Seepage Areas Research Articles

Evaluation of Nong’an oil shale reservoir stimulation based on nitrogen injection

Reservoir stimulation for in-situ oil shale conversion employed hydraulic fracturing, as demonstrated in the Nong’an oil shale in-situ conversion project. This study examines the extent of reservoir stimulation and the associated changes in permeability. Hydraulic fracturing significantly increased the reservoir stimulation volume, raising the permeability in the stimulated area to 324.6 mD. Subsequent water replacement involved injecting lower-temperature nitrogen, which mitigated volume shrinkage and closed microfractures. However, this process reduced permeability by 80.54%, decreasing the seepage area to 2660.7 m3. The gas injection and mining process encompassed two stages: warming and cracking. The former aimed to enhance the drying of the formation in the stimulation area, restoring 22.87% of the permeability of the original area. The latter stage facilitated organic matter decomposition to release hydrocarbons, increasing the permeability of the reformed region to 704.842 mD. The reservoir-stimulated area can be categorized into cracking, high seepage, or low seepage zones, depending on the difficulty of injected gas flow and the extent of high-temperature influence.

The Identification and Quantification of Hidden Hazards in Small Scale Reservoir Engineering Based on Deep Learning: Intelligent Perception for Safety of Small Reservoir Projects in Jiangxi Province

This study aims to enhance the detection and assessment of safety hazards in small-scale reservoir engineering using advanced image processing and deep learning techniques. Given the critical importance of small reservoirs in flood management, water supply, and ecological balance, the effective monitoring of their structural integrity is crucial. This paper developed a fully convolutional semantic segmentation method for hidden danger images of small reservoirs using an encoding–decoding structure, utilizing a deep learning framework of convolutional neural networks (CNNs) to process and analyze high-resolution images captured by unmanned aerial vehicles (UAVs). The method incorporated data augmentation and adaptive learning techniques to improve model accuracy under diverse environmental conditions. Finally, the quantification data of hidden dangers (length, width, area, etc.) were obtained by converting the image pixels to the actual size. Results demonstrate significant improvements in detecting structural deficiencies, such as cracks and seepage areas, with increased precision and recall rates compared to conventional methods, and the HHSN-25 network (Hidden Hazard Segmentation Network with 25 layers) proposed in this paper outperforms other methods. The main evaluation indicator, mIoU of HHSN-25, is higher than other methods, reaching 87.00%, and the Unet is 85.50%, and the Unet++ is 85.55%. The proposed model achieves reliable real-time performance, allowing for early warning and effective management of potential risks. This study contributes to the development of more efficient monitoring systems for small-scale reservoirs, enhancing their safety and operational sustainability.

Gulf Stream mesoscale variabilities drive bottom marine heatwaves in Northwest Atlantic continental margin methane seeps

Methane hydrates on continental margins sequester substantial amounts of methane. Ocean warming often triggers hydrate dissociation, influencing global climate and marine ecosystems. Here we use ocean reanalysis to investigate bottom marine heatwaves affecting methane seeps at the Northwest Atlantic continental margin. These heatwaves are driven by downward displacement of ocean subsurface isopycnals that brings anomalously warm water to the seafloor, which frequently lacked surface expressions. The isopycnal anomalies are generated by the interaction of Gulf Stream mesoscale activity and slope topography, including warm core ring intrusions and impingements at the tail of the Grand Banks. Once generated, the isopycnal anomalies propagate along the slope and affect the seep area via topographic Rossby waves, offering predictability for bottom marine heatwaves. A northward shift and increasing instability of the Gulf Stream has intensified bottom marine heatwaves at the seep area since 2009, and future climate change will likely exacerbate this trend.

