Low Salinity Water Research Articles

Experimental Investigation about Oil Recovery by Using Low-Salinity Nanofluids Solutions in Sandstone Reservoirs

Production of crude oil from matured oil reservoirs has major issues due to decreased oil recovery with water channeling; however, the low-salinity water flooding technique is more commonly used to maximize recovery of the remaining oil. In this study, we demonstrated a new hybridization technique of combining low-salinity water and nanofluids; this was achieved by using experiments such as contact angle measurement with water of different salinity levels and nanofluid concentrations, core displacement, and NMR (nuclear magnetic resonance) between low-/high-permeability rock. The trial results demonstrated that the test with KCl-1+NF outperformed those with other compositions by changing the original contact angle from 112.50° to 53.3° and increasing formation production up to 15 cc. In addition, we saw that when 2 PV of KCl-1+NF was injected at a rate of 5 mL/min, the middle pores’ water saturation dropped quickly to 73% and then steadily stabilized in the middle and late stages. Regarding the novel application of the hybridization technique, the insights presented in this paper serve as a helpful resource for future studies in this field.

Seasonal Water Mass Transformation in the Eastern Indian Ocean from In Situ Observations

The Eastern Indian Ocean (EIO) is one of the eastern boundary areas, which control currents circulation and atmospheric dynamics. This research mainly aimed to identify and analyze the water mass transformation in the EIO. The investigated physical properties of the ocean are the temperature, salinity, seasonal temperature–salinity, and water column stability. An extensive amount of in situ data measurements from 1950 to 2018 was downloaded from the global datasets inventory. The visualization and analysis of the data were defined in monthly spatial and vertical profiles. The result showed the mixed layer is shallower during the northwest monsoon relative to the southwest monsoon. The surface water in the EIO is documented to be warmer due to the interaction with the atmosphere. Furthermore, low-salinity surface water around the Java Seas area is caused by a mixing with fresh water from the eastern Indonesia rivers. The data also confirmed that, at latitude 16° S, the maximum salinity occurred at a depth between 150 and 350 m. There are ten types of water masses found in the EIO, which originate from several regions, including the Indonesia Seas, Pacific Ocean, Indian Ocean, and Antarctic. During the northwest and southeast monsoons, a stable layer is found at a depth of 40 to 150 m and 80 to 150 m, respectively. For further research, it is recommended to focus on the coastal region, particularly the Timor Sea and Northwestern Australia, to investigate the dynamics between the Indonesian Throughflow, Holloway Currents, and Leeuwin Currents. Additionally, deep water observations below 800 m are crucial for a comprehensive understanding of the oceanographic variability in the deep layers of the EIO.

Blocking a Flow Conductive Inter-well Fault by Fines Detached by a Low-Salinity Water Slug

Blocking a Flow Conductive Inter-well Fault by Fines Detached by a Low-Salinity Water Slug

Decadal comparisons identify the drivers of persistent changes in the zooplankton community structure in the northwest Atlantic

Abstract Plankton community structure changes seasonally in response to the annual cycles of stratification, temperature, and primary productivity. These communities also change from year-to-year, in some cases exhibiting persistent regime shifts. How changes in physical conditions structure the plankton community and why conditions persist is a fundamental question in oceanography. Continuous plankton recorders have been used to sample the plankton community across the Gulf of Maine since 1961. Historically, this community has had a classic subarctic structure dominated by Calanus finmarchicus. However, during the 1990s, C. finmarchicus became less prominent, and a more diverse community of smaller copepods emerged. This shift was related to an influx of cold, low-salinity water. We show that a similar community shift occurred around 2012. We use high-resolution hydrographic data to link the shift to an influx of saltier water and warmer conditions. By comparing the 1990s with the recent decade, we develop a synthesis for how physical changes lead to community shifts. Our synthesis suggests that the link between the 1990s and 2010s is enhanced water column stratification. We further propose that ecological interactions link declines in C. finmarchicus with the emergence of the more diverse community, drawing parallels with classic food web ecology.

