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