Based on the coupling method of the Navier?Stokes equation and phase field theory, the pore scale numerical model for fractured mixed?wet tight reservoir is established to investigate the oil recovery process under different injection velocities, injection modes, and injection?shutdown durations. The findings indicate that the injection velocity has a nonlinear correlation with the oil recovery, with an optimal velocity of 0.01 m/s, where the dynamic equilibrium between capillary force and viscous force achieves the highest fracture?matrix pressure transfer efficiency, leading to a peak recovery degree. The periodic intermittent water injection demonstrates a 48% reduction in water usage compared to constant rate injection, with a slight 1.08% reduction in recovery, making it more economical under low oil prices. The short?cycle high?frequency water injection with low injection?shutdown durations can generate periodic pressure fluctuations, reducing cumulative water injection by 80%, while achieves comparable recovery performance to long?cycle injection.This study investigates the influence law of injection parameters on the synergistic enhancement mechanism of imbibitiondisplacement during water flooding in tight oil reservoirs with mixed wettability, providing a theoretical basis for optimizing injection strategies.

The water film formed within the pores of tight reservoirs leads to a distinct "oil?core water?film" configuration in the distribution of oil and water within the porous medium, which has a significant impact on the flow channels and capillary forces of infiltration and absorption. To address these phenomena, high?pressure mercury injection and core imbibition experiments were conducted to study the microscopic distribution characteristics of oil?water and the underlying mechanisms of capillary forces. A capillary force calculation model considering water film thickness was established to elucidate the influence of water content distribution on capillary force. The results indicate that as the oil phase pressure increases, the water film on the pore wall gradually becomes thinner until it stabilizes. Under the same pressure, the smaller the pore size, the larger the proportion of water film to the pore size. When the capillary radius is less than 30 nm, the smaller the radius, the greater the influence of water film on capillary force; when the capillary radius is greater than 30 nm and the water saturation is greater than 0.60, the capillary force calculated with and without considering the water film is basically equal, and the influence of the water film on the water saturation and capillary pressure is relatively small. When the water saturation is less than 0.60, there is a significant difference in capillary force between the two conditions. Higher water saturation corresponds to a smaller deviation in capillary pressure. Furthermore, lower capillary forces are associated with reduced imbibition capacity and permeability of the rock core.

A new type of combined cooling, heating and power (CCHP) system is proposed, consisting of a dual recompression Brayton cycle, a CO₂ reheat Rankine cycle and a two?stage flash cycle, to achieve synergistic waste heat recovery from a natural gas?fueled solid oxide fuel cell, utilization of liquefied natural gas (LNG) cold energy, and capture of CO? from flue gas. The cycle system was simulated using thermodynamic simulation software to analyze the effects of the mass fraction of mixed workmass Xe, the inlet pressure p₂₃ of the CO₂ reheat Rankine cycle expander, the pump outlet pressure p₂₆ of the flash cycle, and the shunt ratio x on the system's thermal efficiency, saprophytic efficiency, net work output, and cold water recovery rate. The results demonstrate that increasing p₂₃ is favorable to improve the net output work, thermal efficiency and hydronic efficiency of the system; decreasing p₂₆ is favorable to improve the net output work and thermal efficiency of the system, and increasing the Xe mass fraction and shunt ratio can improve the net circulating work, thermal efficiency and hydronic efficiency of the system. When the mass fraction of Xe is 0.3, p₂₃ is 16 MPa and p₂₆ is 13.5 MPa, the thermal efficiency, the net efficiency and the net output work of the system are 67.17%, 58.13% and 2 587.96 kW, respectively.

Wellbore instability is easy to occur when drilling fractured shale formation. Based on mechanical experiments, this paper investigated the weakening law of mechanical properties of shale soaked in drilling fluid.Considering the influence of stress?pressure?temperature?solute concentration disturbance and natural fractures, a multi?field coupled thermal?hydraulic?mechanical?chemical wellbore stability analysis model of fractured shale formation was established.Based on the characteristics of wellbore instability, the window chart of safe drilling density in fractured shale formation with different rock strength parameters is established. The results show that with the increase of drilling fluid soaking time, the strength parameters and elastic parameters of shale deteriorate exponentially. Considering the non?uniform distribution of physical fields around the well after the development of natural fractures, the stress concentration at the crack tip leads to the collapse and tensile failure zone toward it. Increase of horizontal in?situ stress difference and fluid pressure difference will enlarge the tensile and collapse failure zone, and the increase of solute concentration difference will help reduce the failure risk. Increasing drilling fluid temperature has little effect on collapse failure, but it can significantly reduce the risk of tensile failure. The investigation can provide guiding suggestions for safe drilling design in fractured shale formation.

In the process of oil and gas field production, as well as in the gathering and transportation phases, the water jacket furnace coil serves as a crucial component for natural gas heating, playing a significant role in both heating and energy support. However, the presence of fine grit within the water jacket furnace coils can result in erosion damage that is challenging to predict. Therefore, it is essential to understand the factors influencing the erosion of water jacket furnace coils and to establish an effective predictive model. This study employs computational fluid dynamics (CFD) simulations and sensitivity analyses to investigate the effects of temperature, pressure, gas flow rate, particle diameter, bend diameter, and curvature radius on the erosion of water jacket furnace coils. The results indicate that the gas flow rate, particle diameter, bend diameter, and curvature radius are the primary factors affecting erosion. Consequently, a comprehensive erosion prediction model is developed, providing a scientific basis for equipment maintenance and safety management. The findings of this study offer a vital reference for addressing the erosion issues associated with water jacket furnace coils and hold practical significance in engineering applications.

