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This paper reports a study of water dynamics in a carbonate vadose zone (VZ). This study is performed in the experimental natural site of Saint-Emilion located in an underground quarry (Gironde, France). For this, two geophysical properties are used: the time domain reflectometry method (TDR) which provides the volumetric water content and electrical properties which provides the spatial water distribution. The dephasing and amplitude attenuation of the water content front were measured and modelled. Physical properties of the porous medium (porosity, permeability and effective diffusivity) can explain the water transfer process in VZ. The electrical resistivity tomography (ERT) gives a series of 2D images of water dynamics in VZ. Variations in water content induce changes in the electrical properties of the medium such as electrical resistivity. Using the time-lapse method, it is possible to model the evolution of saturation over time. The reliability of these electrical tools was confirmed by laboratory measurements.

International audience; This work is part of the Aquifer CO2-Leak project and aims to understand, quantify and model the environmental impact of a CO2 leak on water quality in the carbonate freshwater aquifer as well as CO2-water-carbonate interactions. The experiment has been performed within an Oligocene carbonate underground quarry located in Saint-Emilion (France).A water charged with dissolved CO2 was injected in the aquifer through a borehole. Downstream, seven wells were fitted with in-situ probes which automatically measured physicochemical parameters. Periodic water samplings in all wells have been undertaken to determine the elemental concentrations by ion chromatography.The spread of CO2 in the groundwater was monitored as a function of time and was observed to influence the various physicochemical parameters. Five parameters seem to be excellent indicators for monitoring a gas plume during CO2 geological storage in regard to our results: electrical conductivity and pH, and Ca2+, HCO3−, and CO2(aq) concentrations.The interaction between CO2 and limestone is highlighted by a saturation index (SI) calculated with PhreeqC software. It shows (i) a slight trend to dissolution of calcite in the injection well (SI < 0) linked to the reaction process between CO2-H2O-CaCO3 and (ii) a transport process via diffusion for the observation wells with a SI≃0.The evolution of physicogeochemical signatures in the aquifer allows us to understand the reactive and transport processes that occur during the migration of a gasified water plume in the context of leakage from a geological storage reservoir. Our results will make possible to model a leakage in a complex natural reservoir.

This work is part of the Aquifer CO2-Leak project, started in 2018 for a 4-years duration and that aims at evaluating the impact of CO2 leakages from a geological storage site and developing new monitoring tools and methodologies. The present study aims to understand, quantify and model the environmental impact of a CO2 leak on water quality in the carbonate freshwater aquifer and understanding CO2-water-carbonate interactions.This research has been performed on an experimental site located in Saint-Emilion (Gironde, France), in an underground quarry within a 30-meter-thick carbonate formation dated to the Upper Oligocene. The facies vary from wackestone to grainstone, and are associated with high values of porosity (from 25 to 45%) and permeability (between 5 and 20 D). A gas mixture, composed of CO2 (90%), He (9%) and Kr (1%), was injected in the aquifer through a borehole located upstream hydraulic gradient. The total injected volume was 200 liters for 1h30.The seven other boreholes downstream in the injection well were fitted with in-situ probes which automatically measured pH, electrical conductivity, and CO2 fraction. Periodic water samplings have been undertaken, to determine the elementary concentrations by ionic chromatography. The spread of dissolved CO2 in the freshwater aquifer has influenced the physicochemical parameters at the various measurement points and thus has been followed in the time.The interaction between the CO2 and the limestones causes the dissolution of the calcite, releasing Ca2+ and CO32- in the solution, which are distributed between H2CO3, HCO3- and CO32-. The comparison of the results before and after the passage of the plume highlights a dissolved CO2 concentration increase, combined with an increase of electrical conductivity and temperature, as well as a decrease in pH values.The evolution of the physicogeochemical signature in the aquifer allow to understand the reactive and transport processes during a migration of a CO2 plume in a leakage context. The acquisition of these results will make possible to model a leakage in a complex natural reservoir. Electrical conductivity and pH measurements seem to be excellent indicators for monitoring a gas plume during CO2 geological storage. The laboratory analyzes lead to better understand the CO2-water-carbonate interactions produced at the field scale and the relationships with petrophysical properties.Batch measurements study the evolution of the electrical conductivity, monitored as a function of the CO2 concentrations. Comparison of experiments using only water, water and sand or water and limestone, have shown that only the presence of carbonate ions allows an increase in this geophysical parameter. By means of these different tools and measures, the propagation of a CO2 leak will be followed through the modification of physicochemical parameters in the aquifer. This should also change the electrical resistivity values across the unsaturated zone. The electrical resistivity tomography should be a complementary tool in order to support these results, and to represent a 3D image plus time of the CO2 plume.

