松散沉积物中天然气水合物生成、分解过程与声学特性的实验研究
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摘要
为了解松散沉积物中天然气水合物的生成和分解规律以及水合物对沉积物声学特性的影响,在粒径为0.18~0.28mm天然沙中进行了甲烷水合物的生成和分解实验,并利用超声波探测技术和时域反射技术实时测量了反应体系的声学参数与含水量。结果表明:根据水合物的生成和分解速率,可将水合物的生成过程分为初始生长期、快速生长期和稳定期3个阶段,分解过程可分为初始分解期和样品表层水合物快速分解期以及样品内、外层水合物均快速分解期3个阶段;由温度和压力数据的分析,得出水合物先在沉积物表层生长,然后在沉积物内、外层迅速生成;由水合物分解过程3个阶段的平均分解率,得出水合物的分解是一个由慢到快的过程。对声学参数的研究表明:水合物在松散沉积物中先胶结骨架颗粒而生成,使纵波速度和声波衰减在饱和度0~1%之间陡然增大;随后水合物开始在沉积物孔隙中形成悬浮粒子,造成超声波信号在饱和度1%~90%间淬熄,声波速度无法获取。研究结果在揭示沉积物中水合物与颗粒间接触机制的同时,为海上地球物理勘探中地震信号的解释提供了新的思路。
To improve our understanding of the evolvement of gas hydrate in sediments and its acoustic impact on unconsolidated sediments,methane gas hydrate was formed and then dissociated in 0.18-0.28 mm sands,and subsequent testing was conducted to enable acoustic properties and water contents to be measured with ultrasonic detection and time domain reflectometry(TDR).The results of testing on several runs of experiments show that both of gas hydrate formation and dissociation could be divided into three periods according to formation speed and dissociation speed,respectively.Based on the analysis of temperature and pressure data,it comes to the conclusion that hydrate forms at the surface of sediments first and dissociates gradually fast during the three periods of dissociation.Moreover,acoustic properties shows that methane gas hydrates have the ability to cement sand grains at hydrate contents around 0-1% leading to a sharp increase in compression velocity and wave attenuation in specimens with no hydrate in the pore space.Whilst hydrates form as a part of the pore fluid and cause the blanking of ultrasonic signal appearing at the period of saturation 1%-90% during gas hydrate formation and dissociation.Consequently,this study reveals the contact mechanism between gas hydrate and sediment grains and provides a new idea to explain seismic signals in oceanic geophysical exploration.
To improve our understanding of the evolvement of gas hydrate in sediments and its acoustic impact on unconsolidated sediments,methane gas hydrate was formed and then dissociated in 0.18-0.28 mm sands,and subsequent testing was conducted to enable acoustic properties and water contents to be measured with ultrasonic detection and time domain reflectometry(TDR).The results of testing on several runs of experiments show that both of gas hydrate formation and dissociation could be divided into three periods according to formation speed and dissociation speed,respectively.Based on the analysis of temperature and pressure data,it comes to the conclusion that hydrate forms at the surface of sediments first and dissociates gradually fast during the three periods of dissociation.Moreover,acoustic properties shows that methane gas hydrates have the ability to cement sand grains at hydrate contents around 0-1% leading to a sharp increase in compression velocity and wave attenuation in specimens with no hydrate in the pore space.Whilst hydrates form as a part of the pore fluid and cause the blanking of ultrasonic signal appearing at the period of saturation 1%-90% during gas hydrate formation and dissociation.Consequently,this study reveals the contact mechanism between gas hydrate and sediment grains and provides a new idea to explain seismic signals in oceanic geophysical exploration.
引文
[1]Milkov A V,Sassen R.Preliminary assessment of resources andeconomic potential of individual gas hydrate accumulations in theGulf of Mexico continental slope[J].Marine and PetroleumGeology,2003,20:111-128.
[2]苏新,宋成兵,方念乔.东太平洋水合物海岭BSR以上沉积物粒度变化与气体水合物分布[J].地学前缘,2005,12(1):234-242.
