Search Results (10,032)

Suction caisson anchor foundations have been widely applied in oil and gas platforms but remain in the exploratory stage for floating offshore wind power applications, where research on their anchor load-bearing characteristics is insufficient. This study focuses on the influence of length-to-diameter ratio, loading angle, and loading point depth on the anchor load-bearing characteristics of suction caisson anchor foundations. Through numerical simulation, the load–displacement curves, internal force distribution along the caisson body, movement mode transitions, and soil failure characteristics were obtained. The results indicate that loading point depth and loading angle alter the movement mode of the suction caisson anchor foundation, directly affecting its bearing capacity. Smaller loading angles result in higher bearing capacity, which initially increases with loading point depth, peaks at 0.6 L, and then decreases at 0.8 L due to a transition in the foundation’s movement mode. Similarly, as the length-to-diameter ratio decreases, the bearing capacity and overall movement amplitude of the foundation decrease, leading to a shift in the optimal loading point position. The circumferential soil pressure and horizontal soil resistance distributions vary significantly with loading angle and depth. The findings of this study provide valuable reference for the design and application of suction caisson anchor foundations. Full article

Drilling fluid plays a critical role in drilling engineering. With the deepening implementation of clean production concepts and increasingly stringent environmental regulations, the treatment standards for drilling wastewater at operational sites have been significantly elevated. In response to the characteristics of high oil content, high COD, high chromaticity, high ammonia nitrogen, and total phosphorus content in drilling, the use of fine bubbles to improve gas utilization efficiency and mass transfer effect, combined with ozone gas, is aimed at degrading difficult-to-degrade high-molecular-weight organic compounds, aiming to solve the problems of high viscosity and high oil content in drilling fluids returned from offshore platforms. Indoor simulation experiments have shown that by using ozone fine bubble technology to treat drilling fluids, the viscosity reduction rate can reach over 29%, and the oil removal rate can reach 40%. Ozone fine bubble technology has significant viscosity reduction and oil removal effects on high viscosity drilling fluids. Full article

In this study, we investigated the influence of water invasion velocity on gas–water permeability in bottom-water gas reservoirs. We conducted simultaneous core water invasion experiments under actual reservoir conditions, systematically examining varied permeability cores and multiple influx velocities. Two data processing methods were comparatively validated, analyzing gas–water relative permeability curves, fractional flow curves, and injection volume–recovery efficiency relationships. The results indicate that under HTHP (high-temperature, high-pressure) conditions, gas relative permeability declines faster, while water relative permeability increases more significantly. NMR imaging revealed that water preferentially invades smaller pores, accelerating gas–water flow before entering larger pores, leading to a rapid increase in water relative permeability. Long-core experiments unveiled a waterfront “stepwise advance” and localized water channeling due to heterogeneity, which were not observed in short-core tests. Water influx velocity critically influences fractional flow curves: high velocities cause rapid post-breakthrough water cut increase, easily inducing fast water breakthrough and coning, whereas low velocities promote a uniform frontal advance. HTHP (high-temperature, high-pressure) long-core flooding experiments more accurately reflect actual reservoir water influx dynamics, offering key insights for optimizing development strategies, delaying water influx, and enhancing recovery efficiency. Full article

