Search Results (276)

Gas well production optimization is an effective way to improve the efficiency and economic performance of natural gas development. Multiphase flow in wellbores and reservoir seepage make the process highly nonlinear, strongly coupled, and complex. Traditional simulation software can provide accurate predictions, but the high computational cost limits its use in iterative and large-scale optimization. This paper presents an integrated framework that combines numerical simulation, surrogate modeling, and intelligent optimization for gas well production parameter optimization, particularly under continuous gas lift conditions. A simulator is used to generate datasets, which are then used to train a neural network surrogate model for fast prediction of gas well production response. An improved particle swarm optimization algorithm is applied to perform global search and obtain the optimal production parameter combination. Results show that the surrogate model can reliably replace the simulator in repeated prediction tasks while substantially reducing computational cost, and the improved algorithm performs better than traditional methods in both convergence speed and optimization accuracy. Case studies confirm that the optimized parameters effectively increase gas well production. The proposed framework provides an efficient and practical approach for intelligent production optimization in gas wells under complex wellbore multiphase-flow conditions. Full article

Bed-separation grouting filling mining is a damage-mitigation mining technology characterized by non-interfering mining and filling operations, low cost, and high efficiency. To recover coal resources from the 3801 working face located beneath a surface gas station in a Shanxi coal mine, this study first analyzed the maximum allowable deformation values for the gas station’s canopy, business hall, and oil storage tanks. Second, the feasibility and safety of bed-separation grouting filling mining at the 3801 working face were investigated using physical similarity modeling and the probability integral method. Finally, a field application of this technology was carried out at the 3801 working face. The results show that: (1) After the successive mining of the 3802, 3803 and 3801 working faces, the No. 17 bed separation was finally preserved above the 3801 working face. It is located in the upper part of the water-conducting fracture zone and has a thick impermeable isolation layer. (2) Physical similarity simulation and numerical simulation (3UDEC) of bed-separation grouting filling mining at the 3801 working face indicate that the underlying strata are effectively compacted after mining, and both overlying strata movement and surface subsidence above the grouting zone are significantly reduced. (3) The probability integral method was adopted to predict surface movement and deformation induced by mining at the 3801 working face (bed-separation grouting filling mining), the 3802 working face (fully mechanized top-coal caving mining) and the 3803 working face (full-seam mining in a single lift). All surface movement and deformation indices satisfy the surface deformation control requirements for the gas station. (4) After completion of the overburden bed-separation grouting filling project at the 3801 working face, the measured surface movement and deformation values during and after mining are all below the allowable deformation limits. No large deformations or cracks occurred in gas station structures including the canopy, business hall and oil tank farm. The protection effect is satisfactory, and the gas station has maintained normal operation throughout the mining period. Full article

Gas-lift reverse circulation drilling technology is one of the typical “bottom-hole negative pressure” drilling technologies. This technology can significantly reduce wellbore circulation pressure loss, alleviate the bottom-hole pressure holding effect, and effectively lower the probability of lost circulation. The core theory underlying this technology is multiphase flow in the wellbore. Based on gas–liquid two-phase flow theory, this paper develops a method for calculating bottom-hole pressure during gas-lift reverse circulation. The effects of key operational parameters on bottom-hole pressure were analyzed. The results show that bottom-hole pressure decreases as gas injection rate increases and as the gas injection point deepens. Moreover, the deeper the gas injection point, the greater the pressure reduction. Compared with the results from gas-lift reverse circulation drilling design and monitoring software applied to a shale gas well in southern Sichuan, the two sets of data differ by approximately 3%. The proposed calculation method can predict bottom-hole pressure under gas-lift reverse circulation conditions, overcoming the low accuracy of empirical formulas traditionally used in such operations. This has significant implications for advancing gas-lift reverse circulation technology in oil and gas well drilling. Full article