The potential of electrodialysis as a cost-effective alternative to reverse osmosis for brackish water desalination

While electrodialysis (ED) demonstrates lower energy consumption than reverse osmosis (RO) in the desalination of low salinity waters, RO continues to be the predominant technology for brackish water desalination. In this study, we probe this skewed market share and project the potential for future disruption by ED through systematic assessment of the levelized cost of water (LCOW). Using rigorous process- and economic-models, we minimize the LCOW of RO and ED systems, highlighting important tradeoffs between capital and operating expenditure for each technology. With optimized current state-of-the-art systems, we find that ED is more economical than RO for feed salinities ≤ 3 g L−1, albeit to a minor extent. Considering that RO is a highly mature technology, we focus on predicting the future potential of ED by evaluating plausible avenues for capital and operating cost reduction. Specifically, we find that reduction in the price of ion-exchange membranes (i.e., < 60 USD m−2) can ensure competitiveness with RO for feed salinities up to 5 g L−1. For higher feed salinities (≥ 5 g L−1) we reveal that the LCOW of ED may effectively be reduced by decreasing ion-exchange membrane resistance, while preserving high current efficiency. Through extensive assessment of structure-property-performance relationships, we precisely identify target membrane charge densities and diffusion coefficients which optimize the LCOW of ED, thus providing novel guidance for future membrane material development. Overall, we emphasize that with a unified approach — whereby ion-exchange membrane price is reduced and performance is enhanced — ED can become the economically preferable technology compared to RO across the entire brackish water salinity range.

Hybrid low salinity water and surfactant process for enhancing heavy oil recovery

Combining low salinity water (LSW) with surfactants has an enormous potential for enhancing oil recovery processes. However, there is no consensus about the mechanisms involved, in addition to the fact that several studies have been conducted in model systems, while experiments with rocks and reservoir fluids are scarce. This study presents a core-flooding experiment of LSW injection, with and without surfactant, using the core and heavy oil samples obtained from a sandstone reservoir in southeastern Mexico. The effluents and the crude oil obtained at each stage were analyzed. The study was complemented by tomographic analysis. The results revealed that LSW injection and hybrid process with surfactants obtained an increase of 11.4 percentage points in recovery factor. Various phenomena were caused by LSW flooding, such as changes in wettability and pH, ion exchange, mineral dissolution, detachment of fines and modification of the hydrocarbon profile. In the surfactant flooding, the reduction of interfacial tension and alteration of wettability were the main mechanisms involved. The findings of this work also showed that the conditions believed to be necessary for enhanced oil recovery with LSW, such as the presence of kaolinite or high acid number oil, are not relevant.

Using Unoccupied Aerial Systems (UASs) to Determine the Distribution Patterns of Tamanend’s Bottlenose Dolphins (Tursiops erebennus) across Varying Salinities in Charleston, South Carolina

The Charleston Estuarine System Stock (CESS) of Tamanend’s bottlenose dolphins (Tursiops erebennus) exhibit long-term site fidelity to the Charleston Harbor, and the Ashley, Cooper, and Wando Rivers in Charleston, South Carolina, USA. In the Cooper River, dolphins have been irregularly sighted in upper regions where salinity levels are below what is considered preferred dolphin habitat. We conducted unoccupied aerial system (UAS) surveys in high-salinity (&gt;15 parts per thousand) and low-salinity (&lt;15 parts per thousand) regions (n = 8 sites) of the Cooper River and surrounding waters to assess dolphin distribution in terms presence/absence, detection rate, abundance, and density. We also assessed the influence of ecological factors (salinity, water temperature, season, and prey availability) on dolphin distribution. Dolphins were detected at five sites, with higher salinity and water temperature being significant predictors of presence and abundance. Dolphins were detected year-round across high-salinity sites, and were infrequently detected in low-salinity sites during months with warmer water temperatures. The results from this study contribute to the overall understanding of dolphin distribution across various habitats within the Charleston Estuary System and the potential drivers for their movement into low-salinity waters.

