岩石三阶弹性模量与加压钻孔孔周声速分布的实验探究

发布时间：2019-06-09 21:27

【摘要】：声弹性理论的发展和应用为地下应力的检测提供了新的途径，在有限（非无限小）静应力引起的非线性形变体上激发小扰动波场是典型的非线性声学中的声弹性问题。在非线性声学中，介质的三阶弹性模量是非常重要的参数。依据声弹理论，油气储层岩石的三阶弹性常数直接关系到声速和地应力的敏感性，因此近年来岩石三阶弹性模量的测量一直是一个比较重要的课题，受到诸多学者的关注和研究。另外，如果顾及非线性静形变，地应力将诱导出介质等效各向异性,而当存在钻孔的介质受应力作用时会出现应力集中的问题，从而影响孔周的声速分布，这为我们提供了获取应力信息的机会，为此近年来开展了诸多的理论和实验工作。而受应力作用井孔的声速分布实验测量，国内外主要是开展了裸眼井纵波速度分布，对于横波速度分布，以及套管声速分布尚未见报道。本文正是针对以上两个方面的问题开展了岩石三阶弹性模量的测量与加压钻孔孔周声速分布的实验探究工作。首先，推导了应力诱导的各向异性场方程--Piola-Kirchhoff方程和在任意三轴应力作用下诱导的等效弹性模量，由运动方程和平面波解给出相应的Christoffel方程导出了群速度。并数值计算和分析在三维应力作用下沿任意方向的相速度。数值结果表明：单轴应力作用下的介质呈现横向各向同性的特征,而双轴不等应力作用的介质呈现正交各向异性特性；三轴不等应力作用下的介质也呈现正交各向异的特征，但在相同水平应力作用下，第三轴应力的出现使介质相速度的方位各向异性减弱。其次，通过双发双收脉冲信号，在单轴加载条件下测量沿锈石岩样厚度方向传播的纵波，偏振与加载方向垂直以及平行的横波速随应力的变化来实现岩石三阶模量的反演。由此依据声弹公式获取了三个独立的三阶弹性常数（共十组），进一步通过最小二乘法获得相对高精度的三个独立的三阶弹性常数，利用所得到的三个独立的三阶弹性常数来推导单轴应力作用下的纵波以及横波波速的数值，所得数值与实验测量值几乎相同，从而验证了此种反演方法的可行性。最后，通过双发双收脉冲信号，在单轴加载条件下测量钻孔尼龙孔周的纵波、两个横波波速，实验结果表明加载钻孔孔周波速的最大、最小方向分别对应着加载样品的最小、最大主应力方向。Winkler在1996曾设计实验，得到纵波速度的分布符合这种规律，本文则证实了横波速度的分布同样符合。因此，该方法可以简单直观的确定水平主应力的方向。然后，在钻孔的尼龙样品的孔壁上黏合上钢管，，与未加钢管的样品一样，对其施加单轴压力，并且测量孔附近的纵波、偏振方向与单轴应力方向分别垂直与平行的两个横波波速随方位角的变化，整理分析其结果，与未加钢管的结果做对比。结果显示加上套管之后，速度的极值位置发生变化，速度的分布也更为复杂。
[Abstract]:The development and application of the acoustic elasticity theory provide a new way for the detection of the underground stress, and the excitation of the small-disturbance wave field on the nonlinear-shaped variant caused by the finite (non-infinitesimal) static stress is a typical acoustic-elastic problem in the non-linear acoustics. In non-linear acoustics, the third-order elastic modulus of the medium is a very important parameter. According to the acoustic-elastic theory, the third-order elastic constant of the oil-gas reservoir rock is directly related to the sensitivity of the sound speed and the in-situ stress, so the measurement of the third-order elastic modulus of the rock has been a relatively important subject in recent years, and is subject to the attention and the research of many scholars. in addition, if that non-linear static deformation is taken into account, the geostress will induce the equivalent anisotropy of the medium, In this regard, many theories and experiments have been carried out in recent years. The velocity distribution of longitudinal wave in the open hole is mainly carried out at home and abroad, and the distribution of the transverse wave velocity and the distribution of the sound velocity of the casing have not been reported. In this paper, the third-order elastic modulus measurement of the rock and the experimental investigation on the velocity distribution of the hole of the pressurized drilling hole are carried out in the light of the above two aspects. First, the stress-induced anisotropic field equation--Piola-Kirchhoff's equation and the equivalent elastic modulus induced by any three-axis stress are derived. The phase velocity in any direction under the action of three-dimensional stress. The numerical results show that the medium under the action of uniaxial stress presents the characteristics of lateral isotropy, and the medium with biaxial stress does not exhibit the characteristics of orthotropic anisotropy, and the medium under the action of three-axis unequal stress also presents the characteristic of the orthogonal anisotropy, but at the same horizontal stress Under the condition of the third axial stress, the orientation anisotropy of the velocity of the medium is reduced. Weak. Second, the third-order modulus of the rock is realized by measuring the longitudinal wave, the polarization and the loading direction, and the variation of the parallel transverse wave velocity with the stress under the uniaxial loading condition. In this paper, three independent third-order elastic constants (10 sets) are obtained according to the acoustic-bomb formula, and three independent third-order elastic constants with relatively high precision are obtained by the least square method. Based on the three independent third-order elastic constants obtained, the numerical values of the longitudinal wave and the wave velocity of the shear wave are derived by using the three independent third-order elastic constants, and the obtained values are almost the same as those of the experimental measurements, so that the inversion method is proved. In the end, the longitudinal wave and the two transverse wave velocities of the drilling nylon hole are measured under the single-axis loading condition by double-transmitting and double-receiving pulse signals. The results show that the maximum and the minimum directions of the wave velocity of the loading hole are the minimum and the maximum of the loading samples, respectively. The direction of the principal stress. Winkler designed the experiment in 1996 to obtain the distribution of longitudinal wave velocity. The cloth is also in line with. Therefore, the method can be simple and intuitive to determine the horizontal master. and then, the steel pipe is bonded on the hole wall of the nylon sample of the drilling hole, the uniaxial pressure is applied to the steel pipe without the steel pipe, and the longitudinal wave, the polarization direction and the uniaxial stress direction in the vicinity of the measuring hole are respectively perpendicular to the parallel two transverse wave wave velocity The change of a steel tube, the result of which is analyzed and the result is compared with that of a non-steel tube. The results show that the extreme position of the velocity is changed and the velocity distribution after the addition of the casing.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P634.1

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