Search Results (119)

The antifoaming performance of natural gas desulfurization solvents is critical for maintaining product gas quality and ensuring the safe operation of processing units. Hydrocarbon impurities can enter amine solutions through feed-gas entrainment, wellhead flowback carryover, and leakage of equipment lubricants. These contaminants may gradually accumulate in the solvent system and become a significant contributor to foaming. To address the industrial demand for rapid quantitative determination of hydrocarbon contaminants in desulfurization solvents, this study investigates in-service UDS-series solvents and representative samples collected from a natural gas purification plant in western Sichuan. NMR spectroscopy and GC-MS analyses reveal that the impurities are predominantly n-alkanes in the C₁₃-C₁₈ range, based on which a corresponding reference standard oil was prepared. COSMO-RS calculations combined with molecular interaction analysis identify n-hexane as the optimal extraction solvent. The ultraviolet spectrophotometric method commonly used to determine hydrocarbons in environmental water samples shows limited sensitivity to long-chain n-alkanes and requires strong acid pretreatment that disrupts the amine solvent matrix, rendering it unsuitable for UDS solvents. In contrast, the n-hexane extraction-GC-FID method showed good linearity, precision, and accuracy, meeting engineering analytical requirements for monitoring hydrocarbon contamination in MDEA-based UDS desulfurization solvents. Full article

Virtual flow metering (VFM) serves as an effective alternative to traditional physical flow meters, significantly reducing gas-field metering costs and operational complexity. However, conventional VFM typically employs a single-modeling approach, failing to address metering requirements across varying production conditions and data types. Focusing on wellhead choke equipment, four mechanistic models (MModels) based on choke-flow dynamics are constructed using piecewise linear regression, alongside six machine learning models. Hyperparameters are optimized via grid search and cross-validation, establishing a hybrid mechanistic and data-driven multi-model VFM method for gas wells. Systematic testing utilizes field data from gas wells in the Southwest Oil and Gas Field, with the Shapley additive explanations (SHAP) method quantifying feature contributions. MModel results indicate superior overall performance by the temperature-difference piecewise linear model, yielding a training R² of 0.91 and a mean test error of 4.59%. Under different valve-position conditions, the downstream-temperature piecewise linear model demonstrates better predictive capability when the valve position is equal to 100, whereas the valve-position piecewise linear model achieves higher accuracy when the valve position is less than 100. MLModel results reveal that among ten feature parameters, “Date” and “Valve Position Indication” contribute most significantly to prediction accuracy, accounting for over 50% of cumulative contribution in GBoost (extreme gradient boosting) and CatBoost (categorical boosting) models. Notably, the XGBoost model exhibits optimal predictive performance, achieving a training R² of 0.979 and a mean test error of merely 0.13%. Random sampling results show coefficient of variation values below 0.1 for all metrics, demonstrating exceptional robustness, providing an effective technical solution and solid theoretical support for gas-field VFM. Full article

In shale gas extraction, solid particles such as fracturing proppants cause erosion in production and transmission pipelines. Cyclone desanders are widely used for gas–solid separation, but high-velocity sand-laden fluids frequently induce equipment failure, leakage and safety risks. Therefore, research on erosion and protective measures is essential. This study focuses on the desander at the M shale gas wellhead, where wall thickness was measured at three monitoring points to determine erosion rates. A CFD-based numerical erosion model for the cyclone desander was developed using ANSYS Fluent within the ANSYS Workbench 19.2 environment (ANSYS, Inc., Canonsburg, PA, USA). The model was validated by comparing simulation results with field data, revealing the distribution patterns of the velocity field, pressure field, and erosion rate. The study analyzed the impact of nine factors on desander erosion: inlet aspect ratio, cylinder radius, cone length, dust discharge port diameter, exhaust port diameter, particle size, particle concentration, inlet velocity, and operating pressure, clarifying the erosion variation patterns for each factor. SPSSAU V25.0 (Beijing Qingsi Technology Co., Ltd., Beijing, China) was employed to analyze the significance of these nine factors, identifying six significant influencing factors: inlet aspect ratio, cylinder diameter, dust discharge port diameter, particle size, particle concentration, and inlet velocity. Subsequently, response surface analysis was performed using Design-Expert 13 (Stat-Ease, Inc., Minneapolis, MN, USA) to obtain the relationship between the factors and their impact on maximum erosion, leading to the establishment of a predictive model for the maximum erosion rate. In addition, geometry optimization, local wall thickening, coating protection, material selection, and bionic rib structures were discussed as erosion-mitigation strategies. The optimized geometry reduced the erosion rate at the inlet and dust discharge outlet by 20.4% and 21.8%, respectively, while the bionic rib structure reduced the maximum erosion rate by 58%. Full article

