Polymer Retention during Flow of Polymer Solutions through Porous Media

Polymer solution flow and retention through porous media is of interest to many applications in the oil industry such as drilling, water shut-off and enhanced oil recovery. Operators of mature oil and gas fields are faced with the problem of excessive water production (EWP), which can cause a premature abandonment of some oil and gas wells. It has been found that the injection of high molecular weight polymer solutions through the pay zones of the oil and gas wells would induce a sharp decrease of the water production without affecting the oil and gas production. This effect is called disproportionate permeability reduction (DPR) and the polymer solutions inducing such an effect are called relative permeability modifiers (RPM). Hence, the DPR effect has been utilized in the water shut-off or conformance control of oil and gas wells suffering from EWP. In spite of the extensive research of the DPR effect, there is still a lack of agreement on the mechanisms controlling such an effect and relatively high percentage failures are observed during conformance control field applications. Polymer retention in porous media has been attributed to mechanisms such as bridging-adsorption, adsorption-entanglement, and flow-induced adsorption. These mechanisms have been proposed to account for the increase in flow resistance during or after the flow of polymer solutions through porous media. The DPR effect has been attributed to effects induced by this retained polymer such as steric and lubrication effects, wettability change, segregated oil and water pathways, and swelling and shrinking of the adsorbed polymer layer. The aim of this study is to add knowledge on the effect of polymer solution flow on polymer retention in porous media. In this study, the rheology of high molecular weight polymer solutions was studied using a cone-and-plate setup. Moreover, the characteristics and the effective hydrodynamic thickness of adsorbed polymer layers on glass from these polymer solutions under static conditions were investigated using atomic force microscopy (AFM). Also, quartz crystal microbalance with the dissipation monitoring (QCM-D) was used to investigate the effect of increasing the flow rate of polymer solutions on the adsorbed amount on silica and gold surfaces. Additionally, the mobility reduction and the residual resistance as a result of polymer solution flow through single glass capillaries, 2D and 3D models of porous media were studied. The implementation of the above techniques was used to relate the microscopic effect of the flow of the polymer solutions to the polymer retention in the porous media. The anti-thixotropic behaviour of the polymer solutions, which can be attributed to the shearinduced formation of micron-size transient entanglement networks (TEN), is expected to play a major role in the polymer retention in porous media. These microscopic structures can adsorb on the solid surfaces if the adsorption energy of the polymer/solid system is sufficient. Also, in porous media in which mechanical entrapment is possible, these structures can be entrapped in the small pores and pore throats. Two new mechanisms for polymer retention are proposed in this study: transient-entanglement networks adsorption (TENA) and transient-entanglement networks entrapment (TENE). The TENA is the retention mechanism of the TEN structures in flow systems in which mechanical entrapment is not possible provided that the adsorption energy is sufficient. If mechanical entrapment is possible, then the retention by adsorption and mechanical entrapment are lumped in the TENE mechanism. The results from this study have given a new insight on the flow and retention of polymer solutions through porous media. Hence, it is believed that the improved understanding will improve the design of high molecula

Frequency and type of toenail tumors in the dromedary camel

A total of 275 dromedary camels (16 males and 259 females) of local “Arabiyat” breed suffering from different types and degrees of severity of toenail tumors were surgically treated. Histopathological examination of the tissue samples removed from 50 tumor-like growths (2 males and 48 females) revealed three types of tumors; squamous cell carcinoma (70%), spiny keratoderma (22%) and fibroma (8%). An increased incidence of tumors was recorded in the medial when compared to the lateral toenails in both sexes. In females, the incidence in the medial toenails was 90/259 (34.75%) and 71/259 (27.41%) in the right and left forelimbs respectively when compared to the lateral toenails which was 25/259 (9.65%) and 5/259 (1.93%) for the respective right and left forelimbs. In the hind limbs, this ratio was 29/259 (11.20%) and 20/259 (7.72%) for right and left medial toenails respectively, whereas it was 17/259 (6.56%) and 2/259 (0.77%) for the right and left lateral toenails respectively. Similar to the observations in female camels, male camels also showed a higher incidence of these tumors in the medial when compared to the lateral toenails in both fore and hind limbs. Based on these findings, we conclude that in the dromedary camels, the medial toenails of the fore limbs are most commonly affected with tumors; with the most common tumor being the squamous cell carcinoma

