速度差对井间走时层析成像质量的影响及其改进方法
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摘要
在井间地震初至走时层析成像中,随着相邻地质体速度差的增大,使得射线分布不均匀,以及网格剖分不合适,导致层析成像结果不理想.物理和数值模型的井间走时层析成像表明:当速度差超过30.0%时,层析结果畸变较大;在30.0%~15.0%之间时,层析结果较好;低于15.0%时,层析结果好.在此基础上,提出了井间多尺度初至走时层析成像方法,即对同一模型采用多种网格剖分来同时进行层析成像,以获得研究区域的速度图像.数学和物理模型的井间多尺度走时层析结果表明:该方法很好地兼顾了层析成像的分辨率和精度,极大地改善了井间地震层析成像的质量.即使速度差超过30%,其多尺度的层析结果仍然较好.因此,这种方法具有实际应用的潜力.
The quality of the tomographic result is not good as expected because of the uneven ray coverage caused by increasing velocity contrast of the neighboring geological bodies and the inappropriate grid discretization in crosswell seismic first-break traveltime tomography.The tomographic results of physical and numerical models prove that when the velocity contrast is greater than 30.0%, its tomographic result will be deformed significantly,when between 30.0% and 15.0%,it will be acceptable,and when less than 15.0%,it will be very good.The multi-scale crosswell traveltime tomography is proposed on the above basis.The method is a simultaneous traveltime tomography using various grid discretizations for the same model to obtain velocity reconstructive images of a study area.The tomographic results of numerical and physical models show that this method simultaneously considers the resolution and accuracy of tomography and can significantly improve the quality of crosswell tomography.Even if the velocity contrast is more than 30.0%,multiscale tomographic results are still good.Therefore,this method can be applied to real crosswell seismic data tomography.
The quality of the tomographic result is not good as expected because of the uneven ray coverage caused by increasing velocity contrast of the neighboring geological bodies and the inappropriate grid discretization in crosswell seismic first-break traveltime tomography.The tomographic results of physical and numerical models prove that when the velocity contrast is greater than 30.0%, its tomographic result will be deformed significantly,when between 30.0% and 15.0%,it will be acceptable,and when less than 15.0%,it will be very good.The multi-scale crosswell traveltime tomography is proposed on the above basis.The method is a simultaneous traveltime tomography using various grid discretizations for the same model to obtain velocity reconstructive images of a study area.The tomographic results of numerical and physical models show that this method simultaneously considers the resolution and accuracy of tomography and can significantly improve the quality of crosswell tomography.Even if the velocity contrast is more than 30.0%,multiscale tomographic results are still good.Therefore,this method can be applied to real crosswell seismic data tomography.
引文
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[14]王辉,常旭.基于图形结构的三维射线追踪方法.地球物理学报,2000,43(4):534~541Wang H,Chang X.3_D ray tracing method based on graphicstructure.Chinese J.Geophys.(in Chinese),2000,43(4):534~541
[15]陈国金,曹辉,吴永栓.最短路径层析成像技术在井间地震中的应用.石油物探,2004,43(4):327~330Chen G J,Cao H,Wu Y S.Shortest path tomographic techniqueapplied in the crosswell seismic.Geophysical Prospecting forPetroleum(in Chinese),2004,43(4):327~330
[16]赵群,郝守玲.井间地震观测系统的物理模型研究.石油物探,2004,43(3):298~300Zhao Q,Hao S L.Physical model study using crosswell seismicobservation system.Geophysical Prospecting for Petroleum(inChinese),2004,43(3):298~300
[17]陈国金,高志凌,吴永栓.自动生成井间层析成像初始速度模型的方法研究.石油物探,2005,44(4):339~342Chen G J,Gao Z L,Wu Y S.The method of automatically buildingthe initial velocity model used in the seismic tomography.GeophysicalProspecting for Petroleum(in Chinese),2005,44(4):339~342
[2]Todi J L.Velocity analysis without picking.Geophysics,1989,54(2):191~199
[3]Harris J M,Nolen_Hoeksema R C,Langan R T,et al.Highresolution crosswell imaging of a west Texas carbonate reservoir:Part1 Project summary and interpretation.Geophysics,1995,60(3):667~681
[4]安艺敬一,P G理查兹.定量地震学.北京:地震出版社,1987Keiiti Aki,Paul G Richards.Quantitative Seismology:Theory andMethods.W H Freeman Company,1980
[5]刘福田,李强,吴华等.用于速度图像重建的层析成像法.地球物理学报,1989,32(1):46~61Liu F T,Li Q,Wu H,et al.On the tomographic inverse methodused in velocity image reconstruction.Chinese J.Geoghys.(inChinese),1989,32(1):46~61
[6]Zhou Hua_wei.Multiscale traveltime tomography.Geophysics,2003,68(5):1639~1649
[7]Vesnaver A.The contribution of reflected,refracted and transmittedwaves to seismic tomography:A tutorial.First Break,1996,14(5):159~168
[8]Bohm G,Vesnaver A.In quest of the grid.Geophysics,1999,64(4):1116~1125
[9]Vesnaver A,Bohm G.Staggered or adapted grids for seismictomography.The Leading Edge,2000,19:944~950
[10]Dynes K A,Lytle R J.Computerized geophysical tomography.Proc.IEEE,1979,67:1065~1073
[11]Moser T J.Shortest path calculation of seismic rays.Geophysics,1991,56(1):59~67
[12]刘洪,孟凡林,李幼铭等.计算最小走时和射线路径的界面网全局方法.地球物理学报,1995,38(6):823~831Liu H,Meng F L,Li Y M,et al.The interface grid method forseeking global minimum traveltime and the correspondent ray path.Chinese J.Geoghys.(in Chinese),1995,38(6):823~831
[13]张建中,陈世军,余大祥.最短路径射线追踪方法及其改进.地球物理学进展,2003,18(1):146~150Zhang J Z,Chen S J,Yu D X.Shortest path algorithm ray tracingdynamic networks.Progress in Geophysics(in Chinese),2003,18(1):146~150
[14]王辉,常旭.基于图形结构的三维射线追踪方法.地球物理学报,2000,43(4):534~541Wang H,Chang X.3_D ray tracing method based on graphicstructure.Chinese J.Geophys.(in Chinese),2000,43(4):534~541
[15]陈国金,曹辉,吴永栓.最短路径层析成像技术在井间地震中的应用.石油物探,2004,43(4):327~330Chen G J,Cao H,Wu Y S.Shortest path tomographic techniqueapplied in the crosswell seismic.Geophysical Prospecting forPetroleum(in Chinese),2004,43(4):327~330
[16]赵群,郝守玲.井间地震观测系统的物理模型研究.石油物探,2004,43(3):298~300Zhao Q,Hao S L.Physical model study using crosswell seismicobservation system.Geophysical Prospecting for Petroleum(inChinese),2004,43(3):298~300
[17]陈国金,高志凌,吴永栓.自动生成井间层析成像初始速度模型的方法研究.石油物探,2005,44(4):339~342Chen G J,Gao Z L,Wu Y S.The method of automatically buildingthe initial velocity model used in the seismic tomography.GeophysicalProspecting for Petroleum(in Chinese),2005,44(4):339~342
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