Impact of Fluvial Sedimentary Heterogeneities on Heat Transfer at a Geothermal Doublet Scale

Virginie Hamm (1) , Simon Lopez (1)

1 BRGM - Bureau de Recherches Géologiques et Minières (BRGM)

Deep Triassic aquifers of the Paris sedimentary basin are located in clastic series which are mainly composed of fluvial deposits. They lie between 2000 and 3000 m depth and their temperature can reach 120°C in some areas. There were few attempts (3) at geothermal exploitation in the early 80's but none of them was really successful (exploitation was performed during one year on one site but injection pump failure and well damage lead to abandonment). In the context of the renewal of geothermal exploration and development in the Paris basin several new projects are now considered. As a preliminary study of the specificities of Triassic aquifers, we investigated the impact of sedimentary heterogeneities of such environments on the hydrodynamic and thermal behaviour of a geothermal doublet (1 producer well and 1 injector well). Two orientations of wells were simulated: vertical wells and horizontal wells. The main objectives are i) to study the impact of these heterogeneities and of the type of exploitation (vertical or horizontal wells) on the shape of the cold plume developing around the injector and on the thermal breakthrough time, and ii) to explore a relationship between a heterogeneous model of permeability and a more simplistic model that could potentially describe heat transfer processes at the doublet scale. For the numerical simulations we used a 3D numerical block obtained with a process-based model of fluvial sedimentary deposits (Flumy model developed by Mines Paristech). This synthetic block is 5 km long, 4 km wide and 50 m thick. It is composed of 200 cells in x and z directions for 160 cells in y direction (6.400.000 cells). For numerical limitation, it was upscaled to 100 cells in x and z directions and 80 cells in y direction (800.000 cells). Doublet simulations were performed considering two cases: the doublet is parallel to the main channels; or the doublet is perpendicular to the main channels. The simulation results were then compared to those obtained with a simple hydrogeological model with the heterogeneous model being replaced by a 2 layers model which cumulates sand bodies and clay bodies. For each simulation a passive tracer was added to the cold injected water to compare the geometry of the cooled part of the reservoir to the injected fluid paths.

Domaines: Thermique [physics.class-ph]; Thermique [physics.class-ph]; Physique Numérique [physics.comp-ph]

Virginie Hamm, Simon Lopez. Impact of Fluvial Sedimentary Heterogeneities on Heat Transfer at a Geothermal Doublet Scale. Stanford Geothermal Workshop, Jan 2012, Stanford, United States. SGP-TR-194, 18 p. ⟨hal-00661859⟩