基于方位AVO正演的HTI构造煤裂隙可探测性分析
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摘要
通过建立6类HTI构造煤的理论模型,利用Hudson等效介质理论和Schoenberg所定义的传播矩阵,正演煤层顶板的方位AVO记录,最终获得了6类模型的多方位AVO记录。通过对HTI构造煤方位AVO曲线的分析可知:①不同方位AVO曲线的P值为小于零的常量,G值较大并随方位角φ的增大而减小(φ[0,90°]);②当裂隙密度增大时,P值减小,G值增大;③相对于泥岩顶板来说,砂岩顶板的P值较小,G值较大。通过对HTI构造煤GVAz曲线的分析可知:①GVAz曲线的周期为180°,并在裂隙法向方位取最小值;②随着裂隙密度的增大,GVAz曲线的波幅相应增大;③当裂隙水填充时,GVAz曲线的波幅大于裂隙气填充时的情形。因此,方位AVO的P值可以被用来识别煤层的顶板岩性,GVAz曲线的极值和波幅可分别用来获得裂隙发育法向和裂隙密度信息。就实际地震数据来说,较高信噪比(>5)是进行方位AVO分析的前提。
Established six kinds of HTI (Transverse Isotropy with a Horizontal Axis) coal models,Hudson’s effective media theory and Schoenberg’s propagation matrix were used to calculate azimuthal AVO (Amplitude Variation with Offset) records.And finally,the azimuthal AVO records according to the six kinds of models were achieved.By analyzing azimuthal AVO curves,it is easy to conclude that:① The P values are less than zero and not variation with azimuthal,the G values are positive and decrease with the increase of azimuth (φ [0,90°]);② With the increasing of crack density,the P values decrease and the G values increase;③ Relative to the mudstone roof,P values of sandstone roof are smaller and G values of sandstone roof are lager.By the GVAz (Gradient Variation with Azimuth) curves’ analysis,the following conclusions can be made:① GVAz curves’ period is 180°,and they get their minimum at crack’s normal direction;② With the increasing of crack’s density,the amplitudes of GVAz curves increase correspondingly;③ When cracks filled with brine,the GVAz curves have larger fluctuation range than the situation of gas infilling.Therefore,P values of azimuthal AVO curves can be used to detect coal roof’s lithology and GVAz curve’s minimum and amplitude could give the information of crack’s normal direction and density respectively.As for the practical seismic data,higher signal to noise ratio (greater than five) is a precondition of azimuthal AVO analyzing.
Established six kinds of HTI (Transverse Isotropy with a Horizontal Axis) coal models,Hudson’s effective media theory and Schoenberg’s propagation matrix were used to calculate azimuthal AVO (Amplitude Variation with Offset) records.And finally,the azimuthal AVO records according to the six kinds of models were achieved.By analyzing azimuthal AVO curves,it is easy to conclude that:① The P values are less than zero and not variation with azimuthal,the G values are positive and decrease with the increase of azimuth (φ [0,90°]);② With the increasing of crack density,the P values decrease and the G values increase;③ Relative to the mudstone roof,P values of sandstone roof are smaller and G values of sandstone roof are lager.By the GVAz (Gradient Variation with Azimuth) curves’ analysis,the following conclusions can be made:① GVAz curves’ period is 180°,and they get their minimum at crack’s normal direction;② With the increasing of crack’s density,the amplitudes of GVAz curves increase correspondingly;③ When cracks filled with brine,the GVAz curves have larger fluctuation range than the situation of gas infilling.Therefore,P values of azimuthal AVO curves can be used to detect coal roof’s lithology and GVAz curve’s minimum and amplitude could give the information of crack’s normal direction and density respectively.As for the practical seismic data,higher signal to noise ratio (greater than five) is a precondition of azimuthal AVO analyzing.
引文
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[13]张爱敏,汪洋,赵世尊.不同厚度煤层AVO特征及模型研究[J].中国矿业大学学报,1997,26(3):36-41.Zhang Aimin,Wang Yang,Zhao Shizun.AVO character and its modeling research for different thickness coal bed[J].Journal of China University of Mining and Techonology,1997,26(3):36-41.
[14]Dong Shouhua,Yue Jianhua.Forward modeling of the relationship between reflection coefficient and incident angle of the P-wave in a coal-seam[J].Journal of China University of Mining and Technolo-gy,2006,16(1):5-8.
[15]彭苏萍,高云峰,杨瑞召,等.AVO探测煤层瓦斯富集的理论探讨和初步实践——以淮南煤田为例[J].地球物理学报,2005,48(6):1475-1486.Peng Suping,Gao Yunfeng,Yang Ruizhao,et al.Theory and appli-cation of AVO for detection of coal bed methane:a case from the Huainan coalfield[J].Journal of Chinese Geophysics,2005,48(6):1475-1486.
[16]Hilterman Fred J.Seismic amplitude interpretation[M].Seg&Ea-ga,Houston,2001.
