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Water transfer characteristics in the vertical direction during methane hydrate formation and dissociation processes inside non-saturated media

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Journal of Natural Gas Chemistry 2010年第2期19卷 139-145页

作者： peng zhang qingbai wu guanli jiang jing zhan yingmei wang state key laboratory Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou 730000 Gansu China

In order to study water transfer characteristics inside non-saturated media during methane hydrate formation and dissociation processes,water changes on the top,middle and bottom locations of experimental media during the reaction processes were continuously followed with a novel apparatus with three pF-meter *** sand,fine sand and loess were chosen as experimental *** was experimentally observed that methane hydrate was easier formed inside coarse sand and fine sand than inside *** hydrate formation configuration and water transfer characteristics during methane hydrate formation processes were very different among the different non-saturated media,which were important for understanding methane hydrate formation and dissociation mechanism inside sediments in nature.

关键词： water transfer methane hydrate formation and dissociation processes non-saturated

Relation between soil matrix potential changes and water conversion ratios during methane hydrate formation processes in loess

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Journal of Natural Gas Chemistry 2011年第2期20卷 140-144页

作者： peng zhang qingbai wu guanli jiang yibin pu state key laboratory of Frozen Soil engineering Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences Lanzhou 730000 Gansu China

With a new apparatus designed and assembled by ourselves, the matrix potential of non-saturated loess was firstly measured and studied during methane hydrate formation processes. The experimental results showed that during two formation processes, the matrix potential changes of the loess all presented a good linear relationship with water conversion ratios. In addition, although it was well known that the secondary gas hydrate formation was easier than the initial, our experimental results showed that the initial hydrate formation efficiency in non-saturated loess was higher than that of the secondary.

关键词： hydrate formation non-saturated loess matrix potential water conversion ratio

Effects of Temperature Gradient and Cooling Rate on the Formation of Methane Hydrates in Coarse Sand

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china Petroleum Processing & Petrochemical Technology 2013年第2期15卷 42-52页

作者： wang yingmei wu qingbai zhang peng jiang guanli state key laboratory of Frozen Soil engineering Cold and Arid Regions Environment and Engineering Research Institute Chinese Academy of Sciences Western china Energy & Environment research Center Lanzhou University of Technology

Temperature gradient and cooling rate have an obvious effect on formation of methane hydrate. The process for formation of methane hydrate in coarse sand is monitored to tmderstand the relationship between temperature gradient and cooling rate and nucleation, growth and distribution of methane hydrate by using the electrical resistivity method. The results show that the change of resistivity can better reflect the nucleation and growth and distribution of methane hydrate. Temperature gradient promotes the nucleation, formation, and formation rate of methane hydrate. At a temperature gradient of 0.11℃/cm, the rate of methane hydrate formation and saturation reaches a maximum. Cooling rate has little effect on the methane hydrate formation process. Judging from the outcome of final spatial distribution of methane hydrate, the cooling rate has an obvious but irregular effect in coarse sand. The effect of tempera^re gradient on distribution of methane hydrate in coarse sand is less than that of cooling rate. At a temperature gradient of 0.07℃/cm, methane hydrate is distributed uniformly in the sample. If the temperature gradient is higher or lower than this value, the hydrate is enriched in the upper layer of sample.

关键词： methane hydrate cooling rate temperature gradient resistivity formation hydrate distribution

Comparison of the water change characteristics between the formation and dissociation of methane hydrate and the freezing and thawing of ice in sand

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Journal of Natural Gas Chemistry 2009年第2期18卷 205-210页

作者： peng zhang qingbai wu yingmei wang state key laboratory of Frozen Soil engineering Cold and Arid Regions Environmental and Engineering Research InstituteChinese Academy of Sciences Lanzhou 730000 Gansu China

Hydrate formation and dissociation processes are always accompanied by water migration in porous media, which is similar to the ice. In our study, a novel pF-meter sensor which could detect the changes of water content inside sand was first applied to hydrate formation and dissociation processes. It also can study the water change characteristics in the core scale of a partially saturated silica sand sample and compare the differences of water changes between the processes of formation and dissociation of methane hydrate and freezing and thawing of ice. The experimental results showed that the water changes in the processes of formation and dissociation of methane hydrate were basically similar to that of the freezing and thawing of ice in sand. When methane hydrate or ice was formed, water changes showed the decrease in water content on the whole and the pF values rose following the formation processes. However, there were very obvious differences between the ice thawing and hydrate dissociation.

