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.

Three-dimensional structure of a low salinity tongue in the southern Taiwan Strait observed in the summer of 2005

Cruise observations with CTD （conductivity-temperature-depth） profiler were carried out in the southern Taiwan Strait in the summer of 2005. Using the cruise data, two-dimensional maps of salinity and temperature distributions at depths of 5, 10, 15, 20, and 30 m were generated. The maps show a low salinity tongue sandwiched by low temperature and high salinity waters on the shallow water side and high temperature and high salinity waters on the deep water side. The further analysis indicates that the low salinity water has a nature of river-diluted water. A possible source of the diluted water is the Zhujiang （Pearl） Estuary. Meanwhile, the summer monsoon is judged as a possible driving force for this northeastward jet-like current. The coastal upwelling and the South China Sea Warm Current confine the low salinity water to flow along the central line of the strait. Previous investigations and a numerical model are used to verify that the upstream of the low salinity current is the Zhujiang Estuary. Thus, the low salinity tongue is produced by four major elements： Zhujinag Estuary diluted water, monsoon wind driving, coastal upwelling and South China Sea Warm Current modifications.

Enhanced oil recovery from carbonate reservoirs by spontaneous imbibition of low salinity water

An experimental study was performed to investigate the impact of low salinity water on wettability alteration in carbonate core samples from southern Iranian reservoirs by spontaneous imbibition. In this paper, the effect of temperature, salinity,permeability and connate water were investigated by comparing the produced hydrocarbon curves. Contact angle measurements were taken to confirm the alteration of surface wettability of porous media. Oil recovery was enhanced by increasing the dilution ratio of sea water, and there existed an optimum dilution ratio at which the highest oil recovery was achieved. In addition, temperature had a very significant impact on oil recovery from carbonate rocks. Furthermore, oil recovery from a spontaneous imbibition process was directly proportional to the permeability of the core samples. The presence of connate water saturation inside the porous media facilitated oil production significantly. Also, the oil recovery from porous media was highly dependent on ion repulsion/attraction activity of the rock surface which directly impacts on the wettability conditions. Finally, the highest ion attraction percentage was measured for sodium while there was no significant change in pH for all experiments.

Numerical Simulation and Dynamical Analysis for Low Salinity Water Lens in the Expansion Area of the Changjiang Diluted Water

The low salinity water lenses（LSWLes） in the expansion area of the Changjiang diluted water（CDW） exist in a certain period of time in some years. The impact of realistic river runoff, ocean currents and weather conditions need to be taken into account in the dynamical analysis of LSWL, which is in need of research. In this paper, the POM-σ-z model is used to set up the numerical model for the expansion of the CDW. Then LSWL in summer 1977 is simulated, and its dynamic mechanism driven by wind, tide, river runoff and the Taiwan Warm Current is also analyzed. The simulated results indicate that the isolated LSWL detaches itself from the CDW near the river mouth, and then moves towards the northeast region outside the Changjiang Estuary. Its maintaining period is from July 26 to August 11. Its formation and development is mainly driven by two factors. One is the strong southeasterly wind lasting for ten days. The other is the vertical tidal mixing during the transition from neap tide to spring tide.

Digging out molecular markers associated with low salinity tolerance of Nannochloropsis oceanica through bulked mutant analysis

Nannochloropsis oceanica is a marine microalgal species with both economic value and biological importance.It grows fast,contains rich oils,reproduces asexually,holds a small and haploidy genome,and is easy to be modified genetically.However,the genetic study of N.oceanica is scarce.Very less genetic bases of its traits have been deciphered,and no gene has been isolated from it with the function verified simultaneously via either genetic or reverse genetic approaches or both(de novo cloned).Changing medium salinity may aid to control harmful organisms met during large scale cultivation.As a stress,it may also facilitate the accumulation of desirable chemicals including fatty acids.In order to decipher the genetic basis of the low salinity tolerance of N.oceanica,we mutated N.oceanica with Zeocin.In total,five mutant bulks were constructed at equal number of cells,100 mutants each,which were tolerant to a discontinuous serial of salinities from that of 100%of f/2 to that of a mixture of 4%of f/2 and 94%of BG11.The bulks were genotyped through whole genome re-sequencing and analyzed with bulked mutant analysis(BMA)newly modified from bulked segregant analysis(BSA).In total,47 SNPs and 112 InDels were found to associate with the low salinity tolerance,and around them a set of low salinity tolerance associating genes were identified.A set of annotatable genes commonly found between control and different salinities indicated that the genes functioning in gene expression,energy metabolism and cellular structure may be involved in the low salinity tolerance.These associating molecular markers and genes around them were not enough for outlining the physiological mechanism underlining the tolerance;however they should aid to improve N.oceanica genetically.

