{"title":"Estimation of anisotropy parameters in vertical transverse isotropy media using the ray-based tomography","authors":"Gualtiero Böhm, Biancamaria Farina","doi":"10.1111/1365-2478.13526","DOIUrl":null,"url":null,"abstract":"<p>In seismic exploration, it is very important to consider the presence of anisotropy in order to image the subsurface correctly. The knowledge of anisotropic parameters leads to more precise characterization of reservoir, fracture density and flow paths. However, conventional geophysical methods do not directly measure these parameters, and it is useful to have a method to estimate them from seismic data. In the weak transverse isotropy approximation, the fields to be considered are the vertical and horizontal velocity components and the Thomsen parameters <span></span><math>\n <semantics>\n <mi>ε</mi>\n <annotation>$\\rm \\epsilon$</annotation>\n </semantics></math> and <span></span><math>\n <semantics>\n <mi>δ</mi>\n <annotation>$\\rm \\delta$</annotation>\n </semantics></math>. We present a method for estimating the anisotropic Thomsen parameters in the presence of weak vertical transverse isotropy using P-wave traveltime tomography based on anisotropic ray tracing. Depending on the available information, we propose different approaches to retrieve the unknowns. A conventional three-dimensional traveltime tomography algorithm has been extended to include anisotropic ray tracing and using the algebraic reconstruction technique or modified simultaneous iterative reconstruction technique to retrieve the unknowns. We test the method on synthetic examples for the inversion of transmitted and reflected traveltimes, and we evaluate the sensitivity of the tomographic results to the available information. Furthermore, we also consider the case of tilted transverse isotropy in a seismic reflection example.</p>","PeriodicalId":12793,"journal":{"name":"Geophysical Prospecting","volume":null,"pages":null},"PeriodicalIF":1.8000,"publicationDate":"2024-04-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Geophysical Prospecting","FirstCategoryId":"89","ListUrlMain":"https://onlinelibrary.wiley.com/doi/10.1111/1365-2478.13526","RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"GEOCHEMISTRY & GEOPHYSICS","Score":null,"Total":0}
引用次数: 0
Abstract
In seismic exploration, it is very important to consider the presence of anisotropy in order to image the subsurface correctly. The knowledge of anisotropic parameters leads to more precise characterization of reservoir, fracture density and flow paths. However, conventional geophysical methods do not directly measure these parameters, and it is useful to have a method to estimate them from seismic data. In the weak transverse isotropy approximation, the fields to be considered are the vertical and horizontal velocity components and the Thomsen parameters and . We present a method for estimating the anisotropic Thomsen parameters in the presence of weak vertical transverse isotropy using P-wave traveltime tomography based on anisotropic ray tracing. Depending on the available information, we propose different approaches to retrieve the unknowns. A conventional three-dimensional traveltime tomography algorithm has been extended to include anisotropic ray tracing and using the algebraic reconstruction technique or modified simultaneous iterative reconstruction technique to retrieve the unknowns. We test the method on synthetic examples for the inversion of transmitted and reflected traveltimes, and we evaluate the sensitivity of the tomographic results to the available information. Furthermore, we also consider the case of tilted transverse isotropy in a seismic reflection example.
在地震勘探中,考虑各向异性的存在对于正确绘制地下图像非常重要。对各向异性参数的了解有助于更精确地描述储层、裂缝密度和流动路径。然而,传统的地球物理方法并不能直接测量这些参数,因此有一种从地震数据中估算这些参数的方法非常有用。在弱横向各向同性近似中,需要考虑的场是垂直和水平速度分量以及汤姆森参数和。我们提出了一种在存在弱垂直横向各向同性的情况下,利用基于各向异性射线追踪的 P 波行进时间层析成像估算各向异性汤姆森参数的方法。根据可用信息的不同,我们提出了不同的未知数检索方法。我们扩展了传统的三维行进时间层析成像算法,将各向异性射线追踪纳入其中,并使用代数重建技术或改进的同步迭代重建技术来检索未知量。我们在反演透射和反射旅行时间的合成示例中测试了该方法,并评估了层析成像结果对可用信息的敏感性。此外,我们还考虑了地震反射实例中倾斜横向各向同性的情况。
期刊介绍:
Geophysical Prospecting publishes the best in primary research on the science of geophysics as it applies to the exploration, evaluation and extraction of earth resources. Drawing heavily on contributions from researchers in the oil and mineral exploration industries, the journal has a very practical slant. Although the journal provides a valuable forum for communication among workers in these fields, it is also ideally suited to researchers in academic geophysics.