Process Modeling of Wellbore Leakage for GCS Risk Assessment

Transcription

1 Process Modeling of Wellbore Leakage for CS Risk Assessment Crtis M. Oldenbrg Earth Sciences Division Lawrence Berkeley National Laboratory Contribtors: Leha Pan (LBNL) Bill Carey (LANL) IEAH- Modeling and Risk Management Network Meeting Trondheim, Norway Jne 11, 2013 Lawrence Berkeley National Laboratory Earth Sciences Division 1 Cyclotron Road, MS C Berkeley, CA

2 Otline Introdction and motivation Models of cement and casing degradation Wellbore leakage flow conceptalizations Modeling examples Copling with reservoir Two-phase flow effects in wellbore Phase change de to decompression Two-phase drift-flx model demonstration 2

3 Introdction Wellbore integrity relies on cement, steel, and pressre control Well failres can lead to flid flow with severe conseqences Modeling of flid flow in well-leakage scenarios is critical for risk assessment This talk presents a review of modeling of wellbore sealing, failre mechanisms, and pward flid leakage From asda et al. (2004) Env. eol. (Dan Magee, Alberta eol. Srvey) 3

4 eochemical Model of Cement-CO 2 Reactions Accrate representation of CO 2 -cement reactions as observed in the field and laboratory Depth of CO 2 penetration is limited by a diffsion /reaction mechanism Low porosity, carbonaterich zones form and impede CO 2 migration Carey et al. (2007) IJCC 4

5 Mltiphase Flow and Reaction Demonstrates that CO 2 does not penetrate good-qality cement Capillary forces prevent CO 2 migration into cement Interfaces are the key to leakage of CO 2 Carey and Lichtner (2011) SPE Jornal Slide 5 5

6 eomechanical Model of Wellbore Systems Flly 3-D model of stress and mltiphase flow Shear- and tensile-failre modes Impact of thermal and mechanical stress on enhanced permeability and flow High reservoir pore pressres can damage the cement sheath Lewis, Carey et al. (2012) American Rock Mech. Assoc. Proceedings Slide 6 6

7 Corrosion rate / (mm/yr) Corrosion Model for Steel Casing Water chemistry represented with Pitzer activity formlation for accrate representation of brine The dominant cathodic reaction is de to carbonic acid Steel corrosion rates increase rapidly with CO 2 pressre and temperatre as Soltion Salt CO 2 CO 2 CO 2 CO 2 CO 2 CO 2 CO 2 CO 2 H 2 O H 2 CO 2 H 2 CO 3 HCO 3 - CO 3 2- Fe ++ Fe Steel Ohio University - Institte for Corrosion and Mltiphase Technology bar 10bar 100bar 500bar H 2 Na + Cl - Han et al. (2011) IJC Temperatre / C 7

8 Wellbore Flow Conceptalizations Poros media Degraded cement with connected porosity => Poros media flow, Darcy s Law (mltiphase) Open wellbore or annlar gap Loss of pressre control Cement and/or casing failre => Pipe flow, Navier-Stokes eqns (two-phase) In all cases, mst simlate copled processes, e.g., Wellbore-reservoir copling as exsoltion Decompression cooling 8

9 Example: Estimation of the Macondo Oil Leakage Rate Oldenbrg, Freifeld, Press, Pan, Finsterle, and Moridis, Proceedings of the National Academy of Sciences (2012):

10 Example: Estimation of the Macondo Oil Leakage Rate Primary reslt shows sensitivity of flow rate to the size of the opening to the well in the reservoir. Oil flow rate is also sensitive to the pressre at the bottom of the BOP, with gas exsoltion moderating oil flow for lower P BOP. Oldenbrg, Freifeld, Press, Pan, Finsterle, and Moridis, Proceedings of the National Academy of Sciences (2012):

11 Decompression Cooling => Liqid CO 2 LUCI = Laboratory for Undergrond CO 2 Investigations E.g., physics of pward CO 2 flow, expansion, and trapping Three 500 m high vessels, 1 m in diameter Filled with brine and sand T and P gradients to mimic the sbsrface We carried ot simlations to observe the effects of sidewall bondary conds. Inslated sidewalls => formation of liqid CO 2 Profiles of P, T, S CO2, and r CO2 at t = 30 days PT profile showing expansion cooling and formation of three-phases (liq. CO 2, gaseos CO 2, aqeos) Oldenbrg, Doghty, Peters, and Dobson, reenhose ases: Science and Technology 2.4 (2012):

