井间地震直达波和反射波走时联合层析反演
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摘要
提出一种井间地震直达波和反射波走时联合层析反演方法。建立了基于不规则单元的地层和界面完全耦合的三维井间离散模型,并在垂直于连井截面方向上假设模型参数不变;以直达波走时和反射波走时为观测数据,地层单元节点上的慢度和反射界面节点上的深度为模型参数,并考虑平滑约束和先验约束等,建立了线性迭代联合层析反演方程。理论模型合成资料和实测资料的应用结果表明,联合层析反演能同时发挥直达波和反射波各自的优势,不但可以确定反射界面,而且能提高地层速度的分辨率和可靠性。
A method for crosshole seismic tomographic inversion using combined direct and reflected traveltimes is proposed in this paper.The 3-D crosshole model is represented as a set of layers separated by the interfaces,across which the velocity may be discontinuous.Each layer is discretized by irregular hexahedral and/or tetrahedral cells and each interface is discretized by inclined planes,which are perpendicular to the crosshole section.The discrete layers couple entirely with the discrete interfaces.The model parameters are assumed to be constant in the direction vertical to the crosshole section.Both velocities at layer nodes and depths at interface nodes are simultaneously inverted using a combination of direct and reflected arrival data.The inversion process seeks a minimum-structure model that is able to explain the given traveltime data satisfactorily by inverting to minimize data misfit and model roughness norms simultaneously.The nonlinear traveltime inversion is achieved using an iterative linearized approach.The applications of this method to synthetic and real data demonstrate that the combined direct and reflected traveltime tomographic inversion can obtain more accurate medium velocity and interface depth with a higher resolution than the direct traveltime inversion.
A method for crosshole seismic tomographic inversion using combined direct and reflected traveltimes is proposed in this paper.The 3-D crosshole model is represented as a set of layers separated by the interfaces,across which the velocity may be discontinuous.Each layer is discretized by irregular hexahedral and/or tetrahedral cells and each interface is discretized by inclined planes,which are perpendicular to the crosshole section.The discrete layers couple entirely with the discrete interfaces.The model parameters are assumed to be constant in the direction vertical to the crosshole section.Both velocities at layer nodes and depths at interface nodes are simultaneously inverted using a combination of direct and reflected arrival data.The inversion process seeks a minimum-structure model that is able to explain the given traveltime data satisfactorily by inverting to minimize data misfit and model roughness norms simultaneously.The nonlinear traveltime inversion is achieved using an iterative linearized approach.The applications of this method to synthetic and real data demonstrate that the combined direct and reflected traveltime tomographic inversion can obtain more accurate medium velocity and interface depth with a higher resolution than the direct traveltime inversion.
引文
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[6]Bube K P,Langan R T.Resolution of slowness and reflectors incrosswell tomography with transmission and reflection traveltimes[J].Geophysics,2008,73(5):321-335.
[7]左建军,林松辉,孔庆丰,等.井间地震直达波和反射波联合层析成像及应用[J].石油地球物理勘探,2011,46(2):226-231.
[8]张建中,丁兴号.一种2.5维井间透射波层析成像方法[J].声学学报,2007,32(1):91-96.
[9]Huang Y Q,Zhang J Z,Liu Q H.Three-dimensional GPR raytracing based on wavefront expansion with irregular cells[J].IEEETransactions on Geoscience and Remote Sensing,2011,49(2):676-686.
[10]张建中,陈世军,徐初伟.动态网络最短路径射线追踪[J].地球物理学报,2004,47(5):899-904.
[2]Calnan C,Schuster G T.Reflection+transmission crosswelltomography[C].[s.l.]:59th Annual International Meeting,SEG,Expanded Abstracts,1989,8:908-911.
[3]Wu L,Song W,Zhang M.Seismic crosshole curved ray reflection&transmission tomography(CCRTT)[J].CT Theory and appli-cations,1994,3(1):42-47.
[4]Van Schaack M A.Velocity estimation for crosswell reflection ima-ging using combined direct and reflected arrival traveltime tomo-graphy[D].Ph.D.dissertation.USA:Stanford University:1997.
[5]Spetzler J.Finite-frequency wavefield theory for high-resolutionvelocity estimation using transmission and reflection data[C].[s.l.]:73th Annual International Meeting,SEG,Expanded Ab-stracts,2003,22:2315-2318.
[6]Bube K P,Langan R T.Resolution of slowness and reflectors incrosswell tomography with transmission and reflection traveltimes[J].Geophysics,2008,73(5):321-335.
[7]左建军,林松辉,孔庆丰,等.井间地震直达波和反射波联合层析成像及应用[J].石油地球物理勘探,2011,46(2):226-231.
[8]张建中,丁兴号.一种2.5维井间透射波层析成像方法[J].声学学报,2007,32(1):91-96.
[9]Huang Y Q,Zhang J Z,Liu Q H.Three-dimensional GPR raytracing based on wavefront expansion with irregular cells[J].IEEETransactions on Geoscience and Remote Sensing,2011,49(2):676-686.
[10]张建中,陈世军,徐初伟.动态网络最短路径射线追踪[J].地球物理学报,2004,47(5):899-904.
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