Characteristics of dissolved pores and dissolution mechanism of zeolite-rich reservoirs in the Wuerhe Formation in Mahu area, Junggar Basin

The reservoir in the Wuerhe Formation in the Mahu Sag, northwestern Junggar Basin, China, exhibits complex dissolution and cementation related to zeolite. The source and mechanism of diagenetic fluids are crucial in studying the reservoir genesis. Thus we investigated the key reservoirs fluids related to the zeolite and discussed their significance in the zeolite-rich reservoir of the Permian Wuerhe Formation in the Mahu Sag. Based on thin sections and electron microscope observations of rock samples and analyses of physical properties, C-O isotopes, and major elements, it is found that the reservoir underwent mainly two stages of fluid-related dissolution and cementation processes, in which the hydrocarbon-bearing fluid played the primary role in forming the high-quality reservoir. Dissolution pores are the most important storage space, and zeolite cement is the most important dissolution mineral. The geochemical characteristics of zeolite and calcite cement indicate the presence of two diagenetic fluids. The iron-rich calcite and orange-red heulandite is related to early diagenetic fluids with high iron content and higher carbon isotope values, whereas the calcites, with high manganese content and lower carbon isotope values, are formed by late acidic organic diagenetic fluids related to oil and gas activities. The hydrocarbon-bearing fluids form different spatial diagenetic zones, including the dissolution zone, buffer zone, and cementation zone, and the dissolution zone near the oil source fault is the main site of zeolite dissolution. The late fluid has the characteristics of multi-stage activity, which makes the spatial zoning expand gradually, resulting in multiple superpositions of dissolution and cementation and increasing the complexity and heterogeneity of the reservoir diagenesis. This study expands the understandings of the dissolution activities of different fluids in zeolite-rich reservoirs and also has reference significance for dissolution activity of hydrocarbon fluid in other types of reservoirs.

Synthesis and some properties of compounds Cu2PrSb3S7 and Cu2ErSb3S7

The phase equilibrium in systems of CuSbS2 – PrSbS3 and CuSbS2 – ErSbS3 has been studied by physicochemical methods (Differential thermal analysis – DTA, X-ray diffraction phase analysis, Scanning Electron Microscopy – SEM analysis and microhardness testing) and their T-x diagrams were drawn. It was determined that both systems are quazibinary and characterized by formation of Cu2LnSb3S7 -type (Ln = Pr, Er) compounds. Cu2PrSb3S7 melts congruently at 1050 K and is the phase with unstable content. Its dissolution zone changes within concentration interval of 32-37 mole% of PrSbS3. Cu2PrSb3S7 divides the system into two sub-systems: CuSbS2-Cu2PrSb3S7 and Cu2PrSb3S7-PrSbS3. Both of sub-systems are eutectic. The coordinates of the eutectic point are like following: 15 mole % PrSbS3, T = 740 K and 50 mole % PrSbS3, T = 790 K. Cu2ErSb3S7 melts at 920 K by decomposition. At 725K between Cu2ErSb3S7 and CuSbS2 compounds in content of 15 mole % of ErSbS3 is formed eutectic balance. 4 mole % of solid solution is formed on base of CuSbS2. Both compounds are crystallized by naffildite-type structure in the form of rhombic syngonia (Cu2PrSb3S7 – a = 1.444; b = 2.146; c = 0.3995 nm; z = 4; Cu2ErSb3S7 – a = 1.430; b = 2.128; c = 0.380 nm; z = 4; stereogroup Pbnm or Pbn21).

