Deposition Of Elemental Sulfur Research Articles

Optimization of fracturing parameters for horizontal wells in high-sulfur gas reservoirs considering the effect of sulfur deposition

During the development of high-sulfur gas reservoirs, the precipitation and deposition of elemental sulfur can lead to a reduction in reservoir porosity and permeability. Previous studies focus on the well production with optimized operational parameters, but the effect of sulfur deposition is not included, which impacts fracturing parameters, well production, and economic evaluation. Therefore, this work proposes a reasonable approach for parameter optimization considering sulfur. The variation of porosity and permeability are first evaluated during sulfur deposition. After that, fracture half-length, fracture spacing, fracture conductivity, and fracture distribution are optimized with orthogonalization factor analysis, and the influence of sulfur deposition on different fracture parameters are detailed analyzed. The results shown that the fracture half-length and fracture conductivity are greatly affected by sulfur deposition. Finally, net profit value is applied to obtain the optimal fracture spacing interval. With economic evaluation, the optimal fracture spacing interval of 125 m∼ 150 m is determined considering the net profit and the payback period. This work provides a useful economic method for fracture parameter optimization high-sulfur gas reservoirs, which benefits for the development and production of gas reservoirs.

Study on deposit formation model in sulfide-containing natural gas environment

The breathing pipe of a produced water storage tank in a sulfide-containing natural gas station is prone to deposit formation, which leads to pipeline blockage. In this study, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) analyses of the deposit in breathing pipe show that the deposit is composed of elemental sulfur and corrosion scales of ferrous polysulfide and ferrous sulfate. Existing deposit formation prediction models cannot predict the formation of elemental sulfur and corrosion scales in sulfide-containing environments. Herein, based on thermodynamic models of elemental sulfur and corrosion scale formation, deposit formation models of elemental sulfur, ferrous polysulfide, and ferrous sulfate scale formation are established. It is found that deposition of elemental sulfur and ferrous polysulfide increases with decreasing temperature of the breathing tube. Corrosion of pipe in the precipitating corrosive water leads to higher activity of left[{mathrm{Fe}}^{2+}right] on the inner wall of the pipe carried by the sulfide-containing natural gas. Consequently, ferrous polysulfide and ferrous sulfate are easily deposited when the activity products of ferrous, sulfide, and sulfate ions are higher than the thermodynamic solubility product constant. The aforementioned prediction models are applied to predict the deposition of ferrous polysulfide, ferrous sulfate corrosion scale, and elemental sulfur using the chemical composition data of gas and precipitating water in the breathing pipe of the produced water tank of TB101-X1 well. The prediction results of the models are consistent with those of actual chemical composition analysis, which verifies the accuracy and reliability of the models.

Effect of CuO addition on the performance of V2O5-based oxygen carriers for chemical-looping oxidation of H2S for efficient sulfur recovery from natural gas

Integrating Chemical-Looping process with Selective Oxidation of H2S (CLSO) at low temperature is a novel method to achieve efficient desulphurization and sulfur recovery from nature gas. In CLSO process, a reducible catalytic oxygen carrier (COC) is need to cyclically transport oxygen from air to H2S in gaseous fuels. For energy saving, it must have adequate catalytic sites that can selectively convert H2S to elemental sulfur at temperature as low as possible, meanwhile COCs do not combust nature gas, and for continuously operation the reduced COCs can be fully regenerated with air. COC development is key issue for the successful deploying CLSO process. Based on CLSO concept given by previous work (Kane, 2019), this study developed various V2O5-based COCs with and without CuO addition using TiO2- and Al2O3- supports of stableporousstructures, trying to improve the overall performance of COCs. By cyclic CLSO experiments, the desirable features of the new COCs were examined, and the effects of CuO addition on oxygen transport, catalytic behaviors, and chemical stabilities were specially assessed. This study also revealed the selective oxidation reaction mechanisms of H2S with these V2O5-based COCs, and identified the roles of CuO in catalytic redox reaction. It is demonstrated that the reactivities of V2O5 phase was greatly promoted as supported on porous supports; CuO phase enhanced significantly oxygen transport capacities of COCs as it was reduced to metallic copper in selective oxidation of H2S. Elemental sulfur deposition, H2S adsorption, and metallic sulfide formation put impacts to selectivity, and further study to improve COC selectivity is needed.

