bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pore-Scale Modelling of Water Flooding in Mixed-Wet Rock Images: Effects of Initial Saturation and Wettability
Authors: Zhou Y. , Helland J. O. , Hatzignatiou D. G. 
Published: April 2012

Abstract
We simulate transient behaviour of viscous- and capillary-dominated water invasion at mixed-wet conditions directly in SEM images of Bentheim sandstone by treating the pore spaces as cross-sections of straight tubes. Initial conditions are established by drainage and wettability alteration. Constant rate or differential pressure is imposed between tube inlet and outlet. The phase pressures vary with positions along the tube length but remain unique in each cross-section, consistent with one-dimensional core-scale models. This leads to a nonlinear system of equations that are solved for the interface positions as a function of time. The cross-sectional fluid configurations are computed accurately at any capillary pressure and wetting condition by combining free energy minimisation with a menisci-determining procedure that identifies the intersections of two circles moving in opposite directions along the pore boundary. Circle rotation at pinned contact lines accounts for mixed-wet conditions. The fluid conductances are estimated by new explicit expressions that are shown to be in agreement with numerical computations performed directly in the cross-sectional fluid configurations.
An SEM image of Bentheim sandstone is taken as input to the developed model for simulating the evolution of saturation profiles during water floods for different flow rates and several mixed-wet conditions, which are established with different initial water saturations and contact angles. It is demonstrated that the simulated saturation profiles depend strongly on initial water saturation at mixed-wet conditions. The saturation profiles exhibit increasingly gradual behaviour in time as the contact angle, defined on the oil-wet solid surfaces, increases or the initial water saturation decreases. Front menisci associated with positive capillary pressures promote oil displacement by water, whereas for large and negative capillary pressures at small flow rates oil displaces water because the associated front menisci retract. This results in the development of pronounced gradual saturation fronts at mixed-wet conditions. The water floods simulated at conditions established with a large initial water saturation and small contact angle on the oil-wet solid surfaces, exhibit steep Buckley-Leverett saturation profiles for high flow rates because the capillary pressure is small and less important. The shape of the saturation profiles are interpreted based on the simulated capillary pressure curves and the corresponding fluid configurations occurring in the rock image.
The Design and Execution of an Alkaline-Surfactant-Polymer Pilot Test
Authors: Sharma A. , Azizi-Yarand A. , Clayton B. , Baker G. , McKinney P. , Britton C. , Delshad M. , Pope G. 
Published: April 2012

Abstract
A tertiary Alkaline-Surfactant-Polymer pilot flood was implemented during 2010 in the Illinois Basin of the United States and is continuing at this time. With initial discovery of the Bridgeport Sandstone formation in the early 1900's and over 60 years of waterflooding, the pilot was designed to demonstrate that ASP flooding could produce significant quantities of incremental oil in order to sanction a commercial project. Laboratory experiments including corefloods were done to determine the optimal chemical formulation for the pilot and to provide essential parameters for a numerical simulation model. Polymer injectivity tests, single well chemical tracer tests and an interwell tracer test program were all done to prepare for and support a full interpretation of the pilot results. A field laboratory was run through the duration of the pilot to monitor the quality the injection and production fluids, which turned out to be critical to the success of the pilot. We present the results and interpretation of the ASP pilot to date, the challenges faced during the project, and the lessons learnt from the field perspective.
Comparison of Various Gases for Enhanced Recovery from Shale Oil Reservoirs
Authors: Hoffman B. Todd 
Published: April 2012

