scholarly journals Experimental Investigation of Mechanical Properties of Black Shales after CO2-Water-Rock Interaction

2016 ◽  
Author(s):  
Qiao Lyu ◽  
P.G. Ranjith ◽  
Xinping Long ◽  
Bin Ji
Keyword(s):  
Mechanical Properties ◽  
Black Shales ◽  
Brittleness Index ◽  
Sem Images ◽  
Rock Interaction ◽  
Saturation Time ◽  
Eds Analysis ◽  
Shale Reservoirs ◽  
Cumulative Ae Energy ◽  
Water Rock Interaction

The effects of CO2-water-rock interactions on the mechanical properties of shale are essential for estimating the possibility of sequestrating CO2 in shale reservoirs. In this study, uniaxial compressive strength (UCS) tests together with an acoustic emission (AE) system and SEM & EDS analysis were performed to investigate the mechanical properties and microstructural changes of black shales with different saturation times (10 days, 20 days and 30 days) in water dissoluted with sub-/super-critical CO2. According to the experimental results, the values of UCS, Young’s modulus and brittleness index decrease gradually with increasing saturation time in water with sub-/super-critical CO2. Compared to intact samples, 30-days’ saturation causes reductions of 56.43% in UCS and 54.21% in Young’s modulus for sub-critical saturated samples, and 66.05% in UCS and 56.32% in Young’s modulus for super-critical saturated samples, respectively. The brittleness index also decreases drastically from 84.3% for intact samples to 50.9% for samples saturated in water with sub-critical CO2, to 47.9% for samples saturated in water with super-critical carbon dioxide (SC-CO2). SC-CO2 causes a greater reduction of shale’s mechanical properties. The crack propagation results obtained from the AE system show that longer saturation time produces higher peak cumulative AE energy. SEM images show that many pores occur when shale samples are saturated in water with sub-/super-critical CO2. The EDS results show that CO2-water-rock interactions increase the percentages of C and Fe and decrease the percentages of Al and K on the surface of saturated samples when compared to intact samples.

scholarly journals Effect of Dry-Wet Cycling on the Mechanical Properties of Rocks: A Laboratory-Scale Experimental Study

Processes ◽  
2018 ◽  
Vol 6 (10) ◽  
pp. 199 ◽  
Author(s):  
Xiaojie Yang ◽  
Jiamin Wang ◽  
Dinggui Hou ◽  
Chun Zhu ◽  
Manchao He
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
Uniaxial Compressive Strength ◽  
Open Pit ◽  
Rock Surface ◽  
Periodic Action ◽  
Rock Interaction ◽  
The Impact ◽  
Water Rock Interaction

Taking Nanfen open-pit iron mine in Liaoning Province as the engineering background, this study analyzes the effect of water-rock circulation on the mechanical properties of rock through a combination of macro-mechanical experiments and microstructure tests in the laboratory. Uniaxial compression experiments and acoustic wave tests are used to determine the degradation law of the mechanical properties of chlorite under the periodic action of water. The experimental results show that dry-wet cycles have a continuous and gradual effect on the rock sampled: Its uniaxial compressive strength, elastic modulus, and acoustic velocity all decrease gradually with an increase in the number of cycles. After 15 wet-dry cycles, the uniaxial compressive strength and elastic modulus of the rock decreased by 34.21% and 44.63%, respectively. Electron microscope scans of the rock indicate that the particle size, characteristics, and pore distribution at the rock surface had changed significantly after water-rock interaction. Finally, a drainage system and sliding force monitoring devices have been arranged at the mine site that can effectively reduce the impact of water-rock interaction on the stability of the mine. This combination of macro-experiments and micro-analysis allowed the weakening effect of dry-wet cycles on slope rock to be studied quantitatively, providing a theoretical reference for stability evaluation in geotechnical engineering.

scholarly journals Mechanical Properties of Weathered Feldspar Sandstone after Experiencing Dry-Wet Cycles

2020 ◽  
Vol 2020 ◽  
pp. 1-15 ◽  
Author(s):  
Wen-bo An ◽  
Laigui Wang ◽  
He Chen
Keyword(s):  
Mechanical Properties ◽  
Salt Crystallization ◽  
Salt Rock ◽  
Rock Interaction ◽  
Maximum Variation ◽  
Group A ◽  
Yungang Grottoes ◽  
Group B ◽  
Water Swelling ◽  
Water Rock Interaction

Weathering is one of the important geological hazards to many stone cultural relics carved on feldspar sandstone (such as the Datong Yungang Grottoes). To study the mechanical properties of the weathered Yungang Grottoes, feldspar sandstone was subjected to comparative dry-wet cycle tests with water-rock interaction (Group A) and salt-rock interaction (Group B). The variation patterns of the macroscopic physical and mechanical parameters as well as the micro/mesoscopic structures of the two groups of feldspar sandstone with the number of dry-wet cycles were measured. The results showed that for the Group A and Group B sandstones, as the number of dry-wet cycles increased the saturated water absorption and the longitudinal wave velocity increased, with the maximum variation rates reaching 28.02%, 36.98%, 16.20%, and 33.27%. The peak strength and elastic modulus gradually decreased, with the maximum variation rate reaching 48.53%, 73.44%, 26.61%, and 72.39%. The surface height deviation increased by as much as 1.06 μm and 3.34 μm. The mechanism of weathering for the water-rock interaction included three effects, namely, the hydrolysis of the K-Na feldspar, the water swelling of the clay minerals such as kaolinite, and the dissolution of the soluble minerals. The mechanism of weathering for the salt-rock interaction included salt crystallization in the pores or fissures and chemical reactions between the minerals (such as feldspar and calcite) and sulfate, in addition to the above three effects. Therefore, the crystallization stress of the salt exerted the most notable effect on the deterioration of the feldspar sandstone. The results are expected to provide a reference for the stability evaluation and protection of the rock mass of the Grottoes.

