Water-saturated Conditions Research Articles

Impact of salt deposition induced by water evaporation on petrophysical properties and pore structure in underground gas storage through dynamic and static experiments

During the production process of underground gas storage (UGS) with high-salinity formation water, salt deposition has been observed due to formation water evaporation. This work aims at understanding the effect of salt deposition on petrophysical properties and pore structure. Firstly, dynamic and static experiments are carried out to simulate the multi-cycle gas injection and production of the UGS based on the core plugs, rock debris and water from Wen23 gas field. Secondly, Nuclear magnetic resonance (NMR), scan electron microscope (SEM) and energy dispersive spectrum (EDS) are applied to investigate the change of pore structure and salt-crystal morphology. Results indicate that the core permeability and porosity after water evaporation are averagely increased by 39 % to 68 % and 42 % to 66 % respectively compared with the initial water saturation conditions under different water salinity. Salt crystals in the reservoir are mainly deposited in large pores. The dispersed and aggregated salt crystals are observed and most salt crystals are between 1 μm and 5 μm in size. Thus, formation water evaporation is beneficial to the improvement of reservoir petrophysical properties without formation water supplement. This work provides an effective method to understand the impact of salt deposition caused by formation water evaporation on the petrophysical properties, fluid flow ability, and gas storage capacity of the UGS and CO2 geological storage.

Effect of grain dissolution on sloping ground

The static and dynamic stability of natural or constructed slopes can be affected by dissolution or dissolution-like phenomena. Their underlying mechanisms, however, remain unclear. New experimental results and discrete element simulations provide particle-level and macroscale information on the consequences of mineral dissolution on slope behavior. At the microscale, load-carrying grain arches develop around dissolving particles, the porosity increases, and contact force chains evolve to form a honeycomb topology. At the macroscale, while vertical settlements are the prevailing deformation pattern, lateral granular movements that create mass wasting are prominent in sloping ground, even under the quasi-static granular loss. Horizontal grain displacement is maximum at the surface and decreases linearly with the distance from the slope surface to become zero at the bottom boundaries, much like vertical granular displacement along the depth. Sediments with smaller friction angles and steeper slopes experience greater displacement, both vertically and horizontally. Slopes become flatter after dissolution, with the reduction in slope angle directly related to the loss in ground elevation, ΔH/Ho. Yet, because of the porous fabric that results from dissolution, vertical shortening is less than the upper bound, estimated from the loss in the solid mass fraction, ΔH/Ho≈SF. Under water-saturated conditions, the post-dissolution fabric may lead to sudden undrained shear and slope slide.

Logan Medallist 7. Appinite Complexes, Granitoid Batholiths and Crustal Growth: A Conceptual Model

Appinite bodies are a suite of plutonic rocks, ranging from ultramafic to felsic in composition, that are characterized by idiomorphic hornblende as the dominant mafic mineral in all lithologies and by spectacularly diverse textures, including planar and linear magmatic fabrics, mafic pegmatites and widespread evidence of mingling between coeval mafic and felsic compositions. These features suggest crystallization from anomalously water-rich magma which, according to limited isotopic studies, has both mantle and meteoric components. Appinite bodies typically occur as small (~2 km diameter) complexes emplaced along the periphery of granitoid plutons and commonly adjacent to major deep crustal faults, which they preferentially exploit during their ascent. Several studies emphasize the relationship between intrusion of appinite, granitoid plutonism and termination of subduction. However, recent geochronological data suggest a more long-lived genetic relationship between appinite and granitoid magma generation and subduction.Appinite may represent aliquots of hydrous basaltic magma derived from variably fractionated mafic underplates that were originally emplaced during protracted subduction adjacent to the Moho, triggering generation of voluminous granitoid magma by partial melting in the overlying MASH zone. Hydrous mafic magma from this underplate may have ascended, accumulated, and differentiated at mid-to-upper crustal levels (ca. 3–6 kbar, 15 km depth) and crystallized under water-saturated conditions. The granitoid magma was emplaced in pulses when transient stresses activated favourably oriented structures which became conduits for magma transport. The ascent of late mafic magma, however, is impeded by the rheological barriers created by the structurally overlying granitoid magma bodies. Magma that forms appinite complexes evaded those rheological barriers because it preferentially exploited the deep crustal faults that bounded the plutonic system. In this scenario, appinite complexes may be a direct connection to the mafic underplate and so its most mafic components may provide insights into processes that generate granitoid batholiths and, more generally, into crustal growth in arc systems.

