Walkaway井地联合地震资料Q值波形反演方法
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摘要
传统的品质因子Q值估算方法通常是基于VSP资料或者叠加的地面地震资料,在薄互层存在的情况下,它们难以提取地震子波及有效地分离固有衰减和散射衰减。为了获得更可靠的地震波衰减图像,研究采用了一种基于Walkaway井地联合地震资料的波形反演来求取Q值的方法。通过理论模型的数值计算分析,探讨了初始模型厚度、Q值及噪声对反演结果的影响。合成的Walkaway井地联合地震资料的衰减估计结果表明,波形反演的Q值估算方法充分利用了各种波的运动学和动力学信息,避免了初至拾取和波场分离等处理困难,并能减小可能的人为误差,提高计算的精度。将该方法用于某油田的高分辨Walkaway井地联合地震资料Q值估计,结果表明,介质品质因子Q与介质性质和孔隙流体有良好的对应关系。
Traditional Q estimation methods were generally based on VSP data or stacked surface seismic data. They are incapable of extracting wavelets and distinguishing the inherent attenuation from the scattering attenuation in the presence of thin interbeds. To obtain a more reliable Q image, a waveform inversion method was developed for estimating Q from the walkaway VSP and surface seismic data. By calculation with theoretical model, the effects of thickness and Q value of the initial mode, as well as the noise on the inversion results were discussed. Theoretical modeling indicates that the waveform inversion for Q estimation can avoid the difficulties in first break pickup and wave field separation by fully utilizing the kinematic and dynamic information of seismic waves. It can also reduce the possible artificial errors, and improve calculation accuracy. The method is used in a certain oil field for estimating the Q from the walkaway VSP and surface seismic data, the result shows that the quality factor Q corresponds well with petrophysics characters of reservoirs.
Traditional Q estimation methods were generally based on VSP data or stacked surface seismic data. They are incapable of extracting wavelets and distinguishing the inherent attenuation from the scattering attenuation in the presence of thin interbeds. To obtain a more reliable Q image, a waveform inversion method was developed for estimating Q from the walkaway VSP and surface seismic data. By calculation with theoretical model, the effects of thickness and Q value of the initial mode, as well as the noise on the inversion results were discussed. Theoretical modeling indicates that the waveform inversion for Q estimation can avoid the difficulties in first break pickup and wave field separation by fully utilizing the kinematic and dynamic information of seismic waves. It can also reduce the possible artificial errors, and improve calculation accuracy. The method is used in a certain oil field for estimating the Q from the walkaway VSP and surface seismic data, the result shows that the quality factor Q corresponds well with petrophysics characters of reservoirs.
引文
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[2]Sun Sh J.Determination of seismic attenuation fromsurface and downhole measurements[D].Oklahoma:University of Oklahoma,2000.
[3]Kjartansson E.ConstantQwave propagation and attenuation[J].J.G.R.,1979,84(4):4737~4748.
[4]Dasgupta R,Clarkz R A.Esti mation ofQfromsurface seismic reflection data[J].Geophysics,1998,63(12):2120~2128.
[5]Quan Y L,Harrisy J M.Seismic attenuation tomography using the frequency shift method[J].Geophysics,1997,62(3):895~905.
[6]王辉,常旭,刘伊克,等.时间域相邻地震波衰减成像研究[J].地球物理学报,2001,44(3):396~402.
[7]马昭军,刘洋.地震波衰减反演研究综述[J].地球物理学进展,2005,20(4):1074~1082.
[8]王辉,常旭,高峰.井间地震波衰减成像的几种方法[J].地球物理学进展,2001,16(1):104~109.
[9]Aki K,Richard P G.Quantitative seismology:theory and methods[M].New York:W.H.Freeman,1980.168~169.
[10]Bickel S H,Natarajan.Plane-waveQdeconvolution[J].Geophysics,1985,50(9):1426~1439.
[11]杨文采.地球物理反演和地震层析成像[M].北京:地质出版社,1989.
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