Dual-Layer Sulfur Cathode Integrating Sulfur Composite Electrode and Binder-Free Sulfur Thin Film for High Loading Li-S Batteries

The Lithium-sulfur (Li-S) battery is one of the most promising future electrochemical energy storage systems owing to the intrinsic advantages of sulfur such as its high energy density, low cost, and innocuous nature. For several decades, many research teams have tried to develop high performance Li-S batteries. Recently, various approaches for high sulfur loading have been demonstrated to achieve high energy density Li-S batteries. Many types of porous carbon materials (e.g., graphene, mesoporous carbons, hollow carbon spheres, and carbon nanotubes) have been used as a sulfur host. In many cases, however, the large-scale implementation to Li-S batteries has been discouraged due to the non-scalable synthesis process of these carbon materials. To improve the energy density of a sulfur cathode, we demonstrate a dual-layer sulfur cathode composed of a S-filled carbon electrode and a sulfur deposit film. First, a sulfur electrode was fabricated by uniformly embedding sulfur within the porous network of a carbon film. Then, an ultra-thin sulfur layer was constructed on the surface of the sulfur electrode through physical vapor deposition (PVD) of elemental sulfur

Effect of H2S concentrations on corrosion failure of L245NS steel in CO2-O2-H2S system

The corrosion behavior of L245NS steel with different gas environments and H2S concentrations in CO2-O2-H2S environment were studied by weight-loss test and surface characterization techniques. It was found that in the CO2-O2-H2S environment, the H2S, CO2, and O2 reacted successively, and the deposition and hydrolysis acidification of elemental sulfur aggravated the occurrence of localized corrosion. When H2S changed in the low concentration range (1000 – 5000 ppmv), the reaction was dominated by the gradual development of the dense inner film, which decreased the corrosion degree. At 10,000 ppmv, the solution pH value would decrease. More H2S was involved in hydrogen evolution corrosion and enhanced the synergistic effect with O2 to accelerate the corrosion.

Transient analysis of horizontal wells with multiple fractures in sour gas reservoirs

Due to the decrease of reservoir pressure, the elemental sulfur deposits in sour gas reservoirs, leading to the reduction in the reservoir porosity and permeability. It can also impact the transient pressure and rate behavior of gas wells, which is always reflected in pressure and flow rate type curves. However, few studies focus on transient analysis of multi-fractured horizontal wells affected by sulfur deposition. Therefore, the objective of this work is to develop a comprehensive model to analyze the transient pressure and flow rate of multi-fractured horizontal wells in sour gas reservoirs. Pseudo-time function and pseudo-pressure function are derived and the point source method is applied in this model. Then the proposed model is validated against analytical solutions and real production data. Furthermore, sensitivity analysis for pressure and rate type curves was conducted. Results show that the pressure type curves can be divided into six stages. The reservoir with higher H2S concentration will result in more sulfur deposition, which requires larger pressure difference to maintain a constant rate in the late time. Fracture properties impact flow rate in the early production time, and increasing fracture conductivity and fracture number is helpful to reduce the generation of sulfur deposition. For a smaller reservoir, larger pressure difference is essential to stabilize constant production rate, which means more sulfur deposition will be produced in the reservoir. During the development of sour gas reservoir, it is important to control flow rate to reduce pressure depletion for decrease amount of sulfur deposition. This paper reveals the impacts of sulfur deposition on type curves and provides a comprehensive transient analysis for multi-fractured horizontal wells in the development of sour gas reservoirs.

Microwave Sensing of Elemental Sulfur Deposition in Gas Pipelines

A novel electromagnetic-based method is presented for monitoring elemental sulfur deposition within a natural gas-carrying pipeline. The deposited sulfur behaves as a superstrate layer above a sensing microstrip patch antenna that is optimally placed on the inner wall of the gas pipeline. Increasing the superstrate thickness by the sulfur deposition alters the antenna resonance behavior, which can be monitored externally using a vector network analyzer. The effect of uneven or bumpy sulfur deposition is studied. Sensing antennas positioned outside a plexiglass pipeline are also investigated to observe the change in the antenna impedance matching with accumulating sulfur superstrate. A variation in the resonance frequency of the invasive sensing antenna from 10.14 to 8.32 GHz is observed for a deposited sulfur thickness that ranges from 0–7 mm. The sensing sensitivity is found to be 0.23 GHz/mm. Lab-based measured results agreed well with the simulated responses using commercial electromagnetic software. The proposed low-cost and easy-to-implement detection technique accurately estimates the deposited sulfur thickness inside the natural gas-carrying pipelines.