Habitat salinity and source-induced variation in body shape of euryhaline long whiskers catfish (Mystus gulio)

The study was carried out to investigate the body shape variation of the Mystus gulio collected from three different salinity gradient habitats (high-salinity brackish water, low-salinity brackish water, and freshwater) and two different sources (wild and hatchery) using linear morphometric distances, landmark-based truss-networking and geometric morphometrics. A total of 436 individuals of M. gulio were collected from the high-salinity (8–15 ppt), low-salinity (2–6 ppt), and freshwater bodies (0 ppt). For wild versus hatchery sources body shape variation, 430 individuals of M. gulio were collected from various coastal rivers and hatcheries. M. gulio from different salinity gradient habitats and sources exhibited negligible sexual dimorphism. Principal component analysis (PCA) indicated that high and low salinity populations appeared to form overlapping clusters with the freshwater populations, but other multivariate analyses discriminated both populations from brackishwater habitats from the freshwater counterparts. The geometric morphometrics displayed that the body shape variation of M. gulio from salinity gradient habitats was mainly visible in the width of the dorsal-ventral part, the snout shape, the tail shape, the head region, and the eye diameter. PCA demonstrated that multivariate spaces of both the wild and captive populations overlapped each other, although many individuals of the wild population were discriminated from the culture populations. Our results showed that truss networking and geometric morphometric methods provide consistent outcomes for body shape discrimination in the M. gulio populations.

Geological controls on the geothermal system and hydrogeochemistry of the deep low-salinity Upper Cretaceous aquifers in the Zharkent (eastern Ily) Basin, south-eastern Kazakhstan

The Zharkent (eastern Ily) Basin is renowned for its low-salinity natural hot springs and geothermal wells, primarily utilized for recreational purposes. Despite the growing commercial interest, the geothermal system in this area is very poorly documented or understood. Accordingly, we conducted a multi-disciplinary study, focusing on the advanced characterization of waters from productive Cretaceous strata, along with the interpretation of geothermal gradients and reservoir recharge in a geological context. Conventional wisdom asserts that Ily is an intracratonic basin characterized by high geothermal heat in its central part and by geothermal aquifers that are rapidly replenished by meteoric water recharge via porous strata exposed on the basin margin. Our results argue for an alternative and expanded interpretation of these systems. Elevated geothermal gradients (with average of up to 40°C/km in the southern part of the basin and locally possibly up to 55°C/km) are likely associated with crustal thinning owing to the development of a pull-apart basin. Anomalously fresh water (&amp;lt;1 g/L) in the deep (up to 2850 m depth) Upper Cretaceous reservoir is charged laterally, predominantly by snowmelt waters from basin bounding mountains. Recharge includes both mountain-front recharge (MFR), where water infiltrates into outcrops of reservoir rock near the mountain fronts, and mountain-block recharge (MBR), characterized by deep groundwater flow through fractured, predominantly rhyolite basement rocks (as evidenced from their solutes in reservoir waters). The combination of elevated geothermal gradients, low salinity water chemistry, and excellent reservoir properties makes the studied reservoir horizon an attractive target for geothermal development. Our results are applicable to other geothermal systems in strike-slip settings across Central Asia, and potentially worldwide.

Palynological analysis (biochronostratigraphy and paleoenvironments) from a fossil-Lagerstätte section within the Late Paleozoic Ice Age unit of the Paraná Basin (Itararé Group), Western Gondwana

