WHAT ARE THE DIFFERENCES BETWEEN
“HOMOGENEOUS and FRACTURED RESERVOIRS?
•Fracture network controls the flow due to high k.
•Matrix stores most of the oil due to high
•Frontal advance theory may not be applicable.
•Matrix-fracture interaction is the main cause of HC production
Tayfun Babadagli, PhD, PEng
Short Course - EOR
File-12
2
ELEMENTS OF NATURALLY FRACTURED
RESERVOIR MANAGEMENT
Characterization Reservoir dynamics
Matrix
Fracture
Core
Well test
Well logs
Outcrop
Matrix
effect
Fracture
effect
“Monitoring”
performance
EOR
Most proper
method
Experiment
(Scaling)
Numerical
simulation
3
“HOMOGENEOUS” SYSTEMS
Swept Zone
Unswept Zone
I
I
P
I
I
WATER
BREAKTHROUGH
WATER
PRODUCTION
I : INJECTION WELL
P : PRODUCTION WELL
Unrecovered oil can be in pores, never swept (not residual oil!!!!)
OR it can be in pores swept (residual oil!!!!)
Tayfun Babadagli, PhD, PEng
Short Course - EOR
File-12
4
FRACTURED SYSTEMS
•
UNSWEPT AREA: Channeling
Tayfun Babadagli, PhD, PEng
Short Course - EOR
File-12
5
EOR MECHANISMS in NFRs
• Fracture Recovery – Viscous Flow
• Matrix Recovery – Capillarity and Mass Transfer
– Gravity Drainage
– Capillary Imbibition
– Convection
– Diffusion
Tayfun Babadagli, PhD, PEng
Short Course - EOR
File-12
6
OIL AND WATER
OIL
a
X
x
Magnitude of gravity
WATER
Magnitude of capillarity
ko a ( w o ) g Pc
qi
o
a
7
CONVECTION AND DIFFUSION
CONVECTION
•Result of contrasting oils within the fracture network
•Large times are needed to see the effect of convection
•High vertical permeability (fractures) accelerates
•Oil at the crest is heavier than the base.
•Vertical fractures provide communication for convection
DIFFUSION
•Contrast in HC properties between fracture and matrix
8
OIL-WATER : FULLY IMMERSED IN WATER
OIL
Z
H-Z
Height of the water front in the
block above the bottom
H
Z
x
u
WATER
Pc g ( H Z )
w
kk rw
[ MH (1 M ) Z ]
High H and small Z Gravity dominates
Water wettability is small Gravity dominates
9
WATER
WATER
WATER
WATER
x, Core Length (vertical)
min.
66 min.
99 min.
min.
12
12min.
min.
15
min.
15 min.
1
6 min.
30 min.
0
Tayfun Babadagli, PhD, PEng
20
40
60
80
100
Sw , Average
Short Course - EOR
File-12
10
OIL
WATER
WATER
WATER
33min.
min.
x, Core Length (vertical)
OIL
OIL
18 min.
18
min.
WATER
OIL
30min.
min.
30
day
11 day
1
3 min
80 min.
00
Tayfun Babadagli, PhD, PEng
20
40
60
80
100
Sw , Average
Short Course - EOR
File-12
11
OIL RECOVERY IN NATURALLY FRACTURED
RESERVOIRS
Capillary Imbibition Transfer at Static Conditions,
i.e. No Flow of Water in Fracture
Berea Sandstone
Heavy Crude Oil-Brine
Indiana Limestone
Light Crude Oil -Brine
PROBLEM
Matrix recovery by capillary imbibition is not
EFFECTIVE if
• IFT is high
• Unfavorable matrix boundary conditions
restricting the contact of matrix and water in
fracture exist
• Matrix is oil-wet
and
• OIL VISCOSITY IS HIGH
SOLUTION
(Babadagli, Coll. And Surface A: Phys. And Eng. Asp., 2003 – SPE 69564)
SURFACTANT, POLYMER, HOT WATER INJECTION
to reduce IFT and oil viscosity
or to increase water viscosity
or to overcome unfavorable matrix boundary conditions
and oil wettability
or to have additional recovery mechanisms
?
OBJECTIVE
EXPERIMENTATION AT STATIC CONDITIONS
• Most proper EOR method (injection fluid)
• Scaling to reservoir scale
?
PART I-A
SELECTION OF EOR METHODS
Which method (EOR fluid) yields the most
effective recovery methods
for
different boundary conditions, oil type, IFT, oil
viscosity, wettability.
Polymer (0.1 wt %), k=128 mD
Surfactant (1 vol %), k=19 mD
Heat (40 C), k=1 mD
Temp. increased from 40 to 80 C
37
(Babadagli, Coll. And Surface A: Phys. And Eng. Asp., 2003 – SPE 69564)
Tayfun Babadagli, PhD, PEng
Short Course - EOR
File-12
SELECTION CRITERIA
SANDSTONES
- Light oils: no surfactant. Especially for unfavorable BC.
- Heavy oils: surfactant is desirable. Especially for
unfavorable BC.
- Light oils: polymer is not desirable. For all BCs.
- Heavy oils: polymer is desirable. Especially for
unfavorable BC.
- Thermal is effective to fasten light oil recovery but not
for ultimate recovery.
- Thermal is effective to fasten heavy oil recovery and for
ultimate recovery.
SELECTION CRITERIA
CARBONATES
- They all good!
- Thermal > surfactant > polymer > brine.