Cold Seeps Research Articles

Validation of a New Method for Continuous Flare Combustion Efficiency Monitoring

A new method is described for calculating flare combustion efficiency (CE) and destruction and removal efficiency (DRE) using a numerical parametric model. The method combines key variables that affect flare performance including the flare vent gas net heating value (NHV), flare design, flow rate, exit velocity, and inert gas composition, alongside the environmental influence of crosswind speed. Each effect is characterized using a parametric model derived from experimental testing data and computational fluid dynamics (CFD). The inclusion of CFD allows the model to be extended into the high-wind conditions that cannot be adequately controlled for in empirical testing yet represent some of the most challenging conditions in which to maintain good combustion. This new parametric model method (PMM) is coupled with ultrasonic flowmeters from which the molecular weight and net heating value of the flare gas can be derived using the vent gas speed of sound measurement. In doing so, this method provides a reliable continuous flare combustion efficiency measure that can be deployed at scale with minimum hardware updates. The system was verified using an extractive sampling method with tests conducted on three full-scale industrial flares including non-assisted, single-arm pressure-assisted, and multi-arm pressure-assisted flare designs. A total of seventy valid test points were carried out with varying flow rate and flare gas heating value, covering a CE range from 46–100%. The uncertainty of the method was assessed using both traditional error propagation and Monte Carlo methodology. The results from the new method agree with the extractive method to within 0.8% in the ≥98% DRE region where flares are expected to operate to limit the impacts of flaring as a source of methane as a greenhouse gas. Uncertainty analysis revealed that the larger DRE discrepancy for DRE ≤ 98% correlates to the measurement uncertainties for both methods.

Integrating 3D subsurface imaging, seismic attributes, and wireline logging analyses: Implications for a high resolution detection of deep-rooted gas escape features, eastern offshore Nile Delta, Egypt

The eastern part of the offshore Nile Delta is one of Egypt's most productive gas provinces. This study utilizes well logs dataset and 2D seismic from Port Fouad marine (PFM) Field to investigate reservoir lithofacies, rock-types as well as the associated gas chimneys, pockmarks, bright anomalies of escaping fluids in the seafloor, and high-faulted zones caused by the chimney's developments. First, structural smoothing and median filters are used to improve the continuity of the stratigraphic horizons while preserving various geological structures, in order to pick all formation tops and structural faults. Afterwards, variance and energy attributes were computed and extracted for amplitude enhancement of various geobodies such as faults, gas chimneys, and bright reflectors. After that, petrophysical analyses revealed that the Upper Miocene Wakar Formation hosts scattered, thin gas pay zones (<10m) with low hydrocarbon saturation values (average Shc = 27.9%), high water saturation (average Sw > 70%), and high shale volume (average Vsh > 30%). These poor reservoir characteristics prevented accumulation of thick gas zones, thereby several gas escape features (e. vertical chimneys) are observed in the region. Finally, the estimated petrophysical parameter logs and the structure maps derived from seismic data are crucial components of the built 3D structural model. This model reveals the presence of four major normal faults (F1, F2, F3, and F4) oriented NW-SE and WNW-ESE, creating grabens and half grabens. These major faults (F1, F2, F3, and F4) are directly related to the inverted tectonics during the Cretaceous-Paleogene compression (Syrian Arc phase). A link between these structural patterns and gas escape zones is proposed, and the absence of good reservoir facies likely promoted an active phase of gas seepage in the study region. In addition, such gas escape chimneys can create catastrophic events on the seafloor and are considered direct evidence for the presence of gas generation and failure in accumulation.

Cold seep formation from salt diapir–controlled deep biosphere oases

Deep sea cold seeps are sites where hydrogen sulfide, methane, and other hydrocarbon-rich fluids vent from the ocean floor. They are an important component of Earth's carbon cycle in which subsurface hydrocarbons form the energy source for highly diverse benthic micro- and macro-fauna in what is otherwise vast and spartan sea scape. Passive continental margin cold seeps are typically attributed to the migration of hydrocarbons generated from deeply buried source rocks. Many of these seeps occur over salt tectonic provinces, where the movement of salt generates complex fault systems that can enable fluid migration or create seals and traps associated with reservoir formation. The elevated advective heat transport of the salt also produces a chimney effect directly over these structures. Here, we provide geophysical and geochemical evidence that the salt chimney effect in conjunction with diapiric faulting drives a subsurface groundwater circulation system that brings dissolved inorganic carbon, nutrient-rich deep basinal fluids, and potentially overlying seawater onto the crests of deeply buried salt diapirs. The mobilized fluids fuel methanogenic archaea locally enhancing the deep biosphere. The resulting elevated biogenic methane production, alongside the upward heat-driven fluid transport, represents a previously unrecognized mechanism of cold seep formation and regulation.

