Proppant Crushing Mechanisms Under Reservoir Conditions: Insights into Long-Term Integrity of Unconventional Energy Production

Proppant crushing, a major proppant failure mechanism, occurs in geothermal energy and oil/gas stimulation production stages when the level of net stress exerted on the proppant exceeds the actual crush resistance of the material. Loss of effective reservoir conductivity due to proppant crushing can result in significant loss in productivity, and so it is crucial to understand the realistic proppant mechanical performances under deep reservoir conditions. This review provides a comprehensive overview of proppant crushing at the micro- to macro-levels by analyzing single proppant breakage, as well as re-arrangement and breakage mechanisms of proppant packs under in situ fracture environments. The choice of an appropriate proppant type based on the fracture treatment plays a key role in effective geothermal and oil/gas recovery. In addition, injection of proppants with better characteristics (higher sphericity, lower size, better gradation and lower granular porosity) can significantly influence the reduction of the extent of proppant crushing. Moreover, this study compares the performances and responses of different types of proppants upon proppant interaction with geothermal and oil/gas reservoir environments. Furthermore, this paper discusses various proppant types and their enhanced characteristics, which can be utilized as controlling measures for proppant crushing during unconventional energy extraction.

     

中国西部兰白西城市群经济增长结构分解及空间特征

采用偏离-份额四分量模型,分解2010-2015年兰白西城市群41个县（区）经济增长结构;采用空间数据分析方法,分析41个县（区）经济增长总量及各分量空间特征。结果表明：（1）兰白西城市群呈现以兰州市和西宁市为双核心的"中心-外围"经济结构,兰州市的经济中心地位更为显著。（2）根据经济增长总量及各分量,将兰白西城市群41个县（区）分为经济快速增长型、经济滞后增长型、竞争力优势推动型和资源配置优势推动型等4种类型。（3）经济增长总量、份额偏离分量、产业结构分量在空间上存在集聚性特征,竞争力分量在空间上存在随机分布性特征,资源配置分量在空间上存在负相关性特征。（4）份额偏离分量、产业结构分量与经济增长总量的空间重合度较高,竞争力分量、资源配置分量与经济增长总量的空间重合度有待优化。     

河南省能源消费碳排放动态变化及空间分异

在分析河南省1978—2015年能源消费碳排放总量和结构变化的基础上,利用Im PACT等式对河南省碳排放驱动因素进行了研究和对未来碳排放量进行了情景预测,并运用空间自相关分析法探讨了空间分异特征。结果表明:(1)1978—2015年,河南省碳排放量总体上呈现增加的趋势,年均增长5.11%,由煤炭和石油消费导致的碳排放比重一直稳定在95%以上。(2)弹性分析表明人均真实GDP增加1%将导致人均能源消费量增加0.48%,利用强度下降0.52%,而环境影响增加0.53%。(3)保持经济增长的同时,与2011—2015年相比,1978—2015年效率年均增长率提高5.25倍,是河南省实现循环经济建设的一种可行方案。(4)河南省2015年碳排放全局Moran’s I值为0.047,呈微弱空间正相关,各地市碳排放具有明显的二元结构特征,空间集聚特征不明显。     

Spatial and temporal variation of vegetation phenology and its response to climate changes in Qaidam Basin from 2000 to 2015

Based on TIMESAT 3.2 platform, MODIS NDVI data (2000–2015) of Qaidam Basin are fitted, and three main phenological parameters are extracted with the method of dynamic threshold, including the start of growth season (SGS), the end of growth season (EGS) and the length of growth season (LGS). The spatial and temporal variation of vegetation phenology and its response to climate changes are analyzed respectively. The conclusions are as follows: (1) SGS is mainly delayed as a whole. Areas delayed are more than the advanced in EGS, and EGS is a little delayed as a whole. LGS is generally shortened. (2) With the altitude rising, SGS is delayed, EGS is advanced, and LGS is shortened and phenophase appears a big variation below 3000 m and above 5000 m. (3) From 2000 to 2015, the temperature appears a slight increase along with a big fluctuation, and the precipitation increases evidently. (4) Response of phenophase to precipitation is not obvious in the low elevation humid regions, where SGS arrives early and EGS delays; while, in the upper part of the mountain regions, SGS delays and EGS advances with temperature rising, SGS arrives early and EGS delays with precipitation increasing.     

