Applying Hydrocarbon Systems Analysis and Basin Hydrodynamics to Onshore Gas in Australia

Early in the development cycle of onshore gas such as coal seam gas (CSG), operating company Environmental Impact Statements and regulatory agency assessments need to consider the potential for gas development impacts on other resources including groundwater. To a large degree, this depends firstly on our ability to forecast the volume of associated water anticipated to be co-produced and secondly, on our ability to forecast the continuity and performance of seals (top, intraformational and fault seal) within the stratigraphic succession. Unfortunately, this is also when there is the least amount of data to constrain the problem and history shows that we tend to overestimate the volume of associated water and overestimate the hydraulic continuity of the strata. We use a hydrocarbon systems analysis approach to identify the migration of hydrocarbons and non-hydrocarbon gases through the strata at different geological times. These fingerprint migration and leakage pathways that relate to the seal performance on a geological time-scale. Outcomes from this approach can be explored within a risk assessment framework for resource interaction on a human time-scale that will inform the development of an effective measurement, monitoring and verification strategy.