Appendix C - Examples of modelling for regional impact simulations Coal seam Modelling approach Modelling gas type adopted and tool(s) Simplifications and assumptions Uncertainty analysis Reference(s) development adopted processes included project Arrow Energy MODFLOW Regional groundwater Dual-phase and unsaturated flow, geomechanical Deterministic uncertainty Arrow Energy Surat Gas model effects, and dual porosity nature of coal all assumed analysis only: Sensitivity Pty Ltd Project, insignificant analysis for specific (2012c) (120,000 km2 model Australia aquifer parameters and domain) Assessed to be limited groundwater–surface water multiple aquifers. Effect interaction simple (non-coupled) approach to – Well field represented by of sensitivity-adopted groundwater–surface water interaction adopted individual abstraction parameter values on wells Coal horizontal anisotropy not modelled calibration performance discussed Cumulative impacts Coal seams not modelled independently of coal assessed (including measures Indicated significance of CSG developments) Hydraulic connectivity of geologic structural features hydraulic parameters and range of drawdown ignored magnitudes (Hydraulic fracturing not proposed to be undertaken by Arrow, thus its potential impact was not required to be assessed)
Appendix C - Examples of modelling for regional impact simulations Coal seam gas development project Modelling tool(s) adopted Modelling approach type adopted and processes included Simplifications and assumptions Uncertainty analysis Reference(s) Arrow Energy Surat Gas Project, Australia MODFLOW Regional groundwater model (120,000 km2 model domain) Well field represented by individual abstraction wells Cumulative impacts assessed (including CSG developments) Dual-phase 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 seams 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 Arrow Energy Pty Ltd (2012c)
csg-modelling-groundwater-impacts.docx