An ultra-diffusive leakage experiment was performed on the pilot site of Saint-Emilion near Bordeaux in France. It consisted in the injection of 85% CO2 and 5% of each He, Kr and CH4 in a vertical well with a very low injection pressure. This study allowed the development of an automated tool that continuously monitored the gas phase within the vadose zone. Measurements showed that the gas plume had a heterogeneous spatial and temporal variation. Mathematical calculations performed on the time series of the gas species showed that diffusive transport mainly occurred in the porous media. However, every stage of the migration could not be driven by diffusive process as shown by the exponential regression. A non-identified transport mechanism may have occurred during the increase of concentration. He was proven to be a suitable temporal tracer for a CO2 leakage as it was a good temporal precursor. Even if the process was weaker than in the former injection experiments, Kr could show help foreseeing the extent of the gas plume within the pilot site. CH4 was also shown to be an excellent temporal precursor of CO2 arrival. The amount of gas migrating through the preferential path identified in the previous experiment was weaker than in the previous study. Moreover, the monitoring showed that a significant amount of injected gas migrated deeper in the vadose zone. The ratios CO2/Kr vs. CO2/He and the evolution of CO2/Kr, CO2/He and CO2/CH4 put in evidence three groups of probes. The first consists in the subsurface probes and is characterized by a potential reactive transport of CO2 through the vadose zone such as gas dissolution in the aqueous phase. The second group gathers the closest probes to the injection point and underlines a very slow return to baseline value through diffusion. The third group is characterized by a competition between the process occurring in the first and second group. Isotopic measurement of Kr could not bring relevant information about the CO2 fates into the vadose zone. However, it shows the possible presence of mechanism transport such as vertical flux and gravitational settlings. Observations from both of all the leakage experiment and future laboratory experiment could improve our understandings of the buffering zone and help to foresee CO2 leakage for future storage site.

The paper aims to study the general characteristics of the reservoirs of different reservoirs system in Paleozoic formations in Ghadames and Jefarah basins, located in Libya and in Tunisia. For that, more than twenty six wells were used to illustrate how reservoir properties such as porosity and permeability changes through time from a proximal to a distal sedimentary environments . Reservoirs systems are analysed at two different scales: i) reservoirs scale using data analysed from geological and petrophysical software for reservoir property analysis and constructing of five stratigraphic cross sections through the area have been reconstructed between twenty six wells; ii) core scale using different laboratory petrophysical analysis. The Paleozoic reservoirs are characterized by a large range of siliciclastic reservoirs extending from Cambrian to Permian . Nine main Paleozoic reservoir systems are identified in these two basins these are; the Hasawnah, Hawaz and Mamouniyat Formations (Lower Paleozoic), Akakus, Tadrart, Ouan Kaza and Tahara Formations (Middle Paleozoic) and M'rar and Asadjefar Formations (Upper Paleozoic). These reservoir systems are connected with two major hydrocarbon source rocks known as; the Lower Silurian Tanezuft Formation and Middle-Upper Devonian Awaynat Wanin Formation. The study shows that depositional facies and position within the paleogeographical setting influenced the evolution and the heterogeneity of reservoirs properties.

The Apulian carbonate margin is widely preserved across the Adriatic domain and has been extensively studied in the south of Italy. In Albania, Oligocene–Pliocene fold-and-thrust tectonics led to widespread exposure of the Apulian Platform and associated Ionian Basin carbonates. However, the portion linking the platform to the basin is missing, preventing a direct reconstruction of the platform margin. Syn-sedimentary folding and faulting are recognized in the uppermost part of both the platform and basinal/slope series. Mass transport deposits (MTDs) occur within the platform succession incorporated into well-bedded intertidal (stromatolites) to shallow-subtidal (rudist packstones) sedimentary sequences. They display significant lateral variability which is accompanied by both rigid and soft deformation structures. Spectacular slumps made up of sediment density flow deposits are recognized in the adjacent Ionian Basin. The lateral extent of basal shear surfaces, syn-sedimentary faults and folds evidenced in the Ionian Basin points toward multiple regional tectonic triggering events affecting the Apulian Platform margin at that time. Bio- and chrono-stratigraphic analyses suggest that the triggers occurred during the late Campanian – early Maastrichtian. Beyond the obvious interest from a stratigraphic point of view, the study of these events recording the dismantling of the Apulian carbonate platform allows for a better understanding of the triggering mechanisms and the sedimentary characteristics of MTDs and slumps at a basinal scale.

