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On the Selection of the Eigenmodes of an Anisotropic WaveguideNormal access

Authors: A.A. Nikitin and T.V. Zharnikov
Event name: Geomodel 2019
Session: Математические методы обработки геологической и геофизической информации
Publication date: 17 September 2019
DOI: 10.3997/2214-4609.201950089
Organisations: EAGE
Language: Russian
Info: Extended abstract, PDF ( 615.98Kb )
Price: € 20

Recently, the analysis of anisotropic elastic properties of rock has become increasingly important. This is due to the increasing importance of geomechanical analysis required for solving such tasks as designing hydraulic fracturing, predicting the wellbore stability and others. Sonic logging is primary method for determining the anisotropic elastic moduli tensor. The reservoir is usually considered as transversely isotropic medium with an axis of symmetry inclined at some angle to borehole axis. The elastic moduli tensor of such medium is determined by five components. At present, the method of analyzing sonic logging data based on the semi-analytical finite element method (SAFE) is being actively developed. This technique belongs to the class of variational methods and is based on the reduction of three-dimensional problem to two-dimensional ones. The main difficulties arising in the calculation of dispersion curves of borehole modes is the appearance of a large number of eigenmodes, only a small part of which occurs in reality. In this regard, the problem of modes classification naturally arises. In this paper the approach to solving this problem is proposed, which is based on the analysis of radial and spatial distributions of kinetic energy density of eigenfunction, its symmetry class and its polarization.

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