Percolation parameter and percolation-threshold estimates for 3D random ellipses with widely-scattered distributions of eccentricity and size

In fractured materials of very low matrix permeability, fracture connectivity is the first-order determinant of the occurrence of flow. For systems having a narrow distribution of object sizes (short-range percolation), a first-order percolation criterion is given by the total excluded volume that is almost constant at threshold. In the case of fractured media, recent observations have demonstrated that the fracture-length distribution is extremely large. Because of this widely-scattered fracture-length distribution, the classical expression of the total excluded volume is no longer scale invariant at the percolation threshold and has no finite limit for infinitely large systems. Thus, the classical estimation method of the percolation threshold established in short-range percolation becomes useless for the connectivity determination of fractured media. In this study, we derive a new expression of the total excluded volume that remains scale invariant at the percolation threshold and that can thus be used as the proper control parameter, called parameter of percolation in percolation theory. We show that the scale-invariant expression of the total excluded volume is the geometrical union normalized by the system volume rather than the summation of the mutual excluded volumes normalized by the system volume

Characterization of the velocity field organization in heterogeneous media by conditional correlation

International audienceThe purpose of the present work is to quantify the correlation structure of simulated velocity fields in heterogeneous permeability fields and to discuss how to represent it in upscaled transport models. We investigate the velocity field correlation structure for multinormal log permeability fields. The simulated velocity distributions are analyzed in a Lagrangian framework, i.e., along the particles' paths.To quantify the different spatial organization of low- and high-velocity zones, we condition the estimated velocity correlation length and time on the initial particle velocity. The velocity correlation length is found to increase with the initial particle velocity, following a power law. Such an effect is likely due to the channeling of high-velocity zones, which implies that particles keep memory of their initial velocity over longer distances for high initial velocities than for low initial velocities. Two distinct regimes are identified for the velocity correlation time. For low initial particle velocity the correlation time is controlled by the large time needed to escape from the low- velocity zones. For high initial particle velocity it is controlled by the large time needed for particles to sample the whole velocity field, in particular low- velocity zones. One of the consequences of these results is that for such velocity fields the nonlinear dependence of both the correlation length and time on the particle initial velocity restricts the se of spatial or temporal Markovian assumptions for modeling velocity transitions in effective transport models

Temporal evolution of age data under transient pumping conditions

International audienceWhile most age data derived from tracers have been analyzed in steady-state flow conditions, we determine their temporal evolution when starting a pumping. Our study is based on a model made up of a shallowly dipping aquifer overlain by a less permeable aquitard characteristic of the crystalline aquifer of Plœmeur (Brittany, France). Under a pseudo transient flow assumption (instantaneous shift between two steady-state flow fields), we solve the transport equation with a backward particle-tracking method and determine the temporal evolution of the concentrations at the pumping well of CFC-11, CFC-12, CFC-113 and SF6. Apparent ages evolve because of the modifications of the flow pattern and because of the non-linear evolution of the tracer atmospheric concentrations. To identify the respective role of these two causes, we propose two successive analyses. We first convolute residence time distributions initially arising at different times at the same sampling time. We secondly convolute one residence time distribution at various sampling times. We show that flow pattern modifications control the apparent ages evolution in the first pumping year when the residence time distribution is modified from a piston-like distribution to a much broader distribution. In the first pumping year, the apparent age evolution contains transient information that can be used to better constrain hydrogeological systems and slightly compensate for the small number of tracers. Later, the residence time distribution hardly evolves and apparent ages only evolve because of the tracer atmospheric concentrations. In this phase, apparent age time-series do not reflect any evolution in the flow pattern

Mutation Analysis of NR5A1 Encoding Steroidogenic Factor 1 in 77 Patients with 46, XY Disorders of Sex Development (DSD) Including Hypospadias