[3]王家生,高钰涯,李清,等.沉积物粒度对水合物形成的制约:来自IODP 311航次证据[J].地球科学进展,2007,22(7):659-665.
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[6]李明川,樊栓狮,赵金洲.冰成天然气水合物机理分析[J].能源工程,2006,(6):5-7.
[7]Bower P G.Deep ocean field tests of methane hydrate formationfrom a remotely operated vehicle[J].Geology,1997,25:407-410.
[8]刘峰,樊栓狮.海泥石英砂沉积物中甲烷水合物的生成[J].天然气化工,2005,30(2):22-27.
[9]周锡堂,樊栓狮,梁德青,等.石英砂中甲烷水合物的降压分解实验研究[J].天然气化工,2007,32(1):52-55.
[10]黄雯,樊栓狮,李栋梁,等.甲烷水合物在冰粉石英砂混合物中的生成过程[J].武汉理工大学学报,2007,29(3):86-89.
[11]孙志高,樊栓狮,郭开华,等.天然气水合物形成条件与生长过程研究[J].哈尔滨工业大学学报,2005,37(1):108-110.
[12]Kowalsky MB,Moridis J G.Comparison of kinetic and equilibri-um reaction models in simulating gas hydrate behavior in porousmedia[J].Energy Conversion and Management,2007,48:1850-1863.
[13]Kharrat M,Dalmazzone D.Experimental determination of stabili-ty conditions of methane hydrate in aqueous calcite chloride solu-tions using high pressure differential scanning calorimetry[J].The Journal of Chemical Thermodynamics,2003,35(9):1489-1505.
[14]Jones K W,Kerkar P B,Mahajan D,et al.Microstructure ofnatural hydrate host sediments[J].Nuclear Instruments andMethods in Physics Research,2007,261:504-507.
[15]Priest J,Best A,Clayton C,et al.Alaboratory investigation intothe seismic velocities of methane gas hydrate-bearing sand[J].Journal of Geophysical Research,2005,110:B04102,doi:10.1029/2004JB003259.
[16]Winters W J,Pecher I A,Waite W F,et al.Physical propertiesand rock physics models of sediment containing natural and labo-ratory-formed methane gas hydrate[J].American Mineralogist,2004,89:1221-1227.
[17]Winters WJ,Waite WF,Mason D H,et al.Sediment propertiesassociated with gas hydrate formation[M]//The Proceedings ofthe 4thInternational Conference on Gas Hydrates.Yokohama:[s.n.],2002:722-727.
[18]张剑,业渝光,刁少波,等.超声探测技术在天然气水合物模拟实验中的应用[J].现代地质,2005,19(1):113-118.
[19]Wright J F,Nixon F M,Dallimore S R,et al.A method for di-rect measurement of gas hydrate amounts based on the bulk die-lectric properties of laboratory test media[M]//The Proceedingsof the 4thInternational Conference on Gas Hydrates.Yokohama:[s.n.],2002:745-749.
[20]Zhong Y,Rogers R E.Surfactant effects on gas hydrate formation[J].Chemical Engineering Science,2000,55:4175-4187.
[21]Zhang J S,Lee S,Lee J W.Does SDS micellize under methanehydrate-forming conditions below the normal Krafft point?[J].Journal of Colloid and Interface Science,2007,315:313-318.
[22]Topp G C,Zegelin S J,White I.Monitoring soil water contentusing TDR:An reviewof progress[M]//The Proceedings of theSymposiumand Workshop on TDR in Environmental,Infrastructureand Mining Applications.Evanston:[s.n.],1994:67-80.
[23]Sloan E D.Clathrate Hydrates of Natural Gases[M].2nd Edi-tion.New York:Marcel Dekker Inc,1998:175-199.
[24]Matveva TV,Soloveiv V A.Geological control over gas hydrateaccumulation on the Blake outer ridge[J].Geologiya I Geofiz-ika,2002,43(7):658-668.
