The demand for a new generation of high⁃energy⁃density batteries is increasingly urgent for the present market. As one of the most promising secondary batteries, the research on cathode materials has attracted much attention. Carbon materials with biomass as the precursor have been widely applied to the research of lithium⁃sulfur battery anode materials because of their wide range of sources, easy preparation, and high environmental friendliness. This paper introduces the current research status of cathode materials, the main methods of preparing biomass⁃based carbon materials and the effect of different factor of preparation on the biomass⁃derived carbon materials and on the performance of lithium⁃sulfur batteries. In addition, the paper also introduces some examples of biomass⁃derived carbon materials improved by current methods. Finally,the future development direction in lithium⁃sulfur battery cathode materials was proposed.
Cross⁃linked microcapsules were prepared by suspension polymerization with polystyrene as the wall material and 58# paraffin as the core material. The effects of polymerization temperature, initiator dosage, crosslinker type and core⁃wall ratio on microcapsules were investigated. The structure, morphology, heat storage performance and thermal stability of microcapsules were characterized by FT⁃IR, SEM, DSC and TG. The experimental results show that the microcapsules prepared by the polymerization temperature of 80 ℃ and the initiator AIBN 2% have good spherical shape. The microcapsules prepared by the cross⁃linking agent DVB have less clastic debris, no agglomeration and good thermal stability. The microcapsules prepared by the core wall ratio of 3∶1 have a phase transition enthalpy of 152.2 J/g, a core material content of 82.2%, and the best heat storage performance.
The Hβ zeolite was modified with different concentrations of citric acid. The textures of the modified Hβ zeolites were characterized by XRD and Ar adsorption, and the acid properties were characterized by NH3⁃TPD and Py⁃FTIR. In addition, the interaction between the pyridine molecules and the active constituent units of the Hβ zeolite was also analyzed by Py⁃FTIR. The results showed that several active sites, such as the Brønsted acid sites associated with the bridging hydroxyl groups (SiOHAl), the weak Lewis acid sites associated with EFAL hydroxyl groups and the strong Lewis acid sites associated with the three⁃coordinated Al hydroxyl species and AlO+ cations were existed in the Hβ zeolite. The synergistic effect between the EFAL and the adjacent bridging hydroxyl groups was found on the adsorption of pyridine. The pyridine molecule which adsorbed in the Lewis acid site and bonded with the adjacent B acid sites was less likely to desorb at high temperature. Pyridine molecules were preferentially adsorbed on the strong acidic bridging hydroxyls and defect sites associated with the three⁃coordinated Al hydroxyl species. It was only weakly interacted with EFAL hydroxyl groups. After citric acid treatment, EFAL hydroxyl groups were selectively removed while the framework aluminum was not severe damaged. The strong Lewis acid sites were preserved in the modified Hβ zeolite after citric acid treatment, and the strong Lewis acid sites may be related to AlO+ and the three⁃coordinated Al species of defect sites.
MB reservoir in H oilfield is mainly carbonate reservoir with pores,and water injection development is the main development method.The quality of injected water affects the effect of the oilfield development.The injected water quality standard of H oil field was studied,and the main control indexes such as the median particle size,suspended matter content,oil content and bacteria content of the injected water were obtained by core displacement experiment and dynamic corrosion experiment.The results showed that the median particle size index of suspended solids was less than or equal to 2.5 μm.Suspension content index was no more than 10 mg/L,oil content indexwas no more than 15 mg/L,the content of saprophyte (TGB) should be no more than 100 per mL,the content of iron bacteria (IB) should be no more than 10 per mL,and the content of SRB should be no more than 10 per mL.The results provide experimental basis for water injection quality standards in H oilfield,and also provide reference for research on water injection quality in similar areas.
The development of heavy oil field encounters such problems as steam channeling, water cut rising, and a large number of low production and low efficiency wells. In view of the existing problems, this paper proposed low temperature thermochemistry technique. The chemical system (sulfonate chemical system L⁃B) was developed independently and adapted to the offshore heavy oil field, which was used to synergize the thermal effect of low temperature steam, so as to reduce the cost and increase the efficiency of oil displacement and improve the efficiency of oil displacement. The static oil washing efficiency of the chemical system is 28.7%. The interfacial tension between crude oil and chemical system is 0.086 mN/m at 56 ℃, which is 99.3% lower than that between crude oil and formation water. The displacement efficiency can reach 65.00% at 120 ℃, which is 8.50% higher than that of steam flooding at the same temperature and achieved the steam injection effect at 200 ℃.After the application on an oilfield in Bohai Sea,the maximum daily oil production of a single well can reach 32 m3, increasing 52.4%. Low temperature thermochemical technique has certain guidance and reference significance for enhancing oil recovery of offshore heavy oil field.
