b'AEGC 2023Short abstractsthick elastic layer shows that the strain amplitude in that layerhuman timescales on the basin scale. v maxfor CO 2and methane is of the same order as (but lower than) both in the formationare on scales of m/year, whilst values for hydrocarbon fluids are and in the fluid, and appears to scale with cables Poissons ratio.an order of magnitude smaller than for other fluids. Our results The strain in the cable is zero when cable Poissons ratio is zeroalso indicate that the fluid mobility of subsurface CO 2may be or when the borehole fluid is replaced with air. The results aresensitive to surface and near-surface temperature variations. CO 2consistent with recent laboratory and field studies, and confirmstability may be affected by surface or near-surface temperature the feasibility of borehole DAS measurements with fibre-opticvariations caused by long-term climate change or urbanisation. cables suspended in a borehole liquid (but not gas!), providedCO 2storage in geological media may be more efficient in the cable has a relatively high Poissons ratio. regions of low surface temperature, away from sources of heat and beneath a minimum depth of ~0.6 km. v maxfor hydrogen is approximately 210 times greater than those for hydrocarbons at Evaluation of a survey style absolute quantum gravimeter. the same depth. This is important for determining the migration Kyle Hardman, Christian Freier and Paul Wigley of hydrogen through geological media for both storage and exploration assessment. The increased vertical velocities must also Nomad Atomics Pty Ltd be taken into account if applying conventional basin modelling software to model hydrogen migration.Absolute gravimetry, the ability to measure the true value of the gravitational pull of objects, is of critical importance for geodesy, regional resource exploration, and long-term monitoring ofAnalysis of teleseismic earthquakes on nodal seismic underground dynamics. Unfortunately, current commercialsurveys.absolute gravimeters are large, fragile, and expensive resulting in extensive logistical problems for frequent field deploymentSteve Hearn, Bodee Bignell, John McMonagle and Shaun and field surveying. While relative gravimeters offer a smaller,Strongeasier to use alternative, they are limited by the fact that cannot provide true (absolute) measurements and drift over time. Velseis Pty LtdAdvances in quantum technologies are enabling the developmentIn recent years, nodal sensors have emerged as the default for of smaller, simpler, and more robust absolute gravimetersland seismic exploration. These systems record continuously, that address the limitations of current commercially availableand hence record a range of passive events. Although the sensor devices. By exploiting the natural properties of atoms and theiris designed for higher-frequency events, with appropriate interactions with light quantum gravimeters offer unprecedentedpre-processing it is possible to extract high quality records of stability and precision, as well as the possibility of miniaturisation.teleseismic (distant) earthquakes which are of potential interest Quantum gravimeters offer a pathway for the development ofin analysis of the crust and upper mantle near the receivers. survey style land-based absolute gravimeters right through toAspects of the pre-processing are of interest. Cross-correlations airborne drone-based gravimeters in the future. of the earthquake P-wave reveal inter-node time variations which resemble statics contours from conventional reflection We will report on the results of a comparison study betweenprocessing. Examination of time-distance variation across the the worlds first field-deployable absolute quantum gravimeternodal array provides an estimate of apparent slowness of the developed by Nomad Atomics and current commerciallyarriving P-wave. This is useful for confirmation of theoretical available state-of-the-art gravimeters. The comparison providestravel-time models, and for inferring basement dip.an assessment of the accuracy, precision and deploymentBecause of the large channel counts in modern surveys, logistics of this next-generation gravity sensor and provides astacking the teleseismic event can provide significant platform for future deployment for geophysics applications improvement in signal-to-noise. We have used stacked nodal records to infill between recordings made at other permanent Computation of vertical fluid mobility of CO 2 , methane,seismographs in Queensland. Relative travel-time residuals hydrogen and hydrocarbons through sandstones andacross the regional stations are of order 1-2 s. When teleseisms from different azimuths are examined, the raw relative-residual carbonates: Implications for CO 2storage and hydrogenpatterns appear to be inconsistent. However, ray-path back exploration. projection to upper-mantle depths reveals coherent delay patterns. The observations would be consistent with velocity Bhavik Harish Lodhia and Stuart Raymond Clark variations of order 10% occurring in the depth zone 200-300 University of New South Wales km. This supports lateral variation in the degree of development of an upper-mantle low-velocity zone, with low velocities Over the last decade, there has been an irreversible shift fromresulting from increased temperature and partial melting.hydrocarbon exploration towards carbon storage, low-carbon energy generation and hydrogen exploration. Whilst basin modelling techniques may be used to predict the migrationJust because its old doesnt mean its not good: A of hydrocarbons through sedimentary basins on geologicalintegrated geophysical case history in Archean gold timescales, there remains little understanding of how fluidsexploration.behave at the basin scale on present-day timescales. We apply the Darcy flow equation to present an algorithm thatRobert Hearstcalculates vertical fluid velocities for CO 2 , methane, hydrogenSouthern Geoscience Consultantsand hydrocarbons as a function of depth in sandstones and carbonates. This may significantly speed up calculations in basinIn this case history we look at an example of gold exploration modelling and allow calculation of vertical fluid velocities (v max ) onin the Canadian Shield of Northern Ontario. Older (30 year old) FEBRUARY 2023 PREVIEW 102'