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Seismic stimulation for enhanced oil production

Seismic stimulation for enhanced oil production. Eirik G. Flekkøy, University of Oslo. Mihailo Jankov, Olav Aursjø, Henning Knutsen, Grunde Løvoll and Knut Jørgen Måløy, UiO Renaud Toussaint, Universite Louis Pasteur de Strasbourg Steve Pride, Lawrence Berkeley Labs. Outline.

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Seismic stimulation for enhanced oil production

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  1. Seismic stimulation for enhanced oil production Eirik G. Flekkøy, University of Oslo Mihailo Jankov, Olav Aursjø, Henning Knutsen, Grunde Løvoll and Knut Jørgen Måløy, UiO Renaud Toussaint, Universite Louis Pasteur de Strasbourg Steve Pride, Lawrence Berkeley Labs

  2. Outline • Field observations • Pore scale intro and elements of theory • Lattice Boltzmann and experiments • Moving up from pore scale: Network models and experiments • Transversal versus longitudinal stimulation • Effects of compressibility

  3. OilCut OilCut Oil Production(B/day) Oil Production(B/day) Oil cut % Oil cut % Oil Production Oil Production stimulation applied stimulation applied Increase in Oil Production after Stimulation at Occidental’s Elk Hills Field, California Increase in Oil Production after Stimulation at Occidental’s Elk Hills Field, California FIELD EVIDENCE FOR SEISMIC STIMULATION • Earthquakes or hammers, as in this case: FIELD EVIDENCE FOR SEISMIC STIMULATION

  4. Water extraction wells:

  5. Context: As much as 70% of the world’s oil is in known reservoirs but is trapped on capillary barriers and is effectively “stuck”. Seismic Stimulation: A seismic wave is to “shake the stuck oil loose” and get it flowing again toward a production well.

  6. Lattice Boltzmann model • Hydrodynamics comes from mass- and momentum conservation: G. McNamara and G. Zanetti 1986

  7. Lattice-Boltzmann Movie • NOTES • No green arrow = • no applied forcing • Single green arrow = • production-gradient only • Double green arrow = • two periods of seismic stress • + production-gradient • “when stimulation is applied, bubbles coalesce creating a longer stream of oil that flows even in absence of stimulation”

  8. Snapshots and average oil speed during the four stages of a typical “production run”: running average

  9. A tiny experiment:

  10. Lattice Boltzmann and experiments

  11. n The condition for a stuck oil bubble: “the production pressure drop along the bubble is just balanced by a capillary-pressure increase” Beresnev et al., 2005

  12. The production-gradient force that always acts on the fluids: Poroelasticity determines the seismic force acting on the fluids: “acceleration of grains” “wavelength-scale fluid-pressure gradient” where is the seismic strain rate.

  13. The seismic force adds to the production gradient and can overcome the capillary barrier whenever: “stimulation criterion” where dimensionless “stimulation number” (a type of capillary number) “criticalthreshold of stimulation number” (purely geometry dependent) and where k is permeability and f is porosity.

  14. Six different realization of same porosity:

  15. Total volume of oil production with (solid symbols) and without (open symbols) three cycles of stimulation applied (Fs = Fo): Less of a stimulation effect because at 33% saturation, oil cannot form a continuous stream across system. More of a stimulation effect because at 50% saturation, coalescence can result in oil forming a continuous stream across system

  16. Towards larger scales: Experiments:

  17. Displacement structures depend on velocity and viscosities and gravity:

  18. Experimental setup:

  19. Experiment movie- no oscillations

  20. Experiment, parallel oscillations a=0.8 g

  21. Parallel oscillations with a=2.6 g

  22. Corresponding network simulations: • a=1.0 g f= 10Hz

  23. ..and with transverse oscillations: • a=1.0 g f=10Hz

  24. The different frequencies and accelerations: • No oscillations • Parallel osc: • Transverse osc:

  25. Lattice Boltzmann • Longitudinal and transverse oscillations

  26. Resulting, end saturations of wetting fluid:

  27. 20 cm 35 cm An experiment with compressibility: Q=const.

  28. Linear elastic response of both air and local plate displacements may model fluid compressibility under much higher pressures.

  29. Elastic response gives finite skin-depth: Diffusion equation D For damped oscillations:

  30. Results 4.0 Hz Flow direction 0.9 Hz 0.2 Hz Pressure amplitude (Pa) low high

  31. Frequency (Hz) Amplitude (Pa) Phase diagram 2

  32. Closer look Fragments Coexistence of both phases in pore spaces-foam

  33. Conclusions • Transverse stimulation more efficient than parallel stimulation, at least for high fractions of invading fluid • Smaller scale coalescence potentially more efficient at higher volume fractions • Compressibility gives skin-depth stimulation range depends on frequency. • Simplified (network) and 2D simulations (Lattice Boltzmann) capture experiments • Quantification, analysis and scaling laws still lacking

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