For achieving the sustainable development goals, green development has been raised to a high position for cities in China. The economic development in Northwest China is slow, the ecological environment is fragile, and the mineral resources are rich. Only through green development can we realize the comprehensive income of regional production development, rich life, and good ecology. This paper measures the green development efficiency of 30 prefecture-level cities in Northwest China by using DEA-SBM model of unexpected output, explores the differences and causes of green development efficiency from the perspective of time and space through convergence coefficient, coordination matrix, GIS, and other methods, and empirically tests the impact of industrial structure, technological progress, and other driving factors on green development efficiency by using panel Tobit model. The results show that, on the whole, the efficiency of green development in Northwest China is low, path dependence is serious and unbalanced, the coordinated development effect of different regions is weak, and the spillover effect of core urban agglomerations has not been effectively exerted; from the perspective of driving factors, economic development, population density, traffic situation, and education investment can significantly improve the efficiency of urban green development, and the second is that the proportion of industries significantly hinders the improvement of green development efficiency, while the impact of scientific and technological innovation is not significant. Based on the empirical results, this paper believes that the harmonious development of natural environment and economic society can be realized only by improving the coordinated development effect among cities, implementing the optimization and upgrading of industrial structure, introducing excellent talents, and promoting the technological upgrading.

A physical modeling system of long slim tube was established. Several pressure measuring and sampling points were laid out at different positions along the tube. Through real-time measurements of pressures and chemical concentrations at different points, the mass transfer and chemical concentration of ASP flooding in porous media are studied. The concentration of chemicals declines gradually during the fluid flow from the inlet to the outlet of the model. The concentration increases in the front edge of the slug faster than the concentration decreases in the rear edge of the slug. The concentration variation of the chemicals is an asymmetrical and offset process. The order of motion velocities of the chemicals from fast to slow is polymer, alkali and surfactant. The motion lag and comprehensive diffusion are strong in the vicinity of the inlet, the motion velocities of the chemicals are high, the difference of flow velocities among the three chemicals is significant and the chromatographic separation of the chemicals is obvious. In the area near the outlet, the comprehensive diffusion and motion lag become weak, the concentrations of the chemicals decrease, the motion velocities of the chemicals are slow, the difference among the motion velocities of the chemicals becomes small, the chromatographic separation is not obvious, the adsorption and retention of chemicals gradually increase as the chemical slug moves further along the tube, the adsorption and retention of polymer is the most serious.ASP flooding, concentration of chemicals, motion velocity, chromatographic separation, adsorption and retentionThe synergic effect of alkali, surfactant and polymer is applied in ASP flooding. Oil recovery is significantly enhanced by improving displacing efficiency and sweeping efficiency. The research on the mechanism of enhanced oil recovery has been widely emphasized by researchers in the world [1] . ASP flooding is a very complex physical-chemical process, the fluid flow and mass transfer of chemicals in porous media are two major theoretical problems. In the past, the fluid flow mechanism of ASP flooding in porous media, including microscopic fluid flow mechanism and macroscopic fluid flow mechanism, has been studied a lot, and remarkable results have been achieved, the theoretical foundation has been setup for oilfield application [2][3][4][5][6] . In recent years, researches on the mass transfer of ASP flooding have been begun to study, such as, chromatographic separation [7] , diffusion and dispersion [8] , mass transfer of chemicals [9] , and so on.Since the mass transfer of ASP flooding is very complex and involves many physical and chemical phenomena. There exist many problems which need to be studied in detail, and only in this way can the large-scale on-site application of the ASP flooding technology be promoted in the oil fields.The difference of concentrations between ASP agents and formation water causes diffusion and dispersion in the process of flooding and results in the concentration decreasing of chemi...