The influence of water-based drilling fluid on mechanical property of shale and the wellbore stability

AbstractBecause of high cost and pollution of oil-based drilling fluid, the water-based drilling fluid is increasingly used now. However, bedding planes and micro-cracks are rich in shale formation. When water-based drilling fluid contacts formation rock, it causes the propagation of crack and invasion of drilling fluid, which decrease shale strength and cause wellbore instability. In this paper, we analyzed influence of water-based drilling fluid on shale strength and failure mode by mechanics experiment. Based on those experimental results, considering the effect of bedding plane and drilling time, we established modeling of wellbore stability for shale formation. The result from this model indicates that in certain azimuth of horizontal well, collapsing pressure increases dramatically due to shale failure along with bedding plane. In drilling operation, those azimuths are supposed to be avoided. This model is applicable for predication of collapsing pressure in shale formation and offers reference for choosing suitable mud weight

Studies on the interaction of achiral cationic pseudoisocyanine with chiral metal complexes

The effect of chiral metal complexes ([Co(en)(3)]I(3)center dot H(2)O, cis-[CoBr(NH(3))(en)(2)]Br(2), K[Co(edta)]center dot 2H(2)O and [Ru(phen)(3)](PF(6))(2)) on the polymer-bound J-aggregates in aqueous mixtures of pesudoisocyanine (PIC) iodine and poly(acrylic acid, sodium)(PAAS) have been studied by UV-vis absorption, circular dichroism (CD) and fluorescence spectra. At low concentration, the PIC monomers could self-assemble to form supermolecules by binding to each of the COO(-) groups on the polymer chains through electrostatic interactions. After the addition of chiral metal complexes to the formed PIC-PAAS J-aggregates, we found that only the chiral multiple pi-conjugated phenanthroline metal complexes could transfer their metal-centered chiral information to the formed J-aggregates. The chiral J-aggregates showed a characteristic induced circular dichroism (ICD) in the visible region of J-band chromophore, and the ICD signals depend on the absolute configuration, concentration of the chiral multiple pi-conjugated metal complexes, as well as temperature. More interestingly, the supramolecular chirality of the polymer supported PIC J-aggregates could be memorized even after the addition of an excess opposite chiral complex enantiomers. This is in sharp contrast to the behavior in the high concentrated NaCl induced PIC-J aggregates, in which the optical rotation of a mixture of two enantiomers varies linearly with their ratio.National Natural Science Foundation of China[20773098, 20877099, 20972183]; State Key Laboratory of Natural and Biomimetic Drugs[20080208]; GUCAS (A B); Ministry of Science and Technology of China[2008AA100801]; CAS[2010B090300031]; Guangdong Provinc

Colorimetric Assay for Determination of Lead (II) Based on Its Incorporation into Gold Nanoparticles during Their Synthesis

In this report, we present a new method for visual detection of Pb2+. Gold nanoparticles (Au-NPs) were synthesized in one step at room temperature, using gallic acid (GA) as reducer and stabilizer. Pb2+ is added during the gold nanoparticle formation. Analysis of Pb2+ is conducted by a dual strategy, namely, colorimetry and spectrometry. During Au-NPs synthesis, addition of Pb2+ would lead to formation of Pb-GA complex, which can induce the aggregation of newly-formed small unstable gold nanoclusters. Consequently, colorimetric detection of trace Pb2+ can be realized. As the Pb2+ concentration increases, the color turns from red-wine to purple, and finally blue. This method offers a sensitive linear correlation between the shift of the absorption band (Δλ) and logarithm of Pb2+ concentration ranging from 5.0 × 10−8 to 1.0 × 10−6 M with a linear fit coefficient of 0.998, and a high selectivity for Pb2+ detection with a low detection limit down to 2.5 × 10−8 M

Transformation, memorization and amplification of chirality in cationic Co(III) complex-porphyrin aggregates

Lambda-and Delta-enantiomers of cis-[CoBr(NH3)(en)(2)]Br-2 were obtained by absolute asymmetric synthesis. The interactions between the achiral 5,10,15,20-tetrakis(4-sulfonatophenyl) porphyrin (TPPS) and two chiral cationic Co(III) complexes were studied by UV-vis spectroscopy, circular dichroism (CD), fluorescence spectroscopy and atomic force microscopy (AFM). It was found that the cationic Co( III) complexes can induce the formation of chiral porphyrin J-aggregates, that the metal-centered chirality can be transferred to the J-aggregates, and that the chirality was able to be memorized and amplified in the porphyrin J-aggregates. Therefore, this should be a good chiral model for understanding similar processes in physical and biological systems.National Natural Science Foundation of China [20773098, 20877099, 20972183]; State Key Laboratory of Natural and Biomimetic Drugs [20080208]; GUCAS [065101HM03 B