At present, the polymer injection target of Lamadian oilfield has been shifted to the second type reservoir. Compared with the second type A reservoir,the second type B reservoir has serious heterogeneity and low permeability.For this reason,the study on the characteristics of polymer flooding seepage in the second type B reservoir is carried out.The results show that with the increase of core permeability,the iso⁃permeability point of polymer flooding relative permeability curve moves to the right and the span of two phases increases.Increasing the polymer molecular weight and the injection concentration can make the right end of the curve shift to the right.The polymer flooding resistance coefficient and residual resistance coefficient increase with the increasing of polymer solution concentration and molecular weight,while decrease with the increase of core permeability.There is a good correspondence between the polymer flooding resistance coefficient and the shunt rate.When the resistance coefficient reaches the peak,the shunt rate will reach the peak,and then the shunt rate of the high permeability layer will rise.The higher the molecular weight of the polymer, the higher the concentration of the solution,the greater the difference in permeability level,and the earlier the diversion rate of high permeability layer rises.
In order to improve the displacement effect of lh25 million macromolecule polymer, the oil displacement experiments of single slug and multiple slug were carried out. Through the experiments, the slug combination and injection method of 0.2、0.6、0.2 PV(1 800、1 500、1 200 mg/L）were determined in the test area of zone A. Compared with the conventional 25 million polymer block, the experimental area in zone A had the same increase rate of injection pressure, but the oil reservoir, especially the thin differential layer, had better injection and production capacity. Under the same PV injection, the water cut of the production well decreased more and the effect was faster, which was better than the injection of 25 million polymer blocks. There are differences in water cut rate, effective time and effective ratio of producing classified wells, and the indexes of type III wells are better than those of type I and II wells.
The particle size distribution of oil⁃in⁃water emulsion prepared under different conditions was studied by Malvin laser particle size analyzer. The results showed that the particle size of the oil⁃in⁃water emulsion decreased with the increase of the concentration of the active agent. When the concentration of the active agent reached 0.5%, the emulsion system was stable and the particle size changed little with the time of standing. With the addition of polymer, the particle size of oil⁃in⁃water emulsion increased first, then decreased and then increases. Within a certain shear rate range, the particle size of oil⁃in⁃water emulsion decreased with the increase of shear rate. When the shear rate exceeded 6 000 r/min, the particle size hardly changed with the shear rate. After shearing for a certain time, the change of emulsion particle size with shearing time was very small. At low shear rate, the emulsion system formed with short shear time was unstable.
In the late stage of high water cut in sandstone oilfield,the dominant flow field is seriously developed,which restricts the further improvement of water drive recovery.In this paper,AHP and fuzzy comprehensive evaluation combined with numerical simulation method are used to determine the weight of the influencing factors of the dominant flow field in the reservoir plane.The fuzzy comprehensive evaluation index (FCI) of the advantaged flow channel is obtained by fuzzy calculation of the constructed matrix,and the production and injection well with the advantaged flow channel is determined by the FCI value. Basing on the study of the advantaged flow channel,water injection volume of ineffective circulating injection wells is reduced and injection layer is adjusted to enlarge the water⁃flooding area and to achieve the aim of further tapping the remaining oil with the idea of fine injection and production adjustment.This method is adopted to determine the advantaged flow channel of a block of V Oilfield.Among them,seven production and injection well pairs exist in advantaged flow channel area,five production and injection well pairs exist in much more advantaged flow channel areas.The comprehensive water cut in V Oilfield is reduced by 1.1%,the cumulative crude oil yield rises up to 2.2×104 t,achieving a good effect for taping reminding oil and controlling water cut by the deep profile and periodic water injection in injection well with the production well shutting off adjustment for 12 well groups which is in advantaged flow channel areas.
Paleokarstification is one of the key factors for the formation of marine carbonate reservoirs in Tazhong and north Tarim basin. The interlayer karstification in the middle Tarim basin is quite different from that in the weathering crust in the north Tarim basin. In order to further identify the development pattern of interlayer karst in Tarim basin and analyze the development characteristics of paleokarst. On the basis of previous studies, the stratigraphic loss between the ordovician and overlying strata is clarified. The field profile and typical characteristics of the traditional weathering crust karst and interlayer karst are investigated through field investigation and laboratory core experiment analysis. The results show that the interlayer karst has obvious vertical zoning, and the continuity of karst caves is poor from top to bottom, which are nodular loam zone (residual zone), weathered fracture zone (seepage zone) and dissolution cave zone (subsurface zone). It is also a multi⁃stage cycle, forming interlayer karst development zone of tens of meters, which is a favorable area for oil and gas enrichment. It is considered that the interlayer karstic reservoir in Tarim basin is the result of the superimposed transformation of multi stage karstification.