Volcanogenic Massive Sulfides (VMS) are considered major base (Cu-Zn±Pb) and precious metal (Au and Ag) sources with paramount contribution in the development and evolution of mankind through the ages. They are characterized by variable ore mineralogy and geochemistry, largely attributed to the variety in the geotectonic regime of formation (both divergent and convergent margins) and the variability in the host lithologies. Several VMS types are distinguished depending on the type of volcanism and host-rock lithology. The lens-shaped-to-stratiform bodies composed of fine-grained sulfides, usually accounting for more than 60% of the rock mass, have been exploited since prehistoric times. Recent studies reveal that VMS continue to be formed in deep marine settings and along plate margins on the ocean floor. Besides base and precious metals, nowadays, VMS are considered significant sources of critical and strategic metals, such as Co, Ni, Ga, Ge, In, Bi, As, Sb, Se, Mo, Cd, Sn, Hg, Tl and Bi, particularly after extensive research of the ocean floors in the years following World War II (WWII). Since the late 1970s, the potential of VMS has been further enhanced after the successful deep-sea mining (DSM) pilot tests, with the pipeline-lift mining system considered the most suitable for seabed massive sulfide (SMS) recovery. Full article

Hydrogen-enriched fuel injection in staged gas-turbine combustors is commonly achieved through jet-in-crossflow (JICF) configurations, where flame stabilization is governed by a local balance between flow-induced strain/mixing and chemical reaction rates. This work investigates turbulent reacting JICF relevant to staged combustion conditions using high-fidelity simulations with adaptive mesh refinement (AMR) and differential-diffusion effects together with Lagrangian particle statistics. Chemistry model uncertainties are incorporated by using a projection method that maps uncertainty estimates from detailed mechanisms into the model used in this work. Results show that the macroscopic flame topology remains in a stable two-branch regime (lee-stabilized and lifted) and is primarily controlled by the jet momentum–flux ratio J. Visualization of the normalized scalar dissipation rate reveals that the flame front resides on the low-dissipation side of intense mixing layers, occupying an intermediate region between over-strained and under-mixed regions. While hydrogen content does not significantly change the global stabilization mode for the cases studied, uncertainty analysis reveals composition-dependent differences that are not apparent in the mean behavior alone. In particular, visualization in Eulerian (χ, T) state-space analysis and particle statistics conditioned on the stoichiometric surface demonstrate that higher-hydrogen cases observe a lower scalar dissipation rate and exhibit substantially reduced variability in OH production under kinetic-parameter perturbations, whereas lower-hydrogen blends experience higher dissipation and amplified chemical sensitivity. These findings highlight that, even in globally similar JICF regimes, the hydrogen content can modify the local response of the flame to kinetic-parameter uncertainty, motivating uncertainty-aware interpretation and design for hydrogen-fueled staging systems. Full article

Gas–liquid bubbly flow in horizontal pipes is widely encountered in energy and process systems, where accurate prediction of phase distribution is essential for safety and performance assessment. In Euler–Euler two-fluid simulations, the predicted void fraction profile is highly sensitive to the choice of interphase force closures. In this study, the effects of drag, lift, wall lubrication, and turbulent dispersion forces on the void fraction distribution in horizontal bubbly flow are numerically investigated using a Euler–Euler two-fluid model. Simulations are performed for three experimental cases covering a wide range of bubble Reynolds numbers (Re_b = 55, 140, 6283), and the predicted void fraction profiles are compared with available experimental data. The results indicate that the void fraction profile is insensitive to drag force model selection. In contrast, the lift force plays a dominant role in controlling the lateral migration of bubbles and the formation of the upper-wall void fraction peak. The wall lubrication force significantly influences the near-wall phase distribution, with different models exhibiting varying levels of agreement with the experimental data at different bubble Reynolds numbers. Turbulent dispersion is found to be essential under horizontal conditions, and the Lopez-de-Bertodano model is robust for all cases. The present results provide insight into the relative roles of different interphase forces in shaping the phase distribution in horizontal bubbly flow. Full article

As a branch of nondestructive testing (NDT), Pulsed Eddy Current Testing (PECT) is characterized by its wide frequency spectrum and high penetration depth. After years of development, it has been widely applied to defect detection and material characterization of key components in industries such as petrochemicals, new energy, and aerospace. With the large-scale application of new energy sources like liquefied natural gas (LNG), methanol, and liquid hydrogen, the demand for NDT of non-ferromagnetic materials (e.g., austenitic stainless steel) has surged. However, challenges such as electromagnetic leakage caused by low magnetic permeability and the lift-off effect induced by protective layers impose stricter requirements on inspection technologies, driving the evolution of PECT towards adaptability in complex scenarios. This paper systematically reviews the latest advances in PECT technology, covering detection sensors, modeling methods, detection signal processing, and engineering applications. With a particular emphasis on research outcomes from the past decade, this paper also proposes potential directions for future development, aiming to provide a reference for innovative research and the industrial promotion of PECT technology. Full article

