Reduction Of Water Salinity Research Articles

Insights into the pore-scale mechanism of low salinity water injection using a clay-coated micromodel

This study aims to provide new insights into the interactions among an acidic crude-oil, brine with different salinities and clay using flow experiments in montmorillonite-coated micromodels. To this end, a series of oil-displacement experiments are performed in a transparent clay – coated micromodel. In addition, salinity-screening tests, pH and IFT measurements are performed to support the results of flow-experiments. It is shown that during water injection into a clay-coated micromodel, polar components of crude oil partition between oil/water phases and form an emulsified phase. With the 90% reduction in water salinity, the partitioning of crude oil polar components in the aqueous phase is increased. Such partitioning lead to a significant reduction in the pH of the aqueous phase. This observation is supported by an increase in the IFT of oil/brine due to the decrease of crude oil polar components. Salinity screening tests show that there is a critical water salinity, i.e., below the critical point, a large amount of crude oil polar components is partitioned between phases, which can be attributed to the polarization effect. Overall, results show that low salinity water injection benefits from formation of an emulsified phase and wettability alteration to improve oil recovery in the microscale.

Impact of Low Salinity Water Injection on CO2 Storage and Oil Recovery for Improved CO2 Utilization

CO2 utilization for oil recovery applications is often impacted by the challenges such as viscous fingering and its premature breakthrough. Injection of slugs of water-alternating-gas (WAG) generally aims to overcome these challenges though the control of CO2 mobility. Moreover, the oil recovery potential of WAG is largely dependent on the injection water salinity and the subsequent CO2 dissolution and storage. Therefore, the effect of varying salinity (0–4 wt% NaCl) on CO2 loading capacity of water is investigated in this study, at two test temperatures of 323 K and 363 K and three confining pressures of 4, 8, and 12 bar, and subsequently, the flooding experiments were performed to find the low salinity (LS)-WAG process suitability in oil recovery applications from porous sandstone rocks. The inclusion of salt was found to significantly affect CO2 loading capacity of water. At higher NaCl concentration (4 wt%), CO2 loading decreased by 50% as demonstrated by absorption kinetic study. LS-WAG suggested maximum oil recovery 55–58% of original oil in place for water salinity of 2 wt% NaCl at both the test temperatures. Increment in pressure had a positive impact on CO2 loading while increasing temperature showed reverse behavior. As a result of LS in WAG and kinetic adsorption study, it is anticipated that the reduction in water salinity is a favorable factor in the CO2 storage and oil recovery performance of CO2 injection. The instance of CO2 injection was also varied for LS-WAG process and its effect on oil recovery from sand-packs was reported. Oil recovery results demonstrated that WAG was similarly effective in all the stages of the injection cycle as long as water salinity remained lower than 2 wt% NaCl. Based on the findings in this study, it is recommended to implement the WAG in conjunction with low salinity water (LSW) in moderate saline conditions, which is of key importance for various applications where water salinity differs on a large scale.

Subtropical mangrove wetland is a stronger carbon dioxide sink in the dry than wet seasons

Coastal mangrove wetlands have an excellent potential in sequestrating atmospheric carbon dioxide (CO2) owing to their high primary productivity as well as slow anaerobic decomposition of organic matter. Yet, there is hitherto a paucity of researches examining the temporal variations and environmental controls of ecosystem-scale CO2 fluxes in subtropical mangroves using quasi-continuous, high temporal resolution measurements. In this study, we measured the net ecosystem CO2 exchange (NEE) between the atmosphere and a subtropical estuarine mangrove dominated by Kandelia obovata using an eddy covariance system for two full years to investigate the seasonal variability and key biophysical drivers of NEE. During the wet seasons, the magnitude of increase in ecosystem respiration (Re) was greater than that in gross primary productivity (GPP) owing to a combination of higher temperature and lower percentage of inundation, tidal height and water salinity, which subsequently resulted in an overall decrease in net CO2 uptake as compared to the dry seasons. Our results of path analysis showed that temperature was a dominant control of the temporal variations in CO2 flux during the wet seasons, while its influence became weaker during the dry seasons. On the other hand, an increase in water salinity during the dry seasons had a positive influence on GPP, which was likely related to a greater availability of ions (mainly Cl− and Na+) in supporting photosynthesis by mangrove trees in this coastal wetland with relatively low salinity (∼5–15 ppt). Our subtropical mangrove wetland was shown to be a significant carbon (C) sink, with annual C uptake rates of 890 and 758 g CO2-C m-2 yr−1 in the two years of study. We found a strong control of mangrove CO2 fluxes by biophysical factors such as temperature and salinity, implying that global warming and a reduction in water salinity in response to a greater river discharge could potentially reduce the C sink strength of estuarine mangroves in the subtropical regions.