Effects of Ionic Concentrations on Survival and Growth in Polyculture of Litopenaeus vannamei with Oreochromis niloticus in Low Salinity Water

A study comparative of rearing of the Pacific white shrimp （Litopenaeus vannamei） with the Nile tilapia （Oreochromis niloticus） in three earthen ponds （5,600 m^2） with the salinity ranged from 0.5-1.2 ppt and three treatment ponds with salinity of 2-4 ppt by adding brine water into the ponds. Postlarvae 12 （PL12） of L. vannamei were stocked at density of 9 PL/m^2 and after one week the Nile tilapia fingerlings were stocked at density of I fish/m^2. Only pelleted feed were given to the fish during the 196-day rearing period. Shrimps were partially harvested by sieve net at day 80 and 120, and five days later PLI2 were stocked at the rate of 3 PL/m^2. After final harvesting at day 196, the production, body weight and survival from the treatment group were significantly higher （P 〈 0.05） than those of the control group. While the fish production body weight and survival rate from both groups were not significant differences （P 〉 0.051）. The ionic concentration of six major ions （CI, SO42, Ca^2＋, Na^＋, Mg^2＋ and K^＋）, salinity and hardness in the treatment ponds were significantly higher than those of the control ponds （P 〈 0.05）. Moreover, the ionic profiles of the treatment ponds were similar to seawater at the salinity of 2 ppt while only 1 ppt in the control ponds. Results from the study indicated that in order to achieve good growth and survival rate of L. vannamei, brine water should be added into grow-out ponds prior to stocking and during the rearing： period to obtain and maintain the salinity not less than 2 ppt.

The Impact of Core Firing on EOR of Low Salinity-Surfactant Flooding

The combination of injection of lower saline brine and surfactant will increase recovery in sandstone rocks than either when any of the techniques is singly applied. In this work, core IFT test, pH test, flooding experiments and measurement of dispersion were performed on four core samples which were grouped into two: group A which were not fired and group B which were fired at a temperature of 500°C for 24 hours. Two low saline brines were prepared: LS1 which was derived by the dilution of seawater four times and LS2 which was derived by ten times diluting the seawater. The surfactant used was ethoxylated alcohol surfactant. Coreflood experiments were then performed on the rock samples starting with the injection of low saline followed by low saline brine combined with surfactant (LSS). Results from the experiments show that with the injection of LS1 brine and LSS1 higher increment in recoveries were obtained for group B than for group A cores. The same trend was also noticed with the injection of LS2 and LSS2. From the results, LS1 gave higher increment in oil recovery than LS2. Also LSS1 gave higher recoveries when compared with LSS2. In all the cases tested, core samples which were fired gave higher recoveries even though they had low permeabilities of 993 md for sample 3 and 1017 md for sample 4 than those which were not fired with higher permeabilities of 1050 md and 1055 md for samples 1 and 2 respectively. This was attributed to the alteration of wettability as well as that of permeability caused by sample firing. The dispersion profiles of the rock samples show that all samples are homogeneous.