Mechanical Properties and Failure Behavior of Dry and Water-Saturated Foliated Phyllite under Uniaxial Compression.

Phyllite is widely distributed in nature, and it deserves to be studied considering rock engineering applications. In this study, uniaxial compression tests were conducted on foliated phyllite with different foliation angles under dry and water-saturated conditions. The impacts of water content and foliation angle on the stress-strain curves and basic mechanical properties of the Phyllite were analyzed. The experimental results indicate that the peak stress and peak strain decrease first and then increase with increasing foliation angle as a U-shape or V-shape, and the phyllite specimens are weakened significantly by the presence of water. Moreover, an approach with acoustic emission, digital image correlation, and scanning electron microscopic is employed to observe and analyze the macroscopic and mesoscopic failure process. The results show that tensile microcracks dominate during the progressive failure of phyllite, and their initiation, propagation, and coalescence are the main reasons for the failure of the phyllite specimens. The water acts on biotite and clay minerals that are main components of phyllite, and it contributes to the initiation, propagation, and coalescence of numerous microcracks. Finally, four failure modes are classified as followed: (a) for the specimens with small foliation angles α = 0° or 30° (Saturated), both shear sliding and tensile-split across the foliation planes; (b) for the specimens with low to medium foliation angles α = 30° (Dry) or 45°(Saturated), shear sliding dominates the foliation planes; (c) for the specimens with medium to high foliation angles α = 45° (Dry) or 60°, shear sliding dominates the foliation planes; (d) for the specimens with high foliation angles α = 90°, tensile-split dominates the foliation planes.

Use of wood and cork in biofilters for the simultaneous removal of nitrates and pesticides from groundwater

About 13% and 7% of monitored groundwater stations in Europe exceed the permitted levels of nitrates (50 mg NO3− L−1) or pesticides (0.1 μg L−1), respectively. Although slow sand filtration can remove nitrates via denitrification when oxygen is limited, it requires an organic carbon source. The present study evaluates the performance of the use of wood pellets and granulated cork as carbon sources in bench-scale biofilters operated under water-saturated and water-unsaturated conditions for more than 400 days. The biofilters were monitored for nitrate (200 mg L−1) and pesticide (mecoprop, diuron, atrazine, and bromacil, each at a concentration of 5 μg L−1) attenuation, as well as for the formation of nitrite and pesticide transformation products. Microbiological characterization of each biofilter was also performed. The water-saturated wood biofilter achieved the best nitrate removal (>99%), while the cork biofilters lost all denitrification power over time (from 38% to no removal). The unsaturated biofilter columns were not effective for removing nitrates (20–30% removal). As for pesticides, all the biofilters achieved high removal rates of mecoprop and diuron (>99% and >75%, respectively). Atrazine removal was better in the wood-pellet biofilters than the cork ones (68–96% vs. 31–38%). Bromacil was only removed in the water-unsaturated cork biofilter (67%). However, a bromacil transformation product was formed there. The water-saturated wood biofilter contained the highest number of denitrifying microorganisms, with Methyloversatilis as the characteristic genus. Microbial composition could explain the high removal of pesticides and nitrates achieved in the wood-pellet biofilter. Overall, the results indicate that wood-pellet biofilters operated under water-saturated conditions are a good solution for treating groundwater contaminated with nitrates and pesticides.

Effects of void content on the moisture uptake and mechanical strength of a glass/epoxy composite

The effect of voids on the moisture uptake and transverse modulus and strength of a unidirectional glass/epoxy composite has been examined. To create voids, a foaming agent was mixed with the liquid epoxy resin prior to infusion. Micrographs of polished cross-sections indicate that voids are close to spherical in shape appearing in the matrix and at the fiber/matrix interface. The fiber, matrix, and void contents were analyzed by micrograph, burn-off, and density (Archimedes) methods. The void contents in the void-free and void-containing composites were respectively close to zero and 21%. Specimens were immersed in distilled water at 40°C until saturation. The weight gain was monitored periodically. For the void-free specimens, saturation moisture contents of about 0.60%. The void-containing specimens absorbed much more water, about 5%. The Fickian diffusion model provided good fits to experimental data although the transport mechanism for the void-containing composite appeared non-Fickian. Young’s modulus of the void-free composite was slightly affected by water absorption, although, the transverse tensile strength dropped significantly. Voids were found to substantially reduce transverse modulus and strength about 70%, for both dry and water saturated specimens. Moisture content analysis was in good agreement with experiments for the void-free composite but over-predicted the moisture content for the voidcontaining composite. Micromechanics predictions of the transverse modulus were within 21% of the experimental results for void-free and void containing composites at dry and water saturated conditions.