During the development of multiple wells of shale gas, coproduction under varying pressures induces interference. High-pressure wells impose backpressure on low-pressure wells, thereby restricting overall reservoir productivity. Accurate interference characterization is critical for efficient development. This study examines 42 gathering platforms within the Changning 201 Block. A three-tier surface gathering network hydraulic model (‘Platform-Gathering Station-Central Station’) was established. The model calculates key node pressures in the pipeline system following the integration of new wells. Unlike conventional interference studies that primarily focus on the reservoir scale and overlook the critical role of the surface gathering pipeline network as a propagation pathway for interference, this paper, for the first time, extends interference analysis from the “reservoir–wellbore” system to the full surface pressure system encompassing “wellhead-platform-gas gathering station-central station”. A transferable three-stage engineering decision-making workflow of “diagnosis-comparison-coordination” is proposed. This evaluates the extent to which the production of new wells at different development stages interferes with the pressure and productivity of existing gas wells, and enables a quantitative assessment of the influence of pressure-boosting technology on well deliverability and auxiliary measures. This research confirms that the model presents calculation errors of less than 3%. The commissioning of seven new wells with a combined capacity of 531,000 m³/d resulted in a total output increase of 626,900 m³/d at the central processing station; Platform CN-30 gas well deliverability decreased by 20.7%; the implementation of appropriate pressure-boosting technology was effective, enabling an average deliverability increase of 1.27 × 10⁴ m³/d per well, releasing the potential deliverability of the well. Full article

Helium-rich unconventional natural gas resources have attracted increasing attention from both academia and industry. A pronounced local enrichment of helium has recently been identified in coal-derived unconventional natural gas in the Sanjiaobei block on the eastern margin of the Ordos Basin. To clarify the main controls on helium enrichment in unconventional natural gas in this area and to guide the exploration of helium-rich resources, this study systematically examines the source of helium, its transport carrier, multiphase fractionation processes, and enrichment and accumulation pattern in natural gas. The analysis is based on conventional gas composition, helium volumetric content, carbon isotopes, and noble gas isotopes (He, Ne, and Ar) measured from wellhead gas samples collected from 11 production wells in the block, together with the regional deep structural evolution and hydrogeological conditions. The results show that: (1) the helium volumetric content of natural gas in the study area ranges from 0.0175% to 0.214%, with an average of 0.108%, and most wells fall within the high-helium grade category; (2) the helium isotope ratios ³He/⁴He (R/Ra) of the samples range from 0.0148 to 0.0824, indicating a typical crustal helium source; the good positive correlation between helium and nitrogen volumetric contents suggests that the two components share a highly consistent source affinity or common migration and accumulation behavior during fluid evolution; and the extremely high He/Ne ratios, on the order of 10⁴, together with excess Ar isotopes, indicate that the gases experienced little dilution by shallow atmospheric water or modern atmospheric fluids during migration and accumulation. The formation of helium-rich unconventional gas reservoirs on the eastern margin of the Ordos Basin is interpreted to be characterized by basement-derived helium supply, activation by tectonothermal events, groundwater transport, efficient fault-controlled migration, reservoir capture along migration pathways, and sealing by stagnant groundwater and lithologic barriers. On this basis, a helium enrichment model is established. This model depicts the geochemical evolution pathway of trace noble gases in a natural gas system and may provide a useful reference for helium resource evaluation in analogous areas. Full article

With continued expansion of offshore oil and gas development, the number of high-inclination wells has increased rapidly. During drilling of such wells, vibration transmission from the bottom drillstring to the wellhead is significantly attenuated. Therefore, even when severe vibration occurs at the bit, surface monitoring may not accurately reflect downhole conditions. To analyze axial and lateral vibration behavior, this study considers drillstring–wellbore contact and bit–formation interaction. Based on the Lagrange equation and the S–N fatigue curve, a dynamic model of the drillstring in offshore high-inclination wells is developed using the beam element method. A dynamic safety evaluation model is then constructed using the calculated dynamic characteristics, forming a mechanical analysis and optimization approach for drillstrings in these wells. The technique was applied in a branch well in the Bohai Oilfield. Drillstring vibration under different wellbore trajectories and drilling parameters was examined, and limit drilling parameters were selected through fatigue life analysis. The recommended configuration includes 24 drill collars, a weight on bit of 100 kN, and a rotation speed of 60 r/min. These optimization guidelines support improved drilling efficiency and help ensure drillstring safety in offshore high-inclination well applications. Full article

