IEAGHG Combined Monitoring and

Environmental Research Network

Meeting

26-30 August 2013

Otway injection Experiment: Measuring downhole

pressure and logging saturation

Lincoln PatersonCO2CRC/CSIRO

© CO2CRC

All rights reserved

Location of CO2CRC Otway Project

CO2CRC Otway Project aerial view

Surface facilities during test

Technique Range Comment

Pressure 10s-100s m > 1 hour to overcome wellbore storage effects

Thermal response 0.5 m Assume no convection

Pulsed neutron logging < 0.5 m Wellbore fluids affect calibration

Noble gas tracer 10-20 m Range is limited by amount of injected water. Samplingissues complicate analysis

Reactive ester tracer 2 m Limited by injected water

Dissolution test 10-20 m Limited by injected water

Core flood Core length Sample selection issues

Radius of investigation

Monitoring at Otway

• A wide variety of technologies have been deployed at Otway

• This presentation will focus on two technologies:

– Downhole pressure

– Pulsed neutron logging

Downhole pressure

• Advantages

– Very accurate, fast, continuous

– Inexpensive

– Insignificant surface disturbance

– Standard industry technology

– Can also get temperature

• Disadvantages

– No directional information (although partly offset with multiple

holes and gauges)

– Wellbore storage at short times

Stage 1 pressure during CO2 injection

Downhole gauge pressure accuracy

Twenty months of

recording during shut-in

after small injection

Tides are evident in

spectral analysis

Pressure buildup during water injection

Pressure during carbon dioxide injection

Horner plots of pressure

Pulsed neutron logging

• Advantages

– Vertical profile can help determine the thickness and variability of

saturation from an injected carbon dioxide plume

– Limited surface disturbance

– Standard petroleum industry technology

• Disadvantages

– Very limited depth of penetration into formation (< 0.5 m)

– Needs calibration (although procedure exists)

Pulsed neutron logging

– Pulsed-neutron well logging tools work by emitting bursts of

neutrons.

– As the neutrons interact with various elements in the formation,

gamma rays are generated that return to the tool. These gamma

rays are recorded and analysed to interpret the fluid saturation.

– The neutron capture cross section is heavily influenced by

chlorine and hydrogen, hence the response is largely determined

by salinity and molecules like methane and water that contain

hydrogen.

Pulsed neutron logging

– The Otway project is unique in that pulsed neutron time-lapse

logging was conducted at three stages of contrasting saturation:

when the formation was fully water saturated; after CO2 was

injected; and after water was injected to drive the CO2 to residual

saturation.

– A particular challenge for the second stage was that the space in

the borehole surrounding the tool was occupied by CO2 rather

that water, and this change needs to be calibrated out before

saturation in the formation can be determined.

– The Otway test was in water with relatively low salinity.

Pulsed neutron logging

– Two saturation profiles were generated for Otway, one using

normal processing (SIGM) for evaluation, the other using

thermal-decay-time-like processing (SIGM TDTL).

– Using the TDT-Like processing is believed to give a better result

when CO2 is in the borehole.

– The saturation profiles show that the CO2 has tended to migrate

to the top of the injection interval under buoyancy, and that the

average residual saturation is around 20% with some uncertainty

arising from the calibration.

Pulsed neutron logging results

Thermal Decay Time-Like

processing (SIGM TDTL)Normal processing (SIGM)

Relative permeability hysteresis

From:

Juanes et al (2006) WRR

Conclusions

• Downhole pressure

– Very accurate, fast, continuous, inexpensive, but no directional

information

– Advantageous having multiple gauges

• Pulsed neutron logging

– Vertical profile, but very limited depth of penetration into

formation (< 0.5 m)

– Useful for determining saturation

• Both

– Limited surface disturbance

– Standard petroleum industry technology

– Jonathan Ennis-King

– Tess Dance

– Tara La Force

– Chris Boreham

– Mark Bunch

– Charles Jenkins

– Ralf Haese

– Linda Stalker

– Barry Freifeld

– Rinjindar Singh

– Matthias Raab

– Yingqi Zhang

Acknowledgements

The authors acknowledge financial assistance

provided through Australian National Low

Emissions Coal Research and Development

(ANLEC R&D). ANLEC R&D is supported by

Australian Coal Association Low Emissions

Technology Limited and the Australian

Government through the Clean Energy Initiative

Acknowledgements

CO2CRC Participants

Supporting Partners: The Global CCS Institute | The University of Queensland | Process Group | Lawrence Berkeley National Laboratory

CANSYD Australia | Government of South Australia | Charles Darwin University | Simon Fraser University