British Geological Survey/NCCCS – The long-term fate of CO2 in the subsurface environment

GLOBAL CCS INSTITUTE

The long-term fate of CO2 in the subsurface environment Mike Stephenson and Jonathan Pearce

British Geological Survey/Nottingham Centre for CCS

WWW.GLOBALCCSINSTITUTE.COM


MIKE STEPHENSON

1

Head of Science (Energy) at the British

Geological Survey (BGS)

- Professor Stephenson runs the Energy

Programme at BGS including carbon

capture and storage, hydrocarbons,

renewables and unconventional energy

- Director of the Nottingham Centre for

Carbon Capture and Storage, a joint venture

between the BGS and the University of

Nottingham.

- Mike earned a BSc, MSc and PhD from

the University of Sheffield and Imperial

College, London as well as various

postgraduate teaching qualifications.


JONATHAN PEARCE

2

Job Title at Organisation

-Jonathan Pearce, over 24 years experience

with BGS.

-Involved in CO2 storage research since the

early 1990s and has led a number of

research projects on long-term geochemical

processes and the development of shallow

monitoring tools in CO2 Storage.

-His research has allowed him to collaborate

with other researchers globally including in

China, Australia, Canada, South Africa and

widely across Europe.


THE LONG TERM

FATE OF CO2 IN

THE

SUBSURFACE

ENVIRONMENT

Mike Stephenson

Jonathan Pearce

M


RELEVANT TO

• Regulation

• Public confidence

• Investment

M


VERY IMPORTANT

Building the three-dimensional static geological earth model

Using the data collected in Step 1, a three-dimensional static geological earth model, or a set of such models, of

the candidate storage complex, including the caprock and the hydraulically connected areas and fluids shall

be built using computer reservoir simulators. The static geological earth model(s) shall characterise the

complex in terms of:

(a) geological structure of the physical trap;

(b) geomechanical, geochemical and flow properties of the reservoir overburden (caprock, seals, porous and

permeable horizons) and surrounding formations;

(c) fracture system characterisation and presence of any human-made pathways;

(d) areal and vertical extent of the storage complex;

(e) pore space volume (including porosity distribution);

(f) baseline fluid distribution;

(g) any other relevant characteristics.

Regulation and public confidence

J


BASICS OF

STORAGE

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GLOBAL CCS INSTITUTE Basics of long term storage

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STORAGE AND

TIME

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TIME

„Free CO2‟

Dissolved CO2

Carbonate minerals

Storage and time

Physical trap

Solubility trap

Mineral trap

Time =?

Time =?

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CO2

Physical trap Storage and time

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CO2

Physical trap: pressure in a closed system

Storage and time

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GLOBAL CCS INSTITUTE Physical trapping: simulation

Storage and time M


CO2

After 3 power stations per year (30mt/yr) for 50 years.

The first 50 years

Storage and time

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Pressure – open system

The first 50 years

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PRESSURE: ‘CLOSED’ SYSTEM

Storage and time

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CO2 injection starts

free CO2

The first 1780 years: free CO2

Storage and time M


1999 (2.3 Mt) CO2 reaches top of reservoir. First repeat survey 2001 (4.3 Mt) Second repeat survey 2020 (20 Mt) Injection ceases 2070 2270

free CO2 CO2 in solution

[courtesy Erik Lindeberg, SINTEF]

Solubility trapping : Sleipner, the next 275 years

Storage and time: effects of impurities on solubility? J


0 s 60 s 90 s 105 s 120 s 135 s 150 s 195 s 255 s

Lab dissolution experiment

Free CO2

Saline water

[BGS Hydrothermal Laboratory] Storage and time J


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HOW COULD WE DEFINE „LONG TERM‟?

• Approaches to defining appropriate time scales of post-closure:

– When complete dissolution of CO2 occurs?

– When stability of CO2 migration is reached? (creation of CO2 reservoir)

– When a “new” THMC equilibrium is reached? (steady- state regime)

When...?

Complete dissolution

Stabilisation

J


CONFORMITY WITH MODELS • Any assessment of permanency will rely on models

– Hence the validity of static and dynamic models is critical

• Validity and robustness is tested by comparing model predictions with

past monitoring data (so-called history-matching)

• Suggested tests:

– A model matches historical flow/pressure data to within x% of the

actual measured data.

– If a static model has not been revised over e.g. 5 years, and still

adequately enables predictions to match monitored performance,

then the static model may be considered robust and representative.

• Key issues are:

– What is adequate? (e.g. within 5% or 10%?)

– The acceptable range deemed to meet measurements will vary with

parameter and is likely to be specified as a condition of the storage

permit

– What if there is more than one unique solution?

– Updates to models should be expected as more data is obtained J


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CONFORMITY WITH MODELS

• Models used to predict future performance

should be those that have been used during site

characterisation and development of monitoring

plan (subject to approved revisions)

• The regulator might want to review the changes

undertaken to models during the project

J


Things go

down....

CO2

mineralises..

Dissolution? mineralisation J


DEMONSTRATING LONG-TERM

STABILITY

• Model scenarios should be conservative –

parameters should be far from expected values

(e.g. 2δ)

• Define acceptable % deviation from stable value

(5-10%)

• Models predict eventual stability of the plume

with no evidence of potential future leakage

• Key monitored parameters should be within a

predetermined range to the future stable values

J


CONCLUSIONS

• Key trapping mechanisms are:

– Physical containment

– Residual trapping

– CO2 dissolution

– Mineral trapping

• Demonstrating long-term performance is

fundamental to transferring long-term liability to the

State.

• Storage risk goes down with time

M


ACKNOWLEDGEMENTS

Sam Holloway (BGS)

Andy Chadwick (BGS)

Mercedes Maroto-Valer (NCCCS)

Sarah Mackintosh (NCCCS)

Antony Benham (NCCCS)

Sarah Hannis (BGS)

John Williams (BGS)

Andy Newell (BGS)


QUESTIONS

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to us simply by typing

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Mike Stephenson, Kathy Hill, Jonathon Pearce

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British Geological Survey/NCCCS – The long-term fate of CO2 in the subsurface environment

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