西峰油田长8储层微观孔隙结构非均质性与渗流机理实验

为深入剖析超低渗储层微观孔隙结构非均质性对渗流机理的影响程度,选取鄂尔多斯盆地西峰油田长8储层有代表性的样品进行了真实砂岩微观模型水驱油和CT扫描水驱油驱替实验。通过真实砂岩微观模型水驱油实验发现,对于没有微裂缝存在的岩样,水驱油效果往往与渗透率成正比关系,而微裂缝的存在使得微观孔隙结构非均质性显得更加突出,渗流机理将完全改变,从而水驱油效果也表现出较大的差异。CT扫描水驱油驱替实验结果也表明,微裂缝的存在明显增加了孔喉微观非均质程度,使得水驱效果变差。而环压对具有双重孔隙介质储层的注水效果会产生较大影响。可见对于超低渗储层,微观孔隙结构非均质性是造成注入水波及效率不高、水驱油效果差的主要原因。     

Three-dimensional hydromechanical modeling of internal erosion in dike-on-foundation

Currently, numerical studies at the real scale of an entire engineering structure considering internal erosion are still rare. This paper presents a three-dimensional (3D) numerical simulation of the effects of internal erosion within a linear dike located on a foundation. A two-dimensional (2D) finite element code has been extended to 3D in order to analyze the impact of internal erosion under more realistic hydromechanical conditions. The saturated soil has been considered as a mixture of four interacting constituents: soil skeleton, erodible fines, fluidized fine particles, and fluid. The detachment and transport of the fine particles have been modeled with a mass exchange model between the solid and the fluid phases. An elastoplastic constitutive model for sand-silt mixtures has been developed to monitor the effect of the evolution of both the porosity and the fines content induced by internal erosion upon the behavior of the soil skeleton. An unsaturated flow condition has been implemented into this coupled hydromechanical model to describe more accurately the seepage within the dike and the foundation. A stabilized finite element method was used to eliminate spurious numerical oscillations in solving the convection-dominated transport of fluidized particles. This numerical tool was then applied to a specific dike-on-foundation case subjected to internal erosion induced by a leakage located at the bottom of the foundation. Different failure modes were observed and analyzed for different boundary conditions, including the significant influence of the leakage cavity size and the elevation of the water level at the upstream and downstream sides of the dike.     

古代植物的医药功能初探:以陕西高陵杨官寨遗址H85出土植物遗存为例

植物考古学界多以研究古代农业经济及其发展演变为主,鲜有对其他问题进行深入分析,本文通过对一个灰坑内出土植物遗存的组合特点和量化特点分析,探讨了古代植物的医药功能。由陕西省考古研究院和中美国际田野考古学校联合发掘的西安市高陵区杨官寨遗址H85是庙底沟文化中晚期灰坑,H85坑底的生土台结构和烧烤草拌泥处理壁面的现象显示其早期功能可能与居住有关。前人仅对H85 B12层以上出土植物遗存进行过研究,研究显示第⑧~B12层与居住生活关系密切。此次采集的浮选土样合并相同单位后共计21份,不仅包括第①~B12层样品,还包括最底层的第B14层样品（采样缺少B13层）。此次浮选发现了包括粟（Setaria italica）、黍（Panicum miliaceum）、大豆（Glycine max）、狗尾草（Setaria viridis）、马唐（Digitaria sanguinalis）、草木樨属（Melilotus sp.）、胡枝子属（Lespedeza sp.）、猪毛菜（Salsola collina）、夏至草（Lagopsis supina）、秃疮花（Dicranostigma leptopodum）、泥胡菜（Hemistepta lyrata）,以及植物鳞茎（bulk）等20余个种属的植物遗存。H85最底层比较集中地发现了禾本科（Gramineae）杂草、猪毛菜、植物鳞茎、夏至草、秃疮花和泥胡菜等植物。其中,夏至草、秃疮花、泥湖菜的药用价值需要被重视,可能与调节妇女生理机能密切相关,禾本科杂草暗示了铺垫坑底行为的存在,据此推断H85不仅作为房子被使用过,并且其功能可能还具有一定特殊性,这是初次对史前人类的原始医疗情况进行探讨,从医药考古的角度看具有重要意义。量化统计分析还显示,粟、黍是重要的日常口粮,大豆应被利用,胡枝子属、草木樨属这样的小型豆科植物可能与牲畜饲料关系密切。综上,H85出土植物遗存不仅反映了遗迹功能,某种程度上还原了杨官寨先民在饮食、家畜饲养和原始医疗等方面的生活场景。

