A combined geochemical and μCT study on the CO2 reactivity of Surat Basin reservoir and cap-rock cores: porosity changes, mineral dissolution and fines migration

Geological storage of CO generally involves injection of a CO stream into a high porosity and permeability reservoir, contained by one or more overlying low permeability formations. Sandstone reservoirs and associated cap-rocks of targeted CO storage sites therefore have distinct properties such as porosity and mineral contents. Their geochemical response or reactivity to injected supercritical CO and associated changes in porosity, and permeability affecting scaling, mineral trapping, injectivity, or migration can therefore be very different. Six drill core samples including quartz-rich sandstones, calcite cemented sandstones, and feldspar or clay-rich cap-rocks from a proposed demonstration site in the Surat Basin, Australia, were characterized before and after reaction with pure supercritical CO and low salinity formation water. The quartz-rich sandstones have low reactivity, and maintain high porosities with visible pore connectivity after reaction, they are unlikely to be affected by scaling. Kaolin and fine grain movement observed via μCT and SEM could have the potential to open or plug pores, potentially increasing or decreasing permeability and CO injectivity. Calcite cemented sandstones had the greatest measured change in porosity after reaction via calcite dissolution. Narrow angular channels were formed in the calcite cement around framework grains, extending through to the center of the sub-plug in the courser grained rock, and surface roughness increased. Solution pH was however quickly passivated. The highest concentrations of Ca, Mn, Sr, and Mg were released to solution from calcite dissolution. Clay (and feldspar) rich cap-rock core had mainly microporosity and the smallest initial pore throat diameters associated with clays. Small changes to μCT calculated porosities after reaction were related to a decrease in chlorite X-ray density, and dissolution of patchy carbonate minerals. Pores were disconnected in μCT images, except for some created horizontal connection along a sandy lamination in a cap-rock. Dissolved concentrations of Ca, Fe, Si, Sr, Mn, Li and Mg increased via dissolution of both carbonate and silicate minerals. Dissolved Ca, Fe, Mn and Mg from silicate minerals in the cap-rock were available for longer term mineral trapping of CO. Potential increases in porosity and migration will be highest in the calcite cemented zones, while clay-rich cap-rocks could be expected to maintain integrity. There is a low likelihood of mineral trapping or scaling in the quartz rich lower Precipice Sandstone. Overlying rocks can provide Fe, Mg, Ca for mineral trapping of CO as ferroan carbonates such as siderite, ankerite and dolomite over longer time scales when pH is buffered. Changes to porosity, mineral content, and water chemistry after pure CO reaction observed here and in other published studies were dependent on mineral content and fluid accessibility. These results could be generalized to other sandstone reservoirs where it is expected to inject CO. The results can also be used to validate geochemical models to build longer term predictions

Investigation of an optically induced superstrate plasma for tuning microstrip antennas

Optically induced electron-hole plasmas in silicon are used to perform radiation pattern tuning. The antenna is a slot loaded microstrip patch and the effect of illumination is shown to produce beam switching in the radiation patterns of certain modes while other modes are left unaffected. The structure is specifically designed to make the best use of currently available miniature laser sources to form a compact tunable package. Modelled and measured results for tuning of the radiation patterns and frequency response are presented. The effect of the losses incurred by the plasma along with the losses in the optically transparent ground plane are quantified in both simulation and measurement. This forms the basis for designing other types of optically tunable miniature antennas based on the structure presented

Great Artesian Basin authigenic carbonates as natural analogues for mineralisation trapping

This project is the first to comprehensively investigate the controls on the formation of authigenic carbonates in low salinity, siliciclastic aquifers of the Great Artesian Basin. These processes are\ua0natural analogues for mineralisation trapping of CO2 during geo-sequestration. Calcite is the main carbonate present. Analyses included elemental composition, C and O stable isotopes, fluid inclusion analyses including\ua0gas isotopes, SEM-EDS and QEMSCAN, and X-ray micro-CT scanning.\ua0The samples reflect\ua0a variety of fluid origins, compositions, and temperatures of precipitation.\ua0Differentiating between carbonate formed via different mechanisms, and determining controls on the extent of authigenic carbonate formation, could lead to options for engineered accelerated mineralisation in reservoirs

Spatio-temporal processes drive fine-scale genetic structure in an otherwise panmictic seabird population