It is always the key point in the field of oilfield development to study the oil circulation condition and percolation law in reservoirs.Based on the percolation theory,a three⁃dimensional percolation model is established by numerical simulation method,which can simulate the distribution of cracked joints,percolation laws,percolation thresholds of reservoir rocks and determine whether they are permeable.The results show that when the connectivity probability increases from 0,the total number of clusters increases.When the connectivity probability increases to 0.17,the total number of clusters begins to decreases.When the connectivity probability is small,the percolation probability increases slowly with the increase of the connectivity probability.When the connectivity probability exceeds the first critical value,the growth rate of the percolation probability suddenly increases.When the connectivity probability exceeds the second critical value,the percolation probability begins to slowly increase again and eventually approaches 1.The seepage cluster can accurately determine whether the porous medium is permeable and accurately capture the percolation threshold.The size of the percolation threshold is related to the size and shape of the medium.There is no obvious regularity between the maximum cluster size and the average cluster size,the maximum cluster size and the total number of clusters.It is concluded that this three⁃dimensional percolation model can simulate the long⁃range coupling mutation caused by the change of connectivity probability in porous media,which can be used to simulate the permeability and percolation law of rock.
Massive electric charges will be generated due to the contact of oils flowing in the non⁃metallic pipeline with the inner wall of the pipeline. Excessive charge gathering discharge will cause spark discharge, which will lead to perforation of the pipe wall and fire, and seriously affect the normal production. Through analysis on the cause of static electricity and influencing factors, it is easy to find that the electrification rate is influenced by the oil flow rate, temperature, water content, pipe material and roughness. The results show that there is a positive correlation between the electrification rate and the oil flow rate, between the electrification rate and the pipe roughness; the rise of oil temperature adversely affects the accumulation of oil static; the electrification rate grows with the moisture content in a certain content range, and decreases with the increase of water content beyond the range; in combination with the existing experiment data, an oil flow⁃induced static model is built.
In order to ensure the safety production of offshore heavy oil thermal recovery platform and establish the mathematical model of thermal recovery blowoff diffusion of offshore platform, ANSYS Fluent software was used to simulate the gas diffusion in the process of steam huff and puff thermal recovery, quantify the impact of thermal recovery blowoff process on the platform, and provide guidance for platform general layout. Taking LvDa 21⁃2 oil field as an example, due to the increase of methane content in the later stage of blowout, the slow diffusion rate caused by the decrease of blowoff volume, blowoff was easy to accumulate in the steam boiler and other higher equipment, thus causing potential safety hazards. By optimizing parameters of cold vent system and equipment layout, the impact of blowout on safe operation was lowered to the utmost and platform area was cut down by 5.9%. The study could provide reference for safety design of offshore thermal discovery platform.
Based on OpenFoam open source software,this paper builds three⁃dimensional flow model under VOF method.Stratified flow,wave flow,bubble flow,plug flow and slug flow with different gas⁃liquid velocities in horizontal pipe are simulated and compared with Mandhane flow pattern.The simulation results of horizontal pipe with diameter of 0.05 m and length of 16 m are consistent with theoretical and experimental results,which verify the validity of the model.The model is used to study the process of plugging,growth and evolution of slug flow.The characteristics of interfacial wave during plugging and the characteristics of liquid slug motion under different gas⁃liquid velocity differences are obtained.The phenomenon of liquid slug head projection and the wave⁃like motion of liquid slug are found.
Due to the influence of its own parameters, conventional sand⁃washing tools can not meet the needs of the field. Based on the theoretical study of sand⁃washing mechanism, a complete set of sand⁃washing tools is designed. Through calculation, laboratory and field operation, it is proved that the non⁃metallic continuous pipe horizontal well sand⁃washing tool can solve the sand⁃washing problem of small displacement surface equipment in horizontal section, realize the functions of adjustable rotational speed, hydraulic propulsion, turbulent sand⁃carrying and pulsed jet, solve the technical problems of non⁃metallic pipe matching sand⁃washing tool, and obtain certain economic and social benefits.
The energy consumption of oilfield fuel oil heating furnaces is high, and the sulfur dioxide, nitrogen oxides and soot in the flue gas emitted seriously exceed the standard, causing serious environmental pollution. So it is urgent to replace the oilfield heating furnace. The technology principle, energy consumption calculation, equipment characteristics and feasibility of replacing oil field fuel oil heating furnace of air source heat pump and sewage source heat pump are studied, and the benefits of two heat pump technologies replacing oil field fuel oil heating furnace are analyzed. Through research, it is concluded that the air source heat pump and sewage source heat pump technology are effective ways to replace oil in the oil field heating furnace; by using air source heat pump and sewage source heat pump to replace the fuel oil heating furnace, the operating costs can be reduced by 30% and 45% respectively, and the carbon emissions can be reduced by 60% and 75% respectively. By replacing the fuel oil of the heating furnace, not only can you obtain considerable economic benefits, but you can also effectively reduce the emissions of sulfur dioxide, nitrogen oxides, and smoke.