Synthesis, Characterization and Application of N,N-Dimethyl-N-Sulfoethan Ammonium tetra-Chloro Aluminate: A Novel micro-Heterogeneous Cata-lyst for Synthesis of tri-Arylmethanes

2020 ◽  
Vol 17 ◽  
Author(s):  
Saeid Azimi ◽  
Niloofar Mohamadighader
Keyword(s):  
Ionic Liquid ◽  
Heterogeneous Catalyst ◽  
Mass Spectroscopy ◽  
Aromatic Aldehydes ◽  
Solid Catalyst ◽  
Sem Images ◽  
One Pot ◽  
Acidic Catalyst ◽  
Eds Analysis ◽  
Ft Ir

Abstract: A new solid catalyst was synthesized from an ionic liquid and heterogenised by changing anion reaction. The new heterogeneous acidic catalyst was characterized by SEM images, EDS analysis, AFM images, Ft-IR, HNMR, 13CNMR and Mass Spectroscopy. It was applied to synthesis of tri-arylmethanes throughout one-pot tri-component reactions among aromatic aldehydes, N,N-dimethylaniline and other carbonic nucleophiles such as anisole and indole. Hence, synthesis of convenient and inexpensive micro-heterogeneous catalyst was introduced, the efficiency of which was confirmed. Also, various useful products were synthesized throughout this simple and clean procedure.

87SR/86SR, δ18O AND NOBLE GASES AS TRACERS OF WATER-ROCK INTERACTION IN THE THEISTAREYKIR GEOTHERMAL FIELD

2020 ◽  
Author(s):  
Marie Haut-Labourdette ◽  
◽  
Daniele Pinti ◽  
André Poirier ◽  
Marion Saby ◽  
...  
Keyword(s):  
Noble Gases ◽  
Geothermal Field ◽  
Rock Interaction ◽  
Water Rock Interaction

Magnetite texture and trace-element geochemistry fingerprint of pulsed mineralization in the Xinqiao Cu-Fe-Au deposit, Eastern China

2020 ◽  
Vol 105 (11) ◽  
pp. 1712-1723
Author(s):  
Yu Zhang ◽  
Pete Hollings ◽  
Yongjun Shao ◽  
Dengfeng Li ◽  
Huayong Chen ◽  
...  
Keyword(s):  
Trace Element ◽  
Triple Junction ◽  
Eastern China ◽  
Black Shales ◽  
Hydrothermal Fluids ◽  
Oscillatory Zoning ◽  
Trace Element Geochemistry ◽  
Element Geochemistry ◽  
Rock Interaction ◽  
Multiple Pulses

Abstract The origin of stratabound deposits in the Middle-Lower Yangtze River Valley Metallogenic Belt (MLYRB), Eastern China, is the subject of considerable debate. The Xinqiao Cu-Fe-Au deposit in the Tongling ore district is a typical stratabound ore body characterized by multi-stage magnetite. A total of six generations of magnetite have been identified. Mt1 is commonly replaced by porous Mt2, and both are commonly trapped in the core of Mt3, which is characterized by both core-rim textures and oscillatory zoning. Porous Mt4 commonly truncates the oscillatory zoning of Mt3, and Mt5 is characterized by 120° triple junction texture. Mt1 to Mt5 are commonly replaced by pyrite that coexists with quartz, whereas Mt6, with a fine-grained foliated and needle-like texture, commonly cuts the early pyrite as veins and is replaced by pyrite that coexists with calcite. The geochemistry of the magnetite suggests that they are hydrothermal in origin. The microporosity of Mt2 and Mt4 magnetite, their sharp contacts with Mt1 and Mt3, and lower trace-element contents (e.g., Si, Ca, Mg, and Ti) than Mt1 and Mt3 suggest that they formed via coupled dissolution and reprecipitation of the precursor Mt1 and Mt3 magnetite, respectively. This was likely caused by high-salinity fluids derived from intensive water-rock interaction between the magmatic-hydrothermal fluids associated with the Jitou stock and Late Permian metalliferous black shales. The 120° triple junction texture of Mt5 suggests it is the result of fluid-assisted recrystallization, whereas Mt6 formed by replacement of hematite as a result of fracturing. The geochemistry of the magnetite suggests that the temperature increased from Mt2 to Mt3 and implies that there were multiple pulses of fluids from a magmatic-hydrothermal system. Therefore, we propose that the Xinqiao stratiform mineralization was genetically associated with multiple influxes of magmatic hydrothermal fluids derived from the Early Cretaceous Jitou stock. This study demonstrates that detailed texture examination and in situ trace-elements analysis under robust geological and petrographic frameworks can effectively constrain the mineralization processes and ore genesis.

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