锌等。这些矿产的生成主要源于多种多样的矿床类型和各式各样的矿化类型,其中浅成低温热液型、斑岩型、矽卡岩型、IOCG(铁氧化物铜金)型是最突出的矿床类型。这些矿床的形成与北科迪勒拉山系的形成有关,体现了联合大陆长期积聚或解体的某些阶段,尤其是中新生代成矿带的空间展布特征与其形成的大地构造环境密切相关。划分的9个构造-岩浆-成矿带,分别形成3个俯冲成矿系列,即从沿海到内陆依次发育的IOCG型铁铜金成矿带→斑岩型铜钼金成矿带→浅成低温热液型银金多金属成矿带,分别代表太平洋古板块、法拉隆板块和科科斯板块向北美板块从俯冲、挤压到碰撞后伸展的板块构造岩浆成矿环境。这类俯冲边界型成矿系统的主体部分是西马德里造山带岩浆弧中的斑岩型铜钼矿成矿系统和盆岭省中的火山岩控制的浅成低温热液型银金矿成矿系统。  相似文献   

Errata     

《国际泥沙研究》2014,29(2):183

  相似文献   

华南地区晚三叠世含煤岩系层序—古地理   总被引：1，自引：0，他引：1       下载免费PDF全文

邵龙义  李英娇  靳凤仙  高彩霞  张超  梁万林  黎光明  陈忠恕  彭正奇  程爱国 《古地理学报》2014,16(5):613-630

在对露头及钻孔剖面沉积特征研究的基础上,建立了华南地区晚三叠世含煤岩系层序地层格架,恢复了基于三级层序的岩相古地理,并分析了聚煤规律。根据岩相特征及岩相组合类型,在区内晚三叠世含煤地层中识别出陆相和海陆过渡相两大沉积类型,并可进一步识别出冲积扇、河流(包括辫状河和曲流河)、三角洲、湖泊、潮坪—潟湖、滨海平原和滨浅海等7种沉积类型。陆相沉积主要发育在上扬子地区的四川盆地;海陆过渡相沉积主要发育在东南部湘赣粤滨浅海。在晚三叠世含煤岩系中识别出区域性不整合面和构造应力转换面、砂砾岩体底部冲刷面和岩性突变面等类型的层序界面,将含煤岩系划分为5个三级层序。以三级层序为古地理作图单元,恢复了研究区的古地理格局。由煤层厚度与岩相古地理平面展布规律可知,最有利的成煤环境为三角洲沉积体系,其次为河流、潮坪—潟湖沉积体系,聚煤中心主要分部在四川盆地的乐威煤田以及华蓥山煤田、湘赣粤滨浅海地区的湘东南至赣西萍乡一带。  相似文献   

Paleomagnetism of the 1.88-Ga Sokoman Formation in the Schefferville–Knob Lake area,Québec,Canada, and implications for the genesis of iron oxide deposits in the central New Québec Orogen     

《Precambrian Research》2004,128(1-2):167-188

Thirty-nine oriented block samples of iron-formation were collected at 13 sites, including opposite limbs of major folds, from the 1.88-Ga Sokoman Formation (Knob Lake Group) in the Schefferville–Knob Lake area of the central New Québec Orogen, northern Québec. The samples assayed up to 80.24% Fe₂O₃T (54.08% Fe), implying Fe-enrichment of the iron-formation up to ore grade. Anisotropy of magnetic susceptibility measurements on 245 standard specimens indicate a well preserved bedding-parallel fabric in the iron-formation, suggesting minimal alteration of the magnetic mineralogy since deposition and/or a mimetic secondary magnetic mineralogy. The iron-formation has not been internally deformed since the magnetic mineralogy was established. Analyses by variable-field translation balance and X-ray diffraction showed that the predominant magnetic mineral is hematite but a small amount of magnetite also is present in most samples. Following low-temperature pre-treatment as appropriate, stepwise thermal and alternating-field demagnetization of 218 specimens revealed a low-temperature, post-folding component (maximum T_ub≈400 °C, D=27.1°, I=20.1°, α₉₅=10.9°, from seven sites; pole position of 40.6°S, 257.0°E), and components carried by magnetite (maximum T_ub≈580 °C, D=35.8°, I=3.9°, α₉₅=9.1°, from 10 sites; pole position of 29.6°S, 250.9°E) and hematite (maximum T_ub≈680 °C, D=40.0°, I=1.6°, α₉₅=18.6°, from seven sites; pole position of 26.8°S, 247.0°E). The components carried by magnetite and hematite are pre-, syn- and post-folding depending on the sampling site, indicating that the magnetization was acquired continuously with deformation in the New Québec Orogen at 1.84–1.83 Ga. No evidence was found for acquisition of magnetization during the Mesozoic, when many of the iron oxide orebodies in the Schefferville–Knob Lake area are thought to have formed. Our findings imply that an episode of Fe-enrichment of iron-formation in the Sokoman Formation involved the circulation of hydrothermal fluids related to late Paleoproterozoic orogenesis. Such orogenic circulation of fluids may have contributed to the development of hematitic orebodies in the central New Québec Orogen.  相似文献   

