Présentations Colloques

Oral Presentation
8.03
Session 8.03: Geometrical structure and hydrogeological properties of Hard-Rock aquifers.
Rafini Silvain
Characterizing complex aquifers using flow dimension diagnostic sequences
In hydrogeology, pumping tests are still commonly interpreted assuming Theissian conditions, which involve gross approximations of natural aquifer heterogeneities+ the quality of water resource management is consequently reduced. The petroleum industry has long used drawdown log-derivative analyses for reservoir characterization, integrating a series of analytically derived interpretative models handling non-purely Theissian heterogeneous flow. The flow dimension theory (GRF model) further diversifies the interpretative framework to non-trivial flow conditions, which more accurately represent real aquifer responses. These approaches are integrated into a flow dimension sequence diagnostic methodology, which is suitable for interpreting successive flow regimes and interactions in natural aquifers where pumping occurs. Specific flow regimes are produced by specific heterogeneous conditions encountered by the pressure front pulse propagating outwards into the aquifer, inducing flow dimension changes. We explain how these flow dimension sequences provide powerful diagnostic tools of aquifer conditions. The case of two laterally juxtaposed aquifers is used to illustrate the methodology. The hydrodynamic properties of such heterogeneous systems are numerically constrained, and a flow dimension diagnostic sequence is formalized. It is composed of two successive n = 2 radial flow regimes separated by an optional n = 1.5 fractional stage if a conductive fault embodies the interface between the aquifers. Our numerical experiments illustrate how this methodology downgrades conventional interpretative approaches by identifying subtle hydrodynamic changes, and preventing erroneous aquifer diagnostics. We promote an advanced tool for refining pump test interpretations, accounting for complex aquifer conditions that are not handled in Theis-derived methods.
France