Nanoparticles and Surfactants-Stabilized Foam and Emulsion for Gas Mobility Control in Petroleum Reservoirs

This work proposes the use of nanoparticles (NPs) to stabilize foams/emulsions for gas mobility control and to improve the gas sweep efficiency. First, NPs were used alone to stabilize emulsion. Second, NPs and surfactants were used synergistically to improve the stability of foam. Surface modified silica NPs with DCDMS, hidden chemical, and PEG were used to assess the ability of NPs to stabilize gas-liquid emulsions at reservoir conditions. Silica modified with DCDMS was able to increase the CO2 viscosity 26-60 fold. Silica modified with hidden chemical was able to increase the CO2 viscosity 25-53 fold and N2 viscosity 22-54 fold. Finally, the presence of silica modified with PEG was able to increase the CO2 viscosity 24-49 fold. All tested materials showed an inverse relationship between the emulsion quality and viscosity. In most cases, salinity was found to have a significant impact on emulsion strength. As salinity increased, the emulsion viscosity increased, too. The concentration of NPs showed similar behavior, with NPs concentration and viscosity being directly proportional. Shear rate was found to be a crucial parameter for emulsion stability and viscosity, with a threshold shear rate being necessary to stabilize emulsions. Also, increased pressure can improve emulsion stability to produce a more viscous emulsion. The presence of NPs in all surfactant solutions enhanced foam stability and produced more viscous foams compared to surfactant alone. The presence of NPs with ENORDET A031 was able to increase the gas MRF up to 84.57 compared to 72.57 for surfactant. For the mixtures of silica NPs and nonionic surfactants, results showed that the concentration of surfactant and NPs is a crucial parameter for foam stability and that there is an optimum concentration for strong foam production. For N2 foam, the mixture of surface modified silica NPs and CNF surfactant resulted in a total recovery of 49.05% compared to 41.45% for surfactant alone. The total oil recovery for the same mixture with sc-CO2 was 80.05% of the OOIP. This is around 4% higher than the surfactant case and 8.55% higher than sc-CO2. In fractured rocks, oil recoveries during secondary production mechanisms for the mixture of surface modified silica NPs and CNF surfactant, the surfactant alone, and sc-CO2 alone were 12.62, 8.41 and 7.21% of the OOIP, respectively

Prevalence and Determinants of Anemia in Pregnancy, Sana’a, Yemen

Anemia is a global public health problem in both developing and developed countries, especially among pregnant women. The aim of the study was to estimate the prevalence of anemia among pregnant women in Sana'a governorate, Yemen, and to identify the determinants contributing to it, and to assess knowledge regarding it. The study was conducted using a cross-sectional approach. It included 360 pregnant women attending the maternity clinics of maternity hospitals. A predesigned structured interviewing questionnaire was used to collect data from the pregnant women. Laboratory investigations were done. The prevalence of anemia was found to be 40.3%, and was higher among females aged 35 to less than 45 years, those with poor income and poor nutritional level. The risk of anemia increased with the gestational age, gravidity, decreased birth spacing, drinking tea and coffee after meals, decreased intake of proteins and low level of knowledge and income. The binary logistic regression model indicated a significant impact of the education and occupation on the level of knowledge of pregnant women. Anemia was found out to be a severe public health problem among pregnant women in Yemen. Identified risk factors should be considered for its prevention and control

On Some Shrinkage Techniques For Estimating The Parameters Of Exponential Distribution

A variety of shrinkage methods have been proposed for estimation of some unknown parameter by considering estimators based on a prior guess of the value of the parameter. We compare some of the shrunken estimators for the parameters^ and 9 of the exponential distribution through simulatio

Time-Dependent Physicochemical Changes of Carbonate Surfaces from SmartWater (Diluted Seawater) Flooding Processes for Improved Oil Recovery.