A critical review of carbonate reservoir wettability modification during low salinity waterflooding

The nature of carbonate reservoirs promotes the adsorption of oil onto the rock surface hence making oil recovery a challenge even with the interventions of varied chemical EOR methods.Recently,low salinity water flooding has become of great interest since it is cost-effective and environmentally friendly.Although low salinity waterflooding has been highly investigated in sandstone reservoirs,it is not the same for carbonate reservoirs due to its complexities.Nonetheless,it has been proposed as a favourable technique to mobilise the trapped oil in carbonate reservoirs.Wettability alteration is regarded as the most accepted mechanism for low salinity flooding but has not been well understood making field scale applications doubtful.In this paper,we present a detailed review of the wettability alteration mechanisms in carbonate reservoirs during low salinity waterflooding.Parameters influencing wettability alteration in carbonates and the interactions that occur at the rock/brine/oil interface are also presented.The different methods utilised for wettability measurements during low salinity waterflooding are also reviewed including their drawbacks and advantages and recommendations.This will provide an improved understanding of the low salinity flooding application in carbonate reservoirs.

A review on the mechanisms of low salinity water/surfactant/nanoparticles and the potential synergistic application for c-EOR

Chemical enhanced oil recovery(c-EOR)is a conventional and promising strategy to recover oil from reservoir techniques such as low salinity water flooding(LSWF),surfactant flooding,alkaline flooding,polymers flooding,and nanofluid flooding.The use of various types of chemical materials for c-EOR method has recently attracted the attention of the oil and gas industry.The primary objective of this review work is to explore the synergy of low salinity water/surfactant/nanoparticle flooding for effective c-EOR method and investigate the mechanism behind these methods.The advantages of combining these chemical materials for c-EOR methods is also reviewed.Challenges and limitations of this synergy and their economic feasibility for additional oil recovery and potential return on investment are reviewed.Nanoparticles have been successfully used in various applications in several industries and have also shown good application for EOR in terms of wettability alteration.LSWF contributes to wettability alteration,while surfactant contributes to wettability alteration and interfacial tension(IFT)reduction.However,fines migration caused by LSWF and nanoparticle agglomeration can cause formation damage,while excessive surfactant adsorption can lead to cost overrun on surfactant use.Understanding the characteristics of reservoir formation mineralogy and appropriate nanoparticle type,size,and concentration can be used to resolve this challenges.The synergy of LSWF and nanoparticles in alkaline medium can serve as sacrificial agent to reduce excessive surfactant loss.Therefore,the appropriate synergistic formulation of LSFW/surfactant/nanoparticle can improve additional oil recovery and support return on investment for c-EOR projects.

Evaluation of sour gas-low salinity waterflooding in carbonate reservoirs-A numerical simulation approach

Although significant amount of H_(2)S(sour gas)rich natural gas is estimated globally,but not much attention has been given to the application of H_(2)S in the oil recovery process.Recent studies on the use of H_(2)S in oil recovery processes showed that H_(2)S has the potential of improving the oil recovery,and it can be even more effective than using CO_(2) in some processes.H_(2)S can equally dissolve in the water,react with the reservoir rock to change its surface charge,porosity,and permeability.However,previous in-vestigations on H_(2)S oil recovery attributed the improved oil recoveries to the higher miscibility of H_(2)S in the oil,and the reduction in the oil viscosity.Therefore,there is limited understanding on the H_(2)S-oil-brine-rock geochemical interactions,and how they impact the oil recovery process.This study aims to investigate the interactions between H_(2)S,oil,and carbonate formations,and to assess how the combi-nation of H_(2)S and low salinity water can impact the wettability and porosity of the reservoirs.A triple layer surface complexation model was used to understand the influence of key parameters(e.g.,pressure,brine salinity,and composition)on the H_(2)S-brine-oil-rock interactions.Moreover,the effects of mineral content of the carbonate rock on H_(2)S interactions were studied.Thereafter,the results of the H_(2)S-oil-brine-rock interactions were compared with a study where CO_(2) was used as the injected gas.Results of the study showed that the seawater and its diluted forms yielded identicalζ-potential values of about 3.31 mV at a pH of 3.24.This indicates that at very low pH condition,pH controls the ζ-potential of the oil-brine interface regardless of the brine's ionic strength.The study further demonstrated that the presence of other minerals in the carbonate rock greatly reduced the calcite dissolution.For instance,the calcite dissolution was reduced by 4.5%when anhydrite mineral was present in the carbonate rock.Findings from the simulation also indicated that CO_(2) produced negative ζ-potential values for the car-bonate rocks,and these values were reduced by 18.4%-20% when H_(2)S was used as the gas phase.This implies that the H_(2)S shifted the carbonate rockζ-potentials towards positive.The outcomes of this study can be applied when designing CO_(2) flooding and CO_(2) storage where the gas stream contains H_(2)S gas since H_(2)S greatly influences the dissolution of the carbonate mineral.

