Hard Shale Research Articles

Properties and Model of a Lacustrine Shale Oil Reservoir: A Case Study of the Upper Fourth Member and Lower Third Member of the Shahejie Formation in Dongying Sag and Zhanhua Sag, Jiyang Depression

By combining thermal simulation experiments with core data, thin sections, scanning electron microscopy (SEM), source rock, and high-pressure mercury and gas adsorption analysis, this paper evaluates the properties and models of shale reservoirs in the upper fourth member and the lower third member of the Shahejie Formation in Dongying Sag and Zhanhua Sag. The results show that the oil shale is a high-quality source rock with petroleum generation potential. Inorganic mineral pores, organic pores, and fractures have developed with petroleum storage capacity. Clay and organic-rich soft shale lithofacies are interbedded with carbonate-rich hard shale lithofacies to form sandwich-type source–reservoir–caprock assemblages with internal sealing properties. Bitumen occurs mostly in the free state, and to a lesser extent is adsorbed, and shows flow characteristics. The migration resistance of the bitumen is displacement pressure, including capillary force and adsorption resistance, and the main force is pore fluid pressure. The migration modes of the bitumen include both subcritical flow and instantaneous flow, which are controlled by pore fluid pressure, displacement pressure, and the rock’s fracture strength. Owing to the multi-scale characteristics of the shale reservoir space, a vein-type model of a multi-scale progressive transport network is developed that obeys Murray’s law with a dominant migration pathway in the shale reservoir. The shale oil reservoir is a special lithologic reservoir controlled by the sedimentary environment and has self-generation, self-storage, and self-sealing characteristics with developed pore fluid overpressure and a multi-scale transport network.

Assessment of Chemical Effects on Wellbore Stability in Transition Shale Formation

Substantial research has been conducted on the mechanisms responsible for the wellbore collapse in shale formations. For chemically active soft shale formations, pore pressure and stress change due to osmotic pressure and hydration swelling are usually recognized as the primary mechanisms, while for chemically inactive hard shale formation, wellbore instability is generally attributed to weak structural planes like bedding planes and microcracks. In this paper, experimental testing and analytical and numerical analyses are performed to reveal the dominant mechanism of the frequently encountered severe wellbore instability events in the middle-deep shale formation in the Bohai oil field of China. It is evidenced from the physical and chemical experimental testing that the middle-deep shale features both medium chemical activity and abundant bedding planes and microcracks, indicating that the middle-deep shale is in the transition process from chemically actively soft shale to the chemically inactive but laminated and fractured hard shale. Mechanical testing also shows considerable strength degradation of the middle-deep transition shale due to drilling fluid-shale interaction. Analysis through a hydro-chemo-mechanical coupling theory shows that the extent of the damage zone around the wellbore is limited if only pore pressure change and hydration swelling caused by the chemical difference between the drilling fluid and the formation fluid are considered, which cannot explain the severe wellbore collapse in the drilling process. In contrast, when pore pressure increase and strength degradation of the shale due to drilling fluid penetration along the bedding planes and microcracks are taken into account, a damage zone of 3~4 times of the wellbore diameter can be generated, implying that the dominant mechanism of the wellbore instability in the middle-deep transition shale formation should be the pore pressure change and strength degradation resulted from drilling fluid penetration along the bedding planes and microcracks.

