This study focuses on the contrasted architectural elements of the two late Pleistocene alluvial fill sequences (T1 and T2 attributed to the Late Saalian and Weichselian) of the upstream Seine River alluvial plain, la Bassee, and constitutes the first estimation of the sediment volumes associated to these glacial cycles along this river. Estimations of the incised valley and valley fill spatial distribution are obtained by cokriging of data from 546 wells collected from the French national repository and a digital elevation model (DEM) of the present topography. The well stratigraphic attribution is given by the homogenised geomorphological map of la Bassee. We calculated the sediment volume of eroded material for the T1 sequence to be 1.70 10(9) m(3) and of valley fill deposits to be 1.18 10(9) m(3). This corresponds to a mean thickness of 6.1 m. By contrast, volumes of the T2 sequence are one-third smaller, 1.23 10(9) m(3). The T2 mean thickness is very similar with 5.8 m. The alluvial plain is divided into four reaches representing a typical assemblage of the T1 and T2 incision style and valley fill deposits. Along the downstream reaches (1 - Montereau-Bazoches, 2 - Bazoches-Grisy), the T2 proportion per kilometer are close to the alluvial plain mean value (reach 1: 76%; reach 2: 69%, la Bassee: 71%), the T2 mean incised valley width corresponds to three quarters of the T1 (4 km). In the middle upstream reach (3 - Grisy-Courceroy), the T2 proportion is the largest (92%), the T2 mean incised valley width is the largest and comparable to the T1 (5.5 km). Along the upstream reach (4 - Courceroy-Rornilly), the T2 proportion is the lowest (53%) and the T2 incised valley (2 km wide) is enclosed within the T1 incised valley (4 km wide). The rate of exported material, though, is the same for each sequence in any reach (31%). The spatial pattern of the T1-T2 deposits coincides largely with the presence of a knickpoint along the T2 paleothalweg (downstream part of reach 4, slope face 1.5 parts per thousand), suggesting that the knickpoint had a large influence on the fluvial processes. The toe of the knickpoint (reaches 3 to 1, slope 0.24 parts per thousand) was the site of the most efficient erosion of the T1 deposits. We propose that the change of slope favored diversion of the channel path. Upstream of the knickpoint face (upstream part of reach 4, thalweg slope 0.34 parts per thousand), the incision processes were dominated by incision, avulsions or multithreading with limited lateral migration as indicated by the numerous T1 relicts preserved across valley. The sediment export corresponds to a mean incision rate of 40 m/Ma during the last 300 kyr; a fairly low value for the Paris basin, suggesting a low uplift area north of the Massif Central. Such contrast between the fluvial processes during the T1 and T2 sequences is most likely to be looked for in the climatic conditions that existed at the onset of the incision as no local controls for the knickpoint location could be identified such as active faults, substrate heterogeneity, or flow modifications. The lower sediment flux and the knickpoint associated to the T2 sequence suggest a transient river profile and valley incision at the end of the climatic transition associated to the Weichselian (T2). (C) 2018 Published by Elsevier B.V.

In landscapes dominated by fluvial erosion, the landscape morphology is closely related to the hydrographic network system. In this paper, we investigate the hydrographic network reorganization caused by a headward piracy mechanism between two drainage basins in France, the Meuse and the Moselle. Several piracies occurred in the Meuse basin during the past one million years, and the basin's current characteristics are favorable to new piracies by the Moselle river network. This study evaluates the consequences over the next several million years of a relative lowering of the Moselle River (and thus of its basin) with respect to the Meuse River. The problem is addressed with a numerical modeling approach (landscape evolution model, hereafter LEM) that requires empirical determinations of parameters and threshold values. Classically, fitting of the parameters is based on analysis of the relationship between the slope and the drainage area and is conducted under the hypothesis of equilibrium. Application of this conventional approach to the capture issue yields incomplete results that have been consolidated by a parametric sensitivity analysis. The LEM equations give a six-dimensional parameter space that was explored with over 15,000 simulations using the landscape evolution model GOLEM. The results demonstrate that stream piracies occur in only four locations in the studied reach near the city of Toul. The locations are mainly controlled by the local topography and are model-independent. Nevertheless, the chronology of the captures depends on two parameters: the river concavity (given by the fluvial advection equation) and the hillslope erosion factor. Thus, the simulations lead to three different scenarios that are explained by a phenomenon of exclusion or a string of events.

