| Title | Non-Intersected Nearby Faults: ‘Dazzling Blind’ Spot for Artificial Tracers in Inter-Well Tests (Scoping Simulations, 3) |
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| Authors | Horst BEHRENS, Julia GHERGUT, Martin SAUTER |
| Year | 2021 |
| Conference | Stanford Geothermal Workshop |
| Keywords | large-scale fault, permeability anisotropy, reservoir boundary, drain, tracer test, forced-gradient, Upper Rhine Rift Valley, Oberrheingraben |
| Abstract | This is a just a brief note, updating a small-study series (2017, 2019) concerning the ability of conservative artificial tracers, in inter-well forced-gradient flow, to ‘detect’ and quantify the properties of ‘nearby’ fractures or faults (non-intersected by the wells involved in the test). In an earlier short note (2015), we criticized the ‘bad habit’ of predicating ‘tracer test failure!’ from the objective datum of a very long residence time (a property intrinsic to fluid turnover in the georeservoir subject to the given forced-gradient flow). We now revisit a particular reservoir setting in the Upper Rhine Rift Valley, to find that a long residence time for circulating fluids may indeed be associated with ‘tracer test failure’, but in a different sense than previously incriminated. Again, this is not a test design issue, but a more general problem posed by a georeservoir class we may deem ‘very large’ in terms of fluid turnover volume under the typical conditions of a geothermal heat extraction project. With ever increasing georeservoir dimensions, the usefulness of artificial tracers in inter-well circulation may indeed become questionable, especially in the presence of large-scale faults. |