Mapping the hydraulic connection between a coalbed and adjacent aquifer: example of the coal-seam gas resource area,north Galilee Basin,Australia

Coal-seam gas production requires groundwater extraction from coal-bearing formations to reduce the hydraulic pressure and improve gas recovery. In layered sedimentary basins, the coalbeds are often separated from freshwater aquifers by low-permeability aquitards. However, hydraulic connection between the coalbed and aquifers is possible due to the heterogeneity in the aquitard such as the existence of conductive faults or sandy channel deposits. For coal-seam gas extraction operations, it is desirable to identify areas in a basin where the probability of hydraulic connection between the coalbed and aquifers is low in order to avoid unnecessary loss of groundwater from aquifers and gas production problems. A connection indicator, the groundwater age indictor (GAI), is proposed, to quantify the degree of hydraulic connection. The spatial distribution of GAI can indicate the optimum positions for gas/water extraction in the coalbed. Depressurizing the coalbed at locations with a low GAI would result in little or no interaction with the aquifer when compared to the other positions. The concept of GAI is validated on synthetic cases and is then applied to the north Galilee Basin, Australia, to assess the degree of hydraulic connection between the Aramac Coal Measure and the water-bearing formations in the Great Artesian Basin, which are separated by an aquitard, the Betts Creek Beds. It is found that the GAI is higher in the western part of the basin, indicating a higher risk to depressurization of the coalbed in this region due to the strong hydraulic connection between the coalbed and the overlying aquifer.     

全球温度变化的热力学平衡和最新发现

本文提出了一种新的研究全球气候温度变化的思路。为发现全球气候变化的宏观规律,把生物圈系统作为一个整体的物质进行研究,从而把纷繁复杂的全球气候温度变化问题归纳成经典物理学的热量与温度变化问题。给出了广义生物圈的热平衡测量Q值和温度变化的热力学公式,并在实际数据的基础上通过计算发现人类使用矿物燃料和核能所排放的热量理论上可使全球海平面每年升高35 mm或者可使大气对流层温度每年升高011 ℃。该发现表明:能源热量因素已成为影响全球温度变化的重要因素。     

煤层气损失气量计算的全脱分析法

针对目前煤层气损失气量无法计算煤层的溶解气和游离气含量问题,根据烃类气体进入钻井液的方式和分布状态理论,基于气测录井资料,提出了计算煤层气损失气量的新方法——全脱分析法。通过沁水盆地枣园区块3号煤层的实际应用,发现该方法计算的损失气量明显高于常规煤心样品的回归结果,前者一般为后者的1.5~4.5倍。该方法不仅能有效地解决煤层气损失气量计算中忽视的溶解气和游离气问题,而且还能消除损失时间的影响,同时也可以按不同部位计算煤层气损失气量。该方法适用于不同煤级、各种结构的煤岩,数据易采集,计算过程简单,有很好的应用前景。     

Hydrogeochemical effects of secondary forest in Guangxi Nongla karst areas in China

Rainfall, throughfall, stemflow and spring were studied in a secondary forest during a wet season from April to August in 2006. Some of the chemicals in throughfall, stemflow and spring were increased in contrast with incident rainfall. Specifically, Cl⁻, HCO₃ ⁻, Na⁺ and Ca²⁺ were leached negatively in throughfall, but K⁺ and Mg²⁺ were leached positively. In stemflow, Cl⁻ and Na⁺ were leached negatively, the others were leached positively and their concentrations were higher than those in throughfall. Total carbon, organic carbon and inorganic carbon in throughfall and stemflow were increased as rainfall went through the secondary forest. The concentration of free CO₂ in rainfall was lower than both, throughfall and stemflow; the relationship between total acidity and free CO₂ was linear. pH of throughfall and stemflow , such as maximum, minimum and mean, were lower than that of rainfall and the extent of pH in spring was changed minimally. We came to a conclusion that rainfall via the secondary forest can lead to further erosion, accelerate the biogeochemical cycle in epikarst zone, enhance the effective state of alkali elements in the soil, supply vegetation with more nutrients and advance vegetation’s growth and succession, which are reasonably sufficient to form a stable karst ecosystem.     

微波消解等离子体发射光谱和石墨炉原子吸收光谱法联合测定土壤中多元素

采用密闭式微波消解系统处理土壤样品,电感耦合等离子体发射光谱法或石墨炉原子吸收光谱法测定土壤样品中铜、砷、铅、锌、钴、铬、锰、镍、钒9个元素。分别从消解液的选择、用酸量及样品消解量等方面进行消解条件的优化,确定了一个最适合土壤消解的前处理体系。各元素的检出限为0.16～2.52μg/g,回收率为95.2%～106.6%,精密度为2.03%～9.79%(n=7)。方法简单快速,效率高,劳动强度低,是进行土壤中多元素测定的高效方法。     