The oil and gas industry is increasingly challenged by the global transition toward renewable energy systems aimed at reducing carbon emissions. Nevertheless, opportunities remain to mitigate the environmental impacts associated with ongoing oil and gas operations. One of the major environmental challenges in this sector is the extensive use and treatment of water. Membrane-based separation has emerged as an effective technology for oil–water separation due to its ability to overcome limitations associated with conventional treatment methods. This study aims to build a CFD model to investigates the influence of operational hydrodynamic conditions on membrane separation, including transmembrane pressure 202, 101, 50, 10 kPa, crossflow velocity 0.08 m/s, 0.116 m/s, 0.33 m/s, 0.66 m/s, and oil droplet diameter 1, 5, 10, 50, 100 µm, on membrane performance in addition to different oil concentrations 1%, 2%, 4%, 8% using Eulerian-Eulerian multiphase model. This is done by experimentally extracting the membrane water resistance, which is found to be 6.46 × 10¹⁰ (1/m) and using it as an input to the numerical model. The results indicate that permeate flux is primarily governed by transmembrane pressure, in agreement with Darcy’s law, while fouling development along the membrane length is mainly influenced by crossflow velocity and oil droplet size. Where it was found that for large droplets 100 µm and 50 µm the buoyancy forces were large enough to lift the oil droplets away from the membrane at velocities 0.08, 0.16 and 0.33 m/s while smaller droplets remained at the membrane surface In addition, backward diffusion, which has been emphasized in previous studies, was found to play a comparatively minor role in the present numerical analysis. Full article

The present numerical study simultaneously investigates the aerodynamic performance, shape optimization, and aeroacoustic characteristics of modified leading-edge wavy wings for the NACA 0020 airfoil. Unlike conventional passive flow-control approaches, the present study proposes a collaborative vortex–slot control strategy, where streamwise vortices induced by a wavy leading edge interact constructively with momentum injection from upper-surface slot channels. Flow field is analyzed at a Reynolds number of 290,000 and various angles of attack (AoA) utilizing Computational Fluid Dynamics (CFD). Three leading-edge wavy wing configurations, namely A3L11, A3L40 and A11L40, are examined and further modified by introducing streamwise slots near the leading edge on the upper surface of the wing. Three slot diameters (0.07c, 0.10c, and 0.13c) are examined at a constant draft angle of 7.5°, which represents the inclination of the slot relative to the wing surface. The numerical results are validated against experimental data available in the literature. The findings indicate that the A3L11 configuration with a 0.07c slot diameter, as well as the A11L40 configuration at high angles of attack, outperform the baseline wavy wing. This improvement is attributed to the slotting mechanism, which enhances surface suction and streamwise momentum, thereby improving boundary-layer behavior. An increase in aerodynamic efficiency, quantified by the lift-to-drag ratio, is observed at 20° AoA for all configurations. To further enhance performance, shape optimization is performed by optimizing the slot diameter and the distance between the chord line and the slot center using a Genetic Algorithm (GA), with the A11L40 configuration at 20° AoA identified as the optimal design. The optimized configuration yields an overall aerodynamic performance improvement of approximately 27.76% compared to the smooth wing, while broadband aeroacoustic source modeling indicates a relative reduction in predicted noise-source intensity relative to the baseline modified wing. The results are presented through combined quantitative metrics and qualitative flow analyses, demonstrating the potential applicability of the proposed optimization framework to low-Reynolds-number aerodynamic and aeroacoustic design problems, such as those encountered in small-scale air vehicles, bio-inspired wings, and noise-sensitive systems. Full article

Distributed acoustic sensing sends laser pulses along a fiber optic cable and analyzes the backscattered light to identify acoustic signals along the entire fiber. Liquid slugs were produced in a 427 m vertical test well using surface-controlled gas lift valves. To enhance DAS monitoring, pressure pulses were induced by multiple acoustic shots from a fluid level gun. Visualization of the responses through frequency band energy plots and unfiltered phase shift measurements permitted tracking slug movement and estimating parameters such as velocity, location, and body length. The results demonstrate that DAS stimulated with acoustic pulses can effectively track liquid slugs in real-time. We observe that relying solely on flow-induced noise in multiphase flow environments may not provide sufficient signal strength for slug detection. Applications include real-time detection of liquid slugs for improved well monitoring and flow management. Full article

