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Effect of background fields on three‐dimensional finite element analysis of induction logging
Author(s) -
Badea Eugene A.,
Everett Mark E.,
Shen Liang C.,
Weiss Chester J.
Publication year - 2001
Publication title -
radio science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.371
H-Index - 84
eISSN - 1944-799X
pISSN - 0048-6604
DOI - 10.1029/2000rs002576
Subject(s) - borehole , finite element method , transmitter , electromagnetic field , electromagnetic induction , finite element limit analysis , computer science , mathematical analysis , acoustics , mathematics , geology , mixed finite element method , physics , telecommunications , electromagnetic coil , geotechnical engineering , thermodynamics , channel (broadcasting) , quantum mechanics
Three‐dimensional controlled‐source electromagnetic induction algorithms are generally formulated in terms of secondary fields or potentials. The selection of the primary solution is somewhat arbitrary but can greatly influence the efficiency of finite element codes. A simple induction logging problem demonstrates this statement. Responses are computed using a three‐dimensional finite element method for two different selections of the primary potential, one that includes the borehole effect and one that does not. The accuracy of the numerical solution, for a given mesh size, increases dramatically when the borehole effect is included in the primary solution. This is because the sharp gradients in the electromagnetic field near the transmitter due to the presence of the borehole are coded as an analytic source term and do not have to be captured by the numerical approximation. Whenever possible, finite element analysts should select a convenient primary solution that closely matches the anticipated total solution in the immediate vicinity of the transmitter.