The blowout preventer (BOP) is critical for ensuring oil and gas well safety, but its main sealing components are susceptible to crack-type leakage during well shut-in, posing significant risks. Limited research on temporary plugging using particle injection has hindered process development. Based on the actual blowout conditions (10–70 MPa) and the size of BOP, this paper establishes a simulation model and builds an experimental platform to analyze the effects of particle concentration, size, shape, elastic modulus, friction coefficient and well pressure on the plugging effect. The results show that the plugging process primarily depends on a small amount of strong chains to withstand fluid drag. Furthermore, conventional downhole plugging theories (D50 and D90) are not fully applicable to wellhead conditions. At 70 MPa, single-particle bridging shows optimal plugging performance. The research results provide theoretical support for the process parameters and plugging formula of particle plugging.

In oil and gas perforating operations, detonation loading from shaped charges can induce tubing-string vibration and failure risks such as buckling and fracture. Based on Lagrange's equations and the finite element method, this study establishes a fully coupled axial-lateral-torsional-bending (ALTB) nonlinear dynamic model of a perforating tubing string using an extended spatial Euler-Bernoulli beam-element description. The model considers detonation loading, casing constraints, tubing-casing contact, and the actual string assembly configuration. A coupled solution framework integrating NOCH-α time integration, Newton-Raphson iteration, penalty contact treatment and banded matrix solution is developed. By layered checking of contact constraints and displacement convergence, and by solving the correction equation with banded Gaussian elimination, the computation time is reduced by 34.2%-49.7% compared with baseline Scheme 1 while maintaining accuracy. Compared with field-measured axial acceleration peaks, the model-calculated positive and negative peak errors are 9.28% and 4.42%, respectively, indicating reasonable agreement between the model results and measured axial acceleration response. For the studied field-well condition and tubing-string configuration, the vibration response shows a “strong lower section and weak upper section” pattern. Axial compression dominates the response, and buckling mainly occurs in the perforating gun and tubing sections. Under the simulated condition, the maximum von Mises stress is 310.86 MPa, remaining below the tubing yield strength. In this case, the tubing-packer connection is identified as the main high-risk region. These results provide a theoretical basis for dynamic safety evaluation of perforating tubing strings under detonation loading.

Conventional lost circulation materials (LCMs) suffer from limitations such as poor adaptability and low plugging efficiency. This study developed a high-temperature-responsive, shape-memory, expandable lost circulation material. Specifically, using thermosetting epoxy resin as the matrix and organic montmorillonite (OMMT) as reinforcing nanoparticles, an epoxy foam nanocomposite (OMMT/SMPF) was fabricated through chemical foaming combined with hot-press molding techniques. Lab tests demonstrated that the composite (OMMT/SMPF) exhibits excellent mechanical properties and shape memory characteristics. The incorporation of OMMT significantly enhanced the composite's thermal stability and glass transition temperature (Tg). When the OMMT content was increased to 5%, the thermal decomposition temperature of the OMMT/SMPF composite rose from 314 degrees C (pure resin) to 339.5 degrees C; while its Tg increased from 104.94 degrees C (pure resin) to 137.23 degrees C. The maximum expansion rate at 140 degrees C reached 130%. These improvements significantly broaden its potential for application in high-temperature deep well drilling operations. Simulation experiments for sealing long fractures confirmed that temperature significantly influences the plugging performance of OMMT/SMPF granules. After being stimulated by high temperatures, the OMMT/SMPF rapidly expands to seal fractures, demonstrating significantly superior plugging effectiveness compared to conventional bridging materials. This study provides crucial theoretical underpinnings for the development of high-efficiency circulation materials.

The Mullins effect is a defining characteristic of filled rubber and exhibits significant temperature dependence. Comprehensive studies and modeling of this effect are essential to ensure the reliability of rubber products in service. However, existing constitutive models lack in-depth discussion on the physical nature of the Mullins effect, making it challenging to elucidate the influence of temperature on this phenomenon from a mechanistic perspective. In this manuscript, a novel model based on dynamic force spectroscopy theory is proposed to elucidate and capture the temperature-dependent Mullins effect in filled rubber. A probability distribution function of the link rupture force is introduced, interpreting the damage mechanism of the Mullins effect as a continuous rupture-rebonding process of the links under chain tension. Furthermore, the total strain energy is expressed as the integral of the strain energy of each chain over the distribution range. By quantifying the temperature effect on a single parameter in this distribution function, temperature dependence is explicitly incorporated into the new damage mechanism. The particle swarm optimization algorithm is employed to fit the uniaxial tensile experimental data from two rubber specimens. The model’s ability to predict the mechanical response across different temperatures and a wide range of deformations is validated. The proposed model is simple in form with clear physical significance, providing effective support for the simulation and prediction of the mechanical properties of rubber products under varying temperature environments.

