Table AD3: Evaluation of modelling approaches. (Source: IESC, 2014.) Modelling Advantages Disadvantages Appropriate application approach/ purpose Analytical Efficient and simplified analysis of all Unable to capture complex Screening or preliminary potential impacts to groundwater geologic geometries (e.g. assessment (particularly resources non-uniformly layered where data is severely geology) or hydraulic limited) Useful when data is limited and/or conditions (e.g. coal geological and hydraulic conditions are Can be a valuable tool for anisotropy) relatively simple modelling flow in the vicinity May oversimplify hydraulic of individual wells processes Axisymmetric Useful for modelling relatively symmetric Not suitable for regional Assessment of impacts in conditions (e.g. in vicinity of coal seam scale assessment the near-well (or near-field) gas wells where geological conditions under axisymmetric Available tools do not are axisymmetric) conditions consider gas desorption and migration, dual phase flow or Can be a valuable tool for coal dual porosity, which modelling flow in the vicinity may pose inaccuracies in of individual wells predicting impacts Not capable of assessing cumulative impacts Reservoir Designed (and therefore best suited) to Reservoir assessment Assessment of impacts to assessment predict produced water volumes and groundwater (not surface depressurisation and in the near-field. water) in the near-field (but not water quality) Can model near-field produced water Used for design of coal seam gas well networks Tools do not consider water interaction Most tools account for geomechanical processes, gas desorption and migration, dual phase flow and coal dual porosity, as well as complex geological conditions Regional Tools practicable for regional scale Generally ignores Regional-scale assessment Groundwater impact assessment geomechanical processes, of impacts, water quality, Impact gas desorption and and cumulative Capable of representing complex Assessment migration, dual phase flow impacts geology, assessing cumulative impacts and coal dual porosity; this and changes to groundwater quality may create inaccuracies
Table AD3: Evaluation of modelling approaches. (Source: IESC, 2014.) Modelling approach/ purpose Advantages Disadvantages Appropriate application Analytical Efficient and simplified analysis of all potential impacts to groundwater resources Useful when data is limited and/or geological and hydraulic conditions are relatively simple Unable to capture complex geologic geometries (e.g. non-uniformly layered geology) or hydraulic conditions (e.g. coal anisotropy) May oversimplify hydraulic processes Screening or preliminary assessment (particularly where data is severely limited) Can be a valuable tool for modelling flow in the vicinity of individual wells Axisymmetric Useful for modelling relatively symmetric conditions (e.g. in vicinity of coal seam gas wells where geological conditions are axisymmetric) Not suitable for regional scale assessment Available tools do not consider gas desorption and migration, dual phase flow or coal dual porosity, which may pose inaccuracies in predicting impacts Not capable of assessing cumulative impacts Assessment of impacts in the near-well (or near-field) under axisymmetric conditions Can be a valuable tool for modelling flow in the vicinity of individual wells Reservoir assessment Designed (and therefore best suited) to predict produced water volumes and depressurisation and in the near-field. Can model near-field produced water Tools do not consider water interaction Most tools account for geomechanical processes, gas desorption and migration, dual phase flow and coal dual porosity, as well as complex geological conditions Reservoir assessment Assessment of impacts to groundwater (not surface water) in the near-field (but not water quality) Used for design of coal seam gas well networks Regional Groundwater Impact Assessment Tools practicable for regional scale impact assessment Capable of representing complex geology, assessing cumulative impacts and changes to groundwater quality Generally ignores geomechanical processes, gas desorption and migration, dual phase flow and coal dual porosity; this may create inaccuracies Regional-scale assessment of impacts, water quality, and cumulative impacts
G2-Gippsland-impact-assessment-report-June-2015.docx