Low-salinity-based enhanced oil recovery literature review and associated screening criteria

A thorough literature review is conducted that pertains to low-salinity-based enhanced oil recovery(EOR).This is meant to be a comprehensive review of all the refereed published papers,conference papers,master’s theses and other reports in this area.The review is specifically focused on establishing various relations/characteristics or"screening criteria"such as:(1)classification/grouping of clays that have shown or are amenable to low-salinity benefits;(2)clay types vs.range of residual oil saturations;(3)API gravity and down hole oil viscosity range that is amenable for low salinity;(4)salinity range for EOR benefits;(5)pore sizes,porosity,absolute permeability and wettability range for low-salinity EOR;(6)continuous low-salinity injection vs.slug-wise injection;(7)grouping of possible low-salinity mechanisms;(8)contradictions or similarities between laboratory experiments and field evidence;and(9)compositional variations in tested low-salinity waters.A proposed screening criterion for low-salinity waterflooding is introduced.It can be concluded that either one or more of these mechanisms,or a combination thereof,may be the case-specific mechanism,i.e.,depending on the particular oil–brine–rock(OBR)system rather than something that is"universal"or universally applicable.Therefore,every OBR system that is unique or specific ought to be individually investigated to determine the benefits(if any)of low-salinity water injection;however,the proposed screening criteria may help in narrowing down some of the dominant responsible mechanisms.Although this review primarily focuses on sandstones,given the prominence of carbonates containing^60%of the world’s oil reserves,a summary of possible mechanisms and screening criteria,pertaining to low-salinity waterflooding,for carbonates is also included.Finally,the enhancement of polymer flooding by using low-salinity water as a makeup water to further decrease the residual oil saturation is also discussed.

Effect of water salinity on oil/brine interfacial behaviour during low salinity waterflooding: A mechanistic study

In recent years,controlling the salinity and composition of the injected water has become an emerging enhanced oil recovery(EOR)technique,often described as low salinity(LS)waterflooding.This work is done with the intention to contribute to the ongoing discussions about LS waterflooding mechanism(s).For this purpose,a series of different experiments were conducted.At first,the effect of salinity on the interfacial tension(IFT)and the contact angle was evaluated with a crude oil sample.Then to achieve more accurate results in observing oil/water interface,similar IFT experiments were also carried out on a synthetic oil containing asphaltenes.Thereafter,microscopic visualization using glass micromodel was performed on the interface of the synthetic oil sample and brines.Four brine solutions including Sea Water(SW),it's dilutions and formation water(FW)were used for various experiments.Finally,to investigate the presented mechanism by other authors,a series of Environmental Scanning Electron Microscopy(ESEM)analysis on the synthetic oil was carried out to understand better the phase behaviour after contacting both synthetic oil and water phases from the micromodel experiment.Based on the existing mechanism,there exists an optimal concentration beyond which dilution is no longer an effective process.

Effect of Long-Term Low-Salinity Culture on the Survival, Growth, and Nutrient Composition of Mud Crab Scylla paramamosain

