ALBERT

Description: 〈span〉〈div〉ABSTRACT〈/div〉Calcite cementation has been identified as an active process in the Upper Triassic Yanchang Formation throughout its burial history and as a major diagenetic factor causing strong reservoir heterogeneities. The origins of calcite cements and their relevance to reservoir heterogeneities were investigated using a suite of petrographic and geochemical methods, including optical microscopy with fluorescence and cathodoluminescence, scanning and backscattered electron microscopy with energy-dispersive spectrometry, x-ray diffraction, x-ray fluorescence, electron probe microanalysis, quantitative evaluation of minerals by scanning electron microscopy, fluid inclusion analysis, and carbon and oxygen stable isotope analyses. The sandstones are compositionally immature with relatively high amounts of volcanic rock fragments. The two generations of calcite cements are Ca-I and Ca-II. The Ca-I calcites are distributed along the interface of sandstone and mudstone units and were formed during the Late Triassic to Early Jurassic at formation temperatures of approximately 90°C. The Ca-II calcite mainly developed in the lower part of the fining-upward sandstone units and was formed in the Late Jurassic at higher temperatures of approximately 110°C. The origins of calcite cements were constrained by geochemical and isotope measurements, fluid inclusion homogenization temperature, and in situ element analysis. The Ca-I calcite cement originated from dissolution of the lacustrine depositional carbonates in the interbedded mudstones and reprecipitation in the adjacent sandstones. The Ca-II calcite was mainly related to organic matter decarboxylation, with Ca〈sup〉2+〈/sup〉 having been provided internally by volcanic fragment alteration and plagioclase dissolution. Calcite cementation had caused strong reservoir heterogeneities in the Yanchang Formation tight sandstones. The Ca-I calcite cementation destroyed reservoir properties along the interface of sandstones and mudstones. The lower parts of the fining-upward sandstone units were tightly cemented by Ca-II calcite, although they originally had high porosity and permeability. The middle–upper parts of the fining-upward sandstone units contain less calcite cements and thus have better preserved reservoir pores because of oil emplacement inhibiting the calcite cementation processes.〈/span〉

Description: The influence of blade angle distribution along leading edge on cavitation performance of centrifugal pumps is analysed in the present paper. Three sets of blade angle distribution along leading edge for three blade inlet angles are chosen to design nine centrifugal pump impellers. The RNG k- ##IMG## [http://ej.iop.org/icons/Entities/epsilon.gif] {epsilon} turbulence model and the Zwart-Gerber-Belamri cavitation model are employed to simulate the cavitation flows in centrifugal pumps with different impellers and the same volute. The numerical results are compared with the experimental data, and the comparison proves that the numerical simulation can accurately predict the cavitation performance of centrifugal pumps. On the basis of the numerical simulations, the pump head variations with pump inlet pressure, and the flow details in centrifugal pump are revealed to demonstrate the influence of blade an...

Description: As a kind of widely used device in pipe system for pressure and flow rate regulating, the valve would experience cavitation in the case when a sharp pressure drop occurs, which will induce the energy loss, noise and vibration of pipeline system, and even operational accidents. The experiment on flow resistance coefficient of a DN600 pressure-regulating valve under operation conditions from 0% to 100% openings is conducted. Based on the RNG k-e turbulence model and the Rayleigh-Plesset cavitation equation, a set of computational model is developed to simulate the turbulent flow in the valve under operational conditions from 0% to 100% openings. The computational results of flow resistance coefficient are compared to the experimental data. And the numerical simulation is employed to predict the cavitation performance of the valve at different inlet flow conditions. The transient cavitating flow is calculated to reveal the time evolution of cavitation in the valve.

Description: During casting of steel ingots, the inclusions such as oxide, sulfide will inevitably exist in the melt. These inclusions will flow upward together with light solutes during solidification due to their lower density relative to the steel melt, which therefore causes impacts on the thermo-solutal convection in the melt and final solute distribution. Hence, a macrosegregation model that considers the effects of inclusions on melt flow in the mushy zone is established. Of the new model two important parameters, the inclusion capturing probability by solid, k p , and the original volume fraction, n 0 , are systematically studied in terms of simulations, which shows that decreasing k p or increasing n 0 leads to stronger ascending flow in the melt. And then as a validation example, the model was used to predict the macrosegregation in a 3.3-ton steel ingot. The prediction demonstrates that with consideration of inclusio...

Description: The influence of prewhirl regulation by inlet guide vanes (IGVs) on cavitation performance and flow characteristic in a centrifugal pump is investigated. At the impeller inlet, the streamlines are regulated by the IGVs, and the axial velocity distribution is also influenced by the IGVs. Due to the total pressure loss on the IGVs, the cavitation performance of the centrifugal pump degrades. The cavitation area in impeller with IGVs is larger than one without IGVs. The specify values of total pressure loss between the suction pipe inlet and impeller inlet for three cavitation conditions show that the IGVs will generate additional pressure loss, which is related to the IGVs angles and cavitation conditions.

Description: This paper discusses a new method for determining the iron content in Chinese fir leaves and roots using a SmartChem200 automatic chemical analyzer. With a pH value of 4-5, Fe 3 + was reduced to Fe 2 + by hydroxylamine hydrochloride, and Fe 2 + and 1,10-phenanthrolinemonohydrate generated an orange complex. The iron content was calculated based on the absorbance measured at a wavelength of 510 nm. The absorbance is directly proportional to the Fe 2 + content within a certain concentration range of Fe 2 +. The absorbance had a good linear relationship with the Fe 2 + content in the range of 0.01 mgL −1 to 5 mgL −1 ; the linear regression equation of the standard curve was Y=0.0632*X-0.00002, and the correlation coefficient was 1.0000. The method is convenient and rapid, and the experimental results were reliable.