Experimental investigation on the effect of high-pressure water on tensile strength and microstructure of cementitious materials

The strength of cementitious materials is strongly related to their microstructures. This paper aims to investigate the effect of high-pressure water on the static and dynamic tensile strength of cementitious materials and interpret the influence through the view of microstructure. Specimens were first put in different water pressure (0 MPa, 1 MPa, 3 MPa, and 5 MPa) then their strength and microstructures were measured through splitting tensile tests, SEM tests, and MIP tests. Results showed that as water pressure increased, the strength of mortar decreased with a maximum loss of 32.54 %, while strain rate sensitivity increased. The static strength of saturated specimens was higher than the dried ones under the same water pressure, whereas the opposite results were obtained for dynamic strength. The observed microstructure morphology indicated that higher water pressure would induce more microcracks around pores and around aggregate-matrix interfaces, which led to the loss of strength. The water content and total porosity increased with increasing water pressure. Predictive static and dynamic tensile strength models concerning water pressure, porosity, and saturation states are proposed. The predicted values are in good agreement with the test values.

Gas content prediction model of water-sensitive shale based on gas–water miscible competitive adsorption

The evaluation of gas content plays a key role in determining the efficient development of shale reservoirs. To better understand the gas–water miscible competitive adsorption mechanism in the pore-fracture system of water-bearing shale, the water vapor adsorption experiment of dry shale and the methane gas adsorption experiment of water-bearing shale were carried out to compare and analyze the competitive adsorption laws of formation water and methane gas on the shale surface under different temperatures, pressures, and water saturation conditions. Moreover, based on the molecular layer adsorption theory, the gas–liquid–solid interface competitive adsorption model considering the coupling of temperature, pressure, and water saturation was established to predict the actual gas content of water-bearing shale reservoirs. The results show that the main controlling factors affecting the adsorbed gas content of water-bearing shale are specific surface area, temperature, and water content in turn according to weight coefficients; Compared with the gas–solid adsorption model, the gas–liquid–solid competitive adsorption model has higher accuracy in calculation results, which are much closer to the desorption data of shale cores in Jiaoshiba area, Fuling, China. Hence, the competitive adsorption model provides a theoretical foundation for reasonably evaluating the exploitation potential of shale gas reservoirs.

Assessing water-induced changes in tensile behaviour of porous limestones by means of uniaxial direct pull test and indirect methods

Understanding the uniaxial tensile behaviour of rocks and its water-induced variation are key issues for designing effective mining and civil engineering structures and for assessing numerous geotechnical hazards. However, these aspects remain poorly analysed because conducting uniaxial direct pull tests is a difficult and time-consuming laboratory task that requires the use of sophisticated equipment and complex rock sample preparation and processing. This work attempts to expand knowledge by determining several tensile properties of three porous limestone lithotypes under dry and water-saturated conditions through two different approaches: by conducting direct tensile tests and by means of indirect methods (i.e. Brazilian and point load tests). The results revealed that water saturation generated important reductions in their uniaxial tensile strength (UTS), tensile elastic modulus (Et), Brazilian tensile strength (BTS) and point load strength index (Is(50)). In addition, their petrological characteristics and mineralogical composition are used to discuss the main causes of the observed tensile softening. Furthermore, highly accurate correlation functions were established between the direct tensile strength parameters (UTS and Et) and the indirect ones (BTS and Is(50)) for the whole set of tested rocks. The proposed relationships are a novel and useful contribution to geomechanics because they enable the estimation of pure tensile parameters using alternative, cheap, rapid and versatile tests.

