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Numerical simulations of the transient electrokinetic response of finely layered porous media

Numerical simulations of the transient electrokinetic response of finely layered porous media Michel DIETRICH (1) & Florence DELPRAT-JANNAUD (2) (1) Formerly IFPEN, Rueil Malmaison, France, now at Univ. Joseph Fourier, Grenoble, France (2) IFPEN, Rueil Malmaison, France.

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Numerical simulations of the transient electrokinetic response of finely layered porous media

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  1. Numerical simulations of the transient electrokinetic response of finely layered porous media Michel DIETRICH (1) & Florence DELPRAT-JANNAUD (2) (1) Formerly IFPEN, Rueil Malmaison, France, now at Univ. Joseph Fourier, Grenoble, France (2) IFPEN, Rueil Malmaison, France IFPEN Pore2Field Symposium, 16–18 November 2011 1 1

  2. Motivations • New tools are needed for the detection, characteri-zation and monitoring of fluids in underground reservoirs • Electrokinetic effects in fluid-filled porous or fractured media can reconcile the high resolving powerof seismic prospecting techniques with the sensitivity of EM exploration methods to fluids • The combination of seismic and electroseismic (or seismoelectric) measurements is likely to bring new and unique information on reservoir fluids • Modeling plays an important role in the development of “electrokinetic geophysics” IFPEN Pore2Field Symposium, 16–18 November 2011 2 2

  3. Outline • Overview of electrokinetic geophysics • Coseismic effects • Electrical double layer model • Interface response • Summary of publication history from the 1930s onwards • Numerical simulations of the coupled seismic and electromagnetic wave propagation in fluid-filled porous media • Governing equations and numerical schemes • Near-surface simulations • Thin layers IFPEN Pore2Field Symposium, 16–18 November 2011

  4. A simple (seismoelectric) experiment in the field Amplitude Spectrum IFPEN Pore2Field Symposium, 16–18 November 2011 4 4

  5. Field observations – 1a (Garambois & Dietrich, Geophysics 2001) IFPEN Pore2Field Symposium, 16–18 November 2011 5 5

  6. Air Gun Air Gun Field observations – 1b SEMM test site (Vesdun-en-Berry) 18 horizontal geophones & 17 electric dipoles (1 m aperture) 5 m 54,5 m Seismic recording Seismo-electric recording 0 0 0.1 0.1 Time(s) Time (s) 0.3 0.3 0.4 0.4 Stack 300 (after notch filtering) IFPEN Pore2Field Symposium, 16–18 November 2011 6 6

  7. Electrical double layer model (Helmholtz, 1853; Gouy, 1909; Chapman, 1913; Stern, 1924) IFPEN Pore2Field Symposium, 16–18 November 2011 7 7

  8. Bell shape of amplitude response  First Fresnel zone shows dipole radiation Seismo-electromagnetic conversion at an interface IFPEN Pore2Field Symposium, 16–18 November 2011 8 8

  9. Electric Seismic Field observations – 2c Accelerated weight-drop source (CGGVeritas) 50 Hz noise 9

  10. Electric Electric Seismic Seismic Field observations – 2d 5003 – 5040 records 'H' filtered and stacked Close-up view IFPEN Pore2Field Symposium, 16–18 November 2011 10

  11. Bibliographic review of electroseismic wave phenomena Pride (1994) Thompson & Gist (1993) Pride & Morgan (1991) Frenkel (1944) Thompson (1936) Blau & Statham (1936) 11 11

  12. Governing equations in porous media (Pride, 1994) IFPEN Pore2Field Symposium, 16–18 November 2011 12 12

  13. Layered model parameters IFPEN Pore2Field Symposium, 16–18 November 2011 13 13

  14. SKBP Fortran code Coupled seismoelectromagnetic wave propagation in fluid-saturated porous media (Garambois & Dietrich, JGR 2002) Based on the electroseismic wave theory of Pride (1994) Written for point sources (3D radiation) in layered media Uses the generalized reflection and transmission matrix method (Kennett & Kerry, 1979) Times series computed via the discrete wavenumber method (Bouchon, 1981) Can handle surface-to-surface, surface-to-borehole, borehole-to-surface, and borehole-to-borehole source / receiver configurations IFPEN Pore2Field Symposium, 16–18 November 2011 14 14

  15. Modeling – 1 EM-wave Slow P-wave S-wave Fast P-wave VPf1 = 1935 m/s VPs1 = 87 m/s VS1 = 545 m/s VEM1 = 4 518 245 m/s VPf2 = 2430 m/s VPs2 = 4 m/s VS2 = 953 m/s VEM2 = 3 768 806 m/s QPf1 = 1772 QPs1 = 0.5 QS1 = 804 QEM1 = 0.5 QPf2 = ∞ QPs2 = 0.5 QS2 = ∞ QEM2 = 0.5 Rho1 = 2120 kg/m³ Rho2 = 2280 kg/m³ Bulk densities IFPEN Pore2Field Symposium, 16–18 November 2011 15

  16. Modeling – 2 P-P P-P P-S P-S P-EM P-EM P-P P-S IFPEN Pore2Field Symposium, 16–18 November 2011 16

  17. Modeling – 3 IFPEN Pore2Field Symposium, 16–18 November 2011 17

  18. Electric Electric Seismic Seismic Modeling – 4 } } EM wave dispersion in shallow subsurface IFPEN Pore2Field Symposium, 16–18 November 2011 18

  19. Seismo-electric response of a thin layer – 1 Intercalation of a thin layer whose thickness d << λP Electric field Ex / 2 layers Electric field Ex / 3 layers (Pride & Garambois, 2005) IFPEN Pore2Field Symposium, 16–18 November 2011 19 19