A diverse and exceptionally preserved fossil association occurs in Campáleo Outcrop black shales of the upper Itararé Group, correlated to the Lontras Member, considered representative of the Pennsylvanian–Permian transition in the Paraná Basin, Brazil. In this paper, we present the palynological records from 20 stratigraphic horizons of these shales and related strata, which revealed 21 taxa of spores, 33 of pollen grains, two species of fungi, one species of Chlorophyceae and two species of Prasinophyceae. The section is correlated to the Vittatina costabilis Zone, due to the records of certain guide species, such as Converrucosisporites confluens, Illinites unicus and several species of Vittatina. An additional subsurface section (TC-4 core) partially correlated with the Campáleo Outcrop and comprising the passage of the Crucisaccites monoletus and Vittatina costabilis palynozones was also studied in order to support the stratigraphic positioning. Once combined with the stratigraphic positioning in the basal portion to the Lontras Shale, it allows us to consider it around the Pennsylvanian–Permian boundary, probably in the Gzhelian to age of the Campáleo Outcrop. We observed distinct palynofloristic compositions from (i) the rhythmic shale with dropstones (basal portion) and from (ii) the fossiliferous black shales (upper portion). The former presents a large dominance (about 90 %) of pollen grains (xerophylous elements) and low frequency (about 7 %) of spores (meso-hygrophylous), while the results of the latter are conversely. Marine palynormorphs were recorded herein only from the rhythmic shale. The palynological assemblages on the base of the Campáleo Outcrop demonstrated a more intense sediment supply, bringing sporomorphs from more distant regions being represented mainly by xerophylic flora, indicating the existence of regions devoid of ice cover, where forests could develop, as occur in seasonal climate regions. The upper level of the Campáleo Outcrop characterizes one of the predominance of spores (hygrophylic communities) in these palynological associations supported by the large number of insects found that indicates proximity to the coastline, little transport (spore tetrads), poor contribution of more distant continental sediments (low expressiveness of pollen grains) and low salinity water, due to the absence of marine palynomorphs, representing a reducing restricted marine environment. This data integrated with the stratigraphic context and other geological data evidenced changes in sea level due to the climatic oscillations in the course of the LPIA that influenced the sediment supply and the distance of the coastline in this region of the Paraná Basin.

Adaptation of Ulva lactuca in low-salinity and high-nutrient water environment and its synergistic microbial effect on inorganic nitrogen removal

Adaptation of Ulva lactuca in low-salinity and high-nutrient water environment and its synergistic microbial effect on inorganic nitrogen removal

Humic acids as complexing agents to drive photo-Fenton at mild pH in saline matrices: Process performance and mechanistic studies

The role of iron complexation on (photo)-Fenton process at mild pH has been investigated; in particular, the effect of humic acids, their interaction with chlorides and the involvement of the target pollutants has been studied. For this purpose, solutions consisting in mixture of 6 pollutants (acetaminophen, acetamiprid, amoxicillin, caffeine, carbamazepine and clofibric acid) in different matrices ( a) distilled water, b) low salinity water (1 g·L−1 of Cl-), c) high salinity water (30 g·L−1 of Cl-), d) tap water and e) real sea water) have been irradiated with simulated sunlight with and without humic acids (10 mg L−1). The ability of humic acids to complex Fe(III) resulted in an enhancement of pollutants removal as prevented iron inactivation, but in highly saline waters were they were not able to displace completely Cl- as ligands for Fe(III) and in sea water where other species could also contribute to inhibit photo-Fenton. Furthermore, pollutants with phenolic and/or carboxylic moieties also contribute to keep iron active at pH = 5, most probably by complexation. This is in line with dissolved iron at the end of the experiment and hydrogen peroxide consumption. Electron spin resonance measurements of ·OH show a very good correlation between the radical formation and pollutants removal, indicating that in the presence of complexing agents, generation of ·OH is favoured. These results indicate that HA could be used as auxiliary to apply photo-Fenton in low salinity environments rather than in real seawater.

A comprehensive evaluation of the effect of key parameters on the performance of DTPA chelating agent in modifying sandstone surface charge

Despite the positive aspects of low salinity water (LSW), this technique is relatively expensive and unavailable in some countries. Furthermore, potential problems associated with LSW such as scale precipitation in carbonate reservoirs and fine migration in sandstone reservoirs raise concerns. Chelating agents have the ability to chelate metal ions from solution, effectively reducing the salinity of seawater (SW) and mimicking the behavior of LSW. However, they mitigate the challenges associated with LSW injection. This study focuses on how the Diethylenetriaminepentaacetic acid (DTPA) chelating agent performs in modifying rock surface charge. The impact of concentration, brine salinity, potential determining ions (PDIs), oil presence, Fe3+ ions, and solution pH on the effectiveness of DTPA in altering rock surface charge was evaluated. Furthermore, wettability alteration and sand pack flooding tests were conducted to study the effect of DTPA on rock wettability and oil recovery. Results of wettability alteration, zeta potential, sand pack flooding experiments and ion concentration analysis are reported in this paper. The results showed that reducing salinity, increasing DTPA concentration, and raising solution pH changed rock wettability from oil-wetness towards water-wetness. The presence or absence of PDIs in the solution did not affect the performance of DTPA. However, by tripling the concentration of these ions in the solution, the performance of DTPA in changing rock surface charge was impaired. Based on the wettability alteration and zeta potential experiments, 5 wt% DTPA was determined as the optimum concentration. Subsequent flooding experiments revealed that injecting 5 wt% DTPA chelating agents into the sandstone sand pack after SW injection increased oil recovery from 48 % to 68.3 %. The analysis of ion concentrations also revealed a significant increase in the amount of calcium ions during the DTPA flooding, indicating the chelation of metal ions from both rock and solution and improving the wettability conditions.

Integrating major ion geochemistry, stable isotopes (18O, 2H) and radioactive isotopes (222Rn, 14C, 36Cl, 3H) to understand the interaction between catchment waters and an intermittent river

Determining the locations and sources of baseflow and the transit times of water is important for understanding catchment behaviour and functioning. Major ion geochemistry, stable isotopes (18O and 2H), and radioisotopes (222Rn, 3H, 14C, and 36Cl) were used to investigate the sources and transit times of water in the upper catchment of the intermittent Avoca River in southeast Australia. 222Rn activities and Cl concentrations implied the presence of baseflow inputs and the distribution was mainly controlled by local topography. Fluctuation of Cl concentrations implied that low-salinity near-river water was an important component of baseflow. The 3H activities of laterally disconnected pool waters during the summer months were 1.64 to 5.11 TU. The higher of these values exceed those of average annual rainfall (2.8–3.2 TU), probably due to the input of later winter to spring rainfall. The stream water had 3H activities ranging from 2.21 to 2.40 TU in July and 2.39 to 2.77 TU in August, which yield mean transit times of 4.0 to 7.0 years and 1.4 to 4.8 years respectively. These 3H activities were significantly higher than those of regional groundwater (3H activities <0.1 TU), implying that the river is largely sustained by young near-river stores at all flow conditions. Regional groundwater had 14C activities of 34.0 to 98.1 pMC, which yield mean residence times of up to 12,900 years. R36Cl values of regional groundwater (50.9–61.9 × 10−15) were higher than those of modern rainfall, probably reflecting the R36Cl values of recharge. Similar R36Cl values of the pool and stream water (33.3–58.7 × 10−15) implied that some Cl is derived from the regional groundwater influx. As with other intermittent streams in southeast Australia, the upper Avoca River was mainly sustained by relatively small water stores, and it will be vulnerable to short-term changes in climate and land use.

Biofilm formation and cell plasticity drive diazotrophy in an anoxygenic phototrophic bacterium.

The contribution of non-cyanobacterial diazotrophs (NCDs) to total N2 fixation in the marine water column is unknown, but their importance is likely constrained by the limited availability of dissolved organic matter and low O2 conditions. Light could support N2 fixation and growth by NCDs, yet no examples from bacterioplankton exist. In this study, we show that the phototrophic NCD, Rhodopseudomonas sp. BAL398, which is a member of the diazotrophic community in the surface waters of the Baltic Sea, can utilize light. Our study highlights the significance of biofilm formation for utilizing light and fixing N2 under oxic conditions and the role of cell plasticity in regulating these processes. Our findings have implications for the general understanding of the ecology and importance of NCDs in marine waters.

Interfacial Water-Dictated Oil Adhesion Based on Ion Modulation.

Oil adhesion on ionic surfaces is ubiquitous in organisms and natural environments and is generally determined by surface chemical component and texture. However, when adhesion occurs, water molecules at the solid-liquid interface, acting as a bridge not only influenced by the structure and composition of the solid surface but also interacting with the neighboring oil molecules, play a crucial role but are always overlooked. Herein, we investigate the oil adhesion process on a carboxyl-terminated self-assembled monolayer surface (COOH-SAM) in ionic solutions and observe the interfacial water structure via surface-enhanced Raman scattering (SERS) in this system. It is found that the lower the tetracoordinated water content, the stronger the oil adhesion. Compared to monovalent ions, the strengthened binding of multivalent ions to the COOH-SAM surface makes the interfacial water more disordered, which eventually leads to a stronger oil adhesion. Notably, the amount of oil adhesion decreases with an increase in the thickness of the interfacial water region. The interfacial water-dictated oil adhesion has been demonstrated in capillary to simulate the water-driven oil recovery, providing a molecular-level explanation for enhanced oil recovery from low salinity water flooding and also indicating potential applications in intelligent microfluidic and seawater desalination.

Experimental investigation of combined carbon nanoparticles (CNPs), ionic liquid (I.L), and low salinity water to enhance oil recovery (EOR) at Iraq's southern oil fields

By 2030, global energy demand is expected to increase by 50% with respect to 2020. However, supplies of natural gas and oil are steadily depleting. Therefore, implementing innovative enhanced oil recovery (EOR) technology in producing reservoirs is essential to meeting the growing energy demand.EOR is a technique that has currently been in use to increase the rate of oil production. This research demonstrates the novel opportunities of combining carbon nanoparticles, ionic liquid surfactant (dodecyl pyridinium chloride), and low-salinity water to improve oil recovery from carbonate reservoirs. A series of experimental works, comprising sedimentation technique, zeta potential analysis, contact angle measurements, and surface tension tests, were conducted to study the stability and choose the optimal nanofluid for application in EOR.It was discovered that by adding various concentrations of an ionic liquid to a 50 ppm nanocarbon solution, the density of the nanofluid formulations could be slightly reduced, the surface tension could be changed, and the wettability of carbonate rocks could be altered from an oil-wet to a water-wet system. Core-flooding tests were carried out for optimum nanofluid formulation (50 ppm of nanocarbon with 250 ppm of ionic liquid) at different flow rates. Additional oil recoveries of 8.46 % and 20.5 % of the original oil in place were achieved at flow rates of 0.667 cm3/min and 0.334 cm3/min, respectively. This study is one of the first to be conducted in Iraq's oil fields to investigate the potential for EOR using carbon nanoparticles, ionic liquid, and low-salinity water. The results of this research highlight the potential of hybrid nanofluids as a new type of injection fluid for EOR.

Discovery, geological setting and mineralization of the Shuvuutai molybdenum deposit, central-southern Mongolia

We document the newly discovered Shuvuutai Molybdenum (Mo) porphyry deposit located in the central-east Mongolian volcanic/-plutonic belt of the southern Altaids. The deposit is characterized by quartz vein- and veinlet-disseminated-type Mo ore bodies mainly hosted in a Late Permian-Early Triassic granitic intrusion. In this study, we provide a detailed study that integrates detailed geology with petrographic, mineralogic, geochemical, and geochronologic date to determine the tectonic setting of the deposit. Fluid inclusion analysis is used to reconstruct the fluid evolution history of the Shuvuutai Mo mineralization system and to understand the origin of the deposit. The ore bodies occur mainly as veins, lenses, and pods in positions from inner intrusions through contact zones to the host rocks distal to causative intrusions. The host rocks are variable in lithology, including granites, porphyries, volcanic breccias and tuffs, and sedimentary rocks. Outward from ore bodies to host rocks, the wall rock alteration is zoned from potassic (K-feldspar-quartz-mica), through phyllic (quartz-sericite-chlorite-epidote), to propylitic or argillic alterations. Two samples from porphyry stock intrusions at Shuvuutai were selected for U–Pb zircon geochronology and trace element composition studies, including the ore-hosting monzodiorite porphyry and quartz syenite porphyry. Our new ages are consistent with, or slightly postdate published zircon U-Pb ages of early phase of monzodiorite porphyry (268–232 Ma) and the main phase of quartz syenite porphyry (251.6 ± 1.7 Ma). Hydrothermal mineralization generally includes four stages, from early to late, represented by (1) potassic feldspar-quartz veins or veinlets, (2) quartz-molybdenite stockworks, (3) quartz-sulfide stockworks, and (4) quartz ± carbonate veins or veinlets. The ore-forming fluids were initially magmatic in origin and show high-temperature and high-salinity, containing daughter mineral and CO2-bearing fluid inclusions; and eventually evolved to low-temperature, low-pressure, low-salinity and CO2-poor meteoric water. S isotopic compositions of sulfides from the Shuvuutai Mo porphyry deposit indicate that the source of the ore-forming material was derived from the felsic magma. The Central-Eastern Mongolian volcanic-plutonic belt continues from Mongolia into northeast China, where similar Mo deposits are not yet recognized, suggesting that a new exploration strategy, based on the characteristics and history of the Shuvuutai discovery, is needed for the Chinese segment of the Altaids.