Abstract
New technology in horizontal drilling and stimulation has caused production from ultra-tight oil formations to increase rapidly over the last decade. While initial rates are high, recovery factors for these types of reservoirs are predicted to be low, around 5–10%. Unlike conventional reservoirs, water flooding does not appear to be a viable secondary option due to its low injectivity. Recent analysis has shown that gas injection may be an effective alternative.
A 4-section area of the Elm Coulee field in eastern Montana is used to study the impact of different gas injection schemes: carbon dioxide, immiscible hydrocarbon and miscible hydrocarbon. This paper examines the difference in total recovery, production rate and efficiency using a flow simulation model. Recovery efficiency is similar for both miscible hydrocarbon gases and carbon dioxide with recoveries increasing from 6% on primary production to around 20% with gas injection.
While the increased recovery is encouraging, both methods have some practical limitations. Carbon dioxide is currently unavailable in many basins, and while hydrocarbon gases are available in most oil fields, they are rarely used as injectants because they are marketable. We performed a cost-benefit analysis of selling the hydrocarbon gas versus using it to increase oil production. We assumed a $10 million investment in compression and facilities for the 4-section area, and used a $5/mscf cost for the gas and $80/stb revenue for the oil. The net present value for these criteria in this area is $68 million and the rate of return is 83%.
The value of this work is that it demonstrates that injecting gas (both immiscible and especially miscible) will appreciably increase oil recovery in very low permeability reservoirs. These types of reservoirs are becoming more prevalent, and a large prize is available to those who find ways to increase recovery from them. In the case of hydrocarbon gas, the economics appear to be favorable for current commodity prices.
Self-Sustained CAGD Combustion Front Development; Experimental and Numerical Observations
Authors: Rahnema H. , Barrufet M. A. , Mamora D. 
Published: April 2012

Abstract
Using horizontal wells for In-Situ combustion operation brings new advantages. Horizontal wells provide larger contact area between the formation and combustion front. Mobilized oil does not necessarily should pass through cold oil bank to be produced and this improve the overall performance of the process. Combustion Assisted Gravity Drainage (CAGD) is an integrated horizontal well air injection process for in situ recovery and upgrading of heavy oil and tar sands bitumen. Short distance air injection and direct mobilized oil production are main features of this process that lead to stable sweep and high oil recovery. These characteristics identify CAGD process as a highly potential oil recovery method.
This paper summarizes recent experimental and numerical studies of CAGD process. In-Situ combustion experiments have been carried out using a rectangular 3D combustion cell with dimensions of 0.62 m, 0.41 m and 0.15 m. Enriched air (50% O2) has been injected to create and sustain the combustion front in the model. Experimental results showed that oil displacement occurs mainly by gravity drainage. Vigorous combustion was observed at the early stages near the heel of injection well, where peak temperature of about 690 °C was recorded. Moreover, a thermal simulator was used for history matching the laboratory data, while capturing the main mechanisms. Simulation results showed very good agreement between numerical and experimental data in terms of fluid production rate, combustion temperature and produced gas composition.
Effect of Neutral Salts and Temperature on the Partitioning Coefficient of Ethyl Formate Used for Enhanced Oil Recovery Assessment
Authors: Chavez-Majluf Nabil , Shiau B. J. , Harwell Jeffrey H. , Roberts Bruce L. , Lin Zhixun , Yuill Sean 
Published: April 2012

Abstract
Single well chemical tracer test is a technique for measuring residual oil saturation in a reservoir. For enhanced oil recovery applications, like waterflooding and chemical flooding (polymer/surfactant), it is essential to evaluate the efficiency of the process by determining the amount of oil displaced. This is where the single well chemical tracer test plays an important role. The partitioning coefficient of chemical tracers (K), a ratio of chemical tracer concentration in crude oil to concentration in brine, is a critical parameter for designing single well chemical tracer tests. Factors such as brine salinity, crude oil composition, and the procedures for measuring the K value can directly impact this critical parameter. The effect of the above-mentioned factors and reservoir temperature on the K value is studied and discussed in this work. Crude oil and brine from Oklahoma oil fields were used in the study along with decane and mimic brine. K value measurements at 30°C, and 60°C demonstrated that the temperature effect over K is minimal. In addition, the impact of brine minerals on the hydrolysis reaction of chemical tracers is also evaluated. K value measurements using different Oklahoma oil field brines and mimic brines with TDS ranging from 10,000 mg/L to 183,000 mg/L are also determined. The results clearly show a positive correlation between the K value and TDS. It is also observed that K values of mimic brines are particularly sensitive to changes in NaCl and MgCl2, whereas equivalent changes in CaCl2 and BaCl2 concentrations impact the K value less significantly. Ongoing tests are being carried on to continue to study of the effects of more brine components as wells as the effect of the crude oil composition over K. The results from this study can significantly help improve the protocol of single well chemical tracer tests.
Improved Reservoir Characterization using Petrophysical Classifiers within Electrofacies
Authors: Teh Woan Jing , Willhite G Paul , Doveton John H. 
Published: April 2012