The elemental sulfur ore deposit of Salmerón: Las Minas de Hellín basin (Late Miocene, SE Spain)

Strata-bound elemental sulfur deposits occur in different circum-Mediterranean Miocene sedimentary successions containing evaporites and high amounts of organic matter. It is widely known that bacterial sulfate reduction processes are the triggering mechanisms involved in the origin of hydrogen sulfide and the subsequent native sulfur. However, in most of these sedimentary successions, there is controversy over whether elemental sulfur formed in the basin floor, as the same time as the sediments (biosyngenetic), or later, during diagenesis (bioepigenetic). Las Minas de Hellín basin, in the SE Spain, contains one of the largest elemental sulfur deposits in Europe. Based on data recovered from mining company (1903 -1960) and a borehole campaign performed by MINERSA between 1987 and 1988, two native sulfur ore bodies are recognized. The upper sulfur body is hosted by carbonates and diatom-rich levels, whereas the lower sulfur body, only exploited in underground mines now closed, is hosted by gypsum. This work shows a petrological and geochemical study of core samples from the upper sulfur body in the Salmerón area (Murcia), 500 m west of the widely exploited area of Las Minas de Hellín (Albacete). In Salmerón, elemental sulfur occurs as pseudomorphs after primary sedimentary gypsum as well as filling fractures and bed joints. The elemental sulfur replacement is also related to calcification and silicification of the sedimentary biomediated dolomite. The mineralization is considered bioepigenetic formed during early diagenesis. Contribution from hydrothermal waters circulating through adjacent faults are not ruled out.

Enhanced sulfur selectivity for H2S catalytic oxidation over Fe2O3@UiO-66 catalyst

Fe2O3 as a catalyst for H2S oxidation, has a high catalytic activity but a low sulfur selectivity. In this regard, a series of Fe2O3 supported on UiO-66 complex catalysts (xFe2O3@UiO-66, x represents the weight percentage of Fe2O3) with high sulfur selectivity were successfully synthesized, and their catalytic performance was investigated at varied reaction temperature (100–210 ℃). The experimental results indicate that 5Fe2O3@UiO-66 catalyst shows the best catalytic performance at 150 ℃, the H2S conversion keep at 100% and the sulfur selectivity reaches 93.06%, which is significantly higher than the bulk Fe2O3 (62%) and commercial Fe2O3 (80%). The superior catalytic performance is mainly attributed to the synergistic effect between Fe2O3 and UiO-66, the formed FeOZr bonds help the electrons transfer from Fe to Zr, which inhibits the formation of the intermediate of FeS2 during the catalytic process, a species that readily to be oxidized into SO2, thus promotes its sulfur selectivity. In addition, the high specific surface area, abundant pores and the high dispersion of Fe2O3 nanoparticles also contributed to its improved sulfur selectivity. The deposition of elemental sulfur and sulfates responsible for its deactivation.

Enhancement mechanism of polyoxyethylene nonyl phenyl ether on the bioleaching of chalcopyrite

Chalcopyrite is the most abundant copper-bearing mineral in nature. Due to technological limitations, a large amount of low-grade chalcopyrite is discarded, which causes a large waste of resources and a series of environmental problems. Bioleaching is a low-consumption technology that plays an important role in treating low-grade minerals. However, the leaching efficiency of chalcopyrite is too low for industrial production. This study proposes the use of polyoxyethylene nonyl phenyl ether (NP-15) to improve the bioleaching efficiency of chalcopyrite. The effects of concentration and adding time of NP-15 on copper extraction were investigated. After 30 days bioleaching, the copper concentration in the leaching solution was 930.91 mg/L with the addition of 20 mg/L of NP-15. In contrast, the copper concentration was observed to be 385.62 mg/L in the absence of NP-15. The optimum adding time was the 6th day after the start of the bioleaching process. The analysis of the results of X-ray diffraction (XRD), Raman spectroscopy, and the electrochemical tests revealed that the presence of NP-15 was beneficial to reduce the deposition of elemental sulfur on the chalcopyrite surface. Moreover, NP-15 promoted the oxidation of elemental sulfur by Acidithiobacillus ferrooxidans. The contents of elemental sulfur and polysulfide in the passivation layer were reduced. Additionally, NP-15 reduced the surface tension of the leaching solution, which was beneficial for improving the contact between the leaching solution and chalcopyrite surface. Thus, the bioleaching efficiency was improved. This study provides a reference for the application of surfactants to enhance the bioleaching of chalcopyrite ores.

