Modeling of CO 2 leakage rates coupled to wellbore cement reactivity

Transcription

1 Modeling of CO 2 leakage rates coupled to wellbore cement reactivity Laure Deremble, Bruno Huet*, Jean Desroches * now with Lafarge

2 Problem statement Leakage = Flowing fluid from a Source along a Pathway to a Target What we know: mechanical debonding conditions.no defect = no leak Challenge: feedback of cement reactivity on leakage rates for existing defects?

3 Outline Do we understand cement reactivity in 1-D scenario? Experimental evidence (Duguid, Barlet-Gouedard and Kutchko) Experimental conditions Main features Modeling the brine composition effect on the rates Can we model cement feedback on CO 2 leakage rates? Numerical experiments conditions Leakage dynamics Conclusion What we know, better! Remaining challenges

4 1-D Experimental evidence Rates: total reacted layer thicknesses vs sqrt of time Can we explain these differences?

5 Experimental evidence Experimental conditions summary: Parameter Duguid Barlet Kutchko P [bar] T [ C] NaCl [molal].5.17 Cement Portland Portland Portland Boundary conditions - Brine Boundary conditions: Open Closed Closed Boundary conditions - Gas Open Open Open gas brine cement mass transfer closed boundary

6 Main features Main features: Duguid 25, 29 Barlet-Gouedard 26 Kuchko 28 Aqueous species concentration profile Ca 2+, CO 2, mol.kgw Cement C-S-H CalCite SiO 2

7 1-D Boundary conditions Da vs pco 2 (ph 3.7 and 25 C, D = 1-9 m 2.s -1, pco 2 = -log1 (CO 2 )) Reacted layer thickness [m] x pco 2 = pco 2 =1 pco 2 =1.3 pco 2 =1.4 pco 2 =1.5 pco 2 =1.6 pco 2 =1.9 pco 2 =2.2 Layer dynamics at ph = Time [s 1/2 ] Log1(Da/D ) pco 2 Large range of rates depending on brine conditions

8 Outline Do we understand cement reactivity in 1-D scenario Experimental evidence (Duguid, Barlet-Gouedard and Kutchko) Experimental conditions Main features Modeling the brine composition effects on the rates Can we model cement feedback on CO 2 leakage rates Numerical experiments conditions Leakage dynamics Conclusion: What we know, better! Remaining challenges

9 Description of the phenomenon: CO 2 flowing in the defect space Calcite precipitation z δ CO 2 [Ca 2+ ] [mol/kgw] Calcite equilibrium CO 2 is absorbed Ca 2+ is released λ Flow of CO 2 rich brine CO 2 Ca [CO 2 ] [mol/kgw] CO 2 Ca 2+ Cement Calcite Silica Gel [Ca 2+ ], [CO 2 ]

10 Stability criterion for risk assessment: Dimensional analysis t Z S + S + vs X = J x ( ( )) liq ζliq sol ζsol ( liq ζliq liq ) k k k 3 dimensionless groups: ζ l Gδ l = ζs ζl Dcalcite GD = DSG 4 CO2 wδpm % ρw Gμ = = 2 12μ f Λ D1cs t t χ μ 2 dimensional parameters: m CO 2 2 Ca m + Characteristic values: Z t J CO2 CO2 mw 2 CO2 * wm = tχ = cd s 1 * 1 m Dcs = w ρ w

11 Stability criterion for risk assessment: Is the defect self-healing? Simulation at constant cement properties X: no plugging X: plugging G 1.5 x 1-3 μ = w ΔPm % ρw 12 Dc 4 CO2 2 μ f Λ 1 s Forecast for injection condition: 5 bars Defect over 1m of wellbore length Width of the defect : 1 μm or 8 μm G μ 1.5 No stable leaks! Rate decrease until complete cement carbonation m co2 [mol/kgw] Annulus clogging depending on initial width for brine leakage

12 What we know: Models explain large differences in rates of Portland cement reactivity Three main mechanisms: 1) Calcium leaching, 2) Carbonate ingress, 3) Pore clogging Related to: 1) system composition (IC, BC) and 2) P,T Experimental evidence on New cement matrices (FA, BFS): Carbonation rates much faster, carbonation degree much lower) No stable leaks!

13 Remaining challenges Need for further 1-D experiments! Check transition conditions between mechanisms upon brine compositions Other possible rate controlling mechanisms? Transition of mechanisms in time? New cement matrices (FA, BFS) Thermodynamics of hydrates (C-S-A-H, ) Slow hydration: competition between hydration and carbonation Need for 2-D experiments with P, T and flow control! Verify annulus clogging conditions Clogging of annulus for Ca and CO2 saturated brine Control of CO 2 gas (liquid) leaks: reactive and expansive chemicals

14 Questions? Contact information: