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| 1 | Experimental study on the effects of drying methods on the stabilities of lignite显示文摘The drying processes are always applied prior to the transportation or utilization of lignite, and result in notable changes in the stabilities of lignite. In this paper, the study on the effects of nitrogen and MTE drying process on the physico-chemical properties and stabilities of Zhaotong lignite was carried out. The briquettes produced by MTE drying in this study were 150 mm in dimension, and so had a much larger particle size than nitrogendried samples. Nitrogen adsorption, mercury intrusion porosimetry and scanning electron microscopy all suggested that drying was accompanied by the transformation of larger pores into smaller ones. Compared to nitrogen drying, the pore structures could be stabilized by the MTE process. The soluble salts were removed during MTE drying which resulted in the decrease in ash and the concentrations of some of the major metals.The removal of water enhanced the hydrophilicity of nitrogen dried samples, but did not affect the hydrophilicity of MTE dried samples. The moisture holding capacity of MTE dried samples reduced faster than nitrogen dried samples with the decrease of residual moisture content. The moisture readsorption processes of MTE dried samples were strongly inhibited due to the much larger particle size of sample produced by MTE drying than nitrogen drying. The susceptibility to spontaneous combustion, indicated by cross point temperature and self-heating tests, of nitrogen and MTE dried samples increased with the decrease of residual moisture content. The MTE dried samples are more liable to spontaneous combustion than nitrogen dried samples with the same residual moisture and particle size. However, the larger particle size of the MTE product made it more stable with respect to spontaneous combustion and also moisture readsorption. | Yixin Zhang Jixiang Dong Fanhui Guo Xiaokai Chen Jianjun Wu Zhenyong Miao | 2018 | Chinese Journal of Chemical Engineering2018,26,7: | 4 |
| 2 | An optimal fracture geometry design method of fractured horizontal wells in heterogeneous tight gas reservoirs显示文摘In this work, the unified fracture design(UFD) is extended for the first time to the fractured horizontal wells in heterogeneous closed box-shaped tight gas reservoirs. Utilizing the direct boundary element method and influence function, the dimensionless fracture productivity index is obtained and expressed in the function of proppant volume and fracture geometry at the pseudo-steady state. With the iterative method, the effectively propped permeability, kfe, is corrected using the in-situ Reynolds number, N_(Re). The goal of this paper is to present a new UFD extension to design the proppant volume and the optimal fracture geometry. The results show that there exists an optimal proppant volume for a certain reservoir. The small aspect ratio(y_e/x_e) and high permeability reservoirs need short and wide fractures to diminish the non-Darcy effect. On the contrary, long and narrow fractures are required for the large aspect ratio and low permeability reservoirs. A small proppant volume is prone to creating long fractures, while a relatively large proppant volume creates wide fractures. The new extension can be used to evaluate the previous fracture parameters and design the following fracture parameters of the fractured horizontal well in heterogeneous tight gas reservoirs, with the non-Darcy effect taken into account. | ZENG FanHui KE YuBiao GUO JianChun | 2016 | Science China(Technological Sciences)2016,59,2: | 3 |
| 3 | Numerical simulation of 23 June 2016 Yancheng City EF4 tornadic supercell and analysis of lightning activity显示文摘Based on the Weather Research Forecasting(WRF) model that features charging and discharging parameterization,relationships between tornado, hail and lightning were investigated for a tornado-producing(EF4 intensity) supercell thunderstorm over Yancheng City in Jiangsu Province, China, on 23 June 2016. Based on a sounding at 0800, there was a low lifting condensation level, substantial convective available potential energy(CAPE), and strong vertical wind shear near Yancheng City, which promote supercell development. At 1400, observations revealed that hail production and a dramatic increase of positive cloud-to-ground flash rates occurred simultaneously, maximizing five minutes later. The tornado occurred 30 min after the hail production. The time of minimum positive cloud-to-ground flash rates was 15 min later. The simulation indicated that the tornadic supercell moved eastward and that positive cloud-to-ground flash rates increased dramatically at 1400, the same as observed, but their maximum was 5 min later than observed. The simulated updraft volume peaked at 1425 and the simulated downdraft volume maximized5 min later, when the mesocyclone formed. Simulated reflectivities showed no hook echo and horizontal winds for different height at mid-low levels had a different cyclonic shear at 1430, favorable to mesocyclone formation. Based on the simulated results,the region of positively charged graupel ascended resulting from the region of high liquid water content was lifted by the strong updraft, forming a mid-level strong positive charge region. A lower negative charge region formed by the inductive charging mechanism of collisions between graupel and droplets at the bottom of the cloud, conducive to positive cloud-to-ground flashes. | GUO FengXia LI Yang HUANG ZhaoChu WANG ManFei ZENG FanHui LIAN ChunHao MU YiJun | 2017 | Science China Earth Sciences2017,60,12: | 3 |