Dome top tanks are important facilities for oil storage, and in order to reduce the evaporation loss of storage tanks, it is necessary to conduct research on their evaporation loss mechanism. Establishing a UDF for the absorption of heat flux at different times in a dome roof tank, and using FLUENT 19.0 software to simulate and analyze the effects of solar radiation intensity, oil storage height, and oil storage time on the diffusion of oil and gas inside the tank, the simulation results showed that: the gas temperature distribution inside the tank was uneven, with a vertical distribution of high and low, and the average gas temperature inside the tank decreased with the increase of oil storage height. The mass fraction of oil and gas in the tank is similar at the same oil level height, with the highest mass fraction on the oil surface. The vapor mass fraction is positively correlated with the oil storage height and storage time. The maximum pressure value of the gas inside the tank in a day first increases and then decreases, gradually increasing with the height of the liquid level. This study provides a basis for evaluating the evaporation loss of storage tanks and designing and managing oil and gas recovery systems

Risk evaluation is the core work of pipeline integrity management and the prerequisite and foundation for realizing risk prevention management. Zhoushan submarine pipeline has harsh service conditions, difficult monitoring and maintenance, and serious consequences of accidents. In order to ensure the safe operation of the submarine pipeline. Integrating the service conditions and operational characteristics of the Zhoushan section of the Xinao LNG submarine pipeline, this study first identifies risk factors through systematic hazard analysis. Subsequently, the modified Kent methodology is applied to quantify relative risk values. According to the size of the relative risk value, the risky pipeline sections of this LNG pipeline system were graded. The results show that the relative risk value of the Zhoushan section of the submarine pipeline is predominantly within the 100~200 range, and the risk rating is at a low level. Meanwhile, risk management measures and recommendations for Zhoushan submarine pipeline are proposed. These strategies are aimed at promoting the realization of a risk?level?based management mechanism, thus providing scientific guidance and reference bases for the safe operation of submarine pipelines.

The optimization process in reservoir history matching belongs to the high?dimensional system's optimal control problem, and the selection of a suitable optimization algorithm is crucial for achieving a good fitting effect. As gradient?based methods face challenges in computing the gradient of the objective function, intelligent optimization algorithms with stochastic properties are widely applied in reservoir optimization processes. A method for reservoir history matching based on real?number coding genetic algorithm RGA and connectivity model was proposed. This method eliminates the need for encoding and decoding operations by directly using feasible solutions obtained from traditional solving methods as initial parameters for the improved genetic algorithm, thereby reducing the complexity of the search space. In RGA, real?number coding is employed to represent parameters, enabling the algorithm to handle continuous variables directly, thus enhancing search accuracy and convergence speed. A adaptive selection strategies, crossover, and mutation operations are introduced in this paper to further enhance the algorithm's performance. Application of RGA to the history matching problem in a mechanistic model demonstrates that RGA can effectively improve fitting results and find relatively optimal solutions in a short time. Therefore, this method has significant potential for widespread application in reservoir history matching problems.

Using molecular dynamics, the lowest energy configurations of n?dodecane, n?octadecane, and n?nonadecane were constructed, and the interactions between oil molecules and wax molecules were studied at different water contents (mass fractions). The molecular dynamics model of crude oil emulsion system based on different mass fraction water content was constructed. The effect of water molecules dissolved in the system on the viscosity of waxy crude oil was studied. The radial distribution functions of wax molecules in different water content systems were compared. The results show that carbon number is the main factor to determine the interaction energy between crude oil molecules. With the increase of water content, the distance between molecules increases, while the interaction energy decreases. After water molecules are dissolved in the system, the distance between wax molecules and electrostatic interaction become larger, the distribution of wax molecules becomes disordered, and the flow characteristics of crude oil are improved.

The low?permeability reservoir in Qiuling Oilfield of Tuha shows that the characteristics of early water discovery and rapid rise of water cut in some wells during water injection development, and dynamic analysis shows that there are dominant channels or the possibility of fractures in the reservoir. In order to further improve the development effect and enhance oil recovery, it is necessary to verify and determine the development of micro?fractures in the reservoir at the later stage of reservoir development. In this paper, based on the description of the core of a water washing inspection well, the development and distribution of reservoir fractures are studied, and a method of identifying the fracture development horizon based on logging curves are proposed. Through the analysis of logging data of two wells and the comparison of water absorption profiles, the method is proved to be feasible and reliable, and the study provides theoretical support for improving the development effect of water drive, effective utilization and recovery of remaining oil in Qiuling Oilfield of Tuha.

During the extraction and transportation of waxy crude oil, paraffin will deposit on the wall, forming wax deposition. In recent years, microbial wax removal and prevention technology has been widely studied for its economic and environmental advantages. Five strains of bacteria were screened from crude oil sludge, and through the determination of their paraffin degradation rate and surface hydrophobicity, the bacterium B3 was selected and identified as Bruella intermedia. The experimental results showed that bacterial B3 had the best growth activity at a temperature of 40 ℃, an initial pH of 6, and a shaking table speed of 160 r/min, and had the best degradation effect on paraffin at this time. When bacteria B3 grows and metabolizes with paraffin as a carbon source, they can produce lipopeptide biosurfactants, with an emulsification coefficient of 52.5% for liquid paraffin. After 7 days of interaction between bacteria B3 and crude oil, the wax prevention rate reached 77.2%, and the viscosity reduction rate reached 50.2% at 41 ℃. Bacterial B3 can degrade paraffin, improve crude oil fluidity, and reduce wax deposition.