Le Paléolithique supérieur dans l’île d’Hokkaïdo

Since the discovery of the first Paleolithic site in Hokkaido, we consider that the time in the half more than centuries already passed, and float today. However, our research is still a way. By today, we have not discovered the trace about a Pithecantropines (Homo erectus) and a Paleanthropic man (Homo sapiens neanderthalensis) at all in this region. We know that a Neanthropic man (Homo sapiens sapiens) dominated all the continents except Antarctica in the final time of the Pleistocene era. And they passed along the dried shoal which appeared to the north in the same time from the Asian Continent to the Island of Hokkaido, and reached it to this place. The first attainment time is an age which exceeds 20,000-years before a little from the present. We are not checking a fact which exceeds it you to be much. However, the habitants of these beginnings left the trace of the activity of them in large numbers, so that he was wonderful to inside of this island. The studies-of-prehistory research in Hokkaido has little proof of the natural science field concerned on age determination or chronology. This has serious restriction. However, the tephra-chronology of volcanic ashes has played the big role uniquely. The eruption of the Eniwa volcano of the Hokkaido central part is especially a very important index. This volcano blows off ash fall (En-a) in large quantities, and covered all large ranges. This deposited volcanic-ashes layer plays a big role to discernment of an old industry and a recent industry on the cultural chronology. The obsidian from this island and nearby hard shale was used for many industries of this Upper Paleolithic cultures as main materials. Although obsidians in the island where the different four outcrops are known well. This rock was mined in large quantities, and was carried in various places. As well as many examples in the world, we divided this rock, and the human beings of the prehistoric age were demanded for it, and it was often utilized. In it, especially the outcrop of Shirataki was located in the northern part of Hokkaido, and was very important. Large quantities of obsidian from Shirataki outcrop is discovered in a large number of Paleolithic sites within a segment 700km in diameter at least. It covered the territory in Hokkaido and circulated further also except this island. This fact circulated as important trade materials on stone-tool fabrication among the human-beings groups from whom this island's every place differed. In this time, human beings’ activity in Hokkaido is a clear proof, which was not isolated at all. As for the studies of the prehistorians of Hokkaido distinguish, the exception put the technical process of eight different microblade productions. The technical process of some of them was limited only to the specific narrow area. Or it is proved that other technical processes are widely connected with the human-beings group of the Asian Continent on the contrary. At present, our research grasps the whole second-half Paleolithic culture, and has not yet established the year system edited by locally complete. The oldest industry of this area composed the typical stone tool of second-half Paleolithic culture from the beginning, and was accompanied by the manufacturing technique of a braid and microblade. The feature is the example in which the ruins of Kashiwadai-I were most excellent. These ruins correspond at time older than deposition of the Eniwa volcano tephra. It is located at the chill time in the second half of a Würm glacial period. The second continuing step is an industry of succession newer than this volcano tephra. It is raised as an example with Ôsatsu-16 typical ruins etc. The third phase is an industry of the end term of second-half Paleolithic culture. It is simultaneously located in the dawn of Jōmon culture. The feature of this cultural aspect is a transitional cultural stage which earthenware appears and is called what is called “Sub-Neolithic-Culture”. We can check having passed expansively, while the aspect of this last continues within a short period of time relatively.

Study on Wellbore Stability and Failure Regions of Shale considering the Anisotropy of Wellbore Seepage

The hard and brittle shale formation is prone to collapse and instability, and the penetration of drilling fluid along the bedding reduces the mechanical properties of rock near the borehole wall, resulting in serious downhole accidents. Therefore, in this paper, the geomechanical parameters of the reservoir in the Longmaxi formation of Jiaoshiba were determined by field hydraulic fracturing and laboratory experiments. Then, the stress distribution model of borehole wall under the condition of underbalanced seepage flow is established based on the experimental results obtained by mechanical experiments on underground cores. The instability zone of borehole wall under the condition of underbalance is calculated and analyzed. The results show that the two-way horizontal ground stress of the Longmaxi formation is higher than 2.2 MPa/100 m, and the original ground stress is high. Moreover, the mechanical parameters of the stratified shale stratum matrix and weak surface are significantly different. The cohesion (4.7 MPa) and the angle of internal friction (26.9°) of bedding plane are significantly lower than that of the matrix (7.77 MPa) and the angle of internal friction (46.7°). Hard and brittle shale is easy to be destroyed along the stratification. Under the condition of underbalanced seepage, the mechanical properties of borehole shale can be stable. It is found that when the borehole axis is vertically stratified, the collapse pressure is the lowest, while in other drilling directions, the drilling fluid density needs to be increased by 0.5 g/cm3 to maintain the borehole stability. With the increase of the inclination angle of bedding plane, the wall failure area increases. The results of this study can provide guidance and suggestions for drilling in Jiaoshiba block and other permeable hard and brittle shale formations.

