08 November 2012, Volume 30 Issue 32

    

Spescial Issues
Articles
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Spescial Issues
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  A Roadmap to Geothermal Energy Development in China

  PANG Zhonghe;HU Shengbiao;WANG Jiyang

  . 2012, 30(32): 18-24. https://doi.org/10.3981/j.issn.1000-7857.2012.32.002

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  China possesses a high potential of geothermal energy. A suitable roadmap for technology and industry development is required in order to realize the vision making demand on global climate change mitigation. It is proposed that the future of geothermal technology development in China will be characterized by the diversification of sources and utilizations, the scale enlargement of development projects, the refinement of advanced technologies, and sustainability guarantee. The geothermal industry development will be focused on low-medium temperature direct use and high- temperature geothermal power generation in the near future, power generation from low-medium temperature in middle period, and Hot Dry Rock (HDR) energy combined heat and power in the long term. The leading role playing by government, supplementing by the coordination among researchers, educators, producers, and consumers will be the key to successful geothermal technology and industry development in China.
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  Estimate of Geothermal Resources Potential for Hot Dry Rock in the Continental Area of China

  WANG Jiyang;HU Shengbiao;PANG Zhonghe;HE Lijuan;ZHAO Ping;ZHU Chuanqing;RAO Song;TANG Xiaoyin;KONG Yanlong;LUO Lu;LI Weiwei;

  . 2012, 30(32): 25-31. https://doi.org/10.3981/j.issn.1000-7857.2012.32.003

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  As one of the clean renewable energy, geothermal energy is very competitive. According to its genesis and exploration conditions, geothermal resources could be divided into two kinds, that is, one is hydrothermal resources and the other one is Hot Dry Rock (HDR) geothermal resources. Because of its universality and high temperature, HDR geothermal resources have great potential for projecting future development. The assessment of HDR geothermal resources potential is the base of HDR resources exploration. Here the heat flow map in the continental area of China is updated on the basis of more new heat flow data. Then the HDR geothermal resources are estimated using volume methods with a thermal physical access in the continental area of China (3 km —10 km). Results show that the total HDR geothermal energy is 20.9×10⁶EJ, which is equivalent to standard coal of 714.9×10¹²t. If the recoverable energy is 2% by computing, then it is 168 times of conventional hydrothermal energy, and it is equivalent to 4,400 times of total annual energy consumption during the year of 2010 in China. Nevertheless, due to the limitation of economics and technology, the HDR geothermal resources exploration within the depth of 4km—7km accompanied with an expected temperature of 150—250 ℃ should be conducted in the near future. Several target regions for HDR geothermal resources exploration are proposed, including South Tibet, West Yunnan (Tengchong), the southeast coast of China (Zhejiang, Fujian and Guangdong), North China (BBB basin), the southeast regions of Ordos Basin (Fenwei Graben), and Northeast China (Songliao Basin). Finally, the future tasks involving geothermal resources research are listed.
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  Evaluation and Efficient Development of Geothermal Resource Associated with Oilfield

  LI Kewen;WANG Lei;MAO Xiaoping;LIU Changwei;LU Juhong

  . 2012, 30(32): 32-41. https://doi.org/10.3981/j.issn.1000-7857.2012.32.004

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  The methods for estimating geothermal resources coexisted in oil and gas fields have been investigated and modified according to the difference between conventional and coproduced geothermal resources. The current status of geothermal resources coexisted in oil and gas fields in China has been reviewed and studied. The main factors that affect reservoir temperature have been investigated using numerical simulation. The modeling results showed that the decline rate of reservoir temperature decrease with the decrease in water reinjection rate but decrease with the increase in temperature of reinjected water. The advantages of power generation using geothermal energy coexisted in oil and gas reservoirs have been analyzed in comparison with using solar and wind energy. Some of the pilot projects of power generation using coproduced geothermal energy in the world have been appraised and discussed. "High efficiency method for producing oil-heat-electricity simultaneously" has been proposed after the feasibility of generating electricity using coproduced geothermal resources was proved. The method can meet the requirements from both enhanced oil recovery and developing geothermal energy. Finally, potential and prospect of efficiently developing and utilizing geothermal resources coexisted in oil and gas fields, especially electricity generation, have been analyzed and predicted.
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  Technology Progress in an Enhanced Geothermal System (Hot Dry Rock)

