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CO2-EOR and Carbon Geo-storage; A UK Perspective

Jon Gluyas & Simon MathiasDepartment of Earth Sciences

Durham University

UKCCSC, Durham, UK

September 2012Email: j.g.gluyas@durham.ac.uk

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Outline� Part 1 CO2-EOR in context

� Displacement & sweep efficiency

� Thief zones & gravity segregation

� WAG, SWAG and FAWAG

� Summary

� Part 2 Application & UK Potential

� The prize

� CO2 supply and facilities longevity

� Costing the earth & saving the planet

� The CO2-EOR heritage

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Denver Unit of the Wasson Field, West Texas

NETL CO2-EOR Primer (2010)

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Thermal methods

Steam injection leads to reduced oil viscosity.

Air injection leads to in situ combustion.

Gas injection

Includes injection of natural gas, nitrogen and CO2.

Injected gas displaces oil.

If reservoir pressure is sufficiently high the gas dissolves into the

oil leading to reduced oil viscosity and volume swelling.

Chemical methods

Polymers are used to change the viscosity of injection water

Surfactants (like detergent) are used to reduce surface tension

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Reegtien (2010) SPE 136034

Maturation curve for EOR

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� Improve displacement efficiency (micro-

scale)

� Improve sweep efficiency (macro-scale)

What are we trying to do?

Al-Shuraiqi et al.

12th European Symposium on IOR

From SPE 97270

Residually

trapped oil

Rock

grainsFlow of oil

Adapted from CO2CORC

Water

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Electron photomicrograph of a

sandstone

1 mm

Pore-space

Pore-

throat

Displacement efficiency (micro-scale)

(Price, 1996)

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If the rock is water wet, water adheres to the sides of

the pores due to surface tension.

Residual trapping

(Extracted from Tchelepi, 2009)

OilWater

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If the rock is water wet, water adheres to the sides of

the pores due to surface tension.

As water moves upwards oil is displaced.

But as the water passes through the pore throat,

some of the oil is trapped.

(Extracted from Tchelepi, 2009)

OilWater

Residual trapping

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Surfactants (like detergent) reduce surface tension

allowing oil to connect into a continuous phase.

Application of surfactants

OilWater

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Sweep efficiency (macro-scale)

� Viscous fingering

� Poor conformance

� Gravity segregation

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Viscous fingeringMobility ratio is essentially the ratio

of displacing to recovering fluid

viscosity. Very small (or large)

mobility ratios lead to poor sweep.

Ultimately, the front can become

unstable and viscous fingering can

occur.

Mobility ratio can be favourably

modified by increasing CO2 viscosity

by polymer addition.

[ ] 21)1(2 −+−= γγ DD hx

(Zhang et al. 1997, Chem Eng Sci 52:37-54)

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Poor conformance

ProductionInjection

CO2

Oil

CO2 often travels

preferentially through

high permeability thief

zones.

ProductionInjection

CO2

Oil

Sealing thief zones

with gel or foam can

lead to significantly

enhanced sweep

efficiency.

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Identification of thief-zones

See for example Butler et al. (2009, Hydrogeology Journal 17:1849–1858) or Li et al. (2010, SPE 116286)

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(Mathias et al. 2006, Water Resour. Res. 43: W07443)

Identification of flowing horizons

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Gravity segregation

ProductionInjection

CO2

Oil

De

pth

Permeability

De

pth

PermeabilityProduction

Injection

CO2

Oil

Use foam or gel to

reduce permeability.

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Application of gel for gas cut-off

Production

Gas

Oil

Water

See for example Al Dhafeeri et al. (2008, SPE 114323)

Localised application of gel reduces permeability

under gas cap leading to reduced gas production

due to coning.

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WAG: Water Alternating Gas

Pulsing of water and gas leads to reduced composite

mobility due to residual trapping of gas. However, gravity

segregation can still be an issue.

SWAG: Simultaneous Water And Gas

Simultaneous injection of water and gas at the top and

bottom of reservoir, respectively. Should reduce gravity

segregation but often limited by poor injectivity.

FAWAG: Foam Assisted WAG

Same as WAG but with surfactant. Combined surfactant and

gas leads to foam generation which reduces the mobility of

the gas.

See Aladasani and Bai (2010, SPE 130726) and Anwan et al. (2008, SPE99546)

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Summary� The aim of CO2-EOR is to mix residing oil with CO2 to

reduce oil viscosity and increase oil volume.

� The challenge is to improve displacement (micro-

scale) and sweep (macro-scale) efficiency of the CO2.

� Gravity segregation and thief zones are significant

problems for large carbonate reservoirs.

� Gels, foams and WAG strategies represent a range of

mitigating technologies (which reduce CO2 mobility),

which can be used in various combinations to

optimise various effects.

