13 October 2015, Volume 33 Issue 19

    

Special Issues
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Special Issues
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  Current status and prospect of hot dry rock research

  LU Chuan, WANG Guiling

  Science & Technology Review. 2015, 33(19): 13-21. https://doi.org/10.3981/j.issn.1000-7857.2015.19.001

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  Hot dry rock contains a huge amount of geothermal energy and is one of the most important resources being explored in developed countries. The enhanced geothermal system (EGS) has been developed on the basis of hot dry rock utilization. EGS related science and technologies have been developed for decades, which are abundant in theoretical research and engineering practice. This paper reviews the developing courses of several important EGS projects, summarizing their successes and lessons, and provides a comprehensive discussion of the key scientific and technical achievements and deficiency, including new progress in high temperature geothermal systems. Prospect of their future development is predicted.
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  Research on the occurrence types and genetic models of hot dry rock resources in China

  GAN Haonan, WANG Guiling, LIN Wenjing, WANG Xiao, MA Feng, ZHU Xi

  Science & Technology Review. 2015, 33(19): 22-27. https://doi.org/10.3981/j.issn.1000-7857.2015.19.002

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  As a significant part of geothermal resources, hot dry rock (HDR) resources have attracted increasing attention due to their clean, stable, reproducible characteristics and huge potential of high temperature geothermal power generation. China started research on HDR resources since the 1990s, and has successfully explored and predicted quite a few HDR resources deposits. However, until now, we have not classified HDR resources and studied the genetic mechanisms of their occurrence, which hinders the exploration and precise potential estimation of HDR resources in China. Based on the geological indicators of the occurrence of HDR resources and genetic analysis of them in the world and the crustal structure in China, this paper divides the HDR resources into four types, i.e. the high radioactive heat production type, the sedimentary basin type, the modern volcano type and the intraplate active tectonic zone type. The genetic mechanisms of different types of HDR resources are analyzed and compared, and the prospect regions of HDR resources are proposed, which may provide references for precise potential estimation of the HDR resources in China.
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  Site selection and development prospect of a hot dry rock resource project in Zhangzhou geothermal field, Fujian province

  LIN Wenjing, WANG Fengyuan, GAN Haonan, MA Feng, WANG Guiling

  Science & Technology Review. 2015, 33(19): 28-34. https://doi.org/10.3981/j.issn.1000-7857.2015.19.003

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  Hot dry rock (HDR) geothermal resources have been listed in the national energy development plan by increasing countries owing to their incomparable advantages over conventional fossil fuels. HDR research is still at the early stage in China. Based on analyses of exploitation projects of HDR in the world, we propose several geothermal and geological indexes for HDR development. We take the HDR resource project in Zhangzhou geothermal field as an example to discuss the rules and indexes for site selection through analyses of acidic rock distribution, cap rock condition, deep geothermal anomaly, and regional stability. We also build a conceptual model of the drilling area of Zhangzhou geothermal field, estimate the deep geothermal reservoir temperature, and put forward suggestions for future development of HDR geothermal resources in Zhangzhou.
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  Laboratory study of hydraulic fracturing on hot dry rock

  XU Tianfu, ZHANG Yanjun, YU Ziwang, HU Zhongjun, GUO Liangliang

  Science & Technology Review. 2015, 33(19): 35-39. https://doi.org/10.3981/j.issn.1000-7857.2015.19.004

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  Hot dry rock (HDR), which contains abundant geothermal energy, is a new type of geothermal resources and has become the worldwide focus in new energy utilization and development. The field test of enhanced geothermal engineering for development of HDR resources is costly, risky, and time-consuming. Therefore, it is necessary to carry out laboratory test for investigating the property of HDR before field fracturing and construction of artificial geothermal reservoir. The most urgent and essential problem is the research on hydraulic fracturing and micro seismic monitoring technology in the process of utilizing HDR. To further explore this issue to provide parameters and technical support for field fracturing and reservoir stimulation, Jilin University established a HDR laboratory simulation system that can carry out hydraulic fracturing of large-sized samples under high temperature and pressure. This paper focuses on the testing instrument, testing conditions and research results of the simulation system.
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  Key technology and development of hot dry rock drilling

