Supercritical CO 2 leakage Modeling for Well Integrity in Geological Storage Project

Transcription

1 Presented at the COMSOL Conference 2008 Hannover Supercritical CO 2 leakage Modeling for Well Integrity in Geological Storage Project Houdu E., Meyer V., Poupard O. Oxand S.A., France COMSOL Conference November 4-6, 2008

2 Outline Context Geological storage project OXAND s activities: Well Integrity Risk Analysis Modelling Governing equations Porous media flow, biphasic system Results 2

3 Context Confirmation of global warming Kyoto agreement CO 2 market legal framework, taxes EOR Enhanced Oil Recovery Growing interest for CO 2 geological storage as a feasible and relevant solution 3

4 Geological storage project CO 2 Injection and long-term geological storage in: Hydrocarbon reservoirs Saline aquifers Coal-bed 4

5 Geological & Biosphere system Wells Hydrocarbon reservoir Saline aquifer 5

6 Geological system Aquifer Caprock Hydrocarbon reservoir 6

7 Well Integrity Risk Analysis Aquifer Caprock Hydrocarbon reservoir 7

8 Well Integrity Risk Analysis Reservoir depletion 8

9 Well Integrity Risk Analysis Reservoir depletion 9

10 Well Integrity Risk Analysis 10

11 Well Integrity Risk Analysis CO 2 injection 11

12 Well Integrity Risk Analysis Cement sheath CO 2 leakage through the well during the injection and at long-term? 12

13 Well Integrity Risk Analysis < 1 m 1-5 km 13

14 Well Integrity Risk Analysis < 1 m 1-5 km 14

15 Well Integrity Risk Analysis < 1 m 1-5 km 1-5 m Rat hole Rat hole represents key element in the CO 2 leakage simulation 04/11/

16 Modelling Biphasic flow model Water + Supercritical CO 2 Incompressible phases Fluids properties at p, T bottom injection reservoir Well modelling Well is assumed as a concentric system Cylindrical coordinates 16

17 Meshing 17

18 Meshing 18 18

19 Computation stage Reservoir Pressure Initial condition: Initial equilibrium Depletion period Injection Boundary condition Aquifer connection water Bottom reservoir connection depletion period Initial injection equilibrium post injection Aquifer p nw p w Time Surface CO 2 Surface connection atmosphere, water Reservoir 19

20 Governing Equations Wetting phase: δ S S tt w + k k η w r, w ( p w + ρwgh ) = 0 (1) Non-wetting phase: δ S S t nw + k k η r, nw nw ( p nw + ρ nw gh ) = 0 (2) 20

21 Pressure form Wetting phase: C p ( p ) k k nw pw r, w, w + ( pw + ρ w gh ) = tt η w Non-wetting phase: 0 (3) C p ( p ) k k, nw pw r nw, nw + ( pnw + ρ nwgh ) = t η nw 0 (4) 21

22 Specific capacity Specific capacity C p, nw Relationship between effective water saturation and specific capacity p, w = C δ s S = p c w C αm 1 m ( ) 1 m p, w = φ 1 Sr, w Θ 1 Θ 1 m m 22

23 Porous media Capillary pressure p c = p nw p w Relationship to close biphasic flow model (Van Genuchten): N M pc = (7) the effective saturation of wetting phase the capillary pressure p c the capillary pressure head p ec S w S Θ = 1 S rw rw p ec Θ 23

24 Main Results: Effective Water Saturation 24

25 Main Results: Effective Water Saturation Max: 1 Min:

26 Effective Water Saturation S ew max = 1 Casing Caprock S ew min = 0.15 Reservoir No CO 2 leakage with aquifer connection 26

27 Effective Water Saturation S ew max = 1 Casing Caprock S ew min = 0.15 Reservoir No CO 2 leakage with aquifer connection 27

28 Radial pneumatic gradient Casing H H nw r > 0 r H nw < 0 Caprock Reservoir No possible CO 2 radial flow in the rat hole 28

29 Numerical difficulties Space distortion Radial size scale: <1 m Axial size scale: 1000 m Permeability Well cavity (5O D) Caprock ( 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 29

30 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 well 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 30

31 Future works Robustness analysis to be performed To quantify the CO2 leakage in the case of no aquifer protection Improvements in the modeling to take into account the significant differences between some parameters values 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 31