High-temperature produced gas imposes severe thermal loads on underground coal gasification (UCG) production wellbores, creating substantial challenges for wellhead thermal management and continuous operation. The dominant thermal-control mechanism in spray-cooled UCG production wellbores, however, remains insufficiently understood. Here, a steady-state coupled heat-transfer model is developed by integrating segmented axial temperature calculation, temperature-dependent thermophysical properties of multicomponent produced gas, and annular spray cooling. The model is evaluated against field-measured wellhead temperature and applied to investigate the effects of daily gas output, insulated production tubing thermal conductivity, and overall wellbore heat-transfer coefficient.Under the reference condition, annular spray cooling reduces the predicted wellhead temperature from 498 °C to 255 °C. Daily gas output exerts the strongest influence on the thermal response because increasing production intensifies the thermal load transported upward by the produced gas and progressively increases the cooling demand. The thermal conductivity of insulated production tubing governs heat partitioning between the produced gas and spray-water system, resulting in a thermal-design window of approximately 5–10 W/(m·K) that balances wellhead cooling against excessive spray-side thermal loading. By contrast, variations in the overall wellbore heat-transfer coefficient have only a minor effect on the axial temperature field. These results indicate that thermal control is governed primarily by the competition between gas-borne thermal loading and internal gas–water heat exchange, whereas external radial heat dissipation plays a secondary role under the investigated conditions. These findings provide a quantitative basis for thermal-control design and operating-parameter selection in high-temperature UCG production wellbores, particularly for balancing production intensity, wellhead thermal protection, and spray-side thermal loading.

Abstract To address the low utilization (typically <50%) of grid capacity oversized for peak drilling power, this work proposes a collaborative supply mode integrating grid and energy storage system (ESS) to reduce grid capacity and lower drilling costs. The power profile and change rates under typical drilling conditions are first analyzed to determine the grid installation capacity and ESS discharge threshold post-intervention. The effectiveness of the coordinated grid-ESS supply is then validated through theoretical analysis and experimental testing. Results show that with ESS intervention, the grid capacity can be reduced from 2500 kVA to 1200 kVA, with the average utilization rate increasing by up to 52%. In addition, annual drilling cost savings reach CNY 293 000, and the estimated payback period for the ESS investment is 4.6 years. This study confirms the feasibility of grid-ESS collaborative power supply in oil and gas drilling and offers new insights for energy saving and carbon emission reduction in such operations.

Laser shock peening (LSP) and surface texturing are two valid surface modification techniques with well-studied tribological benefits. However, whether their synergistic effect can produce an enhancement effect has not been explored. This study performed on 55SiMoVA bearing steel, systematically evaluating the tribological behavior of untreated, laser shock peening-treated (LSPed), surface texturing-treated (Textured), and laser shock peening synergistic surface texturing-treated (LSPed-textured) samples through a reciprocating friction test system under the drilling fluid lubrication. The results exhibited that the LSPed-textured sample showed the best wear performance, with a 71.43% reduction in wear volume compared to the untreated sample, and were significantly better than the LSPed (42.86% reduction) and Textured (38.46% reduction) samples. The microstructure evolution induced by LSP formed a protective surface layer characterized by high hardness and residual compressive stress, enhancing the load-bearing capacity and inhibiting crack extension, thus reducing the wear volume due to abrasive and delamination wear. Furthermore, surface texturing produced a surface with positive kurtosis (Sku) and negative skewness (Ssk), and the reduced valley depth (Svk) and the valley void volume (Vvv) increased 86 times and 75 times, respectively. This surface characteristic was conducive to capturing wear debris, supporting load, and lubricating, further optimizing the interfacial friction behavior.