Vertical takeoff and landing (VTOL) aircraft must balance the conflicting demands of hover and cruise performance. To address the lack of integrated design methodologies in the existing literature, a unified design-optimization framework is presented, coupling high-fidelity CFD simulations with a genetic algorithm to refine a gas-driven thrust fan (GDTF) VTOL nacelle. Key geometric parameters—fan pressure ratio pressure ratio, fan tilt, nozzle angle, tail inclination, and tip shape—were varied in a comprehensive parametric study to maximize lift-to-drag ratio and maintain constant mass flow. The optimization reveals that a nearly horizontal fan axis maximizes cruise efficiency (${\displaystyle \frac{L}{D}}\approx 2.98$), a nozzle angle of about $22°$ offers the best lift-vs-drag compromise during transition, and refining the tip geometry yields a $10$–$20\%$ performance boost. To validate the numerical predictions, a 1:1.05 scale VTOL nacelle model (fan diameter $D = 0.42 \mathrm{m}$) was fabricated and tested in a low-speed wind tunnel at $52 {\displaystyle \frac{\mathrm{m}}{\mathrm{s}}}$ ($Re \approx 5 \times {10}^6$, turbulence intensity ≈ 2%). Total-pressure probes at the intake exit plane and static taps along the inner cowl wall provided detailed pressure distributions, from which exit Mach number, velocity and the equivalent flow coefficient φ (≈0.68 under test conditions) were derived. Oil-flow visualization on the external cowl surface confirmed smooth, attached streamlines with no large separation bubbles. This dual validation combining surface-flow visualization and pressure-recovery mapping demonstrates the accuracy and reliability of the proposed simulation methodology. By successfully bridging detailed CFD with genetic-algorithm-driven design and validating against comprehensive wind-tunnel measurements, this integrated approach paves the way for next-generation VTOL configurations with longer range and lower fuel consumption. Full article

Potato harvesters operating in hilly and mountainous areas are often subjected to harsh working conditions such as high temperature, sun exposure, and high torque excavation. Due to the fluid sealing characteristics, closed loop hydraulic systems are prone to high temperatures during long-term continuous operation, resulting in a decrease in fluid viscosity, poor lubrication, severe wear, and power attenuation. This study investigates the hydraulic system of potato harvesters in hilly terrain, systematically analyzing its energy transfer process and identifying key heat-generating components. Based on an optimization strategy that extends the flow path of high-temperature fluid within the tank, four distinct tank designs were proposed. Computational fluid dynamics (CFD) and thermodynamic simulations were conducted to evaluate their heat dissipation performance, followed by full-machine validation testing. Results indicate that the walking and lifting systems are the primary heat sources. The dual pump contributes the highest proportion of heat (52.07%), followed by the walking motor (20.54%). The heat exchanger dissipates 72.91% of the heat, while the hydraulic oil tank accounts for 14.93%. Among the four tank designs, Tank 0 exhibited the fastest temperature rise, reaching a thermal equilibrium of 83.27 °C, whereas Tank 1 had the lowest equilibrium temperature (78.62 °C). Heat dissipation efficiencies for the tanks were 7.8%, 12.9%, 10.1%, and 11.6%, respectively. The residual gas volume fraction decreases significantly as the bubble diameter increases, due to the higher buoyancy and faster rise velocity of larger bubbles, which leads to shorter residence times and more effective precipitation. Tank 1 achieved the lowest equilibrium temperature, indicating the best thermal efficiency. Tank 3 showed the best overall degassing performance, particularly for medium-to-large bubbles. Tank 1 was selected as the optimal final design because it could offer an excellent balance, with very good cooling and competitive degassing (especially for small bubbles). Field tests confirmed a 14.8% reduction in thermal equilibrium temperature for Tank 1 (75.6 °C) compared to Tank 0 (88.7 °C). Simulation and experimental data showed strong agreement, with maximum errors of 9.2% for return fluid temperature, 12.7% for cooling return fluid temperature, 9.7% for pressure, and 8.5% for flow rate. Average errors remained below 8.4% for pressure and 7.6% for flow rate. These results validate the accuracy of the simulation model and the effectiveness of the tank optimization method. Full article