Geological evaluation of Halfway–Doig–Montney hybrid gas shale–tight gas reservoir,northeastern British Columbia     

《Marine and Petroleum Geology》2013,39(1):53-72

Evaluation of the reservoir quality of the Triassic Halfway–Montney–Doig hybrid gas shale/tight gas reservoir in the Groundbirch field in northeastern British Colombia requires an integration of unconventional and conventional methodologies. Reservoir evaluation includes reservoir thickness and structure, total porosity, TOC content, organic maturity, pore size distribution (micro- to macro-pore size fractions), surface area, mineralogy and pulse-decay permeability. Quartz (10–74%), carbonate (13–73%) and feldspar (0–42%) dominate the mineralogy of all formations with illite (0–32%) being locally important. The T_max values range between 443 and 478 °C placing the reservoirs beyond the oil window. Pore size distribution by low-pressure gas adsorption analysis identifies a large variation between the contributions from the micro-, meso- and macro-pore size fractions. Matrix permeabilities range between 1.0E-3 and 6.5E-7 mD at an effective stress between 2400 and 3300 PSI (16.5–22.8 MPa).Changes in depositional environments and diagenetic processes manifest as differences in lithology and mineralogy within the Montney and Doig reservoirs which subsequently affect the fabric, texture and pore size distribution. Fabric, texture and pore size distribution contribute to the variation in the permeability and the proportions of free to sorbed gas within the reservoir. Quartz-rich, coarser-grained intervals (upper portions of Doig C, B and Halfway Formation) have lower surface area, greater porosities and a higher volume of macropores compared to the carbonate- and clay-rich finer-grained intervals (Doig A). Permeabilities do not vary according to lithology with higher permeabilities found within both fine-grained (Doig A) and coarser-grained (Halfway Formation) units. Permeability is controlled by pore size distribution. Higher permeability samples contain a balanced ratio between micro-, meso- and macro-porosity. The finer-grained intervals have higher sorbed gas capacity due to higher surface areas because of the higher volumes of finer mesopores and micropores than the coarser-grained units. However, porosity and permeability are low in some parts of the Doig A and fracture stimulation is necessary to achieve economic flow rates.  相似文献   

新疆北部青河县阿斯喀尔特铍矿区花岗质岩石年代学及地球化学特征   总被引：1，自引：1，他引：0  

张亚峰  蔺新望  赵玉梅  郭岐明  赵端昌  王星  朱伟鹏 《矿床地质》2017,36(3):643-658

新疆北部青河县阿斯喀尔特铍矿床的形成与岩浆活动密切相关,是中国花岗岩型铍矿床的典型代表。对矿区斑状二云母二长花岗岩进行LA-ICP-MS锆石U-Pb年龄测试,获得其加权平均年龄为(216.7±2.8)Ma(MSWD=0.48),表明该岩体形成时代为晚三叠世,据此限定阿斯喀尔特铍矿床成矿时代略晚于216 Ma,为晚三叠世—早侏罗世。岩石具有高硅(w(Si O2)=70.86%~76.34%)、富碱(ALK=5.54~9.30)、富铝(w(Al_2O_3)=13.00%~14.74%,A/CNK=0.99~1.23)、低钛(w(Ti O2)=0.02%~0.18%)和镁(w(Mg O)=0.02%~1.21%)特征,为过铝质中钾-高钾岩石系列。稀土元素配分型式显示LREE的相对弱富集,HREE较平坦以及Eu弱-中等的负异常(δEu=0.37~0.90),呈略右倾型。微量元素Ba、Sr、Hf、Ti等具负异常,Rb、Th、K、Nb、Ta、La、Ce、Nd、Sm等具正异常,Rb/Sr比值较高(9.34~26.81),显示出S型花岗岩特征。结合区域资料,认为阿斯喀尔特铍矿矿区印支期花岗岩形成于后造山构造阶段,可能是上地壳含砂泥质岩石部分熔融的产物。  相似文献   