Fractal Model for Predicting Elemental Sulfur Saturation in the Presence of Natural Fracture.

Sour gas reservoirs are an important part of unconventional gas reservoirs, which are widely distributed in the world. However, elemental sulfur deposition, channel plugging, and productivity reduction consequentially occur in the development of high sour gas fields as pressure drops. The accurate prediction of sulfur deposition is a very important work for sour gas reservoirs. In this paper, a fractal model is presented for predicting elemental sulfur saturation in the presence of natural fracture. The model takes into consideration the effects of non-Darcy flow. In addition, the influence parameters such as fractal dimension, fractal index, and non-Darcy flow are studied. The results showed the following: (1) sulfur deposition was overestimated by Hu’s model, and this paper model is more accurate for prediction of sulfur deposition; (2) elemental sulfur deposition decreases with the increase of the fractal dimension, while elemental sulfur deposition increases with the decrease of the fractal index; and (3) non-Darcy flow should be considered because it causes a faster rate of sulfur deposition. This research will provide a basis and reference for predicting elemental sulfur saturation in the presence of natural fracture for sour gas reservoirs.

A Novel Model for Predicting the Well Production in High-Sulfur-Content Gas Reservoirs

High-content H2S gas reservoirs are important for natural gas extraction. However, the precipitation and deposition of elemental sulfur in high-sulfur-content gas reservoirs eventually lead to porosity and permeability damage, resulting in the low well productivity. Therefore, it is worth developing an accurate production prediction model considering sulfur deposition for fractured horizontal wells. In this study, based on the partition model and transient percolation theory, a novel numerical model considering the damage of sulfur deposition with pressure change on reservoir porosity and permeability was first developed to predict the production from fractured horizontal wells in high-sulfur-content gas reservoirs. Then, it was validated by actual field data from a high-sulfur-content gas reservoir. After that, the influence of sulfur deposition on the production of fractured horizontal wells was revealed through theoretical calculations, and the effects of hydraulic fracture parameters on production were analyzed. The results show that elemental sulfur gradually deposits in the reservoir pores as the reservoir pressure decreases and the production time increases, which eventually leads to permeability damage and reduces reservoir productivity; this negative impact gradually increases over time. It is also shown that the production of fractured horizontal wells increases with an increase in the half-length, fracture conductivity, and fracture number. Compared with the fracture half-length, the fracture conductivity and fracture number have a greater influence on the production of a single well. The model can handle the influence of nonlinear parameters caused by sulfur deposition, which allows accurate calculations and provides guidance for the development of fractured horizontal wells in gas reservoirs with high sulfur content.

The Seven Sisters Hydrothermal System: First Record of Shallow Hybrid Mineralization Hosted in Mafic Volcaniclasts on the Arctic Mid-Ocean Ridge

We document the discovery of an active, shallow, seafloor hydrothermal system (known as the Seven Sisters Vent Field) hosted in mafic volcaniclasts at a mid-ocean ridge setting. The vent field is located at the southern part of the Arctic mid-ocean ridge where it lies on top of a flat-topped volcano at ~130 m depth. Up to 200 °C phase-separating fluids vent from summit depressions in the volcano, and from pinnacle-like edifices on top of large hydrothermal mounds. The hydrothermal mineralization at Seven Sisters manifests as a replacement of mafic volcaniclasts, as direct intraclast precipitation from the hydrothermal fluid, and as elemental sulfur deposition within orifices. Barite is ubiquitous, and is sequentially replaced by pyrite, which is the first sulfide to form, followed by Zn-Cu-Pb-Ag bearing sulfides, sulfosalts, and silica. The mineralized rocks at Seven Sisters contain highly anomalous concentrations of ‘epithermal suite’ elements such as Tl, As, Sb and Hg, with secondary alteration assemblages including silica and dickite. Vent fluids have a pH of ~5 and are Ba and metal depleted. Relatively high dissolved Si (~7.6 mmol/L Si) combined with low (0.2–0.4) Fe/Mn suggest high-temperature reactions at ~150 bar. A δ13C value of −5.4‰ in CO2 dominated fluids denotes magmatic degassing from a relatively undegassed reservoir. Furthermore, low CH4 and H2 (<0.026 mmol/kg and <0.009 mmol/kg, respectively) and 3He/4He of ~8.3 R/Racorr support a MORB-like, sediment-free fluid signature from an upper mantle source. Sulfide and secondary alteration mineralogy, fluid and gas chemistry, as well as δ34S and 87Sr/86Sr values in barite and pyrite indicate that mineralization at Seven Sisters is sustained by the input of magmatic fluids with minimal seawater contribution. 226Ra/Ba radiometric dating of the barite suggests that this hydrothermal system has been active for at least 4670 ± 60 yr.