  JIA Jun, ZHANG Delong, WENG Wei, HUANG Yuwen, SHAN Wenjun, XIONG Zhengqiang

  Science & Technology Review. 2015, 33(19): 40-44. https://doi.org/10.3981/j.issn.1000-7857.2015.19.005

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  Hot dry rock resource is clean and renewable energy with abundant reserve. Exploitation of hot dry rock resource requires drilling to the reservoirs and establishing an enhanced geothermal system (EGS). Hot dry rock formations are usually igneous rock with poor drillability and high temperature, which is a huge challenge to the drilling technology, equipment and materials. Based on analysis of the characteristics of and difficulties in hot dry rock drilling, this paper introduces the key technology and development, including high-temperature drilling fluid, downhole motor, well control, igneous rock fracturing and distributed temperature measurement, and discusses the focus and direction of drilling technology research, which may provide references for managers, researchers and engineers.
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  Well control techniques in hot dry rock drilling

  ZHANG Delong, WENG Wei, JIA Jun, HUANG Yuwen, FENG Meigui

  Science & Technology Review. 2015, 33(19): 45-48. https://doi.org/10.3981/j.issn.1000-7857.2015.19.006

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  Hot dry rock formations are usually igneous rock with poor drillability and high temperature. Circulation loss, blowout, well kick and other drilling accidents occur frequently in hot dry rock drilling. Domestic well control techniques and equipment cannot meet the requirement of hot dry rock drilling. To satisfy the need of high-temperature well control and guarantee construction safety, this paper analyzes the relationship between the formation temperature, pressure and blowout and designs a high-speed rotary blowout preventer and control system with simple structure and high-temperature capacity, which can improve the drilling efficiency and reduce drilling risks.
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  Analysis of the potential and development prospects of shallow geothermal energy and hot dry rock resources

  MA Feng, WANG Xiaoyuan, WANG Guiling, LIN Wenjjing, LI Honglei

  Science & Technology Review. 2015, 33(19): 49-53. https://doi.org/10.3981/j.issn.1000-7857.2015.19.007

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  Shallow geothermal energy and hot dry rock have the most utilization potential among geothermal energy. The former is used to offer indoor heating or cooling to reduce the country's energy demands, and the latter is used to generated electricity to increase the national renewable energy supply. Both of them have tremendous potentials and are environmentally friendly, and the development technology named ground source heat pump and enhanced geothermal systems share some similarities. This paper compares the basic concept, resource potential, energy-saving effects, economic benefit and environmental impacts between shallow geothermal energy and hot dry rock, discussing their advantages and disadvantages and development prospects. Based on the characteristics of geothermal resources in China and the national planning on energy development, geothermal development is suggested to go deeper in the future.
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  Characteristics of Gonghe Basin hot dry rock and its utilization prospects

  YAN Weide

  Science & Technology Review. 2015, 33(19): 54-57. https://doi.org/10.3981/j.issn.1000-7857.2015.19.008

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  The national and local governments have carried out a series of explorations of geothermal resources in the Chapcha (Qia-bu-qia) region, Gonghe County, Hainan Tibetan Autonomous Prefecture in Qinghai Province since 2011. It has been discovered that Gonghe Basin substrate is composed of the indosinian granite with a significantly high geothermal gradient up to 11.5℃/100 m. The temperature reached 150℃ at the level of 2200 m and was close to 200℃ at 3000 m and was estimated to be 260℃ at 4000 m, indicating that the basin has widely distributed hot dry rock in relatively shallow depth. Utilization of such hot dry rock resources will not only fill up the gap in China's new energy utilization, but also improve local residents'living conditions as well as develop local industry and agriculture.
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  Geothermal field characteristics and heat generation rate of radioactive elements in Taishan rock group at Chenzhuang uplift, Shandong Province

  TAN Xianfeng, WANG Hao, ZHANG Zhenyu

  Science & Technology Review. 2015, 33(19): 58-61. https://doi.org/10.3981/j.issn.1000-7857.2015.19.009