关键词： methane hydrate ice formation and dissociation process freezing and thawing process water change

粉土内甲烷水合物形成与分解过程中的水分特征

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天然气地球科学 2009年第4期20卷 616-619,626页

作者：张鹏吴青柏王英梅中国科学院寒区旱区环境与工程研究所冻土工程国家重点实验室甘肃兰州730000

用可探测土壤内部水含量变化的pF-meter探头开展了甲烷水合物形成与分解过程中多孔介质内部水含量变化研究,结果表明,该新型研究方法可有效探测实验过程中多孔介质内水含量变化。通过研究指出:水合物生成时会对介质内的水产生吸力,将水... 详细信息

用可探测土壤内部水含量变化的pF-meter探头开展了甲烷水合物形成与分解过程中多孔介质内部水含量变化研究,结果表明,该新型研究方法可有效探测实验过程中多孔介质内水含量变化。通过研究指出:水合物生成时会对介质内的水产生吸力,将水向水合物处抽吸;水合物分解时会释放水,使介质内水含量增大;温度升高会使存于多孔介质内毛细管中的水向下流动;水合物在粉土中的二次形成范围比一次形成范围更大。

关键词：甲烷水合物形成与分解粉土水分

Methane hydrate formation comparisons in media with and without a water source supply

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research in cold and arid regions 2014年第4期6卷 293-301页

作者： peng zhang qingbai wu state key laboratory of Frozen Soil engineering Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences

Water is a necessary element during gas hydrate formations. Therefore, by analyzing water depletion changes in media, the reaction characteristics of methane hydrate in media can be studied. In this study, two water sources supplying some liquid water which may be consumed by the methane hydrate formation reactions were designed and assembled. Using them, the full formation processes of methane hydrate was studied. Experimental results show the following： If heat released from nucleation reaction of methane hydrate is diffused rapidly, the nucleation ratios will be enhanced discernibly. While the hydrate is formed, a force is generated that sucks fresh water from the source into the vicinity of the hydrate, slowing down the cementation process and causing some hydrate grain dissociation. As a result of cementation differences, the hydrate reaction processes with different water sources present linear or quadratic equation characteristics. After a few repeated dissociation and formation processes of some hydrate grains caused by the fresh water, the gas amounts contained in hydrate will be significantly enhanced.

关键词： water source water transfer methane hydrate formation process

Thermal state of soils in the active layer and underlain permafrost at the kilometer post 304 site along the china-Russia Crude Oil Pipeline

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Journal of Mountain Science 2016年第11期13卷 1984-1994页

作者： wang Yong-ping LI Guo-yu JIN Hui-jun LU Lan-zhi HE Rui-xia zhang peng state key laboratory of Frozen Soils engineering Cold and Arid Regions Environmental and Engineering Research InstituteChinese Academy of SciencesLanzhou 730000China Beifang University of Nationalities Yinchuan 750000China Nanjing Tech University Nanjing 210009China

On-site monitoring is very important for understanding formation mechanisms of frost hazards frequently occurring in pipeline foundation soils and for designing and deploying according mitigative measures in permafrost *** thaw subsidence of ground surfaces along the chinaRussia Crude Oil Pipeline(CRCOP) from Mo'he to Daqing,Heilongjiang Province,Northeast china have been observed at some segments underlain by ice-rich warm(>1.0°C) permafrost since the official operation in January *** monitoring results of the thermal states of foundation soils at the kilometer post(KP) 304 site along the CRCOP are presented in this *** results indicate that during the period from 2012.to 2014,shallow soils(at the depths from0.8 to 4.0 m from ground surface) has warmed by approximately 1.0°C in the lateral range of 1.2 to 2.1 maway from the pipeline axis,and deeper permafrost(such as at the depth of 15 m,or the depth of zero annual amplitude of ground temperatures) by 0.08°C per year 4 m away from the pipe axis,and 0.07°C per year 5 m away from the pipeline *** results indicate an all-season talik has developed around and along the *** thaw bulb,with a faster lateral expansion(compared with the vertical growth),enlarges in summer and shrinks in *** research will provide important references and bases for evaluating thermal influences of warm pipeline on permafrost and for design,construction,operation and maintenance of pipelines in permafrost regions.