Olive leaves (Olea europaea) are the most abundant agricultural by-product of olive tree cultivation, generating substantial waste each year. Their disposal is deemed an environmental challenge, particularly in Mediterranean countries that dominate the olive oil sector, yet their rich bioactive profile makes them promising candidates for functional food development. This study aimed to determine the total antioxidant capacity (TAC) and total phenolic content (TPC) of olive leaf powder extracts using different extraction solvents and methods to identify the most efficient strategy for possible incorporation into functional food systems. Extractions were performed with distilled water, 70% ethanol, 80% methanol, and 50% acetone using three methods: stirring, soaking, and ultrasound-assisted extraction (UAE). TAC and TPC were quantified using the FRAP and Folin–Ciocalteu assays, respectively. Among solvents, acetone consistently yielded the highest values across most methods (TAC: 19.02 mmol Fe²⁺/L, TPC: 1289.95 mg GA/L), while ethanol also showed strong extraction performance (TAC: 15.35 mmol Fe²⁺/L; TPC: 1214.76 mg GA/L), offering a safer and more scalable option for food applications. Method-wise, UAE achieved the greatest phenolic recovery, while both UAE and stirring proved effective for antioxidant extraction. Overall, these findings provide quantitative evidence supporting possible incorporation of olive leaf powder as a valuable ingredient in functional foods and other sustainable applications, while also contributing to the circular economy through the sustainable valorization of agricultural waste. Full article

The rising level of atmospheric carbon dioxide (CO₂) is a major driver of climate change, highlighting the need to develop carbon capture and storage (CCS) technologies quickly. This paper offers a comparative review of three main groups of porous adsorbent materials—zeolites, metal–organic frameworks (MOFs), and activated carbons—for their roles in CO₂ capture and long-term storage. By examining their structural features, adsorption capacities, moisture stability, and economic viability, the strengths and weaknesses of each material are assessed. Additionally, five different methods for delivering these materials into depleted oil and gas reservoirs are discussed: direct suspension injection, polymer-assisted transport, foam-assisted delivery, encapsulation with controlled release, and preformed particle gels. The potential of hybrid systems, such as MOF–carbon composites and polymer-functionalized materials, is also examined for improved selectivity and durability in underground environments. This research aims to connect materials science with subsurface engineering, helping guide the selection and use of adsorbent materials in real-world CCS applications. The findings support the optimization of CCS deployment and contribute to broader climate change efforts and the goal of achieving net-zero emissions. Key findings include CO₂ adsorption capacities of 3.5–8.0 mmol/g and surface areas up to 7000 m²/g, with MOFs demonstrating the highest uptake and activated carbons offering cost-effective performance. Full article

Fault activity represents a significant geological hazard to buried pipeline infrastructure. The associated stratigraphic dislocation may lead to severe deformation, instability, or even rupture of the pipeline, thereby posing a serious threat to the safe operation of oil and gas transportation systems. This study employs the 3D nonlinear finite element method to systematically investigate the mechanical behavior of buried steel pipes subjected to fault-induced dislocation, with particular emphasis on critical parameters including fault offset, internal pressure, and the diameter-to-thickness ratio. The study reveals that buried pipelines subjected to fault dislocation typically undergo a progressive failure process, transitioning from the elastic stage to yielding, followed by plastic deformation and eventual fracture. The diameter-to-thickness ratio is found to significantly affect the structural stiffness and deformation resistance of the pipeline. A lower diameter-to-thickness ratio improves deformation compatibility and enhances the overall structural stability of the pipeline. Internal pressure exhibits a dual effect: within a moderate range, it enhances pipeline stability and delays the onset of structural buckling; however, excessive internal pressure induces circumferential tensile stress concentration, thereby increasing the risk of local buckling and structural instability. The findings of this study provide a theoretical basis and practical guidance for the design of buried pipelines in fault-prone areas to withstand and accommodate ground misalignment. Full article

Nitrile rubber (NBR) exhibits excellent oil resistance, wear resistance, gas barrier properties, and mechanical properties. On the other hand, lignin, a by-product of the pulp and paper industry, can serve as an ideal substitute for carbon black as a reinforcing agent for rubber. However, when NBR is directly compounded with lignin, direct compounding fails to achieve the desired reinforcing effect due to poor dispersion of lignin in the NBR matrix and poor compatibility with the NBR phase. In this paper, carboxyl groups were introduced via cyano group hydrolysis. By controlling the hydrolysis time, we successfully prepared two types of carboxylated NBR with different carboxyl contents. Subsequently, the carboxylated NBR was processed into lignin/NBR composites via dry blending. The results indicated that the introduction of carboxyl groups endowed NBR with higher polarity and reactivity, significantly enhancing the interfacial compatibility between lignin and the rubber matrix. The mechanical properties of the composite were greatly improved, with the mechanical strength increasing from 4.5 MPa without carboxyl groups to 13.8 MPa with high carboxyl content. The good dispersion of lignin also significantly improved the thermal stability of the composite. The carboxylation modification strategy of NBR provides a new approach for preparing high-performance NBR/biomass composites. Full article