Over the past few decades, field- and laboratory-scale studies have shown enhancements in oil recovery when reservoirs, which contain high-salinity formation water (FW), are waterflooded with modified-salinity salt water (widely referred to as the low-salinity, dilution, or SmartWater effect for improved oil recovery). In this study, we investigated the time dependence of the physicochemical processes that occur during diluted seawater (i.e., SmartWater) waterflooding processes of specific relevance to carbonate oil reservoirs. We measured the changes to oil/water/rock wettability, surface roughness, and surface chemical composition during SmartWater flooding using 10-fold-diluted seawater under mimicked oil reservoir conditions with calcite and carbonate reservoir rocks. Distinct effects due to SmartWater flooding were observed and found to occur on two different timescales: (1) a rapid (<15 min) increase in the colloidal electrostatic double-layer repulsion between the rock and oil across the SmartWater, leading to a decreased oil/water/rock adhesion energy and thus increased water wetness and (2) slower (>12 h to complete) physicochemical changes of the calcite and carbonate reservoir rock surfaces, including surface roughening via the dissolution of rock and the reprecipitation of dissolved carbonate species after exchanging key ions (Ca2+, Mg2+, CO32-, and SO42- in carbonates) with those in the flooding SmartWater. Our experiments using crude oil from a carbonate reservoir reveal that these reservoir rock surfaces are covered with organic-ionic preadsorbed films (ad-layers), which the SmartWater removes (detaches) as flakes. Removal of the organic-ionic ad-layers by SmartWater flooding enhances oil release from the surfaces, which was found to be critical to increasing the water wetness and significantly improving oil removal from carbonates. Additionally, the increase in water wetness is further enhanced by roughening of the rock surfaces, which decreases the effective contact (interaction) area between the oil and rock interfaces. Furthermore, we found that the rate of these slower physicochemical changes to the carbonate rock surfaces increases with increasing temperature (at least up to an experimental temperature of 75 °C). Our results suggest that the effectiveness of improved oil recovery from SmartWater flooding depends strongly on the formation of the organic-ionic ad-layers. In oil reservoirs where the ad-layer is fully developed and robust, injecting SmartWater would lead to significant removal of the ad-layer and improved oil recovery

COVID-19 in a pregnant patient with beta-thalassemia major: A case report

Further studies are needed on this unique population to better manage them and increase their chances of normal pregnancy and fewer complications and more favorable outcomes

Response of crude oil deposited organic layers to brines of different salinity:An atomic force microscopy study on carbonate surfaces

The various microscopic processes that take place during enhanced oil-recovery upon injecting low salinity brines are quite complex, particularly for carbonate reservoirs. In this study, we characterize the in-situ microscopic responses of the organic layers deposited on flat Iceland spar calcite surface to brines of different salinity using Atomic force Microscopy (AFM). Organic layers were deposited from crude oil at the end of a two-step aging procedure. AFM topography images reveal that the organic layers remain stable in high-salinity brines and desorb upon exposure to low-salinity brines. In addition, the organic layers swell in low-salinity brines, and the stiffness of the organic layers is found to directly proportional to the brine salinity. These observations are explained in terms of ‘salting-out’ effects, where the affinity of organic layers to solvent molecules increases upon reducing the brine salinity. The swelling and desorption of organic materials provide access for the brine to mineral surface causing dissolution and change in wetting properties of the surface. Our results show the significance of de-stabilizing the organic layer on rock surfaces in order to design any successful improved oil recovery (IOR) strategy

Effects of ions on the characteristics of monolayer at brine/oil interfaces

The advanced waterflooding technologies through salinity and ionic content adjustment can make favorable impacts on rock wettability and oil recovery. In carbonate reservoirs, SmartWater at low ionic strength showed strong chemical interactions with carbonate minerals and oil components. As a result, several hypotheses are proposed in literature as ionic exchange, rock dissolution, surface charges and others. The applied macroscopic and microscopic technologies have certain limitations in identifying the structures at interfaces especially at monolayers. In this paper, advanced Sum Frequency Generation (SFG) spectroscopy is utilized for the first time to characterize the chemical structures of molecules at the brine/oil interfaces. Different brines recipes and model oil are tested to determine the effects of individual and combined ions on the monolayer structures. Stearic acid is also mixed with hydrocarbons to mimic the acidity condition of fluids in the reservoir. The change in the chemical structure is mo nitored with time at a broad wavenumber range from 1,000 to 3,800 cm-1. Distinct spectral signatures of oil components and water ions are detected at different pH conditions. The SFG data is compared with the previous macroscopic wettability results to predict the components that are highly affected during waterflooding and enhanced oil recovery (EOR) processes. This study brings new insights on understanding the chemical structures at the thin monolayers of flat and curved geometric at different aqueous interfaces. The measured spectra, coupled with a wide range of laser polarization settings, and signal intensity trends are discussed in terms of composition, and structure of organic and inorganic components. For example, the intensity for SmartWater at certain wavenumber is three folds higher when compared to high salinity water. This indicates that the interactions at oil/water interfaces are enhanced at lower ionic strengths. In addition, these findings are also confirmed with similar behaviors at a higher salinity brine as connate formation brine. The novelty of this interfacial study can provide better understanding of the reaction mechanisms altering the ionic strength and salinity of injection water and its impact due to the changes in geometric interfaces. Such understanding is also crucial to optimize the chemistry of injection water and its interaction with oil components and carbonate rock, to ultimately alter wettability toward water-wet