Downhole gas-liquid separators often face the challenge of wide operating conditions in which a wide range of gas volume fraction (GVF) and processing capacity (PC) are coupled in actual operations. To overcome the bottleneck problem that the continuity of gas core and the stability of flow field are difficult to maintain due to the failure of interstage synergy in traditional design, which leads to a significant reduction in separation efficiency, this study innovatively proposes an inter-stage coupled gas-liquid separator (IS-C-GLS) based on the sequential separation concept of "stabilization before separation, and coarse before fine". Combining numerical simulations with experimental validation, the internal flow field evolution characteristics and synergistic separation mechanisms of the IS-C-GLS were systematically investigated under the typical operating conditions of the Qinghai Oilfield (China), spanning a GVF of 20% similar to 80% and a PC of 300-700 m(3)/d. The results indicate that the IS-C-GLS exhibits excellent operating adaptability under wide working conditions based on the rigorous evaluation criteria of a separation efficiency eta > 80% and a pressure drop Delta P < 3177 kPa. Benefiting from the inter-stage synergistic effect enabled by the sequential structure, the simulated and experimental separation efficiencies remain stably above 83.5% and 80%, respectively, which highly matches the fluctuating production demands of the oilfield. By validating and analyzing the suppression mechanisms of the IS-C-GLS's inter-stage synergy against gas core breakup and flow field instability, this study provides vital theoretical and technical support for enhancing separator efficiency under complex operating conditions.

Natural gas hydrate (NGH) has emerged as a promising clean energy resource, yet its commercial exploitation faces significant challenges due to hydrate-sand cemented particles agglomeration during solid fluidization mining. These composite particles not only increase energy consumption and equipment abrasion but also pose reservoir destabilization risks, ultimately compromising extraction efficiency. To address these challenges, this study proposes a novel coupled numerical approach based on Computational Fluid Dynamics (CFD) and Discrete Element Method (DEM) to systematically investigate the de-cementation mechanism. This article uses the CFD-DEM coupling method to analyze the variation laws of tangential stress and normal stress of cemented particles, and combines quantitative evaluation of de-cementation efficiency to reveal the de-cementation mechanism at different structural parameters. The results show that the de-cementation efficiencies gradually increase to 88.61% and 89.36% with the increase of do andl, respectively. While the de-cementation efficiencies gradually decrease to 81.4%, 80% and 77.78% with the increase of b, H and theta, respectively. Moreover, as duincreases, the de-cementation efficiency first increases then decreases with the peak value of 84.78%. The research presents a systematic evaluation of hydrocyclone structural parameters for de-cementation performance, offering a novel approach for enhanced in-situ hydrate-sand separation during NGH mining.

Driven by China's carbon peaking and carbon neutralization goals as well as the strategic development of deep-offshore energy resources,energy island clusters in the South China Sea are evolving from single energy-supply nodes into integrated engineering platforms that combine multi-energy coupling,energy conversion,operational support,emergency response,and long-distance replenishment.However,the existing support model dominated by nearshore home ports is constrained by long offshore distances,complex sea conditions,extended replenishment chains,and insufficient multi-stakeholder coordination,making it difficult to support large-scale and continuous operation of deep-offshore energy island clusters.This study reviews operational support models for energy islands and offshore energy hubs in China and abroad,analyzes the capability basis and limitations of ports,island-reef nodes,and frontier facilities in the South China Sea,and proposes a three-tier coordinated support system consisting of core home ports,relay hubs,and frontier support nodes.Based on support distance,water depth,task attributes,and response requirements,the proposed system divides the support space into a nearshore support layer,an offshore relay layer,and a deep-offshore frontier layer,corresponding respectively to integrated coordination,relay transfer,and near-field response functions.Scenario-based calculations indicate that the proposed system can reduce the response time for urgent spare-parts replenishment from approximately 51.5 h to 17.5 h,a decrease of about 66%,and reduce the arrival time for medical rescue from approximately 3.28 h to 1.43 h,a decrease of about 56.4%.Institutionally,this study recommends establishing the South China Sea Deep Blue Economic Comprehensive Pilot Zone as a coordination platform,while advancing standard sea-unit certification,three-dimensional layered sea-use rights,enclave-economy cooperation,and sea-air emergency coordination mechanisms.The results indicate that the three-tier coordinated support system can improve the operational efficiency,emergency response capability,and system resilience of energy island clusters in the South China Sea,providing a reference for the construction of deep-offshore energy engineering support systems in China.

