How the pore scale affects the field scale: Real world examples

1. How the pore scale affects the field scale: Real world examples David A. DiCarlo Petroleum and Geosystems Engineering The University of Texas at Austin Austin, TX Department Seminar, Apr 18, 2011

2. Acknowledgments University of Texas Hassan Dehghanpour Behdad Aminzadeh Mohammad Mirzaei Stanford University Akshay Sahni Martin Blunt Department Seminar, Apr 18, 2011

3. Gas Oil Variety of flow scales Pore Scale Continuum Scale Field Scale Department Seminar, Apr 18, 2011

4. Interests and motivation • The configuration of fluids at the pore-scale controls flow and transport at field scales • Three-phase (gas, oil, water) flow • Preferential flow • Unsaturated flow in fractures • In-situ measurements of pore filling • Fluid-fluid interfacial area in porous media • Continuum and discrete formulations of flow Department Seminar, Apr 18, 2011

5. NAPL Gas Water Oil Three-phase (gas, oil, water) flow • Essential component of oil recovery or aquifer remediation Leakinggasoline Oil recovery by gas injection Key parameters: Residual oil (Sor) and flow speed (kro) Department Seminar, Apr 18, 2011

6. Prudhoe Bay’s extra oil • At best, only 50% of the original oil in a reservoir is recovered by a waterflood • Prudhoe Bay’s eventual recovery will be over 70%! (>$100 B difference) • Why? • Prudhoe Bay is the world’s largest gas injection operation Department Seminar, Apr 18, 2011

7. Objectives • Understand at a basic physical level why high recoveries are possible for three-phase flow • Develop a quick method to measure three-phase relative permeability (normalized recovery rate) • Systematically measure three-phase relative permeability as a function of wettability and saturation history Department Seminar, Apr 18, 2011

8. Experimental set-up • Create 1m long sandpacks with varying degrees of wettability • Fill sandpacks with oil and water, then open the bottom and let drain out • Use dual-energy computed tomography (CT) to measure the saturation of each phase versus position and time Department Seminar, Apr 18, 2011

9. Experimental Set-up Vertical Positioning System Gas Invades the System Effluent Oil phase  N-octane, Aqueous phase  10 wt % NaBr , Gas phase  Air 9 Department Seminar, Apr 18, 2011

10. Long time saturation vs position and time – initial experiments Department Seminar, Apr 18, 2011

11. Calculating Relative Permeabilities • ui = -(K/m) kr(Si)DPi/Dx • To directly measure the relative permeability of a phase you need • The fluid saturation - Si • The flux - ui • The pressure gradient - DPi/Dx Department Seminar, Apr 18, 2011

12. Saturation vs Position and Time saturation oil moved Department Seminar, Apr 18, 2011

13. Measured Relative Permeability • Can measure relative permeability over 6 orders of magnitude • Measure with different wettabilities • Measure with different initial states Department Seminar, Apr 18, 2011

14. Oil Permeability Remains Finite to Low Saturations • Oil relative permeability depends on wettability Department Seminar, Apr 18, 2011

15. Oil trapping after waterflood solid grain water trapped oil Department Seminar, Apr 18, 2011

16. No oil trapping after gasflood gas oil layers Department Seminar, Apr 18, 2011

17. Oil and water are not interchangeable Oil remains mobile to very low saturations Water becomes immobile at around Sw = 0.1 Department Seminar, Apr 18, 2011

18. g g w w t r a e g a s g q g g o w g i l o o w i l - w t r f o e s u a c e Fluids on water-wet and oil-wet surfaces g a s g g g o q o i l g w g o g w a t e r o w w a t e r - w e t s u r f a c e Water beads on oil Oil spreads on water Department Seminar, Apr 18, 2011

19. q g o q o w b g a s i l o w t r a e No water layers! Water can be trapped Fluids in pore corners q Oil layers at low So Oil cannot be trapped g w q o w b g a s w t r a e i l o water-wet corner oil-wet corner Department Seminar, Apr 18, 2011

20. All oil in layers q ~ r4 So ~A~ r2 kro ~ So2 q g o q o w b g a s i l o w t r a e Layers Show up at Low Sat Department Seminar, Apr 18, 2011

21. Current work – Three Phase • Comparing results to Stone and saturated average three-phase permeability models • Can possibly fit by changing the residuals • Extending reconnection work to different wettabilities • Measure pressures, and do with real rock cores and CO2 • ????? Department Seminar, Apr 18, 2011

22. Interests and motivation • The configuration of fluids at the pore-scale controls flow and transport at field scales • Three-phase (gas, oil, water) flow • Preferential flow – flow at frontal interfaces • Unsaturated flow in fractures • In-situ measurements of nano-particles • Surfactant imbibition into oil-wet media • Continuum and discrete formulations of flow Department Seminar, Apr 18, 2011

23. Thanks for your attention! Department Seminar, Apr 18, 2011