Quest for optimal nanoconfinement for hydrate-based CO2 capture

CO2 capture is a viable solution for mitigating the global CO2 emission in the atmosphere. Hydrate-based CO2 capture is a promising technology. In this study, the CO2 hydrate formation thermodynamics and kinetics, along with the factors that influence CO2 capture in nanoporous silica gels (named S9, S26, and S77 with an average pore size of 9, 26 and 77 nm, respectively), with different degrees of nanoconfinement were investigated. The CO2 hydrate phase equilibrium and dissociation heat were determined by heat flow analysis. The heat flow curves revealed the formation of both confined- and bulk-phase hydrates in S9 and only bulk-phase hydrate in S26 and S77. The phase equilibrium temperature of the confined-phase hydrate was about 10 K lower than that of the bulk-phase hydrate and the dissociation heat of confined phase hydrate is 285.81 J/g in S9. According to the pressure curves, the CO2 hydrate formation time in S9 was 2–3.5 times longer than that in S26 and S77. Compared with dry silica gel, the supersaturated one was more conducive to CO2 capture. Under the same water saturation condition, the CO2 capture ability of S26 and S77 was stronger than that of S9, and the effect of water saturation was dominant over that of pressure. Thus, nanoconfinement in S9 has an adverse effect on hydrate-based CO2 capture whereas that in S26 and S77 is advantageous to it. This study provides an important fundamental basis for enhancing the hydrate-based CO2 capture ability via nanoconfinement in silica gel.

Identification of fluid types and their implications for petroleum exploration in the shale oil reservoir: A case study of the Fengcheng Formation in the Mahu Sag, Junggar Basin, Northwest China

The Fengcheng Formation in the Junggar Basin is a typical shale oil reservoir. Fluid type identification and controlling factors on fluid combination types are significant challenges in shale oil exploration and development. By using two-dimensional (2D) nuclear magnetic resonance (NMR) technology, the accurate boundary values of each fluid type can be determined. Combined with thin sections, scanning electron microscopy (SEM), cathode-luminescence (CL), X-ray diffraction (XRD) and NMR, the effect of lithologies on fluid combination types has been evaluated. The results show that a total of six fluid types can be identified in the Fengcheng Formation, including free oil, adsorbed oil, kerogen, hydroxyls, adsorbed water and free water. Their boundary values on the NMR T1-T2 map can be determined by comparing fluid signals under the original state and water-saturated state after oil washing. In this study, different fluid types eliminated kerogen and hydroxyls can be combined into four fluid combination types defined as Type 1 (free oil, adsorbed oil and adsorbed water), 2 (free oil, adsorbed oil, free water and adsorbed water), 3 (adsorbed oil, free oil and free water) and 4 (movable fluids), existing in the dolomitic shale, mixed shale, felsic shale and sandstone, respectively. Meanwhile, the geometric means of T2 (T2gm) and T2 curves indicate that the pore size can effectively distinguish different lithologies and can be considered as an essential factor influencing the occurrence state of fluids. As the average pore size increases, free water emerges in the mixed shale, and adsorbed water disappears in the felsic shale. Furthermore, after the lithology transforms into sandstone, the fluid type is simple, and only movable fluids exist. Finally, the oil test results imply that the reservoirs with fluid combination Type 4 and Type 3 have relatively high oil production. Therefore, the subsequent orientation for petroleum exploration in shale oil reservoirs targets the sandstone and felsic shale interlayers in the Fengcheng Formation.

Thermal stability of limestone calcined clay cement (LC3) at moderate temperatures 100–400 °C

The mechanical properties, phase evolution, microstructure development and (re)hydration properties of limestone calcined clay cement (LC3) paste and mortar were investigated to understand their thermal stability under moderate temperatures (100–400 °C). The residual compressive strengths of LC3 and Portland cement (PC) mortars kept constant or slightly increased from ambient to 300 °C, and sharply dropped at 400 °C. At 100 °C, monocarboaluminate (Mc) and ettringite (AFt) converted into hemicarboaluminate (Hc) and monosulfate (Ms), and caused partial dehydroxylation of C-(A)-S-H. As the temperature increased, at 200–300 °C, due to the decomposition of large fraction of hydration products, macroscopic cracks and microstructure damage occurred. At 400 °C, the mean chain length (MCL) of C-(A)-S-H gel decreased, accompanied by the shift of Si and Al-coordination number and the formation of active sites. Under water saturation conditions, the microstructure showed self-repairing performance.

