井周速度变化时的散射波特征研究

发布时间：2018-01-17 16:01

本文关键词：井周速度变化时的散射波特征研究　出处：《中国石油大学(华东)》2015年硕士论文　论文类型：学位论文

【摘要】：实际测井中经常遇到钻井机械碰撞、地层应力释放、钻井流体侵蚀或者页岩粘土膨胀等现象,这都会造成井壁附近地层参数的变化,进而导致井壁附近的地层弹性波速度与远离井壁处的速度相比相差很多。为了研宄该地层中井壁附近的速度变化情况,本文介绍了一种利用单极纵波提取散射波信息反演地层径向纵波速度剖面的层析成像方法,该方法能够利用散射波的变化特征重建地层径向纵波速度变化,它对评价井壁稳定性、估算地应力、探测流体侵入、优化油藏生产等都有着重要的意义。本文将在地震勘探领域已经获得广泛应用的弹性波散射理论应用到声波测井领域。构建了合适的声速扰动模型,将弱非均匀介质中根据Born近似获得的散射波积分表达式在柱坐标先展开,针对平面波入射和球面波入射的不同情况,进一步理论求解了这两种情况下的散射波解析表达式。将地震中常用的Rytov近似与Born近似得到的结果进行对比,发现,在地震领域内适用性更好的Rytov近似并不适合声波测井领域,在声波测井领域内,Born近似的使用效果更好。利用理论求解的不同速度扰动模型下平面波和球面波分别入射得到的不同的散射波理论表达式,结合发展成熟的有限差分等方法,进行井周散射声场的数值模拟,分别讨论井周径向和周向地层速度变化情况下的散射波变化特征,结果表明,在井周径向和周向速度变化时,散射波均能给出很好的响应。尤其是针对不同周向方位上速度增加或者降低的情况,散射波的相位正负变化十分明显。十分有利于速度变化情况的反演。最后,将得到的散射波理论表达式用于声波测井数据反演,分别讨论不同目标函数,不同声源入射,不同速度扰动模型下的反演情况,根据不同情况下得到的反演结果进行优化选择,并将之应用于现场实际数据的处理,取得了令人满意的效果。
[Abstract]:Drilling machine collision, formation stress release, drilling fluid erosion or shale clay expansion are often encountered in actual logging, all of which will cause changes in formation parameters near the wellbore. In order to study the variation of formation velocity near the well wall, the elastic wave velocity of formation is much different from the velocity far away from the well wall. In this paper, a tomography method for retrieving the velocity profile of radial longitudinal wave of strata by extracting scattering wave information from unipolar longitudinal wave is introduced. This method can reconstruct the velocity change of radial longitudinal wave of stratum by using the variation characteristic of scattering wave. It can be used to evaluate wellbore stability, estimate in-situ stress and detect fluid intrusion. Optimization of reservoir production is of great significance. In this paper, elastic wave scattering theory, which has been widely used in seismic exploration, has been applied to acoustic logging, and a suitable acoustic disturbance model has been constructed. The integral expression of scattering wave obtained by Born approximation in weakly inhomogeneous medium is first expanded in cylindrical coordinates, aiming at the different cases of plane wave incidence and spherical wave incidence. Furthermore, the analytical expressions of scattering wave in these two cases are solved theoretically, and the results obtained by Rytov approximation and Born approximation are compared and found. Rytov approximation, which has better applicability in seismic field, is not suitable for acoustic logging. The Born approximation is more effective. The different theoretical expressions of scattering wave are obtained by using the different velocity perturbation model solved by the theory of plane wave and spherical wave respectively. Combined with the developed finite difference method, the numerical simulation of the scattering sound field around the well is carried out, and the variation characteristics of the scattering wave in the radial and circumferential formation velocities around the well are discussed, respectively. When the radial and circumferential velocities around the well vary, the scattering wave can give a good response, especially for the different circumferential azimuth increase or decrease of velocity. The positive and negative phase change of scattering wave is very obvious, which is very beneficial to the inversion of velocity change. Finally, the theoretical expression of scattering wave is applied to the inversion of acoustic logging data, and different objective functions are discussed respectively. According to the inversion results obtained under different conditions, the inversion results obtained from different incident sources and different velocity perturbation models are optimized and applied to the processing of field actual data, and the results are satisfactory.
【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

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