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The gas huff-n-puff process has been widely employed in low permeability reservoir development practices. At present, the understanding of synergistic effects of different injection fluids and rock permeability is still limited and is worthy of in-depth investigation. Therefore, laboratory studies on oil recovery performance of supercritical CO2 (scCO2) and N2 huff-n-puff processes in ultra-low (< 0.5 mD), extra-low (0.5-1 mD), and average-low permeability (1-10 mD) core samples were systematically investigated. More effective cycles could be achieved in the CO2 huff-n-puff process than in the N2 process. The CO2 huff-n-puff operation could produce 29.9% oil in the ultralow permeability core, which is obviously higher than 20.2% for N2. With increasing core permeability, the oil recovery ratio for both the scCO2 and N2 huff-n-puff processes increases as well. Laboratory results show oil recovery ratios of 33.1% and 47.3% for the scCO2 process in 0.5 mD and 10 mD cores and 36.3% and 49.1% for the N2 process in 0.5 mD and 9.5 mD cores, respectively. Although the oil recovery rates for the N2 and CO2 huff-n-puff processes are close in the 0.5 mD and 10 mD cores, the effective oil extraction pressure for the scCO2 puff process is found to be 5~10 MPa, which is much higher than 0~2 MPa for the N2 puff process. The study's findings can help provide a better understanding of the oil extraction behaviors in the huff-n-puff process with different injection fluids as well as in different low permeability cores.

A thin-walled spherical shell made of pure iron material is a key part of precision physical experiments. Tool wear is an important factor restricting its geometric accuracy. And tool wear characteristics of curved surface parts are significantly different from those of single-point turning due to the movement of the contact point between the tool and the workpiece. Hence, this article takes the pure iron spherical shell as the research object, which is aimed at investigating the formation mechanisms of flank wear land. Tool wear characteristics are compared between spherical shell turning and end face turning. The results show that uniform flank wear land and notable notch wear occur when turning end face, but notch wear disappears and only flank wear land exists when turning spherical shell. Based on major notch position and minor notch position, a mathematical model is developed to explain formation mechanisms of flank wear land during turning spherical shell of pure iron materials. Theoretical and experimental results show that flank wear land results from the major and minor notch movement. Spherical shell turning and end face turning have the same wear mechanisms, mainly composed of adhesive wear, diffusion wear and oxidation wear.

Based on the theory of small deflection bending of a thin-walled part, a mechanical model of thin-walled planar members under the action of vacuum adsorption was established. Combined with finite-element simulation and testing, the deformation mechanism and law of the thin-walled flat members was studied under the action of vacuum adsorption. Vacuum clamping caused clamping residual stresses on the upper and lower surfaces of the thin-walled flat parts and resulted in torque along the middle surface. When the vacuum clamping was unloaded, the rebound of the thin-walled flat parts that was caused by the torque was the fundamental cause for the clamping deformation. The residual stress and deformation on the surface of the thin-walled flat parts tended to increase and level off with an increase in vacuum. From the initial stage to the stable clamping stage, the radial and tangential stresses in the 200 mm × 2.2 mm workpiece increased by –10 MPa and –27 MPa, respectively, and the relative displacement in the load direction increased by 0.026 mm. Under the effect of vacuum clamping, the maximum deformation capacity of thin-walled flat parts was affected mainly by their initial surface profile error. The stiffness of the workpiece was affected mainly by its thickness; a greater thickness led to a greater stiffness, and a larger vacuum was required for the workpiece to reach a stable clamping state.

Nontransparent flat parts with weak rigidity are widely used in precision physics experiments, aerospace, and other fields in which parallelism is required. However, existing methods cannot meet requirements due to the limitation of measurement size and accuracy. This paper proposes a new method for measuring parallelism of nontransparent flat parts with high accuracy and then builds a submicrometer-level parallelism measuring system. The 3D model of the whole part is reconstructed by thickness and flatness, which are measured respectively. Subsequently, parallelism is evaluated by the principle of minimum directional zone. The method is verified by an experiment with a thin copper substrate sized ⊘ 200 m m × 2.48 m m on the parallelism measuring system. The experiment result shows that the part’s parallelism is 7.41 µm, and the expanded uncertainty of parallelism measurement system is 0.34 µm, k = 2 .