Abstract
Estimation of permeability in a reservoir is necessary for simulation of production history. In mature fields, cores are limited so estimation of permeability is usually done from permeability-porosity correlations developed from cored wells. In this paper, a methodology is presented to predict permeability from well logs. The method groups the well logs into electrofacies, which are recognized to correspond with core lithofacies. The permeability-porosity correlations in the core data are developed using petrophysical classifiers - rock fabric number, rfn for dolomite and flow zone indicator, FZI for sandstone. The rfn and FZI are calculated for the cored wells and calibrated to the well log measurements within each electrofacies. The petrophysical classifiers extract the pore connectivity information from the well logs within each electrofacies, representing similar lithology. The permeability is then calculated from the porosity, using the petrophysical classifier values. Application of the methodology is demonstrated for dolomite and sandstone intervals in the Ogallah Field, Kansas. Permeabilities obtained from this approach closely matched core measurements.
Design and Development of Aqueous Colloidal Gas Aphrons for Enhanced Oil Recovery Applications
Authors: Samuel Shivana R. , Kuru Ergun , Trivedi Japan J 
Published: April 2012

Abstract
The problems associated with current chemical flooding technologies are based around inadequate sweep efficiencies and unfavorable mobility ratios which leave much of the recoverable oil left untouched in the pores of the reservoir. In order to address the low sweep efficiency and unfavorable mobility ratio issues, numerous formulations of polymer and surfactant base fluids have been used for enhanced oil recovery (EOR) applications with varying degree of success. The use of Colloidal Gas Aphrons (CGA) as an alternative chemical EOR technique is investigated in this study. Colloidal Gas Aphrons (CGA) are described as micro-bubbles which are 10 to 100 microns in size with a gas containing inner core encapsulated by a thin surfactant film. Aqueous CGA fluids are comprised of water, polymer and surfactant solutions.
An experimental study was conducted to determine the optimum surfactant and polymer concentrations which would yield stable micro-bubbles. The formulations of stable micro-bubbles were analyzed in terms of rheology, bubble size distribution and time stability.
In order to determine the displacement efficiency of CGA fluid in the EOR process, flooding experiments were conducted using a 2D linear model and 3D radial model, both packed with glass beads and saturated with mineral oil. Flooding experiments were performed using a) water, b) aqueous polymer solution, c) aqueous polymer and surfactant solution mixed at low shear rate, d) CGA fluid, e) water followed by CGA fluid, and f) water followed by polymer solution. Efficiency of oil recovery using the CGA fluid was compared to that of other fluids. All experiments were repeated to ensure consistent results. Less than 3 % variation in results was observed in all cases.
Pressure drop, ultimate recovery and injected fluid retention time data were measured during the flooding experiments. In addition, time-lapse images taken at regular intervals were analyzed to study frontal displacement patterns observed in 2-D experiments.
The results indicated that the CGA fluids showed more stable frontal displacement as compared to water flooding. The cumulative oil recovery performance of CGA fluids was comparable but slightly less than that of aqueous polymer solutions. CGA fluids, however, required significantly lower injection pressure as compared to aqueous polymer solutions. The breakthrough time of CGA fluids was longer than that of any of the other fluids tested indicating that CGAs have longer retention time.
Results from preliminary experiments encourage the further investigation of colloidal gas aphrons as an alternative EOR technique. The results will also be useful in designing an EOR process as an alternate to polymer, surfactant-polymer or WAG flood with particular importance to carbon sequestration as CO2 / flue gas can also be used in micro-bubble generation in place of air.
Difference between early clinical features of swine origin A H1N1 influenza corfirmed and not confirmed infection in Mexico
Authors: Rodríguez-Valero Monica , Prado Calleros Hector Manuel , Bravo Escobar Gerardo Arturo , Valdez Vázquez Rafael Ricardo , Figueroa Moreno Rafael , Martínez Montes Guillermo , Kawa Karasik Simón 
Published: April 2012

