摘要
本文采用一个具有4个待定参数的函数去逼近震源子波,利用黏弹介质中单程波传播理论推导出了地震子波包络峰值处瞬时频率(EPIF)和品质因子之间的解析关系;同时,为提高瞬时频率的估计精度和抗噪性能,在小波域中发展了一种计算瞬时频率的方法,并在此基础上提出了估算VSP资料Q值的方法,简称小波域包络峰值处瞬时频率法(WEPIF).合成的VSP数据衰减估计结果表明,与对数谱比法和中心频率偏移法相比较,WEPIF法受到界面反射波影响相对较小、计算结果稳定、精度相对较高.将WEPIF法用于某气田的单炮零偏6级VSP资料Q值估计,结果表明,吸收强弱与储层含气性高低有良好的对应关系.
In the work,employing a function with four undetermined parameters to model the source wavelet,an analytical relation between Q-factor and envelope peak instantaneous frequency(EPIF)is derived from the theory of one-way waves propagating in an anelastic medium;at the same time,a method for extracting instantaneous frequency(IF)in wavelet domain is developed for improving the precision and anti-noise performance of IF estimation,and based on these,a method called EPIF in wavelet domain(WEPIF)is proposed for estimating Q-factor of VSP data.Test of synthetic zero-offset VSP data indicates that,comparing with logarithm spectral ratio method and centroid frequency shift method,WEPIF method is more stable and precise,and less sensitive to interface reflection waves.The Q-factors of single-shot zero-offset VSP data of 6-series from a certain gas field is estimated by WEPIF method,and the result shows that the extent of absorption corresponds well to the gas saturation of reservoirs.
引文
[1]Ricker N.The form and laws of propagation of seismic wavelets.Geophysics,1953,18(1):10~40
[2]Futterman WI.Dispersive body waves.J.Geophys.Res.,1962,67(13):5279~5291
[3]Kneib G,Shapiro S A.Viscoacoustic wave propagation in2-Drandom media and separation of absorption and scattering of attenuation.Geophysics,1995,60(2):459~467
[4]Winkler K W,Nur A.Attenuation:Effects of pores and frictional sliding.Geophysics,1982,47(1):1~15
[5]Sheriff R E,Geldart L P.Exploration seismology.London:Cambridge Univ.Press,1995
[6]Toks z M N,Shakal A F,Micheal A J.Space-time migration of earthquakes along the North Anatolian Fault Zone and seismic gap.Pure Appl.Geophys.,1979,117:1258~1270
[7]Frisillo A L,Stewart TJ.Effects of partial brine saturation on ultrasonic absorption in sandstone.J.Geophys.Res.,1980,85:5209~5211
[8]马昭军,刘洋.地震波衰减反演综述.地球物理学进展,2005,20(4):1074~1082Ma Z J,Liu Y.A summary of research on seismic attenuation.Progress in Geophysics(in Chinese),2005,20(4):1074~1082
[9]高静怀,杨森林.利用零偏VSP资料估计介质品质因子方法研究.地球物理学报,2007,50(4):251~262Gao J H,Yang S L.On the method of quality factors estimation fromzero-offset VSP data.Chinese J.Geophys.(in Chinese),2007,50(4):251~262
[10]Brzostowski M,Mc Mechan G.3-D tomographic imaging of near-surface seismic velocity and attenuation.Geophysics,1992,57(3):396~403
[11]Gladwin M T,Stacey F D.Anelastic degradation of acoustic pulsesinrock.Phys.Earth PlanetaryInt.,1974,8(3):332~336
[12]Wright C,Hoy D.A note on pulse broadening and anelastic attenuation in near-surface rocks.Phys.Earth Planetary Int.,1981,25(1):1~8
[13]Hauge P S.Measurements of attenuation from vertical seismic profiles.Geophysics,1981,46(11):1548~1558
[14]Stainsby S D,Worthington M H.Qestimation fromvertical seismic profile data and anomalous variations in the North Sea.Geophysics,1985,50(4):615~626
[15]Quan Y,Harris J M.Seismic attenuation tomography using the frequency shift method.Geophysics,1997,62(3):895~905
[16]Zhang C,Ulrych T J.Estimation of quality factors from CMP records.Geophysics,2002,67(5):1542~1547
[17]Matheney M P,Nowack R L.Seismic attenuation values obtained frominstantaneous frequency matching and spectral ratios.Geophys.J.Int.,1995,123:1~15
[18]Aki K,Richards P G.Quantitative Seismology:Theory and Methods.San Francisco:W.H.Freeman&Co.,1980
[19]Dasios A,Astin T R,McCann C.Compressional-waveQ estimation fromfull-waveformsonic data.Geophys.Prosp.,2001,49:353~373
[20]Barnes A E.Instantaneous spectral bandwidth and dominant frequency with applications to seismic reflection data.Geophysics,1993,58(3):419~428
[21]Li HB,Zhao WZ,Cao H,et al.Measures of scale based on the wavelet saclograme with applications to seismic attenuation.Geophysics,2006,71(5):111~118
[22]Barnes A E.Instantaneous frequency and amplitude at the envelope peak of a constant-phase wavelet.Geophysics,1991,56(7):1058~1060
[23]Toks z M N,Johnston D H.Seismic waves attenuation.Soc.Expl.Geophys.,1981,352
[24]Sheriff R E.Encyclopedia dictionary of exploration geophysics:Soc.Expl.Geophys.,1984,194
[25]Waters K H.Reflection Seismology.New York:John Wiely,1978
[26]Gao J H,Li Y M,Chen W C.On the instantaneous attributes analysis of seismic data via wavelet transform.68th SEG meeting,Expanded Abstracts,1998.1084~1087
[27]Gao J H,Dong X L,Wang W B,et al.Instantaneous parameters extraction via wavelet transform.IEEE Tran.on Geoscience and Remote Sensing,1999,37(2):867~870
[28]White R E.Properties of instantaneous seismic attributes.The Leading Edge,1991,10(7):26~32
[29]Ganley D C.A method for calculating synthetic seismograms which include the effects of absorption and dispersion.Geophysics,1981,46(8):1100~1107