     

Driving forces of indirect carbon emissions from household consumption in China: an input–output decomposition analysis

Human activities have become a major source of Earth’s climate change, which brings the rise of surface air temperature and subsurface ocean temperature. Therefore, promoting sustainable consumption and production patterns is imperative to minimize the use of natural resources and reduce emissions of pollutants. This study uses Economic Input–Output Life-Cycle Assessment method and structural decomposition model to identify the driving forces that influence the changes in carbon emissions from China’s residential consumption in the context of sustainable consumption. The findings of the study are as follows: (1) indirect carbon emissions from Chinese household consumption increase rapidly over time; (2) the largest carbon dioxide emitting sector turns from agriculture sector in 1992 into service sector in 2007; (3) the consumption level and the emission intensity are the main drivers that influence the change in indirect carbon emissions; and (4) the factor of consumption level presents positive effect on the emissions, while the emission intensity effect plays a negative role. Besides, the factors of urbanization, production structure, population size and consumption structure also promote the rapid increase in carbon emissions.

     

东昆仑白石崖地区铁多金属矿田找矿新发现及其意义

白石崖铁多金属矿田位于东昆仑东段,距青海省都兰县城西20多公里,矿田内的矿床大多赋存于下石炭统大干沟组碳酸盐岩与中酸性火山岩或酸性侵入体接触带矽卡岩带中。白石崖地区成矿特征显示,本区具有寻找铁铜铅锌钨锡的地质条件。以M20矿床为突破口,采用磁法、EH4连续电导率剖面测量及钻探查证等技术,开展了以铁多金属为主的找矿工作,发现并探明了一批有一定储量的多金属矿体,并于深部岩体附近发现钨矿体,实现了近年来白石崖地区找矿的重大突破。     

A Multi-method Approach for Estimating the Failure Depth of Coal Seam Floor in a Longwall Coal Mine in China

Determining the failure depth of coal seam floor is necessary for safe mining operations, especially when the coal seam is located above confined aquifers with high water pressure. Geomechanical, geophysical, and hydrogeological data collected during the longwall mining of the first working face of coal seam no. 16 in the Nantun coal mine, Shandong Province, China, were used to calculate the failure depth of the coal seam floor above the Ordovician limestone confined aquifer. The multiple method approach employed by this study made use of the plastic sliding theory, empirical formulas, water injection test, and numerical simulation. Multiple methods can compensate for and validate each other and also overcome the intrinsic limitations of any single method. The results showed that the most appropriate value of the failure depth of the coal seam floor in the mine was 14.6 m and this value proved useful for knowing the effective thickness of water pressure-resistant layer below the coal seam. The failure depth also proved to be an important parameter when preventing groundwater flow into the mine from the coal seam floor.     

Extraction and Analysis of Land Cover Heterogeneity over China

Spatial heterogeneity exists in land surface at every scale, and it is one of key factors to bring uncertainty to land parameter retrieval from remote-sensed data. This paper proposed a methodology to use the boundary length among different land cover types to characterize and quantify land surface heterogeneity based on high-resolution land cover images. Then the heterogeneity feature at 1 kilometer scale in China was extracted from “GlobalLand30” land cover datasets with the spatial resolution of 30 m. The mixed structure, degree of fragmentation and intra-heterogeneity of eight main vegetation biomes from MODIS land cover product over heterogeneous surface in china were analyzed. Mountain area and ecotone are more heterogeneous than other regions. Savanna biome (average boundary length is 7 426 meters) is the most heterogeneous zone followed by forest, grass/crop and shrub biome with average boundary length of 4 323, 3 160, 1 779 meters, respectively.     