The price for subway access: spatial econometric modelling of office rental rates in London

ABSTRACT

The relative location of commercial properties as the distance to the metro station as well as its absolute location as the address in the Central Business District (CBD) is expected to influence its valuation. We apply the advanced spatial econometric methodology, based on micro geo-located data, to the office rental transaction data from London in 2015. We use different spatial information on the local and global neighbourhood in order to estimate the spatial hedonic valuation model and test the strength of spatial spillovers and location effects on office fees. For offices in London in 2015, geographical factors may raise the price by 50%, as every next 100 m to the metro cost an additional 0.7 ? per ft² per year and the CBD location raises the cost for ca. 20 ? per ft² per year.     

Positive plant interactions in the Iberian Southeast: Mechanisms, environmental gradients, and ecosystem function

Semi-arid ecosystems are privileged sites to address the effects of plant interactions on community structure and dynamics because environmental conditions are demanding and may change quickly, altering in significant ways the balance between positive and negative effects among neighboring plants. Plant interaction processes have been well documented in the semi-arid region of Southeast Spain over the last 15 years. In this article we review the growing body of research on plant–plant interactions available from this area, highlighting its importance in increasing our knowledge on this field of study. This review has been organized in five sections, i) facilitation mechanisms; ii) the nurse effect; iii) the balance of interactions and environmental, ontogenic, temporal, and spatial gradients; iv) the effects of facilitation on biodiversity; and, v) facilitation and ecosystem functioning. Mechanisms of facilitation in these systems are relatively well known, but not completely explored. In these environments competition, mainly for water, is intense between neighbors and switches in intensity from belowground to aboveground as productivity increases. By contrast, facilitation may decrease quickly with increasing productivity, although the balance between facilitation and competition is not fully understood, and is further complicated because shifts can also be driven by factors such as life history or physiology of interacting species. Positive interactions are critical for maintaining biodiversity in some ecosystems in SE Spain, but their role as a driver of ecosystem functioning is less clear. Research on plant–plant interactions in this region has been highly influential and has contributed to our overall understanding of plant community dynamics. Despite the important progress achieved during the last 15 years, there is still substantial scope for exploring the effects of plant interactions at the ecosystem level, and their role as modulators of disturbances such as the current global environmental change.     

黄淮海平原气候变化及其对耕地生产潜力的影响

利用1991年和2000年黄淮海平原气象台站的历史观测资料,分析该地区气温、降水的变化趋势,并利用农业生态地带(AEZ)模型估算黄淮海平原各农业生态区的耕地生产潜力。通过分析气温、降水与耕地生产潜力的关系,评价气候变化对耕地生产潜力的影响。研究发现,黄淮海平原耕地生产潜力与降水量、气温呈显著正相关。对各农业生态区的回归分析表明,如果气温或降水量提高10%,耕地生产潜力将分别提高3.2%与0.3%。该研究对制订应对气候变化、保护耕地与提高耕地生产潜力方面的决策具有参考价值。     

新疆草地气候生产潜力变化特征及对气候响应的预测研究

基于新疆地区52个气象站点1959-2008年逐月气温、降水资料,利用Miami模型和Thornthwaite Memorial模型、线性趋势线、ArcGIS反距离权重插值等方法,对新疆草地生产潜力的时空变化特征进行分析。结果表明,近50 a来,新疆草地温度、降水、蒸散生产潜力均表现为显著增加,且四季和生长季各生产潜力也呈线性增加,夏季和生长季增幅最大,其次,草地生产潜力以及增幅均表现为北疆高于南疆,基本为由南向北递增,并和多年平均降水量变化一致。其中,水分条件是影响新疆草地生产潜力的主导因素。根据二元一次线性回归方程计算得出,年平均气温每升高/降低1 ℃,草地的年气候生产力增加/减少17.309 kg·hm-2·a-1,年降水量每增加/减少1 mm,草地的年气候生产力增加/减少24.392 kg·hm-2·a-1。     

吉林省县域经济效率时空格局演化研究

基于吉林省39个县域11 a的面板数据,采用DEA-Malmquist指数法测度县域的全要素生产率,并运用探索性空间数据分析手段（ESDA）,对不同时间维度的县域经济发展效率进行空间关联性与空间差异度分析。研究发现:①在考察期内,吉林省县域全要素生产率总体呈现波动上升,县域间的差异性表现出先扩大、后缩小的趋势。全要素生产率与县域经济总量之间不存在显著的正相关关系;②在全要素生产率改善方面,技术进步发挥了主导性作用,但近年来其对全要素生产率的贡献度逐年下降。而技术效率和规模效率对吉林省县域全要素生产率的促进作用在逐年增强; ③就全省范围而言,县域全要素生产率总体上不存在显著的全局空间自相关性,基本呈现随机分布的空间格局。但在局部空间尺度上,具有一定程度的空间集聚性,并且以高-高和高-低分布形式为主;④县域间经济效率的时空分异主要受其资源禀赋,以及在此基础上形成的县域经济分工、产业结构和经济集聚水平等的影响。     