[25]Ecker C.Seismic characterization of methane hydrate structures[D].Stanford:Stanford University,2001.
[26]Ahrens T J.Mineral Physics&Crystallography:A Handbook ofPhysical Constants[M].Washington:American GeophysicalUnion,1995:7-54.
[27]Helgerud MB,Dvorkin J,Nur A.Elastic-wave velocity in ma-rine sediments with gas hydrates:Effective medium modeling[J].Geophysical Research Letters,1999,26(13):2121-2124.
[28]Dvorkin J,Prasad M.Elasticity of marine sediments:Rock phys-ics modeling[J].Geophysical Research Letters,1999,26(12):1781-1784.
[29]Mavko G,Nur A.Wave attenuation in partially saturated rocks[J].Geophysics,1979,44:161-178.
[30]范百刚.超声原理与应用[M].南京:江苏科学技术出版社,1984:1-133.
[31]孙春岩,章明昱,牛滨华,等.天然气水合物微观模式及其速度参数估算方法研究[J].地学前缘,2003,10(1):191-198.
[32]Dvorkin J,Nur A.Rock physics for characterization of gas hy-drates[M]//Howell D G.The Future of Energy Gases:USGeological Survey Professional Paper 1570.Denver:US Geolog-ical Survey,1993.
[33]宋海斌.天然气水合物的地球物理研究[M].北京:海洋出版社,2003:28-37.
[34]Lee M W.Elastic velocities of partially gas-saturated unconsoli-dated sediments[J].Marine and Petroleum Geology,2004,21:641-650.
[35]Nur A,Mavko G,Dvorkin J,et al.Critical porosity:A key torelating physical properties to porosity in rocks[J].The LeadingEdge,1998,17:357-362.
[2]苏新,宋成兵,方念乔.东太平洋水合物海岭BSR以上沉积物粒度变化与气体水合物分布[J].地学前缘,2005,12(1):234-242.
[3]王家生,高钰涯,李清,等.沉积物粒度对水合物形成的制约:来自IODP 311航次证据[J].地球科学进展,2007,22(7):659-665.
[4]Winters W J,Waite W F,Mason D H,et al.Methane gas hy-drate effect of sediment acoustic and strength properties[J].Journal of Petroleum Science and Engineering,2007,56:127-135.
[5]Priest J,Best A,Clayton C,et al.Seismic properties of methanegas hydrate-bearing sand[M]//The Proceedings of the 5thIn-ternational Conference on Gas Hydrate.Trondheim:[s.n.],2005:440-447.
[6]李明川,樊栓狮,赵金洲.冰成天然气水合物机理分析[J].能源工程,2006,(6):5-7.
[7]Bower P G.Deep ocean field tests of methane hydrate formationfrom a remotely operated vehicle[J].Geology,1997,25:407-410.
[8]刘峰,樊栓狮.海泥石英砂沉积物中甲烷水合物的生成[J].天然气化工,2005,30(2):22-27.
[9]周锡堂,樊栓狮,梁德青,等.石英砂中甲烷水合物的降压分解实验研究[J].天然气化工,2007,32(1):52-55.
[10]黄雯,樊栓狮,李栋梁,等.甲烷水合物在冰粉石英砂混合物中的生成过程[J].武汉理工大学学报,2007,29(3):86-89.
[11]孙志高,樊栓狮,郭开华,等.天然气水合物形成条件与生长过程研究[J].哈尔滨工业大学学报,2005,37(1):108-110.
[12]Kowalsky MB,Moridis J G.Comparison of kinetic and equilibri-um reaction models in simulating gas hydrate behavior in porousmedia[J].Energy Conversion and Management,2007,48:1850-1863.
[13]Kharrat M,Dalmazzone D.Experimental determination of stabili-ty conditions of methane hydrate in aqueous calcite chloride solu-tions using high pressure differential scanning calorimetry[J].The Journal of Chemical Thermodynamics,2003,35(9):1489-1505.