Characterizing coastal aquifer heterogeneity from a single piezometer head chronicle

We propose a new method for identifying the hydraulic properties of coastal aquifers based on their response to continental and marine influences observed from isolated piezometers displaying both tidal and seasonal fluctuations. From a single piezometer, a first approximation of hydraulic conductivity and porosity can be derived analytically from the mean hydraulic head and its tidal fluctuations. If this approximation also allows a correct simulation of seasonal head variations, the aquifer can be modelled as homogeneous. Otherwise, the seasonal head variations provide constraints on the heterogeneity of hydraulic properties. This new method is applied to a coastal aquifer in Normandy, formed by a relatively flat, kilometer-wide coastal strip of Quaternary sands followed by a foothill of higher Brioverian shales. Hydraulic head variations monitored daily for 8 years in a piezometer located in the Quaternary sand formation enable us to constrain their hydraulic conductivity (5–20 m.d−1) and porosity (7–10 %) within restricted ranges. They also suggest the existence of a significantly more porous formation (15–30 %) upstream of the observation piezometer, which could consist of more porous sands or fractured shales. In the case of limited surface–subsurface interactions, the identification method relies on a step-by-step combination of analytical solutions and simplified 1D numerical models. When more important surface–subsurface interactions are involved, a spatialized 2D model is used, that allows the analysis of seepage areas. Based on this case study, we gradually introduce 1D and 2D approaches, and discuss their applicability. We finally illustrate one major application of this approach by analyzing the interest of aquifer properties investigation on groundwater-induced flooding vulnerability.

Revealing the kinetic behaviors of hydrate formation on bubble surface with different pressure gradients in deep-sea methane seepage areas of the South China Sea

In the deep-sea methane seepage environment, hydrate formation on the methane bubbles is a crucial pathway for methane transformation, and plays an important role in determining whether seepage methane can enter the surface ocean. While how the pressure determines the hydrate formation process in different water depths remains unclear. In this study, we investigated the formation kinetic characteristics and microstructure evolution of methane hydrate on suspended gas bubbles within varied pressure conditions. The pressure range (4–14 MPa) was in the deep-sea methane seepage environment. The results indicated that pressure obviously affected the hydrate film formation characteristics. As pressure increased, the lateral growth rate of the hydrate film accelerated, the hydrate crystal particles became smaller, and the initial hydrate film surface became smoother. Raman spectroscopy results showed that pressure changes did not obviously alter the microporous evolution on the hydrate film surface, that the gas-phase/water-phase Raman peak area ratio exhibited similar trends. The dissolved methane concentration under different pressure conditions was not the primary factor affecting hydrate thickening, rather, it depended mainly on the driving force. This study is of great significance in revealing the characteristics of methane hydrate formation and methane transfer in the oceanic methane seepage environment.

Investigation on methane hydrate formation behaviors in deep-sea methane seepage environments

Deep-sea cold seep is a natural phenomenon where methane leaks from the sea floor. Methane can be partially conversed through physical, chemical, and biological processes, but the excess methane that remains uncaptured escapes into the atmosphere and contributes to the greenhouse effect. Physical carbon sequestration via hydrate formation is a fast and high-energy density type of carbon sequestration; however, it has been largely overlooked. This study investigated hydrate formation in authigenic carbonate rocks through deep-sea geological surveys in cold seeps in the South China Sea. Investigations have shown that authigenic carbonate rocks can sequester carbon by blocking the methane plume from the seepage vents. This perspective provides a new physical carbon sequestration mode of carbonate rocks by observing the artificial collection of methane plumes in deep-sea seepage areas. The mode was simplified into two steps including the formation of a thin layer of planar hydrate film on carbonate rocks and a thick layer of hydrate through the stacking of bubbles under the thin film. Salinity, a key distinction between seawater and freshwater, was further investigated for its impact on the carbon sequestration mechanism. Results showed that saline ions in seawater had little impact on the thickening rate of the planar hydrate film but reduced the lateral growth rate of hydrates on the bubble by 60%. This reduction in the lateral growth rate greatly facilitated the three-dimensional growth, increased the hydrate thickness on the bubble, and improved the carbon sequestration efficiency. Hydrate formation on the exposed carbonate rock can effectively impede methane plume migration into upper water and atmosphere, mitigate the greenhouse effect, and present a promising strategy for carbon sequestration in deep-sea methane seepage areas.

