Constant-rate depressurization, with control of the depressurization rate, has been proven to efficiently enhance hydrate dissociation in simulated confined natural gas hydrate (NGH) reservoirs. However, for unconfined reservoir simulation systems, the effects of depressurization rate on hydrate dissociation and gas production remain unknown. In this study, a stratified NGH reservoir environment was built to investigate CH4 hydrate dissociation in unconfined systems with varied depressurization rates. The results showed that the depressurization rate not only influenced heat and fluid transport within the original pore fluids, but also altered the flow pathways of the overlying water intruding into the reservoir. These changes affected the utilization efficiency of the sensible heat and the reformation characteristics of CH4 hydrates in the hydrate reservoir, resulting in significant spatial heterogeneity in the temperature and flow fields. Depressurization rate significantly influenced both CH4 recovery from NGH reservoirs and CH4 leakage into the overlying environment. By optimizing the depressurization rate to a moderate 0.10 MPa/min to balance factors such as overburden sediment collapse, overlying water intrusion, and hydrate dissociation, the CH4 recovery ratio increased by up to 17.17%, reaching 77.00%, while the CH4 leakage ratio decreased by as much as 11.12%, to 6.50%.

Understanding the dynamic evolution of gas hydrates within hydrophobic fine-grained sediments remains a significant challenge for predicting natural hydrate heterogeneity and for improving production strategies. However, the mechanism controlling the hydrate spatial heterogeneity and temporal evolution during phase changes are poorly understood. To address this, we investigated the formation and dissociation dynamics of gas hydrates in hydrophobic porous media using in situ X-ray computed tomography (X-CT). We observed a distinct boundary-driven growth mode, termed "wall-climbing", in which hydrates preferentially accumulated as massive aggregates with isolated pores at the upper region of the sediment, rather than forming uniform pore-filling hydrates within the internal matrix. During depressurization-induced dissociation, the decomposition of boundary-localized hydrate triggers fluid redistribution and substantial secondary hydrate formation in the lower sediment pores, highlighting a non-equilibrium self-organization pathway during decomposition. We elucidate the dynamic mechanism of gas hydrates in hydrophobic sediments by linking the wall-climbing effect and secondary formation to coupled effects of wettability-controlled capillary redistribution, preferential migration pathways, gravity, and boundary-localized heat transfer. We further propose a field-relevant conceptual analogy in which similar interface-driven accumulation and redistribution may occur at natural high-contrast boundaries, such as fractures, seep conduits, sediment-carbonate interfaces. These findings provide mechanistic insights into hydrate heterogeneity and dynamic redistribution, with implications for gas recovery, flow assurance, and interpretation of cold seep hydrate architectures.

Unlike conventional oil and gas reservoirs, hydrate-bearing reservoirs are generally unsealed, making methane leakage control critical for environmental safety. Previous studies have mainly examined hydrate dissociation and production enhancement in sealed systems, whereas leakage behavior in unsealed reservoirs remains poorly understood. Here, a self-developed experimental simulator was used to construct a submarine-stratified environment and assess how different placements of multilateral horizontal wells influence hydrate dissociation and methane leakage. Results showed that varying the placement of a single horizontal well did not alter final gas and water production, but it modified the flow space of low-temperature overlying water, thereby affecting hydrate dissociation efficiency and methane leakage. The upper-well configuration reduced ineffective sensible heat loss and shortened reservoir temperature recovery, but also produced the highest methane leakage ratio of 13.55%. Under the dual horizontal well configuration, randomly occurring delayed failure of the overlying sediment layer reduced secondary hydrate formation caused by seawater intrusion, improved production continuity and final gas yield, and lowered methane leakage to 1.21%. These findings provide a theoretical basis for the safe and efficient development of marine natural gas hydrates.

The extraction of natural gas hydrates faces challenges due to unresolved in situ decomposition and permeability mechanisms, with reservoir permeability being a pivotal parameter for extraction safety, efficiency, and economics. This study addresses this by developing a novel competition model and models reconstructed via a multi-point statistical method based on real CT images. Using the lattice Boltzmann method, we examine the influence of key factors, such as porosity and saturation, on permeability. Since single-hydrate-morphology models often fail to match practical observations, we propose a competition model that describes the dynamic transition from grain-coating to pore-filling habits. Simulations show that predictions from the competition model converge more closely with experimental data than single-state models. Furthermore, the MPS-based reconstructions provide a realistic benchmark, validating the representativeness of the modeling approaches. The framework demonstrates promising potential for capturing diverse sedimentary scenarios, indicating wide applicability and avenues for future research.