During natural gas production and transportation, multi-stage pressure regulation is often required to meet downstream pressure demands, resulting in substantial waste of residual pressure energy at high-pressure wellheads. This study focuses on high-pressure natural gas at the wellhead of the XC gas well in western Sichuan. Based on thermodynamic and exergy analysis, Aspen HYSYS was employed to simulate residual pressure power generation processes, and a systematic comparison was conducted between single-stage and multi-stage expansion schemes. Under operating conditions of an inlet pressure of 20 MPa, an inlet temperature of 70 °C, and a flow rate of 50 × 10⁴ m³/d, the influence of operating parameters on power generation performance was analyzed. The results indicate that power output increases with increasing natural gas flow rate and inlet temperature but decreases with increasing outlet pressure. Under large pressure differential conditions, single-stage expansion is unable to meet the requirements of high-pressure wellhead residual pressure power generation due to excessive temperature drop and limitations in existing expander performance. On this basis, two-stage, three-stage, and four-stage expansion power generation processes were further developed, and the effects of intermediate pressure selection on power output, heating demand, and pressure energy recovery efficiency were systematically examined. The results show that operating under equal expansion ratio conditions enhances pressure energy utilization. By comprehensively comparing power generation performance, heating power requirements, and economic feasibility, the two-stage expansion scheme was identified as the most favorable option under the investigated operating conditions, providing a practical reference for process design and engineering applications of high-pressure natural gas wellhead residual pressure power generation. Full article

During managed pressure drilling (MPD), gas influx intensifies the nonlinear relationship between choke valve opening degree and wellhead back pressure, causing conventional PID controllers to suffer from prolonged settling time and excessive overshoot. This paper proposes an automatic wellhead back pressure control method based on pressure–opening degree dual-layer cooperative feedback. The outer layer rapidly positions the choke valve near the target opening degree through a pressure drop–opening degree mapping model. The inner layer employs a PID controller tuned by an improved Dung Beetle Optimizer (DBO) for fine pressure regulation. The improved DBO introduces Logistic chaotic map initialization and an adaptive inertia weight to enhance global search capability, and adopts a comprehensive fitness function integrating the ITAE criterion with engineering safety constraints. Simulation results show that, compared with the Ziegler–Nichols (Z-N) method, the improved DBO-tuned PID reduces overshoot by 83.9% and settling time by 78.0%. Gas–liquid two-phase flow laboratory experiments were conducted with gas void fractions of 0–46.6%. Using manual control (average settling time of 50 s) as the benchmark, the dual-layer system equipped with the improved DBO-PID reduces settling time to 25 s (a 50% reduction), maximum overshoot absolute error to 0.009 MPa (a 74% reduction compared with Z-N-tuned PID), and achieves a mean absolute error of 0.004 MPa during continuous pressure tracking with zero overshoot. Both simulation and experimental results confirm that the synergy between the dual-layer control architecture and the improved DBO-PID enables rapid regulation and stable tracking of wellhead back pressure under gas–liquid two-phase flow conditions. Full article

To achieve high-precision and real-time quantitative evaluation of gas production in underground gas storage (UGS), this study focused on 11 typical injection-production wells in the Sudong UGS group. To address the common challenges posed by deviated well structures and complex wellbore temperature field distributions, a gas flow-rate calculation method based on Distributed Temperature-Sensing (DTS) data was developed. By standardizing the processing of multi-well temperature data, deviated wellbore trajectories were straightened to convert measured depth (MD) to true vertical depth (TVD). By incorporating a geothermal correction mechanism, temperature anomalies closely related to fluid flow were extracted, and a spatially unified temperature field model was constructed. On this basis, a “Dual-Point Temperature Difference Method” is proposed as a novel approach for single-well production evaluation. Based on thermodynamic phenomena such as the Joule–Thomson effect and expansion cooling, two critical sensing points, upstream and downstream of the production layer, were selected, with their temperature anomaly difference (∆T) serving as a sensitive indicator of flow rate variations. Combined with downhole pressure parameters and synchronized wellhead metering data, a nonlinear quantitative relationship model between ∆T and gas production rate Q was established, enabling accurate conversion of wellbore thermal response to macroscopic flow parameters. The results indicated that the gas production rates calculated by this method align well with traditional wellhead metering data, with errors maintained within engineering tolerances. Notably, the method demonstrates higher reliability and corrective capabilities in wells with drifting or faulty meters. This achievement breaks the reliance of traditional methods on specific layers or mechanical meters. It enables the effective application of multi-well, full-section, and non-contact temperature data in gas volume assessment. This research provides new technical support for dynamic monitoring, efficient operation, and remaining gas evaluation of UGS, offering significant prospects for engineering applications. Full article