When and where animals breed can shape the genetic structure and diversity of animal populations. The importance of drivers of genetic diversity is amplified in island populations that tend to have more delineated gene pools compared to continental populations. Studies of relatedness as a function of the spatial distribution of individuals have demonstrated the importance of spatial organisation for individual fitness with outcomes that are conditional on the overall genetic diversity of the population. However, few studies have investigated the impact of breeding timing on genetic structure. We characterise the fine-scale genetic structure of a geographically-isolated population of seabirds. Microsatellite markers provide evidence for largely transient within-breeding season temporal processes and limited spatial processes, affecting genetic structure in an otherwise panmictic population of sooty terns Onychoprion fuscatus. Earliest breeders had significantly different genetic structure from the latest breeders. Limited evidence was found for localised spatial structure, with a small number of individuals being more related to their nearest neighbours than the rest of the population. Therefore, population genetic structure is shaped by heterogeneities in collective movement in time and to a lesser extent space, that result in low levels of spatio-temporal genetic structure and the maintenance of genetic diversity

Updated Constraints on the Minimal Supergravity Model

Recently, refinements have been made on both the theoretical and experimental determinations of the i.) mass of the lightest Higgs scalar (m_h), ii.) relic density of cold dark matter in the universe (Omega_CDM h^2), iii.) branching fraction for radiative B decay BF(b \to s \gamma), iv.) muon anomalous magnetic moment (a_\mu), and v.) flavor violating decay B_s \to \mu^+\mu^-. Each of these quantities can be predicted in the MSSM, and each depends in a non-trivial way on the spectra of SUSY particles. In this paper, we present updated constraints from each of these quantities on the minimal supergravity (mSUGRA) model as embedded in the computer program ISAJET. The combination of constraints points to certain favored regions of model parameter space where collider and non-accelerator SUSY searches may be more focussed.Comment: 20 pages, 6 figures. Version published in JHE

Search for Charged Higgs Bosons at LEP

A search for pair-produced charged Higgs bosons is performed with the L3 detector at LEP using data collected at centre-of-mass energies between 189 and 209GeV, corresponding to an integrated luminosity of 629.4/pb. Decays into a charm and a strange quark or into a tau lepton and its neutrino are considered. No significant excess is observed and lower limits on the mass of the charged Higgs boson are derived at the 95% confidence level. They vary from 76.5 to 82.7GeV, as a function of the H->tv branching ratio

Search for Charged Higgs Bosons in e+e- Collisions at Centre-of-Mass Energies up to 202 GeV

A search for pair-produced charged Higgs bosons is performed with the L3 detector at LEP using data collected at centre-of-mass energies between 192 and 202 GeV, corresponding to an integrated luminosity of 233.2 pb^-1. Decays into a charm and a strange quark or into a tau lepton and its neutrino are considered. The observed events are consistent with the expectations from Standard Model background processes. Including data taken at lower centre-of-mass energies, lower limits on the charged Higgs mass are derived at the 95% confidence level. They vary from 67.4 to 79.9GeV as a function of the H^+/- --> tau nu branching ratio

Search for R-parity Violating Decays of Supersymmetric Particles in e+e- Collisions at LEP

A search, in e^+e^- collisions, for chargino, neutralino, scalar lepton and scalar quark pair-production is performed, without assuming R-parity conservation in decays, in the case that only one of the coupling constants lambda_ijk or lambda''_ijk is non-negligible. No signal is found in data up to a centre-of-mass energy of 208GeV. Limits on the production cross sections and on the masses of supersymmetric particles are derived

The exposure of the hybrid detector of the Pierre Auger Observatory

The Pierre Auger Observatory is a detector for ultra-high energy cosmic rays. It consists of a surface array to measure secondary particles at ground level and a fluorescence detector to measure the development of air showers in the atmosphere above the array. The "hybrid" detection mode combines the information from the two subsystems. We describe the determination of the hybrid exposure for events observed by the fluorescence telescopes in coincidence with at least one water-Cherenkov detector of the surface array. A detailed knowledge of the time dependence of the detection operations is crucial for an accurate evaluation of the exposure. We discuss the relevance of monitoring data collected during operations, such as the status of the fluorescence detector, background light and atmospheric conditions, that are used in both simulation and reconstruction.Comment: Paper accepted by Astroparticle Physic

Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment

This paper describes an analysis of the angular distribution of W->enu and W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with the ATLAS detector at the LHC in 2010, corresponding to an integrated luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and the missing transverse energy, the W decay angular distribution projected onto the transverse plane is obtained and analysed in terms of helicity fractions f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw > 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour, are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017 +/- 0.030, where the first uncertainties are statistical, and the second include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables, revised author list, matches European Journal of Physics C versio