Y-B-P-R or S-C-C′? Suggestion for the nomenclature of experimental brittle fault fabric in phyllosilicate-granular mixtures

Mineralogy, fabric, and frictional properties are fundamental aspects of faults. Despite the extensive effort spent in the characterization of such fault properties, the description of fabric elements is not always univocal and nomenclatures such as the Y-B-P-R and the S-C-C′ are at times used interchangeably. This work presents a systematic mineralogical, microstructural, and frictional characterization of natural gouges designed to constrain a criterion for the distinction between the Y-B-P-R and S-C-C′ fabric. For this purpose, we tested four representative natural mixtures of granular minerals (quartz) with increasing amount of phyllosilicates (muscovite). 24 frictional experiments were performed at constant normal stresses of 25, 50, 75 and 100 MPa, at both room dry and water saturated condition. We document that Y-B-P-R fabric typically develops in frictionally strong, granular-rich experimental faults. This fabric is associated to strain localization in narrow shear zones characterized by intense grain size reduction and dominant cataclastic processes. Conversely, S-C-C′ fabric is observed in phyllosilicate-rich experimental faults, which are characterized by distributed deformation and pervasive foliation. Deformation is mainly accommodated by frictional sliding along the well-oriented phyllosilicate foliae. The transition from Y-B-P-R to S-C-C′ is observed for phyllosilicates content >30% and is facilitated by secondary mechanical processes as networking of phyllosilicates and grain mantling. The evolution from Y-B-P-R to S-C-C′ fabric is also associated with a marked reduction in friction, in healing rate and changes in the rate and state friction parameters. Despite their geometrical similarities, we show that Y-B-P-R and S-C-C′ represent distinct fabrics reflecting the dichotomy that exists between frictionally strong, granular-rich, and frictionally weak, phyllosilicate-rich faults.

Facet effect of hematite on the hydrolysis of phthalate esters under ambient humidity conditions

Phthalate esters (PAEs) have been extensively used as additives in plastics and wallcovering, causing severe environmental contamination and increasing public health concerns. Here, we find that hematite nanoparticles with specific facet-control can efficiently catalyze PAEs hydrolysis under ambient humidity conditions, with the hydrolysis rates 2 orders of magnitude higher than that in water saturated condition. The catalytic performance of hematite shows a significant facet-dependence with the reactivity in the order {012} > {104} ≫ {001}, related to the atomic array of surface undercoordinated Fe. The {012} and {104} facets with the proper neighboring Fe-Fe distance of 0.34-0.39 nm can bidentately coordinate with PAEs, and thus induce much stronger Lewis-acid catalysis. Our study may inspire the development of nanomaterials with appropriate surface atomic arrays, improves our understanding for the natural transformation of PAEs under low humidity environment, and provides a promising approach to remediate/purify the ambient air contaminated by PAEs.

Influence of Water Saturation on Curtain Formation of Frozen Wall

In the process of in situ mining of underground oil shale, it is necessary to build an underground frozen wall around the mining area to prevent the inflow of groundwater and prevent oil and gas leakage. However, the water saturation of the frozen soil affects the formation of the freezing circle. In practical engineering, when building a frozen wall in soil under different water saturation conditions, the curtain is often not closed. It also affects the construction and operating costs of the entire project. In this paper, the methods of laboratory experiments and numerical simulation analysis are supplemented by the analysis of ordinary differential equations and partial differential equations. Aiming at the lowest cost, the temperature drop process and freezing time around the frozen well under different water saturation conditions are calculated and analyzed in detail. The formation law of the frozen wall curtain under different water saturation conditions is obtained. It provides a reference for the setting of the low-temperature loading time and the oil shale extraction range of frozen wells for different soils in practical engineering.

Pore-Scale Saturation and Liquid Water Pathways in PEFCs: Insights from Correlative 2D and 3D X-Ray Imaging