Bioaccumulation of Chemical Elements and Organic Carbon in the Macrozoobenthic Organisms of the Laptev Sea

Within the framework of the program “Marine Ecosystems of the Siberian Arctic”, based on the materials collected during the 69th and 72nd cruises of the R/V “Akademik Mstislav Keldysh”, a study of the distribution of a group of chemical elements (As, Ba, Bi, Co, Cr, Cr, Cd, Co, Cu, Cr, Mn, Ni, Pb, Sc, Ti, Tl, Th, V, U and Zn) and organic carbon in the mass taxa of the Laptev Sea macrozoobenthos in the fields of methane seepage and outside them was carried out. For the first time, the bioaccumulation potential (BP) was quantified, taking into account, along with the concentration of elements in organisms, their biomass. At the C-15 methane field, the population of brittle stars accumulates each of the microelements many times (up to 40 times) more than at the background station. Brittle stars and bivalves show increased BP for Ni, As, Ba, Cu, Ti, V, Mn, and Zn compared to other elements, with brittle stars having significantly higher BP. It is assumed that the increased bioaccumulation of some heavy metals and metalloids in methane seep areas is associated with a greater bioavailability of organic matter in bottom sediments. For organic carbon, the highest BP was established, which is especially expressed in the C-15 methane field. At the background station, taxa accumulate a significantly smaller (by a factor of 10) amount of carbon in their biomass. As a result of the functioning of the ground eaters, bottom sediments are enriched with organic carbon, which may indicate an important contribution of benthic organisms to the carbon cycle in the seas of the Arctic.

Natural Structural Transition of Gas Hydrates From sI to sII in the Deep Seafloor

AbstractThe evolution of gas hydrates influenced by the seawater environment is unknown. We present a model of structural transformation from sI hydrate to sII hydrate due to the influence of seawater environment and vent fluid in nature through in situ experiments of gas hydrate formation in the Haima cold seep area. The in situ experimental results indicate that gas hydrates preferentially form as sI hydrates even in cold seep environments where C2+ hydrocarbons are present. During subsequent evolution, the sI hydrates could restructured at the effect of seawater environment and vent fluid, causing transformation to sII hydrates under the influence of hydrate stability. The supply of gas and direct contact with seawater environment are critical factors for structural transformation. Such structural transformation is the result of gas hydrates seeking thermodynamic stability and may be common in active cold seep areas.

Experimental and modeling investigations on CH4 hydrate phase equilibria in multi-ion “Haima” cold seep environment

CH4 hydrate formation represents a primary pathway for CH4 transformation within the deep-sea CH4 seepage environment, holding utmost significance for global carbon budget and marine hydrate resources distribution. As a typical active CH4 seeping, however, the influence characteristics of various ions in in-situ “Haima” cold seep on CH4 hydrate stability remains unclear. In this study, founded on the multiple ion components from the seawater of the “Haima” cold seep, the effects of salt ion categories and concentrations on CH4 hydrate phase equilibrium were investigated, and a thermodynamic model suitable for high-salinity deep-sea environment was proposed. Results indicated that, in higher concentration salt solutions (>3.45 wt%), hydrate stability was no longer solely governed by salinity, and significant differences among ion types were observed. The inhibitory strength of the ions on CH4 hydrate stability followed the order of Mg2+>Na+>Ca2+>Mn2+≈K+>Sr2+>Ba2+. The predicted CH4 hydrate phase equilibrium conditions from the proposed model exhibited strong agreement with both experimental results and data reported in the literature. The average absolute deviation of pressure (AADP) from the model prediction was 2.7% and 4.3% compared to the experimental and published literature data, respectively, which outperformed those of the CSMHYD model, Chen-Guo model and Hu-Lee-Sum correlation (4.7%–6.2%). In light of the marine temperature gradient and prediction results, it is estimated that CH4 hydrate could maintain stably below 600 m depth of the seawater in the cold seep area.

Contrasting Methane Seepage Dynamics in the Hola Trough Offshore Norway: Insights From Two Different Summers