Addressing the challenges of poorly developed fractures and low individual well water yields within the Tianjin Ordovician–Wumishan carbonate thermal reservoir, alongside the rapid reaction rates and short effective distances observed during conventional acid fracturing operations, this study employed an XRD core analysis to confirm reservoir calcite contents exceeding 90%. Based on this finding, an acid formulation incorporating a 2% SPR-12 retarder was developed. High-temperature high-pressure reactor experiments demonstrated that this system successfully reduced the acid–rock reaction rate from 0.122 g·min⁻¹·cm⁻² to 0.037 g·min⁻¹·cm⁻² and increased the retardation efficiency from 34.07% to 68%. This significantly extended the acid penetration distance and enhanced the fracture network connectivity within the reservoir. The field trial conditions informed the parameter optimization via E-StimPlan^® 3D simulations, ultimately determining that a fracture extension of 400 m could be achieved with a 20 MPa breakdown pressure. Conductivity experiments validated that a flow rate of 1.3 m³/min generated pillar-supported wormhole structures, yielding a final conductivity of 46.8 μm²·cm. The pumping pressure plummeted from 20 MPa to 1 MPa, confirming effective fracture network communication. Gas lift backflow for 20 h mitigated secondary precipitation risks. After implementation, the water production rate of this well increased from 12.33 m³/h to 95 m³/h, with a dynamic water level of 158.85 m. The water temperature rose from 62 °C to 88 °C and remained stable. Compared to current acidizing and fracturing methods applied in geothermal wells, the new acid fluid system and process have increased the geothermal production capacity by 275.8%, while reducing acid consumption by 50%, providing critical technological support for the efficient development of carbonate thermal reservoirs. Full article

Electric Submersible Pumps (ESPs) serve as the primary artificial lift technology in offshore oilfields and play a crucial role in ensuring stable and efficient marine oil and gas production. However, the harsh offshore operating environment—characterized by high temperature, complex multiphase flow, and frequent load fluctuations—makes ESPs highly susceptible to accelerated degradation and unexpected failure. To enhance the operational reliability and efficiency of offshore production systems, this study develops a Remaining Useful Life (RUL) prediction method for offshore ESP systems using a Dual-Stage Attention-Based Recurrent Neural Network (DA-RNN). The model integrates an input-attention mechanism to identify degradation-relevant offshore operating variables and a temporal-attention mechanism to capture long-term deterioration patterns in real marine production data. Using field data from a representative offshore oilfield in the Bohai Sea, the proposed method achieves an average prediction error of less than 28 days, demonstrating strong robustness under complex offshore conditions. Beyond prediction, an RUL-driven operation optimization strategy is formulated to guide controllable parameters—such as pump frequency and nozzle size—toward extending ESP lifespan and improving offshore production stability. The results show that combining predictive maintenance with operational optimization provides a practical and data-driven pathway for improving the safety, efficiency, and sustainability of offshore oil and gas development. This work aligns closely with the goals of marine resource development and offers a valuable engineering perspective for advancing offshore oilfield operations. Full article

This study utilizes the drift–flux model to develop a new flow pattern map designed to facilitate an accurate estimation of gas void fraction (${\alpha }_g$) in vertical upward flow. The map is parameterized by mixture velocity ($u_m$) and gas volumetric quality (${\beta }_g$), integrating transition criteria from the established literature. For applications characterized by significant pressure gradients, such as gas lift, these criteria were reformulated as functions of pressure, enabling direct estimation from operational data. A critical component of this methodology for the estimation of ${\alpha }_g$ is the estimation of the distribution parameter ($C_0$). An analysis of experimental data, spanning pipe diameters from 1.27 to 15 cm across the full void fraction ranges (${0<\alpha }_g<1$), reveals a critical ${\alpha }_g$ threshold beyond which $C_0$ exhibits a distinct decreasing trend. To characterize this phenomenon, the parameter of the distribution-weighted void fraction (${\alpha }_c={\alpha }_g{C}_0$) is introduced. This parameter, representing the dynamically effective void fraction, identifies the critical threshold at its inflection point. The proposed model subsequently defines $C_0$ using a two-part function of ${\alpha }_c$. This generalized approach simplifies the complexity inherent in existing correlations and demonstrates superior predictive accuracy, reducing the average error in ${\alpha }_g$ estimations to 5.4% and outperforming established methods. Furthermore, the model’s parametric architecture is explicitly designed to support the optimization and fine-tuning of coefficients, enabling future use of machine learning for various fluids and complex industrial cases. Full article