复杂井孔条件下随钻多极子波场的数值模拟研究

发布时间：2018-05-04 22:29

本文选题：有限元法 + 复杂井孔　；参考：《中国石油大学(华东)》2015年硕士论文

【摘要】：随着随钻测井技术的广泛应用,国内外对于随钻多极子波场的传播特性研究越来越多。目前,主要的研究方向是复杂井孔和各向异性介质条件下随钻多极子波场的传播特性的研究。随钻仪器偏心、井孔的不规则形状和地层差异等多方面的原因造成了随钻多极子波场的变化。本文在各向同性介质条件下,基于COMSOL有限元软件的声固耦合模块针对声源偏心、井孔几何结构变化和声源振动方向变化对随钻多极子声场的影响进行数值模拟研究,分析复杂井孔条件下随钻多极子波场的传播特性,这对于随钻声波测井数据解释有重要意义。本文首先通过将有限元法的模拟计算结果与实轴积分法模拟计算结果进行对比,验证了使用COMSOL有限元软件进行模拟计算的准确性。然后采用偶极子和四极子两种声源,对声源偏心、椭圆井孔和声源振动方向变化条件下的随钻多极子波场进行模拟,数据计算处理结果表明:圆形井孔中的随钻偶极子声波测井波列中存在着钻铤模式波和地层模式波两种波动模式且地层模式波没有清晰的到时起点,随着偶极子声源偏心距离的增加,钻铤模式波和地层模式波的幅度出现了近似线性增大的趋势,但当声源偏心距离较大时,钻铤模式波和地层模式波幅度迅速下降。椭圆形井孔中的随钻偶极子声波测井波列中也存在着钻铤模式波和地层模式波两种波动模式且地层模式波没有清晰的到时起点,随着偶极子声源偏心距离的增加,钻铤模式波和地层模式波的幅度也逐渐变大;随着椭圆偏心率的增大,钻铤模式波的到时前移,钻铤模式波和地层模式波的幅度都逐渐增大;随着声源振动方向与椭圆长轴夹角的增加,钻铤模式波的到时后移,钻铤模式波和地层模式波的幅度都逐渐减小。对于四极子声源激发的声场而言,当声源居中时,圆形井孔中的随钻四极子声波测井波列中仅存在一种地层模式波,具有清晰的到时起点;而椭圆形井孔中的随钻四极子声波测井波列中存在着钻铤模式波和地层模式波共两种波动模式;随着四极子声源偏心距离的增加,无论是圆形井孔还是椭圆形井孔,在随钻四极子声波测井波列中,除原有的地层模式波外,在地层模式波前面都出现了一种新的波动模式(W波动模式),导致地层模式波也没有清晰的到时起点,并且W模式波和地层模式波的幅度都呈现随声源偏心距离增加而增大的趋势。对于对椭圆井孔中四极子激发的声场模拟结果表明,随着椭圆偏心率的增大,地层模式波的到时提前,地层模式波的幅度近似指数规律增加。
[Abstract]:With the wide application of logging while drilling technology, there are more and more researches on the propagation characteristics of multipole wavelet field while drilling at home and abroad. At present, the main research direction is to study the propagation characteristics of multipole wavelet field under the condition of complex borehole and anisotropic medium. The variation of multipole wavelet field is caused by the eccentricity of instruments while drilling, the irregular shape of borehole and the difference of formation. In this paper, the acoustic coupling module based on COMSOL finite element software is used to simulate the effects of sound source eccentricity, wellbore geometric structure change and sound source vibration direction change on the sound field under isotropic medium. It is important to analyze the propagation characteristics of multipole wavelet field while drilling under the condition of complex borehole, which is of great significance for the interpretation of acoustic logging data while drilling. In this paper, the simulation results of the finite element method are compared with the results of the real axis integration method, and the accuracy of the simulation calculation using the COMSOL finite element software is verified. Then two kinds of sound sources, dipole and quadrupole, are used to simulate the multipole wave field while drilling under the condition of the eccentricity of sound source, the variation of vibration direction of elliptical hole and sound source. The data processing results show that there are two wave modes, drill collar mode wave and formation mode wave, in the drilling dipole acoustic logging wave train in the circular well hole, and the formation mode wave does not have a clear arrival starting point. With the increase of eccentric distance of dipole source, the amplitude of collar mode wave and formation mode wave increases linearly, but when the eccentric distance of sound source is large, the amplitude of drill collar mode wave and formation mode wave decreases rapidly. There are two kinds of wave patterns, collar mode wave and formation mode wave, in the drilling dipole acoustic logging wave train in the elliptical hole, and the formation mode wave does not have a clear arrival starting point, as the eccentric distance of the dipole sound source increases, The amplitude of drill collar mode wave and formation mode wave also increases gradually, with the increase of elliptical eccentricity, the drill collar mode wave moves forward, and the drill collar mode wave and formation mode wave increase gradually. With the increase of the angle between the direction of sound source vibration and the long axis of the ellipse, the drill collar mode wave moves back and back, and the amplitude of drill collar mode wave and formation mode wave decreases gradually. For the sound field excited by the quadrupole sound source, when the sound source is in the center, there is only one formation mode wave in the drilling quadrupole acoustic logging wave train in the circular well hole, which has a clear arrival starting point. However, there are two modes of drill collar mode wave and formation mode wave in the four-pole acoustic logging while drilling in the elliptical hole, and with the increase of eccentric distance of the quadrupole sound source, no matter the circular well hole or the elliptical hole, In the quadrupole acoustic logging while drilling, in addition to the original formation mode waves, a new wave mode / W wave pattern appears in front of the formation mode wave, which results in the formation model wave also having no clear arrival starting point. The amplitude of the W mode wave and the formation mode wave increase with the increase of the eccentric distance of the sound source. The simulation results of sound field excited by quadrupole in elliptical borehole show that with the increase of elliptical eccentricity, the arrival of formation mode wave is early, and the amplitude of formation mode wave increases approximately exponentially.
【学位授予单位】：中国石油大学(华东)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P631.81

【相似文献】