全方位P波属性裂缝检测方法
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摘要
本 文总结了国外利用P波振幅和速度进行裂缝检测的方法原理，其本质是利用P波振幅和速度随 方位角的周期变化估算裂缝的方位和密度。但上述方法各有利弊，振幅随方位角变化法(RVA )能够反映薄层特征，但受噪声的影响较大，有时不稳定；速度随方位角变化法(VVA)比较稳 定，但只能识别大套储层，对于识别薄储层的分辨率不够。鉴于此因，文中提出了波阻抗随 方位变化(IPVA)检测裂缝的新方法，其理论依据是“在各向异性介质中，速度是方位角的余 弦函数，波阻抗(IP)也必然是方位角的余弦函数。”文中结合罗家地区的泥岩裂隙地震地质 特征，设计了10线256炮块状砖墙式全方位三维观测系统；在三维资料的保真、保幅和地表一致性处理的基础上，对原有的64次覆盖的CMP道集进行扩大面元，形成了512次超CMP道集 ；分别对9个方位角进行了速度分析、NMO校正、振幅标定、方位AVO叠加、方位波阻抗反演 、VVA(RVA)及IPVA裂缝属性分析。应用效果表明，IPVA法与RVA(VVA)法相比，得到的解的稳 定性和分辨率都较高。
The paper summed up the principle or method for using P wave amplit ude and velocity to detect fracture.The characters are to use periodic v ariance of P-wave amplitude and velocity with azimuth to evaluate the direction and density of frac ture.But above mentioned methods have advantages and disadvantages respective ly.RVA(Reflection amplitude Variation with Azimuth) can reflect thin layer char acter but affected by noises seriously;VVA(Velocity Variation with Azimuth) is stable but only can identity a large suite of reservoir and has inaccurate resolution for identifying thin reservoir.Because of that,the paper presented a new method for using Impedance Variat ion with Azimuth(IPVA) to detect fracture.Th e basis of principle is “Because of velocity being a cosine func tion of azimuth in anisotropic medium, the impedance is certainly a cosine funct ion of azimuth”. Combining with seismic geologic character of fractured shale in Luojia area,the full azimuth 3D geometry with brick style in piec e(10 lines,256 shots) is designed in the pa per;on the basis of processing of high fidelity,amplitude and surface consist ence for 3D data,the super CMP gathers with 512 fold have been formed after enla rging bin to original CMP gathers with 64 fold;velocity analysis,NMO correction, amplitude labeling,azimuth AVO stack,azimuth impedance inversion,VVA(RVA) and an alysis of IPVA fracture attribution are conducted to 9 azimuth gathers respectiv ely.Application results shows that the IPVA has stable solution and high resolut ion comparing with RVA(VVA).
The paper summed up the principle or method for using P wave amplit ude and velocity to detect fracture.The characters are to use periodic v ariance of P-wave amplitude and velocity with azimuth to evaluate the direction and density of frac ture.But above mentioned methods have advantages and disadvantages respective ly.RVA(Reflection amplitude Variation with Azimuth) can reflect thin layer char acter but affected by noises seriously;VVA(Velocity Variation with Azimuth) is stable but only can identity a large suite of reservoir and has inaccurate resolution for identifying thin reservoir.Because of that,the paper presented a new method for using Impedance Variat ion with Azimuth(IPVA) to detect fracture.Th e basis of principle is “Because of velocity being a cosine func tion of azimuth in anisotropic medium, the impedance is certainly a cosine funct ion of azimuth”. Combining with seismic geologic character of fractured shale in Luojia area,the full azimuth 3D geometry with brick style in piec e(10 lines,256 shots) is designed in the pa per;on the basis of processing of high fidelity,amplitude and surface consist ence for 3D data,the super CMP gathers with 512 fold have been formed after enla rging bin to original CMP gathers with 64 fold;velocity analysis,NMO correction, amplitude labeling,azimuth AVO stack,azimuth impedance inversion,VVA(RVA) and an alysis of IPVA fracture attribution are conducted to 9 azimuth gathers respectiv ely.Application results shows that the IPVA has stable solution and high resolut ion comparing with RVA(VVA).
引文
[1]Alford R M.Shear data in the presence of azimuthal anisotr opy.Expanded Abstracts of 56th SEG Mtg,1986,476-479
[2]Mallick S and Frazer L N.Reflection/Transmission coefficie nts and azimuthal anisotropy in marine seismic studies.Geophys J Int,1991,105:24 1-252
[3]Craft K L,Mallick S,Meister L J and Van Dok R.Azimuthal an isot ropy analysis from P wave seismic traveltime data.Expanded Abstracts of 67th S EG Mtg,1997,1214-1217
[4]刘起弘译.利用纵波地震资料确定方位各向异性的主方向.山地地震 勘探,1998,22(1)
[2]Mallick S and Frazer L N.Reflection/Transmission coefficie nts and azimuthal anisotropy in marine seismic studies.Geophys J Int,1991,105:24 1-252
[3]Craft K L,Mallick S,Meister L J and Van Dok R.Azimuthal an isot ropy analysis from P wave seismic traveltime data.Expanded Abstracts of 67th S EG Mtg,1997,1214-1217
[4]刘起弘译.利用纵波地震资料确定方位各向异性的主方向.山地地震 勘探,1998,22(1)
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