Grain boundaries are an important part of many polycrystalline mineral aggregates, possessing unique geometries and chemistries but they are often poorly understood due to the many complexities of studying such large geometrically diverse regions. In this work we shall examine the surfaces of the mineral forsterite in order to understand their controlling behaviour and mechanisms. We shall use a combination of density functional theory and both machine learning and classically trained forcefields. We find that for purposes of partitioning and surface energies most grain boundaries are similar to their constituent planar surfaces. Our main finding is that the relative energies of forsterite surfaces are highly sensitive to T and P and that their planar distributions are not static in real environments. Increasing T at low P can lead to growth of (010) surfaces while increasing T and P together can lead to the growth of (111) surfaces. In mantle conditions we predict a strong favourability of (111) surfaces that increases with depth but with large, sometimes non-monotonic shifts in the favourability of other surfaces. We also demonstrate that changing the surface distribution can lead to changes in crystal properties. The high temperature stabilisation of (010) is driven by a novel collective motion of Mg atoms along [100] channels which will also lead to a large, non-linear, anisotropic increase in grain boundary diffusion as (010) surfaces grow with temperature. We show that partitioning of water to forsterite surfaces is highly surface specific and driven by local chemistry enabling the possibility of hidden reservoirs in the Earth produced by changing surface plane distributions.

Natural Gas Hydrate (NGH), as a significant and promising energy resource for advancing low-carbon development, has long been the focus of global energy resource research. The research on the extraction methods of submarine natural gas hydrate has attracted much attention. Recently, the most promising production method is depressurization, but the regular depressurization method is difficult to meet the efficiency requirement for commercial production. Therefore, it is necessary to innovate the depressurization method in order to develop a more effective approach for NGH production. The Pilot-scale Hydrate Simulator (PHS), with a volume of 117.8L, was employed in this study to conduct four NGH decomposition experiments with horizontal well under different methods including the Regular Depressurization (RD), the Cyclic Depressurization Above the Quadruple point (CD-AQ), the Cyclic Depressurization at the Quadruple point (CD-Q), and the Cyclic Depressurization Below the Quadruple point (CD-BQ). The experimental results show that the horizontal well exhibits higher production efficiency than the vertical well with the CD-AQ mode. When horizontal well is adopted, compared with the RD, the CD-AQ, the CD-Q, and the CD-BQ all enhance gas production efficiency and hydrate decomposition rate. Among three cyclic methods, lower starting pressure results in greater gas output. In the CD-BQ mode, with an initial pressure of 2.2 MPa, ice formation occurs during the process, which not only hinders gas production but also introduces potential safety risks. Therefore, CD-BQ requires specific geological conditions to be viable. In contrast, CD-Q significantly improves hydrate decomposition efficiency while maintaining process stability during both the depressurization and cyclic depressurization stages. This method optimizes both the well type and the cyclic pressure range, providing a new strategy for the NGH commercial development. Further studies on better optimization methods can be conducted based on this.

Deep-sea cold seeps provide an interdisciplinary research window where geological dynamics, energy resource exploitation, and extreme ecosystems converge. We reported a coupled experimental system that enabled the integrated and cross-disciplinary investigation of energy development (methane extraction and leakage), geological processes (methane migration), and biogeochemical dynamics (multi-path transformations of methane and cold seep ecosystem evolution), thereby addressing the fragmented understanding of deep-sea methane systems caused by disciplinary separation. The validation experiment revealed three representative phenomena: (1) the coexistence of high- and low-temperature zones during depressurization, (2) secondary hydrate formation triggered by overlying water intrusion, and (3) characteristic resistivity responses associated with methane leakage. Importantly, this work provides a scalable interdisciplinary research paradigm that further links pilot-scale experiments with field-scale studies on marine methane dynamics and cold seep ecosystem evolution.

International field trials have demonstrated that sand production and control are crucial issues that need to be addressed and resolved to achieve the commercial exploitation of natural gas hydrate (NGH). The objective of this study is to investigate sand migration and control in sediments with different particle size distributions during depressurization-induced hydrate exploitation. A 50PPI (pores per linear inch) polyurethane foam was chosen as the sand control material to further explore its performance under conditions closer to actual field reservoirs, which is the continuation and extension of previous investigations. Experimental results confirm that the 50 PPI polyurethane foam demonstrates good sand control effectiveness for reservoirs with a median particle size (D 50) of quartz sands ranging from 10 to 100 mu m, even under material extrusion deformation. Under comparable reservoir conditions, finer and more heterogeneous sediments increase sand control requirements. Meanwhile, no definitive correlation between internal sand migration and actual sand production was observed. In reservoirs with fine quartz sand, sand production manifests as consolidated sediment migration after hydrate exploitation, while heterogeneous quartz sand reservoirs undergo significant internal changes before and after the NGH exploitation, accompanied by a evident decrease in gas production rate. Based on the experimental study, a theoretical framework for sand migration and production mechanisms during NGH exploitation is proposed, defining three distinct states. The state of sand migration shifts when local blockages reach a threshold, transitioning from particle migration to block displacement.