Introduction: The Swine Origin A H1N1 Influenza Virus (SOIV) pandemic emerged in April 2009 affecting people and health-care systems worldwide. This study examined the differences among the early clinical features presented in confirmed SOIV cases, those who tested negative for SOIV infection, fatalities, and hospitalized cases. Methodology: We reviewed 1,024 initial medical records of patients presenting with acute respiratory symptoms who attended the respiratory emergency room of a general hospital in Mexico and had a confirmatory test for influenza AH1N1 by RT-PCR from April to December 2009. Results: Out of 1,024 cases, 457 (44%) were men with a mean age of 31±17 years; however, of these, SOIV confirmed cases were younger (26±8, p=0.000). SOIV infection was confirmed in 36% of the patients. Most (%?) cases presented mild infection, 20% of the patients required hospitalization, and 0.09% patients died. Asthma was more frequent in confirmed cases (p=0.028). Presence of COPD, systemic arterial hypertension, and diabetes mellitus was significant in confirmed hospitalized cases. Pulmonary rales, wheezing, and sudden symptom onset were more frequent and statistically significant in confirmed patients. Influenza-like illness was more frequent in confirmed cases (p=0.049). Conclusions: This study presents one of the largest series of the new SOIV infection confirmed by RT-PCR reported. This infection is frequently mild and affects mainly young adults. Sudden symptoms onset, pulmonary rales, and wheezing are early features of this infection. Asthma, COPD, systemic arterial hypertension, and diabetes mellitus should be identified to identify potentially severe and fatal cases. ILI helps distinguish SOIV infection.
Oral care practice for the ventilated patients in intensive care units: a pilot survey
Authors: Soh Kim Lam , Shariff Ghazali Sazlina , Soh Kim Geok , Abdul Raman Rosna , Sharif Abdullah Sharifah Shafinaz , Ong Swee Leong 
Published: April 2012

Introduction: Ventilator-associated pneumonia (VAP) is the most common nosocomial infection in intensive care units (ICUs). One factor causing VAP is aspiration of oral colonisation, which may result from poor oral care practice. Oral care using tooth brushing can prevent formulation of dental plaque that can be a reservoir for microbes causing VAP. Methodology: A cross-sectional survey was conducted among 124 nurses, using a self-administered questionnaire, to determine methods used, frequency, and attitude of nurses toward oral care provided to mechanically ventilated patients in Malaysian ICUs. Results: Methods for oral care and their frequency of use varied between nurses even in the same unit. Cotton with forceps was used by 73.4% of the nurses. Some nurses used forceps and gauze (65%) or spatulas and gauze (36%). Toothbrushes were used by 50.8% of the nurses. Nurses in this hospital reported to have positive attitude toward providing oral care. Conclusions: The survey showed the need to have standardised oral care protocols in ICUs to improve quality of oral care provided to ventilated patients.
Occult hepatitis B in Egyptian thalassemic children
Authors: Shaker Olfat , Ahmed Amal , Abdel Satar Inas , El Ahl Hamza , Shousha Wafaa , Doss Wahid 
Published: April 2012