  XU Tianfu;ZHANG Yanjun;ZENG Zhaofa;BAO Xinhua

  . 2012, 30(32): 42-45. https://doi.org/10.3981/j.issn.1000-7857.2012.32.005

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  Enhanced Geothermal System (EGS), known as Hot Dry Rock (HDR), is an engineering technology where the heat energy is extracted from low permeability and low porosity rock, namely, HDR in order to gain the quantity of energy. Although the history and development of EGS has been more than 30 years, only a small number of countries in the world have a voice in this respect, such as the United States, Britain, France, Germany, Switzerland, Japan, Australia, etc. The basic concept, research and development status, key technologies, issues and expectation involving the EGS are mainly discussed.
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  Kalina Cycle of Geothermal Power Production

  ZHU Jialing;LU Zhiyong;ZHANG Wei;FU Wencheng

  . 2012, 30(32): 46-50. https://doi.org/10.3981/j.issn.1000-7857.2012.32.006

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  In July 2000, Kalina cycle is first time used in Husavik, Iceland and is considered to be one of the most promising ways for utilizing the low-temperature heat sources. By using the software of EES, a calculating program is compiled to simulate the cycle process and the results have fitted with the actual operating parameters quite well. On this basis, the influence factors, such as turbine inlet pressure and mass fraction of ammonia which associated with the cycle efficiency are analyzed. In addition, the safe operating range of turbine is calculated and the exergy loss is sized up.
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  Advances in the Drilling Technologies for High Temperature Geothermal Power

  ZHA Yongjin;FENG Xiaowei;GE Yunhua;CHEN Zhixue;

  . 2012, 30(32): 51-54. https://doi.org/10.3981/j.issn.1000-7857.2012.32.007

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  Ultra high temperature drilling is the key technology of high temperature geothermal power generation, the breakthrough of which will enhance the development of the deep high-temperature geothermal power generation industry. We analyze the major technical problems of high temperature geothermal drilling, which include high-temperature well control, ultra high temperature drilling mud, high-temperature well cementing and completion, tools and instruments that suit for the high temperature condition, high temperature well trajectory measurements and control, rock-breaking efficiency in high temperature condition, and so on. As for those problems, the experts both at home and aboard have developed many technological responses, such as, the safety well control of the high temperature geothermal drilling, anti-high-temperature cement, anti-high-temperature down-hole tools, well trajectory monitor and control, anti-high-temperature drill bits and drilling rate, and so on. We also provide an example of the deep high-temperature geothermal drilling in Kenya at last.
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  Geothermal Power Generation and Its Comprehensive Cascade Utilization System

  LUO Chao;GONG Yulie;MA Weibin;

  . 2012, 30(32): 55-59. https://doi.org/10.3981/j.issn.1000-7857.2012.32.008

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  It becomes a hot topic that geothermal resources are effectively utilized; there is rich geothermal resource located in the remote areas in China. Based on the situation and development trend of geothermal utilization, the ammonia water power cycle is introduced and the cycle performance criteria, such as net power output, net power energy per ton of geothermal water, heat efficiency, and heat exchanger area of per net power, are presented. In addition, a demonstration project of geothermal resource cascade utilization in south China area is discussed, the resource utilization rate is more than 70%. The results indicate that AWPC cycling performance could be changed by adjusting the mass fraction of the ammonia solution, a higher ammonia mass fraction solution is favorable for protecting the system from the negative pressure, and the higher mass fraction is, the higher pressure is. There is an optimal circulation ratio in AWPC system, the value is about four for the mid-low temperature geothermal resource and the corresponding mass fraction difference between concentrated solution and dilute solution is about 12%—13%. The mode exploits a new way for efficiently utilizing the mid-low temperature geothermal resource.
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  New Progress in the World Geothermal Power Generation

  Roland N. Horne;LI Kewen

  . 2012, 30(32): 60-66. https://doi.org/10.3981/j.issn.1000-7857.2012.32.009

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  The history of geothermal power generation in the world has been briefly reviewed. In the past five years, considerable changes in the geothermal development have been brought. Historically high oil prices since 2005, supporting by a global ambition to address greenhouse gas reduction have impelled every country in the world paying attention to the renewable energy. Geothermal developments have accelerated in many parts of the world, either in the countries, such as New Zealand, Indonesia, and the USA having a traditional interest in conventional geothermal resources, or in the countries having no historical interest in geothermal energy, such as Australia and Germany. The analysis conducted indicates that some new developments have followed well-worn paths using conventional hydrothermal resources in volcanic regions, while others have struck out in new directions involving Enhanced Geothermal System (EGS) projects in non-volcanic regions. Technology advance has allowed to developing conventional resources with lower temperature, restricted water access, and constrained surface utilization. EGS projects have launched in a variety of different directions and places, currently the USA keeps six EGS projects in operation. Based on current status, the future for the operation expansion of geothermal developments depends on new fields exploration and technical challenges overcoming in known but not-yet-exploited fields. Two issues are currently being addressed by the world geothermal community, they are (1) the productivity gap in the exploitation of fields, namely, temperature is too high for down-hole pumps, however it is too low for flash production; (2) the reliable EGS development procedures are able to ensure sustainable flow rates and assure the public that seismologic disasters will not be induced.
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  Radiation Effect of Porous Materials with Cylindrical Cavities

