Depressurization-Assisted CO₂/N₂ Replacement for Methane Recovery from Hydrate-Bearing Clayey Sediments

Energy & Fuels, Journal Year: 2025, Volume and Issue: unknown

Published: March 5, 2025

Natural gas hydrates (NGHs) are regarded as a secure and efficient renewable energy resource. Recovering methane (CH4) by injecting carbon dioxide (CO2) into NGHs is an innovative method for production greenhouse gases control. However, the replacement injection of CO2 CH4 recovery was constrained mass transfer permeability limitations, leading to poor efficiency rate. Herein, depressurization-assisted CO2/N2 proposed enhance sequestration. In this study, coupled experiment integrating mixed staged depressurization conducted in hydrate-bearing clayey (montmorillonite) sediments using custom-designed triaxial pressure reaction apparatus. The effects pressure, temperature, time were systematically analyzed. results indicate that there substantially enhanced sequestration compared condition without assistance, with remarkable increase from 21 85.7% 45.4 68.3%, respectively. integration effectively overcame physical barriers between hydrate phases, resulting 67.6% enhancement significantly accelerated postdepressurization study provide insight exploring low-carbon

Language: Английский

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Plugging Experiments for Ceramic Filling Layer with Different Grain Sizes Under Gas–Water Mixed Flow for Natural Gas Hydrate Development

Energies, Journal Year: 2025, Volume and Issue: 18(7), P. 1761 - 1761

Published: April 1, 2025

The natural gas hydrate reservoir in the sea area is shallowly buried and mainly composed of silty silt. sediment weakly consolidated has fine particles, which shows a higher sand production risk needs control. However, silt particles can easily cause blockages control medium, so balance between efficiency should be considered. At present, there lack reasonable effective measures to prevent pore blockage medium. In this study, influence formation on sand-retaining mediums under condition gas–water mixed flow discussed, plugging process analyzed. results show that: (1) Although ceramic have high sphericity regular shape, they form porosity permeability, but finer will also muddy reduce productivity. (2) experimental different ceramide filling schemes that Saucier’s empirical criteria are not suitable for development cannot directly used reference. order problem productivity reservoir, it recommended use 40 × 70 mesh as critical optimal condition. paper important guiding significance pre-filled screens formulation optimization schemes.

Language: Английский

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Submarine Continental Slopes Stability Prediction of Natural Gas Hydrates Based on Machine Learning

Offshore Technology Conference, Journal Year: 2025, Volume and Issue: unknown

Published: April 28, 2025

Abstract In the process of extracting naturally-occurring oceanic gas hydrates, dissociation hydrates can cause a reduction in soil strength. This has potential to trigger slope failure and submarine landslides, which present catastrophic threat offshore facilities hydrate production. research aims create robust accurate machine-learning model that efficiently predict stability continental slopes where are widespread. By collecting analyzing 144 relevant cases, comprehensive dataset was constructed, incorporating basic data, overlying underlying layer geological parameters layer. After conducting correlation coefficient analysis between characteristic output, key were determined. To assess its performance, four machine learning techniques employed: Random Forest (RF), XGBoost, K-Nearest Neighbors (KNN), Support Vector Machine (SVM). Formation physical parameters, geotechnical NGH taken as input prediction indicator. Evaluation metrics such ROC confusion matrix employed comprehensively evaluate these models’ classification ability. Among algorithms, RF algorithm achieves best accuracy AUC value, demonstrating natural hydrates. Additionally, sensitive using Gini impurity calculations revealed decomposition degree is most significant factor affecting stability, followed by burial depth thickness The angle, cohesion, internal friction angle also have impacts. study provides new perspective for predicting with offers scientific basis safe efficient exploitation.

Language: Английский

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Numerical study on gas production via a horizontal well from hydrate reservoirs with different slope angles in the South China Sea

Deep Underground Science and Engineering, Journal Year: 2024, Volume and Issue: 3(2), P. 171 - 181

Published: June 1, 2024

Abstract It is important to study the effect of hydrate production on physical and mechanical properties low‐permeability clayey–silty reservoirs for large‐scale exploitation in South China Sea. In this study, a multiphysical‐field coupling model, combined with actual exploration drilling data experimental cores laboratory, was established investigate different slope angles during 5‐year by depressurization method via horizontal well. The result shows that permeability severely affects gas rate, maximum amount 20‐m‐long well can reach 186.8 m 3 /day production. Reservoirs smaller show higher rates. propagation dissociation mainly develop along direction parallel slope. Besides, mean effective stress concentrated near‐wellbore area on‐going production, gradually decreases increase angle. Different from distribution law, total reservoir settlement first then increases 0° angle up 3.4 m, displacement as high 2.2 after 5 years concluded pore pressure drop region Sea limited, various further lead differences strain resulting severe uneven reservoirs.