Oxygen Exchange and Primary Production of Zostera japonica Ascherson et Graebner 1907 Community in the Golubinyi Bay (Sea of Japan)

The net primary production per daylight period (Pn, dl) and dark respiration per day (Rd) of the eelgrass Zostera japonica community were measured in situ by the continuous-flow-system method in the Golubinyi Bay (Sea of Japan) in May–June 2008–2012; the obtained values were Pn = 3.37 g О2/(m2 dl) and Rd = 7.21 g О2/(m2 d). The photosynthesis rate of Z. japonica depended on the intensity of photosynthetically active radiation (PAR) and salinity. The gross primary production (Pg) of the Z. japonica community was 6.98 g О2/(m2 d) or 2.62 g С/(m2 d) at the salinity of 34–17‰. With reduction of water salinity to 8–1‰, the Pg of the Z. japonica community decreased to 2.17 g O2/(m2 d) or 0.81 g C/(m2 d), because of a lower rate of photosynthesis in plants. The primary production of Z. japonica was 6.10 g O2/(m2 d) or 87.4% of the gross production of the community. The ratio of gross production to dark respiration (Pg/R) was approximately 1.0, indicating the balance of autotrophic and heterotrophic processes in the community.

Amyloodiniosis in cultured Dicentrarchus labrax: parasitological and molecular diagnosis, and an improved treatment protocol

Amyloodinium ocellatum, the causative agent of amyloodiniosis (marine velvet, velvet disease), affects marine and brackish fish in various warm and temperate habitats. We recorded disease outbreaks with high morbidity and mortality rates in marine-cultured European seabass Dicentrarchus labrax fry at 2 locations in northwest Egypt. The sudden outbreak, high morbidity and mortality rates, and skin lesions with a velvety appearance in affected fish all indicated A. ocellatum infection. This was further confirmed by microscopic findings of the parasitic stage (trophonts) in skin and gill smears. While ecological factors including water temperature and salinity were all amenable to parasite establishment and propagation, mortality rates differed between the 2 farms, with rates of mortality well correlated with prevalence and intensity of A. ocellatum infections. Characterization by PCR targeting rDNA gene fragments and subsequent DNA sequencing and phylogenetic analysis further confirmed the molecular identity of the A. ocellatum isolate, which was genetically similar to isolates from other geographical locations. Finally, an improved treatment method using dual hyposalination and copper sulfate exposure to increase the efficiency and decrease the toxicity of copper sulfate was tested. The gradual reduction in water salinity coupled with copper sulfate treatment was more efficient at controlling the disease than only applying copper sulfate. To our knowledge, this is the first parasitological and molecular characterization of A. ocellatum in marine cultures in Egypt. The high molecular identity and close phylogenetic relationship further confirmed the monophyletic nature of A. ocellatum isolates.

