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CPGEDepartment Seminar, Apr 18, 2011
Petroleum and Geosystems Engineering
The University of Texas at AustinAustin, TX
How the pore scale affects the field scale: Real world examples
David A. DiCarlo
CPGEDepartment Seminar, Apr 18, 2011
Acknowledgments
Stanford UniversityAkshay SahniMartin Blunt
University of TexasHassan Dehghanpour
Behdad AminzadehMohammad Mirzaei
CPGEDepartment Seminar, Apr 18, 2011
Variety of flow scales
Continuum ScalePore Scale Field Scale
GasOil
CPGEDepartment Seminar, Apr 18, 2011
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
CPGEDepartment Seminar, Apr 18, 2011
NAPL
Water
Three-phase (gas, oil, water) flow
Essential component of oil recovery or aquifer remediation
GasOil
Oil recovery by gas injection Leaking gasoline
Key parameters: Residual oil (Sor) and flow speed (kro)
CPGEDepartment Seminar, Apr 18, 2011
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
CPGEDepartment Seminar, Apr 18, 2011
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
CPGEDepartment Seminar, Apr 18, 2011
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
CPGEDepartment Seminar, Apr 18, 2011
9
Experimental Set-up
Oil phase N-octane, Aqueous phase 10 wt % NaBr , Gas phase Air
Vertical Positioning System
Effluent
Gas Invades the System
CPGEDepartment Seminar, Apr 18, 2011
Long time saturation vs position and time – initial experiments
0
0.1
0.2
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0 20 40 60 80 100
z (cm from the top)
Oil
Sat
ura
tio
n
initial
5 hours
22 hours
46 hours
4 days
9 days
25 days
CPGEDepartment Seminar, Apr 18, 2011
Calculating Relative Permeabilities
ui = -(K/) kr(Si) Pi/x
To directly measure the relative permeability of a phase you need
• The fluid saturation - Si
• The flux - ui
• The pressure gradient - Pi/x
CPGEDepartment Seminar, Apr 18, 2011
Saturation vs Position and Time
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
0 20 40 60 80 100
z (cm from the top)
Oil
Sat
ura
tio
n
initial
5 hours
22 hours
46 hours
4 days
9 days
25 days
oil moved saturation
CPGEDepartment Seminar, Apr 18, 2011
Measured Relative Permeability Can measure
relative permeability over 6 orders of magnitude
Measure with different wettabilities
Measure with different initial states
CPGEDepartment Seminar, Apr 18, 2011
Oil Permeability Remains Finite to Low Saturations
Oil relative permeability depends on wettability
CPGEDepartment Seminar, Apr 18, 2011
Oil trapping after waterflood
solidgrain
water
trappedoil
CPGEDepartment Seminar, Apr 18, 2011
No oil trapping after gasflood
oillayers
gas
CPGEDepartment Seminar, Apr 18, 2011
Oil remains mobile to very low saturations
Water becomes immobileat around Sw = 0.1
Oil and water are not interchangeable
CPGEDepartment Seminar, Apr 18, 2011
Fluids on water-wet and oil-wet surfaces
gw
ow
gogo
gas
water-wet surface
oil
water
gw
ow
gowater
oil
gasgw
oil-wet surface
Oil spreads on water
Water beads on oil
CPGEDepartment Seminar, Apr 18, 2011
Fluids in pore corners
Oil layers at low So Oil cannot be
trapped
go
ow
oil gas
water
ow
gas
gw
water
oil
water-wet corner oil-wet corner
No water layers!Water can be
trapped
CPGEDepartment Seminar, Apr 18, 2011
Layers Show up at Low Sat
All oil in layers
q ~ r4
So ~ A~ r2
kro ~ So2
go
ow
oil gas
water
CPGEDepartment Seminar, Apr 18, 2011
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 ?????
CPGEDepartment Seminar, Apr 18, 2011
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
CPGEDepartment Seminar, Apr 18, 2011
Thanks for your attention!