东中部地区城市人口、经济与城市建设用地的非均衡与协调性分析

基于2000、2015年中国东中部地区261个地级市统计与土地利用数据,运用空间自相关模型,变异系数和三元协调度模型分析其城市人口、GDP和城市建设用地的空间集聚态势和非均衡变化过程,揭示人口城市化与土地城市化的协调程度。结果显示：（1）城市人口、GDP和建设用地的Moran’s I指数均为正值且2015年的值大于2000年的值,显示出明显的空间集聚特征,且在2000—2015年集聚特征不断加强;（2）城市人口密度和人均GDP的变异系数分别从2000年的1.38和0.91下降到2015年的0.96和0.70,地均GDP从1.32上升到1.77,表明城市人口密度和地均GDP的差异在逐步减小,但地均GDP的不均衡性却在增大;（3）2015年,共有171个地级市城市用地规模增长弹性系数小于1.12且人均城市用地小于115m²,但有104个地级市地均GDP在1000元/m²以下,表明虽然绝大部分地级市城市化规模和速率都在可控范围之内,城市用地经济产出仍然相对较低;（4）90%以上地级市的城市人口、GDP和城市建设用地三者在两个研究时间段内处于协调发展状态。     

东北振兴以来吉林省区域经济差异的时空演变研究

基于吉林省2003~2015年间地区生产总值和人均地区生产总值数据,以市域、县域两个尺度单元为研究对象,采用人口加权变异系数、基尼系数、泰尔指数等统计分析方法,对吉林省东北振兴战略实施以来的13 a内,区域经济差异的时空演变进行定量分析,并运用泰尔指数的分解方法,探讨了吉林省区域经济差异的空间格局。结果发现：① 吉林省区域经济总体差异、市域差异、县域差异均呈逐年下降趋势。② 通过差异贡献率显示：县域差异是区域总体差异变化的主导力量,长春市域的内部差异远高于其他市域,但有逐年减小的趋势,长吉两地的二元结构仍然突出,是全省区域经济差异产生的主要来源,主导着全省区域经济差异走向;③ 从2003~2015年来看,全省经济增长速度较快的地区主要还是集中在“三核一带”;④吉林省经济差异主要是由资源禀赋、产业结构、极化效应和政策导向等多种因素综合作用的结果。     

中国航空运输的时空格局演变与发展预测（英文）

This paper analyses the features and dynamic changes of the spatial layout of air transportation utilization among different provinces in China. It makes use of data for the airport throughput and socio-economic development of every province throughout the country in the years 2006 and 2015, and employs airport passenger and cargo throughput per capita and per unit of GDP as measures of regional air transportation utilization, which is significant for refining indicators of regional air transportation scale and comparing against them. It also analyzes the spatial differences of coupling between the regional air transportation utilization indicators and the key influencing factors on regional air transportation demand and utilization, which include per capita GDP, urbanization rate, and population density. Based on these key influencing factors, it establishes a multiple linear regression model to conduct forecasting of each province's future airport passenger and cargo throughput as well as throughput growth rates. The findings of the study are as follows:(1) Between 2006 and 2015, every province throughout the country showed a trend of year on year growth in their airport passenger and cargo throughput per capita. Throughput per capita grew fastest in Hebei, with a rise of 780%, and slowest in Beijing, with a rise of 38%. Throughput per capita was relatively high in western and southeastern coastal regions, and relatively low in northern and central regions. Airport passenger and cargo throughput per unit of GDP showed growth in provinces with relatively slow economic development, and showed negative growth in provinces with relatively rapid economic development. Throughput per unit of GDP grew fastest in Hebei, rising 265% between 2006 and 2015, and Hunan had the fastest negative growth, with a fall of 44% in the same period. Southwestern regions had relatively high throughput per unit of GDP, while in central, northern, and northeastern regions it was relatively low.(2) Strong correlation exists between airport passenger and cargo throughput per capita and per capita GDP, urbanization rate, and population density. Throughput per capita has positive correlation with per capita GDP and urbanization rate in all regions, and positive correlation with population density in most regions. Meanwhile, there is weak correlation between airport passenger and cargo throughput per unit of GDP and per capita GDP, urbanization rate, and population density, with positive correlation in some regions and negative correlation in others.(3) Between 2015 and 2025, it is estimated that all provinces experience a trend of rapid growth in their airport passenger and cargo throughput. Inner Mongolia and Hebei will see the fastest growth, rising221% and 155%, respectively, while Yunnan, Sichuan, and Hubei will see the slowest growth, with increases of 62%, 63%, and 65%, respectively.     