上新世中期中国气候的数值模拟分析

使用中国科学院大气物理研究所的全球大气环流模式,曾就上新世中期(距今约3百万年前)气候进行过数值模拟试验,在已有针对全球气候进行分析的工作基础上,集中研究了该地质时期我国气候的变化特征。数值试验结果表明,除了青藏高原地区由于地形海拔高度变化而引起的局地冷却现象以外,上新世中期我国约100°E以东地区地表气温上升4～8℃,升温中心位于江淮流域下游地区; 该经度线以西地区地表气温升幅相对要弱一些,在1～4℃之间。上新世中期年均降水在我国东部地区显著减少,平均减幅在0.5mm/天以上,特别是在长江中游地区; 新疆北部、青海和西藏大部年均降水略有增加,而新疆中部和南部年均降水略有减少。在对流层低层,上新世中期东亚冬季风系统减弱,夏季风系统总体上略有减弱; 在对流层中层,冬季东亚大槽显著减弱,夏季中高纬度地区500hPa位势高度升高。在以上结果中,上新世中期我国气候相对于现在偏暖、东亚冬季风强度减弱得到了代用资料的支持。     

灰色GM(1,1)模型和Verhulst模型在喀斯特地区耕地预测中的应用——以毕节生态试验区为例

毕节生态试验区是典型的喀斯特地区,人口密度大,生态环境脆弱,水土流失严重,耕地保护尤为重要.本文以毕节地区1998-2006年常用耕地面积统计数据为基础,分别利用灰色GM(1,1)模型和Verhulst模型对该喀斯特地区常用耕地面积变化作预测.预测结果表明,GM(1,1)模型和Verhulst模型都揭示了毕节地区常用耕地面积在未来几年呈逐年递减的趋势.但是通过模拟精度验证,研究区耕地面积原始数据变化曲线呈S型,就灰色GM(1,1)模型与Verhulst模型模拟预测结果相比较,对于原始数据的模拟,GM(1,1)模型预测精度较高,而Verhulst模型更适合研究区未来几年耕地面积变化的预测.该研究结果可为区域合理利用土地资源、编制土地利用规划和耕地保护提供依据.     

From geometry to dynamics of microstructure: using boundary lengths to quantify boundary misorientations and anisotropy

The microstructure of a quartzite experimentally deformed and partially recrystallised at 900 °C, 1.2 GPa confining pressure and strain rate 10⁻⁶/s was investigated using orientation contrast and electron backscatter diffraction (EBSD). Boundaries between misoriented domains (grains or subgrains) were determined by image analysis of orientation contrast images. In each domain, EBSD measurements gave the complete quartz lattice orientation and enabled calculation of misorientation angles across every domain boundary. Results are analysed in terms of the boundary density, which for any range of misorientations is the boundary length for that range divided by image area. This allows a more direct comparison of misorientation statistics between different parts of a sample than does a treatment in terms of boundary number.The strain in the quartzite sample is heterogeneous. A 100×150 μm low-strain partially recrystallised subarea C was compared with a high-strain completely recrystallised subarea E. The density of high-angle (>10°) boundaries in E is roughly double that in C, reflecting the greater degree of recrystallisation. Low-angle boundaries in C and E are produced by subgrain rotation. In the low-angle range 0–10° boundary densities in both C and E show an exponential decrease with increasing misorientation. The densities scale with exp(−θ/λ) where λ is approximately 2° in C and 1° in E; in other words, E has a comparative dearth of boundaries in the 8–10° range. We explain this dearth in terms of mobile high-angle boundaries sweeping through and consuming low-angle boundaries as the latter increase misorientation through time. In E, the density of high-angle boundaries is larger than in C, so this sweeping would have been more efficient and could explain the relative paucity of 8–10° boundaries.The boundary density can be generalised to a directional property that gives the degree of anisotropy of the boundary network and its preferred orientation. Despite the imposed strain, the analysed samples show that boundaries are not, on average, strongly aligned. This is a function of the strong sinuosity of high-angle boundaries, caused by grain boundary migration. Low-angle boundaries might be expected, on average, to be aligned in relation to imposed strain but this is not found.Boundary densities and their generalisation in terms of directional properties provide objective measures of microstructure. In this study the patterns they show are interpreted in terms of combined subgrain rotation and migration recrystallisation, but it may be that other microstructural processes give distinctive patterns when analysed in this fashion.     

古湖岸线的识别及其对砂体和油气的控制

古湖岸线是一定历史时期湖平面与古陆地的交线,即陆上与水下沉积的分界线。古湖岸线的识别 过程就是一个沉积环境恢复的过程,识别标志包括地貌特征、特殊岩性、古生物特征、沉积构造、地球化学指 标、地震反射特征以及沉积相变等多个方面。沉积盆地中古湖岸线对于砂体和油气的分布具有明显的控制作用, 主要表现在：（１） 古湖岸线的类型控制了砂体的成因,古湖岸线的位置及迁移控制了砂体的分布和垂向叠加样 式;（２） 古湖岸线控制了优质储集层的形成与发育,一般情况下水下砂体的储集层物性优于水上砂体; （３） 古 湖岸线的频繁迁移为形成良好的储盖组合提供良好的沉积条件; （４） 古湖岸线附近是地层超覆油气藏、不整合 遮挡油气藏及岩性油气藏发育的有利区带,并且油气藏沿古湖岸线呈现裙带状分布。     

美国印第安纳州宾夕法尼亚系含煤地层和煤层简介

美国中部伊利诺伊煤田(跨伊利诺伊、印第安纳、肯塔基等三个州)的含煤地层为上石炭统宾夕法尼亚系。美国印第安纳地质研究所2006年编制的印第安纳州基岩综合地层柱状图建立了宾夕法尼亚系含煤地层的岩相层序,现将此岩相层序介绍到国内,对我们了解美国晚古生代煤田地质及阅读国外文献资料颇有帮助。