Manganese oxide-based porous electrodes for rapid and selective (electro)catalytic removal and recovery of sulfide from wastewater

Sulfide and its removal is a major concern in wastewater treatment as it represents a threat to human health and the structural integrity of the water distribution system. In this study, we demonstrated for the first time an exceptional performance of manganese oxide-coated graphite felt (GF-MnxOy) electrodes for selective sulfide oxidation to sulfur. Oxidation state, loading, morphology and crystallinity of MnxOy coating was tuned using electrodeposition synthesis method to enable an efficient and selective sulfide oxidation to sulfur. Excellent (electro)catalytic activity of GF-MnxOy yielded up to 25-fold increase in sulfide removal rates compared to pristine GF, both in the open circuit (OC, no applied potential) and under anodic polarization at 0.4 V vs Standard Hydrogen Electrode (SHE). Although anodic polarization did not further enhance sulfide oxidation rate compared to OC, it enabled a continuous re-oxidation of the reduced MnxOy coating after its reaction with sulfide. Thus, restoring of the catalytic properties of MnxOy coating enabled higher sulfide removal rates compared with the OC experiment. The formed elemental sulfur remained at the surface of GF-MnxOy leading to a gradual electrode passivation. The deposited sulfur was successfully dissolved by reversing the polarity of the GF-MnxOy electrode to -0.8 V vs SHE. However, full electrode recovery and restoring of the initial sulfide removal rates could not be achieved as cathodic polarization at -0.8 V vs SHE during longer time (>3 hours) required to remove S0 also caused a partial dissolution of the MnxOy coating. (Electro)catalytic sulfide removal was somewhat decreased in real sewage (2.42 ± 0.02 h-1 vs 0.93 ± 0.15 h-1 in NaNO3 supporting electrolyte and real sewage, respectively). The selectivity of the process towards deposition of elemental sulfur was decreased in real sewage due to partial production of colloidal sulfur, which was presumably caused by diffusion limitation imposed by presence of other ions. Due to lesser extend of GF-Mn2O3 electrode passivation in real sewage, sulfide removal rates remained stable over six subsequent application cycles. In summary, MnxOy-based electrodes demonstrated exceptional (electro)catalytic activity and selectivity for sulfide oxidation to sulfur and thus its complete separation from water. Upscaling of the proposed electrochemical system and its application for the treatment of complex wastewater streams requires further efforts to maintain the selectivity towards deposited sulfur as a final product and allow its complete recovery.

Continuous Oxidation of Hydrogen Sulfide by an Adsorbent Derived from Sewage Sludge

Desulfurization (deS) material is usually deactivated because elemental sulfur formed during deS and covers the material surface. In this study, a novel strategy was proposed for a continuous oxidization of hydrogen sulfide (H2S) by a sewage sludge-derived adsorbent without elemental-sulfur deposition. At temperatures <180°C, the sludge-derived adsorbent was deactivated and showed limited deS amount of 0.27 mmol/g at 60 min. Scanning Electron Microscope (SEM) and Fourier Transform infrared spectroscopy showed that carbon sites of the deactivated adsorbent were covered by elemental sulfurs. After the deactivated adsorbent was regenerated at 200°C, it showed a deS amount of 0.25 mmol/g again. On the contrary, at temperatures >180°C, the adsorbent achieved a stable deS without deactivation, resulting in a deS amount of 121.82 mmol/g at 20 h. In this case, yellow particles evolved from the adsorbent. X-ray diffraction and Thermogravimetric Analysis both proved that the particles were sulfur. Sulfur outflow was a key factor determining the regeneration of active carbon sites and continuous oxidization of H2S. This study will help the development of a low-cost adsorbent for H2S purification.

