各向异性薄煤层纵波AVAZ分析
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摘要
通过建立HTI型薄煤层的传播矩阵,推导了水平界面情况下含各向异性薄煤层反射系数精确计算公式,并利用该公式对含有薄HTI型各向异性煤层进行了纵波AVAZ分析。经过研究发现,当HTI型煤层为薄层时(厚度小于地震波长的1/4时),其纵波反射系数与煤层为厚层时(厚度大于地震波长)顶板的纵波反射系数规律相似,但其值不仅与上下层介质物性参数有关,还与厚度有关,可见煤层为薄层时采用经典公式反演会带来误差;薄层厚度、Thomsen等效各向异性参数和裂缝密度对纵波反射系数有较大影响,裂缝纵横比对反射系数影响较小。入射波方位角为90°时,入射波在HTI介质各向同性面,此时各向异性参数对反射系数影响最小。
By build the propagator matrix of HTI thin coal bed,we deduced the exact P-wave reflectivity equation of anisotropic thin coal bed with horizontal layers. AVAZ Analysis was made to study the reflectivity response of the HTI thin coal bed. The variations of P-wave reflectivity with incidence and azimuth angle were made for HTI thin coal bed case( layer thickness less than a quarter of seismic wavelength) and thick coal seam case( layer thickness larger than seismic wavelength). The tendency was similar but the values were different. The reflection coefficients of P wave are depending not only on physical property of the upper and lower layers,but also on the layer thickness. This indicated that applying classical equations to perform inversion for thin coal bed case was not accurate. Our study showed that layer thickness( of the thin coal bed),effective Thomsen's anisotropic parameters for HTI and crack density had great influence on the P-wave reflectivity,while the aspect ratio of cracks changed the reflectivity tiny. When the azimuth angle was 90 degrees,the reflectivity seemed no longer affected by anisotropic parameters. This was mainly because the incidence wave was parallel to the isotropic plane of the HTI media.
By build the propagator matrix of HTI thin coal bed,we deduced the exact P-wave reflectivity equation of anisotropic thin coal bed with horizontal layers. AVAZ Analysis was made to study the reflectivity response of the HTI thin coal bed. The variations of P-wave reflectivity with incidence and azimuth angle were made for HTI thin coal bed case( layer thickness less than a quarter of seismic wavelength) and thick coal seam case( layer thickness larger than seismic wavelength). The tendency was similar but the values were different. The reflection coefficients of P wave are depending not only on physical property of the upper and lower layers,but also on the layer thickness. This indicated that applying classical equations to perform inversion for thin coal bed case was not accurate. Our study showed that layer thickness( of the thin coal bed),effective Thomsen's anisotropic parameters for HTI and crack density had great influence on the P-wave reflectivity,while the aspect ratio of cracks changed the reflectivity tiny. When the azimuth angle was 90 degrees,the reflectivity seemed no longer affected by anisotropic parameters. This was mainly because the incidence wave was parallel to the isotropic plane of the HTI media.
引文
[1]彭苏萍,杜文凤,殷裁云,等.基于AVO反演技术的煤层含气量预测[J].煤炭学报,2014,39(9):1792-1796.Peng Suping,Du Wenfeng,Yin Caiyun,et al.Coal-bed gas content prediction based on AVO inversion[J].Journal of China Coal Society,2014,39(9):1792-1796.
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[7]Ruger A.Variation of P-wave reflectivity with offset and azimuth in anisotropic media[J].Geophysics,1998,63(3):935-947.
[8]Liu Y,Schmitt D R.Amplitude and AVO responses of a single thin bed[J].Geophysics,2003,68(4):1161-1168.
[9]张铁强,孙鹏远,钱忠平,等.薄煤层AVO响应特征分析[J].石油地球物理勘探,2013,48(4):597-603.Zhang Tieqiang,Sun Pengyuan,Qian Zhongping,et al.AVO analysis on thin coalbed[J].Oil Geophysical Prospecting,2013,48(4):597-603.
[10]赵伟,陈小宏,李景叶.薄互层调谐效应对AVO的影响[J].石油物探,2006,45(6):570-573.Zhao Wei,Chen Xiaohong,Li Jingye.Analysis of impact of thin interbed tuning effect on AVO[J].Geophysical Prospecting for Petroleum,2006,45(6):570-573.
[11]邓小娟,彭苏萍,林庆西,等.基于各向异性的薄煤层AVO正演方法[J].煤炭学报,2010,35(12):2053-2058.Deng Xiaojuan,Peng Suping,Lin Qingxi,et al.AVO forward method of anisotropic thin coalbed[J].Journal of China Coal Society,2010,35(12):2053-2058.