Thaw-induced slope failures and susceptibility mapping in permafrost regions of the Qinghai–Tibet Engineering Corridor,China

With recent climatic warming and enhanced human activities, slope failures related to permafrost degradation are widespread along the Qinghai–Tibet Engineering Corridor. Assessment and mapping of the slope failures are necessary to mitigate hazards and plan engineering activities. According to our field investigations, the occurrence of slope failures is mainly controlled by the slope gradient, ground-ice content, permafrost temperatures, surficial deposits, and slope aspect. Modeling conducted in ArcGIS? was used to produce a slope failure susceptibility map for a representative region along the Qinghai–Tibet Railway from Wudaoliang to Fenghuo Mountain Pass. The study region was divided into four classes based on slope failure susceptibility: (1) unlikely, (2) low, (3) moderate, and (4) high. Areas classified as unlikely accounted for 10.76 % of the study region, while low susceptibility areas comprised 44.51 %. The moderate and high susceptibility zones comprised 21.79 and 22.94 %, respectively. The actual distribution of slope failures in the region was consistent with the modeled results, which demonstrates the utility of the assessment method for future hazard management and engineering planning.     

Modeling beach profile changes by typhoon impacts at Xiamen coast

For the Xiamen coast where typhoon frequently occurs, beaches are subject to severe erosion during typhoons. To investigate storm-induced beach profile changes at Xiamen coast, four inner XBeach models were applied using typhoon Dan as a case study. These numerical simulations utilized hydrodynamic and wave conditions determined from larger-scale outer and middle coupled Delft3D-FLOW and SWAN models. The models were validated against historic measurements of tidal level, storm tide, storm surge and beach profiles, thus showing the accuracy of outer and middle models to provide boundary conditions and the reliability of inner models to reflect beach profile changes during a typhoon process. The applicability of this modeling approach to Xiamen coast was verified. The results also demonstrated that an enormous amount of dune face erosion occurred at the selected beaches during the typhoon Dan process and the slopes in the vicinity of zero elevation for the chosen four beach profiles all turned out to be gentler after typhoon Dan. Nevertheless, these beaches suffered different impact degrees and processes during the typhoon influence period. Compared to swash and collision regimes, overwash and inundation regimes have the ability to alter beach profile rapidly in short time. Post-storm beach profile with and without vegetation indicated that vegetation is capable of protecting coastal beaches to some extent. By running the nested models, the simulated results can be employed in the management of the beach system and the design of beach nourishment projects at Xiamen coast.

     

Physical model study on the clay–sand interface without and with geotextile separator

In most marine reclamation projects, sand fill is placed directly on soft marine seabed soils. The sand particles can easily penetrate into the soft marine soils, and the soft soil can also move into the pore spaces inside the sand at the initial contact interface between the sand and the soft marine soil. In this case, the permeability and the volume of the sand above the initial surface are reduced. To avoid this problem, a geotextile separator is often placed on the surface of the soft marine soils before placing the sand. In this study, a two-dimensional physical model is utilized to study the geotextile separator effects. The initial conditions of a clayey soil, sand fill, and surcharge loading were kept the same in the physical model test with the only difference being that a geotextile separator was either placed on the clay surface or omitted. The settlements of the initial interface were recorded and compared for the two cases without or with the geotextile separator. The particle size distribution of the soils taken across the interface zone for different time durations was then measured, analyzed, and compared. Based on an analysis of the results, the sand percolation depth was 40 mm and fine particle suffusion was apparent when the sand was placed directly on the marine slurry surface without a geotextile separator. However, when a geotextile separator was used sand percolation was avoided, and the fine particle suffusion was effectively diminished. A relative fine particle fraction is defined to illustrate the migration of fine particles from the clay to the sand soils. The fine particle percentages of the Hong Kong Marine Deposits–sand mixtures were calculated for the cases with and without a geotextile separator using an empirical formula and micromechanical modeling to obtain a better understanding of the effects of geotextile separators in practice.