The objective of this work is to understand and characterize how dissolved CO2 concentrations can influence physicochemical parameters, in particular the electrical conductivity and pH. In previous work, a CO2 injection experiment was carried out directly in a freshwater aquifer within an Oligocene carbonate underground quarry located in Saint-Emilion (Gironde, France). Different parameters emerged as excellent indicators for monitoring a gas plume during CO2 geological storage, especially the electrical conductivity and pH. We tried to reproduce field observations on a laboratory scale by batch experiments and measurements on Hassler cell, and to make the link between the geochemical results (electrical conductivity, pH, CO2 concentrations) and the electrical properties (electrical resistivity index) depending on the saturation state of the carbonate rock. A calibration line has been highlighted, making it possible to link the relation between electrical conductivity-CO2-pH. This line is only valid for Saint-Emilion limestones at the injection well because it is dependent on the petrophysical properties of the environment. As field observations are reproducible in the laboratory, this calibration line allows to pass from one scale to another by combining different results, and estimate the CO2 concentrations obtained for such values of electrical conductivity and pH.

The objective of the Aquifer-CO2Leak project is to get insights into carbon dioxide CO2 migration in aquifers within the context of Carbon Capture and Storage (CCS) and to test the different equipment necessary for CO2 monitoring. The underlying idea is to develop an experiment in the saturated zone (phreatic) of the underground limestone quarry located at Gironde department (France). It consists in injecting water, carrying dissolved gases (CO2 and krypton) and a fluorescent molecule, under controlled conditions. In this paper, we present the dimensioning study of the experiment by numerical simulations carried out using the simulator CooresFlow (IFPEN's in-house simulator for reactive transport in porous media). The important experiment parameters (injection flow rate, injected volume, the time to return in system equilibrium and wells location) were successfully estimated. In particular, the variation of species concentration in time and space was simulated and analyzed to define an experimental measurement schedule for the planned survey. Finally, a sensitivity analysis of the uncertain model parameters is presented. We found that the water table level and the dispersivity of the porous medium appear to be the most “sensitive” parameters.

Twenty eight wells with its geological well reports and well logs from the Paleozoic reservoirs of the Ghadames and Jefarah basins (Libya) illustrate how reservoir properties changes laterally and vertically through time (from a proximal to a distal setting). The reservoirs in the study area are spread over a large range of siliciclastic succession with the prospective section extending from Cambrian to the Permian. Six stratigraphic cross sections through the study area have been reconstructed to illustrate the vertical and lateral reservoir extensions. It was noted that the reservoir properties vary laterally and vertically between the proximal and distal deposits with the average porosity decreasing towards the distal part of the basin.

The sedimentology and tectonics and their relationship of the Paleozoic series that fill the Ghadames basin and its northern extension consisting of the Jefarah basin in Libya and Tunisia was studied. These formations belong to the Gondwana cycle and are typically interpreted as being deposited in a cratonic basin truncated by the Hercynian unconformity . This study is based on wells. The stratigraphic correlation between the wells is based on the definition of second order cycles, electrofacies and electrosequences notion. This allowed to produce isopach maps of facies distributions and to reconstruct the paleogeography of the different stratigraphic units. These data allow to address the nature of the deformation and also clarifies the behavior of active high regional areas during the Palaeozoic. The Paleozoic succession in the Ghadames and Jefarah basins can be divided into five first order sequences, bounded by major tectonic unconformities with sequence durations of 40–70 Ma. Within these five sequences 18 s order sequences (10–40 Ma) were differentiated, describing Sequence Boundaries (SB), Maximum Flooding Surfaces (MFS) and sedimentological characteristics.

