转换波方位各向异性裂缝检测技术研究及应用

Research and application of fracture detection technique using azimuthal anisotropy of C-wave

HTI裂缝各向异性介质中,转换波随方位角的变化比较复杂,目前还没有解析公式可以表达其变化特征,只能通过物理实验或数值模拟来分析其应用的可能性.数值模拟结果表明,转换波在裂缝各向异性介质中传播时,其R分量和T分量的振幅属性都具有明显的方位各向异性特征,R分量振幅方位各向异性拟合椭圆的长轴方向指示裂缝方位,这与纵波方位各向异性特征相似;根据P波AVAZ方位各向异性分析原理,对转换波R分量振幅方位各向异性曲线进行方位椭圆拟合,寻找椭圆的长轴方向,即裂缝主方位,再由P波AVAZ技术中振幅响应与炮检方向和裂缝走向之间的夹角关系式得到裂缝的发育密度,从而构建转换波方位各向异性AVAZ裂缝检测技术.该技术已用于川西新场气田某区块的裂缝储层预测,取得了较好的应用效果.

The character of converted waves＇ amplitude versus azimuth is too complex to express it by exact formula,thus we can only analysis the feasibility of applying the Azimuthal Anisotropy of C-wave to detect stratum Fracture by physical experiments and numerical modeling.The results of numerical simulation indicate that,R and T components＇ amplitudes show clear azimuthal anisotropic character when the converted waves propage in the fractured anisotropic media.The direction of long axis of Polarized ellipse is related with the fracture orientation which is same as that of P wave＇s anisotropic character.Based on the theory of P wave AVAZ technique,we fitted the curve of converted waves＇ amplitude versus azimuthal angle,found the direction of long axis of Polarized ellipse,and determined the fracture orientation,then applying the function of P wave AVAZ function to calculate the fracture density,thus formed the converted wave AVAZ fracture detection technique.This technique has been applied to 3D3C converted wave data from Xinchang reservoir of the Sichuan Basin in the southwest of China,and obtained robust achievements in reservoir fracture detection.