b'AEGC 2021Short abstractsalong with Geoscience Australia have been acquiring large224: Predicting fluid pathways in large discontinuity spatially extensive AEM surveys with more modern AEMsystems using graph theorysystems. Most recent of which, the AusAEM programme, has been acquiring AEM over large regions of Australia. AlthoughDr Ulrich Kelka 1, Dr Stefan Westerlund1, Dr Thomas Poulet1 and these large AEM surveys are typically acquired with relativelyDr Luk Peeters1large line spacing which limit their application for fine-scale mapping, they do provide a basis for standardising historical1 CSIROdatasets, therefore providing more accurate estimates ofLarge scale discontinuity patterns such as regional scale fault- subsurface conductivity and extending their value andand fracture networks are a first order control to subsurface relevance. flow. Being able to predict dominant flow pathways in such Here, we present methodologies and results from recent AEMnetworks has implications for mineral exploration, geothermal interpretation projects in which historical AEM datasets haveenergy extraction, nuclear waste disposal, and groundwater been applied to address mapping tasks for groundwater andmanagement. Reliable numerical simulations assessing dominant mineral exploration applications. In addition to historical data,fluid pathways, are however computationally expensive.modern regional AEM data is integrated to assist with modellingHere we present an approach based on graph theory to predict historical data and to extend the application of regional AEMdominant fluid pathways in natural discontinuity systems data to finer scale domains. derived from solving a maximum flow problem on graph representations. Maximum flow algorithms are usually applied for solving flow in pipes or communication networks and we 221: The transformation of Australias first commercialassume the analogy to open fractures or highly permeable CSG field into a major gas project: How innovation andfault zones hosted in low porosity rocks. By comparing the subsurface understanding have driven success predictions obtained from maximum flow with detailed numerical simulations of fluid flow we show how to obtain Dr Mike Martin 1 and Mr Justin Gorton 1 useful information by utilizing graph algorithms and identify when full numerical simulations must be performed. For this, 1 Westside Corporation we numerically solve the fluid flow on different discontinuity The discovery of coal seam gas (CSG) in what was known asnetworks that either represent open flow conduits or comprise Dawson Valley Area dates to 1991, when it was operated bythe generic fault zone architecture built up by permeable Mt Isa Mines. It was the first commercial coal seam gas fielddamage zones surrounding a thin low-permeability fault core. in Australia, with production and sales of gas commencingWe conclude by pointing out limitations and implications of in 1996, then operated by Conoco and known as Meridianclassical network theory to fluid flow in natural discontinuity SeamGas. networks.In 2010, Westside Corporation transitioned from explorer to producer by acquiring a 51% operating interest in Meridian226: A new era for the Australian National Gravity SeamGas from Anglo American (Anglo) and Mitsui MouraGrids - adding airborne data to the mixInvestment Pty Ltd (MMI). Over the last 10 years that Westside has taken production from 5 terajoules per day (TJ/D) to 42Mr Richard Lane1, Dr Yvette Poudjom Djomani 1 and Mr Phillip TJ/D with gas being sold to both domestic and export markets.Wynne1Further acreage acquisition to the north and south effectively1 Geoscience Australiadoubled the acreage; now known as The Greater Meridian Fields.Since 1976, Geoscience Australia has produced grids of gravity The steep rise in gas demand, complex market dynamics,anomalies to support geological mapping and exploration regulatory environment, and competition from large globalapplications. The five editions of the national grids up to 2016 oil and gas operators makes it a challenging environmenthave been based on ground gravity observations, supplemented for smaller gas producers in Australia. The ability to remainon several occasions by marine gravity derived from satellite agile and employ innovative approaches to optimize fieldaltimetry and once with marine ship track gravity data. Airborne development are key success factors for Westsides growth. Ingravity surveys of significant size have been carried out for particular, the utilisation of pad-based drilling of multi-lateralgovernment organisations across Australia over the past few wells has reduced cost and surface footprint, whilst enablingyears. These surveys were carried out for a variety of reasons that more efficient drainage of reservoirs. included a need to acquire data for areas with land access issues, To support these approaches in field development, a morea desire to reduce the observation spacing over large areas, robust subsurface framework was required. Adequateand where we wished to acquire data offshore. In the planning knowledge on the distribution and variability of coal thickness,for the sixth edition of the national grids in 2019, the decision gas content/composition, structure, geomechanics, andwas made to supplement the ground gravity observations with geohazards forms the basis of the static model. It is usedairborne survey data and marine gravity derived from satellite both for resource definition and for the optimal planning andaltimetry. The addition of airborne data required a completely execution of multi-lateral wells; reducing drilling risks. different processing sequence to be devised. An important part of this processing was to vertically continue all observations to This talk will describe elements of the subsurface static model,a single smooth drape surface defined across the entire extent the advancement of drilling and completion approachesof the grids. A further important aspect of the processing was and how these have contributed to further optimization ofto ensure that all operations took into account the low pass economic development and production of gas from the Greaterfiltering inherent in airborne gravity data. The results showed Meridian Fields. clear benefits stemming from the inclusion of the airborne data. AUGUST 2021 PREVIEW 100'