AbstractThis study investigates the temporal variations in methane concentration and flare activity in the Hola trough (offshore Norway) during May 2018 and June 2022. Between these time periods, methane seep activity exhibits 3.5 times increase, as evidenced by hydroacoustic measurements. As the seep area in the Hola trough is constantly within the hydrate stability zone, the observed increase cannot be attributed to migration of its shallow boundary due to temperature increase. However, a combination of low tide conditions resulting in a lower sediment pore pressure and a bottom water temperature increase resulting in a lower methane solubility is likely to explain the increase in the number of seeps observed in June 2022. The hypothesis of tide influence is supported by data collected from a piezometer deployed and recovered during the cruise showing that the tidal effect was observed 3 m below the seafloor. Despite the numerous methane seeps detected, methane concentration and gas flow rates near the seafloor were low (<19 nM and <70 mL min−1, respectively) compared to other areas with methane seep activity. This is likely due to strong currents rapidly dispersing methane in the water column. Sub‐seafloor investigations identified pathways for gas migration in methane seep areas, influenced by topography. This study provides valuable insights into the temporal dynamics of methane concentrations, flare activity, and gas distribution in the Hola trough, contributing to our understanding of offshore methane dynamics in the region.

Occurrence of microplastics in the Haima cold seep area of the South China Sea

The pollution of deep-sea microplastics has received increasing attention. As a special ecosystem in the deep sea, the cold seep area is of great significance for studying the distribution of microplastics in the deep sea. In this work, the distribution and characteristics of microplastics in seawater, sediments, and shellfish in the Haima cold seep area and the correlation between the characteristics of microplastics in different media and the type of media were studied. Microplastics were found in all three media. The abundance of microplastics in different samples from the Haima cold seep area ranged 1.8–3.8 items/L for the seawater, 11.47–96.8 items/kg (d.w.) for the surface sediments, and 0–5 items/individual (0–0.714 items/g) for the shellfish. The amount of microplastics ingested by shellfish varied among different species. The microplastics in these three media were mainly fibrous, dark-colored, small-sized rayon, polyethylene terephthalate (PET), and polyethylene (PE). In the correlation analysis of microplastic characteristics among the three media, it was found that the characteristics of microplastics in different media in the same area were closely related, and each pair of variables showed a significant positive correlation (P ≤ 0.05). The distinctive geographical conditions would accelerate the interchange of microplastics among various media. Principal component analysis showed that habitat contribute to microplastic feature differences in shellfish. Differences in correlation were observed between the characteristics of shellfish microplastics in different regions and the characteristics of microplastics in surrounding seawater and sediments.

A vast repertoire of secondary metabolites potentially influences community dynamics and biogeochemical processes in cold seeps.

In deep-sea cold seeps, microbial communities thrive on the geological seepage of hydrocarbons and inorganic compounds, differing from photosynthetically driven ecosystems. However, their biosynthetic capabilities remain largely unexplored. Here, we analyzed 81 metagenomes, 33 metatranscriptomes, and 7 metabolomes derived from nine different cold seep areas to investigate their secondary metabolites. Cold seep microbiomes encode diverse and abundant biosynthetic gene clusters (BGCs). Most BGCs are affiliated with understudied bacteria and archaea, including key mediators of methane and sulfur cycling. The BGCs encode diverse antimicrobial compounds that potentially shape community dynamics and various metabolites predicted to influence biogeochemical cycling. BGCs from key players are widely distributed and highly expressed, with their abundance and expression levels varying with sediment depth. Sediment metabolomics reveals unique natural products, highlighting uncharted chemical potential and confirming BGC activity in these sediments. Overall, these results demonstrate that cold seep sediments serve as a reservoir of hidden natural products and sheds light on microbial adaptation in chemosynthetically driven ecosystems.

Real-time tunnel lining leakage image semantic segmentation via multiple attention mechanisms

One of the key objectives in tunnel illness detection is identifying tunnel lining leakage, and deep learning-based image semantic segmentation approaches can automatically locate tunnel lining leakage. However, in order to meet the real-time processing needs of professional mobile inspection equipment, existing leakage image segmentation approaches have difficulties in identifying real-time, dealing with voids, and dealing with edge discontinuities in the leaking zone. To address the aforementioned issues, this study introduces the PP-LiteSeg-Attn model, which takes the real-time semantic segmentation model PP-LiteSeg-B as baseline model, and combines the multi-layer CBAM attention mechanism and the CoT attention mechanism. Using the publically available dataset Water-Leakage, we trained and validated the PP-LiteSeg-Attn model, and attained IoU and F1 values of 88.18% and 93.72%, respectively, outperforming similar models in both measures. Extensive experiments show that the segmentation speed of the PP-LiteSeg-Attn model reaches 112.28 FPS, which meets real-time requirements, and that the model can effectively solve problems such as the appearance of voids in the seepage area, discontinuity, and fuzzy segmentation of seepage edges. The PP-LiteSeg-Attn model is better applicable to complicated tunnel settings, offering technical references for real-time diagnosis of tunnel illnesses.