Effects of Groundwater Nitrate and Sulphate Enrichment on Groundwater-Fed Mires: a Case Study

Mires and peatlands in general are heavily influenced by anthropogenic stressors like acidification, eutrophication, desiccation and fragmentation. Groundwater-fed mires are, in contrast to rainwater-fed mires, often well protected against desiccation due to constant groundwater discharge. Groundwater-fed mires can however be influenced by groundwater pollution such as groundwater nitrate enrichment, a threat which has received minor attention in literature. The present case study demonstrates how groundwater nitrate enrichment can affect the biogeochemical functioning and vegetation composition of groundwater-fed mires through direct nitrogen enrichment and indirect nitrate-induced sulphate mobilisation from geological deposits. Biogeochemical and ecohydrological analyses suggest that the Dutch groundwater-fed mire studied is influenced by different water sources (rainwater; groundwater of local and regional origin) with differing chemical compositions. The weakly buffered and nitrate-enriched groundwater leads, where it reaches the uppermost peat, to nitrogen enrichment, enhanced isotopic nitrogen signatures and altered the vegetation composition at the expense of characteristic species. Nitrate-induced sulphate mobilisation in the aquifer led to enhanced sulphate reduction, sulphide toxicity and elemental sulphur deposition in the mire. Despite sulphate reduction and nitrate enrichment, internal eutrophication did not play an important role, due to relatively low phosphorus concentrations and/or low iron-bound phosphorus of the peat soil. Future management of groundwater-fed mires in nitrate-polluted aquifers should include the reduction of nitrate leaching to the aquifer at the recharge areas by management and ecohydrological restoration measures on both a local and landscape scale.

Formation of Large Native Sulfur Deposits Does Not Require Molecular Oxygen.

Large native (i.e., elemental) sulfur deposits can be part of caprock assemblages found on top of or in lateral position to salt diapirs and as stratabound mineralization in gypsum and anhydrite lithologies. Native sulfur is formed when hydrocarbons come in contact with sulfate minerals in presence of liquid water. The prevailing model for native sulfur formation in such settings is that sulfide produced by sulfate-reducing bacteria is oxidized to zero-valent sulfur in presence of molecular oxygen (O2). Although possible, such a scenario is problematic because: (1) exposure to oxygen would drastically decrease growth of microbial sulfate-reducing organisms, thereby slowing down sulfide production; (2) on geologic timescales, excess supply with oxygen would convert sulfide into sulfate rather than native sulfur; and (3) to produce large native sulfur deposits, enormous amounts of oxygenated water would need to be brought in close proximity to environments in which ample hydrocarbon supply sustains sulfate reduction. However, sulfur stable isotope data from native sulfur deposits emplaced at a stage after the formation of the host rocks indicate that the sulfur was formed in a setting with little solute exchange with the ambient environment and little supply of dissolved oxygen. We deduce that there must be a process for the formation of native sulfur in absence of an external oxidant for sulfide. We hypothesize that in systems with little solute exchange, sulfate-reducing organisms, possibly in cooperation with other anaerobic microbial partners, drive the formation of native sulfur deposits. In order to cope with sulfide stress, microbes may shift from harmful sulfide production to non-hazardous native sulfur production. We propose four possible mechanisms as a means to form native sulfur: (1) a modified sulfate reduction process that produces sulfur compounds with an intermediate oxidation state, (2) coupling of sulfide oxidation to methanogenesis that utilizes methylated compounds, acetate or carbon dioxide, (3) ammonium oxidation coupled to sulfate reduction, and (4) sulfur comproportionation of sulfate and sulfide. We show these reactions are thermodynamically favorable and especially useful in environments with multiple stressors, such as salt and dissolved sulfide, and provide evidence that microbial species functioning in such environments produce native sulfur. Integrating these insights, we argue that microbes may form large native sulfur deposits in absence of light and external oxidants such as O2, nitrate, and metal oxides. The existence of such a process would not only explain enigmatic occurrences of native sulfur in the geologic record, but also provide an explanation for cryptic sulfur and carbon cycling beneath the seabed.

A comprehensive model for dynamic characteristic curves considering sulfur deposition in sour carbonate fractured gas reservoirs

Calculating sulfur deposition is a key issue in developing sour gas reservoirs, where sulfur solubility plays an important role. However, prediction of sulfur solubility is a difficult problem due to the toxic of H2S. In this work, an analytical model for dual porosity media considering the influence of sulfur deposition was proposed. The Douglas-Jones predictor-corrector method is used to calculate a relationship between time and pressure, which can avoid solving the system of nonlinear equations. The effects of sulfur deposition on well performance were analyzed and some dynamic characteristic curves for predicting sulfur deposition were provided. The results show that the fastest pressure drop appears near the wellbore, which is the primary damage zone for elemental sulfur precipitation and deposition. Flow parameters and storage ratio play the significant influences on the sulfur saturation curve shape. In addition, the reduction of flow parameters and storage ratio lead to the increase of sulfur saturation and decrease of permeability, resulting in the damage of sour gas formation. The advantage of this approach is that it can be used to describe a characteristic curve without considering the sulfur solubility issue. This paper provides a novel method to analyze the impacts of sulfur deposition on well performances in sour carbonate fractured gas reservoirs.