Dehydration of crude oil is an important step in the production and processing of crude oil. As oil fields enter the high water cut stage of production and the addition of oil recovery additives, dehydration becomes increasingly difficult, so the use of high?frequency electric fields for electric demulsification has become an effective means of dehydration. This article investigates the mechanism of electric dehydration under high?frequency electric field through static dehydration experiments and numerical simulations of droplet electric coalescence. It is found that the electric field strength, frequency, and duration have significant impacts on dehydration efficiency when treating crude oil with electric demulsification and dehydration. In the process of electric demulsification and dehydration, there is an optimal electric field frequency. After the electric field strength increases to a certain value, continuing to increase the electric field strength will actually lead to an increase in water content. After the electric field action reaches a certain time, continuing to increase the electric field action time will result in little change in the water content of crude oil; the greater the electric field strength applied to droplets in the electric field, the more likely the droplets are to deform, and the larger the diameter of the droplets, the more likely they are to deform; compared with the power frequency electric field, droplet coalescence efficiency is higher under high?frequency electric field, and droplets are more prone to coalescence. The research results provide theoretical support for the design and parameter optimization of crude oil electric dehydration units.

In view of the influence of different factors on the leakage and diffusion of hydrogen?doped natural gas pipelines in the pipe gallery, the leakage and diffusion model of hydrogen?doped natural gas pipelines in the pipe gallery was established by numerical simulation software, and the influence of factors such as hydrogen doping ratio, pipeline pressure，leakage hole size and the model of ventilation on the gas diffusion process was studied. The results show that the hydrogen blending ratio can affect the mass transfer ability of hydrogen?doped natural gas, and the higher the hydrogen blending ratio, the faster the diffusion rate of hydrogen?doped natural gas. The pipeline pressure and leakage hole size mainly affect the leakage gas diffusion by affecting the initial kinetic energy and leakage volume of the leakage gas, and the leakage gas diffusion range becomes larger with the increase of pipeline pressure and leakage hole size. The ventilation mode plays a dominant role in the distribution of leaked gas in the pipe gallery, and the ventilation frequency is inversely proportional to the height of the leaked gas jet.

Offshore oilfield development faces complex geological conditions and high development costs, with limited platform lifespans and well locations. These constraints reduce the effectiveness of chemical flooding for enhancing oil recovery. Based on the geological characteristics of offshore oilfields, and drawing on the results of synergistic enhanced oil recovery (EOR) techniques combining chemical flooding and infill well patterns in Daqing, Dagang, and Shengli oilfields, this study evaluates the synergistic potential of chemical flooding agents, well pattern infill, and layer adjustment. The synergy between chemical flooding and infill well pattern optimization for enhanced oil recovery was established. Relying on numerical simulation, an optimized design for synergistic chemical flooding and infill well patterns was developed for the SZ36?1 oilfield. The effects of reservoir permeability, permeability heterogeneity, and crude oil viscosity on enhanced oil recovery potential were clarified, along with the establishment of corresponding boundaries. The study demonstrated that after the original inverted nine?spot well pattern is encrypted into an oblique inverted nine?spot well pattern, the well spacing is reduced by half. Combined with polymer flooding technology, the recovery rate can be increased by 9.8%, which is 3.4% higher than the sum of the recovery increases achieved by independent water flooding and polymer flooding. This result confirms that by utilizing the synergistic effect of chemical flooding and infill well pattern technology in offshore oilfields, the sweep efficiency of the oil displacement system can be significantly enhanced, leading to a substantial increase in recovery rates and optimization of production capacity.

The forward and reverse transportation simulation model was established by using SPS simulation software to simulate the forward and reverse operation process of A?Sai crude oil pipeline at low throughput. The change law of the oil temperature along the pipeline during the process of forward and reverse transportation is studied. The results show that the oil temperature along the pipeline decreases gradually under the steady state of forward transportation. The oil temperature drops first and then increases at the beginning of the reverse transportation, and then drops gradually after reaching the steady state.The oil temperature at the reverse inlet station decreases first and then increases slightly, and finally tends to be stable. The lowest temperature of crude oil in the process of forward and reverse transportation is the arrival temperature when the remaining crude oil is completely pushed out of the pipeline. In addition, the influence of inverse throughput on oil temperature drop during the inverse transportation was analyzed. The higher the inverse throughput is, the higher the lowest oil temperature in the process of inverse transportation is, and the faster the stable state of inverse transportation reaches. The temperature change of forward and reverse transportation obtained by SPS simulation analysis can provide certain basis for making the forward and reverse transportation scheme of A?Sai pipeline.

