A seamless geo-flow modelling workflow to tackle structural uncertainty using LoopStructural and MODFLOW

Despite being one of the biggest sources of uncertainty in groundwater models, geological structural uncertainty is rarely addressed, primarily due to a lack of workflows that can generate multiple structural realisations and integrate these directly with its flow model counterpart. We present a streamlined workflow which combines LoopStructural for building complex geological models and MODFLOW 6 for flow modelling. Key features of the workflow include the use of unstructured gridding, which efficiently adapts to each structural interpretation, a full-connectivity flow formulation, and the use of structural parameters. A case study is used to demonstrate how the workflow can be used to address uncertainty in fault displacement and sub-cropping location of an aquifer. Furthermore, we demonstrate how the workflow may be used to inverse model structural parameters to tackle structural uncertainty alongside parameter uncertainty during the history matching process, negating the need for traditional Bayesian Model Averaging approaches. • Structural uncertainty is important but rarely addressed in modelling workflows • LoopStructural is combined with MODFLOW 6 to create a geo-flow modelling workflow • The workflow addresses structural uncertainty by facilitating a multi-model approach • A key feature of the workflow is the use of unstructured (DISU) grids • The workflow enables inverse modelling of structure using structural parameters.