In this paper, we aim to study the oil–gas two-phase flow characteristics, leakage characteristics, and critical oil sealing characteristics of the bearing cavity sealing system of aero-engine bearings. For this purpose, the unsteady solution models of the conventional bearing cavity sealing system and the graphite with oil-return groove bearing cavity sealing system based on the Euler–Euler two-phase flow method were established. The experimental device for the oil–gas two-phase flow for the bearing cavity was designed and constructed. Thus, the oil–gas two-phase oil sealing characteristics of both systems under different structural and working condition parameters were studied. The results show that the change in the sealing length does not affect the leakage of lubricating oil for the conventional bearing cavity sealing system. It was observed that the higher the rotate speed is, the greater the oil leakage and the greater the critical sealing pressure difference. The graphite with oil-return groove structure can significantly reduce the leakage of lubricating oil and the critical sealing pressure difference. The increase in the length and number of oil-return groove can effectively reduce the leakage of lubricating oil. The width of the oil-return groove has no obvious effect on the sealing and leakage characteristics of the lubricating oil. Full article

With the advancement of oil and gas exploration and development technologies into deeper and ultra-deep reservoirs, complex geological conditions here render them highly susceptible to severe lost circulation. However, conventional bridging plugging methods struggle with large-sized lost circulation channels, while chemical gel plugging faces challenges such as low success rates and insufficient pressure-bearing capacity. To address this, a novel leak plugging method combining bridging and gel plugging is proposed herein. From structural stability and mechanical properties perspectives, the enhancing effect of nanomaterials on the gel system is revealed, and the synergistic mechanism of gel-bridging coupled plugging is elucidated. For the experimental setup, orthogonal experiments determined a base formulation with controllable gelation time: 10 wt% main agent, 2 wt% crosslinking agent, and a 1:3 pH regulator ratio. Introducing 1.0 wt% nanosilica enhanced gel properties, achieving 30 N strength at 120 °C aging. An optimized walnut shell bridging agent constructed the supporting skeleton, yielding a coupled plugging formulation with up to 8 MPa pressure for a 7 mm fracture. Lost circulation volume is controlled at 163 mL, outperforming single plugging methods. Research results demonstrate gel-bridging coupled plugging’s advantages for large fractures, providing new technical insights for severe lost circulation field construction. Full article

Although wind-assisted ship propulsion (WASP) is an effective technique for reducing the emissions of merchant ships, the best fuel type for complementing WASP remains an open question. This study presents a new original life cycle assessment method for ship fuels that uses a validated ship performance prediction model and actual operation conditions for a WASP ship. As a case study, the method is used to evaluate the fuel consumption and environmental impact of different fuels for a WASP ship operating in the Baltic Sea. Using a novel in-house-developed platform for predicting ship performance under actual operation conditions using hindcast data, the engine and fuel tank were sized while accounting for fluctuating weather conditions over a year. The results showed significant variation in the required fuel tank capacity across fuel types, with liquid hydrogen requiring the largest volume, followed by LNG and ammonia. Additionally, a well-to-wake life cycle assessment revealed that dual-fuel engines using green ammonia and hydrogen exhibit the lowest global warming potential (GWP), while grey ammonia and blue hydrogen have substantially higher GWP levels. Notably, NOx, SOx, and particulate matter emissions were consistently lower for dual-fuel and liquid natural gas scenarios than for single-fuel marine diesel oil engines. These results underscore the importance of selecting both an appropriate fuel type and production method to optimize environmental performance. This study advocates for transitioning to greener fuel options derived from sustainable pathways for WASP ships to mitigate the environmental impact of maritime operations and support global climate change efforts. Full article

