Methodological developments to define safety criteria

Transcription

1 Methodological developments to define safety criteria Olivier BOUC 3 rd IEA GHG Risk Assessment Network Meeting - London

2 Frame of our research > BRGM research about safety criteria for CO 2 geological storage Internal research project 3 years project funded by the National Resarch Agency, with TOTAL, Armines, University Paul Sabatier (Toulouse), University of Neuchâtel Safety criteria for CO 2 geological storage: qualitative/quantitative approach of risk scenarios > Aim: contribute to demonstrating safety of CO 2 geological storage > Safety criteria performance objectives > 2

3 Safety criteria > Requirements to ensure near-zero local impacts on health, safety and the environment in the short, middle and long term Qualitative / generic Quantitative / site specific > 3

4 Purpose > Provide a simple workflow to evaluate safety in a licensing process Build long-term evolution scenarios Evaluate potential targets exposure using simple models Determine safety criteria > Not a risk assessment Rather keys to control a risk assessment > First choose a method to build scenarios Methodological exercise to try the use of FEPs > 4

5 Context of the assessment > Hypothetical storage site > In the East of the Paris Basin Strategic aquifer at -800m > In the Dogger aquifer -1700m, thickness 25m Nearly flat reservoir, very slow natural flow (1m/yr) Near hydrostatic stress state ~ 16% ; K ~ 1 D ; T ~ C ; P ~ 173 bars > 5

6 FEPs database workflow used 1- Identification Which FEPs do enter the frame of analysis? Characterised Fs EPs 2- Evaluation Probability / Potential impacts Excluded FEPs Quintessa online FEPs database Workflow closely inspired by Vattenfall & TNO «Safety assessment of structure Schweinrich» in CO2STORE Reference scenario Reference scenario EPs EPs and associated risk level 3- Selection Depending on the risk level determined 5- F-EPs Correlation Which Fs linked to which EPs groups? Fs linked to EPs groups Alternate scenarios EPs 4- Grouping Which EPs do present similarities? EPs Groups 6- Interactions Which interaction intensity between EPs Groups? Interaction matrix / influence diagram between EPs groups 7- Alternate scenarios constitution Screened out EPs Alternate scenarios composed by EPs groups and related Fs

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8 Results: six leakage scenarios identified > 8

9 Freshwater aquifer Reservoir 1 1 Well degradation 2 Cap rock fracturing due to overpressure 3 Leakage through buoyancy 4 Leakage through a fault 5 Reservoir water migration 6 Open hole leakage CO 2 injection well Hydrocarbons extraction well Observation well CO 2 migration Saline water migration Aquifer regional flow Pressure front propagation Overpressure Fault

10 Feedback from our attempt > Method not optimal Tedious and time-consuming Result: very little surprise compared to the investment! Very close to the results of the CO2STORE study > Some steps arguable OK for steps 1-3 (Identification Evaluation Selection) Step 4 (Grouping) determining and questionable: seems very subjective Idem for step 7 (Deducing scenarios from influence diagram) > Results achieved by giving up steps 4-7 > 10

11 Restrictions > Only a test first use of the tool > Hypothetical site lack of real data > Not an expert panel > Difference TNO Quintessa database TNO maybe more suitable for this method But would it really be more time-efficient? > Schweinrich case study hypotheses close to ours > 11

12 Feedback (2) > Main advantages of the FEPs Comprehensiveness Systematic documentation of the evaluation > Is this really appropriate in our approach? > Maybe not a scenario-building tool? > Rather an audit tool Top-down use Cf. Quintessa document (Savage et al.[2004], A generic FEP database for the assessment of long-term performance and safety of the geological storage of CO 2 ) > 12

13 Possible scenario construction methods > Non-FEPs approaches: GEODISC (Australia): an expert panel reviews a limited number of risk events (probability/impacts) > FEPs approaches Battelle, Mountaineer (USA): more qualitative and quick screening of the FEPs DB. Decision oriented for risk management. > Mixed approach: Identification of simple scenarios by an expert panel Audit with the generic FEPs database > 13

14 Further work and perspectives > Base safety criteria on potential targets > Develop a site model representing the potentially exposed elements > Link risk scenarios to targets exposure > Build simple models to evaluate CO 2 fluxes between compartments Analytical, semi-analytical, 1D How to ensure they are representative? Address uncertainties > Infer safety criteria > 14

15 Site model for CO 2 storage in aquifer underneath the Paris Basin Potentially exposed elements 10 km Aquifer to be preserved Reservoir? NB : local topography is overstated in comparison to the scale for subsurface depth CO 2 injection well River Facility where CO 2 is produced and captured CO 2 injection Oil extraction well Observation well Potable water catchment City: economic activity and living area Site with nature conservation measures Site with heritage protection measures Zone widely devoted to agricultural land use Aquifer regional flow direction Fault Potential CO 2 leakages (6 identified scenarios)