Building confidence of CCS using knowledge from natural analogues

Transcription

1 Building confidence of CCS using knowledge from natural analogues Kenshi Itaoka and Koji Yamamoto Mizuho Information and Research Institute (MHIR), Tokyo, Japan The 2 nd Meeting of the Risk Assessment Networt October 5-6, 2006, Lawrence Berkeley National Laboratory 1

2 Contents of the presentation How natural analogues can help building confidence for CCS decision making (building confidence in long term effectiveness and safety). Our ongoing natural analogue study Promotion of international collaboration. 2

3 How natural analogues can help building confidence for CCS. 3

4 Characteristics of CCS risk Super long-term risk and high uncertainty Natural risk and manmade risk Intrinsic uncertainty of the geological systems Difficulty of the data acquisition Uncertainty of the behavior of injected CO 2 Difficulty of the verification 4

5 Different types of the risk Natural risks. Broad unknowns and known uncertainty. The damages should be minimized. Manmade risks No or little unknown uncertainty but there is known uncertainty. The probability should be minimized. 5

6 Issues of building confidence for CCS effectiveness of confinement: risk of seepage 1. Risk: difficult to interpret Natural analogue Very long-term risk Unfeasibility of long-term monitoring Reliance on numerical modeling for prediction but difficulty in the verification Probability consequence The fraction retained in appropriately selected and managed geological reservoirs is very likely to exceed 99% over 100 years and is likely to exceed 99% over 1,000 years (IPCC SR) 2. Known uncertainty: difficult to estimate Intrinsic uncertainty of the geological systems: complexity Behavior of injected CO 2 Error of obtained information 3. Unknown uncertainty:?? Intrinsic uncertainty of the geological systems: heterogeneity (unknown factors) 6

7 How natural analogue can be used for building confidence? Understanding the leakage and trap mechanism Effectiveness of the four trap mechanisms: proof of confinement Effects of the heterogeneity of the earth crust on CO 2 behavior Verification of numerical models and risk assessment procedures Long-term behavior of the CO 2 can be observable and comparable to the simulation results Reduction of uncertainty of parameters of models. Test of monitoring methodology. Interpretation and risk management Help interpretation of stochastic events and their consequence. Comparison of natural analogue sites and a CCS site give basic idea of the character, magnitude and impact of the leakage risk. Risk communication Communication of how safe and how risky. Risk of the CO 2 leakage can be measurable and comparable to the assessed results 7

8 Risk types and management options Manmade pathways (poor well completion, abandoned wells, etc.)- Engineering solutions Technology development and strict design guideline for new wells Finding old wells Mitigation techniques Natural pathways Natural analogue Slow migration in the seal formation- main stream leak risk Site selection Monitoring the migration to find unidentified pathways Modelling based assessment of the leak-rate and total escapable volume considering trap mechanisms to ensure that they are acceptable level Unknown/unpredictable pathways, creation of new pathways -that may not happen in the monitoring term Explore the pathways as much as possible Site selection with assessed leak risk based on the known conditions Natural analogue based risk assessment to know how common, how significant effects. 8

9 Events comparable to natural/industrial phenomena Examples CO2 release from failed wells CO2 release through reactivated faults Seismic, volcanic, and other tectonics related activities Activities caused by other external natural force (glacier, meteorite impact, Critical points of the risk assessment Geological, mechanical and chemical conditions that govern the initiation and termination of the leakage and its rate Frequency/Impact on the human health and eco-system Risk management options from the analogue study Compare the conditions (geological/geochemical/geomechanical, etc.) Identify that the relationship between the conditions and probability/consequences Choose the management options Accepting the risk Monitoring to detect the leakage Some remediation options, etc. 9

10 For risk interpretation and management Risk matrix of the CO2 leakage events based on natural analogue (if site is in the same condition ) Consequence Detectable but no effects on human health and environment Anxiety, discomfort, impact on env. recoverable in short time Damage on human health and life, long-term impact on env. Massive loss of life, unrecoverable change of ecosystem Probability More than once in the project term (<50 yrs) More than once in the reserve period(<1000 Geological yrs) evidence of the phenomena Monitoring, damage reduction measures Acceptable with monitoring of leakage Acceptable without any countermeasures Prevention Not allowable 許容不可 measures or (abort the project) design change to Condition of Condition of Condition of Mammoth Mt. Dieng Matsushiro 許容不可 Theoretically possible 10