[14]Jones K W,Kerkar P B,Mahajan D,et al.Microstructure ofnatural hydrate host sediments[J].Nuclear Instruments andMethods in Physics Research,2007,261:504-507.
[15]Priest J,Best A,Clayton C,et al.Alaboratory investigation intothe seismic velocities of methane gas hydrate-bearing sand[J].Journal of Geophysical Research,2005,110:B04102,doi:10.1029/2004JB003259.
[16]Winters W J,Pecher I A,Waite W F,et al.Physical propertiesand rock physics models of sediment containing natural and labo-ratory-formed methane gas hydrate[J].American Mineralogist,2004,89:1221-1227.
[17]Winters WJ,Waite WF,Mason D H,et al.Sediment propertiesassociated with gas hydrate formation[M]//The Proceedings ofthe 4thInternational Conference on Gas Hydrates.Yokohama:[s.n.],2002:722-727.
[18]张剑,业渝光,刁少波,等.超声探测技术在天然气水合物模拟实验中的应用[J].现代地质,2005,19(1):113-118.
[19]Wright J F,Nixon F M,Dallimore S R,et al.A method for di-rect measurement of gas hydrate amounts based on the bulk die-lectric properties of laboratory test media[M]//The Proceedingsof the 4thInternational Conference on Gas Hydrates.Yokohama:[s.n.],2002:745-749.
[20]Zhong Y,Rogers R E.Surfactant effects on gas hydrate formation[J].Chemical Engineering Science,2000,55:4175-4187.
[21]Zhang J S,Lee S,Lee J W.Does SDS micellize under methanehydrate-forming conditions below the normal Krafft point?[J].Journal of Colloid and Interface Science,2007,315:313-318.
[22]Topp G C,Zegelin S J,White I.Monitoring soil water contentusing TDR:An reviewof progress[M]//The Proceedings of theSymposiumand Workshop on TDR in Environmental,Infrastructureand Mining Applications.Evanston:[s.n.],1994:67-80.
[23]Sloan E D.Clathrate Hydrates of Natural Gases[M].2nd Edi-tion.New York:Marcel Dekker Inc,1998:175-199.
[24]Matveva TV,Soloveiv V A.Geological control over gas hydrateaccumulation on the Blake outer ridge[J].Geologiya I Geofiz-ika,2002,43(7):658-668.
[25]Ecker C.Seismic characterization of methane hydrate structures[D].Stanford:Stanford University,2001.
[26]Ahrens T J.Mineral Physics&Crystallography:A Handbook ofPhysical Constants[M].Washington:American GeophysicalUnion,1995:7-54.
[27]Helgerud MB,Dvorkin J,Nur A.Elastic-wave velocity in ma-rine sediments with gas hydrates:Effective medium modeling[J].Geophysical Research Letters,1999,26(13):2121-2124.
[28]Dvorkin J,Prasad M.Elasticity of marine sediments:Rock phys-ics modeling[J].Geophysical Research Letters,1999,26(12):1781-1784.
[29]Mavko G,Nur A.Wave attenuation in partially saturated rocks[J].Geophysics,1979,44:161-178.
[30]范百刚.超声原理与应用[M].南京:江苏科学技术出版社,1984:1-133.
[31]孙春岩,章明昱,牛滨华,等.天然气水合物微观模式及其速度参数估算方法研究[J].地学前缘,2003,10(1):191-198.
[32]Dvorkin J,Nur A.Rock physics for characterization of gas hy-drates[M]//Howell D G.The Future of Energy Gases:USGeological Survey Professional Paper 1570.Denver:US Geolog-ical Survey,1993.
[33]宋海斌.天然气水合物的地球物理研究[M].北京:海洋出版社,2003:28-37.
[34]Lee M W.Elastic velocities of partially gas-saturated unconsoli-dated sediments[J].Marine and Petroleum Geology,2004,21:641-650.
[35]Nur A,Mavko G,Dvorkin J,et al.Critical porosity:A key torelating physical properties to porosity in rocks[J].The LeadingEdge,1998,17:357-362.
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