CCS Technical Workshop, Tokyo, Japan, 24th January 2013

Development of an assessment
methodology for CO2 leakage fromoff‐shore reservoir
海底下貯留における海域環境影響評価手法の開発

Keisuke UCHIMOTO (RITE)
内本 圭亮

Offshore CO2 storage

Caprock layer prevents
injected CO2 from leaking

caprock layer
reservoir

Various trapping
Physical trapping

(%)
100

In addition to physical trapping•Solubility trapping: dissolution inContribution●●

 Buoyant forces are eliminated●•Mineral trapping: conversion to●●stable carbonate minerals

●
●

● ●

0formation water

1●

●

●

10●

●

●

100

1000

10000
Since injection stops (year)

Risk of CO2 leakage fromReservor is thought tobe little.

Why is the assessment necessary?
Science and Technology is not perfect.
Possibility of leakage is thought to be little butnot zero.

–Required by law→ talked by Dr. Kita
–To gain Public acceptanceDevelopment of simulation models
If stored CO2 should leak into the sea,

what would happen?

RITE is developing numerical models
to simulate CO2 behavior from the reservoir tothe sea, to assess environmental impacts ofleaked CO2.

CO2 simulation models

sea MEC‐CO2sediment layer
C.CANDIformations
Tough
CO2 reservoir

Potential escape routes

IPCC Special Report on Carbon Dioxide Capture and Storage

Simulation in geological formations（Tough）
Constructing a model for potential
escape routes• bubble CO2• dissolved CO2
seabedCO2 migrates
according to•permeability•buoyancy

CO2 in the model:•supercritical•gas phase•liquid phase・dissolved

CO2（from reservoir）

Model domain

Permeability in escape routes• Appropriate values ?
– Actually there are no fault near the reservoir
through which CO2 may leak!

• Fault zone modeling– Geometry・Complexity・Damage zone・Type ofmaterialpermeability
LH

Talwani et al. (2007)

Sediment layer
sea
Sediment
formations(overburden)

Tens ofmetersOnlytens ofcentimeters

Around1km
or deeper

Reservoir

Sediment layer

Is this thin sedimentlayer important?
Is the simulationnecessary?

sea
Sediment
formations(overburden)

Tens ofmetersOnlytens ofcentimeters

Around1km
or deeper

Reservoir

Sediment layer
Sea
Organic matter・excretion
・dead organisms
etc.

buried and/or deposited
Sediment layer

Sediment layer
Oxygen respirationsea
sediment

Depth (cm)1

Denitrification
Manganesereduction

2

Iron reduction

3

Sulfate reduction

45

Fossing (2004)

Sediment layer
Sea
Organic matter・excretion
・dead organisms
etc.

buried and/or deposited
Sediment layer

C.CANDI:A model calculating
degradation anddiagenesis processes
in the sedimentlayer

Simulation in the sediment layer（C.CANDI）• Organic and inorganic matters are calculated– degradation, redox reaction– advection（transport by porewaters）– diffusion– bioturbation（mixing by benthos）

Simulation in the sediment layer（C.CANDI）• leaked CO2 simulation– CO2 from the seafloor :• Bubble CO2 (gas form)→ without any change within the sediment layer• dissolved CO2→ great change within the sediment layer

Simulation in the sediment layer（C.CANDI）
into sea

sea

T-CO2(mmol/L)
0cm 0

2040

Sediment Depth

Model domain(SedimentLayer;
1D model)CO2 from the seabed moves upward withthe concentration decreased.

seabedDissolved CO2
from the seabed

20cm

No CO2 leakage
CO2 leakage
Saturated CO2 from the formations

Simulation in the seawaterCalculating the distribution andconcentration of CO2 in the sea

CO2 in the sea•Bubble CO2•Dissolved CO2
may influence
the marine environments,
ecosystems

Simulation in the seawater
Bubble CO2 → dissolved CO2 →distributed in the sea

dissolved

dissolved

sea
leaked CO2

Simulation in the sea（MEC‐CO2）• MEC‐CO2 model– ocean model
calculating• current, temperature, and salinity in the sea• driven by tides, wind stress, heat flux, freshwater flux
(precipitation, evaporation, river runoff)– CO2 two‐phase model
calculating• bubble CO2• dissolved CO2• transfer from bubble to dissolved CO2

Simulation in the sea（MEC‐CO2）
Model domain(bathymetry)(m)

×

×：CO2 leakage point＋：tide station

Simulation in the sea（MEC‐CO2）• Time series of sea surface height anomaly[cm]Blue line：observation
Green dots：model results[days]

Simulation in the sea（MEC‐CO2）• Salinity (Sea surface, vertical section)

Simulation in the sea（MEC‐CO2）• Leakage rates according to Kano et al. (2010)– Reasonable rate: 3,800 t/y– Extreme rate: 94,600 t/y

Simulation in the sea（MEC‐CO2）
ExtremeReasonable

Database of impact assessment onmarine organisms• Accumulating a database– Biological impacts of CO2 ‐‐ pCO2, or resultant pHchange– Species by species– Degrees of impacts; decease, growth problem,etc.

Example of Database
供試生物

対照区pCO2（ppm）

サンゴ 成体Porolithon onkodes

135-460（pH 8.00-8.40）

サンゴ プラヌラ幼生
Acropora tenuis

400-475（pH 8.03）

動物プランクトン 幼生
Acartia erythrae

365

ヨコエビ 成体
Gammarus locusta

pH 8.1

巻貝 卵
Littorina obtusata―イカ類
Sepia lycidas
魚類
Paralichthys olivaceus

自然海水（pH 8.12-8.14）
自然海水（pH 8.111）

実験区pCO2（ppm）
520-705（pH 7.85-7.95）
1,010-1,350（pH 7.60-7.70）
905-1,660（pH 7.64）
2,115-3,585（pH 7.31）
2,365
5,365
10,365～550（pH 7.8）～980（pH 7.6）
1,100（pH 7.6）
30,000（pH 6.38）
50,000（pH 6.17）
70,000（pH 6.02）
100,000（pH 5.87）
150,000（pH 5.70）
9,900-79,000（pH 6.233-7.017）

暴露期間

影響

参考文献

白化が増加
8 週間

Anthony et al., 2008
白化が増加
なし

7 日間

生残率：低濃度区
より増加
なし
24 時間 生残率減少
生残率減少

Suwa et al., 2010

Kurihara et al., 2004なし
28 日間Hauton et al., 2009なし

約28 日間 生残率減少

Ellis et al., 2009

半数生存限界24 時間 （TLm）：84,000ppm

Kikkawa et al., 2008

6 時間 LC50：27,600ppm

Kikkawa et al., 2003

Example of results of databasegroup
Shellfish
Echinoderm
Coral
Coccolithophore
FishSquidzooplankton

pCO2

influence

Δ200ppm<

Declining
calcification

Δ2,000ppm<Physiologicalinhibition

QICS
Quantifying and Monitoring Potential Ecosystem
Impacts of Geological Carbon Storage
http://www.bgs.ac.uk/qics/

CO2 release:100‐200 kg/day

Summary• Environment assessment for offshore storage– Need for Assessment• Required by law• To gain Public acceptance– Methodology• Simulation models for leaked CO2:
– Seal layer (overburden) →Tough– Sediment layer → C.CANDI– Sea → MEC‐CO2• Database of impact assessment on marine organisms