High-precision manufactured thin-walled pure copper components are widely adopted in precision physics experiments, which require workpieces with extremely high machining accuracy. Double-sided lapping is an ultra-precision machining method for obtaining high-precision surfaces. However, during double-sided lapping, the residual stress of the components tends to cause deformation, which affects the machining accuracy of the workpiece. Therefore, a model to predict workpiece deformation derived from residual stress in actual manufacturing should be established. To improve the accuracy of the prediction model, a novel method for predicting workpiece deformation by amending the initial residual stress slightly based on the support vector regression (SVR) and genetic algorithm (GA) is proposed. Firstly, a finite element method model is established for double-sided lapping to understand the deformation process. Subsequently, the SVR model is utilized to construct the relationship between residual stress and deformation. Next, the GA is used to determine the best residual stress adjustment value based on the actual deformation of the workpiece. Finally, the method is validated via double-sided lapping experiments.

The formation of stratigraphy in shallow marine environments has long been an important topic within the geologic community. Although many advances have been made in the field of forward stratigraphic modeling (FSM), there are still some areas that can be improved in the existing models. In this work, the authors present our recent development and application of Sedapp, which is a new nonlinear open-source R code for FSM. This code uses an integrated depth–distance related function as the expression of the transport coefficient to underpin the FSM with more alongshore details. In addition to conventional parameters, a negative-feedback sediment supply rate and a differentiated deposition–erosion ratio were also introduced. All parameters were implemented in a nonlinear manner. Sedapp is a 2DH tool that is also capable of running 1DH scenarios. Two simplified case studies were conducted. The results showed that Sedapp not only assists in geologic interpretation but is also an efficient tool for internal architecture predictions.

The precision of cutting simualtion is determined by constitutive models, friction models, and thermal property models etc. In this study, the cutting simualtion model of pure iron with high precision is established. The power-law based material constitutive model has been developed. The high-temperature hardness tests have been carried out to acquired the item of thermal softening. The SHPB tests have been implemented to fit the items of strain hardening and strain rate strengthening. The friction model between workpiece and cutting tool has been developed by orthogonal cutting tests. The thermal property models including specific heat capacity and thermal conductivity modelshave been developed by laser flash diffusivity apparatus, which have been expressed as the functions of temperature. Orthogonal cutting tests with a wide range of cutting and cutting tool parameters have been designed, which is conducive to collecting the cutting temperature of the specific location of the cutting area. The simulated and experimental results have been compared comprehensively in the items of cutting forces and cutting temperature to verify the precision of the simulation model. It is found that the average errors of cutting force, thrust force, and cutting temperature are 5.07 %, 7.73 %, and 9.15 %, respectively, which fully proved the precision of the simulation model.

The Gudong oil field offers a unique opportunity to characterize thin meander-belt sandstones in an area with a dense network of wells (100 wells per square kilometer or 259 wells per square mile). The goal of this study is to evaluate the evolution of subsurface meander-belt complexes through analysis of their overall stratigraphic architecture defined by the spatial distribution of sedimentary structures and stratigraphic surfaces of stacked point-bar sandstones, which severely affect the potential for producing the remaining oil in these mature oil fields. Five types of superposition structures, which reflect the shapes of the point-bar sand bodies in the superimposed regions between point bars, are identified by combining stacked and migrated seismic profiles, seismic forward models, and wire-line log profiles. The point bars belong to different stages of channel stories through the analysis of their superimposed structures and the vertical offset of the basal surfaces of point-bar sandstones. Five channel stories are recognized in the thin meander belt. They can be distinguished by the analyses of stratal slices, wire-line log profiles, and tracer data. These channel stories were found to exhibit unique morphometric characteristics: the thickness and width of the channel stories changed with the discharge of the paleoriver; the widths of the later channel stories became more stable through time and were not affected by the flow discharge during the deposition of the channel stories. The identified superimposed structures between subsequent point bars and morphometric parameters of channel stories are useful for the modeling of the target reservoir.