Laminar burning velocity of lithium-ion battery thermal runaway vent gas in air

In this study, a spherically propagating flame of vent gas generated during the thermal runaway of lithium-ion batteries with different states of charge (SOC) was experimentally and numerically investigated. The vent gas is mainly composed of H2, CO, CO2, and some hydrocarbons. With increasing SOC, the CO2 fraction tends to decrease while the H2 and CO fractions tend to increase. Combustion experiments were conducted using a closed vessel, and the combustion progression was captured using a high-speed Schlieren image system to measure the unstretched laminar burning velocity, Su0. In addition, the combustion was computationally estimated under the experimental conditions by performing 1D planar flame simulations using Chemkin-Pro with the Aramco Mech 1.3 reaction model. Remarkably, the calculated values of Su0 closely matched the experimental ones, demonstrating good agreement. The results showed that Su0 tended to increase with increasing SOC. Furthermore, the effects of the chemical reaction mechanism, which plays a pivotal role in driving this increase in Su0 with increasing SOC, were investigated. Specifically, the heightened SOC levels promoted the H2 branching reaction led to an increased concentration of OH radicals in the mixture. This consequently accelerated the rate-determining reaction for the oxidation of hydrocarbons, leading to an increase in Su0. As an effect of the hydrocarbons in the vent gas mixtures, the number of moles of CO increased slightly near the flame because the rate of CO production in the flame zone was more dominant than that of consumption under the condition of SOC 50.

Mitochondrial and morphological adaptions of Lindaspio polybranchiata (Annelida: Spionidae) in the South China Sea

A dense population of Lindaspio polybranchiata (Annelida: Spionidae) was discovered in a novel cold seep with drastic methane seepage located on the northern passive continental margin of the South China Sea. L. polybranchiata may function as a pioneer species by rapidly colonizing this nascent methane seep. We studied its classification status and evolutionary selection adaptation based on the mitochondrial genome. Phylogenetic analysis revealed that the deep-sea genus Lindaspio clustered with the neritic Rhynchospio aff. asiatica, and the ancestor of the deep-sea Lindaspio might originate from shallow-water spionids. Twelve potentially adaptive mutations were identified in cox1, cox3, cytb, and nad5. The morphological characteristics of L. polybranchiata and R. aff. asiatica collected in the intertidal zones were systematically compared to explore the possible phenotypic adaptations of L. polybranchiata to extreme deep-sea environments. L. polybranchiata lost its eyespots due to long-term colonization of the dark habitat in the deep sea but developed an enlarged caruncle for facilitating chemical perception in the darkness. The specific ventral branchiae and extended respiratory surfaces may aid the survival of L. polybranchiata in the hypoxic environment of the cold seep. This study provides novel insights into the molecular and morphological adaptations of a species endemic in chemosynthetic ecosystems.

Soil processes modify the composition of volatile organic compounds (VOCs) from CO2- and CH4-dominated geogenic and landfill gases: A comprehensive study

Degradation mechanisms affecting non-methane volatile organic compounds (VOCs) during gas uprising from different hypogenic sources to the surface were investigated through extensive sampling surveys in areas encompassing a high enthalpy hydrothermal system associated with active volcanism, a CH4-rich sedimentary basin and a municipal waste landfill. For a comprehensive framework, published data from medium-to-high enthalpy hydrothermal systems were also included. The investigated systems were characterised by peculiar VOC suites that reflected the conditions of the genetic environments in which temperature, contents of organic matter, and gas fugacity had a major role. Differences in VOC patterns between source (gas vents and landfill gas) and soil gases indicated VOC transformations in soil. Processes acting in soil preferentially degraded high-molecular weight alkanes with respect to the low-molecular weight ones. Alkenes and cyclics roughly behaved like alkanes. Thiophenes were degraded to a larger extent with respect to alkylated benzenes, which were more reactive than benzene. Furan appeared less degraded than its alkylated homologues. Dimethylsulfoxide was generally favoured with respect to dimethylsulfide. Limonene and camphene were relatively unstable under aerobic conditions, while α-pinene was recalcitrant. O-bearing organic compounds (i.e., aldehydes, esters, ketones, alcohols, organic acids and phenol) acted as intermediate products of the ongoing VOC degradations in soil. No evidence for the degradation of halogenated compounds and benzothiazole was observed. This study pointed out how soil degradation processes reduce hypogenic VOC emissions and the important role played by physicochemical and biological parameters on the effective VOC attenuation capacity of the soil.

