In order to understand the interactions between surface processes and multilayer folding systems, we here present fully coupled three-dimensional numerical simulations. The mechanical model represents a sedimentary cover with internal weak layers, detached over a much weaker basal layer representing salt or evaporites. Applying compression in one direction results in a series of three-dimensional buckle folds, of which the topographic expression consists of anticlines and synclines. This topography is modified through time by mass redistribution, which is achieved by a combination of fluvial and hillslope erosion, as well as deposition, and which can in return influence the subsequent deformation. Model results show that surface processes do not have a significant influence on folding patterns and aspect ratio of the folds. Nevertheless, erosion reduces the amount of shortening required to initiate folding and increases the exhumation rates. Increased sedimentation in the synclines contributes to this effect by amplifying the fold growth rate by gravity. The main contribution of surface processes is rather due to their ability to strongly modify the initial topography and hence the initial random noise, prior to deformation. If larger initial random noise is present, folds amplify faster, which is consistent with previous detachment folding theory. Variations in thickness of the sedimentary cover (in one or two directions) also have a significant influence on the folding pattern, resulting in linear, large aspect ratio folds. Our simulation results can be applied to folding-dominated foldand-thrust belt systems, detached over weak basal layers, such as the Zagros Folded Belt.

International audienceMountain building and landscape evolution are controlled by interactions between river dynamics and tectonic forces. Such interactions have been extensively studied, however a quantitative evaluation of tectonic/geomorphic feedbacks, which is imperative for understanding sediments routing within orogens and fold-and-thrust belts, remains to be undertaken. Here, we employ numerical simulations to assess the conditions of uplift and river incision necessary to deflect an antecedent drainage network during the growth of one, or several, folds. We propose that a partitioning of the river network into internal (endorheic) and longitudinal drainage arises as a result of lithological differences within the deforming crustal sedimentary cover. Using examples from the Zagros Fold Belt (ZFB), we show that drainage patterns can be linked to the non-dimensional incision ratio R between successive lithological layers, corresponding to the ratio between their relative erodibilities or incision coefficients. Transverse drainage networks develop for uplift rates smaller than 0.8 mm yr−1 and low incision ratios (−10 < R < 10). Intermediate drainage networks are obtained for uplift rates up to 2 mm yr−1 and large incision ratios (R > 20). Parallel drainage networks and the formation of sedimentary basins occur for large values of incision ratio (R > 20) and uplift rates between 1 and 2 mm yr−1. These results have implications for predicting the distribution of sediment depocenters in fold-and-thrust belts, which can be of direct economic interest for hydrocarbon exploration. They also put better constraints on the fluvial and geomorphic responses to fold growth induced by crustal-scale tectonics

Elongation of randomly distributed fold segments and their potential linkage are important for hydrocarbon exploration because it can greatly influence the morphology of the reservoir and both migration and accumulation of hydrocarbons in antiformal traps. Here we study the effects of surface processes and the presence of a topographic slope on the different linkage modes that can occur, and how these parameters affect the required horizontal offset for perturbations to link. The proposed numerical model represents a sedimentary cover detached over a much weaker basal décollement layer. The upper surface is modified by mass redistribution, which is achieved by a combination of fluvial and hillslope processes. Several series of simulations were performed: (1) without surface processes or regional slope, (2) with regional slope only, (3) with fluvial incision and hillslope processes, and (4) with hillslope processes only. Model results show that the presence of a regional slope reduces the critical distance required for the transition between linkage and no linkage modes, whereas erosion and redeposition of sediments, on the contrary, increase this distance. The location of the saddle point, where fold segments link, and its vertical distance to the crests of the anticlines are different compared to the case without erosion or initial topographic slope, which potentially can affect the morphology of hydrocarbon traps. Moreover, both erosion and redeposition of sediments enhance the fold elongation (growth along the fold axis), once the erosion velocity exceeds the folding velocity. Model results have been compared to the Zagros Fold Belt.

High-temperature aquifer thermal energy storage (HT-ATES) may play a key role in the development of sustainable energies and thereby in the overall reduction of CO2 emission. To this end, a thorough understanding of the thermal losses associated with HT-ATES is crucial. We provide in this study a numerical investigation of the thermal performance of an HT-ATES system for a heterogeneous aquifer modelled after a well-defined region in the Greater Geneva Basin (Switzerland), where the excess heat produced by a nearby waste-to-energy plant is available for storage. We consider different aquifer properties and flow conditions, with complex injection strategies that respect maximum/minimum well pressures and temperatures, as well as legal regulations. Based on the results, we also draw conclusions on the economical feasibility (e.g., energy recovery factor vs. drilling costs) for the different strategies.Our results indicate that the true behaviour of HT-ATES systems may deviate significantly from theoretical performance derived from idealised cases. This is particularly true when the operational pressure and temperature ranges of the wells are restricted, and for heterogeneous aquifers.