Aggregation of an anionic porphyrin with chiral metal complexes and the competitive binding influences of a surfactant and a polyelectrolyte

The non-covalent interactions of chiral metal complexes with the achiral 5,10,15,20-tetrakis (4-sulonatophenyl) porphyrin (H(4)TTPS(2-)) have been investigated by UV-vis and circular dichroism (CD) spectra. The results show that under acidic environments, only the chiral complex cations ([CoBr(NH(3))(en)(2)](+), [Co(en)(3)](3+), [Ru(phen)(3)](2+)) could interact with H(4)TTPS(2-) to form chiral aggregates, accompanied with the metal-centered chirality information transferred to the formed J-aggregates. However, the chiral complex anion ([Co(edta)](-)) does not cause the self-assembly process. The competitive binding interactions between an achiral water-soluble cationic surfactant (N-hexadecyltrimethyl ammonium chloride, CTAC) and a cationic polyelectrolyte (polyallylamine, PAA) with the chiral metal complex H(4)TTPS(2-) J-aggregates, respectively, were also investigated. It was found that chiral-symmetry-breaking phenomena occur in the cationic surfactant induced event. In the case of a cationic polyelectrolyte, it could change the conformational flexibility of the H(4)TTPS(2-) aggregates. These results may lead us to understand the possible mechanism of the supramolecular self-assembly process by the non-covalent interactions.National Natural Science Foundation of China[20973136, 20877099, 20972183]; State Key Laboratory of Natural and Biomimetic Drugs[20080208]; Hunan High Education Research Fund[06C068]; GUCAS (A B); Ministry of Science and Technology of China[2008AA100801]; Guangdong Province[2010B090300031]; CAS[2010B090300031

Adsorption Behavior of Methane on Kaolinite

In this work, the adsorption behaviors of CH₄ in slit-like kaolinite pores were investigated using the grand canonical Monte Carlo method. The research results show that the isosteric heat of adsorption of CH₄ decreases with increasing pore size and that CH₄ adsorption on kaolinite can be characterized as physical adsorption. The potential energy between CH₄ and kaolinite was found to decrease with increasing pressure or decreasing pore size, indicating that the adsorption sites of CH₄ changed from higher-energy adsorption sites to lower-energy adsorption sites. The CH₄ adsorption capacity decreased with increasing pore size in mesopores. With increasing temperature, the isosteric heat of adsorption of CH₄ decreased, and the adsorption sites of CH₄ changed from higher-energy adsorption sites to lower-energy adsorption sites, resulting in a decrease of the CH₄ adsorption capacity. As a result of van der Waals force interactions, Coulomb force interactions, and hydrogen-bonding interactions, the water molecules in the kaolinite pores occupies the pore walls in a directional manner, causing the water molecules in the kaolinite pores to accumulate. With increasing accumulation of water, the water molecules occupied adsorption spaces and adsorption sites of CH₄, leading to a decrease of the CH₄ adsorption capacity. The gas adsorption capacity on kaolinite was found to decrease in the following order: CO₂ > CH₄ > N₂. With increasing mole fraction of N₂ or CO₂, the mole fraction of CH₄ in the gas phase decreased, the adsorption sites of CH₄ changed, and the adsorption space of CH₄ decreased, resulting in a decrease of CH₄ adsorption capacity

Schizandrin A Inhibits Microglia-Mediated Neuroninflammation through Inhibiting TRAF6-NF-κB and Jak2-Stat3 Signaling Pathways.

Microglial-mediated neuroinflammation has been established as playing a vital role in pathogenesis of neurodegenerative disorders. Thus, rational regulation of microglia functions to inhibit inflammation injury may be a logical and promising approach to neurodegenerative disease therapy. The purposes of the present study were to explore the neuroprotective effects and potential molecular mechanism of Schizandrin A (Sch A), a lignin compound isolated from Schisandra chinesnesis. Our observations showed that Sch A could significantly down-regulate the increased production of nitric oxide (NO), tumor necrosis factor (TNF)-α and interleukin (IL)-6 induced by lipopolysaccharide (LPS) both in BV-2 cells and primary microglia cells. Moreover, Sch A exerted obvious neuroprotective effects against inflammatory injury in neurons when exposed to microglia-conditioned medium. Investigations of the mechanism showed the anti-inflammatory effect of Sch A involved the inhibition of inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX-2) expression levels and inhibition of the LPS-induced TRAF6-IKKβ-NF-κB pathway. Furthermore, inhibition of Jak2-Stat3 pathway activation and Stat3 nuclear translocation also was observed. In conclusion, SchA can exert anti-inflammatory and neuroprotective effects by alleviating microglia-mediated neuroinflammation injury through inhibiting the TRAF6-IKKβ-NF-κB and Jak2-Stat3 signaling pathways

