柱状分层孔隙介质中的SH-TE声电效应测井研究

发布时间：2018-03-25 03:34

本文选题：柱状分层　切入点：孔隙地层　出处：《吉林大学》2017年硕士论文

【摘要】：在流体饱和孔隙介质中的动电效应在地球物理学界一直是热点问题之一。基于这种效应人们提出声电效应测井技术。由于通过流体耦合不可能由井内声源连续在孔隙介质中激发出SH波,所以近些年也很少考虑通过激发SH波来进行横波测井。而SH波在水平分层介质中是与P-SV波解耦的,并且它与偏振方向平行的界面间传播时,不产生转换波,这样一来如果SH波能够得以利用将会很方便。1994年White设想过利用紧贴井壁的水平声源激发SH波,并在井外均质地层进行了初步理论求解,表明横波的直接探索是有可能实现的。本文对柱状双层孔隙介质包围井孔SH-TE动电测井进行理论模拟。本文对井外为双层柱状的流体饱和孔隙介质的动电效应进行研究,即井内为流体,与井壁相连的是一层环状孔隙夹层,紧接着是一层无限大的孔隙地层。此模型不仅可以模拟有侵入带时的地层,也可以利用此模型对探测界面进行研究。对SH-TE动电测井,基于Biot理论和Pride理论,再通过引入势函数和采用赫姆霍兹分解的方法,理论求解出井内无源情况下的电磁场通解的表达式,和井外的声电耦合波场的表达式。本文还求解了在声场不受其诱导电场影响的前提下,井内外各波场的表达式,并做出了分析。通过数值模拟可以得到,在声场全波波形上能够观察到SH波与love波两种波形;在电磁场全波波形上能够观察到两个界面电磁场和与声场对应的伴随电磁场。结果表明,井半径与孔隙夹层厚度虽然对声场的影响比较复杂,但是对界面响应影响并不明显。随着井半径的增大,love波的伴随电场会减小。井内矿化度的改变对声场与电场影响也并不明显。孔隙夹层矿化度的改变对声场的影响很小,但是对外界面响应影响比较明显,当孔隙夹层与外层孔隙的矿化度差异越大,界面响应就越明显。对于外层孔隙的矿化度也有类似的结果。随着孔隙夹层的孔隙度逐渐增大,声场的SH波与love波的速度增大,幅度减小。内界面产生的电磁波幅度也增大。对于外界面响应而言,当孔隙夹层与外层孔隙的孔隙度差异越大,界面响应就越明显。而外层孔隙介质的孔隙度对声场影响并不明显,对外界面响应也是两层介质的差异越大,界面响应就越明显。两层孔隙介质的弯曲度对声场的影响并不大,但是对电场而言,随着两层孔隙介质的弯曲度的增大,外界面响应就越明显。通过考察可得,对于SH-TE动电测井,可利用辐射电磁波能够最先到达接收器这一特点,探测存在较大差异的界面。
[Abstract]:The electrokinetic effect in fluid saturated porous media has been one of the hot topics in geophysics. Based on this effect, acoustic and electric effect logging technology has been proposed. SH waves are excited in porous media, Therefore, in recent years, very little consideration has been given to shear wave logging by stimulating SH waves, which are decoupled from P-SV waves in horizontal stratified media and do not produce converted waves when they propagate between interfaces parallel to the polarization direction. In this way, if the SH wave can be used, it will be convenient. In 1994, White envisaged that the SH wave would be excited by a horizontal sound source close to the wall of the well, and the initial theoretical solution was carried out in the homogeneous formation outside the well. It is shown that the direct exploration of shear waves is possible. In this paper, the theoretical simulation of SH-TE dynamic logging in cylindrical bilayer porous media is carried out. In this paper, the dynamic and electrical effects of fluid saturated porous media outside the well are studied. That is, the fluid in the well is connected to the wellbore by a layer of annular pore intercalation, followed by an infinite pore formation. This model can not only simulate the formation with an intrusive zone, This model can also be used to study the detection interface. For SH-TE electrokinetic logging, based on Biot theory and Pride theory, the potential function is introduced and Hem Holtz decomposition method is adopted. The general solution of electromagnetic field in the case of passive well and the expression of acoustoelectric coupling wave field outside the well are obtained theoretically. The expressions of the wave fields inside and outside the well are also solved without the influence of the induced electric field on the sound field. Through numerical simulation, two kinds of waveforms, SH wave and love wave, can be observed on the full wave waveform of sound field. Two interface electromagnetic fields and associated electromagnetic fields corresponding to sound field can be observed on the full wave waveforms of electromagnetic field. The results show that the influence of well radius and pore intercalation thickness on sound field is quite complex. However, the effect on the interface response is not obvious. With the increase of the radius of the well, the accompanying electric field of love wave will decrease. The change of the mineralization degree in the well has no obvious effect on the sound field and electric field, and the change of the mineralization degree of the pore intercalation has little effect on the sound field. However, the effect on the external surface response is more obvious. The larger the difference between the pore intercalation and the outer pore mineralization, the more obvious the interface response is, and the similar result is obtained for the outer pore salinity. As the porosity of the pore intercalation increases, The velocity of SH wave and love wave of sound field increases and the amplitude decreases. The amplitude of electromagnetic wave generated by internal interface also increases. For the response of external surface, the greater the difference of porosity between pore intercalation and outer pore, The more obvious the interface response is, the less the porosity of the outer porous medium affects the sound field, the more obvious the external interface response is, the greater the difference between the two layers is, the more obvious the interface response is. The curvature of the two layers of porous media has little effect on the sound field. But for the electric field, with the increase of the curvature of the two layers of porous media, the response of the external interface becomes more obvious. From the investigation, it can be obtained that the radiative electromagnetic wave can reach the receiver first for the SH-TE electrodynamic logging. There are large differences in the detection of interfaces.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P631.81

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