Foam fluid is widely used in petroleum industry, so the behavior of foam fluid flow in porous media directly affects the application effect of foam. However, the foam flow pattern in porous media is difficult to established because of its dynamic change of interface structure and unpredictable boundary condition. In this work, the transient structural changes of foam fluid in porous media are quantitatively characterized, and the flow behavior is analyzed based on fractal theory and visual experiments. Firstly, the foam fractal characteristics are verified and the fractal dimension is calculated. Results shows that the foam fractal dimension is between 1.5~2.0, and the foam flow can be divided into three stages: gas-liquid two-phase flow, foam unstable flow stage and foam stable flow stage. In addition, the evaluation indexes of foam performance in porous media are proposed to evaluate the influencing factors. Namely, the fractal dimension in stable stage Dfoam-s and the time needed to reach stability Ts....

s In this paper, experiments were conducted to study the effect of weak magnetic fields on the freezing process of deionized water and physiological normal saline. The results show that different magnetic field strengths have different effects on aqueous solutions. Only a certain strength of the magnetic field will have a positive effect on the freezing process of the aqueous solution, and generally speaking, the effect of the magnetic field on the normal saline is better than that of deionized water. When the magnetic field strength is 150G, the magnetic field has a positive effect on the supercooling degree and the supercooling time of the saline. In the beef freezing experiment, it was found that the magnetic field can not only promote the freezing process of beef but also inhibit the freezing process. Whether a fan is added will also affect the freezing effect of the magnetic field on the beef.The magnetic field strength of 40G and 50G has a significant promotion effect on the freezing process of beef, while the magnetic field strength of 100G~150G has a significant inhibitory effect.

The interactions between gas and liquid have an important role in energy extraction and storage. For example, the interfacial tension (IFT) between the two phases has an important effect on developing crude oil in low-permeability reservoirs and compressed air energy storage in aquifers (CAESA). For the mechanism of two-phase fluid interaction in energy extraction and storage, the study of gas-liquid interface properties is carried out in the paper. Firstly, molecular dynamics simulations are used to study the molecular simulation progress of nitrogen and water under different environmental conditions, and the effects of different temperatures and pressures on IFT are studied. The results show that IFT increases with the temperature increase at constant pressure. When the temperature is constant, an increase in the pressure of the system will decrease the surface tension of the system. Then the effect of IFT on the distribution of gas-liquid phases in the pores of low-permeability rocks is studied by digital core technology and simulation methods. The results show that the lower the IFT of gas and liquid is, the better the displacement effect is and the higher the recovery ratio is in the low-permeability rocks. This study analyzes the IFT and influencing factors between the gas-liquid two-phase interface, and it guides the efficient development and utilization of energy extraction and energy storage.

Titanium alloys are widely used in industrial fields because of their superior characteristics, but they also have disadvantages leading to fretting fatigue (FF) damage. The silver-based composite films were deposited on a Ti6Al4V alloy substrate using ion-assisted magnetron sputtering for improving the fretting fatigue (FF) resistance of a Ti6Al4V alloy. The surface morphology was characterized by atomic force microscopy (AFM), and micro-structure was characterized by X-ray photoelectron spectroscopy measurements (XPS), X-ray diffractometry (XRD), and transmission electron microscopy (TEM), respectively. The bonding strength and toughness of films were analyzed using a repeated press–press test system that was manufactured in-house. The FF resistance of titanium alloy with the silver-based composite films was investigated using home-made FF devices. The results showed that the FF resistance of the titanium alloy was improved by the Ag-TiN composite films, which were fabricated with an Ag solid lubricating film doped with a hard TiN phase (60–80 at.% Ag). This is attributed to the fact that the composite films had better comprehensive strength-toughness behavior, friction lubrication property, and high bonding strength. However, when the atomic fraction of Ag in the composite film was larger than 90%, it became difficult to form the TiN phase, and it failed to improve the comprehensive strength-toughness behavior of the composite film.