  CHEN Fuli

  . 2012, 30(32): 67-70. https://doi.org/10.3981/j.issn.1000-7857.2012.32.010

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  Porous materials possess superior mechanical and thermal performances, and have been widely used in aeronautics, astronautics, atomic energy, transportation etc industries. The effect of the radiation for the heat transfer property of the porous materials with the cylindrical cavities is studied. The micromechanics methods, ie dilute, self-consistent and Mori-Tanaka methods, are extended to predict the effective thermal conductivity of porous materials accounting for the radiation effect at high temperature. The compact closed form formula of the local effective thermal conductivity is derived, which is very convenient for engineering application. A comparison with available theoretical predictions is made to demonstrate the accuracy of the present formula. The dilute and self-consistent methods give unreasonable predictions for the relative high porosity. The Mori-Tanaka predicts reasonable solutions. Numerical examples reveal a lot of interesting interaction phenomena of pores on heat transfer. It is seen that the local effective thermal conductivity divides into two parts: one attributes to conduction and the dimensionless conductivity by pure conduction is independent of temperature and pore size, whereas the other is due to thermal radiation in the pores and strongly depends on temperature and pore size, which is negligible at low temperature and in the case of small pores.
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  Prediction of Gas Content in Coal Seam Without Being Perturbed by Mining Influence in Wuyang Mine Based on Gray Theory

  LI Sheng;NING Zhiyong;ZHU Xiaoqiang;YANG Yongsheng

  . 2012, 30(32): 71-74. https://doi.org/10.3981/j.issn.1000-7857.2012.32.011

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  From the geology exploration borehole data in the mining areas 76 and 78 of Wuyang Mine, eleven reliable boreholes are selected, together with data related with five influencing factors of the gas content, including the buried depth of the coal-bed, the rock properties of the coal seam (the ratio of the sandstone to the mudstone in the 30m coal seam roof and floor), the coal thickness, the geological structure and the degree of the coal metamorphism (volatile matter and ash). Two kinds of gray relational analysis methods are used-the Deng's relational degree and the generalized relational degree-- to study these influencing factors of the gas content in the coal seam under the condition of without mining, and the GM(1,7), GM(1,6) and GM(1,5) gas content prediction models are established. The results show that, for the case without mining affecting the coal seam, in the mining areas 76 and 78 of No.3 Wuyang Mine, the ratio of the sandstone to the mudstone in the 30m coal seam floor, the geological structure, the volatile matter and the ash are four main influencing factors of its gas content. The GM(1,5) gas content prediction model built by the four factors enjoys the highest prediction accuracy, which can be used to predict the gas content in cases without mining affecting coal seam in the mining areas 76 and 78 of No.3 Wuyang Mine. The predictive value can provide the basis for the prevention and the treatment of coal mine gas disasters, and also has important practical significance for the mine safe production.
Reviews
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  Research Progress in 3-Hydroxybenzo[a]pyrene-biomarker of Benzo[a]pyrene

  HOU Hongwei;ZHANG Xiaotao;XIONG Wei;TANG Gangling;HU Qingyuan

  . 2012, 30(32): 75-79. https://doi.org/10.3981/j.issn.1000-7857.2012.32.012

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  Benzo[a]pyrene (B[a]P) is a main toxic chemical component with tobacco smoking, which is a carcinogen to humans according to the adequate evidence from animals. 3-hydroxybenzo[a]pyrene (3-OHB[a]P) is a biomarker of B[a]P exposure. 3-OHB[a]P could be used to distinguish the populations with different levels of exposure, such as smokers, nonsmokers, occupational exposure population, and general population, and to determine the differences in metabolism. The research progress in 3-OHB[a]P is reviewed. Firstly, the carcinogenicity of B[a]P is discussed. And then the source of 3-OHB[a]P as well as the determination method of 3-OHB[a]P are reviewed. The applications of 3-OHB[a]P in biological monitoring are elaborated in detail, including occupational exposure population, smoking population, and the general population. Starting from the exist problems and current research status on 3-OHB[a]P, the prospects for applying 3-OHB[a]P to the study of biological monitoring smokers and general population are analyzed.