A Pore-Scale Investigation of Low-Salinity Waterflooding in Porous Media: Uniformly Wetted Systems

The potential of low-salinity (LS) water injection as an oil recovery technique has been the source of much recent debate within the petroleum industry. Evidence from both laboratory and field-level studies has indicated significant benefits compared to conventional high-salinity (HS) waterflooding, but many conflicting results have also been reported and, to date, the underlying mechanisms remain poorly understood. In this paper, we aim to address this uncertainty by developing a novel, steady-state pore network model in which LS brine displaces oil from a HS-bearing network. The model allows systematic investigation of the crude oil/brine/rock parameter space, with the goal of identifying features that may be critical to the production of incremental oil following LS brine injection. By coupling the displacement model to a salinity-tracking tracer algorithm, and assuming that a reduction of water salinity within the pore network leads to localised wettability alteration, substantial perturbations to standard pore filling sequences are predicted. The results clearly point to two principal effects of dynamic contact angle modification at the pore scale: a “pore sequence” effect, characterised by an alteration to the distribution of displaced pore sizes, and a “sweep efficiency” effect, demonstrated by a change in the overall fraction of pores invaded. Our study indicates that any LS effect will depend on the relative (scenario-dependent) influence of each mechanism, where factors such as the initial wettability state of the system and the pore size distribution of the underlying network are found to play crucial roles. In addition, we highlight the important role played by end-point capillary pressure in determining LS efficacy.

A new process for the capture of CO2 and reduction of water salinity

The present work evaluates a new process for the capture of CO2 and the reduction of water salinity. It is based on the Solvay process without the use of ammonia and involves the reaction of CO2 with saline water such as reject brine in the presence of calcium hydroxide. The effects of operating parameters such as reaction temperature, water pH and reaction stoichiometry on CO2 capture efficiency and sodium removal were examined for both traditional and modified Solvay process. The optimum conditions for maximum CO2 capture efficiency and sodium removal were determined using response surface methodology and were found to be at temperature of 20°C and a pH of greater than 10 for both processes. At the optimum conditions, CO2 capture of 86% and 99% and sodium removal of 29% and 35% were achieved for the traditional Solvay and the Modified process, respectively. The water pH was found to be a key parameter in the effectiveness of the reaction process; higher pH leads to better process performance in both CO2 capture efficiency and sodium removal. The experimental results clearly illustrated that the Modified Solvay process is superior in terms of CO2 capture efficiency, sodium removal and energy consumption.

Using high- and low-salinity seawater injection to maintain the oil reservoir pressure without damage

The oil reservoir pressure declines due to oil production, and this decline will lead to reduction in the oil productivity. The reservoir pressure maintenance is a practice in the oil industry in which seawater is injected into the aquifer zone below the oil zone to support the reservoir pressure. Calcium sulfate scale is one of the most serious oilfield problems that could be formed in sandstone and carbonate reservoirs. Calcium sulfate may precipitate during the injection of seawater with high sulfate content into formation brine with high calcium content. Mixing seawater and formation water may cause precipitation of calcium sulfate, barium sulfate, and/or strontium sulfate. Seawater treatment does not remove the entire sulfate ions from the injected water. Low sulfate concentrations may cause damage. Enhanced oil recovery processes such as smart water injection, which originally is diluted seawater, may cause calcium sulfate precipitation as the reduction of water salinity will increase the sulfate precipitation and decrease its solubility. This study was conducted to investigate the damage caused by the deposition of calcium sulfate precipitation. A solution is proposed to prevent the damage due to calcium sulfate by using chelating agents. Several coreflooding experiments were conducted using Berea sandstone and Indiana limestone cores at reservoir conditions of pressure and temperature using seawater (high and low salinity) and formation water. Chelating agents used in this study are: EDTA (ethylenediaminetetraacetic acid), HEDTA (hydroxyethylenediaminetriacetic acid), and HEIDA (hydroxyethyliminodiacetic acid). HEDTA and HEIDA chelating gents are environmentally friendly and can be used in marine environment. High-salinity water injection caused severe formation damage, and the injectivity will decline faster compared to the low-salinity water injection. HEDTA and EDTA chelating agents at low concentrations performed better than HEIDA chelating agents in both Berea sandstone and Indiana limestone cores. HEDTA and EDTA chelating agents were able to prevent the damage due to calcium sulfate precipitation and enhanced the core permeability.