On earth, landscape morphology is mainly controlled by rivers evolutions and their interactions with hillslopes. But hydrographic network may be re-organized by stream capture and modify deeply the relief. This transition may be induced by several mechanisms (diversion, headward erosion, avulsion, or subterranean filling up). It has interested numerous scientists since a long time (Davis 1895, Blache 1943, Lesson-Quinif 2001 & Le Roux-Harmand 1997-2009...). Here we focus on stream piracies by headward erosion, when an actively eroding low level stream (called the captor) encroaches on the drainage of a nearby stream flowing at a higher level (called the diverter) and diverts part of the water of the higher stream. During the last decades, several landscapes evolution models (LEM) have been developed to quantify the topography evolution with diffusion and advection equations. These models play an important role in sharpening our thinking to better understand the interaction between landscape evolution processes. LEM were developed basically to simulate erosion, tectonic and climate at different scales of time and space. But, these models were not designed to describe specific mechanisms as the stream capture. It's one of the aims of this work to evaluate LEM for this purpose. In this paper, we develop a 1D model based on LEM equations to investigate the stream piracy by headward erosion responses to climatic or tectonic changes. This model incorporates the most common equations used in quantitative geomorphology; diffusion in hillslope, advection in river (detachment-limited mode) and an inequality based on slope and drainage area for the limit between these two domains (Montgomery and Dietrich, 1988). First, simulations on analytical cases highlight the stream head progression mechanism, and the results indicate that this progression rate is mainly controlled by the slope at the captor source. Consequently, the aggradation of the diverter or (and) the incision of the captor accelerate the process. Then, a predictive study with an improved version of GOLEM (software developed by Tucker & Slingerland in 1994) on the Meuse basin shows that several piracies may probably occur in the future. A comparison with the 1D model gives similar results. The simplicity and the flexibility of the 1D model allow complex simulations in the Meuse basin taking into account: lithological differences of outcropping layers, Meuse deposition tendency, etc. Once the 2D simulations or topography analysis locate potential captures, 1D simulation may intensively be used, as it presents many advantages; weak execution time, simple limits conditions setting, less time for data preparation, etc. Consequently, a sensitivity analysis to estimate piracies ages is realized with the developed 1D model.

Landscape evolution results of antagonistic processes. In the Paris basin (France): tectonic uplift seems to be globally balanced by river incision. But the dynamic equilibrium of the relief can be disturbed by other processes and singularities may appear. A remarkable example is observed in the Meuse basin (NE of France), where the river is actually perched at more than +50m above the surrounding valleys: the Marne valley to the west and the Moselle valley to the east. This special morphology is the result of several stream piracies (at the expense of the Meuse) which has interested numerous scientifics since a long time (Davis 1895, Blache 1943, Lesson-Quinif 2001 & Le Roux Harmand 1997-2009. . . ). The most important ones of these piracies are: 1) the well-known capture of the Haute-Moselle by a tributary of the Meurthe near Toul; 2) at the north-west, the capture of the river Aire by the Aisne. On-going evolution suggests that such events can be expected in the long-term future. Where and when next streams piracies could occur, what consequences may be expected? Our approach is to simulate the dynamic evolution of the landscape with an improved version of GOLEM (Geomorphic / Orogenic Landscape Evolution Model - LEM), this software was developed by Tucker & Slingerland in 1994 (http://csdms.colorado.edu/wiki/Model:GOLEM). The LEM characterizes erosion by incorporating diffusion and advection equations whose parameters must be fixed, according to local conditions. First simulations for next millions years with " detachment-limited " mode, let us locate several potential captures of the Meuse river by tributaries of the Moselle, therefore inducing a complete reorganization of the hydrographic network. The results of the localizations agree with local topography/geometry analysis. The first capture provoques a knickpoint propagation and a significant lowering of the upstream part of the Meuse's basin. Downstream, the orientation of the abandoned valley "slowly" inverts and a new Meuse's tributary appears (like the Agron's river after the Aire's capture). The asymmetry of these processes shows the importance of the localization and the order of the piracies on post-capture landscape evolution. In these simulations, unlike piracy-order, timing depends widely on the physical parameters of the model: in first approximation, durations are proportional to the bedrock erodibility. More complex simulations are in process, taking into account lithological differences of outcropping layers, Meuse deposition tendency...