The bridging behavior of particles in ultra-high-pressure leakage channels is critical to emergency plugging, yet the micromechanical mechanisms governing bridge formation and stability remain insufficiently understood. In this study, emergency plugging after blowout preventer (BOP) shear-ram sealing failure was investigated using a coupled CFD-DEM approach under a differential pressure of 70 MPa. Orthogonal simulations were performed to evaluate the effects of process parameters on plugging efficiency. Particle size was identified as the dominant factor within the investigated parameter range. A force-based stability indicator, termed the dual-force ratio, was introduced as the ratio of the resultant normal contact force to the hydrodynamic drag acting on particles near the leakage opening. Successful plugging was associated with a sustained dual-force ratio greater than 8, whereas failed cases remained below this threshold or exceeded it only transiently. Three plugging modes were identified: multi-particle bridging, single-particle gate blocking, and internal-bridge/external-seal composite plugging. Cylindrical and cubic particles were more likely to form stable multi-particle bridges. Stable bridging was associated with W/D < 1.67, but this threshold should be regarded as a scenario-dependent geometric indicator rather than a universal constant. These findings provide a force-based framework for evaluating plugging stability in ultra-high-pressure leakage channels.

The well control ignition device is the critical equipment for eliminating combustible and toxic gases within the casing during a well blowout. The jet performance of its nozzle directly determines the safety and reliability of ignition. To enhance the jetting performance of this nozzle and optimize its structure, this study systematically investigated the influence mechanism of the structure of the conical nozzle and the key parameters of the jetting medium on the jetting performance. Based on computational fluid dynamics (CFD) simulations and jet theory analysis, it was determined that the average velocity of the nozzle outlet is the key factor determining the spray range, while the velocity attenuation along the path dominates the stability of the jet. Through single-factor analysis, the nozzle contraction angle A, diameter D, and length L were identified as the core optimization variables. Multi-objective optimization was performed using a response surface method based on a Kriging model. Results demonstrate that the optimized nozzle outlet average velocity increased from 40.07 m/s to 43.7 m/s, while the velocity attenuation along the path decreased significantly from 1.53 m/s to 0.048 m/s. It effectively enhances the nozzle's spray range and jet stability.

Under the alternating injection and production stress acting on the storage reservoir pipe column, it will continuously be impacted by solid sand-grain particles carried by the high-speed fluid at specific angles and speeds, resulting in material damage and detachment, which affects its injection and production performance. To explore the erosion characteristics of the pipe column, this study developed a jet-type gas-solid-liquid three-phase erosion experimental system, using the typical plastic pipe material steel L80 as the research object, systematically studying the influence of particle impact angle, speed, and particle size on the erosion rate, and analyzing the microscopic wear mechanism of the material through scanning electron microscopy. Based on the experimental data, an erosion model applicable to the injection and production conditions of the storage reservoir was established using the least squares method, and its performance was assessed through computational fluid dynamics-based comparisons with the available experimental data. It was also compared with classic models such as the Generic model. The study shows that the L80 steel exhibits typical plastic material erosion behavior. The erosion rate reaches its peak at a 30 degrees impact angle during the gas production stage and increases exponentially with the increase in particle speed and size. During the gas injection stage, the erosion is relatively mild but still follows a similar pattern. The established model is in good agreement with the experimental results and outperforms the commonly used classic models in terms of prediction accuracy. This study reveals the core mechanism of cyclic erosion, namely, after forming directional micro "lip-shaped structures" during the gas production stage, the reverse fluid impact during the gas injection stage will cause accelerated damage to its weak root points, which is the key physical mechanism for the exacerbation of material loss under alternating conditions. The research results deepen the understanding of the erosion mechanism of the pipe column in the storage reservoir and provide a theoretical basis and engineering references for predicting pipeline lifespan and ensuring safe operation.