Coral biomineralization typically yields either aragonite (in most scleractinians) or calcite (in octocorals), yet the drivers of this polymorph choice remain debated. Here we report a deep-sea gorgonian coral (Callogorgia sp.) with a coaxial calcite-aragonite-calcite skeleton. Growing at 1,400 m under nearly constant temperature and seawater chemistry, this specimen rules out environmental forcing as a control. High-resolution elemental mapping, Raman microscopy, and infrared nano-spectroscopy show that acidic, aspartate-rich macromolecules are enriched in the calcitic layers but depleted in the aragonitic layer. These macromolecules lower the nucleation barrier for calcite while inhibiting aragonite growth, driving abrupt, layer-by-layer phase switches. Temporal shifts in macromolecule distribution correlate with biological imprints, implying regulation via changes in calcifying tissues or symbionts. Our results provide direct in situ evidence that organic molecules, rather than external conditions, govern carbonate polymorph selection in octocorals, offering a natural template for biomimetic control of CaCO3 phase architecture.

Natural gas hydrates (NGHs) are recognized as a promising strategic green energy source due to their vast reserves and high energy density. Understanding their growth kinetics is of great significance for the comprehensive utilization of hydrates. However, the time-dependent hydrate growth kinetics remain unknown due to the difficulty of directly revealing the local growth behavior of hydrate crystals and the underlying controlling mechanisms. To address this unsolved problem, a newly developed 3D high spatiotemporal resolution in-situ visualization platform was employed to characterize the hydrate phase transition habits, aiming to explore influencing factors of morphological evolution and growth kinetics of gas hydrates from a microscopic perspective. Our results show that higher subcooling degree increases the morphological irregularity of hydrate crystals. More importantly, we found that the apparent kinetic parameter (Kapp) is not a constant; instead, the increase in crystal size leads to a significant reduction in Kapp. The change in kinetic parameter is attributed to the rise in crystal surface temperature caused by the exothermic heat released during hydrate growth. Meanwhile, once the crystal size reaches a certain threshold, the geometric effect becomes the dominant factor limiting the hydrate growth kinetics. Based on these in-situ time dependent hydrate growth observations, this study reveals the dynamic “morphology-volume” coupling mechanism of gas hydrate growth. Our findings provide mechanistic insights and theoretical support for the prediction and regulation of hydrate growth rates in the comprehensive utilization of gas hydrates.

Deep sea microorganisms remain largely inaccessible because existing sampling and cultivation methods fail to preserve native high-pressure microenvironments from seafloor to laboratory. Here we show a closed-loop cyber physical platform that maintains in situ deep-sea conditions through real-time sensing, digital twin control and robotic high-pressure manipulation to enable targeted isolation of extremophiles. The system integrates intelligent site selection, active pressure retention and multimodal vision–tactile feedback to automate colony recognition with 94.6% accuracy and perform compliant streaking and picking, enabling the recovery of deep-sea-adapted strains from cold seep environments. These results establish a sensor-driven framework for standardized exploration of the deep biosphere and provide a generalizable approach for isolating microorganisms from environments inaccessible to conventional methods. A closed-loop cyber physical platform that preserves native deep-sea microenvironments enables fully automated in situ cultivation and isolation of extremophiles through sensor-driven sampling, pressure retentive handling and robotic high-pressure manipulation.

Natural gas hydrates play a critical role in energy resource development and geological stability. Their phase transition is accompanied by significant volume expansion and thermal effects. To enable in situ, high-precision monitoring of this process, this study develops a multiparameter sensing system based on fiber Bragg grating (FBG) sensors. Water-ice freezing-thawing experiments were first conducted as a reference system to characterize baseline liquid-solid phase transition-induced strain behavior in sediments. Subsequently, temperature-controlled formation and dissociation experiments of tetrahydrofuran (THF) hydrate were performed to systematically investigate hydrate-induced strain responses. The effects of sediment grain size, hydrate saturation, and the spatial positioning of FBG sensors on phase change responses were analyzed, and the evolution of strain rate and spectral response during phase transitions was thoroughly investigated. Results demonstrate that FBG sensors can sensitively capture strain fluctuations induced by phase transitions, with strain amplitude positively correlated with hydrate saturation. Fast Fourier Transform (FFT) analysis of strain-rate signals successfully identified characteristic frequency bands and energy distribution patterns associated with phase transitions in sediments of different grain sizes. Furthermore, finer-grained sediments and higher hydrate saturation levels are associated with markedly larger strain amplitudes and more pronounced strain-rate responses during phase transition processes. Finally, a quantitative inversion model linking FBG parameters to hydrate saturation was developed, and the predicted values showed excellent agreement with experimental data. This study demonstrates the reliability of FBG-based monitoring for tracking hydrate evolution and provides essential experimental support for geological risk assessment during hydrate extraction.