Reductive dissolution of biogenic magnetite

Reductive dissolution of magnetite is known to occur below the Fe-redox boundary in sediments. In this study, detailed processes associated with biogenic magnetite dissolution are documented. A sediment core from the Japan Sea was used for this purpose, in which reductive dissolution of magnetic minerals is known to start at depths of about 1.15 m and is mostly complete within a depth interval of about 0.35 m. Using first-order reversal curve diagrams, preferential dissolution of biogenic magnetite within this interval is estimated from the observation that a narrow peak that extends along the coercivity axis (central ridge), which is indicative of biogenic magnetite, diminishes downcore. Transmission electron microscopy is used to demonstrate that the sediments contain three magnetofossil morpho-types: octahedra, hexagonal prisms, and bullet-shaped forms. Within the reductive dissolution zone, partially etched crystals are commonly observed. With progressive dissolution, the proportion of bullet-shaped magnetofossils decreases, whereas hexagonal prisms become more dominant. This observation can be explained by the differences in resistance to dissolution among crystal planes of magnetite and the differences in surface area to volume ratios. Magnetofossil morphology may reflect the preference of magnetotactic bacterial lineages for inhabiting specific chemical environments in sediments. However, it could also reflect alteration of the original morphological compositions during reductive diagenesis, which should be considered when using magnetofossil morphology as a paleoenvironmental proxy.

Reductive dissolution of biogenic magnetite

Reductive dissolution of magnetite is known to occur below the Fe-redox boundary in sediments. In this study detailed processes associated with biogenic magnetite dissolution are documented. A sediment core from the Japan Sea was used for this purpose, in which reductive dissolution of magnetic minerals is known to start at depths of about 1.15 m and is mostly complete within a depth interval of about 0.35 m. Using first-order reversal curve diagrams, preferential dissolution of biogenic magnetite within this interval is estimated from the observation that a narrow peak that extends along the coercivity axis (central ridge), which is indicative of biogenic magnetite, diminishes downcore. Transmission electron microscopy is used to demonstrate that the sediments contain three magnetofossil morpho-types: octahedra, hexagonal prisms, and bullet-shaped forms. Within the reductive dissolution zone, partially etched crystals are commonly observed. With progressive dissolution, the proportion of bullet-shaped magnetofossils decreases, whereas hexagonal prisms become more dominant. This observation can be explained by the differences in resistance to dissolution among crystal planes of magnetite and the differences in surface area to volume ratios. Magnetofossil morphology may reflect the preference of magnetotactic bacterial lineages for inhabiting specific chemical environments in sediments. However, it could also reflect alteration of the original morphological compositions during reductive diagenesis, which should be considered when using magnetofossil morphology as a paleoenvironmental proxy.

Reductive dissolution of biogenic magnetite

Reductive dissolution of magnetite is known to occur below the Fe-redox boundary in sediments. In this study detailed processes associated with biogenic magnetite dissolution are documented. A sediment core from the Japan Sea was used for this purpose, in which reductive dissolution of magnetic minerals is known to start at depths of about 1.15 m and is mostly complete within a depth interval of about 0.35 m. Using first-order reversal curve diagrams, preferential dissolution of biogenic magnetite within this interval is estimated from the observation that a narrow peak that extends along the coercivity axis (central ridge), which is indicative of biogenic magnetite, diminishes downcore. Transmission electron microscopy is used to demonstrate that the sediments contain three magnetofossil morpho-types: octahedra, hexagonal prisms, and bullet-shaped forms. Within the reductive dissolution zone, partially etched crystals are commonly observed. With progressive dissolution, the proportion of bullet-shaped magnetofossils decreases, whereas hexagonal prisms become more dominant. This observation can be explained by the differences in resistance to dissolution among crystal planes of magnetite and the differences in surface area to volume ratios. Magnetofossil morphology may reflect the preference of magnetotactic bacterial lineages for inhabiting specific chemical environments in sediments. However, it could also reflect alteration of the original morphological compositions during reductive diagenesis, which should be considered when using magnetofossil morphology as a paleoenvironmental proxy.

Morphophysiological seed dormancy inHeptacodium

Heptacodium miconiodesis an endangered, monotypic genus in the Caprifoliaceae endemic to China. Species within the Caprifoliaceae have been shown to have morphological or morphophysiological dormancy.Heptacodiumseeds had an underdeveloped embryo at the time of fruit dispersal with an embryo that occupied approximately 12% of the seed length. Cold (8 weeks at 5°C) and warm (8 weeks at 20°C) stratification was effective for dormancy release, but embryo growth prior to germination only occurred at warm temperatures (20°C). Gibberellic acid treatment partially substituted for cold stratification. Final seed germination percentage was not different after warm or cold stratification; however, seeds initially exposed to cold stratification germinated faster and more uniformly. Cold stratified seeds reached 50% final germination approximately 55 days sooner than warm stratified seeds. Prior to radicle emergence, embryos grew to fill approximately 60% of the seed through an endosperm channel that occupied the centre portion of the endosperm. Cells in the endosperm channel had thinner cell walls and fewer storage vesicles compared with other endosperm cells. Channel cells formed a dissolution zone ahead of embryo elongation assumed to be involved with enzymatic hydrolysis of storage reserves. Based on these results, it was concluded thatHeptacodiumdisplays the characteristics of seeds with non-deep simple morphophysiological dormancy.