Pressure swing adsorption (PSA) is a viable method for separating hydrogen from gas mixtures, an important aspect of long-term hydrogen storage in depleted gas fields. This study explores optimizing a 12-step PSA process for recovering high-purity hydrogen from varying compositions of hydrogen–methane mixtures, simulating the conditions likely encountered during hydrogen storage and recovery. Step-time optimization was performed on four different hydrogen–methane mixtures using the toPSAil simulation package—an open-source dynamic PSA simulator developed by researchers at the Georgia Institute of Technology—integrated with a particle swarm optimization (PSO) algorithm. The goal was to develop an optimization framework that can reliably identify PSA step times for different operating scenarios and satisfy specified purity and recovery constraints under fluctuating wellhead feed conditions. The optimization converged within 25–30 iterations, even in high-contaminant, low-pressure scenarios, where PSA performance is traditionally weak. The product purity in the optimized cycles was above 99.1% with more than 80% recovery for all cases, while fuel cell quality (99.7%) hydrogen was achieved in two out of the four scenarios. The purge-to-feed ratio of the best-performing cycles was between 0.07 and 0.32. These findings show the potential of the proposed approach in overcoming the difficulty of designing PSA cycles for non-constant gas compositions and achieving a hydrogen purification process suitable for variable feed conditions. The workflow generates a large synthetic dataset that can support surrogate or hybrid modeling. The results can help advance research in other gas separation areas with non-constant conditions, like flue gas or biogas purification. Full article

Multi-level models are core artifacts of Model-Based Systems Engineering (MBSE) for cross-disciplinary collaboration and staged evolution, yet assessing their maturity in the conceptual design phase remains difficult. This paper proposes a systematic, model-centric maturity assessment method for instrumentation conceptual design. By tailoring ISO/IEC 25010 to instrumentation characteristics, we establish a seven-dimensional quality attribute framework (functional suitability, performance efficiency, interaction capability, reliability, maintainability, flexibility, and structural completeness) and an L0–L4 maturity scale for multi-level MBSE models. The indicators are structured using a Quality Attribute Utility Tree. CRITIC derives the objective weights by jointly considering the score dispersion and inter-indicator correlation, and Dempster–Shafer evidence theory is used to map the indicator values and expert ratings onto basic belief assignments and fuses the multi-source evidence to the output maturity levels with explicit confidence and uncertainty. A case study of an automatic dosing instrument for solid foam drainage agents at a high-pressure gas wellhead yields an overall maturity of $L_1$ (Structured), with $BetP\left(L_1\right)= 0$.424, and an overall unknown mass of 0.186. The results highlight reliability and performance efficiency as the main bottlenecks and support targeted model refinement and resource allocation in early-stage design. Full article

Suction anchors play an important role in the exploration and development of marine natural gas hydrate (NGH). Suction anchors increase the bearing capacity and reduce tilting or sinking risk of underwater wellheads in the exploration and development process. This study proposes a dynamic failure analysis procedure for suction anchor installation based on the DBN-GO method. Firstly, a Goal-Oriented (GO) model is established by analyzing the human and equipment factor nodes in the suction anchor installation operation process. A Bayesian Network (BN) analysis model is set up by mapping the key nodes in the GO model. Then, the Cognitive Reliability and Error Analysis Method (CREAM) and the Dempster–Shafer (D-S) evidence theory are used to quantify the failure probabilities of human and equipment factor nodes in the BN model. The main risk factors are identified using Bayesian backward inference. Finally, the dynamic risk assessment of the suction anchor installation operation is conducted, considering the equipment node transition probability of the BN. Tkae the second production test of natural gas hydrates in the South China Sea as a case study. The study result shows that the failure probability of the suction anchor installation operation is 0.298%, which is at a low-risk level. Suction pump pressure control is the most critical factor leading to human errors. Among the equipment factor, the reliability of the suction pump and the ROV is the most important. Dynamic Bayesian inference shows the risk gradually increases with time. A reasonable maintenance strategy is conducive to reducing the accumulated risks caused by the time-varying degradation of equipment performance. The results could provide significant support in risk management and decision-making for the suction anchor installation operation, which will further promote the environmental sustainability, operational safety and economic feasibility of marine natural gas hydrate development. Full article

