多孔介质中甲烷水合物生成的排盐效应及其影响因素刘昌岭

　27　520069ACTAPETROLEISINICAVol.27　No.5Sept.2006　:(863)“”(2001AA6110-20)。:,,19665,2005,,。E-mail:[e-mail]:0253-2697(2006)05-0056-05刘昌岭1　陈　强2　业渝光1　赵广涛2　张　剑1　刁少波1(1.　　266071;　2.　　266003):利用不同粒径的多孔介质模拟了海洋天然气水合物的生成过程,测定了孔隙水中主要离子质量浓度的变化。研究结果表明,甲烷水合物的生成过程使周围沉积物孔隙水中离子质量浓度发生异常。水合物生成引起的排盐效应主要取决于耗气量。耗气量越大,生成水合物的量越大,排盐效应也就越强,但孔隙水溶液中不同离子质量浓度的变化并不一致。高频振动大大加快了反应速度;粗颗粒(粒径大于125μm)沉积物对水合物生成速度影响不大,而细颗粒(粒径小于74μm)沉积物则明显阻碍水合物的生成。压力对排盐效应的影响体现在反应时间上。在相同反应条件下,反应时间与过冷温度呈幂函数关系。:多孔介质;甲烷水合物;离子质量浓度;排盐效应;地球化学特征:P744.4　　　　:ASalt-removingeffectandaffectingfactorsforformingmethanehydrateinporousmediaLiuChangling1　ChenQiang2　YeYuguang1　ZhaoGuangtao2　ZhangJian1　DiaoShaobo1(1.QingdaoInstituteofMarineGeology,Qingdao266071,China;2.CollegeofMarineGeosciences,OceanUniversityofChina,Qingdao266003,China)Abstract:Methanehydratesformedinporousmediawithdifferentsizeswereexperimentedinlaboratory.Theconcentrationsofmainionsinporewaterbeforeandafterexperimentsweredetermined.Itwasfoundthattheionicconcentrationsinporewatershowedob-viouslyanomalousduringgashydrateformationinporousmedia.Thesalt-removingeffectduringformationofgashydratewasdomi-natedbymethaneconsumption.Moregasconsumptionresultedinalargeamountofgashydrateandstrongersalt-removingeffect.However,variationsofconcentrationsfordifferentionsweredifferentintheporewater.Thehigh-frequencyvibrationcouldacceler-atereactiongreatly.Thecoarsesedimentswithgraindiametersover125μmhadlittleinfluenceonformationspeedofmethanehy-drates,whereasthefinesedimentswithgraindiametersbellow74μmobviouslyobstructedformationofmethanehydrates.Theinflu-enceofpressureonsalt-removingeffectindicatedthatthereactiontimeandthesubcoolingtemperaturesubmittedarelationshipofpowerfunctionunderthesameconditions.Keywords:porousmedia;methanehydrates;ionicconcentration;salt-removingeffect;geochemicalcharacteristic　　,、。,。,,,。HesseHarrison[1],ODP164Blake、、、、[2-4]。,(0.51‰～8.2‰)(19.8‰)。,SO2-4[5],SO2-4,。,。NaCl[6-7][8]、,,　5:57　　　,。[8],,()。,,,,。1　1.1　、、、(1)。,,200cm3,30MPa。1,,。2Pt100。,1.;2.A/D;3、4.;5.;6.;7.;8.;9.;10.;11.;12.;13.;14、15.;16.;17、18.;19.;20.1　Fig.1　Schematicdiagramofexperimentalapparatusformethanehydrate。。,。,3600～7200r/min,,。,99.9%。1.2　,6,500～700μm、355～500μm、250～355μm、180～250μm、125～180μm74～63μm,27%～32%。5%48h,,。,[9],。,(SDS)0.03%,[10]。,60mL,18mL,。,,。,,。。,,,,,1mL50mL,(TDS)。。;;;(ICP-AES)、、、。2　2.1　,,,。,,3。,,,,()(600mL3h);(2),,,(600mL10min),20,。:①,—,;②,,58　　　　　　　　　2006　27　。,。2。,T1,T22　Fig.2　Generationofmethanehydrateinporousmedia,MF。2,4min,,200mL/min;10min,,。,(T2),1.5℃,,(T1)。