关键词： china-Russia Crude Oil Pipeline Permafrost Thermal regime Talik formation Thaw subsidence

Recent changes in ground surface thermal regimes in the context of air temperature warming over the Heihe River Basin, china

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research in cold and arid regions 2014年第4期6卷 273-281页

作者： QingFeng wang TingJun zhang XiaoQing peng Bin Cao state key laboratory of Frozen Soil engineering Cold and Arid Regions Environmental and Engineering Research Institute Chinese Academy of Sciences College of Earth and environmental sciences Lanzhou University National Snow and Ice Data Center Cooperative Institute for Research in Environmental Sciences University of Colorado at Boulder

Changes in ground surface thermal regimes play a vital role in surface and subsurface hydrology, ecosystem diversity and productivity, and global thermal, water and carbon budgets as well as climate change. Estimating spring, summer, autumn and winter air temperatures and mean annual air temperature（MAAT） from 1960 through 2008 over the Heihe River Basin reveals a statistically significant trend of 0.31 °C/decade, 0.28 °C/decade, 0.37 °C/decade, 0.50 °C/decade, and 0.37 °C /decade, respectively. The averaged time series of mean annual ground surface temperature（MAGST） and maximum annual ground surface temperature（MaxAGST） for 1972–2006 over the basin indicates a statistically significant trend of 0.58 °C/decade and 1.27 °C/decade, respectively. The minimum annual ground surface temperature（MinAGST） in the same period remains unchanged as a whole. Estimating surface freezing/thawing index as well as the ratio of freezing index to thawing index（RFT） in the period between 1959 and 2006 over the basin indicates a statistically significant trend of-42.5 °C-day/decade, 85.4 °C-day/decade and-0.018/decade, respectively.

关键词： air temperature ground surface temperature freezing index thawing index tendency rate Heihe River Basin

Early Cretaceous Climate Changes Recorded in Magnetic Susceptibility and Color Index Variations of the Lower Liupanshan Group, Central china

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Acta Geologica Sinica(English Edition) 2016年第3期90卷 1011-1023页

作者： DAI Shuang ZHU Qiang HUANG Yongbo DA SILVA Anne-Christine ZHAO Jie LIU Junwei KONG Li peng Dongxiang LUO Lingling YAN Ningyun wang Wenjie zhang Xiang key laboratory of Western china's environmental Systems(Ministry of Education) College of Earth and Environmental SciencesLanzhou University cold and arid regions environmental and engineering research institute Chinese Academy of Sciences Shandong institute.of geological survey Pétrologie sédimentaire B20Allée du Six Ao t12Quartier AgoraUniversitéde Liège state key laboratory of Continental Dynamics Department of GeologyNorthwest University No.4 institute.of Geological & Mineral Resources Survey of Henan

This study carried out comprehensive analysis on sedimentology, magnetic susceptibility （7of） and color data of the continental sediments of the Liupanshan Group in Central china so as to obtain climatic change information during the 12..14-12..98 Ma interval. Based on the results of the Xlf and of the redness （a＊）, the section can be divided into two segments：（1） 12..14-12..3 Ma, with the lowest Xlf values and strongly variable relatively high values of redness and （2） 12..3-12..98 Ma, with high Elf values and relatively low redness. Analysis of the lithology and facies as well as the magnetic minerals and their contents points to a detrital origin of the magnetic minerals and this allow us to interpret the relationship between magnetic susceptibility variations and climate changes. Our study shows that the climate was significantly dry and hot during the whole studied interval although the interval between 12..3 Ma and 12..98 was a little bit cooler with increased humidity.

关键词： magnetic susceptibility color index climate change Liupanshan Group Early Cretaceous