Improving our understanding of fluid transport in rocks – CO2 sequestration

Tim SendenDepartment of Applied MathematicsResearch School of Physics and Engineering

• Underground storage of CO2 has been proposed as a means of mitigating climate change through ghg emissions.

• Several major challenges to address– Volume of CO2 that can be stored within a given

geological formation

– Proximity to CO2 source (powerplant, gas field)

– Long term storage security (e.g. leakage rate must be less than 0.01% per year)

Introduction

• CO2-rock interactions are a source of uncertainty in assessment of CO2 storage viability– Change injectivity (porosity, permeability etc)– May alter seal rock integrity– Mineral trapping / contaminant liberation

… but supercritical CO2 is an unusual beast!!

Facts: Above 31°C and 73 atm (not uncommon in reservoirs/aquifers);• ½ as dense as water, and 1/10th as viscous but flows like a liquid.• while it does not mix with water is does react to make the water acidic• it dissolves in hydrocarbons.

• Saline aquifer

• Sleipner (Norway)

• Globally ubiquitous

• Need to ensure security to avoid groundwater contamination (true for any lithology)

• Mineral trapping small volumetrically but potentially important (changes to flow properties)

Image source: Statoil

So how to study this troublesome fluid in microscopic pores within rock?

The X-ray micro-Tomography Facility Micro-focus

X-ray source

Rockspecimen

Double helical trajectory means very high fidelity data from micron to centimeter scale

Physical Parameters Reservoir DescriptorsElectrical Conductivity Oil SaturationDielectric Permittivity Water SaturationNeutron Gas SaturationBorehole Pressure PorositySound Velocity PermeabilityNMR ResponseGamma-ray x-sectionCapillary Pressure

How does fluid permeability correlate to other observables ?

We must manage our hydrocarbon resources efficiently

Instead of a single data point we can extract 100’s from a single core

1 mm3 sandstone showing simulated flow lines

Triaxial cell•8 – 25 mm cores•Beryllium cell•Axial strain < 1000 atm•Confining pressure < 100 atm•No creep over 8 hr•Designed for scCO2

at present using analogue fluids

Simulation

Experiment

Mardie Green Sand – Barrow Is, WA

Courtesy of Rowan Romeyn (Hons. student).

Native state After exposure to CO2 equivalent

Using analogue fluids

ANU/UNSW spin-off

• Christoph Arns **• Tomaso Aste• Holger Averdunk• Gareth Crook• Andrew Fogden• Abid Ghous• Stephen Hyde• Anthony Jones• Alexandre Kabla

* VizLab ANUSF** UNSW

• Vanessa Robins• Rowan Romeyn• Mohammad Sadaatfar• Arthur Sakellariou• Tim Sawkins• Adrian Sheppard• Rob Sok• Michael Turner• Trond Varslot• Paul Veldkamp

The Digicore Consortium has included; Saudi Aramco, ExxonMobil, Shell, Chevron, BP, Total, Schlumberger, Baker Hughes, Abu Dhabi Onshore, Maersk, Petronas, PetroBras, Japan Oil & Gas, ONGC (India), BHP, BG, Conoco Philips, FEI, Digitalcore

• Andrew Kingston• Munish Kumar• Mark Knackstedt• Shane Latham• Evgenia Lebedeva• Ajay Limaye *• Jill Middleton• Glenn Myers• Val Pinczewski **

Since 2000

Since 2006

Since 2009

Australian National Low Emissions Coal Research and Development(ANLEC)

In partnership with Digitalcore and ANU received a multi-million dollar grant to develop methods to investigate CO2 – rock interactions in Australian aquifers. 3 years.

Building an open access data repository, visualisation and simulation platform for tomographic data

2011