ENHANCED OIL RECOVERY PROCESSES docx

Reservoir Engineering Courses – K. Madaoui - 2004
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Reservoir Engineering Courses – K. Madaoui - 2004
ENHANCED OIL RECOVERY PROCESSES
CONTENTS
-1-INTRODUCTION
EOR world potential-
-2-THERMAL PROCESSES
-
Steam injection –Air injection
-3-CHEMICAL METHODS

-Polymers and Surfactants
-4-GAS INJECTION as a promising EOR process
-
Specificities,Mechanisms,Efficiencies,Selection criteria,Ratios,Methodology to
conduct a GI project
-5-CONCLUSIONS: EOR vs R&D
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Reservoir Engineering Courses – K. Madaoui - 2004
Typical Oil Field Performances
Time Years
Field Oil Rate
Aband.
Rate
WATER-CUT
NATURAL
DEPLETION
(30%)
WATER
INJ.

(+ 15%)
N
P
DN
P
Diagnosis
3
rd
TYPE
EOR
(+
10%)
IRM (+
5%)
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Ultimate Reserves and Recovery mechanism sequence
N
pu
=N
1
+N
2
+N
3
at economical abandonment conditions
=N
1
+(N
i

-N
1
)[E
d
xE
vol
]
water
+(N
i
-N
1
-N
2
)[E
d
xE
vol
]
gas
How to optimise N
pu
?How to combine N
1
,N
2
,N
3
?
Main parameters?

N
1
(nat.depl.) :identification-limitations-duration
N
2
(water inj.) :limitations-implementation-duration
N
3
(EOR) :process selection-implementation
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Tertiary Recovery Objectives
PRODUCE-ECONOMICALLY- PART OF OIL LEFT BY
CONVENTIONAL RECOVERY METHODS
– Improvement of displacement efficiency
decreasing Sorw
miscible or near miscible gas injection
chemical flood-surfactants
increasing gravity forces
oil vaporization
– Improvement of volumetric sweep efficiency
lowering mobility ratio by increasing m
w
chemical flood - polymers
reducing m
o
thermal flood
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Microscopic and Volumetric Sweep Efficiencies

Example of Five Spot Injection Pattern-
Cross section
Water flooded zone - Intermediate status Water flooded zone - Final status
Injector Producer
Injectors
Producers
Soi
Sorw
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Pore Level Mechanisms - Microscope Efficiency
· Competition between viscous and capillary forces capillary number:
· Competition between gravity and capillary forces Dombrowski
Brownwell number:
1.0
0.5
0.0
10
-6
10
-4
10
-2
10
0
Capillary number, N
c
Microscopic displacement eff., Em
WATER-WET
SYSTEMS

PORE SIZE DIST'N
WIDE
AVERAGE
NARROW
s
m
U
N
c
=
s
Dr
gk
N
b
=
E
m
for N
b
> 10
-5
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Water Injection Efficiency
Water-flood efficiency = Areal sweep efficiency
x Vertical sweep efficiency
xDisplacement efficiency
Limitations: Ed<1
Eareal<1

Evertical<1
f(pattern,mobility ratio)
vs.layer contrast
Sorw = 0
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Limitations of conventional methods-
Recovery by conventional methods=
Natural depletion +Water injection recovery
=N
1
+N
2
=N
1
+(N
i
-N
1
)xEdispl.XEvol.
Ed= Oil left in swept zones
Evol<1 ~0.4 to 1 Oil left in unswept zones
S
oi
-S
orw
1-S
wi
<1 ~60%
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Reservoir Engineering Courses – K. Madaoui - 2004
Enhanced Oil Recovery Methods
Enhanced Oil Recovery
IMPROVEMENT OF
VOLUMETRIC
EFFICIENCY Evol
IMPROVEMENT OF
DISPLACEMENT
EFFICIENCY Ed
INCREASE WATER
VICOSITY
OIL VISCOSITY
REDUCTION
REDUCE INTERFACIAL
TENSION
INCREASE
GRAVITY FORCES
OIL
VAPORIZATION
HEAVY OIL
STEAM INJECTION
IN-SITU COMBUSTION
POLYMER
SURFACTANT
GAS INJECTION
MISCIBLE NEAR MISCIBLE
HC,CO2,N2,AIR,…
Lean gas injection
(HC,N2,CO2,AIR, )
Stable displacement

IMMISCIBLE LEAN
GAS INJECTION
STEAM INJ.(LIGHT OIL)
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Production Mechanisms
Mechanism
I- Oil reservoirs
Natural depletion only
ND+Water depletion
ND+WI+Enhanced oil
recovery
II- Gas reservoirs
Natural depletion
Order of magnitude of
recovery factor
5 to 20 %OOIP
30 to 50 %OOIP
50 - 65 %OOIP
60 - 90 % OGIP
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EOR contribution in the world oil production
ESTIMATION* YEAR 2000
THERMAL 1.0 to 1.5 MMstb/d
CHEMICAL 0.3 to 0.7 MMstb/d
GAS INJECTION 3.5 to 4.5 MMstb/d
EOR PRODUCTION 5 to 7 MMstb/d(
out of more than 70MMstb/d)
(*from 1995 data+personal extrapolation)