The influence of salt on gas hydrates formation in pores is important for the efficient exploitation of gas hydrates in actual sediments. In this study, the experiments of methane hydrate formation in pores with different concentrations (0.00 wt%, 0.40 wt%, 1.00 wt%, 2.00 wt%, and 3.50 wt%) of sodium chloride (NaCl) brine were carried out in a glass micromodel. The effects of salinity on the micro growth morphology and growth rate of methane hydrate formed by free gas and dissolved gas in pores were studied. The results showed that, for the hydrate formed by free gas in pores, the hydrate was preferentially formed at the gas-liquid interface and then grew toward the gas body center. The hydrate growth rate along the gas-liquid interface (vinterface) was 100 to 150 times higher than that toward the gas bubble center (vcenter). Meanwhile, with the increase of salt concentration, the vinterface decreased. However, for the vcenter, it increased first and then decreased with the increase of the salt concentration, and the maximum average vcenter was obtained in the pores containing 0.40 wt% NaCl brine. The possible promotion mechanism of NaCl on the vcenter was analyzed in detail. For the hydrate formed by dissolved gas, the hydrate growth rate decreased with the increase of the distance between the hydrate growth front and the surrounding free gas bubble, and it also decreased with the increase of the salt concentration in pore water. This work is helpful in understanding the influences of salt on the microscopic growth characteristics of hydrate formed by free gas and dissolved gas in pores, so as to provide guidance for the efficient exploitation of gas hydrates.

In this study, a hybrid composite of MXene loaded with carbon-coated Ni0.96S hollow nanobox (shortened as HC-Ni0.96S@MXene/C) is successfully synthesized. The micro-structure of HC-Ni0.96S@MXene/C is further analyzed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) with EDS mappings. The results reveal that similar to 550 nm Ni0.96S nanobox with similar to 60 nm shell is effectively loaded on MXene nanosheets and encapsulated by a thin carbon layer. When evaluated as advanced anode for lithium-ion batteries (LIBs), HC-Ni0.96S@MXene/C achieves a specific capacity of 810.9 mAh g(-)(1) at 0.1 A g(-)(1) and remains 455.6 mAh g(-)(1) at 0.5 A g(-1) after 200 cycles. Moreover, in sodium-ion batteries (SIBs), HC-Ni0.96S@MXene/C anode delivers 416.5 mAh g(-)(1) at 0.05 A g(-)(1) and maintains 201.4 mAh g(-)(1) at 0.5 A g(-)(1) after 400 cycles. Additionally, the HC-Ni0.96S@MXene/C anode demonstrates higher pseudo-capacitance effects of 81.6 and 92.5 % at a scanning rate of 1 mV s(-)(1) in LIBs and SIBs respectively. Moreover, the higher pseudo-capacitance effects in SIBs are according with the facts that the ionic diffusion coefficients of Na ions (DNa+ = 4.6 similar to 40.6 x 10(-11) (discharge) and 1.7 similar to 127.8 x 10(-11) (charge) cm(2)/s) are larger than those of Li ions (DLi+ = 1.1 similar to 19.6 x 10(-11) (discharge) and 0.82 similar to 32.6 x 10(-11) (charge) cm(2)/s) for HC-Ni0.96S@MXene/C anode. The excellent electrochemical performances of HC-Ni0.96S@MXene/C should be assigned to hollow Ni0.96S structure, carbon coating and conductive MXene nanosheets, which collectively alleviate volume changes during cycling, enhance electronic conductivity and accelerate ion diffusion respectively. This strategy of synthesizing HC-Ni0.96S@MXene/C may provide a guidance for designing advanced LIBs/SIBs anodes in the near future.