A multiphase model of hydrothermal liquefaction (HTL) using the computational fluid dynamics coupling discrete element method (CFD-DEM) is used to simulate biocrude oil production from sludge flocs in a continuous stirred tank reactor (CSTR). Additionally, the influence of the agitator speed and the slurry flow rate on dynamic biocrude oil production is investigated through full transient CFD analysis in a scaled-up CSTR study. The kinetics of the HTL mechanism as a function of temperature, pressure, and residence time distribution were employed in the model through a user-defined function (UDF). The multiphysics simulation of the HTL process in a stirred tank reactor using the Lagrangian–Eulerian (LE) approach, along with a standard k-ε turbulence model, integrated HTL kinetics. The simulation accounts for particle–fluid interactions by coupling CFD-derived hydrodynamic fields with discrete particle motion, enabling prediction of individual particle trajectories based on drag, buoyancy, and interphase momentum exchange. The three-phase flow using a compressible non-ideal gas model and multiphase interaction as design requirements increased process efficiency in high-pressure and high-temperature model conditions. Full article

CO₂ flooding has become a strategic tool for enhanced oil recovery and reservoir management in mature fields. This technique, however, is rarely utilized in asphaltenic crude oil systems, due to the likely occurrence of high asphaltene precipitation. The effect of asphaltene concentrations and CO₂ injection pressures has mostly been the focus of studies in determining asphaltene precipitation rates. However, asphaltene precipitation is not the only direct factor to be considered in predicting the extent of damage in an asphaltenic crude oil system. In this study, a compositional reservoir simulation was conducted using Eclipse 300 to investigate the injection pressure at which asphaltene-induced formation damage can be avoided during both miscible and immiscible CO₂ flooding in an asphaltenic crude system. Simulation results indicate that asphaltene-induced permeability reduction exceeded 35% in most affected zones, with a corresponding drop in injectivity of 28%. Cumulative oil recovery improved by 19% compared to base cases without CO₂ injection, achieving peak recovery after approximately 4200 days of simulation time. As CO₂ was injected below the minimum miscibility pressure of 2079.2 psi, a significantly lower asphaltene precipitation was observed near the injector. This could be attributed to the stripping of lighter hydrocarbon components (C2–C7+) occurring in the transition zone at the gas–oil interface. Injecting CO₂ at pressures above the minimum miscibility pressure resulted in precipitation occurring throughout the entire reservoir at 3200 psia and 1000 bbls per day injection rates. An increase in the injection rate at pressures above the minimum miscibility pressure increased the rate of precipitation. However, a further increase in the injection rate from 1000 bbl per day to 4200 bbl per day resulted in a decrease in asphaltene. The pressure drop in the water phase caused by pore throat increase demonstrated that water injection was effective in removing asphaltene deposits and restoring permeability. This work provides critical insights into optimizing CO₂ injection strategies to enhance oil recovery while minimizing asphaltene-induced formation damage in heavy oil reservoirs. Full article