Improving the efficiency of polymer electrolyte fuel cells (PEFCs) through high power density operation necessitates liquid water management in the cathode gas diffusion layer (GDL), where liquid water saturation inhibits oxygen diffusivity. To this end, there have been numerous efforts aimed at understanding liquid water transport behaviour to guide GDL design improvements. X-ray imaging of representative in-operando miniaturized PEFC samples has been instrumental to much of recent progress [1–4] in understanding liquid water distribution patterns. Radiographic two-dimensional (2D) images have enabled visualization of liquid water dynamics [3] while three-dimensional (3D) computed tomography images have provided pore-scale information of liquid water saturation states in the GDL [2] and of its transport mechanism [4]. However, how liquid water pathways are formed and the likelihood for preferential pathways remain unclear.In this work, we investigate factors that influence liquid water distribution and pathway definition using correlative rapid 2D and long duration 3D operando X-ray datasets which enable a visualization of liquid water breakthrough dynamics and the corresponding pore-scale interactions in the GDL. The correlated images together with GDL pore structure visualization are used to identify three characteristic pore-scale saturation behaviour with sample regions highlighted in Fig. 1. These regions include locations with restricted liquid water breakthrough, locations with apparent large breakthrough porous pathways where breakthrough liquid water is observable at least in the 2D images, and similarly porous regions where no liquid water breakthrough is observed. It is found that the behaviour shown in the identified regions are strongly linked to local pore-scale structural characteristics and capillary pressure distribution in the GDL. Investigating the 3D virtual GDL from around the microporous layer through to the channel interface, it is shown that liquid water pathways get increasingly defined with a decrease in spatial uniformity towards the flow channels. Pore-scale analysis and observed flow mechanisms show that the defined pathways are locally accessible paths of least capillary resistance dictated by pore radius and associated hydrophobicity. These findings highlight the important role that pore scale topology plays in addition to pore size distribution for future GDL design aimed at improving water management. Keywords— operando, fuel cell, water, pore structure, X-ray imaging Acknowledgments Funding for this research was provided by the Natural Sciences and Engineering Research Council of Canada, Ballard Power Systems, Canada Foundation for Innovation, British Columbia Knowledge Development Fund, Western Economic Diversification Canada, and Canada Research Chairs.

A Technique to Determine the Breakthrough Pressure of Shale Gas Reservoir by Low-Field Nuclear Magnetic Resonance

The porous and low-permeability characteristics of a shale gas reservoir determine its high gas storage efficiency, which is manifested in the extremely high breakthrough pressure of shale. Therefore, the accurate calculation of breakthrough pressure is of great significance to the study of shale gas preservation conditions. Based on a systematic analysis of a low-field NMR experiment on marine shales of the Longmaxi Formation in the Sichuan Basin, a shale gas breakthrough pressure determination technique different from conventional methods is proposed. The conventional methods have low calculation accuracy and are a tedious and time-consuming process, while low-field NMR technique is less time-consuming and of high accuracy. Firstly, the NMR T2 spectrum of shale core sample in different states is measured through low-field NMR experiment. The NMR T2 spectra of sample in water-saturated state and dry state are combined to model the mathematical relationship between shale gas breakthrough pressure and NMR T2 spectrum. It is found that the gas breakthrough pressure is power-exponentially related to the geometric mean of NMR T2 spectrum and positively related to the proportion of micropores. Accordingly, the shale gas breakthrough pressure is quickly and accurately calculated using continuous NMR logging data and then the sealing capacity of the shale caprocks is evaluated, providing basic parameters for analyzing unconventional hydrocarbon accumulation, preservation and migration. This technique has been successfully applied with actual data to evaluate the sealing capacity of shale caprock in a shale gas well in the Sichuan Basin. It can provide a good basis for the evaluation and characterization of shale oil and gas reservoirs.

Global Variations in Water Vapor and Saturation State Throughout the Mars Year 34 Dusty Season.

To understand the evolving martian water cycle, a global perspective of the combined vertical and horizontal distribution of water is needed in relation to supersaturation and water loss and how it varies spatially and temporally. The global vertical water vapor distribution is investigated through an analysis that unifies water, temperature and dust retrievals from several instruments on multiple spacecraft throughout Mars Year (MY) 34 with a global circulation model. During the dusty season of MY 34, northern polar latitudes are largely absent of water vapor below 20km with variations above this altitude due to transport from mid-latitudes during a global dust storm, the downwelling branch of circulation during perihelion season and the intense MY 34 southern summer regional dust storm. Evidence is found of supersaturated water vapor breaking into the northern winter polar vortex. Supersaturation above around 60km is found for most of the time period, with lower altitudes showing more diurnal variation in the saturation state of the atmosphere. Discrete layers of supersaturated water are found across all latitudes. The global dust storm and southern summer regional dust storm forced water vapor at all latitudes in a supersaturated state to 60-90km where it is more likely to escape from the atmosphere. The reanalysis data set provides a constrained global perspective of the water cycle in which to investigate the horizontal and vertical transport of water throughout the atmosphere, of critical importance to understand how water is exchanged between different reservoirs and escapes the atmosphere.

