China organic-rich shale geologic features and special shale gas production issues

The depositional environment of organic-rich shale and the related tectonic evolution in China are rather different from those in North America. In China, organic-rich shale is not only deposited in marine environment, but also in non-marine environment: marine-continental transitional environment and lacustrine environment. Through analyzing large amount of outcrops and well cores, the geologic features of organic-rich shale, including mineral composition, organic matter richness and type, and lithology stratigraphy, were analyzed, indicating very special characteristics. Meanwhile, the more complex and active tectonic movements in China lead to strong deformation and erosion of organic-rich shale, well-development of fractures and faults, and higher thermal maturity and serious heterogeneity. Co-existence of shale gas, tight sand gas, and coal bed methane (CBM) proposes a new topic: whether it is possible to co-produce these gases to reduce cost. Based on the geologic features, the primary production issues of shale gas in China were discussed with suggestions

Ethylene glycol monoethyl ether (EGME) adsorption by organic matter (OM)-clay complexes: Dependence on the OM Type

The ethylene glycol monoethyl ether (EGME) adsorption method has been used as an available technique for measuring the total specific surface area (TSSA) of soils and clay-rich rocks. However, the existence of organic matters (OM) has recently been proposed to affect the accurate measurement of the TSSA. To explore the effects of OM on the TSSA evaluation of clay-rich samples, EGME adsorption experiments were performed on OM and the OM-clay minerals (OM-clay) complexes that widely exist in soil and clay-rich rocks. Two types of OM, 12-aminolauric acid (ALA) and lauric acid (LA) were used, and montmorillonite (Mt) was selected as the representative clay mineral. OM-clay complexes with OM in interlayer space or OM-clay mixture with OM on the external surface of an expanding clay mineral were prepared to investigate the influence of occurrence sites of OM on the EGME adsorption. The combined methods of X-ray diffraction (XRD) and diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) were used to study the structural characteristics of the OM-clay complexes before and after EGME adsorption for revealing the EGME adsorption mechanisms. The results showed both the occurrence sites and the functional groups of OM significantly influence the EGME adsorption behaviour and TSSA for OM-clay complexes. As ALA intercalated into interlayer space of Mt, it can occupy parts of adsorption sites of EGME leading to a lower TSSA than that of Mt. While as LA located on the external surface of Mt, it affects access to the interlayer surface by the EGME and occupies parts of EGME adsorption sites of the external surface of Mt, resulting in lower adsorption capability and the slight smaller TSSA than Mt. In addition, EGME reacted strongly with LA producing excess TSSA, which brings about a great difference between LA-Mt and ALA-Mt on EGME adsorption behaviour. These fundamental results demonstrated that OM could strongly affect the EGME adsorption on the OM-Mt complexes and further influence detection of TSSA. The occurrence sites and the functional groups of OM in OM-clay complex must be considered when the EGME adsorption method is used for TSSA evaluation of such clay-rich rocks and soil samples

The composition, pore structure characterization and deformation mechanism of coal-bearing shales from tectonically altered coalfields in eastern China

Organic rich shales in coal-bearing strata deposited from marine to lacustrine environments are well developed in China. The Paleozoic coal-bearing shales have been significantly altered by a series of tectonic movements. Based on XRD, SEM, MICP, and a nitrogen adsorption experiment and in combination with other parameters in this paper, the mineral composition and pore structure characterization and deformation mechanism of coal-bearing shales were surveyed. The coal-bearing shales in eastern China undergo various types of deformation, including brittle, ductile, and brittle-ductile deformation. In eastern China, the macro pore size of shales grew with increasing quartz content under different types of structural deformation, while the specific surface area decreases as the quartz content increases in different types of structural deformation; With the increasing of clay mineral content, the average pore size and the specific surface area of BET became larger in the various types deformation shale, while the pore volume decreased in the brittle and brittle -ductile deformation shale and increased in the ductile deformation shale. The ductile and brittle-ductile deformation increase the specific surface area, the total pore volume of nano-pores, and the adsorption capacity of liquid nitrogen, and decrease the nano pore diameter. The micropores in the brittle-ductile and ductile shearing of clay minerals may the main factors affecting pore volume and total specific surface area. And it is the mesoporous structure that undergoes evolution in brittle-ductile-deformed shales, leading them to have the maximum pore volume and pore-specific surface area for pore-fracture systems. Brittle shear results in micro-fractures or large pores and thus has an impact on the desorption and percolation capability of shale gas, Ductile deformation increases the specific surface area of shales and enhances their shale adsorption capacity

Pyrolysis behaviors of organic matter (OM) with the same alkyl main chain but different functional groups in the presence of clay minerals

Organic matter (OM)-clay mineral complexes, especially OM-clay interlayer complexes, exist widely in soil, sediment, and source rock. These associations can influence the pyrolytic behaviors of OM. In addition, the nature of OM may also affect pyrolysis due to the variety and complexity of the structure and chemical composition of natural organics. In this study, to investigate the influences of the nature of OM as well as the interface association between OM' and clay minerals on the pyrolysis of OM, interlayer clay-OM complexes and clay-OM mixtures were prepared and thermogravimetry coupled with Fourier transform infrared spectroscopy (TG-FTIR) was adapted to monitor the pyrolytic temperatures and products of these complexes. A series of OM with the same alkyl main chain but different functional groups, i.e., Lauric acid (LA), Dodecylamine (DA), 12-Aminolauric acid (ALA) and Dodecyl trimethyl ammonium bromide (DTAB), was used, and montmorillonite (Mt) was selected as the representative clay mineral. The results showed that Mt decreased the decomposition temperature of the carboxyl groups that contained OM (LA and ALA), promoted the generation of CO2 via the catalysis of the Lewis acid sites of Mt, and delayed the decomposition of DA and DTAB. The interlayer Bronsted acid sites allowed the nitrogen-containing organics to undergo Hoffmann elimination. The pyrolytic behaviors of OM within the interlayers of Mt were more strongly affected than those on the external surface of Mt The pyrolytic performance of OM was closely related to the association ways between OM and clay minerals, the nature of clay minerals, and the nature of OM. The interlayer space was shown to be particularly important for the preservation and catalysis of organics