Temporal Variation and Persistence of Methane Emissions from Shallow Water Oil and Gas Production in the Gulf of Mexico.

Methane emissions from the oil and gas supply chain can be intermittent, posing challenges for monitoring and mitigation efforts. This study examines shallow water facilities in the US Gulf of Mexico with repeat atmospheric observations to evaluate temporal variation in site-specific methane emissions. We combine new and previous observations to develop a longitudinal study, spanning from days to months to almost five years, evaluating the emissions behavior of sites over time. We also define and determine the chance of subsequent detection (CSD): the likelihood that an emitting site will be observed emitting again. The average emitting central hub in the Gulf has a 74% CSD at any time interval. Eight facilities contribute 50% of total emissions and are over 80% persistent with a 96% CSD above 100 kg/h and 46% persistent with a 42% CSD above 1000 kg/h, indicating that large emissions are persistent at certain sites. Forward-looking infrared (FLIR) footage shows many of these sites exhibiting cold venting. This suggests that for offshore, a low sampling frequency over large spatial coverage can capture typical site emissions behavior and identify targets for mitigation. We further demonstrate the preliminary use of space-based observations to monitor offshore emissions over time.

Copper and zinc isotopic compositions of methane-derived carbonates: Implications for paleo-methane seepage and paleoenvironmental proxies

Copper and zinc isotopic compositions of methane-derived carbonates: Implications for paleo-methane seepage and paleoenvironmental proxies

Lateral migration of methane at a cold seep: Evidence from U–Th dating of methane-derived authigenic carbonate in the Middle Okinawa Trough

Submarine methane seepages constitute an important part of global carbon cycle and may be promoted by the dissociation of gas hydrate. The migration pattern of a seepage is commonly dominated by vertical transport of methane-rich pore fluids, and then lateral migration of these fluids probably occurred due to self-sealing effect of carbonate crust above vertical migration conduit. Some studies found the evidence of this lateral migration, but the one from the record of seep carbonate in nature is very rare. In this study, we present the results of mineralogical, isotopic, and dating analyses of a core containing seep carbonates obtained from seafloor drilling site D5 in the Middle Okinawa Trough. The core contains 0.98-m-long carbonate interval that predominantly consists of aragonite, with an average content of ∼86.6%. The carbonate exhibits moderate depletion in 13C (δ13C values: −37.2‰ to −16.3‰ Vienna Pee Dee Belemnite; VPDB) and enrichment in 18O (δ18O values: 4.3‰–5.8‰ VPDB), with relatively constant 87Sr/86Sr values (0.709167–0.709197). These results suggest that the precipitation of the seep carbonate was induced by the sulfate-driven anaerobic oxidation of methane close to the seabed and this methane could be from the dissociation of gas hydrates. U–Th age–depth profile shows that two carbonate intervals grew downwards coevally to coalesce into a thicker crust, and its upper segment also grew upwards. We interpret that lateral migration of the fluid flows at two levels are responsible for the formation of upper and lower segments of carbonate intervals because they have (a) the distinct clustering of δ13C and δ18O values and (b) a coeval period of fast growth. It is likely that upward migration of methane was redirected by self-sealing of overlying carbonate crust, leading to lateral migration at the flank of seabed mound Db4 during 6.2–4.6 ka. Our findings highlight the interaction between fluid flows and authigenic carbonates during Late Quaternary, which implies that more methane could be consumed by oxidation because it takes longer time for methane to bypass self-sealing of carbonate to escape into the ocean.

