Supercritical CO leakage Modeling for Well Integrity in ... fileOutline Context Geological storage...
Transcript of Supercritical CO leakage Modeling for Well Integrity in ... fileOutline Context Geological storage...
Supercritical CO2 leakage Modeling for Well Integrity in Geological
Storage Project
Houdu E., Meyer V., Poupard O.Oxand S.A., France
COMSOL ConferenceNovember 4-6, 2008
Storage Project
Presented at the COMSOL Conference 2008 Hannover
Outline
� Context
Geological storage project
�OXAND’s activities: Well Integrity Risk Analysis
� Modelling� Modelling
Governing equations
�Porous media flow, biphasic system
� Results
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Context
� Confirmation of global warming
Kyoto agreement
� CO2 market
legal framework,legal framework,taxes
� EOR
Enhanced Oil Recovery
Growing interest for CO2 geological storage as a feasible and relevant solution
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Geological storage project
� CO2 Injection and long-term geological storage in:
Hydrocarbon reservoirs
Saline aquifers
Coal-bed
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Geological & Biosphere system
Hydrocarbonreservoir
Wells
Saline aquifer
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Geological system
Aquifer
Hydrocarbonreservoir
Caprock
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Well Integrity Risk Analysis
Aquifer
Hydrocarbonreservoir
Caprock
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Well Integrity Risk Analysis
Reservoir depletion
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Well Integrity Risk Analysis
Reservoir depletion
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Well Integrity Risk Analysis
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Well Integrity Risk Analysis
CO2 injection
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Cement sheath
Well Integrity Risk Analysis
CO2 leakage through the well during the injection and at long-term ?
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< 1 m
1-5 km
Well Integrity Risk Analysis
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< 1 m
1-5 km
Well Integrity Risk Analysis
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< 1 m
1-5 km
Well Integrity Risk Analysis
1504/11/2008
Rat hole1-5 m
Rat hole represents key element in the CO2 leakage simulation
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Modelling
�Biphasic flow model
Water + Supercritical CO2Incompressible phases
�Fluids properties at p, T bottom injection �Fluids properties at p, T bottom injection reservoir
�Well modelling
Well is assumed as a concentric system
�Cylindrical coordinates
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Meshing
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Meshing
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Computation stage
� Initial condition:
Initial equilibrium
Depletion period
Injection
pw
pnw
Reservoir Pressure
Timedepletionperiod
post injection
� Boundary condition
Aquifer connection� water
Bottom reservoir connection� CO2
Surface connection� atmosphere, water
Initialequilibrium
periodinjection
injection
Aquifer
Surface
Reservoir
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Governing Equations
�Wetting phase:
(1)0)(, =
+∇
⋅−⋅∇+
∂∂
gHpkk
t
Sww
w
wrwS ρ
ηδ
�Non-wetting phase:
(2)
∂t wη
0)(, =
+∇
⋅−⋅∇+
∂∂
gHpkk
t
Snwnw
nw
nwrnwS ρ
ηδ
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Pressure form
�Wetting phase:
(3) 0)()( ,
, =
+∇
⋅−⋅∇+
∂−∂
gHpkk
t
ppC ww
w
wrwnwwp ρ
η
�Non-wetting phase:
(4)
∂t wη
0)()( ,
, =
+∇
⋅−⋅∇+
∂−∂
gHpkk
t
ppC nwnw
nw
nwrwnwnwp ρ
η
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Specific capacity
�Specific capacity
�Relationship between effective water saturation and specific capacity
c
wsnwpwp p
SCC
∂∂=−= δ
,,
saturation and specific capacity
( )m
mmwrwp S
m
mC
Θ−Θ−
−=
11
,, 111
φα
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Porous media
� Capillary pressure
� Relationship to close biphasic flow model (Van Genuchten):
wnwc ppp −=
M(Van Genuchten):
(7)
the effective saturation of wetting phase
the capillary pressure pcthe capillary pressure head pec
Θ=
+ 1
1
MN
ec
c
p
p
rw
rww
S
SS
−−
=Θ1
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Main Results: Effective Water Saturation
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Main Results: Effective Water Saturation
Max: 1
Min: 0.125
Effective Water Saturation
Casing
Sew max = 1
Caprock
Reservoir
Sew min = 0.15
No CO2 leakage with aquifer connection26
Effective Water Saturation
Casing
Sew max = 1
Caprock
Reservoir
Sew min = 0.15
No CO2 leakage with aquifer connection27
Radial pneumatic gradient
Casing
0>∂Hnw
Caprock
Reservoir
0>∂
∂r
Hnw
No possible CO2 radial flow in the rat hole
0<∂
∂r
H nw
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Numerical difficulties
� Space distortion
Radial size scale: <1 m
Axial size scale: 1000 m
� Permeability
Well cavity (5O D)
Caprock ( 0.001 mD)Caprock ( 0.001 mD)
Bad cement sheath (10 mD)
���� Large ranges of values for parameters describing the well induce numerical difficulties
� Capillary pressure head
Need values > 0,1 bar to converge
���� Due to Van Genuchten model
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Conclusions
� Numerical simulations have highlighted the competition between the gas flow and the liquid flow in a specific area of a well
� The rat-hole zone constitutes a key element to consider in the long term integrity performance of a wellwell
� An improvement of the knowledge of the flows in this specific area within the well will be a support in assessing the Performance and the Risks from a well integrity perspective
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Future works
� Robustness analysis to be performedTo quantify the CO2 leakage in the case of no aquifer protectionImprovements in the modeling to take into account the significant differences between some parameters values for two linked elementsvalues for two linked elements
� This study will have to be coupled to a macroscopic CO2 leakage modelling within well system.
Essential into a quantitative well integrity risk analysis for CO2 storage projects
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