随钻电磁波电阻率测井曲线分离关系研究

Study on Relationships of the Separated Curves in Resistivity Logging While Drilling

随钻电磁波电阻率测井仪器受围岩、相对介电常数、泥浆侵入、电阻率各向异性等不同因素影响时,多条电阻率测量曲线之间会呈现复杂的分离关系。文章采取数值计算的方法,模拟各种环境因素对随钻电阻率曲线分离关系的影响。研究表明,围岩影响使目的层电阻率曲线值降低,对幅度比电阻率的影响大于相位差电阻率;介电参数的影响使幅度比电阻率大于相位差电阻率;低阻泥浆侵入的影响使长源距测量值大于短源距测量值;在电阻率各向异性地层中,随着相对倾角的增大,相位差电阻率大于幅度衰减电阻率。不同的影响因素会导致电阻率曲线出现不同的分离次序,根据曲线分离规律,可定性分析仪器测量时受到的具体影响因素,对仪器环境校正和随钻地层评价有指导意义。

The curves of resistivity logging while drilling（LWD） present complex separation relationship when the tool is ＇affected by environ- mental factors such as surrounding rock resistivity, dielectric constant, mud invasion, resistivity anisotropy etc. This paper uses the numeri- cal simulation to investigate the influence of environmental factors on the curves separation relationship. The result shows the effect of shoul- der bed leads to the target resistivity measurement values lower, phase difference resistivity is impacted greater than attenuation resistivity; and the effect of the dielectric constant makes measurement result of attenuation resistivity higher than that of phase difference resistivity; Meanwhile, mud invasion also affects the measurement making the long spacing values higher than the short spacing values; in addition, with the relative dip increasing in the resistivity anisotropic formation, phase difference values will increase which is higher than amplitude attenuation values. In conclusion, these factors lead to the separation phenomenon of curves, the rank of which is based on the factors. U- sing the separation regularities, which is presented in this paper, the specific factors affecting the measurement can be qualitatively ana- lyzed, as has instructive significance to the measurement environmental correction and LWD formation evaluation.