Description: The purpose of this work was to study the depositional mechanisms and significance of the Longmaxi shale in the Sichuan Basin in southern China. Seven lithofacies were identified based on the detailed observation of outcrops and cores using petrographic and scanning electron microscope examination of thin sections and other data analyses: (1) laminated calcareous mudstone, (2) laminated carbonaceous mudstone, (3) laminated silty mudstone, (4) laminated claystone, (5) laminated siliceous shale, (6) siltstone, and (7) massive mudstone. The laminated mudstone and laminated claystone originated from suspension deposition, and siliceous shale is associated with ocean upwelling, whereas massive mudstone and siltstone were primarily deposited by turbidity currents. The depositional mechanisms have a great effect on the source rock and reservoir properties. Suspension deposition near oceanic upwelling zones can provide favorable conditions for the production and preservation of organic matter and are thus conducive to the formation of high-quality source rocks (total organic carbon content up to 5.4%). The reservoir storage spaces are primarily interlaminated fractures and organic pores with good physical reservoir properties (high porosity, permeability, and brittle mineral content). Turbidity currents may carry a large quantity of oxygen to the seafloor, resulting in the oxidation of organic matter, which is unfavorable for its preservation. The lithofacies formed by turbidity currents have relatively low total organic carbon contents (average: 〈1%). Structural fractures and intergranular pores are the primary storage spaces that are present in the reservoir. In summary, organic-rich shale and siliceous shale that was deposited from suspension near upwelling zones are key exploration targets for shale oil and gas. The widely distributed, multilayer, tight sandstone is important in the exploration for tight oil. A better understanding of the deposition mechanism and its effect on oil reservoirs may assist in identification of favorable areas for exploration.

Description: Three nutrient addition experiments were conducted to induce green tides of Ulva prolifera from April to August in 2016 in the coastal waters of Qingdao, China. Photosynthetic activity (F v /F m ), biomass, nutrients and temperature were measured.We found that F v /F m of U. prolifera increased to the maximum about 0.7 ∼ 0.75 under favorable environment, and declined significantly when the growth of U. prolifera was limited by nutrient and temperature. In Addition, the results showed that F v /F m increased to the maximum prior to occurrence of green tide and fell significantly before green tide dissipated. F v /F m can be used to predict the outbreak and dissipation of green tides.

Description: A light ray tracing model and a heat transfer model were built to analyse the heat flux distribution and heat transfer in a 1m cavity receiver tube with Parabolic Trough Collectors as the concentrator. The numerical methods were used to simulate the thermal stress and deformation of the receiver tube. The temperature fields of the receiver tube and the thermal stress distribution in the steel tube at the cross section and along the fluid flowing direction were presented. It is obtained from this study that non-uniform heat flux distribution is absorbed at the receiver tube outer surface due to the structure of the cavity receiver tube. Temperature fields in the steel receiver tube at the inlet and the outlet match well with the incident solar radiation. An eccentric circle temperature gradient is observed at cross section of the outlet fluid. The equivalent stress is a complex result of solar heating flux, energy transfer inside the PTC and the fluid and steel characteristics. H...

Description: The geochemistry and reservoir characteristics of the lacustrine shale in the Eocene Dongying depression are described in detail based on thin-section and field-emission–scanning electron microscope observations of well cores combined with x-ray diffraction, physical property testing, and geochemical indicators. The Eocene Shahejie (Es) Formation Es4s–Es3x shale member is predominantly carbonate, clay minerals, and quartz. Six lithofacies were identified: (1) laminated limestone (organic-rich laminated limestone and organic-poor laminated limestone), (2) laminated marl, (3) laminated calcareous mudstone, (4) laminated dolomite mudstone, (5) laminated gypsum mudstone, and (6) massive mudstone. The Es4s–Es3x shale samples from three cored wells had total organic carbon (TOC) contents in the range of 0.58 to 11.4 wt. %, with an average of 3.17 wt. %. The hydrocarbon generation potential (free hydrocarbons [S1] + the hydrocarbons cracked from kerogen [S2]) values range from 2.53 to 87.68 mg/g, with an average of 24.19 mg/g. The Es4s–Es3x shale of the Dongying depression has a high organic-matter content with very good or excellent hydrocarbon generation potential. The organic maceral composition is predominantly sapropelinite (up to 95%). The hydrogen index (being S2/TOC) versus the maximum yield temperature of pyrolysate ( T max ) indicates that the organic matter is predominantly type I kerogen, which contains a high proportion of convertible organic carbon. The Es4s–Es3x shale is thermally mature and within the oil window, with the vitrinite reflectance values ranging from 0.46% to 0.74% and the T max value ranging from 413°C to 450°C, with the average being 442°C. The shale contains interparticle pores, organic-matter pores, dissolution pores, intracrystalline pores, interlaminar fractures, tectonic fractures, and abnormal-pressure fractures. The primary matrix pore storage is secondary recrystallized intercrystal pores and dissolution pores that formed during thermal maturation of organic matter. The TOC content and effective thickness of the organic-rich shales are the primary factors for hydrocarbon generation. The reservoir capacity is related to the scale, abundance, and connectivity of pore spaces, which are controlled by the characteristics of the lithofacies, mineral composition, TOC content, and microfractures.