BACKGROUND: Mutations of the NR5A1 gene encoding steroidogenic factor-1 have been reported in association with a wide spectrum of 46,XY DSD (Disorder of Sex Development) phenotypes including severe forms of hypospadias. METHODOLOGY/PRINCIPAL FINDINGS: We evaluated the frequency of NR5A1 gene mutations in a large series of patients presenting with 46,XY DSD and hypospadias. Based on their clinical presentation 77 patients were classified either as complete or partial gonadal dysgenesis (uterus seen at genitography and/or surgery, n = 11), ambiguous external genitalia without uterus (n = 33) or hypospadias (n = 33). We identified heterozygous NR5A1 mutations in 4 cases of ambiguous external genitalia without uterus (12.1%; p.Trp279Arg, pArg39Pro, c.390delG, c140_141insCACG) and a de novo missense mutation in one case with distal hypospadias (3%; p.Arg313Cys). Mutant proteins showed reduced transactivation activity and mutants p.Arg39Pro and p.Arg313Cys did not synergize with the GATA4 cofactor to stimulate reporter gene activity, although they retained their ability to physically interact with the GATA4 protein. CONCLUSIONS/SIGNIFICANCE: Mutations in NR5A1 were observed in 5/77 (6.5%) cases of 46,XY DSD including hypospadias. Excluding the cases of 46,XY gonadal dysgenesis the incidence of NR5A1 mutations was 5/66 (7.6%). An individual with isolated distal hypopadias carried a de novo heterozygous missense mutation, thus extending the range of phenotypes associated with NR5A1 mutations and suggesting that this group of patients should be screened for NR5A1 mutations

Le retrait du Cholstat® (le déroulement et ses implications)

La cérivastatine (Cholsta® ou Staltor®), une statine 2ème génération largement prescrite, est subitement retirée du marché le 16 juillet 2001. Cette statine est mise en cause dans des décès par rhabdomyolyses. Ce retrait annoncé par la presse internationale a provoqué la panique auprès des acteurs de la santé et des consommateurs du produit. La gestion du retrait et son déroulement sont observés de l'intérieur de l'entreprise Fournier qui commercialisait le Cholstat® avec une description des répercussions marketing, financières et humaines à plus ou moins long terme sur l'entreprise. Afin de limiter ces impacts et parer rapidement au plus urgent, une cellule de crise est mise en place pour analyser, communiquer et mettre en place des mesures correctives coordonnées. Une méthodologie générale de gestion de crise est détaillée. La réactivité et la communication de l'entreprise à ses différents partenaires et consommateurs reste essentielle dans la gestion de crise d'un retrait de produit.ROUEN-BU Médecine-Pharmacie (765402102) / SudocSudocFranceF

Reconstructing the 3D fracture distribution model from core (10 cm) to outcrop (10 m) and lineament (10 km) scales

Considering the role of fractures in hydraulic flow, the knowledge of the 3D spatial distribution of fractures is a basic concern for any hydrogeology-related study (potential leakages in waste repository, aquifer management, ...). Unfortunately geophysical imagery is quite blind with regard to fractures, and only the largest ones are generally detected, if they are. Actually most of the information has to be derived from statistical models whose parameters are defined from a few sparse sampling areas, such as wells, outcrops, or lineament maps. How these observations obtained at different scales can be linked to each other is a critical point, which directly addresses the issue of fracture scaling. In this study, we use one of the most important dataset that have ever been collected for characterizing fracture networks. It was collected by the Swedish company SKB for their research program on deep repository for radioactive waste, and consists of large-scale lineament maps covering about 100 km2, several outcrops of several hundreds of m2 mapped with a fracture trace length resolution down to 0.50 m, and a series of 1000m-deep cored boreholes where both fracture orientations and fracture intensities were carefully recorded. Boreholes are an essential complement to surface outcrops as they allow the sampling of horizontal fracture planes that, generally, are severely undersampled in subhorizontal outcrops. Outcrops, on the other hand, provide information on fracture sizes which is not possible to address from core information alone. However linking outcrops and boreholes is not straightforward: the sampling scale is obviously different and some scaling rules have to be applied to relate both fracture distributions; outcrops are 2D planes while boreholes are mostly 1D records; outcrops can be affected by superficial fracturing processes that are not representative of the fracturing at depth. We present here the stereology methods for calculating the 3D distribution model from both outcrop and well fracturing observations, and we discuss the consistency between the along-core fracturing intensity profile, the outcrop fracture traces, and the lineament maps. In the Forsmark site investigated by SKB, we conclude that the power-law distribution model is statistically consistent from core scale (80 mm) to outcrop scale (~10 m); the consistency with the lineament scale (10 km) is still questionable. An important subhorizontal fracturing exists at shallow depth, but it does not seems to affect the statistics of highly dipping fractures