  20. Seismo-electric response of a thin layer – 2 Possibly strong effect on converted EM wave No visible effect on seismograms Vertical displacement uz Ex amplitude of converted wave P-EM (Pride & Garambois, 2005) IFPEN Pore2Field Symposium, 16–18 November 2011 20 20

  21. Seismo-electric response of a thin layer – 3 Modifying the layer thickness [ 1 to 800 cm] for k = 10-17 m2 Modifying the permeability contrast [ 5 10-19 to 5 10-14 m2] for d = 50 cm EM Ampl. X 10 EM Ampl. X 10 Ratio ~40 EM Ampl. X 1 EM Ampl. X 1 IFPEN Pore2Field Symposium, 16–18 November 2011 21 21

  22. Concluding remarks • Seismo-electric recordings are sensitive to the microstructure and fluid properties of porous or fractured media. They can potentially be used to estimate medium parameters not detected neither with (high resolution) seismic methods nor with conventional electric or electro-magnetic techniques. • Seismo-electric phenomena in layered structures are reasonably well understood, but field data recorded in highly heterogeneous structures show a great complexity which calls for advanced 2D and 3D modeling techniques. “Super-resolution” of thin layers still requires investigations. • Real data recorded over moderately deep targets (few hundred meters) are critically needed to confront observations with theory and numerical simulations. IFPEN Pore2Field Symposium, 16–18 November 2011 22 22

  23. Acknowledgements Part of this work was performed in collaboration with CGGVeritas. We are grateful to Simon Spitz, Baptiste Rondeleux (CGGV), Patrick Meynier, Patrice Ricarte, Mathilde Adelinet, Marc Fleury, Brigitte Doligez and Martine Ancel (IFPEN) fortheir various contributions in the course of this work. The financial support of IFPEN’s "Resource" Business Unit is gratefully acknowledged. IFPEN Pore2Field Symposium, 16–18 November 2011

  24. Postscript on coupling phenomena …… And the four winds, that had long blown as one Shone in my ears the light of sound Called in my eyes the sound of light …… ―Dylan Thomas, “From love’s first fever to her plague” (1933) (Cited by Lawrence A. Crum in a paper on sonoluminescence) IFPEN Pore2Field Symposium, 16–18 November 2011 24

  25. Underground reservoirs and fluids • Joint interpretation of reflection seismics & CSEM surveys • EMGS (Seabed logging): founded in 2002 • Offshore Hydrocarbon Mapping (OHM): founded in 2002 EMGS documents IFPEN Pore2Field Symposium, 16–18 November 2011 26

  26. Breakdown of contributions in the “modern age”of electrokinetic geophysics (1990 – 2010) IFPEN Pore2Field Symposium, 16–18 November 2011 27 27

  27. Field observations – 2a The electroseismic effect “…The time of arrival suggests that the ES pulse is generated by the seismic wave at some depth between the shot and surface and is transmitted from that level at high speed, probably as an electromagnetic wave…” (Martner & Sparks, 1959) IFPEN Pore2Field Symposium, 16–18 November 2011 28

  28. Field observations – 2a [ Neishtadt, Eppelbaum & Levitski (2006) ] IFPEN Pore2Field Symposium, 16–18 November 2011 29 29

  29. Field observations – 2b (Garambois & Dietrich, Geophysics 2001) IFPEN Pore2Field Symposium, 16–18 November 2011 30 30

  30. Transfer functions of co-seismic effects – 1 (Garambois & Dietrich, Geophysics 2001) IFPEN Pore2Field Symposium, 16–18 November 2011 31 31

  31. Transfer functions of co-seismic effects (Garambois & Dietrich, 2001) IFPEN Pore2Field Symposium, 16–18 November 2011 32 32

  32. Trench experiment – 1 Haines & Guitton Recording of interface response BEFORE co-seismic energy in transmission mode at the surface. IFPEN Pore2Field Symposium, 16–18 November 2011 33

  33. Trench experiment – 2 Electric dipoles Trench Haines & Guitton Impact points IFPEN Pore2Field Symposium, 16–18 November 2011 34

  34. Trench experiment – 3 Transmission mode  Reflection mode before/after signal processing  Haines & Guitton IFPEN Pore2Field Symposium, 16–18 November 2011 35

  35. Seismoelectric or electroseismic? – 1 Waveform design for electroseismic exploration Construction of a low frequency coded waveform by switching between phases of a three-phase power supply (Hornbostel & Thompson, Geophysis 2007) IFPEN Pore2Field Symposium, 16–18 November 2011 36 36

  36. Seismoelectric or electroseismic? – 2 Electromagnetic-to-seismic conversion: a new direct hydrocarbon indicator (Thompson, Sumner & Hornbostel, TLE 2007) IFPEN Pore2Field Symposium, 16–18 November 2011 37 37

  37. Computed wavefields Point source excitation 2 wave systems: PSVTM: Ux, Uz, Wz, Ex, Hy SHTE: Uy, Ey, Hx IFPEN Pore2Field Symposium, 16–18 November 2011 38 38

  38. Sensitivity of EM waves (Garambois & Dietrich, JGR 2002) IFPEN Pore2Field Symposium, 16–18 November 2011 39 39

  39. Future prospects and investigations • Further study of the role of Biot slow waves in the interface response • Response of highly heterogeneous reservoir structures • Seismo-electric and electroseismic waveforms • Electroseismic measurements: development of powerful low-frequency EM sources • Reciprocity of seismo-electric and electroseismic mesurements (nonlinear responses?) • Borehole electrokinetic measurements IFPEN Pore2Field Symposium, 16–18 November 2011 40 40

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