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.

An overview of chemical enhanced oil recovery and its status in India

India is currently producing crude oil from matured fields because of insufficient discoveries of new fields.Therefore,in order to control the energy crisis in India,enhanced oil recovery(EOR)techniques are required to reduce the import of crude from the OPEC(Organization of the Petroleum Exporting Countries).This review mentions chemical EOR techniques(polymers,surfactants,alkali,nanoparticles,and combined alkali-surfactant-polymer flooding)and operations in India.Chemical EOR methods are one of the most efficient methods for oil displacement.The efficiency is enhanced by interfacial tension(IFT)reduction using surfactants and alkali,and mobility control of injected water is done by adding a polymer to increase the volumetric sweep efficiency.This paper also reviews the current trend of chemical EOR,prospects of chemical EOR in Indian oilfields,the development of chemical EOR in India with their challenges raising with economics,and screening criteria for chemical EOR implementation on the field scale.Furthermore,the review gives a brief idea about chemical EOR implementation in Indian oilfields in future prospects to increase the additional oil recovery from existing depleted fields to reduce the import of crude oil.The outcome of this review depicts all chemical EOR operations and recovery rates both at the laboratory scale and field scale around the country.The additional recovery rates are compared from various chemical EOR methods like conventional chemical flooding methods and conventional chemicals combined with nanoparticles on a laboratory scale.The development of chemical EOR in the past few decades and the EOR policy given by the government of India has been mentioned in this review.The analysis provides an idea about enhanced recovery screening and implementation of chemical EOR methods in existing fields will significantly reduce the energy crisis in India.

Landslide displacement prediction based on optimized empirical mode decomposition and deep bidirectional long short-term memory network

There are two technical challenges in predicting slope deformation.The first one is the random displacement,which could not be decomposed and predicted by numerically resolving the observed accumulated displacement and time series of a landslide.The second one is the dynamic evolution of a landslide,which could not be feasibly simulated simply by traditional prediction models.In this paper,a dynamic model of displacement prediction is introduced for composite landslides based on a combination of empirical mode decomposition with soft screening stop criteria(SSSC-EMD)and deep bidirectional long short-term memory(DBi-LSTM)neural network.In the proposed model,the time series analysis and SSSC-EMD are used to decompose the observed accumulated displacements of a slope into three components,viz.trend displacement,periodic displacement,and random displacement.Then,by analyzing the evolution pattern of a landslide and its key factors triggering landslides,appropriate influencing factors are selected for each displacement component,and DBi-LSTM neural network to carry out multi-datadriven dynamic prediction for each displacement component.An accumulated displacement prediction has been obtained by a summation of each component.For accuracy verification and engineering practicability of the model,field observations from two known landslides in China,the Xintan landslide and the Bazimen landslide were collected for comparison and evaluation.The case study verified that the model proposed in this paper can better characterize the"stepwise"deformation characteristics of a slope.As compared with long short-term memory(LSTM)neural network,support vector machine(SVM),and autoregressive integrated moving average(ARIMA)model,DBi-LSTM neural network has higher accuracy in predicting the periodic displacement of slope deformation,with the mean absolute percentage error reduced by 3.063%,14.913%,and 13.960%respectively,and the root mean square error reduced by 1.951 mm,8.954 mm and 7.790 mm respectively.Conclusively,this model not only has high prediction accuracy but also is more stable,which can provide new insight for practical landslide prevention and control engineering.

Characteristics of CO_2 sequestration in saline aquifers

Storage of CO2 in saline aquifers is a viable option for reducing the amount of CO2 released to the atmosphere. This paper provides an overall review of CO2 sequestration in saline aquifers. First, the principles of CO2 sequestration are presented, including CO2 phase behavior, CO2-water-rock interaction, and CO2 trapping mechanisms. Then storage capacity and CO2 injectivity are discussed as the main determinants of the storage potential of saline aquifers. Next, a site section process is addressed considering basin characteristics, reservoir characteristics, and economic and social concerns. Three main procedures are then presented to investigate the suitability of a site for CO2 sequestration, including site screening, detailed site characterization, and pilot field-scale test. The methods for these procedures are also presented, such as traditional site characterization methods, laboratory experiments, and numerical simulation. Finally, some operational aspects of sequestration are discussed, including well type, injection rate, CO2 purity, and injection strategy.

