1887
  1. Home
  2. A-Z Publications
  3. Geophysical Prospecting
  4. Volume 59, Issue 2
  5. Article
Volume 59, Issue 2
  • E-ISSN: 1365-2478

Abstract

ABSTRACT

In present‐day land and marine controlled‐source electromagnetic (CSEM) surveys, electromagnetic fields are commonly generated using wires that are hundreds of metres long. Nevertheless, simulations of CSEM data often approximate these sources as point dipoles. Although this is justified for sufficiently large source‐receiver distances, many real surveys include frequencies and distances at which the dipole approximation is inaccurate. For 1D layered media, electromagnetic (EM) fields for point dipole sources can be computed using well‐known quasi‐analytical solutions and fields for sources of finite length can be synthesized by superposing point dipole fields. However, the calculation of numerous point dipole fields is computationally expensive, requiring a large number of numerical integral evaluations. We combine a more efficient representation of finite‐length sources in terms of components related to the wire and its end points with very general expressions for EM fields in 1D layered media. We thus obtain a formulation that requires fewer numerical integrations than the superposition of dipole fields, permits source and receiver placement at any depth within the layer stack and can also easily be integrated into 3D modelling algorithms. Complex source geometries, such as wires bent due to surface obstructions, can be simulated by segmenting the wire and computing the responses for each segment separately. We first describe our finite‐length wire expressions and then present 1D and 3D examples of EM fields due to finite‐length sources for typical land and marine survey geometries and discuss differences to point dipole fields.

© 2010 European Association of Geoscientists & Engineers
Loading

Article metrics loading...

/content/journals/10.1111/j.1365-2478.2010.00926.x
2010-10-04
2024-04-20

  • From This Site

    /content/journals/10.1111/j.1365-2478.2010.00926.x
    dcterms_title,dcterms_subject,pub_keyword
    -contentType:Journal -contentType:Contributor -contentType:Concept -contentType:Institution
    10
    5
Loading full text...

Full text loading...