Effects of pockmark activity on iron cycling and mineral composition in continental shelf sediments (southern Baltic Sea)

AbstractPockmarks are formed as a result of gas (methane) or/and groundwater outflow from the sea bottom. Methane, the second most important (after CO2) greenhouse gas, has a significant impact on biogeochemical processes in the bottom sediments by affecting the cycling of some elements, e.g. C, Fe, and S. Active pockmarks may also lead to changes in water column conditions by causing nutrients release from sediments. In the present study, we have focused on the impact of biogeochemical processes in pockmarks (methanogenesis, anaerobic methane oxidation, and groundwater seepage) on the transformation of iron (Fe) and the mineral composition of the sediment. In pore water, concentrations of hydrogen sulfide, phosphate, ammonia, sulfate, chloride, dissolved inorganic carbon, iron, and methane were analyzed. In the sediment, Fe speciation was performed using sequential extraction. The mineral composition was determined using powder X-Ray diffraction and scanning electron microscopy. The results from two pockmarks (with active gas seepage and groundwater infiltration) and two reference stations in the southern Baltic Sea show that geochemical conditions in pockmark sediments are significantly different from those in the typical muddy sea bottom. Pore water in pockmarks is characterized by lower sulfate and higher dissolved carbon concentrations as compared to areas of the seafloor where such structures are absent. This is due to the outflow of groundwater, which was confirmed by lower chloride concentration. In addition, sulfate is used to oxidize methane diffusing from deeper layers. Sediments in pockmarks are enriched in Fe(II) carbonates and depleted in Fe(III) (oxy)hydroxides, resulting from the anaerobic oxidation of methane with Fe(III) (Fe-AOM). Ferrous iron produced in large quantities during Fe-AOM is precipitated with carbonates.

Protracted post-glacial hydrocarbon seepage in the Barents Sea revealed by U–Th dating of seep carbonates

The hydrocarbon seepage chronology during deglaciation across the formerly glaciated Barents Sea was established using uranium-thorium (U–Th) dating of seep carbonates. Seep carbonates were sampled with remotely operated vehicles (ROV) from the seafloor at three active hydrocarbon seeps (water depth 156–383 m), located in the north-west (Storfjordrenna), north-central (Storbanken High), and south-west (Loppa High) Barents Sea. Overall, the U–Th dates range from 13.5 to 1.2 thousand years (ka) before present, indicating episodic seep carbonate formation since the late Pleistocene throughout the Holocene. The new U–Th dates indicate protracted post-glacial gas seepage, congruent with previously published seep carbonate ages from the south-west Barents Sea. Gas hydrate dissociation and associated seep carbonate formation occurred at Storfjordrenna between ≈6 and 1.2 ka, and around 13.5 and 6 ka at Storbanken. Early and late Holocene seep carbonate ages from Loppa High support post-glacial seismic activity as potential seepage trigger mechanism.

Interdisciplinary approaches to modeling extraction efficiency and safety for clean energy under coupled multi-field effects

Coal bed methane, a crucial clean energy source, has attracted extensive research attention. Characterized by intricate and rough fracture systems, coal seam is vital for gas migration, which will be influenced by the in situ stress, coal temperature, adsorption–desorption effect, solid deformation, and gas pressure. This paper introduces an innovative, interdisciplinary fractal model that addresses the limitations of current computational models in accurately representing the complex fractures under the coupled multi-field effects. Four novel fractal micro-parameters are introduced to capture the dynamics of rough networks. And rigorous validation against field extraction data reveals that the proposed micro-parameters outperform existing methods in analytical efficacy. Notably, those micro-parameters significantly influence fracture behavior and gas seepage. For instance, a DT increase from 1.2 to 1.8 and an ε rise from 0.06 to 0.18 lead to a respective 29.8% and 22.7% increase in gas pressure. Moreover, alterations in these fractal micro-parameters under coupled multi-field effects markedly impact coal bed stress, raising safety concerns in engineering projects, with a potential increase in coal stress by up to 2.62%. This research offers innovative insights into the complex coupled mechanisms governing rough fractures and significantly advances the understanding of the efficiency and safety in clean energy extraction processes.

Air Quality and Health Impacts of Onshore Oil and Gas Flaring and Venting Activities Estimated Using Refined Satellite-Based Emissions.