Thin copper substrates with high flatness and surface integrity are highly required in precision physical experiments. Normally, fly cutting is used to fabricate the substrates. However, the flatness is difficult to be guaranteed after disassembly due to the clamping and machining stresses which are induced on the substrates. Besides, the surface integrity is hard to be improved because of the severe subsurface deformation and high residual stress. To solve the problem, a new process chain composed by double-sided lapping and chemical mechanical polishing (CMP) is proposed to acquire both high flatness and surface integrity on thin copper substrates. In the new process chain, double-sided lapping is employed to achieve high flatness and uniform distribution of surface residual stress, while double-sided CMP is adopted to obtain the ultra-smooth surface without damage and maintain the flatness. The results show that flatness superior to 4 μm peak-to-valley (PV), and surface roughness less than 3 nm Ra are obtained. Moreover, both surfaces are damage-free with low surface residual stresses.

A clear understanding of the diffusion characteristics between oil and CO2 phase in the miscible front is substantial to operate a successful CO2 miscible flooding process. However, there are few studies on diffusion characteristics of CO2/hydrocarbon systems under the multi-contact miscible state. In this paper, the Dynamic Pendant Drop Volume Analysis (DPDVA) technique is employed to obtain the diffusion coefficients of the CO2/n-hexadecane system over the Minimum Miscibility Pressure (MMP) conditions. Based on the oil droplet volume variation histories, a simplified mass transfer model adapted to the oil-gas miscibility condition is proposed. For the first time, the diffusion coefficients of a miscible CO2/n-hexadecane system at temperature range of 26.9–79.6 °C and the pressure range of 7–19 MPa were measured. It is found the diffusion coefficients close to the MMP condition have the same magnitude values compared to the literature reported results in immiscible conditions, indicating a nearly stable diffusion rate before system miscibility and in the meantime validating the experimental technique employed in this paper. On the other hand, larger diffusion coefficient appears under lower temperature and higher pressure conditions under miscible conditions, and a clearly linear relationship is observed between the diffusion coefficient and the system pressure. It is expected the study can fill some gaps in the research field of oil/gas miscible diffusion characteristics and help optimize the gas injection miscible flooding processes.

The properties of foam fluid are substantially determined by its interfacial dynamics changes during foam transport. In this research, a foam flow simulation model based on the level set method and the N–S equation with surface tension term is established to simulate the dynamic interface evolution mechanism of group foam and individual foam from various aspects such as drainage process and foam migration in porous media, coalescence and Jamin effect. The results show that the foam life decreases linearly with the logarithm of the surface tension and enhances linearly with the liquid viscosity. For foam transport in porous media, both flowing foam and trapped foam exist, and the pressure fluctuates at a certain pressure value and the best foam structure is achieved at the optimum conditions with the optimum values of gas-liquid ratio, surface tension, and porosity being 1:1˜3:2, 0.1˜0.3, and 44.4%, respectively. Besides, the temporary blocking effect of foam has been verified. During the foam coalescence, foam gradually evolves towards minimum interfacial energy with oscillating and gradually decreasing foam volume. During the process of the foam passing through the throat, the maximum pressure occurs when the front end of the foam reaches the narrowest point, and the minimum pressure occurs when half of the foam passes through the narrowest point. The maximum pressure elevates linearly with the surface tension and the inverse of the throat radius.

In relation with the potential applications of CO2 foam technology on Enhanced Oil Recovery and CO2 geological storage, the foam assisted CO2 displacement process in a surfactant solution and oil pre-saturated porous medium is experimentally investigated with special attention on the dynamic foam propagation behavior in the entrance region of porous media. Computational Tomography (CT) imaging is employed to visualize the transient CO2 foam sweep process and the dual-energy CT measurement is performed to obtain the dynamic three phase saturation distributions along the sample core. Studying parameters include the comparison with N2 foam, system backpressure and the porous medium permeability. It is found foam could push most of the liquid phase in the latter part of the porous media but leaves the forepart of the sample less flooded, showing a clear entrance effect of foam flooding process. Compared to CO2 foam, N2 foam displacement process shows higher liquid phase saturation in the entrance section and presents less oil recovery rate. Elevating system backpressure to 1.0 MPa leads to less pressure drop for CO2 foam flooding process without compromising the oil phase sweep efficiency. The CO2 foam flooding process in lower permeable medium shows higher pressure drop and higher oil recovery rate. The mechanisms for the inlet behavior of the foam displacement processes have been scrutinized based on good qualitative and quantitative agreement of the experimental and numerical results with the stochastic bubble population balance model.