Integrated in the peri-Adriatic domain, the Ionian Basin extended along a NW-SE direction during the Late Cretaceous, limited on its sides by the Apulian and the Kruja platforms. The basinal/slope succession was studied in seven outcrops exposed in the Albanian fold-and-thrust belt. Sedimentological investigations, supported by bio- and chronostratigraphy were performed on calcareous Upper Cretaceous hemipelagites, gravity-flow deposits and slumps. The western part of the basin was studied, revealing a strong influence of the Apulian margin, alternatively shedding sediment basinward, by means of a tectonically controlled edge. The Late Albian to Cenomanian period is characterized by the settling of muddy debrites along the margin. A deep basinal environment characterizes this period which prolongs until the Santonian, with no significant influx of the platform basinward. This sedimentary setting abruptly changed at the end of the Santonian, with an important influx derived from both platforms. Coarsening and thickening upward sequences show a progressive increase in sediment shedding during the Campanian. The Late Campanian-Early Maastrichtian period points out a major change on the resedimentation processes with the settling of several slumped units reworking thick sediment packages. The latter can be traced along the Apulian margin, testifying of instabilities along the edge of Apulia.

International audience; From a natural underground cavity and two locations situated in a well, three CO 2 injections have been designed and performed under controlled conditions in order to study its migration along the carbonate vadose zone and to test geochemical and geophysical techniques. After the understanding of the natural CO 2 dynamics and the establishment of a baseline, some numerical simulations have been performed to help to optimize the monitoring strategy (spatially and temporally). A mixture of CO 2 + noble gases has been injected and the results show that CO 2 subsurface leakage can be anticipated thanks to these inert chemical gases used as tracers (He + Kr).The geochemical and geophysical monitoring approaches are very complementary.

Experimental observations of electrical resistivity variations were carried out in a field site (CO 2 -Vadose project) in order to investigate the evolution of this geophysical property in response to possible leakages of geologically sequestered CO 2 . The dynamic evolution of electrical resistivity was measured using time-lapse electrical resistivity tomography during a sub-surface leakage of CO 2 released under controlled conditions in a cavity of about 9 m 3 located in an abandoned limestone quarry. The experimental CO 2 induced leakage was performed to study the gas migration in a carbonate vadose zone. Initial electrical resistivity tomographies were carried out before the gas release in order to have reference values and to characterise the heterogeneity of the limestone massif around the injection room. Significant relative variations of resistivity were found in correlation with the CO 2 concentrations, which allowed not only to detect a leakage of CO 2 on free surfaces of the massif but also to follow the propagation of the CO 2 plume inside the limestone massif. The limestone resistivity decrease observed in this study is probably caused by CO 2 dissolution in the pore-water. The feasibility of this explanation was confirmed by laboratory measurements. Relative variations of resistivity and CO 2 concentrations were exponentially correlated.

The monitoring of CO2 storage sites is a paramount aspect for sites security and for the industrial deployment of the CCS technology. At the soil level, the monitoring of potential CO2 leakage will be requested, at least for high hazard areas (wells, faults). In this study, we compared the performance of a soil gas baseline survey with the disturbance in the gas composition and flux expected for a low amplitude diffuse leakage of CO2. A numerical study of a CO2 leakage was performed at the vadose scale by creating an underground CO2 source and observing its migration toward the atmosphere across a natural limestone formation. Only CO2 molecular diffusion in the gas phase and CO2 dissolution in the irreducible water were taken into account in this numerical model, following the description of a natural site on which field work was performed. A gas geochemistry baseline was performed in key locations and determined from the numerical predictions of the CO2 plume extension. In the light of the numerical experiment, we show how the different soil gas parameters measured are potentially useful for the detection of diffuse CO2 leaks at the soil level and we present the panel of different analyses and their respective addition to such studies.

The CO 2 -Vadose project aims at: (i) understanding the behaviour of CO 2 in the near surface carbonate environment during an induced CO 2 leakage, (ii) assessing numerical simulations associated with CO 2 release experiments, (iii) developing integrated field methodologies to detect and quantify a potential CO 2 leakage. A gas mixture of CO 2 with He and Kr was released in a cavity (9 m 3 , 7 m deep) located in an abandoned limestone quarry in France. Different gas measurement techniques were used to follow the plumes diffuse migrations in the carbonate vadose zone. A first gas release experiment with Ar and He was performed for checking and validating the experimental protocol. Then, the experimental CO 2 and tracers induced leakage was performed to study the gas migration in the vadose zone. The numerical simulations done with COORES™ code, associated with the experiment to describe the plumes extensions, were in good agreement near the source. The results show that CO 2 subsurface leakage can be anticipated thanks to inert gases used as tracers, like He and Kr. As part of a monitoring plan, the detection of noble gas increase could lead to the surveillance of the monitored area with accuracy.