The study of the micro high viscosity mechanism of heavy oil is of great significance for the efficient development of Bohai heavy oil. Therefore, aiming at the typical heavy oil reservoirs in Bohai Sea, the microscopic mechanism of high viscosity of heavy oil is analyzed and studied from the aspects of viscosity?temperature relationship, crude oil composition and component polarity, heteroatom distribution and asphaltene aggregate structure. The results show that compared with N oilfield in Bohai Sea, the content of alkanes and aromatics in L oilfield in Bohai Sea is lower, and the quality score of resins and asphaltenes is higher, reaching 29.95% and 9.76% (23.25% and 6.59% in N oilfield). The quality score of heteroatoms such as O,N and S are high, and the relative molecular mass of resins and asphaltenes are also high. The polarity of each component is strong, and the dipole moments of resins and asphaltenes reach 14.01 D and 17.94 D, respectively (9.12 D and 12.25 D in N oilfield ). These will lead to stronger intermolecular forces and stronger intermolecular association between resins and asphaltenes. The smaller asphaltene molecular spacing and the denser aggregate structure,which will eventually lead to higher viscosity of crude oil.

Ultra?deep wells of over 10 000 meters have been successfully drilled in China, and deeper breakthroughs has been made in drilling and completion equipment technology, which indicates that China has achieved a significant milestone in the field of oil exploration and development. It is crucial to improve drilling efficiency and ensure safety in this context. Intelligent drilling and completion technology is a core solution to the challenges faced in the industry. It offers significant advantages in improving drilling efficiency and safety. By integrating advanced automation control, real?time data monitoring, and machine learning technology, it optimizes drilling operations. This not only improves drilling efficiency but also dramatically enhances drilling and completion safety. This paper summarizes the current development status of intelligent drilling and completion equipment technology. It proposes a trinity research approach that includes automation control, real?time data monitoring, and machine learning technology. The paper focuses on analyzing the development journey and technological innovation of domestic and international innovative equipment, such as intelligent drill bits, intelligent guiding tools, intelligent drill pipes, intelligent slip sleeves, and intelligent drilling rigs. To achieve comprehensive development of intelligent drilling and completion equipment technology in the future, it is recommended to utilize artificial intelligence, intelligent optimization algorithms, and foster domestic and international cooperation.

The crude oil produced by oil wells contains sediment, scale and other particles, which are deposited together with the wax in the process of crude oil pipeline transportation. It leads to a decrease in pipeline throughput, and may cause pipeline blockage and affect the safety of transportation in severe cases.The yield stress test and microscopic characteristic experiments show that there is a critical scale containing ratio in wax deposits of the influence of calcium carbonate scale on the strength of wax deposits. And it is found that the wax deposits containing scale will increase the breaking force on the wax layer and the pigging efficiency of the pig through the indoor pigging experiment of polyethylene pipeline. Based on the data of pigging experiment, a prediction model of pigging efficiency was established by using the π theorem. The model was validated by indoor experiments and third?party literature experimental data.

To study the influence of hydrogen mixing ratio on the leakage of natural gas pipelines, a mathematical model for the leakage and diffusion of directly buried high?pressure hydrogen mixed natural gas pipelines was established based on computational fluid dynamics theory and numerical simulation method.The leakage status, volume fraction distribution of hydrogen mixed gas,and the distribution of soil pressure and gas velocity around the pipeline were analyzed under different hydrogen mixing ratios.The results show that with the increase of hydrogen mixing ratio, the explosion radius of hydrogen mixed gas in the atmosphere will gradually decrease,and the range of high?pressure area around the pipeline will gradually decrease,and the gas flow rate at the leakage port will gradually increase.When the hydrogen mixing ratio is 30%,the explosion radius in the atmosphere is reduced by 43%,and the gas flow rate at the leakage port is increased by 68%.This provides a theoretical reference for the safety and emergency repair of hydrogen?doped natural gas pipelines and has important practical significance for promoting the large?scale application of hydrogen?doped natural gas.

Infrared thermal imaging technology is widely used in the study of precursor characteristics and early warning methods of rock failure. However, infrared radiation precursory features have many forms, so it has certain influence on the accurate early warning of rock instability. The failure and instability of rock are closely related to the evolution of strain energy, and the infrared radiation information of rock is related to the dissipation and release of strain energy. If the strain energy is combined with infrared radiation information, the rock failure and instability can be monitored and warned accurately. Based on this, in this paper, the release time of elastic energy is determined by the cusp mutation theory based on the energy evolution characteristics, which is combined with the infrared radiation anomaly information to determine the precursor of rock failure and instability. The results show that with the sudden drop of the elastic energy curve, the infrared radiation synchronization appears abrupt change. The elastic energy release time of sandstone predicted by constructing the sharp point mutation model can be divided into two situations: leading and lagging the first mutation time of infrared radiation. Taking the elastic energy release time as the standard, the infrared radiation mutation near the sandstone can be regarded as the precursor of sandstone failure. The results can provide a new idea for mine disaster monitoring and early warning.

In some areas of Xinjiang, the dip angle of coal seams can reach 50 °. Unlike horizontal coal seams, fluids in high dip coal seams are severely affected by gravity, and the pressure propagation law of coalbed methane wells has special characteristics. The optimal drainage and extraction well position needs to be optimized. This article considers the gravity effect of formation water and establishes a pressure propagation model for single-phase drainage in steep coal seam, and verifies the correctness of the model.Then, the water production of fractured wells in the inclined reservoir is calculated under stable seepage conditions, and the optimal drainage well position is optimized. Finally, numerical simulation methods are used to study the pressure propagation laws of single wells and well groups in heterogeneous bounded inclined reservoirs. The results show that in a high dip coal seam with an inclination angle of 45 °, the position where the distance ratio between the drainage well and the upper and lower boundaries is 3 : 1 is the optimal drainage well position; under the constant pressure drainage mode, there is not much difference in the pressure drop amplitude between the downward and upward tilt directions. In the constant speed depressurization and extraction mode, the pressure drop amplitude in the upward tilt direction is much greater than that in the downward tilt direction.