Long-term metformin therapy and vitamin B12 deficiency: An association to bear in mind

To date,metformin remains the first-line oral glucose-lowering drug used for the treatment of type 2 diabetes thanks to its well-established long-term safety and efficacy profile.Indeed,metformin is the most widely used oral insulinsensitizing agent,being prescribed to more than 100 million people worldwide,including patients with prediabetes,insulin resistance,and polycystic ovary syndrome.However,over the last decades several observational studies and meta-analyses have reported a significant association between long-term metformin therapy and an increased prevalence of vitamin B12 deficiency.Of note,evidence suggests that long-term and high-dose metformin therapy impairs vitamin B12 status.Vitamin B12(also referred to as cobalamin)is a water-soluble vitamin that is mainly obtained from animal-sourced foods.At the cellular level,vitamin B12 acts as a cofactor for enzymes that play a critical role in DNA synthesis and neuroprotection.Thus,vitamin B12 deficiency can lead to a number of clinical consequences that include hematologic abnormalities(e.g.,megaloblastic anemia and formation of hypersegmented neutrophils),progressive axonal demyelination and peripheral neuropathy.Nevertheless,no definite guidelines are currently available for vitamin B12 deficiency screening in patients on metformin therapy,and vitamin B12 deficiency remains frequently unrecognized in such individuals.Therefore,in this“field of vision”article we propose a list of criteria for a cost-effective vitamin B12 deficiency screening in metformin-treated patients,which could serve as a practical guide for identifying individuals at high risk for this condition.Moreover,we discuss additional relevant topics related to this field,including:(1)The lack of consensus about the exact definition of vitamin B12 deficiency;(2)The definition of reliable biomarkers of vitamin B12 status;(3)Causes of vitamin B12 deficiency other than metformin therapy that should be identified promptly in metformin-treated patients for a proper differential diagnosis;and(4)Potential pathophysiological mechanisms underlying metformin-induced vitamin B12 deficiency.Finally,we briefly review basic concepts related to vitamin B12 supplementation for the treatment of vitamin B12 deficiency,particularly when this condition is induced by metformin.

Screening of indicator pharmaceuticals and personal care products in landfill leachates: a case study in Shanghai, China

Identifying potential sources of pharmaceuticals and personal care products(PPCPs)in the environment is critical for the effective control of PPCP contamination.Landfill leachate is an important source of PPCPs in water;however,it has barely been involved in source apportionment due to the lack of indicator-PPCPs(i-PPCPs)in landfill leachates.This study provides the first systematic framework for identifying i-PPCPs for landfill leachates based on the wide-scope target monitoring of PPCPs.The number of target PPCPs increased from<20 in previous studies to 68 in the present study.Fifty-nine PPCPs were detected,with median concentrations in leachate samples ranging from below the method quantification limit(MQL)to 41μg/L,and 19 of them were rarely reported previously.A total of 29 target compounds were determined to be PPCPs of high concern by principal component analysis according to multiple criteria,including occurrence,exposure potential,and ecological effect.Coupled with source-specificity and representativeness analysis,erythromycin,gemfibrozil,and albendazole showed a significant difference in their occurrence in leachate compared to other potential sources(untreated and treated municipal wastewater and livestock wastewater)and correlated with total PPCP concentrations;these were recommended as i-PPCPs for leachates.Indicator screening procedure can be used to develop a sophisticated source apportionment method to identify sources of PPCPs from adjacent landfills.

The economic value of grassland ecosystem services: A global meta-analysis

Background:Grasslands provide a wide variety of ecosystem services that contribute to human wellbeing.While an increasing number of studies are evaluating the monetary value of grassland ecosystem services,most of them focus on specific grassland ecosystem services at regional or local scales,and they use different assessment methods.Methods:This paper provides a comprehensive assessment of the economic value of global grassland ecosystem services based on a meta-analysis of 702 observations from 134 primary studies.Results:The economic values of different ecosystem services cover a wide range of grassland types,regions,and estimation methods.The annual economic value per hectare ranges from$3955 for semidesert grasslands to$5466 for tropical grasslands.On average,regulating services have the highest value,which is approximately four times that of provisioning services or approximately eight times that of food supply services.Several factors impact the estimated ecosystem service values,including the evaluation method,source and year of publication,and study site.The results indicate that the annual economic value of global grasslands exceeds$20.8 trillion.Conclusions:The findings of this study not only provide useful information for understanding the economic value of various ecosystem services associated with different types of grasslands but also have important policy implications for the ecological conservation of grassland globally.