Numerical investigations were carried out with special attentions on the inlet and outlet behaviors of foam flow process in a homogeneous porous media with confined entrance and exit boundaries. The Stochastic Bubble Population (SBP) balance model, which usually involves two parameters of the bubble generation rate Kg and the maximum bubble density n∞ for bubble number prediction, was employed to study the dynamic foam generation and development process in porous media. With introduction the Kfp parameter to take into account the foam phase relative permeability reduction effect, the control equations of the two-phase flow process in a two-dimensional computational domain were solved with the IMPES algorithm and the inlet and outlet behavior of the foam displacement process were scrutinized based on detailed analysis of the bubble density, water phase pressure and water phase saturation distributions in porous medium. Numerical results showed a clear entrance effect of higher water saturation, lower pressure gradient and developing bubble density in the inlet region of the porous media in the transient foam displacement process, whereas the confined exit results in elevating water saturation and decreasing pressure gradient towards the outlet of the core. Parametric studies on Kg, n∞, Kfp and inlet & outlet sizes D indicate higher bubble generation rate could remarkably suppress the entrance region in the foam seepage process, while the higher maximum bubble number did not lead to obvious change of the foam flow behavior in the inlet and outlet region, although it could produce higher absolute values of bubble density and pressure drop along the core. With lower Kfp values, the strong foam flooding behavior could be properly predicted with much higher pressure drop and lower water saturation. Two dimensional numerical results at various inlet and outlet sizes clearly show the confined geometry effect on foam flow characteristics with smaller sizes corresponding to longer inlet and outlet regions. Computational domain and numerical results were validated through comparisons with corresponding experimental setup and CT measurement results. It is observed that, the numerical simulation could reproduce not only qualitatively but also quantitatively the experimentally obtained water saturation distribution and pressure drop result. It is concluded that the mechanistic stochastic bubble population model could be reasonably employed on prediction of the inlet and outlet behavior in the transient foam flow process in the homogeneous porous media.

Although CO2 huff-n-puff process has been widely employed as an efficient oil recovery and carbon storage technique in unconventional reservoirs, it suffers from the disadvantages of lack of availability near a large field and formation leakage due to the high CO2 mobility. Carbonated water injection (CWI) has been extensively studied as the alternative of CO2 injection process, but the laboratory studies concerning on CW huff-n-puff process is scarcely reported. In this paper, the oil recovery characteristics of CW huff-n-puff process has been scrutinized under reservoir conditions of 28 MPa and 65 °C together with NMR tests to reveal the oil mobilization rules in the tight cores. Comparative studies on CO2 huff-n-puff and water huff-n-puff process were also performed. It is found 4 rounds of CW huff-n-puff processes could recover considerable amount of 36.2% of the oil from the tight core. Although the recovery rate is lower than 55.4% for CO2 process but it is much higher than 14.4% of the water process. NMR T2 results reveal the oil in the large size pores of the tight cores are mobilized and recovered in early huff-n-puff cycles, whereas the oil from small size pores are collected in the later stage of the CW and CO2 huff-n-puff processes. The research results indicate the CW huff-n-puff process is promising for tight reservoir development.