塔里木南缘布雅花岗岩和暗色包体的锆石U-Pb年代学及地球化学特征     

胡雪原  郭瑞清  努尔喀纳提&#;马达依普  郭羽  邹明煜  吕彪  魏震 《岩矿测试》2017,36(5):538-550

塔里木西南缘铁克里克地区广泛发育早古生代中酸性侵入岩,本文对其中布雅岩体及其暗色包体进行系统的岩石学、年代学及岩石地球化学研究,确定了岩石成因及其构造属性。LA-MC-ICP-MS锆石U-Pb年代学研究表明,寄主石英二长闪长岩结晶年龄为432.6±2.5 Ma(MSWD=1.5),暗色包体结晶年龄为432.4±6.4 Ma(MSWD=0.031),二者形成时代相同,均为志留纪早期岩浆活动的产物。地球化学特征表明,布雅暗色包体应来源于地幔的部分熔融,而寄主岩石岩浆具有壳源岩浆的性质并经历了幔源岩浆不均匀的混合。野外及岩相学特征均显示暗色包体为铁镁质岩浆注入长英质岩浆快速冷凝形成的,是幔源岩浆底侵下地壳形成的岩浆混合作用的产物。它们是塔里木南缘早古生代碰撞造山作用晚期的岩浆记录。  相似文献   

新疆阿尔泰克兰盆地基底发现晚寒武世—早奥陶世地层——来自LA-MC-ICP-MS锆石U-Pb年龄证据   总被引：2，自引：0，他引：2  

杨富全  柴凤梅  李强  谷高灵  杨成栋 《地球学报》2017,38(6):859-871

前人认为新疆阿尔泰克兰盆地底部为中—上志留统库鲁木提群,岩性为片岩、片麻岩、变粒岩和变质砂岩组合,原岩为陆源碎屑岩和火山岩。本次获得克兰盆地底部和外围原"库鲁木提群"矽线石云母片岩、黑云母斜长角闪片岩和斜长角闪片岩LA-MC-ICP-MS锆石U-Pb年龄分别为(489.7±2.5)Ma、(480.6±1.3)Ma和(494.9±2.4)Ma,3件样品限定这套片岩年龄为481~495 Ma,属晚寒武世—早奥陶世地层。通过对比认为这套岩石组合不属于中—上志留统库鲁木提群、震旦纪—早寒武世喀纳斯群和中—上奥陶统哈巴群,很可能是一套新的岩石地层单位,这一发现对探讨阿尔泰地质背景和构造演化具有重要意义。  相似文献   

华南晚二叠世层序—古地理及聚煤规律^*          下载免费PDF全文

邵龙义  张超  闫志明  董大啸  高彩霞  李英娇  徐晓燕  梁万林  易同生  徐锡惠  黎光明  陈忠恕  程爱国 《古地理学报》2016,18(6):905-919

晚二叠世是地质历史中重要的成煤时期,在中国南方多个省区都形成了可采煤层。受海平面变化的影响,华南地区晚二叠世发育一套完整的陆相—海陆过渡相—海相含煤岩系。通过对野外露头及钻孔剖面资料分析,识别出了区域不整合面、下切谷底部冲刷面、河道间古土壤层和沉积相转换面等关键层序地层界面,以及依据海相石灰岩标志层横向分布规律反映的区域最大海泛面,同时结合前人关于华南地区地层对比及煤层对比方面的成果,将华南上二叠统划分为3个三级层序及9个体系域。利用单因素分析多因素综合作图法恢复了各层序中岩相古地理及煤层分布规律,结果表明:层序Ⅰ中煤层主要形成于潮控下三角洲平原以及潟湖潮坪环境,厚煤层的展布受这些沉积相带控制;层序Ⅱ中三角洲平原环境中煤层最厚,开阔台地煤层最薄,平面上煤层厚度表现为西部厚、中部次之、东部无煤的阶梯式递变;层序Ⅲ中煤层主要形成于三角洲平原环境,此时聚煤作用主要发生于华南西部的康滇古陆东侧,在华南中部及东部大部地区发育的浅海台地和深水盆地均不利于聚煤作用发生。  相似文献