Analysis of Groundwater Salinity Levels in the Lampulo Coastal Area Kuta Alam Sub-District

The problem of seawater seepage in coastal areas can result in a decrease in groundwater quality due to the mixing of seawater and groundwater, so seawater seepage has an impact on increasing salinity, including in the research area. The research location is in the Lampulo beach area, Kuta Alam sub-district. Phreatic well water is generally not liked by residents of this coastal area because it tastes brackish. The high salinity of phreatic groundwater is caused by seawater seepage into alluvial land. The aim of this research is to analyze the level of groundwater salinity in the Lampulo coastal area, Kuta Alam sub-district. This research uses a grid sampling method and criteria for assessing groundwater salinity (o/oo) based on salt content. Groundwater salinity was measured randomly in 50 phreatic wells using a refractometer and marked with sample coordinates using the Avenza Maps application. Field measurement results show that there are variations in salinity values ranging from 0 to 32 ppt. Phreatic well water at the research location based on its salt content is grouped into three groups, namely fresh water, brackish water and salt water. For the freshwater group, a percentage value was obtained with a prevalence of 68%; for the brackish water group, a percentage value was obtained with a prevalence of 26%; and for the salt water group, a percentage value was obtained with a prevalence of 6%.Keywords: Salinity, Groundwater, Phreatic Well, Seawater Seepage, Grid SamplingÂ

Adaptive AUV Mission Control System Tested in the Waters of Baffin Bay

The primary objectives of this paper are to test an adaptive sampling method for an autonomous underwater vehicle, specifically tailored to track a hydrocarbon plume in the water column. An overview of the simulation of the developed applications within the autonomous system is presented together with the subsequent validation achieved through field trials in an area of natural oil seeps near to Scott Inlet in Baffin Bay. This builds upon our prior published work in methodological development. The method employed involves an integrated backseat drive of the AUV, which processes in situ sensor data in real time, assesses mission status, and determines the next task. The core of the developed system comprises three modular components—Search, Survey, and Sample—each designed for independent and sequential execution. Results from tests in Baffin Bay demonstrate that the backseat drive operating system successfully accomplished mission goals, recovering water samples at depths of 20 m, 50 m, and 200 m before mission completion and vehicle retrieval. The principal conclusion drawn from these trials underscores the system’s resilience in enhanced decision autonomy and validates its applicability to marine pollutant assessment and mitigation.

Identification and Characteristics Analysis of Micro-Seismic Signals in the Haima Seep Area

Identification and Characteristics Analysis of Micro-Seismic Signals in the Haima Seep Area

Manifestation of Gas Seepage from Bottom Sediments on the Sea Surface: Theoretical Model and Experimental Observations

The key area of the Arctic Ocean for atmospheric venting of CH4 is the East Siberian Arctic Shelf (ESAS). Leakage of methane through shallow ESAS waters needs to be considered in interactions between the biogeosphere and a warming Arctic climate. The development of remote sensing techniques for gas seepage detection and mapping is crucially needed for further applications in the ESAS and other areas of interest. Given the extent of the seepage areas and the magnitude of current and potential future emissions, new approaches are required to effectively, rapidly, and quantitatively survey the large seepage areas. Here, we consider the main features of gas seep detection on the sea surface in the characteristics of wind waves and radar signals. The kinematics of wave packets based on the kinetic equation for the spectral density of the wave action of surface waves is described. The results of a full-scale experiment on the remote radar observation of a model gas seep to the sea surface in the radar equipment signals are considered. The characteristic radar signatures of the gas seep in a wide range of hydrometeorological conditions, the parameters of which were recorded synchronously with the radar mapping, were determined. The results of the first radar observations of natural methane seeps on the ESAS are presented, and their radar contrasts are evaluated. The theoretical conclusions are in good qualitative agreement with the results of the model experiment and field studies and can be used for further research in aquatic areas with potential gas seepage, both of natural or anthropogenic origin, such as bubbling release from broken underwater gas pipelines.