Probabilistic seismic hazard maps for the sultanate of Oman

This study presents the results of the first probabilistic seismic hazard assessment (PSHA) in the framework of logic tree for Oman. The earthquake catalogue was homogenized, declustered, and used to define seismotectonic source model that characterizes the seismicity of Oman. Two seismic source models were used in the current study; the first consists of 26 seismic source zones, while the second is expressing the alternative view that seismicity is uniform along the entire Makran and Zagros zones. The recurrence parameters for all the seismogenic zones were determined using the doubly bounded exponential distribution except the zones of Makran, which were modelled using the characteristic distribution. Maximum earthquakes were determined and the horizontal ground accelerations in terms of geometric mean were calculated using ground-motion prediction relationships developed based upon seismic data obtained from active tectonic environments similar to those surrounding Oman. The alternative seismotectonic source models, maximum magnitude, and ground-motion prediction relationships were weighted and used to account for the epistemic uncertainty. Hazard maps at rock sites were produced for 5 % damped spectral acceleration (SA) values at 0.1, 0.2, 0.3, 1.0 and 2.0 s spectral periods as well as peak ground acceleration (PGA) for return periods of 475 and 2,475 years. The highest hazard is found in Khasab City with maximum SA at 0.2 s spectral period reaching 243 and 397 cm/s[superscript 2] for return periods 475 and 2,475 years, respectively. The sensitivity analysis reveals that the choice of seismic source model and the ground-motion prediction equation influences the results most.Oman Ministerial Cabinet (project number 22409017

Seismic microzonation for Muscat region, Sultanate of Oman

Site characterization was carried out for Muscat region using the ambient noise measurements applying the horizontal-to-vertical spectral ratio (HVSR) technique and using active seismic survey utilizing the multichannel analysis of surface waves (MASW) of survey data. Microtremors measurements were carried out at 459 sites using short-period sensors. This extensive survey allowed the fundamental resonance frequency of the soft soil to be mapped and areas prone to site amplification to be identified. The results indicate a progressive decrease in the fundamental resonance frequencies from the southern and eastern parts, where the bedrock outcrops, toward the northern coast where a thickness of sedimentary cover is present. Shear wave velocity (Vs) was evaluated using the 2-D MASW at carefully selected 99 representative sites in Muscat. These 99 sites were investigated with survey lines of 52 m length. 1-D and interpolated 2-D profiles were generated up to a depth range 20–40 m. The vertical Vs soundings were used in the SHAKE91 software in combination with suitable seismic input strong motion records to obtain the soil effect. Most of the study area has amplification values less than 2.0 for all the considered spectral periods. The estimated fundamental frequencies obtained using the H/V spectral ratio method and using SHAKE91 are found to be in a relatively good agreement. Maps of spectral amplification, earthquake characteristics on the ground surface for peak ground and spectral accelerations at 0.1, 0.2, 0.3, 1.0, and 2.0 s, for 475 years return period are produced. The surface ground motion maps show that the hazard level is moderate with expected PGA in the range 0.059–0.145 g for 475 years return period.Oman Ministerial Cabinet (project # 22409017

Deterministic seismic hazard assessment for Sultanate of Oman

The Sultanate of Oman forms the southeastern part of the Arabian plate, which is surrounded by relatively high active tectonic zones. Studies of seismic risk assessment in Oman have been an important on-going socioeconomic concern. Using the results of the seismic hazard assessment to improve building design and construction is an effective way to reduce the seismic risk. In the current study, seismic hazard assessment for the Sultanate of Oman is performed through the deterministic approach with particular attention on the uncertainty analysis applying a recently developed method. The input data set contains a defined seismotectonic model consisting of 26 seismic zones, maximum magnitudes, and 6 alternative ground motion prediction equations that were used in four different tectonic environments: obduction zone earthquake (Zagros fold thrust belt), subduction zone earthquakes (Makran subduction zones), normal and strike-slip transform earthquakes (Owen and Gulf of Aden zones), and stable craton seismicity (Arabian stable craton). This input data set yielded a total of 76 scenarios at each point of interest. A 10 % probability that any of the 76 scenarios may exceed the largest median ground acceleration is selected. The deterministic seismic hazards in terms of PGA, 5 % damped spectral acceleration at 0.1, 0.2, 1.0 and 2.0 s are performed at 254 selected points. The ground motion was calculated at the 50th and 84th percentile levels for selected probability of exceeding the median value. The largest ground motion in the Sultanate of Oman is observed in the northeastern part of the country.Oman Ministerial Cabinet (Project 22409017

Data-Driven Prediction of Vehicle Residual Value in the UAE Automotive Industry

In this master’s thesis, machine learning methods are applied to predict the residual value of a vehicle, focusing on the problem of estimating the vehicle’s price after sale. The research addresses some of the most important drivers of depreciation which include market segmentation, country, region-specific details, transmission type, and some numerical values obtained through factor analysis. This is very important to the automotive industry, leasing businesses, and financial institutions. The data was collected from the open-source online marketplace Dubizzle and contains 25 variables and 62,922 cases. The initial data posed notable challenges as there were non-standardized feature values, incomplete data fields, and inconsistent categorizations leading to assortment which demanded tremendous preprocessing efforts. The study adheres to the CRISP-DM (Cross-Industry Standard Process for Data Mining) model for data cleansing, structuring, and analysing. Vehicle residual value was predicted using Generalized Linear Regression, Least Squares Support Vector Machine (LSVM), and Neural Networks. The Neural Network model achieved the best results with a correlation of 0.988 and a relative error of 0.024, outperforming LSVM (correlation: 0.953, error: 0.092) and Regression (correlation: 0.936, error: 0.124) models, which were slightly lower in performance. The results validate that market trends, vehicle characteristics, and several hidden quantitative elements greatly influence retaining vehicle value. These findings address the emerging role of machine learning in the fields of automotive valuation and price prediction. Additional parameters like real-time market data, macroeconomic trends, and consumer sentiment indicators could be added to improve the prediction models in future research. The research builds on automotive analytics by constructing a model for vehicle depreciation estimation based on available data, which aids in pricing and evaluating financial risk

