Modelling regional impacts Table AD2: Modelling Approaches, Simplifications and Uncertainty Analysis at a Project Level. (Source: Commonwealth of Australia, 2014.) Coal seam gas Modelling Modelling approach Simplifications/ Uncertainty Analysis Project tool used Processes involved Assumptions /Author Arrow Energy Regional groundwater model and unsaturated flow, geomechanical effects, and Deterministic uncertainty analysis only: Surat Gas Project, (120,000 km2 model domain) dual porosity nature of coal all assumed insignificant Sensitivity analysis for specific aquifer MODFLOW Australia (Arrow parameters and multiple aquifers. Effect Well field represented by individual Assessed to be limited groundwater–surface water interaction Energy Pty Ltd, of sensitivity-adopted parameter values abstraction wells simple (non-coupled) approach to groundwater–surface – 2012) on calibration performance discussed water interaction adopted Cumulative impacts assessed Indicated significance of hydraulic (including other coal seam gas Coal horizontal anisotropy not modelled parameters and range of drawdown developments) Coal not modelled independently of coal measures magnitudes Hydraulic connectivity of geologic structural features ignored (Hydraulic fracturing not proposed to be undertaken by Arrow, thus its potential impact was not required to be assessed) Australia Pacific FEFLOW Regional groundwater Geomechanical effects, and dual porosity nature of coal all Deterministic uncertainty analysis only: LNG assumed insignificant Sensitivity analysis (two extreme cases Model (172,740 km2 model only) for aquifer, recharge and stream Project, Australia domain) Simple (non-coupled) approach to groundwater–surface conductance parameters. (Australia Pacific water interaction adopted Finite element method LNG, 2010; Effect of sensitivity-adopted parameter Coal horizontal anisotropy not modelled (FEFLOW) allows improved Geoscience values on calibration performance definition of complex geology Coal seams not modelled independently of coal improved Australia and discussed definition of complex geology Dual-phase flow implicitly Habermehl, 2010) Indicated significance of hydraulic accounted for by reducing coal Dual-phase flow implicitly accounted for by reducing coal parameters and range of drawdown seam permeability seam permeability magnitudes Cumulative impacts assessed Cumulative impacts assessed (including coal seam gas (including other coal seam gas developments) developments)
Modelling regional impacts Table AD2: Modelling Approaches, Simplifications and Uncertainty Analysis at a Project Level. (Source: Commonwealth of Australia, 2014.) Coal seam gas Project /Author Modelling tool used Modelling approach Processes involved Simplifications/ Assumptions Uncertainty Analysis Arrow Energy Surat Gas Project, Australia (Arrow Energy Pty Ltd, 2012) MODFLOW Regional groundwater model (120,000 km2 model domain) Well field represented by individual abstraction wells Cumulative impacts assessed (including other coal seam gas developments) and unsaturated flow, geomechanical effects, and dual porosity nature of coal all assumed insignificant Assessed to be limited groundwater–surface water interaction – simple (non-coupled) approach to groundwater–surface water interaction adopted Coal horizontal anisotropy not modelled Coal not modelled independently of coal measures Hydraulic connectivity of geologic structural features ignored (Hydraulic fracturing not proposed to be undertaken by Arrow, thus its potential impact was not required to be assessed) Deterministic uncertainty analysis only: Sensitivity analysis for specific aquifer parameters and multiple aquifers. Effect of sensitivity-adopted parameter values on calibration performance discussed Indicated significance of hydraulic parameters and range of drawdown magnitudes Australia Pacific LNG Project, Australia (Australia Pacific LNG, 2010; Geoscience Australia and Habermehl, 2010) FEFLOW Regional groundwater Model (172,740 km2 model domain) Finite element method (FEFLOW) allows improved definition of complex geology Dual-phase flow implicitly accounted for by reducing coal seam permeability Cumulative impacts assessed (including other coal seam gas developments) Geomechanical effects, and dual porosity nature of coal all assumed insignificant Simple (non-coupled) approach to groundwater–surface water interaction adopted Coal horizontal anisotropy not modelled Coal seams not modelled independently of coal improved definition of complex geology Dual-phase flow implicitly accounted for by reducing coal seam permeability Cumulative impacts assessed (including coal seam gas developments) Deterministic uncertainty analysis only: Sensitivity analysis (two extreme cases only) for aquifer, recharge and stream conductance parameters. Effect of sensitivity-adopted parameter values on calibration performance discussed Indicated significance of hydraulic parameters and range of drawdown magnitudes
O2-Otway-impact-assessment-report-June2015.docx