The prediction and analysis of natural gas demand can provide help for reasonable production scheduling and resource allocation, and then bring economic benefits to the network companies. This paper discusses the current research progress of natural gas demand prediction and other energy demand prediction, analyzes the research status and development direction in this field at home and abroad, and introduces the characteristics and development trend of the models used specially. The problems in current study and future research direction are pointed out, and the research results and the research results that can be used for reference are summarized, which can provide reference for future research on the further development of natural gas demand.
Using a mixture of water and ethanol as medium, acrylamide (AM) as monomer, polymethylacrylic acid trithiocarbonates (PMAA-TTC) as chain transfer agent and AIBA as initiator, the polyacrylamide (PAM) was synthesized by dispersion polymerization. The effect of reaction media, monomer, initiator, reaction temperature and solid content on polymerization were investigated. The optimum reaction conditions were that the mass ratio of ethanol and water was 7∶3, the molar ratio of AM/Macro-CTA/AIBA was 6 000∶5∶1, the temperature was 50 ℃and the solid content was 10%.
Alkylphenol polyoxyethylene ether surfactants have good emulsifying properties and are common raw materials for silicone oil emulsifiers, however, the by-products and their final metabolites in the production process are highly toxic and can not meet the EU requirements on environmentally friendly surfactants. The non-ionic surfactant complex system without alkylphenol polyoxyethylene ether as silicone oil emulsifier was studied in this paper. The experiments were designed and optimized with uniform design software. Under the condition that the quality fraction of emulsifier was 7%, different kinds of non-ionic surfactants were used as emulsifiers to determine the value range of each factor and set an appropriate level within this range. According to factor number and level number, the appropriate uniform design table was selected for factor horizontal data arrangement, and the experimental points in the uniform design table were tested. The obtained experimental data were analyzed by regression analysis, the regression model was established, and the optimized experimental points of the regression equation were verified experimentally. The synergistic effect of surfactants and the effect on the stability of emulsified silicone oil were investigated. The optimal environmentally friendly nonionic silicone oil emulsifier without alkylphenol polyoxyethylene was obtained.
Phthalate-based plasticizers are the most added additives in polyvinyl chloride, however, it was found that the monomer-type plasticizer had poor migration resistance and potential carcinogenicity, which seriously affected the application performance and service life of the product. Polypropylene glycol adipate (PPA), epoxy soybean oil (ESO) and dioctyl phthalate (DOP) were compounded in this paper. The mechanical properties, plasticizing efficiency, thermal properties and durability of the plasticizer were investigated. The results show that the plasticizing efficiency of 40DOP/10PPA and 40DOP/10ESO is better than 110%, the performance of anti-extraction and anti-volatilization is much better than DOP, which can greatly reduce the glass transition temperature of PVC and improve its processing performance of PVC.
Acidity and accessibility of three commercial zeolites (HY, HMOR, Hβ) were characterized by using in situ FTIR spectroscopy with pyridine (Py), 2,6-dimethylpyridine (DMPy) and 2,6-di-tertbutylpyridine (DTPy) as the probing molecules. The results indicate that the surface acid density of HY molecular sieve is the highest, and there are abundant strong B acid centers, strong L acid centers, and many weak B acid centers. However, the surface acid density of HMOR and Hβ is low, and it is mainly the strong B acid center and the strong L acid center. The accessibility index of B -acid center is calculated by changing the hydroxyl group of Si-Al bridge. The results show that the order of accessibility of macromolecule probes to Br-nsted acid sites in these three type of zeolites is HMOR＞Hβ＞HY.
Based on the power law rheology model of alkali-surfactant-polymer (ASP) fluid, the seepage flow model of ASP flooding for horizontal wells and the variable mass flow model in horizontal wellbore are established. Then the horizontal wells performance prediction model is set up by coupling the seepage flow model and the variable mass flow model. The influence of power law index and consistency factor on horizontal well production has been studied. The results indicate that the IPR curve of ASP flooding is concave upward. The production decreases with increasing of the value of the power law index and consistency factor. In different flooding periods, the IPR curves is different. The corresponding IPR curve should be used to predict the production in different flooding periods. The prediction results can basically meet the actual requirements, which provides a basis for the parameter control of three element composite flooding in horizontal wells.
The enhanced oil recovery technology of ASG (alkali, surfactant and nitrogen) composite foam and water alternating injection was studied in high temperature and high salinity low permeability reservoir. The ASG foam and water alternating injection experiments were carried out through indoor flooding experiments, and compared with water flooding nitrogen flooding and surfactant flooding. The results show that the enhanced oil recovery of the method adopted by this study is 16.61%, 10.26% and 9.21%, respectively, compared with water flooding, nitrogen flooding and surfactant flooding technology. Experimental study on injection parameters optimization of ASG foam and water alternating injection is carried out, and the parameters such as slug size, injection rate and gas fluid ratio of ASG composite foam are optimized by bench scale displacement test. The results show that under the condition of the same foam injection volume (1.2 times the pore volume), the effect of foam slug injection with 0.4 times pore volume is best. The foam injection rate has an optimum value of 1.5 mL/min. When the injection rate is too low, less foam is produced, gasliquid separation is easy to occur, and the blocking effect is poor. When the injection rate is too high, the size of the bubble is different, and it is easy to cause the bubble to merge, causing the bubble to burst, and at the same time, it is easy to cause the shear defoaming of the foam. When the gas fluid ratio is 3∶1, 2∶1 and 1.5∶1, respectively, the recovery rate is 2.04% higher than that of the single gas fluid ratio.