The CO 2 -Vadose Project aims at developing a facility around a cavity in a former underground quarry to perform experimental releases of a CO 2 leakage under controlled conditions in order to study its migration along the carbonate vadose zone and to test geochemical and geophysical detection techniques. The paper aims to understand the natural CO 2 dynamics in the vadose zone and to establish a natural baseline which differentiates it from an induced CO 2 leakage. The location of the sensors is made on the basis of preliminary numerical modelling. The biological production of CO 2 is variable in time and space. There are a lot of environmental parameters responsible for changes in CO 2 concentrations to measure for understanding the natural CO 2 dynamics. The CO 2 moves from the soil to the atmosphere primarily by diffusion through air-filled pores. The air–water filled porosity of the soil can have a significant effect on the CO 2 movement in the soil. The CO 2 moves from the soil to the depth by diffusion through air-filled pores and piston effect. This study shows that it should be possible to detect a leakage with a greater sensitivity by installing the CO 2 probes at a depth greater than 2 m, where the biogenic CO 2 production is reduced.

Carbonate turbidite systems are not as well studied as their siliciclastic counterparts, resulting in a lack of knowledge on their vertical and lateral organisation. Thus, a preliminary detailed sedimentological study was undertaken in the upper Cretaceous limestones of Albania, which have been described as brecciated limestones and, more recently, as calciturbidites. The sedimentological study of three outcrops (Piluri, Vanister and Muzina) allows the definition of different lithologies grading from fine- to coarse-grained sequences representing the calciturbidites, intercalated with debris flow deposits and thick slumped levels. The thin-section examination of several facies defined in the field shows a dominance of mud-rich microfacies with variable granulometry, texture (mainly wackestone to packstone and floatstone), and the mixing of bioclastic and lithoclastic grains from both shallow-water (intertidal/infratidal) and deep-water settings (slope/basin). The microfacies description and fauna determination support the gravity origin of these calciclastic limestones. According to previous studies of the Ionian Basin and the surrounding platforms, the upper Cretaceous calciturbidite system could be reasonably linked to regional tectonic instabilities in relation to the beginning of the convergence between the Africa and Eurasian plates. The lateral and vertical organisation of these carbonate gravity deposits favours a depositional model over the apron model and that these deposits were fed by material derived from either the Apulian or the Kruja platform, through faulted shelf breaks.

This article investigates the isotope Radon-222 (hereafter referred to as radon) evolution in an underground quarry atmosphere, during three hydrological cycles (January 2002 to December 2004). The unsaturated zone has a complex chemical and dynamic operation which varies in time and space. The aim is to use radon as a natural tracer of water–air dynamics. Several parameters have been measured: the outside and inside temperature, the volumetric water content of porous rock, and the radon concentration. A simple diffusion model can explain the natural radon signal. The diffusion coefficient is a very weighty parameter in the calculated predictive signal of radon. Nevertheless, radon migration is more complex than the sole diffusion in the unsaturated zone. Three dynamic processes are at work during the hydrologic cycles: (i) a piston effect and water degassing, (ii) a diffusion process and (iii) a ventilation process. Several periods in the radon time series are individualized by the expression of one of these major processes.

From Danian to Thanetian, the South-Pyrenean carbonate platform underwent the most important Paleocene marine level fall of approximately 60 m magnitude. The palaeoenvironmental setting related to the highstand systems tract was defined thanks to detailed petrographical descriptions of the sedimentary facies. These conditions are based on a “hypersaline lagoon and prograding subtidal sabhka” model. The descriptions of diagenetical processes show that the lowstand period is underlined by the following six major diagenetic stages: early processes related to depositional environment, meteoric karstification, meteoric cementation, mixed corrosion and precipitation, and burial. We propose this sequence such as the diagenetic signature of the Mid-Paleocene subaerial exposure.