At present,most oil fields in China have entered the high water cut period,and the flow characteristics of produced fluid have changed, so it is possible to reduce the temperature of gathering and transportation.However,there are relatively few studies on the influence of pipeline materials on low-temperature gathering and transmission characteristics. Therefore, the characteristics of low-temperature gathering and transportation of high water content crude oil in steel pipe and fiberglass pipe are studied.The results show that the wellhead back pressure rises and the oil temperature at the end of pipeline drops slowly after the water content of the pipeline is reduced. The wellhead back pressure rises differently under different water content.When the water content is the same, the temperature of fiberglass pipe is lower than that of steel pipe, and the minimum water content of fiberglass pipe for low-temperature gathering and transportation is lower than that of steel pipe under the same condition.Based on the experimental data of viscosity wall temperature,the calculation models of different pipe materials are obtained,and the calculation results are accurate, which has a guiding significance for the feasibility judgment and safe operation management of the oil field in the high water cut period.

In order to understand the mechanism of CO₂ dissolved buried mechanism in high temperature and high pressure porous environment,physical simulation experiment was conducted to study CO₂ dissolved buried mechanism,mineralization buried mechanism and free buried mechanism in porous media by means of indoor physical model experiment.The results show that the solubility of CO₂ in formation water is mainly affected by temperature, pressure and salinity of formation water. CO₂ dissolved in formation water will mineralize with minerals in rocks, and the mineral content of rocks will change significantly before and after the reaction. The long core displacement experiment characterized the amount of free CO₂ storage and the oil displacement effect. The experiment reveal that CO₂ flooding in porous media has dual effects of burying and enhancing oil recovery.

In order to study the influence of cross?fracture on the mechanical properties and damage modes of deep shale, and better understand the damage evolution law of shale containing cross?fracture under high temperature and high pressure coupling, 15 groups of shale models containing cross?fracture with different inclination angles were established, and simulation experiments were carried out to study the stress?strain relationship, damage evolution and acoustic emission characteristics of the shale specimens. The results show that the compressive strength and modulus of elasticity of shale are negatively correlated with the inclination angle of the main cracks, and show an upward concave trend with the increase of the inclination angle of the secondary cracks, and the compressive strength of shale decreases significantly when there are cracks perpendicular to or close to perpendicular to the loading direction; the damage modes of shale specimens under the influence of cross?cracks are mainly divided into "X"?shaped damage, diagonal "N"?shaped damage, diagonal "W"?shaped damage, inverted "V"?shaped damage, damage along the main crack, "V"?shaped damage and "λ"?shaped damage; the fractal dimension of shale specimens is negatively correlated with the inclination angle of the main crack, and as the inclination angle of the main crack decreases, the value of fractal dimension tends to increase, and the corresponding damage pattern of the specimens is more complicated and the internal damage is more intense.

At present,there are few studies on the influence of medium and low water saturation on the capacity of free gas storage.Therefore, this study simulates the multi?round gas injection?soaking?production process through laboratory experiments; The laboratory experiment was carried out to simulate the process of multi?round gas injection?well soaking?production. Combined with the mathematical model and numerical simulation results, the research shows that the reservoir capacity increases with the increase of injection?production rounds, but the increase after single?round injection?production decreases rapidly.When the initial water saturation is higher than 50%, the increase of water saturation is beneficial to the reconstruction of gas storage, but the increase of injection?production capacity and storage capacity is relatively slow in the early stage of reservoir construction. When the initial water saturation is increased from 50% to 85%, the gas saturation is reduced by about 9.27% after 6 injection?production cycles. When the injection?production cycles are increased to 20,30,50 cycles, the free gas storage capacity is increased by about 0.51%,3.33%,6.61%, respectively. The research results are expected to provide reference for the evaluation of injection?production capacity and storage capacity of reservoir?type gas storage.

In recent years, with the continuous increase of foreign crude oil imports and the decline of domestic oilfield production, different oil products may need to be transported together by the same oil pipeline during the transportation process.The fourth oil pipeline of Qingtie is taken as an example. Combined with the actual parameters, the pipe wall is discretized by using the finite element analysis method of ANSYS and the hexahedral structural grid. The thermal structure coupling problem of the buried pipeline is solved, and the corresponding thermal stresses of the straight pipe section and the bent pipe section at different temperatures are calculated respectively. Based on the theory of fracture mechanics,the number of annual limit cycles under different service life is calculated, and the influence of temperature alternation on pipeline fatigue life is analyzed, which provides a theoretical basis for the safe transportation of cold and hot crude oil pipelines.

As the oil and gas industry strives to find better gas hydrate management methods, it is necessary to better understand the hydrate formation and plugging trend in multiphase flow.The high?pressure visual flow loop is used to study the formation of carbon dioxide gas hydrate and the properties of hydrate slurry under the flow conditions of complete dispersion and partial dispersion system.The results show that for the fully dispersed phase system with high water content, the contact area between gas molecules and water is larger, and hydrate can be fully generated, which has a great impact on the flow in the loop. For the two systems with different water content, because of the oil?water interface in high water content is damaged more violently, a large amount of hydrate is easier to block the loop.The oil?water interface in low water content can be supplemented after being damaged, so the risk of pipe plugging is low.