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  Radioactive elements exist in rock in the nature, which will release energy in the decaying process. Radioactive heat production is one of the main sources for lithospheric heat. Some basic information has been obtained about Chenzhuang uplift, Shandong Province as a hot dry rock exploration and study site. This paper calculates the radiogenic heat ratio of the rock core using Rybach heat generation rate formula, on the basis of analysis of terrestrial heat flow and geothermal field. The vertical distribution of heat generation rate at GRY1 borehole shows that the heat generation rate was larger with greater variation above 1650 m, and reached 4.72-6.78 μW/m³ at depth of 1430-1645 m, where biotite adamellite and chloritized adamellite mainly exist. At the interval of 1645-2500 m, where the rock is mainly composed of granite, biotite bearing diorite, and gabbro, the heat generation rate decreased. Overall, the heat generation rate of granite changed slightly, which was about 2.0-2.5 μW/m³, while that of biotite adamellite and slightly chloritized adamellite was higher with larger variation.
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  Numerical simulation of hot dry rock exploitation using enhanced geothermal systems in Gonghe Basin

  YUE Gaofan, DENG Xiaofei, XING Linxiao, LIN Wenjing, LIU Feng, LIU Yanguang, WANG Guiling

  Science & Technology Review. 2015, 33(19): 62-67. https://doi.org/10.3981/j.issn.1000-7857.2015.19.010

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  Hot dry rock, which will become one of the most important resources in the future, can be developed and utilized using enhanced geothermal systems (EGSs). Hot dry rock resources are abundant in Gonghe basin, Qinghai province. Complex waterthermal coupling processes occur during water flow in the reservoir, and the power generation capacity of power plants is dependent on the EGS operation scheme. Based on the deep geological conditions of Qiabuqia in Gonghe basin, we established a numerical model to characterize the hydrothermal features of EGS, researched the temporal and spatial distribution of the temperature field and pressure field, and analyzed the influence of injection temperature and flow rate on heat extraction rate. The results show that the maximum heat extraction rate reached 11Mw under the base scheme (20kg/s, 60oC), and the reservoir life was 22 years. The heat extraction rate will increase by about 10% with 10oC increase of injection temperature, while the reservoir life remains the same. Increased flow rate will lead to a greater rate of heat extraction but shorter reservoir life.
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  Hot dry rock geothermal resources in Ru County

  LONG Xiting, YUAN Ruiqiang, DENG Xinping, LI Fang, PI Jing, LI Honglei

  Science & Technology Review. 2015, 33(19): 68-73. https://doi.org/10.3981/j.issn.1000-7857.2015.19.011

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  Ru County is rich in hot dry rock geothermal resources with a 98℃ hot spring distributed. However, research on the resources is scarce. This study evaluated the hot dry rock geothermal resource in Ru County on the basis of borehole temperature measurement and terrestrial heat flow survey. The results show that the average geothermal gradient was 18.7℃/100 m with a max of 35.2℃/100 m and the heat flow changed between 60 and 170 MW/m². Heat came from the deep magma in the geothermal field. The geothermal reservoir was composed of dense fractures produced by sub-faults in the upper part of F1 fault and F3 fault. The cover of the geothermal reservoir contained exposed granite on the east side of the Reshui River and Sinian slate on the west side. According to our model, the temperature was 260℃ on the lower site and 255℃ on the upper site. The stratum thickness is about 3500-4000 m above the geothermal reservoir. In Ru County, the geothermal reservoir has a shallow burial depth and a high temperature belonging to a suitable destination area of hot dry rock development.
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  Relative permeability of the steam-water system of porous media

  LIU Yanguang, WANG Xiaoyuan, LU Chuan, WANG Guiling, LI Honglei

  Science & Technology Review. 2015, 33(19): 74-77. https://doi.org/10.3981/j.issn.1000-7857.2015.19.012

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  The relative permeability of the two-phase steam-water system is an essential property in resource evaluation, dynamic analysis and numerical simulations of high-temperature geothermal systems. This paper introduces the mechanism of steam-water relative permeability in geothermal systems, reviews the latest research progress in this field, and proposes future directions for experimental measurement and numerical simulation.
Articles
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  Jamming jam method based on covariance matrix

  GE Shibin, YU Huabing, CHEN Xinhua, SUN Changyu

  Science & Technology Review. 2015, 33(19): 78-83. https://doi.org/10.3981/j.issn.1000-7857.2015.19.013

