【摘要】 VSP资料钻前预测的关键在于高精度的波阻抗反演,本文针对VSP资料高分辨率、高信噪比以及能精确地分离出上、下行波的特点,提出了一种利用VSP资料进行井底以下钻头前方地层波阻抗反演的方法。该方法首先对VSP走廊叠加记录采用非线性迭代反演方法反演地下地层的波阻抗;通过在迭代过程中不断修改阻尼因子,以及引入预条件共轭梯度法求解方程组,增强了解的稳定性和收敛速度。理论模型与实际资料的处理结果表明该方法具有较好的效果,并在VSP资料钻前预测研究中具有良好的应用前景。更多还原

【Abstract】 Highly precise acoustic impedance inversion is a key technology for pre-drilling prediction by VSP data.In this paper,based on the facts that VSP data has high resolution, high signal to noise ratio,and the downgoing and upgoing waves can be accurately separated, we propose a method of predicting the impedance below the borehole in front of the bit using VSP data.First,the method of nonlinear iterative inversion is adopted to invert for impedance using the VSP corridor stack.Then,by modifying the damping factor in the iteration and using the preconditioned conjugate gradient method to solve the equations,the stability and convergence of the inversion results can be enhanced.The results of theoretical models and actual data demonstrate that the method is effective for pre-drilling prediction using VSP data.更多还原