Rethinking the Disappearance of Microblade Technology in the Terminal Pleistocene of Hokkaido, Northern Japan: Looking at Archaeological and Palaeoenvironmental Evidence

Archaeological research, for several decades, has shown that various microblade technologies using obsidian and hard shale appeared and developed from the Last Glacial Maximum to the terminal Pleistocene (Bølling–Allerød–Younger Dryas) in Hokkaido, Northern Japan. It is well accepted that microblade technology was closely related to the high mobility of foragers to adapt to harsh environments. Recent archaeological and palaeoenvironmental evidence from Hokkaido demonstrates that the disappearance of microblade technology occurred during the terminal Pleistocene, influenced by a wide range of factors, including changes in landscape, climate, subsistence and human populations. The goal of this paper is to provide an overview of the current state of research on the process and background of the disappearance of microblade technology and to discuss prospects for future research. This paper will (1) review palaeoenvironmental research in Hokkaido on changes in climate and biological composition from the terminal Pleistocene to the initial Holocene; (2) survey changes in the technological adaptations and resource use of humans based on the archaeological evidence; and (3) discuss how the abrupt fluctuations of climate that occurred in the terminal Pleistocene affected human behaviour and demographics in Hokkaido.

Quantitative phase field modeling of hydraulic fracture branching in heterogeneous formation under anisotropic in-situ stress

Unconventional reservoir hydraulic fracturing is often characterized with diverting and branching. A fundamental understanding of the fracture branching mechanism remains elusive due to the complicated fusion of geo stress, formation heterogeneity and pre-existed complex natural fracture topologies. Existing sharp fracture models such as, finite-element method (FEM) and its modified versions, often suffer in complex fracture topologies owing to the computationally expensive remeshing when fracture diverts and/or branches. In this paper, phase-field modeling (PFM) is proposed to quantitatively investigate the hydraulic fracture branching condition in heterogeneous formation under anisotropic in-situ stress. The PFM is featured with the diffusive interface, enabling it to automatically capture the fracture branching and diverting without the need of tracking the fracture interface. The model is first verified in predicting the fracture width, stress distribution and fracture propagation via benchmark examples, followed by the comprehensive investigation on hydraulic fracture branching in a heterogeneous formation where a rock strip is laid across the shale main formation with anisotropic in-situ stress. Parametric study shows no branching occurs when the hydraulic fracture propagates towards soft strip (e.g. soft shale), while fracture branches when it propagates towards stiff strip (e.g. hard shale or sandstone) as long as the Young's modulus ratio (ER = Estrip/Emain) exceeds a critical value. Such a critical value increases as the principal in-situ stress difference (Sd) goes up. Finally, the hydraulic fracture branching is quantified in terms of the deviation distance and reentry angle, both of which are found to rise as the ER increases, and as Sd decreases, which indicates relatively low Sd and high ER are in favor of increasing the fracture complexity and drainage area. These results could provide valuable insights in predicating and creating complex reservoir hydraulic fracturing patterns.

Estimation of Shale Intrinsic Permeability with Process-Based Pore Network Modeling Approach