Ultrasonic elliptical vibration cutting (UEVC) is a promising hybrid machining technique for ultra-precision cutting. In this paper, an available and propagable design of the UEVC device is proposed through detailed mechanism analysis. The one-dimensional longitudinal vibration theory and Timoshenko beam theory are utilized and the frequency equations of the designed structure are proposed and solved by analytical solution. Thus, the preliminary size parameters of the proposed structure are obtained according to theoretical analysis, and then appropriate structural adjustment and dimensional parameters optimization are performed based on the modal analysis. The resonance frequencies of the longitudinal and bending vibrations can be adjusted to be the same, and two installation holes are determined near the wave node of the second longitudinal vibration mode and the fourth bending mode. Then the resonant frequency and tool trajectory of the manufactured prototype are verified by laser vibrometer, which are consistent with the design. Cutting experiments on pure iron with the proposed device shows that the mirror surface is achieved with nearly no tool wear. Therefore, the proposed design of the device which works in these two resonant modes can be applied for ultra-precision elliptical vibration cutting.

Thin-walled parts are widely used in shock wave and detonation physics experiments, which require high surface accuracy and equal thickness. In order to obtain the wall thickness of thin-walled spherical shell parts accurately, a new measurement method is proposed. The trajectories, including meridian and concentric trajectories, are employed to measure the thickness of thin-walled spherical shell parts. The measurement data of the inner and outer surfaces are unified in the same coordinate system, and the thickness is obtained based on a reconstruction model. The meridian and concentric circles’ trajectories are used for measuring a spherical shell with an outer diameter of Φ210.6 mm and an inner diameter of Φ206.4 mm. Without the data in the top area, the surface errors of the outer and inner surfaces are about 5 μm and 6 μm, respectively, and the wall-thickness error is about 8 μm with the meridian trajectory.

Thin copper substrates in precision physical experiments are commonly machined by double-sided lapping to obtain high flatness. However, the flatness is limited by the accuracy of lapping plate, process vibration and so on in double-sided lapping process. Hence, magnetorheological finishing (MRF) with its good performance on profile modification is employed to improve the flatness. Nevertheless, thin copper substrates, which are sensitive to the stress, deformed easily with uneven material removal on the surface. In this paper, MRF is conducted on machining thin copper substrate for the first time considering deformation induced by stress. A finite element model is established to evaluate the deformation by residual stress, and the results show that the deformation tends to be more serious with the increase of the material removal. According to the simulation results, the material removal is optimized considering both deformation and efficiency, and a series of experiments are conducted on a Φ100×2.8 mm workpiece to verify the simulation results. The experimental results show that the flatness is further improved from peak to valley (PV) 6.6 μm to PV 2.3 μm with optimized processing parameters. Hence, the feasibility of magnetorheological finishing on thin copper substrate is demonstrated.

The formation of stratigraphy in shallow marine environments has long been an important topic within the geologic community. Although many advances have been made in the field of forward stratigraphic modelling (FSM), there are still some shortcomings to the existing models. In this work, the authors present our recent development and application of Sedapp: a new non-linear open-source R code for FSM. This code uses an integrated depth-distance related function as the expression of the transport coefficient to underpin the FSM with more along-shore details. In addition to conventional parameters, a negative-feedback sediment supply rate and a differentiated deposition-erosion ratio were also introduced. All parameters were implemented in a non-linear manner. Sedapp is a 3D (2DH) tool while also capable of 2D (1DH) scenarios. Two simplified case studies were conducted. The results show that Sedapp can not only assist in geologic interpretation, but is also an efficient tool for internal architecture predictions.

To investigate the mechanism of surface modification of pure iron by atmospheric pressure plasma treatment (APPT), the surface wettability of pure iron was characterized by using a contact-angle measuring instrument, and the mechanical properties of pure iron were measured by a tensile testing machine and nanoindentation instrument. Molecular dynamics simulations were used to explain the modification mechanism of the surface wettability and the mechanical behavior of pure iron by APPT. The experimental results show that pure iron treated by APPT is superhydrophilic, with reduced tensile strength and surface hardness. This result agrees with the molecular dynamics simulation, which shows that the pure iron material hydrophilicity improved after APPT. The behavior was attributed to the formation of hydrogen bonds on the surface of the pure iron after APPT. The surface binding energy of the pure iron material increased between the water molecule and the residual N atom that was induced by APPT. The N atom that was introduced by the APPT led to Fe bond fracture, and the N atom reduced the Fe bond strength, which resulted in a reduction of material yield strength and microhardness.