The infrared radiation observation experiment were carried out in the uniaxial loading process of four sandstones with different water contents. By studying the quantitative relationship between the infrared radiation information and stress of water?bearing sandstone, the influence of water on the infrared radiation characteristics of sandstone was revealed. The results show that with the increase of water content, the size of sandstone infrared anomaly area was larger, and the infrared anomaly phenomenon was more obvious. The mean value of infrared radiation counts of sandstone increased with the increase of the mean value of stress, and there was a linear relationship between them. After fitting the mean value of infrared radiation counts with the mean value of stress, it is found that the slope increases gradually with the increase of water content. The mean value of infrared radiation counts of sandstone was moderately correlated with water content in compaction and elastic stage, and highly linear correlation in plastic stage and post?peak failure stage (correlation coefficient up to 0.96).

Taking a heavy oil in Shengli Oil Field as the research object,the core was filled with porous medium in the core displacement instrument to simulate the formation conditions,and the aquathermolysis of heavy oil under different reaction conditions was studied.The results shown that the viscosity reduction rate of heavy oil can reach 20.8% only in porous medium by direct displacement,and the viscosity reduction effect is more obvious in porous medium system after the addition of amphiphilic catalyst for reaction.The displacement viscosity reduction rate after reaction in a low?temperature environment of 65 ℃ is 57.9%.However,the reaction in a low?temperature environment leads to an increase in the molecular weight of the asphaltene component,with the relative molecular weight of the asphaltene increasing from 5 244 g/mol to 6 690 g/mol.After the reaction is completed and maintained in a high?temperature environment of 265 ℃,the displacement has a better viscosity reduction effect,with a maximum comprehensive viscosity reduction rate of 96.0%.It provides an important guiding significance for the optimization of operating conditions of heavy oil aquathermolysis in the field application process.

The Bohai Sea is very rich in heavy oil reserves. At present,the thermal recovery rate is so low that the potential for tapping the potential is huge. It is of great practical significance to discuss the feasibility of gas injection exploitation in offshore heavy oil field. Through gas injection expansion experiments and multiple contact experiments, the effects of different gas injection media (CO₂,N₂,natural gas) on heavy oils with different viscosities in the Bohai Sea (general I?1, general I?2?A, general I?2?B) the solubilization,expansion,viscosity reduction effect and mixing mechanism.The experimental results show that the compatibility of CO₂ and heavy oil is better than natural gas and better than N₂, the viscosity reduction rates of CO₂ to the three types of heavy oil are 78%,85%,and 90%,respectively,and the viscosity reduction rates of natural gas to the three types of heavy oil are 29%, 69%,and 62%, respectively. CO₂ injection is more suitable for general I?2?B heavy oil, and natural gas injection is more suitable for general I?2?A heavy oil; the results of multiple contact experiments show that the mass transfer mechanism of CO₂ flooding is dominated by dissolution and condensate, the mass transfer mechanism of N₂ flooding is dominated by extraction and extraction, and the mass transfer mechanism of natural gas flooding is the condensate?extraction balance; in addition, the theoretical minimum miscible pressures are all greater than 43.00 MPa, so it is difficult to form miscible at the displacement front. The research results can provide important basis and technical support for gas injection to enhance oil recovery in Bohai heavy oil fields.

In order to determine the reasonable shape of the patching plate for the corrosion defects in the bottom of crude oil storage tank, this paper used finite element analysis to calculate the changes of the stress value in the corrosion defects after repairing different patching plate shapes, and then investigated the stress distribution and the safety factor value of the patching plate, and finally gave the best shape of the patching plate for the bottom of 20 000 m³ crude oil storage tank in Liaohe oil field. The results show that the best shape of the patching plate is a round patching plate. After repairing the corrosion defect, the stress value in the corrosion defect only decreases with the increase of the radius of the patching plate after the repair of the corrosion defect, and does not change with the change of the depth and radius of the defect. With the increase of the radius of the patch plate, the cost and safety of the patch plate will also increase, the specific size of the patch plate should be developed in accordance with the actual situation of the project. The results of the study can give theoretical guidance to the tank bottom repair from a scientific point of view.

In order to optimize the effect of Bohai oilfield regulation and flooding in B water injection development, the numerical simulation software of CMG reservoir was used to carry out optimization research on the effect of "weak gel+water?based microspheres" combined displacement to improve recovery,and according to the known geological reservoir properties of the oilfield,the actual three?dimensional geological model was established,and the historical fitting was carried out in combination with the previous production history.The factors affecting the modulation effect of single section of plugged weak gel modulation,single section of water?based microsphere modulation and driving and the factors affecting the modulation effect of "weak gel+water?based microspheres" were analyzed and optimized,and the related production indexes were predicted.The results show that the combined modulation effect of "weak gel+water?based microspheres" is significantly better than that of a single segment of plug modulation and driving.The optimal injection process parameters of the modulated blocking agent (weak gel) were selected through numerical simulation:the injection mass fraction is 0.50% crosslinker,the injection amount is 0.000 11 PV,the injection speed of A2H well is 240 m³/d,and the injection speed of A3H well is 200 m³/d.The optimal injection process parameters of the modulator (water?based microspheres) were selected through numerical simulation: the injection mass fraction is 0.30%,the injection amount is optimally 0.003 00 PV,and the injection speed of A2H and A3H wells is about 500~600 m³/d. This design scheme can effectively achieve the purpose of increasing precipitation and oil recovery.