Simulation study of affecting parameters during low salinity water injection in carbonate reservoirs: from core to field scale

Over the last decade, economic and environmental factors have led to low salinity water injection (LSWI) becoming one of the most important improved oil recovery methods. Although many results have been obtained from laboratory tests, only a few papers have been published regarding the modeling and simulating LSWI in carbonate reservoirs compared to sandstone reservoirs. This paper investigated the most affecting parameters on oil recovery during LSWI at the core and field scale. The published work focused more on the effective parameters related to ultimate oil recovery using LSWI. However, important parameters affecting the oil recovery rate were not investigated. We compared how important parameters affected the ultimate oil recovery factor and ultimate oil recovery rate. According to the results of this study, the salinity of injected water and curvature of oil relative permeability were the most important factors on the ultimate oil recovery factor. By reducing both of these parameters, more increment oil was recovered. By increasing the injection rate of water, the curvature of the water relative permeability, wettability, and the endpoint of oil relative permeability, the oil recovery rate also increased. Furthermore, threshold capillary pressure and the endpoint of relative permeability of water had inverse effects on oil recovery. Injecting low salinity water into the reservoir will change its wettability. As a result, it will change the properties of the reservoir and increase the production from the reservoir, resulting in more oil being produced. LSWI resulted in an increase of oil recovery factor of 5% and 11% respectively after 25 and 58 years in this case.

Metagenomic and Culture-Based Analyses of Microbial Communities from Petroleum Reservoirs with High-Salinity Formation Water, and Their Biotechnological Potential.

The reserves of light conditional oil in reservoirs with low-salinity formation water are decreasing worldwide, necessitating the extraction of heavy oil from petroleum reservoirs with high-salinity formation water. As the first stage of defining the microbial-enhanced oil recovery (MEOR) strategies for depleted petroleum reservoirs, microbial community composition was studied for petroleum reservoirs with high-salinity formation water located in Tatarstan (Russia) using metagenomic and culture-based approaches. Bacteria of the phyla Desulfobacterota, Halanaerobiaeota, Sinergistota, Pseudomonadota, and Bacillota were revealed using 16S rRNA-based high-throughput sequencing in halophilic microbial communities. Sulfidogenic bacteria predominated in the studied oil fields. The 75 metagenome-assembled genomes (MAGs) of prokaryotes reconstructed from water samples were assigned to 16 bacterial phyla, including Desulfobacterota, Bacillota, Pseudomonadota, Thermotogota, Actinobacteriota, Spirochaetota, and Patescibacteria, and to archaea of the phylum Halobacteriota (genus Methanohalophilus). Results of metagenomic analyses were supported by the isolation of 20 pure cultures of the genera Desulfoplanes, Halanaerobium, Geotoga, Sphaerochaeta, Tangfeifania, and Bacillus. The isolated halophilic fermentative bacteria produced oil-displacing metabolites (lower fatty acids, alcohols, and gases) from sugar-containing and proteinaceous substrates, which testify their potential for MEOR. However, organic substrates stimulated the growth of sulfidogenic bacteria, in addition to fermenters. Methods for enhanced oil recovery should therefore be developed, combining the production of oil-displacing compounds with fermentative bacteria and the suppression of sulfidogenesis.