Geology & Geophysics Group
Rock physics and geotechnics
Contact: Dr Angus Best
Current research carried out in this area includes:
Seismo-electrical properties of gas hydrate reservoir sands. We are currently investigating the use of joint seismic and electrical resistivity measurements for quantifying the physical properties of seabed gas hydrate deposits (e.g., amount of methane hydrate present, degree of sand grain cementation, shear strength of the deposit under various hydrate dissociation scenarios, etc.). Work to date has concentrated on the development of seismic-electrical effect medium models validated by laboratory measurements on artificial sediments (Minshull, Sinha, Best, Sothcott & Ellis, link to Michelle Ellis PhD project site). Research funding from NERC Ocean Margins Programme.
Far left: Grain packing and shape models; near left: electrical resistivity experiment on sediment core
Seismic attenuation anisotropy in reservoir rocks (collaboration with the BGS Edinburgh Anisotropy Project). Seismic attenuation anisotropy is sensitive to the orientation of fractures in the earth, and may be a good indicator of in situ stress conditions (e.g., open or closed cracks) in hydrocarbon reservoirs. We are studying how seismic wave attenuation changes with wave propagation direction and fluid type in cracked rocks. Our approach uses laboratory ultrasonic pulse-echo and sonic resonant bar measurements on artificially cracked rock samples saturated with various pore fluids. Sponsor: Exxon-Mobil. (Link to example results)
Left: Ultrasonic pulse-echo rig and pressure cell
Seismic properties of carbonate hydrocarbon reservoir rocks (collaboration with the Centre for Integrated Petroleum Research Bergen, Norway). We are using a joint rock physics modelling and laboratory measurement approach to understand the meaning of seismic signatures in carbonate reservoir rocks (lithology, porosity, permeability and pore fluid predictions). Sponsor: Norsk Hydro. Link to recent EAGE Vienna abstract by Best et al. (2006).
Time-lapse monitoring of reservoir fluids and pressure using seismic wave attenuation (collaboration with Colorado School of Mines, University of Houston, Indian Institute for Technology Mumbai). Seismic attenuation is sensitive to fizz gas evolution and pore fluid pressure changes in oil reservoirs. We are seeking to understand how seismic signatures change with time during reservoir production for better reservoir management.
Seismic properties of coal measures. Improved seismic characterisation of coal measures is important for mining and the potential use of coal measures for CO2 storage and methane generation. We conducted a laboratory study into seismic wave attenuation in typical coal measure cores using the ultrasonic pulse-echo method. Sponsor: CSIR South Africa. (link to example results).
Seismic & geotechnical properties of sediment-hosted gas hydrates (collaboration with University of Southampton’s School of Civil Engineering & the Environment). Seafloor slopes on continental margins could become unstable if gas hydrates dissociate in response to climate change (warming oceans, sea level rise). The net result would be potentially catastrophic submarine landslides/tsunamis and the release of large volumes of greenhouse gas (methane) into the atmosphere. Understanding how sediment-hosted gas hydrates change their geotechnical properties (e.g., degree of cementation, shear strength) with hydrate content could help us to identify potentially dangerous areas of seafloor, and hence develop mitigation strategies. Crucially, linking hydrate seismic and geotechnical properties will allow us to remotely quantify the state of the seafloor through seismic surveying methods. We are currently conducting laboratory resonant column studies into seismic properties of synthetic sediment-hosted hydrates (methane, CO2) as a function of hydrate growth, morphology, and sediment type. Funding from EU Hydratech project and UK EPSRC. Researchers: Clayton, Best, Priest, Zervos & Kingston. Link to Emily Kingston PhD web page. Link to Jeff priest papers.
Acoustic properties of shallow gassy marine sediments (collaboration with the University of Southampton’s Institute of Sound & Vibration Research). Shallow seabed gas (usually methane generated by microbes) is often found offshore river estuaries and embayments, and could contribute significantly to global climate change if sufficient quantities escape into the atmosphere. We are investigating a novel acoustic method for quantifying gas volumes in seabed sediments so that the amount of global seabed methane can be better calculated. Funding from UK EPSRC. Researchers: Robb, Leighton, Dix & Best. Link to Gary Robb postdoc web page.
Acoustic properties of intertidal marine sediments
(collaboration with the University of Southampton’s Institute of Sound & Vibration Research). Relating the geoacoustic properties of velocity and attenuation to sediment geotechnical properties (e.g., lithology, water content, shear strength) is of fundamental importance to a wide range of seabed applications (e.g., seabed foundations design for oil platforms, pipeline and cable burial, etc.). We measured acoustic velocity and attenuation over the frequency range 10 – 100 kHz on beach sediments along the south coast of England to gain insight into frequency-dependent acoustic behaviour. Researchers: Robb, Best, Dix, Leighton & White. Funding from NERC. Link to Gary Robb papers in JASA & IEEE.
Go to: Rock Physics experimental facilities