Aiming at the periodic characteristics of severe slug flow an experimental study was carried out through the downward?riser system. Based on the experimental data and the variation of pressure in the pipe, the variation rule of the severe slug flow period was analyzed and verified reciprocally with the calculation model results. It turned out that the flow state in the tube would change under different experimental parameters such as the inclination angle of the downdip tube, the gas phase conversion velocity or the liquid phase conversion velocity. The time of the slug eruption and slug reflux was basically changeless on account of the height of the riser was invariant, so the period of severe slugging depends on the time of slug formation and slug outflow stages. And it was mainly affected by the inclination angle of downward riser, gas superficial velocity or liquid superficial velocity.

The types of volcanic rock reservoir space, reservoir physical properties and the main controlling factors were systematically studied by the method of reservoir physical property experiment, core casting thin section observation and X?ray diffraction test. The results show that the Yingcheng formation volcanic rocks in the Dehui fault depression have strong alteration, and the reservoir space is dominated by dissolution pores and dissolution fractures. The average porosity of tuff and dacite are 12.40% and 7.47%, respectively, and the permeability is less than 1.000 mD, belonging to type Ⅲ reservoirs. Gas?bearing formations can be further identified based on acoustic and resistivity logging methods. Lithology and lithofacies are the main controlling factors for the development of reservoirs, and lithofacies models of extrusive facies, extrusive facies and explosive facies were established in combination with the characteristics of seismic reflections. It provides an important theoretical basis for clarifying the mechanism of volcanic rock formation and the distribution of reservoirs in the study area.

To investigate the structure?function relationship of novel extended surfactants and the mechanisms of reducing interfacial tensions (IFTs) at oil?water interface, the interfacial tension values of 13?P series 13?P（I?C₁₃（PO） _x S,x=5,10,15,20）with different concentrations of NaCl and n?hexane to n?tetradecane at fixed concentration were measured by rotary drop interfacial tension meter. The result indicates that at higher numbers of PO（x=15,20), the n_min values become higher with increasing concentration of NaCl. At lower numbers of PO（x=5,10), the n_min values become lower with increasing concentration of NaCl. It reflects two mechanisms on reducing IFTs: Hydrophilic lipophilic equilibrium effect and hydrophilic hydrophobic group in size matching effect, both of which work together, and the size matching plays a crucial role at lower numbers of PO and HLB dominates at higher numbers of PO.

At present, the thermal recovery method is widely used in heavy oil recovery engineering, in which the high temperature and pressure wet saturated steam is injected into the oil well from the steam injection pipeline, and the heat carried by it is exchanged with low temperature heavy oil, so as to improve the fluidity and permeability of heavy oil and realize recovery. Wet saturated steam dryness is an important parameter affecting thermal recovery effino recognized measurement method existent method. There is no recognized measurement method. At present, the commonly used method is manual measurement, but the measurement results of this method have serious hysteresis. In order to achieve the purpose of real?time monitoring of dryness, a new measuring method, matrix conductance method, under the condition of 10 MPa and 310 °C, a 26×26 wire mesh model was established to measure the dryness of wet saturated steam in a steam injection pipeline with an outer diameter of 76 mm and an inner diameter of 54 mm. The measurement principle of the matrix conductance method is introduced and the dryness algorithm model is established. The electric field simulation was carried out in Ansys Electronics software, the electric field between the layers was analyzed, and the results show that the suitable interlayer spacing is 2 mm. In order to improve the accuracy, the linear interpolation method is used to process the edge, and the actual measurement error is predicted; the overall error after primary linear interpolation is within 2.50%; after quadratic linear interpolation, the overall error is less than 1.10%.

For the under?expansion jet generated after the failure leak of high?pressure pipeline, the Birch theory model was used to replace the actual pipeline leak hole with a pseudo?source. Under different conditions of Hydrogen Blend Ratio (HBR), leak hole size and pipeline running pressure, the concentration field distribution, explosion hazard boundary and explosion hazard range of hydrogen?doped natural gas pipelines after leakage and diffusion were studied. The results show that with the increase of HBR, the aggregation of HDNG after leak diffusion is reduced, the explosion hazard range is gradually decreased and the distal hazard is reduced. However, the increase of HBR shifts the position of explosion hazard boundary downward and increases the proximal hazard. With the increase of leak hole size and pipeline pressure, it will increase the influence area of HDNG after leak diffusion, which will move the explosion hazard boundary position upward and increase the explosion hazard range gradually and increase the distal hazard.

Aiming at the problem of wax deposition in gas well exploitation of offshore HPHT gas reservoir, the gas?liquid?solid and fluid phase equilibrium theory and method of throttling effect principle was used to reveal the wax deposition mechanism of the abnormal high temperature and high pressure gas well, and it was found that wax deposition in high temperature and high pressure gas wells mainly occurs at the position of the oil nozzle where the temperature drops sharply when the wing valve of the gas well is closed. According to the phase equilibrium theory, the phase state of the original formation fluid in HPHT gas well was recovered and characterized, and the phase state change characteristics of gas?liquid?solid three?phase fluid, wax precipitation mechanism and process were described accurately. Based on the phase equilibrium model, the wax location, fluid composition change and the influencing factors of wax deposition were analyzed. It was reasonable to explain that the mechanism of wax precipitation in HPHT gas well is the transient phase transition from gaseous to liquid and then to solid due to the rapid change of temperature and pressure, and the corresponding prevention and control strategies are put forward.