A simulation experiment is carried out for polymers which are different from the viscoelasticity of Newtonian fluids. In order to describe the rheology of polymer solution accurately, the constitutive equation of Maxwell is used to control the fluid characteristics. What's more, a physical model of polymer solution flowing in the micro waterwet capillary is established. Finally, CFD software was used to carry out numerical analysis of the model. The pressure fields, stress fields and velocity fields of polymer flow are obtained by numerical simulation, and the change state of polymer flooding is studied. Through pressure, stress, velocity field changes, we can intuitively realize that in the process of polymer flooding, the unique elasticity of the viscoelastic fluid increases the volume of the residual oil by the displacement fluid during the extrusion collision, and makes the original flow of oil flow. The research results can further improve the polymer flooding microscopic seepage theory.
Stress sensitivity is one of the factors influencing fracture net deliverability of multistage fractured horizontal well for tight sandstone gas reservoirs. Based on seepage characteristic of tight sandstone gas reservoir, seepage law after fracturing work and steady seepage theory, flowing resistance method was used to derive fracture net deliverability correlation considering stress sensitivity of multistage fractured horizontal well for tight sandstone gas reservoirs, and then the correlation was used to analyze fracture parameters and stress sensitivity level on gas production rate. The results indicate that with increasing fracture flow conductivity and fracture net permeability, gas production is gradually increased, but the increase is slowed down. The unimpeded flow increases gradually with the increase of fracture half length, and increases rapidly with the increase of fracture conductivity. Therefore, in order to improve gas reservoir productivity, it is more significant to improve fracture halflength than fracture flow conductivity. The greater the stress sensitivity coefficient is, the greater the permeability decreases with the production, and the more the productivity of the gas well decreases.
The casing damage of production and injection wells affects the oil field production and development efficiency. The well casing damage is caused by its production or injection volume variation which is resulted by the stress concentration effect. It becomes difficult to determine the casing damage index boundaries of reducing the damaged casing pipe appearing probability. Using the method of large data mining, based on the "five effects" of the development factors to screen the index and data of the "damage" of the damage, the main development index and the correlation curve of the casing damage are set up, and the index limit of the occurrence of the casing damage is determined. The comprehensive fuzzy evaluation method is used to evaluate the risk of single well development factors. The coincidence rate of the historical data of high risk wells is above 70%, and the risk level of the single well casing damage is divided, so the adjustment and adjustment of the casing damage are more pertinent.
A series of cationic functional polymers with different cations and molecular weights were used to determine the oil water interfacial tension, Zeta potential and O/W emulsion stability of the oil and water of the Gudong crude oil. It was found that when the molecular weight was almost the same, the bigger of the cationic degree, the better ability of breaking the O/W emulsions by the polymers . And in the region of the investigated concentration, at higher concentration of the polymer, better demulsification effects were obtained. The results of interfacial tension and zeta potential measurements indicated that the reason of the demulsification of emulsion by this kind of cationic functional polymer was the electrical neutralization on the interface between oil and water. That is to say, when polymer was added to the emulsion, it could neutralize the charges on the interface and as a result the oil droplets coalescenced.
In view of the increasing water content in China's oil fields, foam has good pugging performance and flow redirection effect, and has broad application prospects. In this paper, the sealing characteristics of bubble redirection effect was studied, the fluid flow was investigated under the condition of different seal characteristics of foam, and effect of flow redirection and enhancing oil recovery was examined. The results show that the foam has good plugging performance, and can be effectively blocked under suitable conditions. The higher the back pressure, gas liquid ratio and core permeability are, the lower the injection speed is, the bigger the resistance factor and residual resistance factor of the foam are, the greater the plugging is. For non-homogeneous reservoirs with a permeability differential of 5.56, foam has effect of flow redirection and can plug the high permeability layer in core selectively. The subsequent injection of water into the low permeability layer will drive out the residual oil, and the bubble drive will increase the recovery rate by 28%.
The pore structure of tight sandstone formation is very complicated, which has significant effects on the percolation of oil and gas. So, elaborate characterization is needed. The fractal geometry theory has provided an effective way for the quantitative characterization of pore structure. Based on the mercury intrusion data of the tight sandstone samples collected from FY formation in Daqing oilfield company, the multiple characteristics of pore structure in tight sandstone reservoirs are quantitatively studied by the two parameters of fractal zone and fractal dimension. The results show that the microscopic pore structure of the tight sandstone samples has multiple fractal features and the numbers of fractal zones can characterize the heterogeneity of formation. The number of fractal interval is the same as the peak value of pore radius distribution curve. The more fractal interval, the stronger the heterogeneity, and the worse the porosity and permeability of reservoir. For the same sample, the larger the pore radius for fractal zones is, the stronger the heterogeneity of pore structure is. For different samples, the larger the comprehensive fractal dimension is, the more the fractal zones are and the worse the porosity and permeability of formation become.