Study on Creep Characteristics of Water Saturated Phyllite

Phyllite is affected by its own bedding, stress environment and water-saturated conditions. There are great differences in its deformation and failure in engineering, and its creep characteristics are an important basis for evaluating the long-term stability of phyllite engineering. Therefore, this study carried out creep tests of water-saturated phyllite under different bedding angles and confining pressures, studied the coupling effect of factors that affect the creep characteristics of phyllite, and investigated and analyzed the deformation characteristics of a phyllite roadway support on site to provide basic support for phyllite roadway mine disaster control and collaborative mining research. The results showed the following: (1) When the bedding dip angle was 30~60°, under the control of the bedding, the sliding deformation along the bedding suddenly increased under the low-stress condition and the specimen did not undergo structural damage. It could continuously bear multi-level stress and generated creep deformation. In this case, a phyllite roadway should adopt the support method of combining flexibility and rigidity. (2) In the process of multi-stage stress loading, the creep instantaneous stress was directly proportional to the initial stress. When the stress was loaded to 50% of the failure strength, the instantaneous stress tended to be stable and maintained a linear, slightly increasing relationship with the stress. When the bedding angle was 30~60°, the creep deformation accounted for more than 50% of the total deformation. The bedding angles of 0° and 90° were dominated by the instantaneous strain during the stress loading process. For the flexible support of the roadway, the deformation caused by disturbance stress should be fully considered. (3) The uniaxial creep specimen mainly displayed compression shear tensile failure, with a small number of parallel cracks along the main fracture surface. The triaxial creep fracture mode changed to single shear failure. The confining pressure showed greater inhibition of the creep of the specimen with a bedding inclination of 0° and 90°. The strength design of the rigid support should refer to the original rock stress value of the roadway. The creep deformation and failure of the specimen with a bedding inclination of 30~60° were mainly controlled by the bedding. The included angle between the bedding dip angle and the maximum principal stress should be kept within 30~60° as far as possible in the roadway layout.

Thermally Insulating, Thermal Shock Resistant Calcium Aluminate Phosphate Cement Composites for Reservoir Thermal Energy Storage.

This paper presents the use of hydrophobic silica aerogel (HSA) and hydrophilic fly ash cenosphere (FCS) aggregates for improvements in the thermal insulating and mechanical properties of 100- and 250 °C-autoclaved calcium aluminate phosphate (CaP) cement composites reinforced with micro-glass (MGF) and micro-carbon (MCF) fibers for deployment in medium- (100 °C) and high-temperature (250 °C) reservoir thermal energy storage systems. The following six factors were assessed: (1) Hydrothermal stability of HSA; (2) Pozzolanic activity of the two aggregates and MGF in an alkali cement environment; (3) CaP cement slurry heat release during hydration and chemical reactions; (4) Composite phase compositions and phase transitions; (5) Mechanical behavior; (6) Thermal shock (TS) resistance at temperature gradients of 150 and 225 °C. The results showed that hydrophobic trimethylsilyl groups in trimethylsiloxy-linked silica aerogel structure were susceptible to hydrothermal degradation at 250 °C. This degradation was followed by pozzolanic reactions (PR) of HSA, its dissolution, and the formation of a porous microstructure that caused a major loss in the compressive strength of the composites at 250 °C. The pozzolanic activities of FCS and MGF were moderate, and they offered improved interfacial bonding at cement-FCS and cement-MGF joints through a bridging effect by PR products. Despite the PR of MGF, both MGF and MCF played an essential role in minimizing the considerable losses in compressive strength, particularly in toughness, engendered by incorporating weak HSA. As a result, a FCS/HSA ratio of 90/10 in the CaP composite system was identified as the most effective hybrid insulating aggregate composition, with a persistent compressive strength of more than 7 MPa after three TS tests at a 150 °C temperature gradient. This composite displayed thermal conductivity of 0.28 and 0.35 W/mK after TS with 225 and 150 °C thermal gradients, respectively. These values, below the TC of water (TC water = 0.6 W/mK), were measured under water-saturated conditions for applications in underground reservoirs. However, considering the hydrothermal disintegration of HSA at 250 °C, these CaP composites have potential applications for use in thermally insulating, thermal shock-resistant well cement in a mid-temperature range (100 to 175 °C) reservoir thermal energy storage system.