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CO2-EOR – Texas� Initiated 1970s in response to oil crisis� Texas at forefront of technology & leads the way today� Permian Basin in NW Texas is the primary injection area� 1000s km 32” pipeline & associated infrastructure developed� Natural & anthropogenic CO2 sources used

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CO2-EOR – Technology

� Water Alternating Gas (WAG)• CO2 injected to swell oil and increase fluidity• H2O injection to displace oil to production wells

� Gravity Stable Gas Injection (GSGI)• CO2 injected at field crest• Stabilising pressure and promoting gravity drainage

� Miscible flood – critical CO2 dissolved in oil • swelling oil, viscosity reduced surface tension reduced

� Immiscible CO2 displacement• Partial dissolution in oil may reduce viscosity substantially

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Schematic WAG

http://www.netl.doe.gov/scngo/Petroleum/publications/eordrawings/eordraw.html

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How much additional recovery?

� West Texas 4-12% of STOIIP (observed)• 60+ projects (~100 world wide)

� US DOE 7-14% of STOIIP (calculated)� Institute for Energy (Netherlands) 9-18% STOIIP of

UK, Norwegian & Danish fields (calculated)

� This study (2009) UK additional 3-8bn bbl� DECC (2012) UK mean additional recovery 5.7bn

(5-15% of STOIIP)

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How much CO 2 is used?

� 0.1 to 0.45 pore volumes injected� Typically 1 (net*) tonne of CO2 injected delivers 2.5 to 5

bbl oil (average 3 bbl)� Tapered WAG (decreasing CO2 volumes) most effective

*Net = total injected - recycled

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UK Oil Fields

Moray Firth &

Central N Sea

Viking

Graben

From Gluyas & Hichens, 2003

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UK Offshore Oil Reserve

Proven Probable P+P Possible Maximum

Cumulative Oil Production in millions tonnes (bnbbl)

3315

(24.9)

Estimated Ultimate recovery in millions tonnes (bnbbl)

3723(27.9)

361(2.7)

4048(30.4)

360(2.7)

4444(33.3)

https://www.og.decc.gov.uk/information/bb_updates/chapters/Table4_3.htm

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UKCS Recovery Factors ~45%

� High End - Piper – recovery factor >70%� Low End - Lyell – recovery factor ~5%

Jayasekera &

Goodyear SPE 75171

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UKCS & West Texas Oil Fields

UKCS

� Sandstones� Most > 2.7 km deep� Most > 90ºC� Light oil ~35-40API� Typically high quality

(permeability – 100s mD)� Line drive water floods for

secondary recovery� Low well density

West Texas

� Sandstones & dolomites� 1.2 to 1.8 km deep� 15-60ºC� Light oil 30-42API� Typically low quality

(permeability 4-16 mD)� Pattern floods

l� High well density

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UKCS vs West Texas

� West Texas – incremental oil recovery 4-12% of STOIIP

� CO2 is expected to be miscible (or nearly so) with current conditions in the UKCS oil reservoirs

� UKCS fields more permeable and at higher temperature than those in West Texas – both factors may favour the North Sea

From Goodyear et al, IEA EOR Caracas 2002

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UKCS – The Prize

� Assuming UKCS:• Reserve of 30,000mmbbl• STOIIP 30,000/0.45 = 67,000mmbbl

� From West Texas 4-12% additional recovery of STOIIP• Yields 2,700 – 8,000 mmbbl technical reserves

• Requiring ~1 t CO2 per 3bbl*

� For ~3,000 mmbbl, ~1,000 Mt CO2 required

*range 2.5 to 5 bbl/tonne

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http://www.decc.gov.uk/en/content/cms/statistics/climate_change/climate_change.aspx

� Scotland 19mm tonnes� North East 21mm tonnes� Yorkshire 27mm tonnes

100km

UK oil province

UK Industrial CO 2 production 2007

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Supply & Demand

� Assuming all industrial CO2 from the eastern UK could be available for CO2-EOR yields 60-70mm tonnes per annum

� Over a 15-25 year period (ie typical CO2-EOR project length) this would use 1 billion tonnes CO2 …. the quantity required to optimise CO2-EOR in the North Sea

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Are UK Oil Fields Ready For CO2-EOR?

Arbroath Claymore

MaureenNinian

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The Time is Right (but don’t wait)

Jayasekera & Goodyear SPE 75171

UKCS Shrinking Infrastructure

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UK Security of Supply

DECC publication 2008

Shortfall in 2010

~15 mm tonnes

Equivalent to

~300,000 bopd

Equivalent to

Initiating ~1/3 potential CO2-EOR projects

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Costing the Earth?

� For the North Sea• There is no CO2 infrastructure• There is no ‘ready’ source of CO2

• The first project will be an enormous commitment

37Capture, Transportation, Injection & FacilitiesMorecambe, Magnus & Miller

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Saving the Planet

� 1bbl of oil contains ≡ 0.42 t CO2 after combustion� 1bbl produced by CO2-EOR requires between 0.4 and 0.2 t

CO2

� At best – the process is carbon neutral� At worst – the process is halving emissions

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CO2-EOR Heritage

� The CO2 production from eastern UK could ‘power’CO2-EOR in the North Sea for 10-15 years per project, over ~30 year period

� It could deliver:• Improved security of oil supply• Infrastructure usable for carbon

capture • Increased tax revenues over

current projections

Deep aquifer storage area