A multi-scale pore network model is developed for shale with the process-based method (PBM). The pore network comprises three types of sub-networks: the $$\upmu $$ m-scale sub-network, the nm-scale pore sub-network in organic matter (OM) particles and the nm-scale pore sub-network in clay aggregates. Process-based simulations mimic shale-forming geological processes and generate a $$\upmu $$ m-scale sub-network which connects interparticle pores, OM particles and clay aggregates. The nm-scale pore sub-networks in OM and clay are extracted from monodisperse sphere packing. Nm-scale throats in OM and clay are simplified to be cylindrical and cuboid-shaped, respectively. The nm-scale pore sub-networks are inserted into selected OM particles and clay aggregates in the $$\upmu $$ m-scale sub-network to form an integrated multi-scale pore network. No-slip permeability is evaluated on multi-scale pore networks. Permeability calculations verify that shales permeability keeps decreasing when nm-scale pores and throats replace $$\upmu $$ m-scale pores. Soft shales may have higher porosity but similar range of permeability with hard shales. Small compaction leads to higher permeability when nm-scale pores dominate a pore network. Nm-scale pore networks with higher interconnectivity contribute to higher permeability. Under constant shale porosity, the shale matrix with cuboid-shaped nm-scale throats has lower no-slip permeability than that with cylindrical throats. Different from previous reconstruction processes, the new reconstruction process first considers the porous OM and clay distribution with PBM. The influence of geological processes on the multi-scale pore networks is also first analyzed for shale. Moreover, this study considers the effect of OM porosities and different pore morphologies in OM and clay on shale permeability.

O-5 重力性曲げによる木古内層(硬質頁岩)の斜面変動

O-5 重力性曲げによる木古内層(硬質頁岩)の斜面変動

Numerical modeling of the tensile fracture reactivation under the effects of rock geomechanical properties and heterogeneity during CO2 storage

The injection of CO2 into aquifers increases fluid pressure and induces a change of the geomechanical state. This is expected to be a cause of fracture reactivation, which is an important issue for the safety of CO2 storage. Using the geomechanics module, fracture reactivation, which was induced by tensile failure, was considered for the investigation of a potential CO2 leakage. Numerical simulations were conducted to analyze the effects of the rock geomechanical properties on the fracture reactivation in a two-dimensional system, and then the properties of fracture propagation were extended to the different rock types, hard shale and weak shale, in a three-dimensional system. Changes of the stress state, rock deformation, and the pressure build-up induced by CO2 injection were examined. When a rock has a high Young’s modulus, effective stress decreases rapidly, leading to an earlier fracture reactivation. The total reduction of effective stress in the rock with a low Poisson’s ratio was less than that of the rock with a high Poisson’s ratio. The magnitude of pressure build-up is lower in the high-permeability rock, so that the fracture propagates more slowly. Hard shale’s caprock is more favorable than that of weak shale for CO2 storage because fractures are opened later, retarding the CO2 leakage. The injected CO2 flows through a preferable region with reactivated fractures in the heterogeneous caprock. This study broadens our perception of the mechanical behavior that is induced by CO2 injection and it could be helpful for the precise safety assessment of CO2 storage projects.

Error estimates of elastic components in stress-dependent VTI media

Abstract This work examines the ranges of physically acceptable elastic components for a vertical transversely isotropic (VTI) laboratory shale data set. A stochastic rock-physics approach combined with physically based acceptance and rejection criteria determined the ranges. The importance of this work is to demonstrate that multiple constrained models explain independently calculated measurement error bars. The data set consisted of pressure- and directional-dependent velocity measurements conducted on a low porosity, brine-saturated hard shale. Error bars were calculated for all five elastic stiffnesses and compliances as a function of pressure. The rock physics model is pressure dependent and represents simultaneously five elastic compliances for a VTI medium. A non-linear least squares fitting routine established a best-fit model to the five compliances at all pressures. Perturbations of the best-fit model provided the statistical parameter space. Twelve physical constraints or data-set-specific conditions comprised the acceptance/rejection criteria. These constraints and conditions included strain-energy requirements, inequalities among stiffnesses and anisotropy parameters, and rates of change of moduli with pressure. The largest number of rejected models resulted from violating a criterion relating a compressional and shear stiffness. Minimum misfits between the accepted models and the data illustrate that a fraction of the accepted models best explain the data. The misfits between these accepted models and data explain the error in the data and/or inhomogeneities at the measurement scale. The ranges of acceptable elastic component values and the corresponding uncertainty estimates could be incorporated into seismic-inversion, imaging, and velocity-modeling schemes.

