Two?dimensional transition metal carbides and nitrides (MXenes) have become a high?profile material with a wide range of application prospects due to their efficient adsorption and catalytic properties,wide optical absorption range,and excellent conductivity.Ni?doped Nb₂C material has positive photocatalytic properties.To explore the intrinsic mechanism of photocatalytic property improvement by Ni?doped Nb₂C,the electronic structure properties of Nb₂C and its Ni?functionalized form(i.e.,Ni?Nb₂C) and their adsorption properties for CO₂ gas molecule by using the density functional theory (DFT) were investigated.The results show that the replacement of an Nb atom by a Ni atom makes the charge density around the Ni atom increase and further results in a redistribution of the charge density of the substrate,which leads to an improved electronic environment for catalyzing CO₂ and improves the photocatalytic property for CO₂.

Three⁃dimensional finite element model of buried casing is established using ANSYS software. Through laboratory tests, the relationship between the stress within the center of buried casing and the load on the ground, and the stress distribution in the direction of casing length under different loads is analyzed,respectively. Finally, a three⁃dimensional finite element model is established according to several casing cases in an oilfield. The magnitude of the load on the ground is obtained when the casing reaches the yield strength. The research results can provide a certain reference for the safety protection of pipelines and casing.

Under different temperature and different stress conditions, the creep experiment of polyurethane foam was carried out, and the creep constitutive equation of polyurethane foam under high temperature was obtained by fitting the obtained creeptime curve with Modified Time Harding model. Comparing the steady state creep rate fitted by model with the steady state creep rate measured by experiment, it is found that the creep property of polyurethane polymer has an important relationship with temperature and stress level. As the temperature and the stress level increases, the creep behavior of the material is more pronounced. The creep curve at high temperature is divided into two phases. In the first phase, the creep rate is larger and the creep rate gradually decreases with time. In the second phase, the creep rate is small and remains basically constant. Modified Time Harding model can better predict the creep rate of polyurethane materials under high temperature conditions.

Locating the combustion front timely is helpful to production control. The prediction methods of combustion front used in field were researched, then a set of application method specific to reservoirs with different feature was obtained. Infrared photography was suitable for shallow layer reservoirs, and direct testing method using thermometric component was suitable for reservoirs with intensive observation well and production well. Method combining production performance and material balance was suitable for homogeneous reservoirs with regular well pattern, and method combining tracer monitoring and production performance was suitable for heterogeneous reservoirs or reservoirs with irregular well pattern. The pressure drop test method was so complicated that it needed further study. At last the suggestions were proposed that on the basis of geological screening in advance, the aim of "less air injection and more oil production" should be achieved, besides, the management of production well should be strengthened by combining analysis of production performance, so that the combustion front could be moving forward evenly and steadily.

Active fractions were extracted from series petroleum sulfonates by extraction and back－extraction method，the equivalent weight distribution of them were analyzed by ESI－MS spectrum and the average equivalent weight could be calculated，as well as gas－phase osmotic method was conducted to determine the average relative molecule mass of their oleophylic groups which were obtained by desulfonation．The interfacial tension of oil／water system respectively consisted of series petroleum sulfonates or their active fractions were measured by rotated dropping method．The results show that the difference of the equivalent weight distribution mainly existed in the low and high equivalent weight section，and the one which has properly hydrophile－lipophile balance for the complementation of molecule structure benefiting from broad equivalent molecule weight distribution，its oil／water system can obtain the ultralow interfacial tension．