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Different oil well tubes have different influences on CO2 corrosion.In order to optimize the materials with the best corrosion resistance to CO2, it is necessary to explore the corrosion of materials of conventional oil well tubes under different conditions.Therefore, taking the production well of CO2 composite flooding injection in Block nine six of Karamay oilfield as the research object, and simulating the actual service condition of oil well pipes, the corrosion weight loss experiments on N80, 3Cr, tungsten-plated heat insulation tube and P110 oil tube materials were carried out.The Potentiodynamic polarization curve and electrochemical impedance spectroscopy(EIS)were measured by three electrode system, scanning electron microscopy(SEM), energy dispersive spectroscopy(EDS)and X-ray diffraction(XRD)were used to observe the microstructure of corrosion products.Results showed that the corrosion rate of the four kinds of materials increased first and then decreased with the increase of temperature.With the increase of pressure, the corrosion rate of the four kinds of casing steels increased.The corrosion rate of tungsten-plated heat insulation tube and 3Cr was obviously lower than that of N80 and P110.According to the corrosion morphology, the four kinds of casing steels were corroded in varying degrees.The serious corrosion occurred on the surface of N80 and P110 whereas slight corrosion occurred on the surface of the tungsten-plated heat insulation tube and the 3Cr.Therefore, the corrosion law of four oil well tubes in CO2-driven environment was obtained, the suggestions on the design and selection of oil well tubes in CO2-driven environment were proposed to select the materials with the best corrosion resistance to CO2 optimally.

Lithium metal batteries have been considered as one of the most promising high-energy-density energy storage devices, however, the low Coulombic efficiency and uncontrolled dendrite growth seriously hinder their commercialization. In lithium metal batteries, the electrolytes would directly participate in the formation of solid electrolyte interface (SEI), which play important roles in affecting the lithium metal anode Coulombic efficiency and inhibiting the growth of lithium dendrites.In the traditional LiPF6 based ester electrolyte, lithium metal anode exhibits low Coulomb efficiency and serious lithium dendrites.In recent years, significant improvement has been achieved for the protection of lithium anode through manipulating the electrolyte additive, solvents, lithium salt and lithium salt concentration,etc. For examples,ether solvent presenting better compatibility with lithium metal was selected to reduce the side reactivity of electrolyte with lithium metal;varieties of additives were adopted to suppress the formation of lithium dendrites;high concentration electrolytes were employed to form stable SEI.In this paper, the growth principles of lithium dendrites, the research status of electrolytes chemistries for protection of lithium metal anode by means of solvents, lithium salts, additives and high concentration electrolytes strategies were reviewed and the advantages and limitations of various approaches were summarized.New insights on the development of electrolytes chemistries were also put forward to stimulate new strategies to face the subsequent challenges of lithium-metal batteries.

Based on the micro control body equations of multiphase flow for drilling operation, a model for compensation balance control of back pressure was proposed to adjust the throttle valve in real-time through compensation for gas slippage pressure drop, which can maintain balance between bottomhole pressure and formation pressure. Results show that the earlier the gas influx is detected, the easier the balance of bottomhole pressure can be achieved. The early detection of gas influx relies on the downhole detection tools. When gas influx occurs in the bottomhole, the throttle valve opening degree should be adjusted sharply to balance the formation pressure rapidly with the back pressure. Adjustment of the throttle valve opening degree depends on the change of pressure difference in the bottomhole. As the gas migrates upwards a-long the annulus, the throttle valve should be adjusted slightly in real-time to balance the pressure drop generated by gas slippage according to the compensation balance control model. When the gas flow away from the wellhead with the circulation, 0 gas flow appears in the annulus, and the throttle valve opening degree and back pressure tend to be stable. [ABSTRACT FROM AUTHOR]

According to the characteristic of axis symmetry of a tool joint and its combined load, a semi-analytical model was established, by which the 3-D FEA model of the tool joint can be changed into the pseudo-3D model, and the load, displacement and stiffness matrix of the tool joint under the combined load was obtained. Based on the theoretical research, an elastic plastic FEA software to compute the mechanical property of the tool joint was developed, which can calculate the mechanical property of the API tool joint under the combined load and can be used to develop a new type tool joint. The results of the FEA software is coincident with the experiment data. It can also be used to develop a new-type double shoulder tool joint. The result, indicates that the theoretial model and the software are reasonable. [ABSTRACT FROM AUTHOR]