Characterization of deep ground geothermal field in Jiahe Coal Mine

Mining Science and Technology( China)21(2011)371-374Contents lists available at Science Directnad lect ai!氵Mining Science and Technology( China)ELSEVIERjournalhomepagewww.elsevier.com/locate/mstcCharacterization of deep ground geothermal field in Jiahe Coal MineZhang Yi Guo Dongming, He manchao, Jiang Yaodong. Yang QingState Key Laboratory of geomechanics and Deep Underground Engineering Beijing 100083, ChinaSchool of Mechanics and Civil Engineering China University of Mining G Technology. Beijing 100083, ChinaARTICLE OABSTRACTArticle history:Research into the characteristics of geothermal fields is important for the control of heat damage inReceived 12 October 2010Received in revised form 9 November 2010mines. Based on measured geothermal data of boreholes from -200 m to-1200 m in a Jiahe Coal Minecepted 7 December 2010we demonstrate non-linear but increasing relations of both geo-temperatures and geothermal gradientsAvailable online 17 June 2011ith increases depth. Numerically, we fitted the relationship between geotemperatures and depth, atial decay curve. formulated as: T(h)--4975+ 23.08 x exp(h/1736.1).8 2011 Published by Elsevier B.V. on behalf of China University of Mining Technologyexothermal fieldeat damageFunction1 Introductiona theoretical knowledge base for heat damage control in deepThe geothermal field of a mine is in the shallow part of the earthe. est, affected by deep geothermal and regional geologic structures 2 Characteristics of a deep geothermal field in the Jiahe Coaland disturbed by factors such as the activities of underground Minewater and local heat sources[1-6. Therefore, the condition of dif-ferent geothermal fields is not only affected by various geotectonicIn order to analyze the distribution of the geothermal fieldelements and depth, but also by the different geologic structures of between-200 m and-1200 m in the Jiahe Coal Mine, 22 holes werethe shallow part of the earth crest, given the same geotectonic ele- bored to different depths for temperature measurements within thements and geothermal backgrounds at the same depth Factors mining field. These measurements are presented in Table 1which strongly disturb a geothermal field may cause significantchanges in the field [7-1012. 1. Analysis of characteristics on geothermal changeThe Jiahe Coal Mine, located in the Xuzhou mining area, is clas-sified into substratum depressions in terms of its geothermal fieldCurves showing geothermal changes for each hole from -200 mIts geology is characterized by large and medium sized settlement. to -1200 m have been drawn from Table 1. We only show fourzones, situated in a stable platform block, with deep crystal sub- curves, all with similar characteristicsstrates Paleozoic, Mesozoic and Cenozoic erathem sedimentaryThe data from Table 1 have been plotted as Fig. 1 showing sharpbasins have been formed over it [11-13). Actual measured data geothermal temperature increases with increasing depth. These inin this mine show that, in general, no heat damage occurs when creases are nonlinearmining depth is less than-500 to-600 m, but may occur when Using data from Table 1 can also be used to show geothermining occurs at even lower levels.variation in ground temperatures at depths from -200 m toAnalysis of the characteristics of this geothermal field is impor1200 m(see Fig. 2).tant for providing direction and information in order to controlAs shown in Curve 5. each stratum in a certain depth has itsheat damage. We present a case study conducted in this mine, to range of temperature changes respectively which shows uniforminvestigate the characteristics of its geothermal held and obtaining distribution features of the geothermal temperature within eachrock stratum. Oscillating trend can be seen from geothermal tem-perature change curves in the specific depth and the fluctuation le-m212vel is increased with the increase of depth, that is, geothermaltemperature sulaf mining depth, whichZhang)中国煤化工ent.1674-5264/5- see front matter e 2011 Published by Elsevier B V. on behalf of China University of miningCNMHGdoi:101016mstc20110501372Y Zhang et aL/ Mining Science and Technology(China )21(2011)371-374Table 1Temperature contrasts at same depths(C).Depth200(m)-300(m)-400(m)-500(m)-600m)-700(m)-800(m)-900(m)-1000(m)-1100(m)-1200(m)18-1220922424.225.827829,433.923.728.337922.73.827428.830733.03.828429923.427827.129.034.836.7202233032634.741.924626.027.531634.136.722023.525.02628630.131321-523.527.124.525.62733.0648.942.222-1228034.138.039.141221.427.637423-723.027.02330.13234.236.240023-1223.52526.931.034.622.524.226027.729631534.024.32542627.829.231.13334.735.838341525.230934623.526427.833438941.021.1426433.038442.33.32.72.2(a)Temperature(C)(b)Temperature (C)Temperature(C)Temperature(℃)19222528313437402528313437404325283134374041922252831343740431200Fig 1.d temperature(a)Well 18-12, (b)Well 18-14 (c)Well 20-11. (d) Well Sup102.2. Analysis of characteristic on geothermal gradient changeshown in this paper since similar change characteristics for allthe curvesGeothermal gradient is the direct reason for heat transfer [14].According to the analysis on the curves from Fig 3a-d, geotherHeat transfer among strata increases with the increase of geother- mal gradient generally shows nonlinear increase with the increasemal gradient, which results in more evident heat exchange [15]. of stratum depth.Therefore, in order to get a clearer picture about the distributionThe curve of geothermal gradient change from -200 m toof geothermal temperature in Jiahe Coal Mine, geothermal gradient -1200 m in Jiahe Coal Mine can also be available based on the dataof each hole are listed statistically in Table 2.in Table 2(see Fig. 4)Curve of geothermal gradient change of each hole from mAs shown in Fig. 4, most of geothermal gradient values are atto-1200 m can be obtained from Table 2. Only four curves are the range of 1.0C/100 m and 2.5C/100 m, indicating that geo-thermal changes from -200 m to -1200 m in Jiahe Coal mine arwell-proportioned. According to further analysis of the changesof geothermal gradient curves from different depth, geothermal-200mgradient increases with increase of depth and nonlinear increasecan be seen from the curve-500m3. Relationship between geothermal temperature and the depthof deep parts in Jiahe Coal Mine一=1000mFrom data obtained in the Jiahe Coal Mine and given the analysis of changes in geothermal temperatures and geothermal gradi1200ments, we fitted numerically a first order exponential attenuationHH中国煤化工epsCNMHGFig. 2. Variation in ground temperature at different depthsT(h)=-4(1Y. Zhang et aL/ Mining Science and Technology( China) 21(2011)371-374Geothermal gradients.Well -200 to-800to-300(r-1m)1m物1m5m900(m)-1000(m)1200(m)18-121.51.8161618-141.1251.619-91.420-100.95362120-111416221.72.62.24.2sup101.2142.02.12.5up111.515121.73.3up13 1.62.023-111.21.31.72.22.023-12161.72.02.1p151184-93.46-101.718219439108926-91.339(a)Temperature()(b)Temperature('O) (c)Temperature(C)(d)Temperature(C)200300m200300m20030m200300m400500m400500m400500m400500m600700600700m鼠600700m600700800900m800900m800900m800900m10001100m10001100m10001100m10001100mg 3. Variation in geothermal gradient. (a)Well 18-12, (b) Well 18-14. (c)Well 20-11. (d)Well Sup10Temperature(C)24283236200率Number1200Fig. 5. Geothermal temperature as a function of depth in Jiahe Coal Mine.500--600-1100--1200geothermal temperature increases with the increase of depth andFig. 4. Variation in ground gradient at different depths.temperature gradient shows nonlinear increase with the increaseof depth4. ConclusionsAs indicated in the curve, the curve shows approximately linearly changes for the depth from -200 m to-700 m, to be specific(1) Geothermalfor shallow part above -700 m underground, the curve showshe increasbasically linear distribution, while the curve change for deepthe featuresYH中国煤化工 radient withCNMH Gms of increasingining(in the depth of =700 m to-1200 m)is as follows: the37Y. Zhang et aL/Mining Science and Technology( china)21(2011)371-374(2)Generally, the increase of geothermal temperature show[4] Xie Q Chen YP. Analysis of earth temperature field character and prediction ofabove -700 m while it is nonlinear when the depth exceeds [5) Yang She3177-9(in chinling railway tunnel. J Southwest Jiaotong Univapproximately linear when the depth of Jiahe Coal MineW. Micmte evaluation system in thermal700m, the relationship between geothermal temperaturemines. i China Univ1上1-4 in englishand depth is formulated by Eq (1).[6] Luo YP, Wang L Research on non-stinsulating matenals. J China UnivTechnol2008:18(1)116-2l[n[71 Ma JX Study on temperature field and plan of the heat preservation andAcknowledgmentsyer on the extra-long highway tunnel in high attitudeFinancial support for this project, provided by the National Basic[8] Wan Zh]. zhaoJR Simulation and forecast methodrock Chin J Rock Mech Eng 2005: 24( 6): 945-9 (inResearch Program of China(No. 2006CB202200), the Key Project ofNational Natural Science Foundation of China and the Program for[9] He YL, Yang LZh, Yang M. A quantitative method for the coupling effect ofChangjiang Scholars, Innovative Research Team in University ofrature fields and stress fields in rock mass. J SoutChina(No iRTo656)and the Fundamental Research Funds for the [101 YuJ Ma ZhY. Wang Zhw u wL Su Y Oxygen and hydrogen isotope exchangeCentral Universities(No. 2010QL04), is gratefully acknowledged.pressured thermal water in the central Guanzhong basin. J ChinaUniyThanks Pro. 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