2.2　——,6,,1。K+0.42g/L,Na+7.12g/L,Ca2+0.33g/L,Mg2+1.24g/L,Cl-19.2g/L,SO2-42.65g/L,31.1g/L。1,(74～63μm),5。250～355μm180～250μm,、;1　Table1　Experimentalresultsforthesedimentswithdifferentsizes/μm/%/MPa/mL/min/℃/(gL-1)K+Na+Ca2+Mg2+Cl-SO2-4TDS/(gL-1)500～70032.077.29110918.25.770.439.670.441.3122.62.9039.5355～50027.857.1336410.05.200.458.910.511.3621.53.2536.2250～35528.317.00114619.73.140.5111.30.591.4824.83.3542.1180～25027.646.94108318.93.000.5011.10.581.4224.63.2041.5125～18027.447.1489716.13.510.4810.70.441.2923.93.0540.174～6328.217.1224725.02.520.458.950.431.2221.82.8733.1(500～700μm),,,250～355μm180～250μm。(74～63μm),(2.52℃)(),。,1000mL,。、,74μm。1,,,,,,(TDS)。,,。3,Ca2+,80%;Na+25%～60%;SO2-4Cl-15%～30%,15%。3　Fig.3　Variationratiosofionicconcentrationsinsedimentswithdifferentsizes。2.3　,180～250μm5,。　5:59　　　2。2,,,,。,。,。2　Table2　Experimentalresultsunderdifferentpressures/MPa/mL/℃/℃/℃/min/(gL-1)4.044962.804.351.5598.835.24.975103.216.052.8422.935.86.105153.247.804.6112.235.36.945103.008.855.858.935.98.075053.5710.356.784.935.1[11],。(NaCl0.035)[12],。,(2)。4,4　Fig.4　Relationshipbetweenreactiontimeandsubcoolingtemperature,()t=204.8×T-1.88　　(r=0.99)(1)　t,min;T,℃。2.4　——,6、,K+、Na+、Ca2+、Mg2+、SO2-4Cl-。12,K+、Na+、Ca2+、Mg2+Cl-,。Ca2+,Na+。,。5,Na+Ca2+,0.930.92。,Na+Ca2+。5　Fig.5　Relationshipsbetweengasconsumptionandvariationratiosofionicconcentration,,。6,(TDSm),0.976。,,,(TDSc)。6　Fig.6　Relationshipsbetweengasconsumptionandthetotaldissolvedsalt　　TDS0,nm=Q/22400(2)　Q,mL;nm,mol;224001mol,mL。　CH4+5.75H2O=CH45.75H2O+ΔH(3)60　　　　　　　　　2006　27　　　,1mol5.75mol。nw=5.75×nm(4)　nw,mol。Vw=18×nw/ρ(5)　ρ,g/mL;Vw,mL;18,g/mol。VV=V0-Vw(6)　V0,mL。　　TDS=TDS0×V0/V=TDS0×V0/(V0-Vw)(7)　　(7)(6),(600mL),,;,,,。,()。6,TDS,1,,。,。3　,,。,,,,。,。;,,。,,();(125μm),(74μm)。,,。[1]　HesseR,HarrisonWE.Gashydrates(clathrates)causingpore-waterfresheningandoxygenisotopefractionationindeep-watersedimentarysectionsofterrigenouscontinentalmargins[J].EarthPlanet.Sci.Lett,1981,55(3):453-462.[2]　WatanabeY,MatsumotoR,LuHL.TraceelementgeochemistryoftheBlakeRidgesedimentsatSite997[J].ScientificResults,2000,164:151-163.[3]　LuHL,MatsumotoR,WatanabeY.Majorelementgeochemis-tryofthesedimentsfromSite997,BlakeRidge,WesternAtlan-tic[J].ScientificResults,2000,164:147-149.[4]　HesseR,FrapeSK,EgebergPK,etal.Stableisotopestudies(Cl,OandH)ofinterstitialwatersfromSite997,BlakeRidgeGasHydrateField,WestAtlantic[J].ScientificResults,2000,164:129-137.[5]BorowskiWS,PaulCK,WilliamUsslerIII.Globalandlocalvariationsofinterstitialsulfategradientsindeep-water,continen-talmarginsedim