砂岩气藏基质酸化残液返排影响因素研究

酸化后残液返排过程涉及气液两相渗流、气窜、液锁、气驱水等物理现象,因此影响残液返排效果的因素很多。在模拟基质酸化过程单一影响因素的基础上,进行了多因素综合研究。研究结果表明:相同条件下,渗透率越低的储层其返排效果越差;随工作液黏度增大,返排率呈下降趋势,当黏度增加到一定程度后,返排率变化不大;一定界面张力范围内,界面张力对返排率影响不大,界面张力增加,返排率只有小幅度减小。而各参数组合k/(δμ)值增大,返排率增大,且变化率由小变大。另外,酸化半径越小,越容易达到极限返排率,并且最终返排率相对较高。当酸化半径达到一定值后,最终返排率变化不大。实验结果显示不同酸化半径的最终返排率取决于储层物性。     

Electronic structures and optical properties of Nb-doped SrTiO3 from first principles

The n-type Nb-doped SrTiO₃ with different doping concentrations were studied by first principles calculations. The effects of Nb concentration on the formation enthalpy, electronic structure and optical property were investigated. Results show that Nb preferentially enters the Ti site in SrTiO₃, which is in good agreement with the experimental observation. The Fermi level of Nb-doped SrTiO₃ moves into the bottom of the conduction band, and the system becomes an n-type semiconductor. The effect of Nb-doping concentration on the conductivity was discussed from the microscopic point of view. Furthermore, the 1.11 at% Nb-doped SrTiO₃ shows strong absorption in the visible light and becomes a very useful material for photo-catalytic activity. The 1.67 at% and 2.5 at% Nb-doped models will be potential transparent conductive materials.     

Nb掺杂浓度对SrTiO3的电子结构和光学性能的影响

用第一性原理计算不同Nb掺杂浓度的n型Nb掺杂SrTiO3,研究了Nb掺杂浓度对SrTiO3的形成焓、电子结构和光学性能的影响.在Nb掺杂SrTiO3中Nb替位Ti原子,与实验结果一致.Nb掺杂SrTiO3的费米能级进入导带底部,Nb掺杂SrTiO3呈现n型半导体特征.从微观角度分析了Nb掺杂浓度对导电性的影响,1.11at％ Nb掺杂SrTiO3在可见光范围有强吸收,是一种有潜在应用的光催化材料;而1.67at％和2.5at％Nb掺杂SrTiO3是潜在的透明导电材料.