Heat calculation and numerical simulation in steam mining of permafrost gas hydrate Heat calculation and numerical simulation in steam mining of permafrost gas hydrate

Heat calculation and numerical simulation in steam mining of permafrost gas hydrate

  • 期刊名字:世界地质(英文版)
  • 文件大小:726kb
  • 论文作者:LI Bing,SUN Youhong,GUO Wei,LI
  • 作者单位:College of Construction Engineering,Institude of Exploration Techniques
  • 更新时间:2020-09-15
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论文简介

Global Geology,15(2):135-139(2012)doi:10.3969/isn.1673-9736.201202.08Article D:673-9736(2012)020135-05Heat calculation and numerical simulation in steam miningof permafrost gas hydrateLI Bing, SUN Youhong, GUO Wei and LI Kuan"21. College of Construction Engineering, Jilin University, Changchun 130026, China;2. Institude of Exploration Techniques, CAGS, Langfang 065000, Hebei, ChinaAbstract: Steam mining method was injecting hot steam into the borehole to heat the hydrate strata at the sametime of depressurization mining, which could promote further decomposition and expand mining areas of gas hy-drate. Steam heat calculation would provide the basis for the design of heating device and the choice of the fieldtest parameters. There were piping heat loss in the process of mining. The heat transfer of steam flowing in thepipe was steady, so the heat loss could be obtained easily by formula calculation. The power of stratum heatingshouid be determined by numerical simulation for the process of heating was dynamic and the equations were u-sually nonlinear. The selected mining conditions were 500-millimeter mining radius, 10 centigrade mining tem-perature and 180 centigrade steam temperature. Ileat loss and best heating power, obtained by formula calcula-tion and numerical simulation were 21. 35 W/m and 20 klKey words: gas hydrates; steam mining; heat loss; numerical simulation; best powerIntroductionmining plan, which has the independent propertyrights in China and is devoted to theGas hydrate is a new substitute for energy with hydrate mining, for the hydrate test mining project ingreat potential, green, large reserves, widely distribu- Qilian permafrost of China Geological Survey.ted,shallow burial and large energy density, which2 Steam mining methodplays an important role in alleviating the energy crisisfacing humanity( Liu, 2002). The only way, must be 2.1 Research status of mining methodspassed from endless r d projects to commercial exThe mining methods of gas hydrate include heaploitation of gas hydrate, is pre-production research ing mining, depressurization mining, chemical reaDallimore et al., 2005). Gas hydrate forms in lowgents mining, CO2 replacement method and so on(Wutemperature and high pressure environment Li et et al., 2008 ). Each mining method has its own supeal., 2011). The general idea of gas hydrate mining is riority and limitations. The depressurization mining isfirst breaking down the temperature and pressure equi-the most economical method, but always appears icclibrium conditions to promote hydrate decompositionms, Decause of the heat absorption in the decompoand then pumping the natural gas to the surface sition process of gas hydrate, which would obstruct the(Zhu,2006)further decomposition of the gas hydrate. The energyThe purpose of this paper is developing a set ofTH中国煤化工 ow in the thoughCNMHGReceived 5 Novemher 2011, aecepted 2 December 2011Supported by project of China Geological Surrey( No. GZHL201 10326)136Li B., Sun Y. H., Guo W., et al.of the range is extensive. In order to expand the mincrease gas production, extend the stable time and en-ing area and extend the time of stable gas productionsure the continuity and stability of the gas hydratea new mining method was proposed-steam mining-toexploit hydrate3 Calculation of steam heat2. 2 Principle of steam miningsteamining method, based on the depres-Pluse steam, produced by the heating device orsurization mining, combines the advantages of depresthe surface, has heat loss in pipeline in the process ofsurization mining and heaating miningmining, so the steam heat should include two partssteamis showed in Fig. 1. First, groundwater one is heat loss in pipeline, the other is for gas hyis pumped to the surface through the center channel of drate stratum hethe double-wall drill pipe by the pump at the bottom 3. 1 Heat loss in pipelineof drilling hole, which is associated with fluid levelThe heat transfer of steam flowing in the pipelinedescending. Gas hydrate will break down under low could be used as stable heat transfer(Gao, 2010)pressure as a result of groundwater pumping. At the The pipeline structure is multilayer cylinder with heatsame time, pluse steam, which was produced by the preservation outside( Fig. 2). Formula(1)is theheating device and injected into the extraction well formula of heat loss. According to the mining planthrough the outward channel of the double-wall drillthe related parameters of the pipe and steam were lis-pipe, heats the hydrate stratum for further decomposi- ted in Table 12m(T,-T)High temperature steam+-·ln-+·ln-+A·1A“n1A2“27起(a+aNatural gasIn this formula, is heat loss (W/m)ia &ais the convective heat transfer coefficient between theDouble-wall drill pipesteam and pipe heat preservation and air(W/mC); a, is radiation heat transfer coefficient (W/mC:A,& A, is the heat conduction coefficient ofpipe and heat preservation(W/m.C); T.