グリーンタフ地域の硬質頁岩卓越層を基岩とする流れ盤型地すべりの地質的特徴

地すべり多発地帯のグリーンタフ地域における新第三系中部～上部中新統遠音別川層硬質頁岩卓越層を基岩とする古期大規模地すべり (オシンコシン地すべり) 地域の地すべりは, 基岩地質による地すべり分類では, 熱水変質帯地すべりである。この地域の地すべりは, 流れ盤型であり, 移動体構成物質による地すべり分類では, オシンコシン地すべりのような大規模熱水変質岩地すべり, 2006年町道オシンコシン線地すべりのような中規模岩屑・土砂地すべり, 1999年町道オシンコシン線地すべりのような小規模岩屑・土砂地すべりなどが見られる。この型の地すべりの発生は硬岩の硬質頁岩厚層中の多量のスメクタイトを含む軟岩の軟質凝灰岩薄層と密接な関係を持つ。

続成帯硬質頁岩を基岩とする受け盤型地すべりにおける風化帯の重要性

続成帯硬質頁岩を基岩とする受け盤型地すべりにおける風化帯の重要性

Nonmodified Silica Nanoparticles Decrease Water Invasion Into Atoka Shale

This article, written by Editorial Manager Adam Wilson, contains highlights of paper SPE 146979, ’Decreasing Water Invasion Into Atoka Shale Using Nonmodified Silica Nanoparticles,’ by J. Cai, SPE, China University of Geosciences; M.E. Chenevert, SPE, and M.M. Sharma, SPE, The University of Texas at Austin; and Jim Friedheim, SPE, M-I Swaco, prepared for the 2011 SPE Annual Technical Conference and Exhibition, Denver, 30 October-2 November. The complete paper was published in the March 2012 issue of SPE Drilling & Completion, Pages 103-112. Shales account for 75% of the all footage drilled and are responsible for 90% of wellbore-stability problems. Maintaining wellbore stability is one of the more critical aspects of oil and gas drilling. The main cause of shale instability for both soft and hard shales is water absorption and subsequent swelling and sloughing of the wellbore. Laboratory data shows the positive effect of adding commercially available, inexpensive, nonmodified silica nanoparticles (particle size varies from 5 to 22 nm) to water-based drilling muds and their effect on water invasion into shale. Experimental Methods Materials Used . Nanoparticles. A total of 22 different types of nanoparticles were obtained from four manufacturers. Of these samples, only seven—NP-G, NP-D, NP-A, NP-E, NP-B, NP-C, and NP-F—were nonmodified, nonacidic, and commercially available (Table 1). Shale Properties. Shale is a sedimentary rock that mineralogically consists of clays, quartz, and other silicate and carbonate minerals. Because of their high clay content, shales tend to absorb water from a water-based mud, which results in swelling and sloughing of the wellbore. In this study, a hard and preserved Atoka shale was used. Great care was taken to preserve the shale at its native water activity. The shale was not exposed to air for any period of time over a couple of minutes. It was stored in oil, and, during preparations for testing, it was stored in a controlled-humidity desiccator. Use of shales that have dried out or that are reconstituted is not acceptable for the tests that were run in this study. Muds Used. Three types of water-based muds were used in this study: a freshwater mud (FWM), a thick bentonite mud, and a low-solids mud (LSM). It was found that, in all tests, the presence of 10 wt% concentration of nanoparticles reduced the permeability of the shale. Test Equipment for Measuring Shale Permeability. A pressure penetration (PP) test was used to measure shale permeability. The test consisted of three steps. Seawater was first flowed through the shale sample, followed by a base mud, and then by a base mud that contained 10 wt% nanoparticles. The experimental setup (Fig. 1) consisted of several devices used to achieve a continuous flow of the test fluid across the top face of the shale sample while the simulated pore fluid was kept in contact with the lower face of the shale. The simulated pore fluid was a 4 wt% solution of sea salt that had a 0.98 water activity. A test fluid was flowed across the top of a shale sample (Fig. 2) at a constant pressure (approximately 250 psi), and the buildup of fluid pressure in a small sealed chamber located at the bottom of the shale was recorded.

