井间地震层析成像分辨率研究
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摘要
通过大量数值模型试验 ,并根据射线密度、射线正交性和点扩散函数 ,对井间地震层析成像的分辨率问题进行了研究。结果表明 ,井间地震层析成像的分辨率在空间上是可能性变的 ,垂直方向的分辨率好于水平方向 ,而且高速异常体和低速异常体的图像形态和分辨率是非一致的。高速异常体波形CT的图像水平方向最小分辨率距离为 1/ 2波长 ,垂直分辨率最小分辨率距离为 3/ 10波长 ;而低速异常体的波形CT图像的水平方向的最小分辨率约为 2 / 5波长 ,垂向最小分辨率约 1/ 5个波长 ;走时CT的图像水平方向最小分辨率为 3个像元 ,垂直方向的最小分辨率距离为 2个像元 ;当井深与井间距之比为 2时 ,图像分辨率最高
Resolution in crosshole seismic tomography has been studied in this paper by means of ray density, ray orthogonality and point-spread function. Numerical experiments indicate that the resolution is better in the vertical direction than in the horizontal, and the high velocity anomalous body is different from the low velocity anomalous body in resolution and shapes of tomography. For the high velocity anomalous body, the spatial resolution of the waveform velocity tomogram in horizontal is about 1/2 of the wavelength, and that in vertical about 3/10 of the wavelength. For the low velocity anomalous body, the spatial resolution of the waveform velocity tomogram in horizontal is about 2/5 of the wavelength, and that in vertical about 1/5 of the wavelength. The spatial resolution of the traveltime velocity tomogram in horizontal is about three tomographic elements width, and that in horizontal about two tomographic elements width. When the ratio between the borehole depth and well offset is equal to 2.0, the spatial resolution of the velocity tomogram is the best.
Resolution in crosshole seismic tomography has been studied in this paper by means of ray density, ray orthogonality and point-spread function. Numerical experiments indicate that the resolution is better in the vertical direction than in the horizontal, and the high velocity anomalous body is different from the low velocity anomalous body in resolution and shapes of tomography. For the high velocity anomalous body, the spatial resolution of the waveform velocity tomogram in horizontal is about 1/2 of the wavelength, and that in vertical about 3/10 of the wavelength. For the low velocity anomalous body, the spatial resolution of the waveform velocity tomogram in horizontal is about 2/5 of the wavelength, and that in vertical about 1/5 of the wavelength. The spatial resolution of the traveltime velocity tomogram in horizontal is about three tomographic elements width, and that in horizontal about two tomographic elements width. When the ratio between the borehole depth and well offset is equal to 2.0, the spatial resolution of the velocity tomogram is the best.
引文
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[2] 陈国金.井间观测系统的讨论[J].石油物探,1996,35(3).
[3] 杨文采,杜剑渊.煤矿陷落柱地震层析成像试验[J].物探与化探,1992,16(3).
[4] 赵永贵,王超凡,陈燕民,等.地震CT在寻找隐伏铜镍矿中的应用[J].地球物理学报,1996,39(2).
[5] BackusG ,GilbertF .Theresolvingpowerofgrossearthdata[J].Geophys.J .R .Astr.Soc.,1968,16(1):169-205.
[6] HumphreysJT ,ClaytonRW .Adaptionofbackprojectiontomo graphytoseismictraveltimeproblems[J].J .G .R .,1988,93:1073-1085.
[7] RectorIIIJW ,WashbourneJK .Characterizationofresolutionanduniquenessincrosswelldirect-arrivaltraveltimetomographyusingtheFourierProjectionslicetheorem[J].Geophysics,1994,59(11):1642-1649.
[8] SchusterGT .Resolutionlimitsforcrosswellmigrationandtra-veltimetomographyGeophys[J].J .Int.,1996,127(2):427-440.
[9] WilliamsonPR ,WorthingtonMN .Aguidetothelimitsofre solutionimposedbyscatteringinraytomography[J].Geophy sics,1991,56(2):202-207.
[10] WilliamsonPR ,WorthingtonMH .Resolutionlimitsinraytomographyduetowavebehavior:Numericalexperiments[J].Geophysics,1993,58(5):727-735.
[11] 冯锐.西北地区的基地速度图像[J].地球物理学报,1991,34(4).
[12] WuRS ,ToksozMN .Diffractiontomographyandmultisourceholographyappliedtoseismicimaging[J].Geophysics,1987,52(1):11-25.
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