This study investigated the effects of long-term low-salinity on the growth performance,proximate composition,amino acid and fatty acid profiles of Scylla paramamosain.The salinity of the low-salinity-culture group(LC)and maintained-salinity-cul-ture group(MC)were set at 5 and 25 respectively.After rearing for 30 d,the survival rate(SR)of the LC group was significantly lower,whereas the average daily molting frequency(ADMF)was significantly higher than those in MC group(P<0.05).There were no significant difference for weight gain rate(WGR)and specific growth rate(SGR)between the two groups.The moisture content of the LC group was slightly higher than the MC group without significant difference.The contents of ash,crude lipid and crude pro-tein in the LC group were lower than those in the MC group,but no significant differences were found except for ash content.A total of 17 free amino acids and 23 fatty acids were identified from the muscle of S.paramamosain.The total amino acids(TAA),essen-tial amino acids(EAA)and essential amino acid index(EAAI)had no significant difference between the two groups.The crabs from LC group had a significantly higher HUFA,including EPA,DHA,ARA.The percentage of n-3 PUFA and the ratio of n-3/n-6 PUFA were significantly higher in the LC group.These results indicated that S.paramamosain rearing at low salinity had significantly de-creased SR;however,the low-salinity environment significantly promoted the accumulation of unsaturated fatty acids(UFAs),espe-cially the n-3 PUFA,which might be related to the osmoregulation mechanism.

Physiological and Molecular Analyses of Low-Salinity Stress Response in the Cuttlefish(Sepia pharaonis)Juveniles

As a stenohaline species,the survival of Sepia pharaonis can be affected by salinity significantly.This study aimed to explore the function of decreasing salinity on the survival of Sepia pharaonis,which can provide an advanced production guide on the culture of S.pharaonis in the rainy season.Salinity was gradually decreased from 29 to 22 within 48 h to acclimate S.pharaonis to a low-salinity environment.After ten days of breeding under low-salinity of 22,the death rate was high.In this process,changes in tissue and cell structures in the larval liver,biochemical indicators,and osmoregulation-related gene expression were examined.In-terestingly,hepatocytes in the low-salinity group were irregular,had dissolved tissue inclusions,and contained vacuolized cells.There-fore,low salinity caused severe damages at a cellular level that can elevate the mortality rate.A gradual decline in salinity limited the full adaptation of S.pharaonis.Biochemical indicators and osmoregulation-related gene expression changed similarly.For instance,the trend of malondialdehyde(MAD)as a product of lipid peroxidation reflected the degree of damage to the body by free radicals.The antioxidant system of S.pharaonis could cope with oxidative stress caused by the change in salinity to a certain extent.Osmo-regulation-related genes’expression also showed an optimistic result,that is,S.pharaonis responded positively to the change in sali-nity by adjusting the expression of osmoregulation-related genes.Conversely,the increase in mortality at day 10 also proved the weak adaptation capability of S.pharaonis.This study indicated that S.pharaonis can adapt to a low-salinity environment with a li-mited extent.

Effect of multi-component ions exchange on low salinity EOR:Coupled geochemical simulation study

The mechanism(s)of Low salinity water flooding(LSWF)has been extensively investigated for 15 e20 years,as a cost-effective and environmentally friendly technique for improved oil recovery.However,there is still no consensus on the dominant mechanism(s)behind low salinity effect due to the complexity of interactions in the Crude oil/Brine/Rock(COBR)system.While wettability is most agreed mechanism of low salinity EOR effect.Nevertheless,the mechanism(s)behind the wettability change is debated between multi-component ion exchange(MIE)and double layer expansion(DLE)in sandstone reservoirs.This paper aims to investigate the effectiveness of MIE with a coupled geochemical-reservoir model using published experimental data reported by Nasralla and Nasr-El-Din[1].We created core-scale numerical models with parameters identical to those used in the experiments.We simulated the low salinity effect using a commercial reservoir simulator,CMG-GEM,by coupling three chemical reactions:(1)aqueous reaction,(2)multi-component ion exchange,and(3)mineral dissolution and precipitation.We modelled the adsorption of divalent cations on the surface of the clay minerals during low salinity water injection.Simulation results were compared with the experimental results.Simulation results show that the fractional adsorption of divalent cations(Ca^2+)increased almost 25%by injecting a 2000 ppm NaCl solution,compared to initial 10,000 ppm NaCl.Injecting a 2000 ppm of CaCl2 solution,however,significantly increased the adsorbed Ca^2+from 0.1 to 1,which implies the complete saturation of mineral surface with divalent cations.Moreover,injecting 50,000 ppm of CaCl2 solution also demonstrated the same effect as the 2000 ppm CaCl2 solution but with a faster rate.Upon combining the simulation and experimental results,we concluded that the multicomponent ion exchange is not the sole mechanism behind low salinity effect for two reasons.First,almost 10%additional oil recovery was observed from the experiments by injecting the 2000 ppm CaCl2 compared with 50,000 ppm CaCl2 solutions.Even though in both cases the surface is expected to be fully saturated with Ca^2+according to the geochemical modelling.Second,6%incremental oil recovery was achieved from the experiments by injecting 2000 ppm NaCl solution compared with that of 50,000 ppm NaCl.Although 25%incremental adsorption of divalent cations(Ca^2+)were presented during the flooding of the 2000 ppm NaCl solution.Therefore,it is worth noting that the electrical double layer expansion due to the ion exchange needs to be taken into account to pinpoint the mechanism(s)of low-salinity water effect.