Global distribution of perfluorochemicals (PFCs) in potential human exposure source-A review

Human exposure to perfluorochemicals (PFCs) has attracted mounting attention due to their potential harmful effects. Breathing, dietary intake, and drinking are believed to be the main routes for PFC entering into human body. Thus, we profiled PFC compositions and concentrations in indoor air and dust, food, and drinking water with detailed analysis of literature data published after 2010. Concentrations of PFCs in air and dust samples collected from home, office, and vehicle were outlined. The results showed that neutral PFCs (e.g., fluorotelomer alcohols (FTOHs) and perfluorooctane sulfonamide ethanols (FOSEs)) should be given attention in addition to PFOS and PFOA. We summarized PFC concentrations in various food items, including vegetables, dairy products, beverages, eggs, meat products, fish, and shellfish. We showed that humans are subject to the dietary PFC exposure mostly through fish and shellfish consumption. Concentrations of PFCs in different drinking water samples collected from various countries were analyzed. Well water and tap water contained relatively higher PFC concentrations than other types of drinking water. Furthermore, PFC contamination in drinking water was influenced by the techniques for drinking water treatment and bottle-originating pollution

Methane Adsorption on Carbon Models of the Organic Matter of Organic-Rich Shales

The organic matter in organic-rich shales has an important significance for the methane adsorption capacity on shales. Kerogen is simplified to ideal graphite, and oxygenated functional groups are grafted onto graphite surfaces to obtain different O/C atomic ratios, reflecting varying maturation levels of kerogen. The adsorption behaviors of methane in the pores of graphite with different O/C ratios were investigated by the grand canonical Monte Carlo method. The results show that the isosteric heat of adsorption of methane is reduced with an increase in the pore size or a decrease in the O/C ratio. The methane adsorption capacity in micropores increases with an increasing pore size, whereas it decreases with an increasing pore size in mesopores. The methane adsorption capacity in pores with the same pore size decreases with decreasing O/C ratio. The proportion of the adsorbed gas in the pores decreases either with increasing pressure with the same pore size or with an increasing pore size under the same pressure. Methane in the organic pores of the organic-rich shales is mainly in the adsorbed state when the pore size is less than 6 nm. The adsorption sites of methane gradually change from lower energy adsorption sites to higher energy ones with increasing temperature, leading to the reduction of the methane adsorption capacity. The water molecules in the pore affected by van der Waals forces, Coulombic forces, and hydrogen-bonding interactions are close to the oxygen-containing groups and occupy the adsorption space of methane molecules, leading to a decrease of the methane adsorption capacity. The reduction of the mole fraction of methane in the gas phase, change of adsorption sites of methane, and decrease of the adsorption space of methane generate the methane adsorption capacity for the methane/carbon dioxide binary gas mixture adsorption system

Complexes of Fe(III)-organic pollutants that directly activate Fenton-like processes under visible light

The major challenge of Fenton and Fenton-like technologies is promoting the effective transformation of Fe3+ to Fe2+. Photoinduced ligand-to-metal charge transfer (LMCT) enables charge to transfer effectively from the complex ligand to metal ions for the subsequent redox reactions. This study shows that photoactivated LMCTs relying on internal charge transfers occurred from the pollutant complex to the Fe3+ center and followed the in situ transformation of Fe3+ to Fe2+ without the addition of other ligands or agents. Using the antibiotic pollutant sulfamethoxazole (SMX), a direct Fe-SMX complex is formed and enables visible light to be used to activate peroxydisulfate (PDS) by Fe3+ for the rapid degradation of SMX at a rate 6.5-times higher than that observed by the conventional Fe2+/PDS system. This study outlines a new and cost-effective LMCT activation approach and broadens our knowledge of the ability of Fe3+ to be applied in Fenton-like reactions for environmental remediation.11Nscopu