References

  1. AndersonW.L.1982. Fast Hankel transforms using related and lagged convolutions. ACM Transactions on Mathematical Software 8, 344–368.
    [Google Scholar]
  2. ChaveA.D. and CoxC.S.1982. Controlled electromagnetic sources for measuring electrical conductivity beneath the oceans. 1. Forward problem and model study. Journal of Geophysical Research87, 5327–5338.
    [Google Scholar]
  3. ConstableS. and SrnkaL.J.2007. An introduction to marine controlled‐source electromagnetic methods for hydrocarbon exploration. Geophysics72, WA3–WA12.
    [Google Scholar]
  4. EdwardsR.N.1997. On the resource evaluation of marine gas hydrate deposits using sea‐floor transient electric dipole‐dipole methods. Geophysics62, 63–74.
    [Google Scholar]
  5. EdwardsN.2005. Marine controlled source electromagnetics: Principles, methodologies, future commercial applications. Surveys in Geophysics26, 675–700.
    [Google Scholar]
  6. EdwardsR.N., LawL.K. and DeLaurierJ.M.1981. On measuring the electrical conductivity of the oceanic crust by a modified magnetometric resistivity method. Journal of Geophysical Research86, 11609–11615.
    [Google Scholar]
  7. FrischknechtF.C., LabsonV.F., SpiesB.R. and AndersonW.L.1991. Profiling methods using small sources. In: Electromagnetic Methods in Applied Geophysics (ed. N.M.Nabighian ), pp. 105–270. SEG.
    [Google Scholar]
  8. GieseR., HenningesJ., LüthS., MorozovaD., Schmidt‐HattenbergerC., WürdemannH. et al. 2009. Monitoring at the CO2SINK site: A concept integrating geophysics, geochemistry and microbiology. Energy Procedia 1, 2251–2259.
    [Google Scholar]
  9. JohansenS.E., AmundsenH.E.F., RøstenT., EllingsrudS., EidesmoT. and BhuyianA.H.2005. Subsurface hydrocarbons detected by electromagnetic sounding. First Break 23, 3136.
    [Google Scholar]
  10. KauahikauaJ.1978. Electromagnetic fields about a horizontal electric wire source of arbitrary length. Geophysics43, 1019–1022.
    [Google Scholar]
  11. LøsethL.O. and UrsinB.2007. Electromagnetic fields in planarly layered anisotropic media. Geophysical Journal International170, 44–80.
    [Google Scholar]
  12. NewmanG.A.1994. A study of downhole electromagnetic sources for mapping enhanced oil recovery processes. Geophysics59, 534–545.
    [Google Scholar]
  13. PellerinL. and HohmannG.W.1995. A parametric study of the vertical electric source. Geophysics60, 43–52.
    [Google Scholar]
  14. SchollC. and EdwardsR.N.2007. Marine downhole to seafloor dipole‐dipole electromagnetic methods and the resolution of resistive targets. Geophysics72, WA39–WA49.
    [Google Scholar]
  15. SchwalenbergK., HaeckelM., PoortJ. and JegenM.2010. Evaluation of gas hydrate deposits in an active seep area using marine controlled source electromagnetics: Results from Opouawe Bank, Hikurangi Margin, New Zealand . Marine Geology272, 79–88.
    [Google Scholar]
  16. SørensenK.I. and ChristensenN.B.1994. The fields from a finite electrical dipole – A new computational approach. Geophysics59, 864–880.
    [Google Scholar]
  17. SpiesB.R. and FrischknechtF.C.1991. Electromagnetic sounding. In: Electromagnetic Methods in Applied Geophysics (ed. N.M.Nabighian ), pp. 285–425. SEG.
    [Google Scholar]
  18. StrackK.M.1992. Exploration with Deep Transient Electromagnetics . Elsevier.
    [Google Scholar]
  19. StreichR.2009. 3D finite‐difference frequency‐domain modeling of controlled‐source electromagnetic data: Direct solution and optimization for high accuracy. Geophysics74, F95–F105.
    [Google Scholar]
  20. WannamakerP.E., HohmannG.W. and SanFilipoW.A.1984. Electromagnetic modeling of three‐dimensional bodies in layered earths using integral equations. Geophysics49, 60–74.
    [Google Scholar]
  21. WardS.H. and HohmannG.W.1987. Electromagnetic theory for geophysical applications. In: Electromagnetic Methods in Applied Geophysics (ed. N.M.Nabighian ), pp. 131–311. SEG.
    [Google Scholar]
  22. WeideltP.2007. Guided waves in marine CSEM. Geophysical Journal International171, 153–176.
    [Google Scholar]
  23. WeitemeyerK.A., ConstableS.C., KeyK.W. and BehrensJ.P.2006. First results from a marine controlled‐source electromagnetic survey to detect gas hydrates offshore Oregon. Geophysical Research Letters33, L03304.
    [Google Scholar]
  24. ZachJ.J. and BrautiK.2009. Methane hydrates in controlled‐source electromagnetic surveys – analysis of a recent data example. Geophysical Prospecting57, 601–614.
    [Google Scholar]
  25. ZiolkowskiA., HobbsB.A. and WrightD.2007. Multitransient electromagnetic demonstration survey in France. Geophysics72, F197–F209.
    [Google Scholar]
http://instance.metastore.ingenta.com/content/journals/10.1111/j.1365-2478.2010.00926.x
Loading
Electromagnetic fields generated by finite‐length wire sources: comparison with point dipole solutions
Geophysical Prospecting 59, 361 (2011); https://doi.org/10.1111/j.1365-2478.2010.00926.x
/content/journals/10.1111/j.1365-2478.2010.00926.x
/content/journals/10.1111/j.1365-2478.2010.00926.x
Loading

Data & Media loading...

  • Article Type: Research Article
Keyword(s): Electromagnetics; Mathematical formulation; Modelling; Numerical study

Most Cited This Month Most Cited RSS feed

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error