[12]邓小娟,彭苏萍,杜文凤,等.薄煤层P-SV转换波AVO正演研究[J].煤炭学报,2012,37(1):62-66.Deng Xiaojuan,Peng Suping,Du Wenfeng,et al.Converted wave AVO forward method of P-SV thin coal bed[J].Journal of China Coal Society,2012,37(1):62-66.
[13]Tsvankin I.Reflection moveout and parameter estimation for horizontal transverse isotropy[J].Geophysics,1997,62(2):614-629.
[14]Hudson J A.Overall elastic properties of isotropic materials with arbitrary distribution of circular cracks[J].Geophys.J.Int.,1990,102:465-469.
[2]Yiwen Ju,Kray Luxbacher,Xiaoshi Li,et al.Micro-structural evolution and their effects on physical properties in different types of tectonically deformed coals[J].International Journal of Coal Science&Technology 2014,1(3):264-275.
[3]陈同俊,王新,崔若飞.基于方位AVO正演的HTI构造煤裂隙可探测性分析[J].煤炭学报,2010,35(4):640-644.Chen Tongjun,Wang Xin,Cui Ruofei.The detectability analysis on HTI tectonic coal cracks by azimuthal AVO’s forward modeling[J].Journal of China Coal Society,2010,35(4):640-644.
[4]崔大尉,王远,于景邨.利用AVO属性研究构造煤的分布规律[J].煤炭学报,2013,38(10):1842-1849.Cui Dawei,Wang Yuan,Yu Jingcun.Study on the distribution of deformed coal with AVO attributes[J].Journal of China Coal Society,2013,38(10):1842-1849.
[5]崔大尉,秦轲,于景邨.利用地震P波方位/角度信息预测煤层裂隙发育—以阳泉矿区为例[J].地球物理学进展,2015,30(2):858-866.Cui Dawei,Qin Ke,Yu Jingcun.Predicting coal fractures with seismic P-wave azimuth/incident angle information:Taking the Yangquan mining areas an example[J].Progress in Geophysics,2015,30(2):858-866.
[6]常锁亮,杨起,刘大锰,等.煤层气储层物性预测的AVO技术对地震纵波资料品质要求的探讨[J].地球物理学进展,2008,23(4):1236-1243.Chang Suoliang,Yang Qi,Liu Dameng,et al.The discussion of required P-wave quality for the AVO technology based on the CBM reservoir research[J].Progress in Geophysics,2008,23(4):1236-1243.
[7]Ruger A.Variation of P-wave reflectivity with offset and azimuth in anisotropic media[J].Geophysics,1998,63(3):935-947.
[8]Liu Y,Schmitt D R.Amplitude and AVO responses of a single thin bed[J].Geophysics,2003,68(4):1161-1168.
[9]张铁强,孙鹏远,钱忠平,等.薄煤层AVO响应特征分析[J].石油地球物理勘探,2013,48(4):597-603.Zhang Tieqiang,Sun Pengyuan,Qian Zhongping,et al.AVO analysis on thin coalbed[J].Oil Geophysical Prospecting,2013,48(4):597-603.
[10]赵伟,陈小宏,李景叶.薄互层调谐效应对AVO的影响[J].石油物探,2006,45(6):570-573.Zhao Wei,Chen Xiaohong,Li Jingye.Analysis of impact of thin interbed tuning effect on AVO[J].Geophysical Prospecting for Petroleum,2006,45(6):570-573.
[11]邓小娟,彭苏萍,林庆西,等.基于各向异性的薄煤层AVO正演方法[J].煤炭学报,2010,35(12):2053-2058.Deng Xiaojuan,Peng Suping,Lin Qingxi,et al.AVO forward method of anisotropic thin coalbed[J].Journal of China Coal Society,2010,35(12):2053-2058.
[12]邓小娟,彭苏萍,杜文凤,等.薄煤层P-SV转换波AVO正演研究[J].煤炭学报,2012,37(1):62-66.Deng Xiaojuan,Peng Suping,Du Wenfeng,et al.Converted wave AVO forward method of P-SV thin coal bed[J].Journal of China Coal Society,2012,37(1):62-66.
[13]Tsvankin I.Reflection moveout and parameter estimation for horizontal transverse isotropy[J].Geophysics,1997,62(2):614-629.
[14]Hudson J A.Overall elastic properties of isotropic materials with arbitrary distribution of circular cracks[J].Geophys.J.Int.,1990,102:465-469.