Standalone screen sand control method is one of the most commonly used sand control method for oil and gas wells. With the deepening of oil and gas field development, the working environment and its own conditions of the independent screen sand control system have changed. Affected by high temperature and high pressure, external load, corrosion, fluid erosion and other factors, it is easy to cause sand control failure, which seriously affects the normal production of oil and gas wells. In this paper, long?term mine practice and theoretical analysis are taken to investigate the reasons for sand control failure. It is considered that the main causes of sand control failure are sand control packer failure, sealing mechanism failure and sand control screen tube failure, among which sand control screen tube failure is the most likely to occur. Screen erosion, screen corrosion, geological factors and special operations are the main factors leading to the failure of sand control screen. Through the in?depth analysis of the causes of sand control failure in oil and gas wells, it provides an important basis for taking preventive measures to avoid sand control failure and affecting production.

Most of the oil fields in China have entered the middle and late stage of exploitation, and the well produced fluid has a high water content. FRP pipes are widely used in surface gathering system of oilfield because of their excellent corrosion resistance. At the same time, in order to save heating energy, low?temperature transportation process can be used to transport high water?cut crude oil, but the possible adhesion problem of crude oil is a serious threat to system safety.Therefore, it is important to investigate the interfacial properties of FRP pipe wall/crude oil to reveal the adhesion mechanism of low?temperature transportation of crude oil with high water?cut. The interfacial properties of crude oil on the FRP surface and stainless steel surface were investigated based on the contact angle apparatus. In the aqueous phase, the contact angle of oil droplet on the solid surface increased with decreasing temperature, and the contact angle of oil droplet on the FRP surface is larger than that on the stainless steel surface. The interfacial tension of oil droplet increased with decreasing temperature in the aqueous phase, and compared to the stainless steel surface, the adhesion work of oil droplet on the FRP surface is lower. And the cohesion work of oil droplet decreased with increasing temperature in the aqueous phase. Crude oil is not easy to adhere to the FRP pipe in the gathering system, FRP pipe is more conducive to the implementation of low?temperature transportation process.

As a universal low temperature gathering and transportation boundary condition,the wall sticking occurrence temperature (WSOT) has been widely promoted and applied in the oilfield in the late stage of high water cut development. When the oil gathering temperature is higher than the WSOT, the pipeline operates smoothly, otherwise the pressure drop of most pipelines increases significantly, but some of the pipeline pressure drop changes are not obvious. Through the field cooling experiment, it was found that in the process of the oil gathering temperature gradually decreasing to 6,8,10 ℃ and 12 ℃ below the gel point, the wellhead back pressure has experienced four stages of smooth operation, small fluctuation, low frequency large fluctuation and high frequency large fluctuation, and there are several "restart" processes in the pipeline when the gathering temperature is too low. At the same time, the gas injection experiment under different gas?oil ratio was further carried out, and the results show that when the gas?oil ratio is 40,80,160 m³/t, the pipeline can run stably at the gathering temperature 3,4 ℃ and 6 ℃ lower than the WSOT.

In the environment of CO₂ enhanced recovery (CCS?EOR), the corrosion cracking behavior and mechanism of X70 pipeline steel under different CO₂ pressures were studied. The on?site environment was simulated by using a high?pressure reactor and a simulated produced aqueous solution; the corrosion rate and corrosion mechanism of X70 pipeline steel in the CCS?EOR environment were investigated by electrochemical experiments; the corrosion cracking behavior of X70 pipeline steel under simulated environment was investigated by slow strain rate tensile experiments; finally, the corrosion cracking behavior of X70 pipeline steel under different CO₂ pressure was analyzed by scanning electron microscope. The results show that the corrosion rate of X70 pipeline steel increases with the increase of CO₂ pressure; the corrosion product film produced on the surface of X70 pipeline steel can not protect the metal matrix, and intensify the local corrosion; under the influence of the corrosion product film, the increase of CO₂ pressure makes X70 pipeline steel stress corrosion susceptibility increases; and the corrosion cracking of X70 pipeline steel is also affected by the metal surface cracks.

Energy shortage and environmental pollution have always been the focus of the world's attention. The use of oil, natural gas, and electricity to heat crude oil has high energy consumption and serious environmental pollution. Solar energy, as sustainable and clean energy, has become the focus of researchers from all over the world.Thus, a solar heating crude oil system was designed, and safe and easily available air was selected as the heat transfer fluid. The system consists of a solar receiver, a heat accumulator, a crude oil heat exchanger, and an electro?thermal furnace. The heat receiver receives solar radiation and the temperature rises. The air passes through the heat absorber to obtain high temperature, and the high temperature air enters the heat exchanger to heat the crude oil. A mathematical model for the analysis of the thermodynamic performance of the solar heating crude oil system was established, and the model was verified. Then, the Aspen Plus software was used to conduct thermodynamic analysis of the heatingprocess. The results show that the compressor and the preheater are the components with large exergy loss. When the pressure ratio of the compressor is 2.7, the system reaches its best state. At this situation, the thermal efficiency is 72.35%, the exergy efficiency is 73.89%, and the waste heat recovery efficiency is 72.33%.