Introduction: Thalassemia is hereditary anemia which requires lifelong transfusion as treatment, and hepatitis viral infection is one of the risks of repeated transfusions. Hepatitis B outbreaks in health-care settings are still a serious public health concern worldwide. Blood samples negative for HBsAg but positive for HBV-DNA, with or without the presence of HBV antibodies, are classified as "occult" HBV infection (OBI). This study investigated the prevalence of occult HBV infection in Egyptian thalassemic children. Methodology: Eighty patients admitted to the Faculty of Medicine, Cairo University Hospital, were involved in this prospective study. Strict inclusion criteria were set to nullify the effect of confounding variables and further minimize selection bias. The following laboratory investigations were performed: complete blood count (CBC); serum AST and ALT; albumin; bilirubin; HBsAg; HBeAg; HBcAb; HCV-RNA; and HBV-DNA. Results: All our patients had no clinical manifestation suggestive of hepatitis. Molecular biology studies revealed positivity for HCV and HBV at 25% and 32.5% respectively. Conclusion: The estimated risk of acquiring hepatitis B and C infection in children receiving multiple blood transfusions is surprisingly high. Moreover, occult hepatitis B infection is a considerably risk.
Prevalence of keratinophilic fungi in soils of St. Kitts and Nevis
Authors: Gugnani Harish Chander , Sharma Soni , Gupta Brijinder , Gaddam Srinivas 
Published: April 2012

Introduction: Information on the prevalence of keratinophilic fungi in West Indies is scanty. Occurrence of keratinophilic fungi in soils of St. Kitts and Nevis has not been investigated previously. Methodology: The prevalence of keratinophilic fungi was investigated in 108 samples of soils of varying habitats from St. Kitts and 55 such samples from Nevis by hair-baiting technique. Fungal growths appearing on the hair baits after four to eight weeks of incubation at room temperature were microscopically examined and cultured on mycological media. Cultures were identified on the basis of colonial and microscopic features. Results: Forty-nine (45%) of the samples from St. Kitts and 38 (69%) from Nevis were positive for keratinophilic fungi. Microsporum gypseum complex, a well-known geophilic dermatophyte, was the most frequently recovered species being present in 15.7% of soils of St. Kitts and 40% of soils of Nevis. The next commonest species recovered was Chrysosporium indicum, represented by 15 (13.9%) isolates from St. Kitts and seven (12.7%) isolates from Nevis. Other infrequently isolated keratinophilic species included Chrysosporium tropicum, Chrysosporium keratinophilum, and unidentified Chrysosporium species. Conclusions: This study is the first of its kind in the islands of St. Kitts and Nevis. A high incidence of M. gypseum complex in the soil of these islands is a noteworthy finding of public health significance.
Epidemiological study of shigellosis in an urban area of Argentina
Authors: Rolfo Florencia , Marin Gustavo Horacio , Silberman Martin , Pattin Jorgelina , Giugnio Silvina , Gatti Blanca , Bettiol Marisa , Rigoni Ana 
Published: April 2012

Introduction: Shigellosis represents one of the main causes of bloody diarrhoea in South America. This study aimed to establish the incidence of shigellosis in an urban zone of Buenos Aires, Argentina, by examining the type of Shigella and living conditions associated with this infection. Methodology: Between January 2009 and December 2010 we analyzed shigellosis in children admitted to the public health service with bloody diarrhoea from La Plata, the capital of Buenos Aires, Argentina. A total of 372 children under 15 years old with Shigella present in their stool samples were admitted to the study. Variables studied were patient age, type of Shigella, family economic status, and access to sewage services and safe drinking water. Results: Shigella flexneri was found to be present in 66.8% of the cases. Incidence was 187 cases/year/100,000 children under 15 years old. Cases were mainly observed during the summer (38.5%) in the population of under 5 years old (69.1% of all cases). The risk of shigellosis increased 12 times in those children who lacked safe drinking water and this risk increased 1.5 times in the population without sewage services. Fewer cases of shigellosis were noted in downtown areas, while hot spots were identified in the suburbs. Treating one case of shigellosis has a local cost of US $976 while assuring safe drinking water and sewage services for one family costs US $634. Conclusion: Incidence of shigellosis in urban areas is associated with quality of water and sewage services. Policies aimed at providing education and improving public utilities networks can help to reduce the incidence of shigellosis.