套管井应力集中诱导井周波速各向异性的研究

The effects of stress concentrations of cased hole on induced azimuthal anisotropy velocity distribution

针对在套管井中应用正交偶极声测井检测地层各向异性和确定异常构造应力的需要,本文通过求解水平构造应力作用下套管井的应力场分布,应用声弹性理论说明应力集中对套管井井周弹性波速空间分布的影响,分析了波速空间分布对加套管后的正交偶极各向异性声测量的影响.井孔、套管、水泥环和地层系统的复杂性改变了原裸眼井情况地层中的应力场分布,使应力集中的范围明显缩小到井眼附近.对应不同方位径向偏振横波的交叉点向井孔附近移动.横波波速空间分布的方位极值规律发生变化,但纵波波速空间分布的方位极值规律不变,仍能提供最大远场构造应力施加的方向.

According to the need of estimating anisotropy and abnormal stress of formation by cross-dipole logging in a cased hole, we show how stress concentrations affect the velocity distribution of formation around a cased hole, and how the velocity distribution influences the cross-dipole anisotropy measurements by computing the stress distribution of a cased hole subjected to the tectonic stress and applying acoustoelasticity theory. The introduction of casing and cement in a cased hole results in that the range of stress concentrations becomes small. The crossover of shear-waves of radial polarization moves towards the borehole. The azimuthal extremum of shear-waves is changed. But the azimuth of compressional velocity minima can still provide an excellent indicator of the direction of maximum far-field tectonic stress.