海上粘弹介质FCT有限差分正演模拟
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摘要
高阶有限差分正演模拟将时间和空间离散,以差分代替微分,其求解精度受子波主频、网格大小以及有限差分精度的影响,不当的话会引起数值频散。海上勘探采用的气枪震源子波频带较宽,主频高,波长短,数值频散现象严重,而减小空间网格大小和提高有限差分精度需要较大的计算量和较长的计算时间。针对这一特点,采用通量校正传输(FCT)技术与有限差分相结合的方法来减少数值频散。在分析气枪震源子波的特征及该子波在粘弹介质中传播频谱特征的基础上,采用FCT有限差分模拟对粘弹介质盐丘模型进行了正演模拟。结果表明,FCT有限差分能够有效地压制数值频散,可以提高模拟的精度和运算效率。
High-order finite difference forward modeling method dispersed time and space through difference instead of differential.Its accuracy was influenced by dominant frequency,grid size and the accuracy of finite difference,which would cause numerical dispersion if they were improperly processed.The air gun wavelet with large frequency bandwidth,high key frequency and short wavelet length used in exploration in offshore oilfield would cause serious numerical dispersion.However,reducing the space grid size and improving the accuracy of the finite difference needed longer computing time.In consideration of the above situation,finite difference method with the FCT(flux correction transport) was used to reduce numerical dispersion.On the basis of analyzing the characteristics of the air gun wavelet and the frequency characteristics that propagated in the visco-elastic media,the method was used for the forward modeling in the salt dome model.The result shows that FCT can effectively suppress numerical dispersion,improve the precision of simulation and operation efficiency.
High-order finite difference forward modeling method dispersed time and space through difference instead of differential.Its accuracy was influenced by dominant frequency,grid size and the accuracy of finite difference,which would cause numerical dispersion if they were improperly processed.The air gun wavelet with large frequency bandwidth,high key frequency and short wavelet length used in exploration in offshore oilfield would cause serious numerical dispersion.However,reducing the space grid size and improving the accuracy of the finite difference needed longer computing time.In consideration of the above situation,finite difference method with the FCT(flux correction transport) was used to reduce numerical dispersion.On the basis of analyzing the characteristics of the air gun wavelet and the frequency characteristics that propagated in the visco-elastic media,the method was used for the forward modeling in the salt dome model.The result shows that FCT can effectively suppress numerical dispersion,improve the precision of simulation and operation efficiency.
引文
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[2]裴正林,牟永光.非均匀介质地震波传播交错网格高阶有限差分法模拟[J].石油大学学报(自然科学版),2003,27(16):17～21.
[3]成景旺,顾汉明,徐照营.实际地层条件下爆炸震源子波模拟研究[J].工程地球物理学报,2009,6(5):529～534.
[4]Boris J P,Book D L.Flux-corrected transport I.SHASTA,a fluid transport algorithm that works[J].Journal of ComputationalPhysics-Special Issue:Commenoration of the 30th Anniversary,1997,135(2):172～186.
[5]潘海滨,孙萍.交错网格波场数值模拟频散分析与校正策略[J].海洋地质动态,2009,25(6):36～41.
[6]潘海滨.交错网格地震波场模拟及频散校正策略[J].物探化探计算技术,2009,31(2):369～373.
[7]王琚,杨长春,冯英杰.用优化通量校正传输技术压制数值模拟的频散[J].勘探地球物理进展,2007,30(4):252～256.
[8]杨宁.FCT最佳差分法在正演模拟中的应用[D].成都:成都理工大学,2008.
[9]Tal-Ezer H,Carcione J M,Kosloff D.An accurate and efficient scheme for wave propagation in linear viscoelastic media[J].Geo-physics,1990,55(8):1366～1379.
[10]Robertsson J O,Blanch J O,Symes W W.Viscoelastic finite-difference modeling[J].Geophysics,1994,59(9):1444～1456.
[11]袁恩辉,顾汉明.基于小波域从叠前地震数据提取地层品质因子Q[J].工程地球物理学报,2010,7(2):190～196.
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