Morphological changes and variations in Na+/K+-ATPase activity in the gills of juvenile large yellow croaker (Larimichthys crocea) at low salinity

Gill morphological changes and physiological responses in juvenile large yellow croaker(Larimichthys crocea)were examined upon exposure to low salinity after indoor culture of the fish at salinities of 2,4,6,8,and 24‰(control group).The thickness of the lamellae was significantly higher in the low-salinity groups than in the control group;in contrast,the interlamellar space was significantly lower in the low-salinity groups than in the control group.Additionally,a significant negative correlation was found between the thickness of lamellae and interlamellar spaces(P<0.01).Mitochondria-rich cells(MRCs)were mainly found in the filament at 24‰salinity and proliferated in the lamellae at lower salinities,suggesting that filament and lamellar MRCs are responsible for ion secretion and absorption,respectively.Meanwhile,the activity of Na+/K+-ATPase(NKA)was significantly elevated with the decrease in salinity from 24‰to 4‰(P<0.05),which was consistent with MRCs proliferation.Finally,the activity of NKA declined at 2‰salinity(P<0.05),indicating the limit of osmoregulation,which was consistent with the degeneration and necrosis of the lamellae.Additionally,different levels of gill histopathological lesions,including pavement cell(PVC)exfoliation,lamellar epithelial lifting,edema,fusion,aneurism,and necrosis,were observed from salinities of 24 to 4‰,likely reducing the respiratory efficiency and compromising the health of juvenile fish.In conclusion,large yellow croaker juveniles could improve the osmoregulatory capacity by increasing lamellar MRCs and NKA activity with the decrease in salinity from 24 to 4‰.However,the associated histopathological lesions are likely to negatively influence the fish by affecting respiration and osmoregulation,especially when the salinity is below 4‰.

Addition of surfactants to Low Salinity Waterflooding in microfluidics system to increase oil recovery

This study was conducted to investigate the phenomenon of oil removal from inside pores using a self-designed microfluidic test kit.An artificial micromodel chip as a representation of porous rocks has been created with a uniform pore structure design and made of PMMA(Polymethyl Methacrylate)material.The micromodel chip has a porosity of 27.8%as well as a permeability of 2.7 Darcy.By using the microfluidic test kit,this study has investigated how low salinity water(LSW)injection with MgCl_(2)divalent ions and the addition of anionic surfactant,linear alkylbenzene sulfonate mixed with nonionic surfactants,nonylphenol ethoxylate(NP-10)affects to oil recovery.The injection of LSW and surfactant solution was carried out with different injection stages,injection rates and surfactant solutions con-centrations.Visual images during the injection process are recorded for analysis,which is the advantage of dynamic testing using this microfluidic test kit over conventional coreflooding.From this study,it is indicated that the selection of ions contained in LSW affects the success of LSW injection.Reducing the surfactant injection rate from 50 mL/min to 20 mL/min can increase the oil recovery from 1.27%to 4.29%.Oil recovery was also higher on surfactant injection which resulted in lower interfacial tension of the system based on the calculation of interfacial tension obtained from the Chun-Huh and Ghosh equations from the Winsor test.From all injection scenarios carried out in this study,the highest increase in oil recovery of 26.87%OOIP was obtained by injecting surfactant solutions directly in the secondary stage without prior LSW injection.