Fault zones properties and groundwater resources in crystalline rocks

International audiencepas de résum

Structural controls of groundwater resources in fractured rock aquifers

International audienceAs hard rock aquifers are gaining in importance for groundwater resources, significant advances have been made in the last twodecades in characterizing their structure and understanding their hydrogeological functioning. Two conceptual models have beenproposed so far to explain qualitatively the geological controls of water productivity. These models propose that groundwaterresources in hard rock aquifers are typically associated with the weathered zone or with regional sub-vertical faults outcroppingin the surface. Still, they fail to explain the hydraulic functioning of a few sites worldwide including the Ploemeur aquifer (Brittany,France). This system in particular hosts a slowly dipping highly transmissive fractured zone - a contact between overlyingmicaschists and a leucogranite - in addition to a set of sub-vertical normal faults. Numerical simulations on a simple conceptualhydrogeological model show that either the transmissivity or the deepening of a regional fractured zone control the resources infractured media. The fractured zone indeed always allows some recharge to occur, even if in its vicinity only; and this, whatever theproperties of the overlying rock. Conversely, when the fractured zone dips slowly, aquifer recharge extends spatially because of athinner overlying unit and as such, even local fractured zones can bear a significant resource. In such conditions, the flow withinthe fractured zone may even become the limiting factor for groundwater occurrence. Local (kilometric) sub-horizontal structurescan thus be as productive as sub-vertical regional faults. In the Ploemeur aquifer, the sub-horizontal geological contact then likelycontrols the recharge of the site and its high productivity. Comparison with other field cases in Brittany confirm the effect of thedip of the fractured zone on productivity. Simulation results not only reveal additional favourable hydrogeological conditions, theyalso show that the flow patterns in shallowly dipping fractured zone differ strongly from those located in regional subvertical faultzones. Such differences carry significant consequences in terms of management as well as identification methods

Porosity and fluid velocities in the upper continental crust (2 to 4 km) inferred from injection tests at the Soultz-sous-Forêts geothermal site

International audienceA heat exchanger was created at the French Hot Dry Rock geothermal site using a doublet of boreholes at a depth of 3600–3800 m. After hydraulic stimulation, this exchanger was tested during a long-term circulation trial from July to November 1997. Tracer tests were carried out during the circulation trial.An analysis of the tracers indicates a connected porous volume in the range of 0.5 to 2.5 × 106 m3, with a connected porosity of the order of 0.9 to 2.3%. These values are one order of magnitude higher than values obtained by extrapolation from petrophysical investigation of the boreholes. This result is interpreted as being due to the connection of the major faults to a dense network of 2nd-order structures.Fluid circulation velocities inferred from the tracer test are of the order of 0.25 to 0.36 m/h. Velocities derived from observation of the migration of fresh fluids after injection into the granite during stimulation tests are of the same order of magnitude (0.02 to 0.17 m/h), yielding hydraulic conductivity estimates of 6.6 10−8 to 2.3 10−6 m/s−1. Both the pressure gradient during the circulation test and the density gradient are related to freshwater injection, and can be considered as possibly equivalent to temperature and hydraulic gradients in the Rhine graben, at least during some specific geological events such as the Alpine uplift phases. Thus, the test shows that fluid migration can occur in the upper continental crust exhibiting “reservoir” properties, and these should be taken into account in large-scale modelling. These properties are in good agreement with a proposed scenario of evolution involving active fluid migration during the Eocene (Alpine uplift phase). It also supports the hypothesis of seawater-derived saline fluids stored in old fractured shield rocks, which implies deep seawater circulation in the continental crust

Flow in multiscale fracture networks

The paper aims at defining the flow models, including equivalent permeability, that are appropriate for multiscale fracture networks. As a prerequisite of the flow analysis, we define the scaling nature of fracture networks that is likely quantified by power-law length distributions whose exponent fixes the contribution of large fractures versus small ones. Despite the absence of any characteristic length scale of the power-law model, the flow structure appears to contain three length scales at the very maximum: the connecting scale, the channelling scale, and the homogenization scale, above which the equivalent permeability tends to a constant value. These scales, including their existence, depend on the fracture length distribution and on the transmissivity distribution per fracture. They are basic in defining the flow properties of fracture networks