Treatments of reverse osmosis concentrate using natural zeolites

Abstract The purpose of the current study is to experimentally investigate the reduction of sodium adsorption ratio (SAR) from a concentrated stream of reversed osmosis (RO) using natural zeolites. In order to reduce the salinity of solution, experiments were carried out using zeolites of varying concentration, pretreatment of adsorbents, and the addition of Ethylenediaminetetraacetic acid (EDTA). The results show that both zeolites can be used in an RO brine treatment; however, Rhyolitic tuff is more effective than clinoptilolite for the reduction of water salinity. The experiments show that Rhyolitic tuff decreases salinity of RO concentrate to nearly one – third of the initial value. Statistical analyses show that the effect of zeolite concentration is negligible. Furthermore, the addition of EDTA and pretreatment of zeolite increase the SAR values.

Effect of Reduction in Water Salinity on Osmoregulation and Survival of Large Atlantic Salmon Held at High Water Temperature

AbstractWe examined the possible ameliorating effects of reduced salinity (28‰) on the physiological performance of large Atlantic salmon Salmo salar initially reared at 35‰ and exhibiting osmo‐ionoregulatory disturbances in high seasonal water temperatures (>18°C). Considerable differences were observed in the behavior, survival, and plasma values for cortisol, osmolality, and chloride after 3 d, with fish from the 28‰ salinity regime approaching basal levels (cortisol: 8.0 ± 1.7 mmol/L; osmolality: 374.3 ± 6.8 milliosmols per kilogram [mosmols/kg]; [Cl‐]: 170.5 ± 3.8 mmol/L [mean ± SE]) and fish from full‐strength seawater showing a further decrease in osmoregulatory capacity (cortisol: 33.7 ± 5.0 mmol/L; osmolality: 411.4 ± 9.7 mosmols/kg; [Cl‐]: 189.1 ± 6.8 mmol/L). Two weeks later, fish kept at 28‰ still had a normal osmoregulatory capacity and exhibited a significant increase in condition factor, whereas many fish (70%) in full‐strength seawater had died. These results indicate a limited capacity for maintaining osmo‐ionoregulatory homeostasis in full‐strength seawater during long periods at high temperature. Access to water of lower salinity appears to be essential for the survival of Atlantic salmon in this environment.

Whole-body corticosteroid and plasma cortisol concentrations in larval and juvenile Atlantic cod Gadus morhua L. following acute stress

Methods were developed to assess whole-body immunoreactive corticosteroid concentrations (IRC) and plasma levels of cortisol in Atlantic cod subjected to several common, acute stressors. A measurable corticosteroid stress response was observed at the first sampling in whole bodies of 8-day post-hatch (dph) larvae. Two groups of juveniles (∼5 and 30 g) were subjected to a 30 s net stressor and whole-body IRC and plasma cortisol levels were determined. Post-stressor IRC in smaller fish rose approximately 14-fold, peaked at 1 h, were sustained for 3–6 h and returned to pre-stressor levels within 24 h. Post-stressor plasma cortisol levels in larger fish rose approximately 18-fold, peaked at 0.5–1 h, were sustained for 1–3 h and then returned to near pre-stressor levels after 24 h. Immunoreactive corticosteroid concentrations appeared to remain elevated longer than plasma cortisol levels suggesting that steroids other than cortisol were contributing to total immunoreactivity in homogenates. Juveniles exposed to either a grading procedure or high density transport had maximal IRC and plasma cortisol levels within 90 min which returned to pre-stressor levels within 24–72 h. A reduction in water salinity (20 g L−1) did not moderate the corticosteroid response in juveniles. The results show that Atlantic cod respond to common, acute stressors in a manner similar to other teleosts. Whole-body homogenates can be used to identify changes in IRC in response to acute stress in cod with the caveat that recovery IRC may differ from plasma cortisol concentrations.