Scenes from the Past: Initial Investigation of Early Jurassic Vertebrate Fossils with Multidetector CT

The study of fossils permits the reconstruction of past life on our planet and enhances our understanding of evolutionary processes. However, many fossils are difficult to recognize, being encased in a lithified matrix whose tedious removal is required before examination is possible. The authors describe the use of multidetector computed tomography (CT) in locating, identifying, and examining fossil remains of crocodilians (Mesosuchia) embedded in hard shale, all without removing the matrix. In addition, they describe how three-dimensional (3D) reformatted CT images provided details that were helpful for extraction and preparation. Multidetector CT can help experienced paleontologists localize and characterize fossils in the matrix of a promising rock specimen in a nondestructive manner. Moreover, with its capacity to generate highly accurate 3D images, multidetector CT can help determine whether the fossils warrant extraction and can assist in planning the extraction process. Thus, multidetector CT may well become an invaluable tool in the field of paleoradiology.

Influence of Specimen Geometry on Sample Disturbance Observed in Oedometric Testing of Clay Shales

Abstract There has been a significant amount of research investigating the relationship between sample disturbance and laboratory test results in soft soils. As a result of this research, the general rule adopted is that using larger specimens results in less sample disturbance. When testing these larger specimens in the laboratory, the results are more representative of in situ behavior of the materials. In contrast, there has been relatively little corresponding research performed on hard soils whose behavior typically lies on the boundary between rock and soil. Extensive unloading in hard soils, from sampling, results in large suctions (negative pore pressures) and the formation of fractures that are uncharacteristic of the material in its natural state. This poses the question of whether the use of small specimens would produce more reliable laboratory results. This paper investigates the following two hypotheses within the context of oedometric testing: (1) testing smaller diameter specimens will produce results more representative of the in situ behavior of the material, and (2) an aspect ratio of 2.5 may reduce disturbance to the specimen during preparation are tested. The results of this testing program, including the intact material properties, and a characterization of the compression behaviour of clay shale from the Bearpaw Formation is also presented herein. Results show that a reduced specimen size, when working with a hard clay shale, minimizes the effect of disturbance and produces results that are the most representative of the intact material. Decreased specimen size also aids in determining preconsolidation pressure by not only reducing the disturbance to the sample resulting from unloading, but also by enabling these high stresses to be achieved in conventional testing equipment. Two criteria from the literature were used to assess disturbance within the oedometer specimens. Overall, the methods provide a good baseline of assessing disturbance, however, there is less gradation to the quality of a specimen in a hard soil. Parameters Cc and σ′p were sensitive to sample disturbance, however, other parameters such as cv and K were less dramatically affected by disturbance. Therefore, care must be taken when assessing the compression of a hard soil as failing to achieve sufficiently higher stresses and the presence of disturbed specimens may lead to misleading Cc and σ′p values.

Use of an Accelerated Migration Test to Study Alteration of Backfill in Contact with Concrete

Zhishin clay and Black Hill bentonite are used as raw clay materials in this study. These clays are mixed with Taitung area hard shale to produce the backfill material for potential application as barrier for the disposal of low-level radioactive waste. The interaction between concrete barrier and the backfill materials is simulated by an accelerated migration test to investigate the effect of concrete on the expected functions of backfill material. The results show some decrease in swelling potential in the backfill material near the interface. Also, backfill material close to the contact with concrete exhibits greater change in the ratio of calcium/sodium concentration, due to the release of calcium ions from the concrete material.

