水平应力作用下不同胶结状况的套管井声场特性研究

To study the acoustic waves in the cased hole is very important to utilize the acoustic logging data efficiently to evaluating reservoir and cement-bond condition. There are many researches about acoustics waves in cased hole, however, in the fact the cased hole are mostly applied with abnormal stresses and some paid attention on how to estimate abnormal stresses by flexural waves excited dipole source. Moreover most authors did not considered the effect of abnormal stresses on acoustic waves in the cased hole. In order to know characteristics of acoustic waves in cased borehole under horizontal stress and the influence on evaluating cement-bond, we have a pre-research and propose this project based on nonlinear acoustics. The project will study the acoustic fields excited by monopole and dipole sources in the cased hole with different bonding condition. For the different cement-bond condition, the parts of study are listed below. First, to accomplish the calculation and analysis of the stresses and velocity distribution around the cased hole under horizontal stress; Second, to investigate acoustoelastic effects on Stoneley, Pseduo-Rayleigh and Flexural waves, give the velocity dispersions fomula , simulate and analyze the change of phase velocity due to applied stresses. Third, to accomplish the simulation and nalaysis of transit acoustic waves in the stress-induced -anisotropic cased-hole system using 3-D finite differnce method.The study is of significance in both academic and real application research，and it is the development of acoustics theory for complex borehole.

套管井的声场特性研究对充分利用声波测井资料评价储层物性或水泥胶结状况是十分重要的。而油田的套管井常伴有异常地应力的作用，国内外关于套管井声场的研究，除了利用偶极弯曲波开展异常应力预测外，基本没考虑地应力对套管井声场的影响，为深入认识地应力作用下套管井井周声场的传播特性，认清其对胶结状态评价的影响，经预研，基于非线性声学理论，本项目提出水平应力作用不同胶结状况套管井单、偶极源激励的声场研究。针对不同胶结状况的套管井，研究内容包括：实现受应力作用套管井井周应力和纵、横波速度场分布计算与分析；推导套管井斯通利波、伪瑞利波和弯曲波等模式波声弹性方程，模拟并分析由应力引起的相速度的变化；开展应力诱导的各向异性套管井孔体系单、偶极源瞬态声场的三维有限差分数值模拟与分析，认识地应力对检测水泥胶结状况的影响。这是一项既有极强的理论性，又有应用价值的课题，是对复杂的井孔声场理论的发展。

套管井的声场特性研究对充分利用声波测井资料评价储层物性或水泥胶结状态是十分重要的。油田的套管井常伴有异常地应力的作用，基于非线性声学理论，本项目研究了水平地应力作用不同胶结状况套管井点源和偶极源激励的声场,是复杂的井孔声场理论的发展。对套管井的不同胶结状态，首先实现了受应力作用套管井井周应力和速度场分布计算与分析，结果表明套管、水泥层的加入使地层中应力分布的非均匀性减小,当胶结状态变化时其非均匀性会发生变化，进而影响近场波速的分布。其次基于非线性声学理论推导了套管井不同胶结状态斯通利波、伪瑞利波和弯曲波等模式波声弹性方程，采用摄动法计算并分析由应力引起导波相速度的变化。结果表明:在单轴应力作用下,不同胶结状态的导波(斯通利波,伪瑞利波和弯曲波)的相速度分别增加;弯曲波在0度和90度方位随频率出现交叉点，而交叉位置依赖于胶结状态。当界面出现滑移时井周地层中的应力集中增强，对应的径向横波的交叉点向远场方向移动。因此在实际测量中对规则的圆形套管井仍可以通过偶极测井获取的弯曲波的频散曲线的交叉来确定是否存在应力的作用。最后，依据声弹性学，导出了套管井不同胶结状况的柱坐标系下应力诱导的各向异性介质弹性系数矩阵。采用时空交错网格上的中心差商和非裂化的完全匹配层（NPML）作为吸收边界，实现了柱坐标系下套管井应力诱导的非井轴对称井周各向异性井孔体系点源和偶极源声场的三维有限差分数值模拟。验证和分析应力作用下在不同胶结状况由点源和偶极声源在不同中心频率激发的全波列波形。研究结果表明波场的各成份主要与套管井的胶结状况相关，水平应力主要影响波形幅度和到时。在基金的支持下，按照项目计划，完成了主要内容，深入认识了地应力作用的套管井的声场特性,并为胶结评价和测井解释提供新认识和理论依据。期间，发表学术论文14篇（其中SCI 9篇），毕业博士1名，毕业硕士8名。