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World Oil reserves estimates( P.R.Bauquis-2000-)
-Conventional reserves ( billion stb )
Initial 1800 to 2500
Cumulative production 800 800
Remaining to be produced 1000 to 1700
-Non conventional reserves
(economically recoverable at year 2030 horizon)

Deep offshore(below 500m water depth) 100 100
Ultra heavy oil(50/50 Orinoco and Athabasca) 600 600
GasToLiquids conversion 100 100
-Overall reserves 1800 to 2500
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TENTATIVE ESTIMATE of EOR POTENTIAL
YEAR 2000 ROUGH WORLD RESERVE‘’GUESTIMATE’’
CONVENTIONAL RESERVES *: 1000 billion stb
(for an initial oil in place of >3500billion stb)

1% recovery factor improvement~35 billion stb !
UNCONVENTIONAL RESERVES:
Deep offshore:100 billion stb
Heavy oil :600 billion stb
*onshore+offshore( less than 300 meters water depth)
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TENTATIVE ESTIMATE of EOR POTENTIAL
CASE of MATURE or AGEING OIL FIELDS

(more than 20 years old and/or in declining phase)
-75% of the conventional reserves located in mature fields
-70% of the world production from fields of >20years
old,majority of them started their decline phase(generally
increasing water-cut)
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ENHANCED OIL RECOVERY
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Heavy oils
q
oi
=
m
o
B
o
[Lnr
e
/r
w
+s-0.75]
a k
a
k
ro
(S
wi+g

) h
x (P
r
-P
wf
) = PIx (P
r
-P
wf
)


High viscosity Low PI Low or Uneconomical oil rate
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F Methods:Increase reservoir temperature
Steam Injection
In-situ Combustion
F Effect
Reduction of oil viscosity due to heating effect
Thermal Flood
Fundamentals of Reservoir Engineering
HEAVY OIL(°API<20-25)=HIGH VISCOSITY(10 to > 10
6
cpo)
=LOW PI =LOW or VERY LOW RATE
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Confusing heterogeneous denominations :
- Heavy Oil, Extra Heavy Oil, Oil Sands, Tar Sands, Bitumen,

….
è need for a simple classification
4 Classes based mainly on downhole viscosity :
0 A Class : Medium Heavy Oil 25°> d°API > 18°
100 cPo >m > 10 cPo, mobile
at reservoir conditions
0 B Class : Extra Heavy Oil 20°> d°API > 7°
10 000 cPo >m > 100 cPo , mobile
at reservoir conditions
0 C Class : Tar Sands and Bitumen 12°> d°API > 7°
m > 10 000 cPo, non mobile
at reservoir conditions
0 D Class : Oil Shales
Reservoir = Source Rock, no permeability
Mining Extraction only
Heavy Oil : a mix of heterogeneous denomination
s
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Reservoir Engineering Courses – K. Madaoui - 2004
Heavy Oil (excluding Oil Shales) : 3 Main Categories
Heavy Oil Classification
Duri
Wabasca
Athabasca
Peace river
Cold lake
Lloyminster
Cat canyon
Kern river
Mount poso

Midway
Yorba linda
Belridge
Poso creek
Pilon
Morichal
Eljobo
Boscan
Bachaquero
Tia juana
Rospomare
Mormora mare
Sarago mare
Shoonebeck
Emeraude
Lacq
Grenade
Varadero
Boca de Jaruco
Bechraji
Upper & Lower Ugnu
West sak
Llancanelo
Captain
Estreito
Alto do rodrigues 1
Mariner (M)
Balol
Qarn alam
Bressay

Mariner (H)
Bati raman
Fazenda belem
Alto do rodrigues 2
10
100
1 000
10 000
100 000
1 000 000
10 000 000
0,0 5,0 10,0 15,0 20,0 25,0
API Density
Downhole Viscosity (Cpo)
Orinoco
B Class :
Extra Heavy Oil
C Class :
Tar Sands & Bitumen
A Class :
Medium
Heavy Oil
uTempa Rosa
(11-23°API)
uDalia
u
u Sup.
Canada
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Steam Injection
F Steam : Good Heat Carrier
T ö mo ø
Oil Mobility Increases
Steam Distillation Process in Zone 1 :
Light Oil Vapor Condenses and Enriches Existing Oil
Reduction on Sor Thanks to Solvent Slug
F Application :
Max Depth = 1500 M (Heat Losses)
So > 50 %
Thick Pay, High K
Cheap Steam
Thermal Methods
Fundamentals of Reservoir Engineering
:
s
t
e
a
m
i
n
j
e
c
t

i
o
n
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Reservoir Engineering Courses – K. Madaoui - 2004
Steam Injection
Schematic Representation of in Situ Combustion Process and
the Various Zones as Formed in the Oil Reservoir
Steam
Injection
Steam
Hot Water Zone
Producer
C
o
n
d
e
n
s
e
d
S
t
e
a
m
Oil & Water
Thermal Methods
Fundamentals of Reservoir Engineering

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Reservoir Engineering Courses – K. Madaoui - 2004
Cyclic Steam Injection Process Scheme
Produced fluidsSoak periodSteam injection
Steam
Viscous oil
Heat
Low
oil
Viscosity
Water
Viscous oil
Heat
Steam
Thermal Methods
Fundamentals of Reservoir Engineering
Cond.
water