Factors influencing secondary school students' decisions to enter higher education : implications for higher education capacity in the Sultanate of Oman

The major goal of this study is to investigate the factors influencing Omani secondary school students' decisions to enter higher education, and the implications of such decisions for higher education provision.A number of economic, sociological, psychological, demographic and institutional variables, derived from previous literature and from analysis of labour market conditions in Oman, were incorporated in the conceptual framework guiding the research.A questionnaire, developed to suit the Omani context, was distributed to cluster samples of final-year public secondary school students, stratified by gender and specialisation, in 6 educational regions (N= 1950, valid returns= 1830). These were followed by semi-structured interviews with 42 volunteer students and telephone interviews with 4 decision-makers in the Ministry of Education, to discuss emergent issues. Government and non-government documents and statistics on higher education capacity and labour market demand were analysed.Of the factors, Human Capital Theory appears to be the most influential factor on students' decisions. Students' self confidence in their ability, parents' and family influence, and students' own attitudes and perception towards higher education followed. External factors of the labour market and school were considered less influential and friends least. Moreover, students' specific motivation was shaped and largely determined by the characteristics of the Omani work environment. Mediating effects of gender, specialisation and region were discovered.Current capacity of higher education does not meet either students' aspirations or the labour market demand. However, inequities in capacity, combined with the traditional Omani disdain for certain types of work, complicate the issue. Resolving the problem, therefore, requires not only expansion of higher education capacity, but also adjustment and redirection of demand. Additionally, adjusting educational demand will necessitate addressing disparities in salaries and employment conditions between the public and private sectors.Theoretical and policy implications are highlighted and specific recommendations address the latter

Living on the edge: Biofilms developing in oscillating environmental conditions

For the first time, the densities and diversity of microorganisms developed on ocean gliders were investigated using flow cytometry and Illumina MiSeq sequencing of 16S and 18S rRNA genes. Ocean gliders are autonomous buoyancy-driven underwater vehicles, equipped with sensors continuously recording physical, chemical, and biological parameters. Microbial biofilms were investigated on unprotected parts of the glider and surfaces coated with base, biocidal and chitosan paints. Biofilms on the glider were exposed to periodical oscillations of salinity, oxygen, temperature, pressure, depth and light, due to periodic ascending and descending of the vehicle. Among the unprotected surfaces, the highest microbial abundance was observed on the bottom of the glider’s body, while the lowest density was recorded on the glider’s nose. Antifouling paints had the lowest densities of microorganisms. Multidimensional analysis showed that the microbial communities formed on unprotected parts of the glider were significantly different from those on biocidal paint and in seawater

Concept analysis of self-efficacy

Self-efficacy has been used widely in health research, however its implication in health-promotion related interventions and practices is limited. The main aim of this paper is to demonstrate an in-depth analysis for the concept self-efficacy used in the health care. Also, determine its implications in health promotion interventions

Myocardial ischemia reperfusion injury: Apoptotic, inflammatory and oxidative stress role of galectin-3

Background/aims: Myocardial reperfusion has the potential to salvage the ischemic myocardium after a period of coronary occlusion. Reperfusion, however, can cause a wide spectrum of deleterious effects. Galectin-3 (GAL-3), a beta galactoside binding lectin, is closely associated with myocardial infarction (MI), myocardial fibrosis and heart failure. In our study, we investigated its role in ischemia-reperfusion injuries (IR) as this phenomenon is extremely relevant to the early intervention after acute MI.Methods: C57B6/J wild type (WT) mice and GAL-3 knockout (KO) mice were used for murine model of IR injury in the heart where a period of 30 minutes ischemia was followed by 24 hours of reperfusion. Heart samples were processed for immunohistochemical and immunofluorescent labeling, morphometric analysis, western blot and enzyme-linked immunosorbent assay to identify the apoptotic, inflammatory and oxidative stress role of GAL-3.Results: Our results show that there was a significant increase in GAL-3 levels in the heart which shows GAL-3 is playing a role in the ischemia reperfusion injury. Troponin I was also significantly higher in GAL-3-KO group than wild type. Our study shows that GAL-3 is associated with an increase in the antioxidant activity in the IR injured myocardium. Antioxidant enzymes superoxide dismutase, glutathione and catalase were found to be significantly raised in the GAL-3 wild type IR as compared to the GAL-3 KO IR group. A significant increase in apoptotic activity is seen in GAL-3 KO IR group as compared with GAL-3 wild IR group.Conclusion: Our study shows that GAL-3 can affect the redox pathways, controlling cell survival and death, and plays a protective role on the myocardium following IR injury