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  The jamming jam method (JJM) uses the previous information of the interference to construct a matrix to cancel the interference. However, in the scenario that the signal is embedded in the interference, signal detection is a very difficult problem because the signal will be severely attenuated in interference cancellation. A jamming jam method based on covariance matrix is proposed to deal with this problem. The proposed method will get the Toeplitz averaged covariance matrix from the covariance matrix of the receiving signal, and then uses the Toeplitz averaged covariance matrix to frame the block matrix. The features of the covariance matrix are used to realize the jamming jam method. The proposed method weakens signal attenuation caused by interference suppression which is beneficial to detect the signal. Theoretical analysis and computer simulation show that compared to the JJM, the modified algorithm can effectively cancel interference and reduce signal attenuation.
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  On the Mogi-Coulomb strength criterion as applied to rock triaxial unloading test

  LI Diyuan, XIE Tao, LI Xibing, WANG Tao

  Science & Technology Review. 2015, 33(19): 84-90. https://doi.org/10.3981/j.issn.1000-7857.2015.19.014

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  To testify the Mogi-Coulomb criterion in triaxial unloading test and based on available unloading testing data, the Mogi-Coulomb strength criterion with a linear fitting method was used in the conventional triaxial unloading tests and the true triaxial unloading tests, respectively. A comprehensive comparative analysis was presented for the related strength parameters according to the fitting results and combination of the failure characteristics of rock specimens. The results showed that the Mogi-Coulomb strength criterion has a good applicability to rock samples under conventional triaxial unloading conditions. However, under true triaxial unloading tests, even though the fitting degree is very good, the fitting parameter a is negative which leads to a negative cohesion of rock samples. This is impossible in practice. Since the Mogi-Coulomb strength criterion is based on the assumption that rock fails in shear, it cannot describe the failure of rock under true triaxial unloading conditions in which the failure modes of rocks specimens may change from shear to extensional slabbing or rock burst. Therefore, for combined shear and tensile failure processes of rocks under true triaxial unloading conditions, it is necessary to build a new strength criterion to describe its constitutive relationships, which is important for deep rock mechanics.
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  Development of well-to-seismic integration reservoir modeling and its application

  ZHANG Yi, YIN Yanshu, QIN Zhiyong, ZHOU Wen

  Science & Technology Review. 2015, 33(19): 91-95. https://doi.org/10.3981/j.issn.1000-7857.2015.19.015

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  The characteristics of high-density sampling of seismic data and well data in the horizontal and vertical directions are integrated to construct the reservoir model for the Section B of a gas field of China. Firstly, the well-to-seismic integration calibration is used to interpret the fine structure, and the accurate velocity model is adopted to set up a bridge between the time domain of seismic data and depth domain of well data. Secondly, the reservoir structural model is built by well correlation under the constraint of the fault and horizon from seismic interpretation. Thirdly, a co-simulation method is developed to forecast the sand distribution, in which well data is the master variable and the lithology probability from seismic inversion is the second variable. The facies model is built on the basis of sand distribution model. Finally, the model of petro-physical property is built under the constraint of the facies model. Appliction has indicated that reservoir modeling with well-to-seismic integration is more accurate in terms of fault and sand body prediction between wells, thereby the improvement of accuracy of the reservoir model.
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  Multi-objective optimization configuration for special equipment materials on warship

  DONG Qi, XU Tingxue, ZHAO Jianzhong, CONG Linhu

  Science & Technology Review. 2015, 33(19): 96-101. https://doi.org/10.3981/j.issn.1000-7857.2015.19.016

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  This paper studies the multi-objective optimization configuration of special equipment materials on warships during the mission at sea. Considering the configuration characteristics of special equipment materials on warships, we establish a multiobjective and multi-constraint model with the fill rate and utilization rate as the optimization target, and volume, mass, and cost as the constraints. The multi-objective Particle Swarm Optimization (PSO) algorithm is designed and improved, guaranteeing diversity of particles at the global scope and avoiding excessively fast convergence, to obtain globally optimal solution. We further compare the calculation results between the improved algorithm and standard algorithm, analyzing the optimal configuration under different weight ratio and tendencies under different constraints. The results demonstrate the stability of the improved algorithm and practicability of the multi-objective model.