[17]陈同俊.P波方位AVO理论及煤层裂隙探测技术[D].徐州:中国矿业大学,2009.Chen Tongjun.Theory on P-wave azimuthal AVO and detecting technique of coal bed cracks[D].Xuzhou:China University of Mining and Techonology,2009.
[18]Castagna J P,Swan HW.Principles of AVO crossplotting[J].The Leading Edge,1997,16(4):337-342.
[19]陈同俊,崔若飞,刘恩儒.VTI型构造煤AVO正演模拟[J].煤炭学报,2009,34(4):438-442.Chen Tongjun,Cui Ruofei,Liu Enru.AVO forward modeling for VTI coal[J].Journal of China Coal Society,2009,34(4):438-442.
[2]俞启香.矿井瓦斯防治[M].徐州:中国矿业大学出版社,1993.Yu Qixiang.The prevention and control for mine gas[M].Xuzhou:China University of Mining and Technology Press,1993.
[3]张玉贵,张子敏,曹运兴.构造煤结构与瓦斯突出[J].煤炭学报,2007,32(3):281-284.Zhang Yugui,Zhang Zimin,Cao Yunxing.Deformed-coal structure and control to coal-gas outburst[J].Journal of China Coal Society,2007,32(3):281-284.
[4]Wei Chen.AVO in azimuthally anisotropy media fracture detection using P-wave data and a seismic study of naturally fractured tight gas reservoirs[D].California:Stanford University,1995.
[5]Chen T,Cui R.P-wave AVO and AVAZ modeling for coal beds[A].Proceedings of2008Asia Pacific CBM symposium[C].Bris-bane Australia,2008:48.
[6]Hudson J A.Wave speeds and attenuation of elastic waves in materi-al containing cracks[J].Geophys.J.Int.,1981,64(1):133-150.
[7]Hudson J A.Seismic wave propagation through material containing partially saturated cracks[J].Geophys.J.Int.,1988,92(1):33-37.
[8]Hudson J A,Liu E,Crampin S.The mechanical properties of materi-als with interconnected cracks and pores[J].Geophys.J.int.,1996,124(1):105-112.
[9]Tsvankin I.Seismic signatures and analysis of reflection data in ani-sotropic media[M].Elsevier,Amsterdam,2005.
[10]Schoenberg M,Prot偄zio J.Zoeppritz’s rationalized and generalized to anisotropy[J].J.Seismic Expl.,1992,1(1):125-144.
[11]琚宜文,姜波.构造煤结构及储层物性[M].徐州:中国矿业大学出版社,2005.Ju Yiwen,Jiang Bo.Structures of tectonic coal and its physicalcharacters[M].Xuzhou:China University of Mining and Technolo-gy Press,2005.
[12]琚宜文,姜波,侯泉林,等.构造煤结构-成因新分类及其地质意义[J].煤炭学报,2004,29(5):513-517.Ju Yiwen,Jiang Bo,Hou Quanlin,et al.The new structure-genetic classification system in tectonically deformed coals and its geolog-ical significance[J].Journal of China Coal Society,2004,29(5):513-517.
[13]张爱敏,汪洋,赵世尊.不同厚度煤层AVO特征及模型研究[J].中国矿业大学学报,1997,26(3):36-41.Zhang Aimin,Wang Yang,Zhao Shizun.AVO character and its modeling research for different thickness coal bed[J].Journal of China University of Mining and Techonology,1997,26(3):36-41.
[14]Dong Shouhua,Yue Jianhua.Forward modeling of the relationship between reflection coefficient and incident angle of the P-wave in a coal-seam[J].Journal of China University of Mining and Technolo-gy,2006,16(1):5-8.
[15]彭苏萍,高云峰,杨瑞召,等.AVO探测煤层瓦斯富集的理论探讨和初步实践——以淮南煤田为例[J].地球物理学报,2005,48(6):1475-1486.Peng Suping,Gao Yunfeng,Yang Ruizhao,et al.Theory and appli-cation of AVO for detection of coal bed methane:a case from the Huainan coalfield[J].Journal of Chinese Geophysics,2005,48(6):1475-1486.
[16]Hilterman Fred J.Seismic amplitude interpretation[M].Seg&Ea-ga,Houston,2001.
[17]陈同俊.P波方位AVO理论及煤层裂隙探测技术[D].徐州:中国矿业大学,2009.Chen Tongjun.Theory on P-wave azimuthal AVO and detecting technique of coal bed cracks[D].Xuzhou:China University of Mining and Techonology,2009.
[18]Castagna J P,Swan HW.Principles of AVO crossplotting[J].The Leading Edge,1997,16(4):337-342.
[19]陈同俊,崔若飞,刘恩儒.VTI型构造煤AVO正演模拟[J].煤炭学报,2009,34(4):438-442.Chen Tongjun,Cui Ruofei,Liu Enru.AVO forward modeling for VTI coal[J].Journal of China Coal Society,2009,34(4):438-442.
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