2002-2015年中国社会保障水平时空分异及驱动机制

运用主成分分析法对2002-2015年的中国社会保障水平进行测算,分析其时空分异特征,同时运用地理加权回归模型分析其影响因素及驱动机制。研究表明：① 中国社会保障总体、地区水平在逐年提高,但区域相对保障水平差距有扩大趋势。② 中国社会保障水平发展不均衡,社会保障水平的“东—中—西”的格局与中国地区发展的格局相吻合。社会保障水平的热点区和冷点区表现出较明显的空间演变特征,高热点区在东部地区扩散并向中部地区辐射,冷点区在西部地区分布并不断加深和强化。③ 人均GDP、农村人均纯收入、城镇化率、教育水平、财政转移支付5个因素,形成经济、教育、财政和社会四大驱动力引致社会保障水平的时序变化和空间布局。     

收缩城市建设用地利用效率时空分异及影响机制——以黑龙江省伊春市为例

建设用地是城镇经济社会活动的空间载体,其利用效率是调控建设用地扩张和配置的重要基础.论文以收缩型城市——黑龙江省伊春市为例,利用DEA模型测算了1995-2015年伊春市建设用地利用效率分析其时空演变规律,并运用地理探测器模型探究伊春市建设用地利用效率空间分异的影响机制,结论如下:①1995-2015年伊春市建设用地利...     

Air transportation in China: Temporal and spatial evolution and development forecasts

This paper analyses the features and dynamic changes of the spatial layout of air transportation utilization among different provinces in China. It makes use of data for the airport throughput and socio-economic development of every province throughout the country in the years 2006 and 2015, and employs airport passenger and cargo throughput per capita and per unit of GDP as measures of regional air transportation utilization, which is significant for refining indicators of regional air transportation scale and comparing against them. It also analyzes the spatial differences of coupling between the regional air transportation utilization indicators and the key influencing factors on regional air transportation demand and utilization, which include per capita GDP, urbanization rate, and population density. Based on these key influencing factors, it establishes a multiple linear regression model to conduct forecasting of each province’s future airport passenger and cargo throughput as well as throughput growth rates. The findings of the study are as follows: (1) Between 2006 and 2015, every province throughout the country showed a trend of year on year growth in their airport passenger and cargo throughput per capita. Throughput per capita grew fastest in Hebei, with a rise of 780%, and slowest in Beijing, with a rise of 38%. Throughput per capita was relatively high in western and southeastern coastal regions, and relatively low in northern and central regions. Airport passenger and cargo throughput per unit of GDP showed growth in provinces with relatively slow economic development, and showed negative growth in provinces with relatively rapid economic development. Throughput per unit of GDP grew fastest in Hebei, rising 265% between 2006 and 2015, and Hunan had the fastest negative growth, with a fall of 44% in the same period. Southwestern regions had relatively high throughput per unit of GDP, while in central, northern, and northeastern regions it was relatively low. (2) Strong correlation exists between airport passenger and cargo throughput per capita and per capita GDP, urbanization rate, and population density. Throughput per capita has positive correlation with per capita GDP and urbanization rate in all regions, and positive correlation with population density in most regions. Meanwhile, there is weak correlation between airport passenger and cargo throughput per unit of GDP and per capita GDP, urbanization rate, and population density, with positive correlation in some regions and negative correlation in others. (3) Between 2015 and 2025, it is estimated that all provinces experience a trend of rapid growth in their airport passenger and cargo throughput. Inner Mongolia and Hebei will see the fastest growth, rising 221% and 155%, respectively, while Yunnan, Sichuan, and Hubei will see the slowest growth, with increases of 62%, 63%, and 65%, respectively.     

浑善达克沙地景观结构变化对生态系统服务的影响

京津风沙源治理是中国政府实施的具有重大战略意义的生态工程,实施近20年,区域生态环境状况发生了根本转变。为了定量评估京津风沙源治理工程实施以来景观结构变化及其对生态系统服务价值的影响,以浑善达克沙地为研究区域,以生态调节服务（风蚀防治、水蚀防治、碳固存）、生态供给服务（牲畜养殖、粮食生产）、生境支持服务（自然生境多样性、人口居住支持服务）等指标,利用生态系统服务复合指数（Multiple ecosystem services landscape index,MESLI）和景观格局指数,运用冗余分析（redundancy analysis,RDA）和变差分解（Variation Partitioning）方法,研究了生态系统服务及集成的时空格局,以及植被景观组成与景观配置对区域生态系统服务贡献的变化。结果表明：（1）2000—2015年,浑善达克沙地的林地、草地面积减少,沙地面积则增加了110%;林地的景观结构改善,而草地与沙地的景观破碎化明显,连通度降低。（2）研究区东部和南部的生态系统服务价值增加了19%—85%,主要与林地景观的空间配置结构改善有关;中部和西部生态系统服务总体降低了...     