The Paleocene of the Campo section, Spain has different sedimentological characteristics above and below the Mid-Paleocene Unconformity. Beneath the unconformity sediments are dominated by evaporitic carbonates and collapse breccias. Above it they are characterized by continental detrital beds alternating with paleosols. Different subaerial features are observed and correspond to different porosity values, pore–throat sizes and micrite morphologies. Unexposed or intertidal facies have low porosity, low throat–pore size (mesoporosity) and well preserved rhombic crystals. Intermediate exposed facies (paleosols) possess medium porosity, medium pore–throat size (microporosity) and mainly micro-rhombic crystals. Finally, the facies corresponding to high exposure intensity and to evaporitic original facies presents high porosity, permeability, large pore–throat size and rounded micritic crystals. These observations show that the emersion phase caused important dissolution, especially when associated with an easily dissolved original lithofacies.

This article studies the water and heat transfer in the vadose zone of a carbonate formation during three hydrological cycles (August 2001–May 2004). The application of the time domain reflectometry (TDR) method to determine the volumetric water content of porous rocks has been widely investigated. The study of more than 285 monthly point measurements of the rock water content during three hydrological cycles, distributed throughout an abandoned underground quarry in Gironde, France, shows a permanently undersaturated limestone (between 35% and 50%). Three periods of maximum volumetric water content correspond to the occurrence of three effective rainfall events. The phase lag and amplitude damping of the hydraulic and thermal signals with depth can be modelled and explained by the hydraulic and thermal properties of the porous medium in the unsaturated zone.

A shallow CO 2 injection experiment was performed on a pilot site near Bordeaux, France, in February 2015. A gas mixture composed of approximatively 90% CO 2 and 5% of each He and Kr as gas tracers was injected through a vertical well, with low injection rate, at 1.80 m depth and into the carbonate vadose zone. A set of geochemical monitoring tools was installed in order to monitor the developing gas plume and to allow comparison between this experiment and a former release experiment which used a higher flow injection was made. Measurement showed a heterogeneous spatial and temporal variation of the gas plume. Difference in time arrival of peak concentration of He, Kr and CO 2 confirmed that diffusion alone did not occur in the porous media. Former studies mentioned advective flow drove through preferential paths. Both advection and diffusion flow may have been observed in the experiment. It also shows that the difference in molecular weights and the heterogeneity of the limestone could lead He to be used as a temporal tracer, and Kr as a spatial tracer as it allows us to estimate the extent of CO 2 plume. The ratios between the various gas components also indicate that a sizeable amount of CO 2 could be consumed before it reaches the subsurface, meaning that the vadose zone could be a buffering zone to CO 2 leakage. The comparison between this experiment and a former one with different injection condition revealed that the presence of advection is dependent of the heterogeneity of the limestone. However, the injection rate induces the amount of gas diffusing or/and advecting. Observations from both, our recent and a previous leakage experiment and future laboratory experiment could improve our understandings of the buffering zone and help to foresee CO 2 leakage for future storage site.

Sedimentological investigations have revealed ten facies in Upper Cretaceous platform carbonates (1220 m thick) at Llogara Pass in southern Albania that can be grouped into four facies associations. These reflect specific environmental conditions, ranging from intertidal to subtidal. The facies form small-scale patterns attesting to high-frequency/low-amplitude cyclicity characteristic of relative sea-level fluctuations. Meter-scale cycles have been classified into six distinct types and characterized on the basis of diagnostic surfaces, diagenetic features, and reservoir properties. A closer look at diagenetic and petrophysical features revealed a drastic porosity reduction at each cycle top (i.e., cycle boundary). This underlines a strong interconnection of facies types and reservoir properties at the cycle scale, thus impacting the whole carbonate succession. The cycle stacking pattern is a reflection of the sedimentary evolution during the late Cretaceous in this southern part of the Apulian Platform. (1) Meter-scale peritidal cycles suggest that the Cenomanian was characterized by stable shallow-water conditions. (2) Thick stromatolitic-dominated cycles typify Turonian deposits. Although the nature of the deposits indicates inner platform conditions, the long-term hiatus documented from Italy (Turonian bauxites) is not evidenced in Llogara. (3) The thin (a few tens of meters) Coniacian–Santonian interval suggests the onset of a significant tectonic control over the sedimentary dynamics, likely accompanied by morphological changes on the Apulian Platform and an emergence of rudist-dominated cycles. (4) Peritidal-subtidal cycles persist during the Campanian, accompanied by a broad development of rudist organisms that evidence significant and repeated relative sea-level rise. These data allow refinement of the general sedimentological evolution during the late Cretaceous on the Apulian Platform.