Language: Английский

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Experiment on Gradient Depressurization Gas Hydrate Breakdown in Sediments with Varied Saturation Levels

Energy & Fuels, Journal Year: 2024, Volume and Issue: 38(3), P. 1977 - 1986

Published: Jan. 16, 2024

The depressurization method is considered to be one of the most promising gas hydrate extraction methods. With use a decomposition simulation test system, four gradient modes and intervals were under two saturation conditions, namely, 24–35 46–64%, simulate borehole pressure salinity in mining location. findings indicate that duration influenced by level saturation, with higher resulting greater decrease time compared lower levels when subjected decline 3 MPa. Specifically, times Run 2–2a, 3–2a, 4–2a at 46–64% 37.57, 21.57, 43.20%, respectively, relation 2–1a, 3–1a, 4–1a 24–35%. highest rates instantaneous observed early stages mining. Within larger drop, initial stage exhibited rate, while within interval, showed rate. Furthermore, peak rate decreased gradually as increased. mean speed varying degrees drop average fell 61.27, 64.64, 69.21%, those 1–2a. implementation has potential likelihood unforeseen reformation or cementation, raise efficacy output, maximum production, bolster stability hydrates, guarantee reservoir wellbore.

Language: Английский

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Hydrate Decomposition Inhibitors by Phase Change Cooling Storage Based on an Electrostatic Spraying Method

Energy & Fuels, Journal Year: 2024, Volume and Issue: 38(14), P. 12978 - 12988

Published: July 8, 2024

The heat transfer of drilling fluid to hydrate reservoir is the main cause decomposition and borehole wall instability. Impeding or retarding from key maintaining stability. In order intelligently control temperature in wellbore, phase change microcapsules were prepared using an innovative method electrostatic spraying physical cross-linking with mixed alkane as core material sodium alginate shell material. This synthesis can particle size microcapsules. characterized by SEM, optical microscopy, analyzer. experimental results presented that latent melting 158.04 J/g, solidification 161.63 J/g. addition, also have excellent thermal stability, conductivity coefficient 0.384 W/(m·°C). experiment show effectively delay hydrates. These provide valuable insights into a better understanding rational development high-performance inhibitors for fluids construction systems.

Language: Английский

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Seafloor Subsidence Evaluation Due to Hydrate Depressurization Recovery in the Shenhu Area, South China Sea

Journal of Marine Science and Engineering, Journal Year: 2024, Volume and Issue: 12(8), P. 1410 - 1410

Published: Aug. 16, 2024

Submarine hydrate mining can trigger geological disasters, including submarine landslides and seafloor subsidence due to excess pore pressure weakened layers, which may potentially lead the reactivation of faults increased seismic activity. However, current research encounters challenges in assessing geotechnical issues associated with long-term large-scale production from well grids located sloped areas. Limited by complexity sediment, a multifield coupled numerical model slope Shenhu area was established. Utilizing modified Mohr–Coulomb as constitutive for hydrate-bearing sediments track dynamic reduction strength employing shear method assess stability, series depressurization strategies are applied evaluate risks subsidence. Results show that dissociation tends stagnate after period mining. The decomposed is severely reduced, volume deficit occurs this area, causing formation displacement. peripheral region compacted high stress, resulting serious decrease permeability porosity, limits continued decomposition hydrates. hydrates will not appear block. several meters’ over wide range engineering safety significantly. amount first 50 days approximately half final settlement. A higher drop speed up recovery rate while more significant slippage. Therefore, balance between stability needs work.

Language: Английский

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An adversarial multi-source transfer learning method for the stability analysis of methane hydrate-bearing sediments

Computers and Geotechnics, Journal Year: 2024, Volume and Issue: 177, P. 106868 - 106868

Published: Nov. 3, 2024

Language: Английский

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