随钻方位电阻率测井电磁响应的研究

发布时间：2019-03-25 18:16

【摘要】：在石油钻井领域尤其是海上钻井中,随钻电磁波测量技术因其在地质导向和边界探测中具有重要价值而得到广泛开发和应用。然而传统的随钻测量技术均采用同轴发射和接收天线,虽然可以确定油气储层的位置,但由于缺乏方位灵敏性,无法提供各向异性储层的定向信息,因而不足以对各向异性地层进行评价。自2000年开始,随着定向随钻测量的引入,产生了新一代定向测井仪器。这些仪器除含有轴向天线外,还有倾斜和横向天线,能够精确测量地层各向异性、倾斜角和方位角,提高了地层界面预测和地质导向的能力。本文通过研究电磁波在各层介质中的反射和透射规律,导出介质层中电磁波的解析表达式,计算电磁波电阻率随钻测量的幅度衰减和相移,分析定向电磁测量对地层界面的灵敏性。同时计算随钻电阻率仪器激发的电磁场随仪器方位变化的关系,分析方位电阻率成像的规律。首先,本文从麦克斯韦方程出发,将测井仪器发射源简化为一个磁偶极子,其在层状地层中产生的电磁场可以分解为电场矢量垂直于入射面的线性极化波(TE波)和平行于入射面的线性极化波(TM波),通过研究这两种波在各层介质中的反射和透射规律,利用边界条件得出磁偶极子在水平层状介质中的解析表达式,并以此为基础计算电磁波随钻测量的幅度衰减和相移。其次,采用不同目的层厚度的三层和多层地层模型,计算定向幅度衰减随仪器方位变化的关系,分析方位电阻率成像的分辨率。结果表明,当目的层厚度较大时,通过成像可以确定地层边界；但当厚度逐渐减小,成像效果变差,甚至可能曲解真实地层情况,影响测井决策。最后,根据电磁波随钻测量的幅度衰减和相移表达式,结合方位电阻成像,分析定向电磁测量对地层界面的灵敏性,研究地层相对倾角和接收天线倾角对电磁测量的影响。计算结果表明,线圈距和目的层厚度越大、频率越低、目的层和围岩电阻率差别越大,定向电磁测量的探测范围越大;随着地层倾角和接收天线倾角的增加,定向电磁响应在接近地层界面时的变化越明显,对地层界面的灵敏性越强。同时分析定向电磁测量信号的方位分辨特性,实现对地层界面的准确预测。以上工作和结论对方位电阻率测井具有实际意义,为分析定向电磁响应和方位电阻成像提供了理论基础。
[Abstract]:In the field of petroleum drilling, especially in offshore drilling, electromagnetic wave measurement while drilling has been widely developed and applied because of its important value in geological guidance and boundary detection. However, the traditional techniques of while drilling adopt coaxial transmitting and receiving antenna. Although the location of oil and gas reservoir can be determined, the orientation information of anisotropic reservoir can not be provided because of the lack of azimuth sensitivity. Therefore, it is not enough to evaluate anisotropic strata. Since 2000, with the introduction of directional logging while drilling, a new generation of directional logging tools has been produced. These instruments not only contain axial antennas, but also have inclined and lateral antennas, which can accurately measure the anisotropy, inclination and azimuth angle of the formation, and improve the ability of prediction and geological orientation of the formation interface. In this paper, the law of reflection and transmission of electromagnetic wave in each layer of medium is studied, the analytical expression of electromagnetic wave in dielectric layer is derived, and the amplitude attenuation and phase shift of electromagnetic wave resistivity measured while drilling are calculated. The sensitivity of directional electromagnetic measurement to formation interface is analyzed. At the same time, the relationship between the electromagnetic field excited by the resistivity instrument while drilling and the azimuth variation of the instrument is calculated, and the rule of azimuth resistivity imaging is analyzed. First of all, based on Maxwell equation, the source of logging tool emission is simplified to a magnetic dipole. The electromagnetic field produced in layered strata can be decomposed into linear polarization wave (TE wave) with electric field vector perpendicular to the incident plane and linear polarization wave parallel to the incident plane (TM wave). By studying the law of reflection and transmission of these two kinds of waves in different layers of media, the analytical expressions of magnetic dipole in horizontal layered media are obtained by using the boundary conditions, and the amplitude attenuation and phase shift of electromagnetic waves measured while drilling are calculated based on these expressions. Secondly, three-layer and multi-layer formation models with different thickness of target layer are used to calculate the relationship between the attenuation of directional amplitude and the azimuth of the instrument, and the resolution of azimuth resistivity imaging is analyzed. The results show that when the thickness of the target layer is large, the formation boundary can be determined by imaging, but when the thickness decreases gradually, the imaging effect becomes worse, and it may even misinterpret the real formation condition and affect the logging decision. Finally, according to the expressions of amplitude attenuation and phase shift of electromagnetic wave measurement while drilling, combined with azimuth resistance imaging, the sensitivity of directional electromagnetic measurement to formation interface is analyzed, and the influence of relative dip angle of formation and angle of receiving antenna on electromagnetic measurement is studied. The results show that the larger the coil distance and the thickness of the target layer, the lower the frequency, the greater the difference between the resistivity of the target layer and the surrounding rock, and the larger the detection range of the directional electromagnetic measurement. With the increase of the dip angle of formation and the angle of receiving antenna, the more obvious the change of directional electromagnetic response is near the formation interface, the stronger the sensitivity to the formation interface is. At the same time, the azimuth resolution characteristics of the directional electromagnetic measurement signal are analyzed, and the accurate prediction of the formation interface is realized. The above work and conclusions are of practical significance to azimuth resistivity logging and provide a theoretical basis for the analysis of directional electromagnetic response and azimuth resistance imaging.
【学位授予单位】：山东大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P631.81

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