International audience; The DEMO-CO2 project is dedicated to develop an analytical method for CO2 leakage detection within the vadose zone and to understand the behavior of CO2 in the near subsurface carbonate environment during an induced CO2 leakage. A gas mixture of 3 m3 of CO2, He and Kr was released at 3.7 m depth in a borehole located in a carbonate vadose zone. Different detection techniques were used to follow the CO2, and noble gas migration within the vadose zone. A numerical simulation done with COORES™ code was used to predict gas flux at surface. Measurements performed in the field showed heterogeneous gas transfer in the subsurface as a result of contrast of permeability/porosity of the porous media at meter scale. Both advective and diffusive gas transfer could be observed due to the different time frames needed to reach maximum He, Kr and CO2 concentrations, confirming that noble gases can be used as precursor of injected CO2 leakage in case of diffusive transfer prevails. Despite the subsurface heterogeneity, simulations results of CO2 flux at the surface were in relatively good agreement with field measurements. The comparison of CO2 concentration with measurements of ubiquitous gas such as N2, coupled with isotopic 13C analyses could be used to clearly differentiate injected CO2 from natural background CO2 produced by biological activity. Lessons learned through this experiment could help to improve future near-surface gas geochemistry surveys for site assessment, identify CO2 leakage, and leakage monitoring at active carbon capture and storage sites.

This chapter discusses the theoretical principles of the complex resistivity, the electrical behavior of a saturated and unsaturated porous medium, and electrofiltration phenomena. The chapter provides the physical properties of different samples. The experimental setting and the conclusions are also presented in the chapter. More than thirteen carbonate samples were investigated to measure classic electric parameters in saturated and unsaturated geological carbonate porous systems. The values of the cementation factor m range from 1.55 to 2.49. The dolomitic crystal texture shows the highest value. The electrical behavior of the carbonate porous system in an unsaturated medium is investigated from the saturation exponent n . The highest values of n are obtained for a dolomite crystal carbonate while the lowest values of n are obtained for a mudstone-wackestone texture. The values of the chargeability factor M range between 0.19 and 0.5, and they depend on the brine/gas saturation of the carbonate porous system, carbonate textures, and the salinity of brine in a porous medium.

In terrestrial environments, fungi constitute one of the most important microbial agents, but also due to their ability to decay organic matter but also because of their role in various biogeochemical cycles (Gadd, 1999; Verrecchia, 2000). Fungal involvement in carbonate rock destruction, dissolution and precipitation has been suspected for over 150 years (Braconnot, 1825) but convincing hypotheses to explain the processes of carbonate dissolution and precipitation were not proposed before the W’s. Nevertheless, their role in the calcium carbonate cycle remains largely underestimated. The aim of this chapter is to emphasize the great potential of fungi in CaCO3 redistribution and sequestration at the surface of continents.

This paper reports an investigation of the effects of porous solid structures on their electrical behaviour at different frequencies (from 100 Hz to 100 kHz). For that, we study different parameters such as : formation resistivity factor, cementation factor, chargeability, resistivity index and saturation exponent. Different porous solid structures are quantified from the petrographic image analysis and Hg-injection technique. Then, by using different models we obtain the permeability prediction from the electrical behaviour and structure parameters.

