反射声波成像测井的有限元模拟

Numerical simulation of borehole acoustic-reflection imaging using the finite element method

应用有限元法对新兴的反射声波成像测井进行了数值模拟研究,计算了井旁附近存在不同倾角声阻抗不连续界面对声波的反射,使用的井内激励源为幅度加权相控线阵声波辐射器。从计算出的声全波波形上可以清楚地看到沿井壁传播的折射波和来自井旁界面的反射纵波。应用偏移叠加等数据处理技术对数值模拟波形进行了处理,从偏移剖面上反演出的反射界面的尺寸、位置和倾角等几何特性与数值模拟输入参数基本一致。

The numerical simulation of borehole acoustic reflection imaging is conducted using the finite element method (FEM). The reflection from varied dip of the acoustic discontinuity is calculated. The downhole source used is a linear phased array transmitter. It is clear on the calculated waveforms that there are refracted waves which propagate along the borehole sidewall as well as reflected waves which are reflected by the interface near-borehole. The technique of migration stack is applied to process the calculated waveforms to image the near-borehole reflecting interface. The geometrical properties of the interface, such as its dip, location and dimension, can be determined from the image and are found to be in good agreement with the input parameters in numerical simulation.