| 4 | Mechanisms of shale hydration and water block removal显示文摘Shale samples of Silurian Longmaxi Formation in the Changning area of the Sichuan Basin, SW China, were selected to carry out scanning electron microscopy, CT imaging, high-pressure mercury injection, low-temperature nitrogen adsorption and imbibition experiments to compare the hydration characteristics of montmorillonite and illite, analyze the main factors affecting the water block removal of shale, and reveal the mechanisms of pore structure evolution during shale hydration. The hydration characteristics of shale are closely related to the composition of clay minerals, the shale with high illite content is not susceptible to hydration and thus has limited room for pore structure improvement;the shale with high montmorillonite is susceptible to hydration expansion and thus has higher potential of pore structure improvement by stimulation;the shale with high illite content has stronger imbibition in the initial stage, but insufficient diffusion ability, and thus is likely to have water block;the shale with high montmorillonite content has weaker imbibition in the initial stage but better water diffusion, so water blocking in this kind of shale can be removed to some degree;the shale reservoir has an optimal hydration time, when it is best in physical properties, but hydration time too long would cause damage to the reservoir, and the shale with high illite content has a shorter optimal hydration time;inorganic cations can inhibit the hydration of clay minerals and have stronger inhibition to illite expansion, especially K^(+);for the reservoir with high content of montmorillonite, the cation content of fracturing fluid can be lowered to promote the shale hydration;fracturing fluid with high K^(+) content can be injected into reservoirs with high illite content to suppress hydration. | ZENG Fanhui ZHANG Qiang GUO Jianchun ZENG Bo ZHANG Yu HE Songgen | 2021 | Petroleum Exploration and Development2021,48,3: | 2 |
| 5 | Optimization of refracturing timing for horizontal wells in tight oil reservoirs: A case study of Cretaceous Qingshankou Formation, Songliao Basin, NE China显示文摘Tight oil reservoirs in Songliao Basin were taken as subjects and a novel idealized refracturing well concept was proposed by considering the special parameters of volume fracturing horizontal wells, the refracturing potential of candidate wells were graded and prioritized, and a production prediction model of refracturing considering the stress sensitivity was established using numerical simulation method to sort out the optimal refracturing method and timing. The simulations show that: with the same perforation clusters, the order of fracturing technologies with contribution to productivity from big to small is refracturing between existent fractured sections, orientation diversion inside fractures, extended refracturing, refracturing of existent fractures; and the later the refracturing timing, the shorter the effective time. Based on this, the prediction model of breakdown pressure considering the variation of formation pressure was used to find out the variation pattern of breakdown pressure of different positions at different production time. Through the classification of the breakdown pressure, the times of temporary plugging and diverting and the amount of temporary plugging agent were determined under the optimal refracturing timing. Daily oil production per well increased from 2.3 t/d to 16.5 t/d in the field test. The research results provide important reference for refracturing optimization design of similar tight oil reservoirs. | GUO Jianchun TAO Liang ZENG Fanhui | 2019 | Petroleum Exploration and Development2019,46,1: | 0 |
| 6 | Synthesis of zeolite Na-P1 from coal fly ash produced by gasification and its application as adsorbent for removal of Cr(Ⅵ) from water显示文摘The coal fly ash produced by gasification is estimated to be over 80 million ton per year in China by 2021.It has mainly been disposed as solid waste by landfill.There is lack of study focused on its utilization.In this paper,the coal fly ash produced by gasification was at first analyzed and then applied to synthesize zeolite as an adsorbent.The effects of synthesis conditions on the cation exchange capacity(CEC)of zeolite were investigated.The results from X-ray diffraction and scanning electron microscope indicated that the crystallinity of the synthesized zeolite is the most important factor to affect the CEC.When the synthesized zeolite with the highest CEC(275.5 meq/100 g)was used for the adsorption of Cr(Ⅵ) from aqueous solution,the maximum adsorption capacity for Cr(Ⅵ) was found to be 17.924 mg/g.The effects of pH,contact time and initial concentration on the adsorption of Cr(Ⅵ) were also investigated.The adsorption kinetics and isotherms can be well described by the pseudo-secondorder model and Langmuir isotherm model,respectively. | Yixin Zhang Lu Zhou Liqing Chen Yang Guo Fanhui Guo Jianjun Wu Baiqian Dai | 2021 | Frontiers of Chemical Science and Engineering2021,15,3: | 0 |