Source and significance of Cretaceous oil seepage in the northern Ordos Basin, China

It has long been believed that the region on the north of the Dongsheng gas field has only limited exploration potential due to the lack of effective source rocks. However, several areas of Cretaceous oil seepage have been discovered in the area and their sources are unclear. In this study, the organic geochemical characteristics of these oil seepages and potential source rocks (coals and carbonaceous mudstones of different formations) are examined using TOC analysis, pyrolysis, gas chromatography-mass spectrometry, and carbon isotopes. The results show that the oil seepages are low-to-moderately mature (0.63 %-0.78 % Rc) and slightly biodegraded. The molecular biomarker compositions of the oil seepages are characterized by C29≫C28>C27 normalized relative abundance of regular steranes, high values of Pr/Ph, (C19TT + C20TT)/C23TT and C24TeT/C26TT ratios, low values of Ga/C30H, and low abundance of dibenzothiophenes. The biomarker compositions, as well as the stable carbon isotopes, indicate that the source of the oil seepages was deposited in a lacustrine fluvial/deltaic environment under oxic to sub-oxic conditions, with organic matter input predominantly from terrigenous higher plants. Oil-source correlation revealed that the oil seepages were closely related to the coals in the Shanxi formation in the south source kitchen, implying that the hydrocarbons generated in the south source kitchen have been able to migrate to the north edge of the Ordos Basin. The oil seepages are accompanied by significant gas leakage. The zone between the Dongsheng gas field and the Wulangar Uplift is therefore likely to have very good accumulation and preservation conditions and may offer a promising exploration prospect for natural gas.

Analysis of Fracture Surface Morphology and Study of Seepage Diffusion Characteristics

There are a large number of rough and irregular fractures in underground engineering rock mass, which makes the movement of fracture fluid very complex. To address the issues of non-visibility of physical model tests and non-repeatability of joint surfaces in natural rock fractures, a method was proposed to accurately depict the impact of rough fracture morphology on rock seepage. This method involved using natural rock fractures as a prototype and creating secondary molds using gypsum and silica gel to precisely replicate the rough fracture surface morphology. The three-dimensional morphology scanning technology was used to accurately obtain the surface morphology information of rough fractures, and the anisotropy of rough fracture morphology parameters was analyzed. Additionally, the study investigated the characteristics of seepage area and frontal flow line morphology through the use of a visual transparent fracture model. The obtained results provided an intuitive understanding of the distribution law of the seepage field. The evolution law of flow velocity with roughness was analyzed by layer superposition technique. The point of maximum flow velocity corresponded to the point of abrupt change in elevation, which occurred in the region with the greatest fluctuation height of the fracture surface. The accurate description of flow patterns in various rough fractures offers theoretical guidance for seepage in rock fractures in practical engineering applications.

Stability analysis and grouting treatment of inclined shaft lining structure in water-rich strata: A case study

The stability of inclined shaft lining structure (ISLS) in complex water-rich strata is affected by many factors, such as water pressure, joint, soft rock, lining corrosion and so on. The instability of the ISLS will affect the safe and efficient coal mine production. Bathe sed on the geological conditions of the Xiaobaodang coal mine, this paper tested the evolution characteristics of concrete composition in long-term water seepage areas and revealed the influence mechanism of corrosion weakening of shaft lining (SL) in water-rich strata. Meanwhile, transient electromagnetic, ground penetrating radar, and infrared monitoring are used to detect the water-rich zones, and damage zones of surrounding rock and lining water seepage zones, and a three-level safety evaluation model for the instability risk of ISLS is constructed. Water abundance of the surrounding rock, surrounding rock deterioration, and shaft lining seepage were the specific indicators in the model. The main inclined shaft (MIS) in the studied coal mine is divided into three levels: non instability risk zone, potential instability risk zone, and high instability risk zone. According to the evaluation results, comprehensive prevention and control measures of “hydrophobic hole drainage” and “back-lining grouting” are adopted for the water inrush source and the surrounding rock micro-crack water channel. The precise prevention and control of ISLS is realized. The research results also provide a reference for the stability evaluation of ISLS and the accurate prevention and control under similar conditions.