This study addresses the challenge of annular gas migration control during the waiting-on-cement (WOC) period in managed pressure cementing for formations with narrow safe pressure windows. A dynamic pressure compensation optimization strategy is proposed by integrating a composite mechanistic model with experimental validation. Based on the hydration degree (T) model, a predictive model for static gel strength development was established. By coupling the gelation-induced suspension effect with cement slurry volumetric shrinkage, a static hydrostatic pressure decline model was developed. Experimental results indicate that the prediction errors of the proposed models are all within 7%, demonstrating improved accuracy compared with traditional empirical approaches and classical shear stress models. In addition, a testing methodology was developed to characterize pressure transmission efficiency during the WOC process, revealing its dynamic attenuation behavior. Experimental results show that when the static gel strength of anti-gas-migration cement slurry reaches 240 Pa, the pressure transmission efficiency ranges from 45% to 49%. Based on these findings, a wellhead backpressure calculation model incorporating the evolution of pressure transmission efficiency was established, providing a quantitative basis for annular pressure management during cement setting. Full article

To address the failure risks associated with long-term service of subsea Christmas tree-wellhead systems under the complex marine environment of the South China Sea, a multi-factor coupled mechanical analysis method is proposed to evaluate the system’s mechanical characteristics and ensure the safety of deepwater oil and gas production. A dynamic model of lateral vibration under seismic loading is established, considering the combined effects of earthquakes, ocean currents, and seabed soil resistance. Based on the actual operating parameters of a well in the Lingshui area of the South China Sea, a three-dimensional finite element model of the subsea Christmas tree-wellhead assembly was developed in ABAQUS 2023. The combined effects of ocean currents, seismic loading, and corrosion over long-term service were simulated to compute and analyze the distributions of stress, bending moment, and associated failure risk. The results indicate that, under a once-in-a-century current combined with seismic waves of intensity V–VI, the system risk remains controllable. However, when the seismic intensity exceeds level VII, the maximum stress and bending moment reach 324.9 MPa and 6.02 MN·m, respectively, surpassing the allowable limits for an X56-grade surface conductor. Considering corrosion effects over a 25-year service life, the extreme stress values increase by 1–5% while the bending moment increases slightly; corrosion significantly amplifies the system’s failure risk. An analysis of the mudline burial height of the subsea wellhead during long-term service shows that, within a range of 1–7 m, variations in system loading are minimal. Based on the mechanical characteristics analysis, it is recommended that the design of subsea Christmas trees and wellheads incorporate regional seismic history, specify X56-grade surface conductors to mitigate corrosion effects, and install leakage-monitoring devices at critical locations to ensure the long-term service safety of the subsea Christmas tree-wellhead system. Full article

With the deepening of oil and gas exploration and development into ultra-deep and ultra-high pressure environments, the pressure of wellhead equipment is becoming higher and higher. The sealing performance of the casing head hanger is directly related to the safety and reliability of the whole wellhead equipment. Firstly, based on the numerical simulation method, the sealing performance of three different metal seal rings—H-type, X-type, and U-type—under 175 MPa working conditions is compared and analyzed. The simulation results show that the sealing performance of the H-type metal sealing ring is better than that of the X-type and U-type. The parametric analysis method is further used to study the influence of the structural parameters of the convex radius and the bottom angle of the H-ring on its sealing performance. The results show that when the convex radius is designed to be 3 mm, and the bottom angle is 90°, the effective contact width reaches 5.91 mm, and the contact uniformity is the best. Finally, based on the H-type metal sealing ring sample trial-produced with optimized parameters, a 175 MPa nitrogen medium sealing pressure test was completed on an 8 1/8” all-metal sealed mandrel casing hanger. The test results show that the system pressure drop is 0.7 MPa during the 5-min pressure stabilization process, which has good sealing reliability. Full article