Cyanobacterial Diversity and the Role of Cyanobacteria in Formation of Minerals in the Baunt Group Hydrotherms (Baikal Rift Zone)

A comprehensive research of water and cyanobacterial mats in Mogoysky and Shurindinsky thermal springs (Baikal rift zone) was carried out by hydrochemical, chemical, microbiological, and mineralogical methods. Detailed descriptions of the springs location and their characteristics were given. According to their chemical composition, the springs were classified as fluoride-bicarbonate (Mogoysky) and bicarbonatesulfate (Shurindinsky) types with a high concentration of fluorine. This is explained by the interaction of infiltration waters with embedding rocks. A wide diversity of cyanobacteria (14 species of 7 genera) was revealed in the investigated springs. The development of cyanobacteria in microbial mats was observed at water outflows at the temperatures of 37.8 to 76.6°C. Chlorophyll a was the predominant pigment in microbial mats of the studied springs, indicating predominance of cyanobacteria in the mat. Deposition of various pyrite forms, celestite (SrSO4), fluorite (CaF2), calcium carbonate, elemental sulfur, barite, and amorphous silica was found in microbial mats.

A review of elemental sulfur deposition in high sulfur-content natural gas transmission pipeline

High sulfur-content natural gas includes hydrogen sulfide, mercaptans, sulfoethers, and other sulfurous substances, with the major component being hydrogen sulfide. The development of high sulfur-content natural gas fields worldwide ensures the supply of not only clean energy, but also raw materials for industrial sulfur products. However, supersaturated precipitation of gaseous sulfur yields solid sulfur particles by nucleation, coagulation, and agglomeration with changing operation pressure, temperature, and species and concentration of gas components in high sulfur-content natural gas transmission pipelines. The solid particles will flow with the natural gas, and when the dynamic conditions for particle deposition are fulfilled, they will be deposited in pipeline. The deposition of solid sulfur particles will cause blockages in the transmission pipeline; furthermore, the elemental sulfur contacting the metal surface of the pipeline will cause electrochemical and chemical corrosion reactions. Eventually, the consequences of sulfur deposition in high sulfur-content natural gas transmission pipelines will cause serious hazards for pipeline operation and production. This paper summarizes the advances in the calculation of the sulfur gas-solid phase equilibrium, understanding of the growth and ablation kinetics mechanism of solid sulfur particles, and development of a gas-solid two-phase flow mathematical model. To fulfill the need for theory and experimental methods for predicting and preventing sulfur deposition in high sulfur-content natural gas transmission pipelines, the following three topics should be emphasized in future studies: First, limited experimental data is available on elemental sulfur solubility in sour gas at the pressure and temperature conditions of transmission pipelines, so sulfur solubility measurements should be established in the pressure and temperature range ( P ≤15.0 MPa, T ≤333.15 K) of transmission pipelines, considering the very low sulfur solubility under these conditions. Second, mathematical models of solid sulfur particle growth kinetics should be established based on molecular dynamics (MD) simulations with statistical mechanics and thermodynamics, combined with crystallization kinetics theory to determine nucleation, growth, and ablation behavior under the conditions of natural gas transmission pipelines. Third, mathematical models of the gas-solid two-phase flow in the transmission pipelines should be built considering the gas-solid phase change of elemental sulfur, and the growth and ablation of sulfur particles these models should involve the coupling effects of multiple parameters such as pipeline pressure, temperature, gas composition, and flow rate. These models could provide a quantitative description of elemental sulfur precipitation, sulfur particle growth, and particle flow behavior in high sulfur-content natural gas. Accordingly, the exact quantity and position of elemental sulfur deposition in high sulfur-content natural gas transmission pipelines can be predicted. These achievements will contribute to sulfur deposition prevention and improvement of control technology, as well as provide technical support for the design and management of high-sulfur natural gas transmission pipelines.