Abstract Fracability is a property that indicates how easy reservoir rocks can be fractured in hydraulic fracturing operations. It is a key parameter for fracturing design and evaluation. In order to utilize continuous logging data to predict fracability, synchronous tests of dynamic and static mechanical parameters of rocks under different confining pressures were conducted on 13 tight sandstone samples derived from the central Junggar Basin, China. A modified formula between dynamic and static mechanical parameters was established. Fracability of the tight reservoir in the Junggar Basin was then evaluated based on brittleness index, fracture toughness, and fracability index. The effectiveness of fracturing was analyzed combined with the oil testing curve after hydraulic fracturing. The results show that: (1) The distribution of oil-bearing formations in the studied area coincides well with stratum of higher fracability index. (2) The critical fracability index is determined to be 0.3, three formations are selected as fracturing candidates, and a thin mudstone interbed is identified in the oil-bearing formation. (3) Well testing curve verifies the reliability of the fracability evaluation method and the accuracy of the modified formula between dynamic and static mechanical parameters. This study provides useful information for improving fracturing operations of tight oil and gas reservoirs.
Abstract In the sintering of iron ores, the partial substitution of anthracite for coke breeze has been considered to be an effective way of reducing pollutant emissions and production cost. In this study, the basic characteristics of anthracite and coke breeze were compared and the sintering performance at different substitution ratios of anthracite for coke breeze was investigated. The porosity of anthracite is lower than that of coke breeze, but its density and combustion reactivity are higher. The substitution of anthracite for coke breeze has no influence on the granulation effect of the sintering blend. As the anthracite proportion increased, the sintering speed and productivity increased and the sintering yield and tumbler index decreased. As the substitution ratio increased from 0 to 60%, the melting temperature duration and the melt quantity index decreased from 2.59 to 2.03 min and from 3218.28 to 2405.75 °C·min, respectively, leading to insufficient sintering mineralization and bad sintering indexes. For an anthracite substitution ratio of 40%, the sintering speed, sintering productivity, sintering yield and tumbler index were 22.34 mm min −1 , 1.49 t·(m 2 h) −1 , 71.65% and 63.59%, respectively, which entirely satisfies the production requirements. Furthermore, hematite (Fe 2 O 3 ), calcium ferrite (CaO–Fe 2 O 3 ), and compound calcium ferrite (CaO–SiO 2 –Fe 2 O 3 ) were the major mineral phases, which were embedded with an interwoven structure.
The amygdala is a critical brain region for auditory fear conditioning, which is a stressful condition for experimental rats. Adult neurogenesis in the dentate gyrus (DG) of the hippocampus, known to be sensitive to behavioral stress and treatment of the antidepressant fluoxetine (FLX), is involved in the formation of hippocampus-dependent memories. Here, we investigated whether neurogenesis also occurs in the amygdala and contributes to auditory fear memory. In rats showing persistent auditory fear memory following fear conditioning, we found that the survival of new-born cells and the number of new-born cells that differentiated into mature neurons labeled by BrdU and NeuN decreased in the amygdala, but the number of cells that developed into astrocytes labeled by BrdU and GFAP increased. Chronic pretreatment with FLX partially rescued the reduction in neurogenesis in the amygdala and slightly suppressed the maintenance of the long-lasting auditory fear memory 30 days after the fear conditioning. The present results suggest that adult neurogenesis in the amygdala is sensitive to antidepressant treatment and may weaken long-lasting auditory fear memory.
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