Carbon dynamics from carbonate dissolution in Australian agricultural soils

Land-use and management practices on limed acidic and carbonate-bearing soils can fundamentally alter carbon (C) dynamics, creating an important feedback to atmospheric carbon dioxide (CO2) concentrations. Transformation of carbonates in such soils and its implication for C sequestration with climate change are largely unknown and there is much speculation about inorganic C sequestration via bicarbonates. Soil carbonate equilibrium is complicated, and all reactants and reaction products need to be accounted for fully to assess whether specific processes lead to a net removal of atmospheric CO2. Data are scarce on the estimates of CaCO3 stocks and the effect of land-use management practices on these stocks, and there is a lack of understanding on the fate of CO2 released from carbonates. We estimated carbonate stocks from four major soil types in Australia (Calcarosols, Vertosols, Kandosols and Chromosols). In >200-mm rainfall zone, which is important for Australian agriculture, the CaCO3-C stocks ranged from 60.7 to 2542 Mt at 0–0.3 m depth (dissolution zone), and from 260 to 15 660 Mt at 0–1.0 m depth. The combined CaCO3-C stocks in Vertosols, Kandosols and Chromosols were about 30% of those in Calcarosols. Total average CaCO3-C stocks in the dissolution zone represented 11–23% of the stocks present at 0–1.0 m depth, across the four soil types. These estimates provide a realistic picture of the current variation of CaCO3-C stocks in Australia while offering a baseline to estimate potential CO2 emission–sequestration through land-use changes for these soil types. In addition, we provide an overview of the uncertainties in accounting for CO2 emission from soil carbonate dissolution and major inorganic C transformations in soils as affected by land-use change and management practices, including liming of acidic soils and its secondary effects on the mobility of dissolved organic C. We also consider impacts of liming on mineralisation of the native soil C, and when these transformations should be considered a net atmospheric CO2 source or sink.

Corrosion Properties of Cold Spray Zn-25Al Coating in Marine Environment

Zn-25Al coatings were prepared by cold spray on mild carbon steel Q235. The coatings were studied by potentiodynamic polarization test, corrosion potentials and electrochemical impedance spectrum in natural seawater. The results show that the Ecorr of Zn-25Al coating is -1.01V (SCE) and the Ecorr of Q235 is -0.65V (SCE) at the beginning of the immersion. Self-corrosion potential of Zn-25Al coating is lower than that of Q235. The coatings turn to activity anodic dissolution zone when the potential reaches -1.05V. The coatings changes to passivation zone after the potential reaches -1.01V and the current intensities increase slightly with the potential increasing quickly. Zn-25Al coatings can provide lower protection potential and promising current to protect Q235 from corrosion.

Microstructure and Anti-Corrosion Properties of Arc-Sprayed Aluminum Coating in Splash Zone

Aluminum coatings were developed by arc spray on mild carbon steel Q235. Scanning electron microscopy detection shows that the coatings have good bonding with the substrate and have low porosity. The corrosion behaviors of the coatings in splash zone were studied. The results show that free corrosion potentials of aluminum coatings are much lower than that of Q235. Potentiodynamic polarization measurements reveal that the curves of aluminum coatings have activity anodic dissolution zone, passivation zone and super-passivation zone. Corrosion morphology and energy dispersive spectrometers show that Cl- can penetrate into the coatings and some of the substrate has been corroded. The arc spray Al-coating develops a film of corrosion products on the coating surface, which tend to seal the pores in the coatings. Arc spray aluminum coatings can protect the substrate from corrosion in splash zone.