Emissions from flaring and venting (FV) in oil and gas (O&G) production are difficult to quantify due to their intermittent activities and lack of adequate monitoring and reporting. Given their potentially significant contribution to total emissions from the O&G sector in the United States, we estimate emissions from FV using Visible Infrared Imaging Radiometer Suite satellite observations and state/local reported data on flared gas volume. These refined estimates are higher than those reported in the National Emission Inventory: by up to 15 times for fine particulate matter (PM2.5), two times for sulfur dioxides, and 22% higher for nitrogen oxides (NOx). Annual average contributions of FV to ozone (O3), NO2, and PM2.5 in the conterminous U.S. (CONUS) are less than 0.15%, but significant contributions of up to 60% are found in O&G fields with FV. FV contributions are higher in winter than in summer months for O3 and PM2.5; an inverse behavior is found for NO2. Nitrate aerosol contributions to PM2.5 are highest in the Denver basin whereas in the Permian and Bakken basins, sulfate and elemental carbon aerosols are the major contributors. Over four simulated months in 2016 for the entire CONUS, FV contributes 210 additional instances of exceedances to the daily maximum 8-hr average O3 and has negligible contributions to exceedance of NO2 and PM2.5, given the current form of the national ambient air quality standards. FV emissions are found to cause over $7.4 billion in health damages, 710 premature deaths, and 73,000 asthma exacerbations among children annually.

Coupling of organic carbon and nitrogen isotopes in cold seep carbonates and its implication for the anaerobic oxidation process of methane

Coupling of organic carbon and nitrogen isotopes in cold seep carbonates and its implication for the anaerobic oxidation process of methane

Experimental study on gas slippage effect in coal at different temperatures based on nuclear magnetic resonance

Coalbed methane (CBM) can be recovered more effectively through heat injection mining. The slippage effect in coal becomes more significant as CBM is exploited, essential for maintaining consistent production of CBM wells. By “slippage effect,” we mean that gas molecules exhibiting non–zero velocity near the wall surface of coal pores, leading to higher gas permeability than liquid permeability. To explore the slippage effect and its control mechanism during heat injection mining, methane seepage experiments with constant effective stress were conducted under five different temperatures and seven pore pressures. An analysis was conducted on the mechanisms by which pore pressure and temperature affect gas slippage effect. Furthermore, the correlation between coal pore structure and the gas slippage effect was revealed using the nuclear magnetic resonance (NMR) technique. The results appear that, first, as pore pressure increases, the slippage effect is suppressed due to the influence of the average molecular free path, despite the positive impact of adsorption–induced matrix expansion. Second, as temperature rises, the average molecular free path and thermal expansion have a positive impact on gas slippage, while matrix shrinkage caused by desorption has a negative impact. The positive impact is stronger, resulting in a continuous enhancement of the slippage effect. Finally, a new slippage factor calculation based on NMR T2 distribution of micropores and transitional pores (&amp;lt;100 nm, T2 &amp;lt; 8.33 ms) was provided, and the method was verified by slippage factor fitted by permeability experimental data. The heat injection mining of CBM can be theoretically guided by the research results.

Experimental Study of the Effect of Molecular Collision Frequency and Adsorption Capacity on Gas Seepage Flux in Coal

Summary The differences in the transport behavior and adsorption capacity of different gases in coal play crucial roles in the evolution of coal permeability. Previous studies of coreflooding experiments failed to explain the mechanism of gas flow and have attributed the variation in gas seepage flux (flow rate) at the beginning of the experiment to the change in effective stress, while the differences in the microscopic properties of different gases, such as molar mass, molecular diameter, mean molecular free path, and molecular collision frequency, were ignored. To research the effect of these gas properties on seepage flux while circumventing the effective stress, coreflooding experiments with helium (He), argon (Ar), nitrogen (N2), methane (CH4), and carbon dioxide (CO2) were designed. The results show that the gas transport velocity in coal is affected by the combination of molecular collision frequency and dynamic viscosity, and the transport velocities follow the order of ν (CH4) &amp;gt; ν (He) &amp;gt; ν (N2) &amp;gt; ν (CO2) &amp;gt; ν (Ar). A permeability equation corrected by the molecular collision frequency is proposed to eliminate differences in the permeabilities measured with different gases. The adsorption of different gases on the coal matrix causes different degrees of swelling, and the adsorption-induced swelling strains follow the order of ε (CO2) &amp;gt; ε (CH4) &amp;gt; ε (N2) &amp;gt; ε (Ar) &amp;gt; ε (He). The reduction in seepage flux and irreversible alterations in pore structure caused by adsorption-induced swelling are positively correlated with their adsorption capacities. The gas seepage fluxes after adsorption equilibrium of coal follow the order of Q (He) &amp;gt; Q (CH4) &amp;gt;Q (N2) &amp;gt; Q (Ar) &amp;gt; Q (CO2). Like supercritical CO2 (ScCO2), conventional CO2 can also dissolve the organic matter in coal. The organic molecules close to the walls of the cleats along the direction of gas flow are preferentially dissolved by CO2, and the gas seepage flux increases when the dissolution effect on the cleat width is greater than that on adsorption swelling.