To address the industry challenges of mismatched power output from gas generators and dynamic downhole load demand in drilling operations, along with the lack of scientific configuration basis for the coordinated operation of energy storage systems and traditional power generation equipment, this study conducts an in-depth optimization study on a hybrid gas-energy storage power supply system using a 50DB drilling rig as the specific research object. Historical load power data of the rig during typical operating cycles were systematically collected and analyzed. Based on this, a cost optimization model for the coordinated gas-energy storage power supply was developed, aiming to minimize the total life-cycle cost. This model innovatively integrates key economic factors, including the initial investment and long-term operation and maintenance costs of the battery energy storage system, as well as the fuel consumption and maintenance costs of the gas generator sets. The optimization objectives are the lowest overall system cost and the optimal energy storage capacity configuration. The results indicate that: ① While meeting the actual power demand, the optimal capacity of the energy storage battery is 1870 kWh, and the optimal charging/discharging power is 992 kW; ② The number of gas generator sets on site can be optimized from the original 8 to 4. This allows the units to operate stably within their high-efficiency range, increasing the average operating efficiency significantly from a maximum of 22.7% before optimization to 42.6%; ③ Under extreme working conditions with the maximum load during drilling operations, the optimally configured energy storage system can independently support the full site load for 4 hours, greatly enhancing the reliability and resilience of the power supply system.

The strengthening of the marine sector and the realization of carbon peaking and carbon neutralization goals urgently necessitates a shift in marine energy development toward deep-sea and intensive utilization.The offshore integrated energy island(OIEI)serves as an effective solution for resolving challenges in deep-sea power consumption and achieving the diversified conversion of energy forms.Based on a summary of international OIEI development models and their current status,this study reviews China's development foundation and analyzes challenges such as institutional fragmentation,technological bottlenecks,and the absence of a business closed loop.Drawing on a source-grid-load-storage-utilization integrated philosophy,the study proposes a comprehensive development model featuring energy conversion,multi-energy complementarity,and zero-carbon services.It outlines three differentiated pathways:a nearshore shared model,a mid-to-far offshore industrial fusion model,and a deep-sea off-grid model.Multi-scenario techno-economic calculations and sensitivity analysis indicate that the economic efficiencies of the three models exhibit significant nonlinear alternating evolution characteristics with increasing offshore distances,and the commercial feasibility of off-grid energy islands in the deep sea is highly dependent on the support provided by green fuel premiums and the carbon market mechanism.The study recommends leveraging marine resource endowments to formulate medium-to-long-term plans supporting OIEI development.It calls for mastering key core technologies,such as high-efficiency energy conversion and green fuel power equipment tailored for multi-scenario applications.Furthermore,the research suggests accelerating the deep cross-sector integration of energy,marine engineering,and shipping industries,as well as establishing international certification systems for green hydrogen,ammonia,and alcohols.Additionally,it proposes perfecting a commercial guarantee mechanism driven by incentive policies and carbon markets to advance the large-scale construction and high-quality development of China's OIEIs.

Solid fluidization technology is an effective method for the development of natural gas hydrate, and the key step is the de-cementation and separation of a large number of hydrate-sand cemented particles in the hydrate slurry. Natural gas hydrate reservoirs have characteristics such as anisotropy, wide saturation range, diverse occurrence forms, and cross-scale particle distribution. Therefore, it is urgent to systematically study the effect of different reservoir parameters on the de-cementation performance of a hydrocyclone. This article uses the CFD-DEM coupling method to analyze the variation laws of tangential stress and normal stress of cemented particles under different reservoir parameters, and combines quantitative evaluation of de-cementation efficiency to reveal the de-cementation mechanism. It is pointed out that hydrate-sand cemented particles are mainly subjected to normal tensile failure during the de-cementation process. This article provides a key theoretical basis and data support for the optimization design of a hydrocyclone and is conducive to promoting the green and safe development of natural gas hydrate.