In order to provide basis for reservoir prediction, the characteristics of nanometer-micron pore throat in dense conglomerate reservoir and its relationship with physical properties and productivity are discussed. Through thin slice observation, scanning electron microscope, high pressure mercury pressure, constant speed mercury pressure and physical properties test, a systematic analysis of reservoir space types, pore throat distribution, connectivity and physical properties is carried out. The results show that the pore types including dissolved pores, intercrystalline pores, primary intergranular pores, microcracks,with the feldspar solution pores and debris solution pores have the greatest contribution to porosity, followed by intercrystalline pores of clay minerals. The distribution shape of pore throat is bimodal, and the radius of most pore throat is less than 1 μm. The pore is connected by few large throat and micro-fracture, resulting in poor correspondence between porosity and permeability. Comprehensive analysis of pore size classification, reservoir physical properties and reservoir productivity shows that pore types have a controlling effect on reservoir physical properties and productivity. The porosity and permeability, gas content and productivity of reservoirs are lower when more capillary and microcapillary are developed in the pores. This explains the difference between the exploration efficiency of relatively high porosity reservoirs and relatively low porosity reservoirs. Geological conditions for the development of nanocapillary and microcapillary are discussed. It is suggested that the prediction of sedimentary facies and the study of diagenetic facies should be strengthened in reservoir prediction.
In the case of low speed and high pressure, the wear of dry gas seal is more serious, therefore, the preparation of DLC film by static ring is proposed, and the friction characteristics of the end face of the static and dynamic ring are analyzed with the groove structure. The dry gas seal with different spiral angle was tested by friction and wear machine, and the change law of temperature rise, friction coefficient and surface wear morphology were tested. The test results show that with the increase of load and speed, the friction temperature rises, friction coefficient and grinding mark of 16° spiral angle are less than 18°. Under the same working condition, the value of average friction coefficient of 18°spiral angle is 0.02 larger than that of 16°spiral angle, and the average friction temperature is increased by 5 ℃. On the one hand, because of the different spiral angle, the interface method is different and the wear degree of the end face of 18° spiral angle is greater than 16° spiral angle. On the other hand, with the increase of load and speed, the graphitization degree of DLC films is increased, which shows DLC films and spiral groove play a key role in the friction and wear of end faces. At the same time, it is found that the wear degree of the two kinds of spiral angle inner ring is greater than the outer ring, so the spiral groove can reduce the wear degree of the end face. The test results laid a foundation for the optimization design and practical application of spiral groove dry gas seal.
The modified hall curve method is qualitative identification of stratum pore passage characteristics from relative relationship between derivative curve and integral curve. The analytic solution formula contains the work systemrelated parameters, however, the work system often changes in practice production, therefore, this formula is slightly different from the ideal model used in the modified hall curve method. The derivative numerical solution curve and analytic solution curve plotted according the actual production data are different from the modified hall curve. In order to avoid the effect of work system on analytic solution and quantitatively identify pore passage characteristics, the derivative numerical solution calculated from the production data of one block was taken into the analytic solution formula, and the proposed correction efficient was used to modify the parameters related to the working system, and the correction efficient was 1.2. The permeability was used as an unknown value, and the derivative numerical solution calculated from the initial production data of the block was taken to the analytic solution formula. The comparison of the calculated permeability and actual formation permeability of the wells showed that the number of wells with the error below 8% accounted for 91.4% of total number of wells, verifying that this method was rational and effective. For one well, the permeability was 16.41 mD at initial production stage, and the predicted formation permeability was 36.77 mD after longterm water injection. It was found that an increase in formation permeability after longterm water injection showed that preferential migration passages were produced, which was consistent with the plotted modified Hall curve.
Aiming at the problem of reasonable formation pressure and reasonable flow pressure in low permeability oilfield, the variation law of formation pressure under different water cut, recovery degree and injection-production ratio was studied, a new method for calculating reasonable formation pressure was established, and the rational strat igraphic pressure range and the adjustment of pressure system in each block in Pubei area was obtained. Considering the effect of water content and liquid production on correcting the actual IPR curves of each fault block in Pubei area the reasonable flow pressure range of each fault block was calculated, the correction equation of inflow performance under various connected conditions of single well in Pubei area was established, and the reasonable flow pressure range of some single well was calculated. The results show that the evaluation method of formation pressure and flow pressure is more reasonable. According to the calculated minimum reasonable formation pressure and the minimum reasonable flow pressure of each fault block, the oil increasing effect of the adjustment well is obvious and the formation pressure tends to be reasonable. The gas influences of the wells were well controlled and the pump efficiencies were improved by adjusting flow pressure.
