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Marine Monitoring Ian Wright National Oceanography Centre, Southampton, UK CCS Meeting University of Nottingham 21 st February 2012

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Marine Monitoring

Ian Wright

National Oceanography Centre,

Southampton, UK

CCS Meeting – University of Nottingham

21st February 2012

Presentation Outline

• Storage site characteristics and monitoring strategy;

• Leakage scenarios and temporal sequence of

emission;

• Current monitoring state of art;

• Marine monitoring for CO2 volume loss - challenges;

• Conclusions

CCS Storage Sites

EOR Sites

• ~ 250 km2 reservoir /

seafloor area;

• ~25-30 km3 ocean;

• point > dispersed seep

sources.

Saline Aquifers Sites

• ~22500 km2 reservoir /

seafloor area;

• ~2500-3000 km3 ocean;

• point = dispersed seep

sources.

A continuum from:

• High discharge (e.g., >200 tonnes d-1) point source

leakage (due to acute well-casing leakage or

hydro-fracturing of a seal cap) in a relatively small

depleted reservoir site,

• Low discharge (e.g., <20 tonnes d-1), dispersed

source discharges from an extensive saline aquifer

system.

• Necessitates diverse, and responsively staged

monitoring.

CCS Leakage Scenarios

Capture Transport Storage Leakage Impact

Assurance Monitoring

CCS Implementation

+ + + + =

Monitoring strategies

How do we monitor sites 250 - 22500 km2 in area, with

ocean volume of 25 - 2500 km3, with potentially known and

unknown point and dispersed seep sources?

• Baseline monitoring; • Seafloor / ocean leakage detection; • Quantification of CO2 leakage.

Point source, high discharge dispersed, low discharge leakage

Deep geophysical detection

Current regulatory monitoring practice

places significant emphasis on “deep”

geophysical monitoring of reservoir

formation, integrity of the capping

seal, and migration of CO2 within the

reservoir.

Geophysical monitoring of CO2 storage from 4-D MCS has been very successful Chadwick et al., 2003

1996 1999 2001

Very clear imaging and modelling of CO2 accumulation and expansion of “gas plume” within the reservoir.

Kaarstad, 2004

4-D Geophysical monitoring of Sleipner

Deep geophysical detection

Requires known quantitative

relationship between any geophysical

parameter and supercritical CO2, but

probably not sensitive enough for

regulation and carbon emission

trading.

Seafloor detection -1

Two additional significant opportunities

for CCS monitoring:

1. Probable that pre-cursory fluids will be emitted at the seafloor before CO2 due to buoyancy pressure of CO2 displacing stratigraphically higher fluids.

2. Seafloor, and lesser extent the overlying ocean, provide a site for more direct and quantitatively explicit measurement of CO2 flux (both as free gas and dissolved phases) that is potentially more sensitive for measurement and verification of CO2 leakage.

Leak Detection

Signature of seeping fluids on to seafloor and overlying water-column Reduced unconsolidated sediment pore fluids; • Increase Fe, [Fe (II)], Mn • Increase H2S • Decrease Eh

Reservoir formation fluids / brines; • Increase salinity • Increase temperature • Increase noble / inert gases (e.g., radon, neon, argon) CO2 fluids, free gas, dissolved phase • Increase CO2 (dissolved phase ± free gas) • Decrease pH • ?Increase trace / heavy metals

Seafloor detection - 2

Physical and chemical signatures of

CO2 loss from the seafloor, either as

direct CO2 measurement, a decrease

in pH, or emission of gas bubbles, are

arguably more tractable both in the

sense of making the observation and

understanding its relationship to CO2

volume loss.

Seafloor physical detection

Physical techniques developing

around passive and active acoustic

bubble detection that would determine

free gas leakage. Hydrophones

acoustically detect bubble oscillation

and expansion, while active sonar

record the acoustic back-scatter

response of ascending gas bubbles.

Multi-frequency acoustic data can be

inverted to determine bubble size

populations.

Seafloor chemical detection

Chemical techniques could include

elevated salinity, Mn, ferrous Fe,

acidity, H2S, and lower dissolved

oxygen.

Typical LOD’s for dissolved Fe and

Mn are nM, methane 0.2 nM, salinity

0.00001, temperature 0.005°C, and

for pH is currently 0.005-0.003 pH

unit, but could be improved to 0.0005

pH unit in the near future. Similarly, a

CO2 sensor with a detection limit of ~3

ppm is possible using microfluidic

techniques.

Monitoring platforms

MBARI

Temperature

Salinity

Dissolved oxygen

Turbidity

Conclusions (1)

• CCS sites with both large spatial seafloor extent and overlying ocean

volumes (with potentially dispersed and localised emission sources)

provide a monitoring challenge;

• Essential rationale for monitoring will be baseline studies, leakage

detection, and flux emission quantification;

• Potential CO2 leakage will have precursor fluid release of reducing

sediment pore fluids ± aquifer brines (each of which has a unique

chemical signature);

• New marine sensor and underwater platform technology is developing to

deploy long-term point observing and remotely surveyed monitoring of

the critical fluid parameters at the necessary sensitivity and spatial

scales for CCS sites (and at relative low cost);

Conclusions (2)

• Monitoring can comprise “deep” remote passive / active geophysical

imaging and direct measurement of dissolved & free gas emissions at

seafloor / ocean.

• The former is deployable now but will require inversion of applicable

geophysical parameters to CO2 flux loss;

• The latter is not yet deployable but will directly measure emission fluid

fluxes (including precursory fluids) but requires more baseline

knowledge;

• The regulatory framework emphasises monitoring of the reservoir, but if

leakage occurs, then quantification of CO2 loss is probably easier and

more accurate at the seafloor.