Experimental study on nanoparticles-assisted low-salinity water for enhanced oil recovery in asphaltenic oil reservoirs

The purpose of this research is to look into the augmentation of silica nanoparticles(NPs)with low salinity(LowSal)brine for EOR.A series of analyses,including oil/water interfacial tension(IFT)and rock wettability tests were undertaken to determine an optimal dispersion to flood into a porous carbonate core with a defined pore size distribution.At 60℃and 14.5 psi,the maximum drop(i.e.,roughly 12.5 mN/m)in oil/water IFT by 0.3 wt%brine occurred,but when 0.08 wt%silica was added to the brine,the IFT reduced to 14.51 mN/m at 60℃and 14.5 psi.The wettability analysis revealed a significant reduction in contact angle,from 142°to 72°and 59°,using 0.04 and 0.08 wt%silica in LowSal brine,but the extent reduced by brine alone was insufficient.The results of rock pore size characterization were discussed in terms of the accomplishment of operating EOR in the porous medium in the presence of NPs.The addition of 0.08 wt%silica to the injected brine resulted in an additional oil recovery of 16.3%OOIP as well as a significant shift in the endpoints/cross-points of the oil/water relative permeability curves.The findings of this research might help improve oil recovery from asphaltenic oil reservoirs or,more environmentally friendly,remediate petroleum crude-oil polluted soil.

Transcriptomic Analysis of Pacific Oyster(Crassostrea gigas) Zygotes Under Hypotonic Triploid Induction

Polyploid breeding is widely used in various marine species. Low salinity treatment is an effective method of inducing triploid of bivalve mollusks. In this study, RNA-seq was performed to determine genes and pathways involved in hyposaline adaption and cell division of Pacific oyster(Crassostrea gigas) zygotes, trying to better understand the possible molecular mechanism of hypo-osmotic induction. A total of 26965 unigenes were generated in the de novo assembly of clean Illumina reads with an average length of 934 bp and N50 of 1721 bp. Of 3024 differentially expressed genes(DEGs), 2501 were up-regulated and 523 were downregulated. GO(Gene Ontology) annotation and KEGG(Kyoto Encyclopedia of Genes and Genomes) pathway analysis of these DEGs revealed that these DEGs participate a variety of biological processes including osmoregulation, cytoskeleton organization, cell survival and death, and substantially modulate cell proliferation and embryonic development. In summery, RNA-seq methodology was applied for the first time to demonstrate hypotonic-induced transcriptomic alteration in oyster zygotes. Our findings not only interpreted the relatively high mortality of induced larvae, but also provided a valuable reference for further investigations on the mechanism of hyposaline induction, thus should aid to the application of low salinity in triploid induction in large scale aquaculture in future.

Insights into wettability alteration during low-salinity water flooding by capacitance-resistance model

The capacitance-resistance model(CRM)has been widely implemented to model and optimise water-flooding and enhanced oil recovery(EOR)techniques.However,there is a gap in the application of CRM to analyse physical phenomena in porous media as well as the performance of EOR methods,such as low-salinity water(LSW)flooding.The main purposes of this study were to investigate how changes in time constant,as a CRM parameter,can represent physical phenomena in porous media such as wettability alteration.Moreover,to show CRM is a reliable tool to use for interpretation of LSW process as an EOR method.The results of different experimental/modelling studies in this research showed that in CRM model time constant increases when the wettability alters to a water wetness state,whereby the smallest time constant value is observed for the oil wet medium and the highest is observed for the water wet medium.The cases with a gradual alteration in wettability show an increasing trend with the dilution of the injection water.The core flooding data confirms the observed results of the simulation approach.The increment in time constant values indicates the resistance against displacing fluid,which is due to the wettability alteration of the porous medium,resulting in additional oil production.The observations made during this research illustrate that the time constant parameter can be a powerful tool for comparing different EOR techniques,since it is a good indication of the speed of impact of a particular injection fluid on production.