12 Sharing animated reslts in pbs. 12

13 T2Well is a Drift-Flx Model for Copled Wellbore-Reservoir Systems Momentm eqation is solved for the mixtre velocity Open wellbore Individal phase velocities are given by the mixtre velocity pls a drift velocity We have developed a code called T2Well that implements the DFM in wells within the TOUH2 framework T2Well has been sed extensively by s to simlate two-phase flows of CO 2 or CH 4 in water or oil Aside from the non-darcy flow in the well, T2Well provides implicit copling of wellbore and reservoir flow and transport 13

14 Drift-Flx Model In the DFM, we solve the momentm eqation for the mixtre only Drift-Flx Model: C 0 d L d c 1 SC0 C 0 1 S S g 1 C L C 0 C0 r ) S 1 S 0 S / r C L 0 c K 1 C r L r 2 r L S 1/ 4 0 S d inertia Momentm eqation for the flid mixtre: t f z P z f r 2 r r r g cos 1 f 64 Re if 2 / d 2log 3.7 Re Re 2 / d log 3.7 2d 13 Re friction if Re 2400 gravity ρ density; S gas satration; mixtre velocity; gas velocity; L liqid velocity; d drift velocity; c critical velocity; gcosθ gravity ; C 0 profile parameter; σ L srface tension between gas and liqid phases; Re Reynolds nmber; ε wellbore roghness; d wellbore diameter; t time; z distance along wellbore 14

15 Example: Non-isothermal leakage flow when a CO 2 plme (10% S, + 0.1MPa) reaches an open wellbore initially fll of water 1000 m CO 2 plme 15

16 CO 2 and Water Flowing p Wellbore Flow rates and velocities of CO 2 and water at three levels in the well. Profiles of gas satration, gas density, pressre, and temperatre as fnctions of time 16

17 Conclsions Well integrity is a primary concern for leakage from CS sites Models have been developed to nderstand processes that lead to loss of integrity Poros media and open-pipe flow conceptalizations of flow are needed for different well leakage scenarios Regardless of conceptalization, rigoros copling to the reservoir is needed bottomhole pressre cannot be assmed fixed mobile satration in the reservoir mst be sed as exsoltion and decompression cooling can both affect pward leakage T2Well can be sed to simlate non-isothermal, mlticomponent, two-phase flow in open pipes or annlar gaps copled to a poros media reservoir. 17

18 Acknowledgments Spport for this work comes from the Assistant Secretary for Fossil Energy, Office of Seqestration, Hydrogen, and Clean Coal Fels, National Energy Technology Laboratory, of the U.S. Department of Energy, and by Lawrence Berkeley National Laboratory nder Department of Energy Contract No. DE-AC02-05CH

19 Mass and Energy Conservation F q t M r r L L L X S X S M z X A z X A A F L L L 1 r r Conservation eqation: Sperscript k components Sbscript β-- phase ( or L) Mass accmlation: Energy accmlation: Mass flow rate: Energy flow rate: r U S M ' ' cos q g A A z h S A z A F m m r r r Kinetic energy per nit mass ρ density; S satration; X mass fraction; U internal thermal energy per nit mass; velocity; A cross sectional wellbore area; h enthalpy per nit mass; gcosθ gravity ; q heat loss per nit wellbore length; t time; z distance along wellbore 19

20 Implementation in TOUH2 Mass & Energy eqations (classical TOUH2 soltions for both wellbore and reservoir) Cell i-1 Cell i Cell i+1 Face i-1/2 Face i+1/2 Momentm eqation (wellbore soltions of velocity) Semi-explicit approach to avoid introdcing an additional primary variable: Implicit pressre and gravity driving force n1 DR n1 1 n r t n r t 1 f n n r z n n r 2d 2 n Explicit spatial acceleration term Explicit part of friction n previos time level; n+1 crrent time level; t time step size 20