各向异性地层中电阻率测井的响应特征

The response characteristic of resistivity log in anisotropic formations

应用模式匹配算法研究了斜井眼中普通电阻车测井的快速正演模拟方法，系统地考察了井眼倾角、地层厚度以及地层的各向异性等对普通电阻车测井的影响。数值模拟结果证明：①在斜井眼中，各向异性地层和各向同性地层在响应特征上存在着很大差异。对于厚度足够大的地层，井眼或地层倾角的变化对各向同性地层的视电阻率几乎没有影响（其影响是由地层视厚度的变化引起的），但对各向异性地层的视电阻车影响很大。②并眼或地层倾角的增加改变了地层的视厚度，对厚度小于测井仪器纵向分辨率的薄储层的视电阻率产生明显影响。③当薄交互层中各个地层的单层厚度大大小于测井仪器的纵向分辨率时，其上的响应与各向异性地层的响应完全相同。因此，利用各向异性地层上现电阻率随井眼倾角变化的特征，可以从斜井眼的视电阻率测井曲线中识别出各向异性地层。此外，文中还进一步研究了水平层状各向异性地层中倒向和微球型聚焦测井响应特征的差异，以及应用两者的差异识别和划分各向异性地层的方法。

The fast simulation of normal resistivity log in deviated borehole is studied by using pattern-matched method. The influence of borehole dipping angle, stratum thickness and stratigraphic anisotropy upon normal resistivity log are examined systematically. Numerical modeling results show the following essential points:Under deviated borehole circumstances, response characteristics in anisotropic formation is much different from that in isotropic formation. For the stratum that is thick enough, dipping angle variation of borehole or stratum has almost no influence upon the apparent resistivity of isotropic formation (the influence resulting from apparent thickness variation of stratum), but it has great influence upon the apparent resistivity of anisotropic formation. The increase of borehole (or stratum ) dipping angle changes apparent stratum thickness, so it brings obvious influence upon the apparent resistivity of a thinreservoir whose thickness is lower than the vertical resolution of a logger. When the thickness of a single stratum in interbedding series is much lower than the vertical resolutlon of a logger, the response is fully similar to that of anisotropic formation. Havlng Known how the apparent resistivity of anisotropic formation varies with the dipping angle of deviated borehole, people can identify anisotropic formation from the apparent reslstivity logging curve that was taken in deviated borehole.Furthermore, authors analyse the response characteristic differences between Laterolog and MSFL in horizontally-layered anisotropic formation, and give the method for us to identify anisotropic formation by using the difference.