横向各向同性介质纵波方位各向异性物理模型研究
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摘要
Ruger公式表明:在各向异性介质中,当各向异性参数、纵波阻抗、横波速度、介质密度已知的情况下,反射系数是方位角和入射角的二元函数;若采用固定炮检距观测方式,只改变测线与裂缝方向之间的夹角,则反射系数可化简为方位角的一元函数,根据Ruger公式便可得到不同炮检距下的反射系数值。本文基于Ruger公式,运用物理模型模拟方法,在水中以50,100,150mm的炮检距观测了HTI介质的地震响应,了解了反射波振幅、反射旅行时随裂缝方位角变化的规律。研究表明:在不同炮检距情况下,裂缝层顶、底界面的反射纵波振幅均出现方位AVO响应,即当方位角为0°时,纵波反射振幅最大,当方位角为90°时,纵波反射振幅最小;裂缝对纵波旅行时也产生影响,即反射时间随方位角增大而增大。物理模拟实验结果与理论计算结果相近,从而为裂缝识别和预测提供了借鉴。
Ruger formula demonstrates that in isotropic media if the isotropic parameters,P-wave impedance,share wave velocity and medium density are known,then the reflection coefficient is the dualistic function of the reflection coefficient and incidence angle. However if the fixed offset was adopted for the observation,only changing the included angle between seismic line and azimuth,then the reflection coefficient can be simplified to simple function of the azimuth,so from Ruger formula the reflection coefficients can be derived for different offsets. Based on Ruger formula and by using physical modeling method,the seismic response for HTI media in the water were observed in 50mm,100mm and 150mm offset respectively. The changing rule of reflection wave amplitude and reflection wave travel time with azimuth was understood. The studies demonstrates that when offsets change,the reflection P-wave amplitude on the top and bottom of the fracture layer shows azimuth AVO response,when azimuth is 0 degree,the reflection P-wave amplitude is maximum,when azimuth is 90 degree the reflection P-wave amplitude is minimum,the P-wave travel time is also affected by fracture,that is,reflection time increases with the azimuth increase,the results from physical modeling experiment are close to the results from the theoretical calculation,it is believed that the studies provides reference for fracture recognition and prediction.
Ruger formula demonstrates that in isotropic media if the isotropic parameters,P-wave impedance,share wave velocity and medium density are known,then the reflection coefficient is the dualistic function of the reflection coefficient and incidence angle. However if the fixed offset was adopted for the observation,only changing the included angle between seismic line and azimuth,then the reflection coefficient can be simplified to simple function of the azimuth,so from Ruger formula the reflection coefficients can be derived for different offsets. Based on Ruger formula and by using physical modeling method,the seismic response for HTI media in the water were observed in 50mm,100mm and 150mm offset respectively. The changing rule of reflection wave amplitude and reflection wave travel time with azimuth was understood. The studies demonstrates that when offsets change,the reflection P-wave amplitude on the top and bottom of the fracture layer shows azimuth AVO response,when azimuth is 0 degree,the reflection P-wave amplitude is maximum,when azimuth is 90 degree the reflection P-wave amplitude is minimum,the P-wave travel time is also affected by fracture,that is,reflection time increases with the azimuth increase,the results from physical modeling experiment are close to the results from the theoretical calculation,it is believed that the studies provides reference for fracture recognition and prediction.
引文
[1]Mallick S,Frazer L N.Reflection/Transmission co-efficients and azi muthal anisotropy in marine seismic studies.Geophysics,1991,56(1):241~252
[2]Ruger A.P-ware reflection coefficients for transverse-lyisotropic models with vertical and horizontal axis of symmetry.Geophysics,1997,62(3):713~721
[3]Ruger A.Variation of P-ware reflectivity with offset and azi muth in anisotropic media.Geophysics,1998,63(2):692~706
[4]Gray D,Head K.Fracture detection in Manderson field:A3-D AVAZ case history.The Leading Edge,2000,19(11):1214~1221
[5]乐绍东.AVA裂缝检测技术在川西J M构造的应用.天然气工业,2004,24(1):22~24
[6]郝守玲等.EDA介质的P波方位各向异性——物理模型的研究.石油地球物理勘探,1998,33(增刊2):54~62
[7]刘洋,董敏煜.各向异性介质中的方位AVO.石油地球物理勘探,1999,34(3):261~267
[8]李国发等.利用三维地震资料勘探纵波方位振幅随偏移距变化技术检测煤田裂缝.科学通报,2005,50(增刊I):138~142
[9]李磊.横向各向同性介质Thomsen近似公式的适用范围.石油物探,2008,47(2):117~122
[10]苏魏,陈树民等.各向异性介质弹性波场成像的Thomsen参数影响研究与分析.大庆石油地质与开发,2007,26(2):123~126
[11]Chang Y and Chang C.The line singularities of the body wares in anisotropic media:Physical modeling result.Expanded Abstracts of70th SEG Mtg,2000,2468~2471
[12]Chang Y and Chang C.Laboratory results for the features of body-ware propagationin a transversely i-sotropic media.Expanded Abstracts of71st SEG Mtg,2001,1921~1924
[13]魏建新.正交各向异性介质波场特性的物理模拟研究[博士论文].北京:中国石油大学(北京),2003
[2]Ruger A.P-ware reflection coefficients for transverse-lyisotropic models with vertical and horizontal axis of symmetry.Geophysics,1997,62(3):713~721
[3]Ruger A.Variation of P-ware reflectivity with offset and azi muth in anisotropic media.Geophysics,1998,63(2):692~706
[4]Gray D,Head K.Fracture detection in Manderson field:A3-D AVAZ case history.The Leading Edge,2000,19(11):1214~1221
[5]乐绍东.AVA裂缝检测技术在川西J M构造的应用.天然气工业,2004,24(1):22~24
[6]郝守玲等.EDA介质的P波方位各向异性——物理模型的研究.石油地球物理勘探,1998,33(增刊2):54~62
[7]刘洋,董敏煜.各向异性介质中的方位AVO.石油地球物理勘探,1999,34(3):261~267
[8]李国发等.利用三维地震资料勘探纵波方位振幅随偏移距变化技术检测煤田裂缝.科学通报,2005,50(增刊I):138~142
[9]李磊.横向各向同性介质Thomsen近似公式的适用范围.石油物探,2008,47(2):117~122
[10]苏魏,陈树民等.各向异性介质弹性波场成像的Thomsen参数影响研究与分析.大庆石油地质与开发,2007,26(2):123~126
[11]Chang Y and Chang C.The line singularities of the body wares in anisotropic media:Physical modeling result.Expanded Abstracts of70th SEG Mtg,2000,2468~2471
[12]Chang Y and Chang C.Laboratory results for the features of body-ware propagationin a transversely i-sotropic media.Expanded Abstracts of71st SEG Mtg,2001,1921~1924
[13]魏建新.正交各向异性介质波场特性的物理模拟研究[博士论文].北京:中国石油大学(北京),2003
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