Natural gas hydrate is an alternative energy source with both reserve advantages and environmental friendliness. Thermal stimulation is a common method for extracting natural gas hydrate, and how to improve the extraction efficiency of natural gas hydrate by optimizing the layout of thermal injection well pattern is a subject worthy of in-depth exploration. This study conducted three sets of hydrate decomposition experiments in a pilot-scale hydrate simulator (PHS) with an effective volume of 117.8 L under different thermal injection well pattern conditions, including single-point heating, two-point heating, and four-point heating. The gas-water production characteristics and heat transfer processes of the three experimental groups were analyzed, and the real-time decomposition rate and energy efficiency ratio of hydrate decomposition under different extraction methods were quantitatively investigated. Experimental results show that under conditions of consistent total heating rate and hydrate saturation, the cumulative gas production of the experiments remained essentially the same, but increasing the density of heat source arrangements shortened the hydrate extraction time. Compared with twopoint and single-point heating, four-point heating intensified heat diffusion, but the reservoir temperature gradient in the four-point heating system decreased compared to single-point and two-point modes. Increasing the density of heating points improved heat exchange efficiency, but the dispersed arrangement of heat sources also increased heat losses. The two-point configuration exhibited the highest gas production rate and energy efficiency ratio, followed by four-point, while single-point showed the lowest values. These results may hold implications for optimizing thermal injection well patterns in trial production projects and future commercial exploitation of natural gas hydrates.

Crude oil catalytic pyrolysis process become an effective solution to satisfy olefin demand and achieve dual-carbon goal, while the integration of artificial intelligence and chemical process can realize breakthrough in rapid technology amplification. However, there is still a lack of molecular-level simulation research on fullfraction oil catalytic process. In this study, molecular-level kinetic model of shale oil catalytic pyrolysis was first established. A feedstock molecular matrix containing 1691 vectors of all fractions was established using molecular reconstruction. Differential reaction rules of multi-level hydrocarbon structures were established, leading to automatic generation of catalytic pyrolysis reaction network. Based on this model, we finished quantitative calculation of hydrocarbon distribution in reaction process, and established correlation between reaction conditions and product distribution. Optimal reaction condition range was determined to reaction temperature of 690-700 degrees C and residence time of 4-4.5 s. In addition, this model obtained reaction competition proportional calculation module by decoupling reaction network, realizing quantitative correlation between reaction pathway and product distribution. Finally, a process simulation software including reaction condition optimization and process deep analysis functions was developed, which could efficiently promote rapid amplification and large-scale application of new chemical processes.

To elucidate the lost circulation mechanism in naturally fractured shale, this study employs fluid seepage theory and fracture deformation theory, assumes the polymer-based drilling fluid system behaves as a Herschel-Bulkley (H-B) fluid, and develops a calculation model for lost circulation pressure that comprehensively incorporates fracture geometry, fracture stress state, drilling fluid properties, and the pressure differential between the wellbore and the formation. Research shows that the lost circulation rate of drilling fluid increases with greater initial fracture width, fracture deformation index, fluid consistency coefficient, yield stress, and pressure differential between the wellbore and the formation, while it decreases with increasing fracture radial extension length, fracture roughness, drilling fluid density, and normal stress on the fracture surface. The initial fracture width, fracture radial extension length, and fluid consistency coefficient have a significant influence on the lost circulation rate of drilling fluid. In contrast, the effects of the fracture deformation index and dynamic yield stress are relatively minor, indicating that they are not the primary controlling factors of fracture-induced lost circulation.

Microplastics (MPs) are emerging soil contaminants that significantly affect the adsorption of co-existing pollutants in soil. This study systematically investigates the distinct roles of conventional polyethylene (PE), biodegradable polylactic acid (PLA), and their derived dissolved organic matter (MPs-DOM) in regulating pyrene adsorption in soil. The results demonstrate that both MPs enhanced pyrene adsorption, with PE exhibiting higher capacity (Qe = 4.09 mg g-1) and faster rate (K1 = 0.09 min-1) than PLA (Qe = 2.26 mg g-1). Aging further diverged their behaviors: PE increased its adsorption partition coefficient (Kd) by 58.80 % through developing a polar-hydrophobic interface with oxygen-containing groups, while PLA decreased Kd by 39.45 % due to enhanced hydrophilicity from ester bond cleavage. Crucially, MPs-DOM, characterized as predominantly low-molecular-weight proteins (>95 %), demonstrated a dual regulatory effect: at 5 mg C L-1, it enhanced ultimate adsorption capacity through micelle formation but concurrently retarded the adsorption rate by introducing hydrogen-bonding sites that modified soil microstructure and interaction pathways. These findings reveal that MPs-DOM operates through fundamentally different mechanisms compared to particulate MPs, predominantly involving protein-like component mediation rather than simple hydrophobic interactions. The study highlights the necessity of considering both particulate MPs and their persistent DOM derivatives in environmental risk assessments, particularly noting the contrasting long-term impacts of conventional versus biodegradable MPs on contaminant behavior in soil ecosystems.