The use of gas-storage caverns in salt formations is a growing industry that continues to gain momentum because it allows gas to be injected and withdrawn at high rates compared with other underground gas-storage systems such as porous rock systems.In order to predict cavern production performances, cavern thermodynamics behaviour must be studied by higher accuracy approaches. This behaviour is extremely related to the temperature distribution in the surrounding formations. During the leaching process, the thermal equilibrium of the rock salt surrounding the cavern is extensively disrupted. The purpose of this paper is to study the heat transfer problem during the leaching process and to develop a thermal model that can be easily used in field applications. The results of this work will be the input data for the prediction of the gas temperature and pressure during cavern gas-storage operation phase. Moreover, the developed model can find its use in the design of salt caverns since it can be coupled with geometrical modelling of salt dissolution codes. Copyright (C) 2008 John Wiley & Sons, Ltd.

A process-based model that simulates fluvial erosion in the River Somme Valley over the last million years is presented here. The model takes into account lithology and climatic influences and allows the simulating of undercapacity and overcapacity sediment transport behaviour. The model has been calibrated to a family of terraces within the River Somme Valley. When matched to this field data, simulation trials suggest that bedrock incision occurred principally from 120 to 60-40 kyr during the last climatic cycle and before the last glaciation. The impact of a progressive tectonic uplift (c. 60 m over c. 1 million years) on the River Somme has also been studied here. Extended over a longer period of time, the simulations suggest that 1 million years ago the profile of the River Somme had a lower slope gradient than today, with little relief throughout the Paris Basin.

The well trajectories becoming more and more complex (Extended Reach Drilling, Horizontal or Multilateral Drilling, Ultra-Deep Drilling, 3D wells….), the associated drillstring composition being unconventional and the material being used to its operating limit, the necessity to have a tool that predicts realistically forces, bending moment and contact loads along the wellbore is essential. To simulate the mechanical behavior of the drillstring, the industry generally uses a stiff-string model for the bottom bole assembly (BHA) to predict drilling trajectories, and a soft-string model for the entire drillstring to calculate torque and drag.The conventional soft-string model gives a good approximation of forces and contact loads in the drillstring for very smooth well trajectories, but is inappropriate when the trajectory becomes tortuous (micro or macro-tortuosity) or complex, as the drillstring no longer contacts the low side of the borehole.An advanced numerical method has been applied to address the 3D mechanical problem of a complete drillstring moving and freely rotating inside a wellbore: computation of the unknown contacts between the drillstring and the wellbore. As this new model does not use the time consuming finite element analysis, it can be used in real-time drilling operation at the rig to monitor torque and drag. For the first time, it is even possible to perform simultaneously a torque and drag, buckling and directional analysis while drilling.The power of a 3D visualization of the drillstring deformed inside the wellbore enables to localize easily contact loads on any drillstring component, from the drilling bit (including side force at the bit and tilt) to the top drive or rotary table (hook load and rotary torque at surface), facilitating drilling problems analysis.This paper will describe the fundamentals of the model developed and shows the differences between the conventional soft-string model and the advanced stiff-string model in terms of tension, torque and contact points between the drillstring and the wellbore, for many actual wells. With the help of the 3D visualization software, this paper will show the cases where the drill pipe contacts the high side of the borehole, or goes up to the right or the left side of the borehole depending on the right or left turn rate of the well trajectory. This new model should improve significantly the torque-drag and buckling calculations and the understanding of the drillstring contributions to overall drilling performance.