11 For risk interpretation and management Risk matrix of the CO2 leakage events based on the industrial analogue Consequence Detectable but no effects on human health and environment Anxiety, discomfort, impact on env. recoverable in short time Damage on human health and life, long-term impact on env. Massive loss of life, unrecoverable change of ecosystem Probability Usually happen in each field Often heard in the industry (once per year) One or a few records in the industry Not heard in the industry Prevention measures or design change Monitoring, damage reduction measures Acceptable with monitoring of leakage Acceptable without any countermeasures Not allowable (abort the project) 許容不可 許容不可 11

12 Our natural analogue study ongoing 12

13 Objective Study of natural analogues To identify key mechanisms and processes relevant to long-term stability and potential seepage associated with CO2 geological sequestration Faults One of the major potential cause of CO2 seepage Difficult to characterize by laboratory tests 13

14 Location of Matsushiro 10km Nagano Nagano city Mt.Minakami Matsushiro (dashed line area) East Nagano Basin fault Location: suburb of Nagano city Land use: agricultural, residential Geology: NE-SW major reverse fault and conjugated strike-slip fault 14 fan sediment(surface), volcanic rock(basement), lava dome

15 Characteristics of Matsushiro Major reverse fault and conjugated strike-slip fault A little CO2 is emitted from ground.(present). Earthquake Swarm( ) 60,000 earthquakes were felt and additional 600,000 unfelt tremors were recorded during five-year period (JMA,1968) Total energy released was M6.4, the energy of the maximum single earthquake was M5.4 During the swarm, ten million tons of CO2 bearing water discharged at the surface through newly created surface ruptures 15

16 rupture High conc. discharge area Discharge area Vertical Movement (>30cm) Nakamura(1971) One probable cause of the swarm: - water intrusion from great depth - dilatancy reactivated the fault system 16

17 Matushiro and Mammoth Mt. Geological conditions and Phenomena Matsushiro Mammoth Mt. Geology Hypabyssal rocks, surface is Volcanic rock covered by sediment Structure Uplift zone near a volcano Outer rim of a caldera Hydrogeology Much rain fall, Snow fall, Stress state Compressional (Strike-slip fault) Extensional (Normal fault) Fault Single fault with a conjugate fault Complex system Relation to During the seismic activity After the earthquake (?) earthquake Long-term Stop immediately (?) Continue for more than ten years Fluid CO2 saturated brine Free gas Impact No casuality, influence on the ecosystem not detected Tree kill, a skier overwhelmed 17

18 Number of earthquakes 700 Surface rupturing and active water discharge (1966/ /02) lateral fault 3km 4km Stage 1 Stage 2 Stage 3 80cm Mean depth of focal points Flow rate of a water spring Upheaval Stage 4 Cl - Concentration 400l/min 4000ppm 5km Time series change of seismicity, uplift, spring discharge, and salinity 18 ( ). (After JMA 1968, Tsukahara and Yoshida 2005)

19 Hypothesis and approaches Geochemistry Supply of CO 2 bearing water from deep formations Dissolution of carbonate cap by increased acidity Pore pressure increment and reactivation of faults (enhancement of permeability and earthquakes) Degassing from water Geomechanics Creation of Carbonate cap Fluid pressure release due to outflow, degassing and dilatancy of faults Stabilization (current state) [Approach 3 : Geochemical survey] -Soil gas concentration -CO2 flux [Approach 1 : Geochemical Modelling] [Approach 2 : Geomechanical Modelling] Max. horizontal stress Mt. Minakami Surface ruptures Low velocity zone High velocity zone Upward fluid motion See Todaka et al. in GHGT-8(poster) Fluid source Left lateral strike-slip fault 19

20 Summary and future work Matsushiro site is a promising natural analogue for studies of fault - fluid interaction related to CO 2 injection, including both mechanical and chemical interactions Geochemical survey, geomechanics coupled flow modelling, geochemistry coupled flow modelling are being conducted Resistivity survey, drilling and fluid sampling, and further modelling work will be done this year Risk assessment and management guideline for CO 2 seepage through faults will be established using this natural analogue 20

21 Promotion of international collaboration 21

22 Need International collaboration There are many existing studies NASCENT, NACS, GEODISC Need more applications of knowledge from natural analogue to various stages of risk assessment and building confidence. Sharing collection of application of natural analogue would help building confidence for CCS in the world. 22