In the process of oil and gas drilling, the blowout preventer (BOP) serves as the last line of defense before wellhead loss of control, and its sealing reliability is of critical importance. However, under the erosion of high-pressure sand-containing fluids, the sealing components of the BOP are prone to failure, resulting in long-slit-type leakage ports, which seriously threaten well control safety. In response to the current lack of theoretical guidance for emergency plugging process parameters, this paper adopts the coupled computational fluid dynamics and discrete element method (CFD-DEM) to establish a numerical model for the plugging of long-slit-type gaps with particles under blowout conditions. The migration and bridging plugging behaviors of three typical shaped particles, namely spherical, cylindrical, and square, under different sizes, concentrations, and pump injection rates are systematically studied. The results indicate that particle transport within the wellbore can be divided into an initial transport stage dominated by jet diffusion and a plugging-structure formation stage dominated by bridging and particle accumulation. When the particle size exceeds the slit width, cylindrical particles exhibit comparatively better plugging performance under the conditions considered in this study. For a long-slit leakage channel with a width of 5 mm, the combination of cylindrical particles with an equivalent diameter of 6 mm, a particle volume concentration of 20%, and a pumping rate of 2.4 m3/min demonstrated relatively favorable overall plugging performance. The particle concentration mainly affects the bridging time, and the bridging time tends to stabilize when the concentration reaches 20%. The higher the pump injection rate, the earlier the particles reach the gap opening, but it has little impact on the final plugging effect. This study provides a scientific basis for the optimization of emergency plugging process parameters after BOP sealing failure, filling the gap in the research on the plugging mechanism of equipment leakage under blowout conditions.

During underbalanced drilling operations, the packing element is subjected to sustained high wellbore pressure, making it highly susceptible to failure modes such as tension-compression fatigue cracking and material spallation. Initially, uniaxial tensile tests were conducted on specimens fabricated from the rubber material of the rotating control head (RCH) packing element to fit and obtain the parameters for the material’s constitutive model. Subsequently, a mechanical analysis of the RCH packing element was performed for different stages of the tripping process. Finite element models were established for both a conventional packing element and a new design incorporating reinforcing ribs. The simulation results from both models were extracted and analyzed. A comparative assessment of the sealing performance and fatigue performance was conducted based on three key aspects: the distribution and magnitude of von Mises stress, the contact stress at the sealing interface along with the effective sealing width, and the deformation behavior of the elements. During tripping-in when sealing the drill pipe, the Mises stress concentration at the critical failure-prone location in the reinforced packing element decreased by 45.285

In deep oil and gas exploration, rubber bushings in high-torque positive displacement motors (PDMs) often suffer wear, peeling, and fatigue fracture due to prolonged exposure to high temperatures, high pressures, and oil-based drilling fluids. Existing failure analyses rarely couple environmental aging with fatigue crack propagation. To address this, we conducted aging experiments under simulated downhole conditions (175 degrees C, 70 MPa, oil-based fluid) and developed a thermo-mechanically coupled finite element model of the bushing and metal rotor. This model systematically simulates the mechanical characteristics, heat generation, and fatigue failure of bushings in high-temperature and high-pressure (HTHP) wells. Results indicate that aging increased the peak von Mises and contact stresses by 314 % and 312 %, respectively. Additionally, the maximum temperature rise of the aged bushing reached 48.22 degrees C (4.12 times that of the unaged state), causing severe heat accumulation at the arc crests. Finally, the entire fatigue crack initiation and propagation process was accurately simulated, providing significant insights for predicting rubber component fatigue failure under thermo-mechanical coupling.

In order to study the optimal size and sealing performance of the foot-shaped slip ring for reciprocating seal, the loading method of fluid pressure penetration is used to simulate the effect of fluid medium pressure on the seal, and the multi-objective optimization of the geometry of the slip ring is carried out based on optimization software to obtain the best combination of parameters for the foot-shaped slip ring. The effects of slip ring geometry, pre-compression and working pressure on Von Mises stress and contact pressure were investigated using the finite element method. The results show that the optimized geometry of the foot-shaped slip ring can reduce the maximum contact stress on the main sealing surface from 108.5 MPa to 75.22 MPa (a reduction of 30.7%) and decrease the maximum Von Mises stress of the slip ring from 62.84 MPa to 41.57 MPa (a reduction of 33.8%), thereby greatly reducing the wear of the slip ring while ensuring reliable sealing. In the static sealing condition, a smaller pre-compression (1.2-1.3 mm) leads to stress concentration in the O-ring, and the recommended pre-compression range is 1.4-1.6 mm. In the dynamic sealing condition, the effect of pre-compression on the sealing performance is greater than that of reciprocating motion speed on the sealing performance, and the foot-shaped slip ring seal is found to be more suitable for low-speed operation at 0.1-0.2 m/s. The optimized design provides a data-driven methodology for enhancing the reliability and service life of reciprocating seals in high-pressure environments.