Browsing by Author "Josh, M"

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    Contrasting anisotropy of velocity and electric/dielectric response in the Marcellus and Utica shales
    (Society of Exploration Geophysicists, 2018-10-28) Delle Piane, C; Josh, M; Dautriat, J; Sarout, J; Giwelli, A; Luzin, V; Clennell, B; Dewhurst, D
    The Marcellus and Utica shales in the USA have become part of the recent shale gas boom, with both shales under increased exploration and production in the past few years. The Marcellus Shale investigated here is clay-rich with a migrated organic component and has undergone significant thermal maturation, probably at temperatures in excess of 250°C (EqVr > 4). The Utica Shale investigated has both carbonate and muddy carbonate facies, also with a migrated organic component at lower thermal maturity (EqVR < 1.8). Velocity anisotropy in the Marcellus is controlled by fracturing as measurements were only possible under ambient conditions. Anisotropy of electrical/dielectric properties was controlled by organic matter maturation, with the high level of maturity resulting in proto-graphite formation and high conductivity. In the Utica shale, velocity anisotropy was controlled by organic matter and calcite alignment in the carbonate facies and clay alignment plus organics in the muddy facies. The Utica shale was highly resistive due to low porosity, low water saturation and the presence of the migrated organic component in the original pore system. © 1996–2023 Society of Exploration Geophysicists
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    New methods of mass spectrometry based on an Electron Cyclotron Resonance ion source
    (Australian Institute of Physics, 2006-12-05) Hotchkis, MAC; Josh, M; Waring, CL; Wei, T
    We are investigating the use of multiply-charged atomic ions for measuring isotopic ratios by mass spectrometry. With multiply-charged ions, molecular interferences are reduced or eliminated, as small molecules generally cannot exist as multiply-charged ions. The Electron Cyclotron Resonance Ion Source (ECRIS) provides a highly efficient means for the production of beams of multiply-charged atomic ions [1]. We have built a compact ECRIS at ANSTO for this work. Applications include the measurement of radiocarbon in small mass samples, as an alternative to Accelerator Mass Spectrometry (AMS). In our method for radiocarbon [3], the same two principles that enable AMS to work are used, but in reverse order. Molecular interferences are eliminated in the first stage of the spectrometer system, by producing high charge state ions directly from an ECRIS. 14N interference is eliminated in the second stage, by converting the beam to negative ions in a charge exchange cell. In another application of the ECRIS, we are using it with a single magnetic sector analyser to determine stable isotopic ratios such as 13C/12C and 18O/16O. Measurements of these and other stable isotopes are widely used in geo- and bio-sciences, where either natural variations are studied or isotopic tracers are used. Conventional isotope ratio mass spectrometers use molecular ions (such as CO2+) to determine such ratios. In our method, 2+ atomic ions are selected, thereby eliminating possible molecular interferences and resolving mass ambiguities that exist with the conventional molecular ion method. [1] R. Geller, Electron Cyclotron Resonance Ion Sources and ECR Plasmas, IOP, Bristol, 1996. [2] R. Middleton, in Proc. First Conf. on Radiocarbon Dating with Accelerators, H.E. Gove (ed.), Rochester, USA, 1978. [3] M.A.C. Hotchkis and T. Wei, 10th International Conference on AMS, Sept 5-10 2005, Berkeley, USA.