Optimizing unconventional gas extraction: The role of fracture roughness

In unconventional reservoir engineering, such as coalbed methane and shale gas extraction, fracture behavior is pivotal in gas accumulation, migration, and extraction, acting as a primary channel for gas flow. Current research inadequately addresses the quantitative impact of fracture roughness on gas extraction. In this study, we introduce a novel interdisciplinary model that quantitatively characterizes shale fracture roughness and correlates it with shale permeability. This model comprehensively considers factors affecting shale extraction, including fracture roughness, in situ stress, reservoir deformation, and adsorption-desorption dynamics. It provides a thorough analysis of how fracture roughness influences gas seepage, extraction efficiency, and reservoir stability under various physical conditions. Our validated findings reveal that fracture roughness significantly affects shale permeability, stress responses, and displacement. As the fracture roughness coefficient χ increases from 0.2 to 1.0, the maximum reduction in gas pressure within the hydraulically fractured region is 4.7%, while the maximum increase in reservoir stress is 2.8%. In shale reservoirs near extraction well, particularly in hydraulically fractured zones, the maximum decrease in shale gas pressure is 11.1%, and the maximum increase in stress is 3.2%, which offer a groundbreaking approach for optimizing extraction rates and ensuring project safety in the industry.

New Phenol Derivatives from the Haima Cold Seep-Derived Fungus Aspergillus subversicolor CYH-17.

Seven new phenol derivatives, subversins A-E (1-5), subversic acid A (6) and epi-wortmannine G (7); one new natural product, 4-hydroxy-7-methoxyphthalide (8); and five known compounds (9-13) were isolated from the fungus Aspergillus subversicolor CYH-17 collected from the Haima cold seep. The structures and absolute configurations of these compounds were determined via NMR, MS, optical rotation, electronic circular dichroism (ECD) calculation, X-ray diffraction analysis and comparison with the literature. Compounds 2 and 5 were two pairs of enantiomers. All compounds were tested for their α-glucosidase and acetylcholinesterase (AChE) inhibitory activity, antioxidant activity and antibacterial activity, but no obvious activity was observed among these studied compounds.

Pseudallenes A and B, new sulfur-containing ovalicin sesquiterpenoid derivatives with antimicrobial activity from the deep-sea cold seep sediment-derived fungus Pseudallescheria boydii CS-793.

Pseudallenes A and B (1 and 2), the new and rare examples of sulfur-containing ovalicin derivatives, along with three known analogues 3-5, were isolated and identified from the culture extract of Pseudallescheria boydii CS-793, a fungus obtained from the deep-sea cold seep sediments. Their structures were established by detailed interpretation of NMR spectroscopic and mass spectrometric data. X-ray crystallographic analysis confirmed and established the structures and absolute configurations of compounds 1-3, thus providing the first characterized crystal structure of an ovalicin-type sesquiterpenoid. In the antimicrobial assays, compounds 1-3 showed broad-spectrum inhibitory activities against several plant pathogens with MIC values ranging from 2 to 16 μg/mL.

Deep-sea in situ and laboratory multi-omics provide insights into the sulfur assimilation of a deep-sea Chloroflexota bacterium.

The cycling of sulfur is one of Earth's major biogeochemical processes and is closely related to the energy metabolism of microorganisms living in the deep-sea cold seep and hydrothermal vents. To date, some of the members of Chloroflexota are proposed to play a previously unrecognized role in sulfur cycling. However, the sulfur metabolic characteristics of deep-sea Chloroflexota bacteria have never been reported, and remain to be verified in cultured deep-sea representatives. Here, we show that the deep-sea Chloroflexota bacterium ZRK33 can perform sulfate assimilation in both laboratory and deep-sea conditions, which expands our knowledge of the sulfur metabolic potential of deep-sea Chloroflexota bacteria. We also show that the genes associated with assimilatory and dissimilatory sulfate reduction ubiquitously distribute in the deep-sea Chloroflexota members, providing hints to the roles of Chloroflexota bacteria in deep-sea sulfur biogeochemical cycling.