利用井孔偶极弯曲波反演横向各向同性孔隙地层渗透率的研究

Study on inversion of permeability for transversely isotropic porous media by dipole fiexural waves in a borehole

对利用井孔偶极弯曲波衰减特性反演横向各向同性孔隙地层的纵、横向渗透率进行了理论方法和数值研究。对软地层,在方差函数极值行为分析的基础上,用最小二乘反演对多组理论模拟数据进行处理,得到的纵、横向渗透率精度都比较高,这与软地层弯曲波衰减对纵向渗透率的敏感程度明显比硬地层高有关;用添加不同强度的随机噪声综合反映现场资料可能带来的误差,对多道间提取的衰减叠加求平均可明显的抵消噪声的影响;对快速孔隙地层偶极声测井理论模拟数据也尝试性地进行了纵、横向渗透率反演,发现,虽然硬地层弯曲波的衰减对纵向渗透率很不敏感,但纵向渗透率的取值偏离真值却对横向渗透率的反演结果有明显影响。

The theoretical method and numerical study which inverses the vertical and horizontal permeability of the transversely isotropic porous media has been done in this paper by using the attenuation character of dipole flexural waves in a borehole. For the slow formation, based on behavior analysis of the variance function, the precision of vertical and horizontal permeability is relatively high which is calculated to groups of theoretical simulation data by least squares method, this is related to the sensitivity of horizontal permeability to the attenuation of slow formation is more than which of fast formation. Though the random noise of different intensity is added to simulate the error of the actual data of well logging, the influence of noise still can be offset by superposition averaging of the attenuations which is calculated from multi-channel. For the fast formation, the vertical and horizontal permeability has been also attempted to inverse by the theoretical simulation data. It is also found that although the vertical permeability of fast porous formation is hardly sensitive, the result of horizontal permeability will be impacted if the value of vertical permeability is much more different from the real value.