& T is theGas hydrateGas hydratetemperature of steam and environment(tTable 1 Related parameters of pipe and steamParameters valuesParamelersvaluesTA℃53.6T℃A2/W·m1·℃-1Diving pumpr1/m0.0300.036Fig 1 Principle of steam mining method中国煤化工CNMHGIn theory, Steam mining method could promTHsresult or neat loss is: 21. 35hydrate decomposition, expand the mining area, in-W/mHeat calculation and numerical simulation in steam mining of permafrost gas hydrate137fine the temperature and pressure at the entrance is453 K and 1. 0 MPa, and the temperature of stratum273The power of steam is variable in numerical simulation. Four sets of simulation have been carriedfor 45 hours without stopping in this paper.Theing power is 5 kW, 10 kW, 20 kw and 50 kw.Thefollowing is the result of the four sets of numerical3.3.3BesTo be mined radius and temperature were set atFig 2 Pipeline structure0. 5 m and 10C. The results of the four sets of simulation show in Table 23.1 Numerical simulation of stratum heatingThe process of steam heating gas hydrate stratumTable 2 Results of the numerical simulationis dynamic, and the equations for calculating areSP/kWIT/℃IMR/mOT/℃OMR/mally non-linear, which can not be calculated in1800.500.42normal way. Numerical simulation was used by means51of FLUENT 6. 3 in this paper3.3.1 Basic assumptions and control equation0.53ne asstions should be set in numericalNote: SP-steam power: IT-inlet temperature; IMR-inlet minedsimulation for the heating process was very complexradius; OT-qutlet lemperature: OMR-outlet mined radiusFirst, thermal physical parameters of steam and stra-tum were constant. Second, the heat absorbed of hyFrom the numerical simulation, it shows: Thedrate phase changing wasn't calculatedsteam temperature is the main factor affecting the heatThe heat transfer between steam and stratum istransfer compared with velocity of flow. The fasterheat exchange and heat convection. Control equationsteam flows, the smaller the temperature difference(2)between the import and exportp,as-(p1·c1·n1)·+2·(AT)+Select the best power is 20k W through the com-parison of the simulative results. Compared with 5 kW(A。·T)(A,·T)(2)and 10 kW, The temperature difference between theIn this equation, T, Pi, C, and v, refer to the import and export of 20 k W is smaller. The mined ratemperature(C), density(kg/m), specific heatimport and export is basically the(J/kg.C)and speed(m/s)of the steam, respec- which can meet the mining demand. The power of 50tively.P, &e A, is the density(kg/m)and specifikw can increase the mined radius. but the increaseheat(W/m. C)of stratum3. 3. 2 Numerical simulation3. 3. 4 Heating timeFirst. build theric model and divide中国煤化工 peraturechanges atsIzeCNMHGm power of 20 kW.2.0 x1.0 m. Second, define the properties of mate-Atemperature changes, the stratumrials, initial conditions and boundary conditions. Deneeds to be heated for 38 hours138Li B, Sun Y H, Guo W., et al.4 Conclusionsmethod combines the advantages of depressurizationmining method and heating method. In the(1)A new mining method was proposed for Per- mining method could prevent the self-protective effectmafrost gas hydrate in this paper. The steam mining to promote further decomposition of gas hydratebsteam-outsteam-ou376343steam-n2734534们987steam-antsteam-Insteam-Ina. The heating power is 5 kW; b. The heating power is 10 kW; c. The heating power is 20 kW; d. The heating power is 50 kWFig 3 Temperature cloud maps in different heating powers(2 )The method of formula was used to calculatethe heat loss in pipeline and the heat loss in pipelinewas 21. 35 W/m(3)Select the best power is 20 kW throughresults of the numerical simulation. The stratum needsto be heated for 38 hours to meet the mining demandReferences中国煤化工te. Exploration Engi-C MH Gese with English abFig 4 Stratum temperature changesDallimore S R. Collett T S. 2005. Scientific results from theHeat calculation and numerical simulation in steam mining of permafrost gas hydrate139Mallik2002 gas hydrate production research well program513-520. ( in Chinese with english abstrarMackenzie Delta, Northwest Territories, Canada. GeologWu CZ, Zhao K B, Sun C C, et aL. Current research in natu-al Survey of Canada, Bulletin, 1-585ral gas hydrate production. Geological Science and TechLiG S, SUN Y H. 2011. Design and field application of gasnology Information, 27(1): 47-52.( in Chinese withhydrate drilling mud cooling system. Exploration Engi-English abstracteering, 38(2):8-11.( in Chinese with English ab-Gao XT, Wu G S. 2010. The mechanism and experimentalstudy on the distillation of superheated steam in heavy oilZhu Y H. 2006. Production test from gas hydrate of Mackenziereservoirs. Journal of Oil and Gas Technology, 32(3)permafrost, Canada. Advances in Earth Science, 21(5)344-366.( in Chinese with English abstract中国煤化工CNMHG

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