都市区空间结构与经济发展的互动关系研究

文章采用结构方程模型实证检验空间结构与经济发展的互动关系。研究发现,中国都市区已经进入多中心分散阶段,空间结构与经济发展存在因果关系,即经济发展水平的提高会扩大人口规模,规模增加则导致集聚不经济上升,并促进空间结构多中心化。多中心化后的空间结构由于降低了集聚不经济而进一步提高生产率。因而,传统地理学中关于两者互动发展的描述得到实证支持;同时明确了多中心化的直接动力是人口规模的增加,而不是经济发展水平的提高。这些发现对于优化当前中国的城市与区域空间战略具有重要的启示。     

TEMPORAL TRENDS IN SOIL PRODUCTIVITY EVALUATIONS*

Studies of soil productivity must compensate for the effects of temporal trends in order to examine the pattern of crop yields along spatial gradients. An analysis of the published yield estimates for 30 soils in 233 counties, however, did not find consistent yield increases over the past three decades. On the contrary, the yield estimates for many soils were markedly uniform since 1972. The uniformity appears to have two causes: the acknowledged difficulty of making yield estimates in a time of increasing variability in soil and crop management, both within and between regions, and surveyors' awareness of data stored in a national soils data base. The effect is to cast doubt on soil productivity data reported in county soil surveys published between 1973 and 1988.     

中国东北地区植被生产力控制因素分析

植被生长季长度和生长强度是形态上影响植被生产力变化的重要因子。全球变暖情景下,北半球中高纬度大部分地区植被生长季显著延长并对植被生产力产生正向反馈,而植被生长强度变化情形及对生产力的控制作用并不清晰。中国东北地区属于中纬度温带地区,具有较高的植被覆盖度和丰富的植被类型,探索其植被生长季长度和强度的变化及对生产力的控制作用有利于理解和应对该地区的生态系统变化。以中国东北为研究区,基于1982—2015年长时序遥感植被指数数据（NDVI3g）,利用曲率求导法确定植被生长季开始点（SOS）、结束点（EOS）、生长季长度（LOS）和夏季最大生长季强度（GM）等关键物候参数,然后利用相对重要性（RI）方法定量分析了生长季长度和强度对植被生产力长期变化趋势的相对贡献及时空格局。结果表明：① 研究区整体的植被生产力和生长强度呈现增强趋势,而生长季长度呈现缩短趋势,导致生长强度成为控制生产力变化趋势的主要因素（RI = 70%）;② 在不同植被覆盖区域,生长季长度和生长强度对生产力的影响程度具有显著的空间差异。西部草原区植被生产力受生长强度控制最为显著（RI = 93%）,其次为针叶林（RI = 66%）和阔叶林区（RI = 62%）,农作物区生产力受生长强度影响最小（RI = 56%）。生长季长度对植被生产力的控制在农作物区最为显著（RI = 40%）,在其他区域的影响约为27%~35%。各植被覆盖区生长强度与生产力均为正相关,生长季长度与生产力均为负相关;③ 气候因素（降水、温度）和物候变化均对主要贡献因子生长强度产生影响,其中SOS的变化对生长强度的影响程度和空间范围最为显著,主要表现为SOS推迟促进生长强度增强。本研究基于遥感数据发现1982—2015年间中国东北地区植被生长更加旺盛,但是植被生长活动主要受生长强度的影响,该研究可以为植被生产力变化模拟的参数选择提供新的线索。     

Life in the Goldilocks Zone: Perceptions of Place Disruption on the Periphery of the Bakken Shale

Community impacts from oil development in the Bakken Shale, located in the north central region of the United States, have been well reported in the press, including highly publicized accounts of social disruption. Less examined are communities on the periphery of such development, which experience related impacts unique to their location. Twenty-eight long-time residents from three Bakken periphery communities were interviewed to evaluate social and environmental impact perceptions, including perceived risks of place disruption. Findings suggest that whereas place meanings and identities were disrupted by the oil boom in Bakken core communities, they remain intact in these periphery communities. Findings further suggest periphery residents view their proximal location to the Bakken region as a social and economic “Goldilocks Zone:” close enough to benefit from spillover economic impacts, yet far enough away to avoid serious negative social impacts. This research extends understanding of place disruption and development impacts in energy periphery communities.