Pan-connected interlayers are widely present in oil reservoirs, forming flow channels at different positions. However, conventional profile control agents struggle to plug deep interlayer channels in reservoirs, limiting the swept volume of injected water. Additionally, a clear methodology for physically simulating pan-connected reservoirs with interlayer channels and calculating interchannel flow rates remains lacking. In this study, a physical model of pan-connected interlayer reservoirs was constructed to carry out deformable gel particles (DGPs) plugging experiments on interlayer channels. A mass conservation-based flow rate calculation method for interlayer channels with iterative solution was proposed, revealing the variation law of interlayer channel flow rates during DGP injection and subsequent water flooding. Finally, oil displacement and DGP profile control experiments in pan-connected interlayer reservoirs were conducted. The study shows that during DGP injection, injected water enters the potential layer through interlayer channels in the middle and front of the water-channeling layer and bypasses back to the water-channeling layer through channels near the production well. With the increase in DGP injection volume, the flow rate of each channel increases. During subsequent water flooding, DGP breakage leads to a rapid decline in its along-path plugging capability, so water bypasses back to the water-channeling layer from the potential layer through all interlayer channels. As the DGP injection volume increases, the flow rate of each channel decreases. Large-volume DGPs can regulate interlayer channeling reservoirs in the high water cut stage. Its effectiveness mechanism involves particle migration increasing the interlayer pressure difference, which drives injected water to sweep from the water-channeling layer to the potential layer through interlayer channels, improving oil recovery by 19.74%. The flow characteristics of interlayer channels during DGP injection play a positive role in oil displacement, so the oil recovery degree in this process is greater than that in the subsequent water flooding stage under each injection volume condition. The core objective of this study is to investigate the plugging mechanism of DGPs in pan-connected interlayer channels of high-water-cut reservoirs, establish a method to quantify interlayer flow rates, and reveal how DGPs regulate flow redistribution to enhance oil recovery. Full article

Underground river reservoirs are dominated by large-scale elongated caves and are typical fractured–vuggy carbonate reservoirs. This paper established physical models of underground river reservoirs with different filling modes. We first conducted bottom water flooding experiments and then studied multi-well, alternating water flooding and gas injection. The remaining oil distribution patterns and key factors under different filling modes and well locations were studied to clarify the recovery-improvement mechanisms of multi-well water and gas injection. The results show that the remaining oil after bottom water flooding can be categorized into the following five types: “insufficient well control remaining oil”, “attic remaining oil”, “bypass remaining oil”, “residual oil in filling medium”, and “shielded oil in filling medium”. Early water injection effectively recovers “insufficient well control remaining oil”, “bypass remaining oil”, and “residual oil in filling medium”. Gas injection targets included “attic remaining oil”. Late water injection can further improve recovery. When the cave is partially filled, there exists a large amount of “shielded oil in filling medium” that is difficult to recover, reducing recovery by 27% compared to unfilled cases. This study clarified the remaining oil distribution laws and water–gas flooding mechanisms for underground river reservoirs, providing guidance for efficient development. Full article

Waste drilling fluids represent a complex gel–colloidal system containing structurally stable polymeric networks and heavy-metal ions that can cause tremendous damage to the ecosystem. The current disposal methods, like solidification/landfills, formation reinjection, and chemical treatment, commonly suffer from high secondary pollution risks, poor resource recovery, and incomplete detoxification. This paper developed a photocatalytic approach to complex gel system treatment by hydrothermally synthesizing a novel sulfur-doped, oxygen-vacancy-modified 3D flower-like xS-BiOBr₀.₅Cl₀.₅ structure which effectively narrowed the bandgap of BiOX and thus significantly enhanced its catalytic activity. The chemical composition, morphology, specific surface areas, and bandgaps of the materials were characterized. The photocatalytic performance and cyclic stability of the materials were measured, and 0.5S-BiOBr_0.5Cl_0.5 showed the best photocatalytic performance. The rhodamine B(RhB) degradation and polymer degradation efficiencies of 0.5S-BiOBr_0.5Cl_0.5 were up to 91% and 79%, respectively, while the Hg(II), Cr(VI), and Cr(III) reduction efficiencies of the material were up to 48.10%, 96.58%, and 96.41%, respectively. The photocatalytic mechanism of the xS-BiOBr_0.5Cl_0.5 materials was evaluated through an oxygen vacancy analysis, active species capture experiments, and density functional theory (DFT) computations. Overall, the xS-BiOBr_0.5Cl_0.5 materials can provide a low-cost and harmless treatment method for waste drilling fluids and promote the “green” development of oil and gas. Full article