Ethylene glycol monoethyl ether adsorption by interlayer montmorilonite-organic matter complexes: Dependence on the organic matter content and its alkyl chain length

The ethylene glycol monoethyl ether (EGME) adsorption method is an essential and available technique for measuring the total specific surface area (TSSA) of natural rock samples that usually contain an abundant amount of clay-organic matter (clay-OM) complexes. Occurrence sites and types of OM are believed to influence the EGME adsorption behaviors of clay-OM complexes. However, the influence of OM properties on the EGME adsorption mechanism remains unclear until now. In this study, interlayer montmorillonite (Mt)-OM complexes were prepared using the intercalation of OM with various contents and different length of alkyl chains, such as tetramethylammonium bromide (TMAB) and dodecyl trimethyl ammonium bromide (DTAB), based on the cation exchange. EGME adsorption experiments were performed on Mt, OM, and Mt-OM complexes. X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) were used to characterize the structural properties of the samples before and after EGME adsorption. The EGME adsorption capacities and the corresponding TSSA decreased after OM intercalation into the interlayer space of Mt. The OM content and the amounts of alkyl chains significantly affected the EGME adsorption behaviors of Mt-OM complexes. For short alkyl chain OM (TMAB), TSSA values of the Mt-OM complexes decreased with the increase of the interlayer OM content. However, for long alkyl chain OM (DTAB), the TSSA values showed a different variation tendency where the smallest TSSA did not appear in the Mt-OM complex with the highest DTAB content. The initial interlayer distance of Mt-OM complexes and the arrangement of interlayer OM are the primarily factors for EGME adsorption behaviors of the Mt-OM complexes. The large initial interlayer distance favored for incremental expansion of Mt. after EGME adsorption, which promoted EGME molecules entering into the interlayer space. The influence of the arrangement of interlayer OM are primarily involved in some newly formed micropores preventing EGME molecules from entering and more adsorption sites were occupied by OM with a higher ordered mode for the conformation of the alkyl chain and a higher packing density for the arrangement

Smart Energy Clays: Chemical Vapor Deposition of PEDOT in Expanded Vermiculite Blocks for Electrochemical Energy Storage

With rapid development of sustainable energy storage systems and intelligent energy supply equipment, supercapacitors have attracted wide attention while still suffering from low specific capacitance, poor kinetic diffusion, and charge transfer. Here, we demonstrate the concept of integrating conductive polymer poly(3,4-ethylenedioxythiophene) (PEDOT) into insulation voids in expanded vermiculite blocks, achieving PEDOT-intercalated vermiculite electrodes for pseudocapacitive energy storage. The electrodes show rapid kinetic diffusion and charge transfer as well as high areal specific capacitance of 2592 mF cm–2 at the current density of 3 mA cm–2, surpassing most of the state-of-the-art electrodes for supercapacitors. The prepared electrodes were assembled into a symmetrical supercapacitor which shows a specific capacitance of 412.8 mF cm–2 at a current density of 2 mA cm–2 with a high energy density of 30.3 μW h cm–2 at a high power density of 3001.8 μW cm–2. This work realizes the preparation of electrochemical energy storage electrode materials on insulating layer minerals, which is a fruitful tactic and opens the door to the creation of more supercapacitor electrodes

XRD-based quantitative analysis of clay minerals using reference intensity ratios, mineral intensity factors, Rietveld, and full pattern summation methods: A critical review

The quantification of clay minerals is essential for the evaluation of clay-rich rock and soil, but it remains challenging due to the unique structures and various element compositions of clay minerals. In this article, several quantification methods for clay minerals sourced from X-ray diffraction (XRD) analysis, mainly recommending the reference intensity ratio (RIR), mineral intensity factor (MIF), Rietveld, and full pattern summation methods are reviewed. Principles and applications of these methods are focused upon in addition to related differences in the analysis of clay minerals (i.e., sample preparation, the selection of characteristic reflections for quantification and standards added during analysis). This critical review also provides a proposal for selection of an adaptive XRD quantification method to be applied to various clay-rich samples

Facile sample preparation method allowing TEM characterization of the stacking structures and interlayer spaces of clay minerals

Transmission electron microscopy (TEM) is an essential and irreplaceable technique for studying the micro morphology and microstructure of clay minerals. However, observing layer stacking and detecting the interlayer spaces of clay minerals by TEM are still major challenges, due to the difficulty of finding suitable fields of view for clay planes along the [001] direction. A simple and effective sample pretreatment method was proposed here for TEM characterization of clay mineral stacking structures and interlayer spaces. Using this method, clay mineral-bearing ultrathin slices, in which clay minerals particles showed an orientated arrangement, were prepared based on the resin embedding method. The (001) plane of clay minerals was exposed toward electron beams during TEM analysis, and fields of view along the [001] direction were observed, accordingly. This method is thus particularly useful for the observation of stacking information and detection of interlayer regions in clay minerals. The validity of this method is exemplified by its application to pure kaolinite and clay mineral-rich shale samples which contains several clay minerals and the clay mineral-organic matter complexes