Experimental Study on Heat Alteration of Palaeolithic Material: Preliminary Results from Shale in the Northeastern Region of Japan

In order to obtain a better understanding of the intentional thermal alteration of Palaeolithic materials in the northeastern region of Japan, heating experiments were carried out on two types of shale samples. Mechanical properties such as strength and hardness as well as surface morphology were analyzed before and after heating. As a result, a functional change was observed in mechanical factors after heating. A hard shale sample comprising small grains exhibited a significant decrease in strength and noticeable increase in hardness after heating. On the other hand, shale comprising larger crystal grains exhibited an increase in both strength and hardness values. Moreover, smoother surfaces were observed through SEM analysis in both samples after heating. These results lead us to the conclusion that the heating process, especially in the case of harder shale with higher strength values, might have modified material properties such as flaking characteristics as well as functional attributes that are relevant to hardness.

Possibly contaminated amino acids in the hard shale of the Miocene Kusanagi Formation

Possibly contaminated amino acids in the hard shale of the Miocene Kusanagi Formation

Molecular characterization of microbial communities in fault‐bordered aquifers in the Miocene formation of northernmost Japan

ABSTRACTWe investigated the diversity and distribution of archaeal and bacterial 16S rRNA gene sequences in deep aquifers of mid‐ to late Miocene hard shale located in the northernmost region of the Japanese archipelago. A major fault in the north‐west–south‐east (NW–SE) direction runs across the studied area. We collected three groundwater samples from boreholes on the south‐west (SW) side of the fault at depths of 296, 374 and 625 m below ground level (m.b.g.l.) and one sample from the north‐east (NE) side of the fault at a depth of 458 m.b.g.l. The groundwater samples were observed to be neutral and weakly saline. The total microbial counts after staining with acridine orange were in the order 105−106 cells mL−1 and 103 cells mL−1 in the aquifers to the SW and to the NE of the fault, respectively. A total of 407 archaeal and bacterial 16S rRNA gene sequences (204 and 203 sequences, respectively) were determined for clone libraries constructed from all groundwater samples. Phylogenetic analyses showed that the libraries constructed from the SW aquifers were generally coherent but considerably different from those constructed from the NE aquifer. All of the archaeal clone libraries from the SW aquifers were predominated by a single sequence closely related to the archaeon Methanoculleus chikugoensis, and the corresponding bacterial libraries were mostly predominated by the sequences related to Bacteroidetes, Firmicutes and δ‐Proteobacteria. In contrast, the libraries from the NE aquifer were dominated by uncultured environmental archaeal clones with no methanogen sequences and by β‐proteobacterial clones with no sequences related to Bacteroidetes and δ‐Proteobacteria. Hence, the possible coexistence of methanogens and sulphate reducers in Horonobe deep borehole (HDB) on the SW side is suggested, particularly in HDB‐6 (374 m.b.g.l.). Moreover, these organisms might play an important geochemical role in the groundwater obtained from the aquifers.

Alteration of the Callovo–Oxfordian clay from Meuse-Haute Marne underground laboratory (France) by alkaline solution. I. A XRD and CEC study

The reaction of the clay fraction of the Callovo–Oxfordian hard shale formation hosting the French underground laboratory site, with high pH NaOH, KOH and Ca(OH) 2 solutions has been investigated through closed system experiments at 60, 90 and 120 °C over 6, 24 and 168 h. The mineralogical composition of the run samples has been determined using X-ray diffraction (XRD) of randomly oriented powders showing the formation of different species of zeolites (analcime, chabazite, phillipsite) and Ca silicates (tobermorite, katoite). The phyllosilicates were studied using XRD of oriented preparations and cation exchange capacity measurements. Detrital or diagenetic mica and chlorite in the <2 μm fraction remain unchanged. On the contrary, the smectite and random illite–smectite mixed layer minerals are strongly reactive. The expandable layers of montmorillonite type are selectively dissolved while beidellitic ones survive or are transitionally formed.