International audience

The sedimentology and tectonics and their relationship of the Paleozoic series that fill the Ghadames basin and its northern extension consisting of the Jefarah basin in Libya and Tunisia was studied. These formations belong to the Gondwana cycle and are typically interpreted as being deposited in a cratonic basin truncated by the Hercynian unconformity. This study is based on wells. The stratigraphic correlation between the wells is based on the definition of second order cycles. This allowed to produce isopach maps of facies distributions and to reconstruct the paleogeography of the different stratigraphic units. These data allow to address the nature of the deformation and also clarifies the behavior of active high regional areas during the Palaeozoic. The Paleozoic succession in the Ghadames and Jefarah basins can be divided in to five first order sequences, bounded by major tectonic unconformities with sequence duration of 40 - 70 Ma. Within these five sequences eighteen second order sequences (10 - 40 Ma) were differentiated, describing Sequence Boundaries (SB), Maximum Flooding Surfaces (MFS) and sedimentological characteristics. Twenty six wells with its geological well reports and well logs have been used in the study area, i.e. the Ghadames and Jefarah basins (Libya) illustrate how reservoir properties changes laterally and vertically through time (from a proximal to a distal sitting). Two softwares were used, JLog (version 4) petrophysical software for reservoir property analysis and PETREL (Schlumberger software 2014 version) for constructing stratigraphic correlation models. The Paleozoic reservoirs in the study area are spread over a large range of siliciclastic reservoirs with the prospective section extending from Cambrian to Permian. Hydrocarbons within the Ghadames and Jefarah basins originated from two major source rocks: i.e. the Lower Silurian Tanezoft Formation and Middle-Upper Devonian Aouinat Ounine Formation. The nine main Paleozoic reservoirs are respectively the Hassaouna, Haouaz and Memouniat Formations (Lower Paleozoic), Acacus, Tadrart, Ouan Kaza and Tahara Formations (Middle Paleozoic) and M’rar and Asadjefar Formations (Upper Paleozoic). Six stratigraphic cross sections through the area have been reconstructed to illustrate the vertical and lateral reservoir extensions. The dataset demonstrates that the Paleozoic reservoir properties are influenced by both, depositional facies and position within the paleogeographical setting (from proximal to distal part).; L’analyse stratigraphique et tectono-sédimentaire des séries sédimentaires du Paléozoïque qui remplissent le bassin de Ghadamès et son extension au nord, le bassin de Jefarah en Libye et en Tunisie, ont été étudiées. Ces formations appartiennent au cycle de Gondwana et sont, généralement, interprétées comme étant déposées dans un bassin cratonique tronqué par la discordance hercynienne. Cette étude est basée sur l’analyse des électrofaciès et des électroséquences dans plus de 130 puits. Les corrélations stratigraphiques entre puits sont basées sur la définition des cycles de 1er et de 2ème ordre. Cela a permis de comprendre l’évolution des environnements sédimentaires dans les deux bassins, de reconstituer des cartes isopaques de répartition des faciès et de reconstruire la paléogéographie des différentes unités stratigraphiques. Ces données permettent d'aborder la nature de la déformation et clarifient également le comportement des zones actives régionales élevées durant le Paléozoïque. La succession paléozoïque dans les bassins de Ghadamès et de Jefarah peut être divisée en cinq séquences de 1er ordre, délimitées par des discontinuités tectoniques majeurs avec une durée de séquence de 40 à 70 Ma. Dans ces cinq séquences, dix-huit séquences de 2ème ordre (10 à 40 Ma) ont été différenciées, décrivant les limites de séquence (SB), les surfaces d'inondation maximales (MFS) et les caractéristiques sédimentologiques. Vingt-huit puits ont été analysés afin d’identifier et d’évaluer les systèmes réservoirs paléozoïques dans les bassins Ghadamès et de Jefarah illustrant comment les propriétés réservoirs changent latéralement et verticalement dans le temps en fonction des environnements de dépôt. Deux logiciels ont été utilisés, le logiciel pétrophysique JLog pour l'analyse des propriétés réservoirs et PETREL pour la construction de modèles de corrélation stratigraphique. Les réservoirs dans la zone d'étude sont répartis sur une large gamme de réservoirs silicoclastiques s'étendant du Cambrien au Permien. Les hydrocarbures dans les bassins de Ghadamès et de Jefarah proviennent de deux roches mères principales, à savoir la Formation de Tanezuft du Silurien inférieure et la Formation d'Awaynat Wanin du Dévonien moyen-supérieur. Les neuf principaux réservoirs paléozoïques sont respectivement les formations de Hasawnah, de Hawaz et de Mamouniyat (Paléozoïque inférieure), d’Akakus, de Tadrart, d’Ouan Kaza et de Tahara (Paléozoïque moyen) et les Formations de M'rar et d’Asadjefar (Paléozoïque supérieur). Six sections transversales stratigraphiques dans la région ont été reconstruites pour illustrer les extensions verticales et latérales des réservoirs. L'ensemble de données acquises démontre que les propriétés réservoirs des séries paléozoïques sont influencées par les deux, les faciès et les environnements de dépôts.