The precipitation of asphaltenes from crude oils can lead to serious challenges during oil production and processing. This research investigates the kinetics of asphaltene precipitation from crude oils using n-alkane precipitant. For several decades, it has been understood that the precipitation of asphaltenes is a solubility-driven phenomenon, and the previous studies on the effect of time are usually limited to short time scales. By using optical microscopy and centrifugation-based separation, we have demonstrated that the time required to precipitate asphaltenes can actually vary from a few minutes to several months, depending on the precipitant concentration used. Our results demonstrate that no single concentration can be identified as the critical precipitant concentration for asphaltene precipitation. On the basis of long-term experiments, we have also been able to establish the solubility of asphaltenes as a function of the precipitant concentration, and it is shown that the short-term experiments overpredict the solubility. Similarities between the current work and other research areas are also discussed briefly. This research opens up a new paradigm for understanding asphaltene precipitation.

Asphaltenes are a solubility class of petroleum crude oil that can destabilize and deposit in both upstream and downstream processes. In this study, asphaltene deposits were generated in metal capillaries by heptane addition to crude oils, and it was found that deposition is caused by submicrometer asphaltene aggregates. Deposits were generated at heptane concentrations above and significantly below the instantaneous onset point. Analysis of the results reveals that the governing factor controlling the magnitude of asphaltene deposition is the concentration of insoluble asphaltenes present in a crude oilprecipitant mixture and the instantaneous onset point is irrelevant to the deposition process. Electron microscopy images of the deposits represent the first images and confirmation of arterial growth in laboratory generated asphaltene deposits. The axial deposit profile was found to be highly nonuniform. In addition, deposits formed shortly after when oil and heptane mix, revealing that the destabilization of asphaltenes occurs virtually immediately after a precipitant is added. The results were reproduced with a second crude oil, indicating that asphaltene deposition behavior is broadly applicable.

This study discusses the development of a generalized geometric population balance model for simulating the growth of asphaltene aggregates from the nanometer scale to micrometer-sized particles. The Smoluchowski kernel has been incorporated to describe the aggregation of asphaltene nanoaggregates, which is induced by the addition of a precipitant, e.g., heptane. Rather than using the discretization of particle sizes based on the particle volumes, a discretization scheme based on the number of asphaltene molecules is incorporated, which ensures that the mass is conserved in this model. The model is in good agreement with the experimental data for the evolution of asphaltene aggregates at different times collected by centrifugation. The particle size distribution (PSD) of the asphaltene aggregates as a function of time is also determined. It was observed that the shift of the PSD to larger diameters is faster in the case of higher heptane concentrations because of the greater mass of asphaltenes precipitated and the higher driving force for their aggregation at these conditions. Additionally, predictions for the onset time for asphaltene precipitation at lower heptane concentrations are also presented.

Asphaltene precipitation is a challenging problem for the petroleum industry. Changes in pressure, temperature, and composition are key factors that influence asphaltene stability in crude oils. We have previously shown that the time required to precipitate asphaltenes can actually vary from a few minutes to several months, depending on the precipitant concentration used and that no single concentration can be identified as the critical precipitant concentration for asphaltene precipitation. Both upstream and downstream processes involve temperature variations, which can cause the precipitation of asphaltenes and can lead to deposition and fouling problems during the production, transportation, and processing of crude oils. In the present work, we extend the findings of the previous research to incorporate the effect of temperature on the precipitation kinetics of asphaltenes. The effect of temperature on asphaltene stability can be complex and various competing effects can be identified. We demonstrate that at higher temperatures the precipitation onset time for asphaltenes is shorter and their solubility is higher. We also present a hypothesis to explain these results and demonstrate that the viscosity difference resulting from a change in temperature is the key parameter in the aggregation of asphaltenes and controls the onset time for precipitation. We also consider the effect of expansion of hydrocarbons, oxidation of crude oil, and the loss of light hydrocarbons due to evaporation, all of which are possible when temperature is increased. This research provides a unified approach to understand the variety of factors that change as a result of temperature variation and evaluates their individual contributions to changes in asphaltene precipitation kinetics and their solubility.

No abstract

Asphaltene deposition is one of the major flow assurance problems in upstream and downstream crude oil recovery operations. In order to prevent potential loss and reduce downtime due to asphaltenes, it is critical to understand the physics of asphaltene adsorption. This study presents a preliminary investigation of asphaltene adsorption from crude oils onto stainless-steel surfaces using the quartz crystal microbalance with dissipation (QCM-D) technique and proposes a theoretical interpretation of the deposition mechanism for asphaltene molecules. The kinetics of deposition at different concentrations was examined, and the sizes of the deposited asphaltene molecules were estimated from the initial adsorption kinetics. Numerical analysis of the experimental data using the theoretical two-step deposition model was attempted, and the optimized adsorption parameters proved to be quite close to those values obtained for some rock types in earlier adsorption studies. Despite asphaltene precipitation increasing with increasing heptane percentage, the deposition of asphaltenes was found to be maximum at 70 vol% heptane content. The performance of a commercial inhibitor was then assessed under different conditions using the developed experimental metrics, and the inhibitor was found to be able to reduce the maximum deposition amount at the solubility with 70 vol% heptane fraction, which happens to be the same condition that generates the largest amount of deposition. The information gained on the solubility effect and inhibitor performance is essential to help the industry better manage asphaltene-related flow assurance problems in crude oil recovery.

<p class="abstract"><strong>Background:</strong> A prospective study to analyze the facial nerve branching pattern as seen in various parotidectomy surgeries in Kashmiri population. Main objective was to find out various branching patterns among peripheral branches of facial nerve in parotid tissue so that new young ENT surgeons could get benefited and it should be easy for them to perform parotid surgeries with less complications and unpredictable outcome.</p><p class="abstract"><strong>Methods:</strong> The prospective study was conducted in 35 patients undergoing superficial parotidectomy in our department of otorhinolaryngology GMC Srinagar over a period of one and half year. Facial nerve branching pattern was classified according to the description given by Davis et al. Branching pattern of main trunk was also observed in all cases.  </p><p class="abstract"><strong>Results:</strong> The most common type of branching pattern of facial nerve in our study was type I seen in 12 (34.2%) patients, followed by type III seen in 9 (25.7%), followed by type II in 5 (14.2%), type IV in 4 (11.4%) patients, followed by type V in 3 (8.5%) and VI in 2 (5.7%).</p><p><strong>Conclusions:</strong> Type I branching pattern is the most common branching pattern of the facial nerve (34.2%) followed by type III (25.7%), following the pattern as described by Davis. Main trunk was found single in 32 (91.4%%) patients however in 3 (8.57%) patients trunk was dividing in 2 branches before dividing in peripheral branching pattern as described above. </p>

<p class="abstract"><strong>Background:</strong> COVID-19 has led to the global pandemic which started in Wuhan, in China. It is highly contagious and the presenting symptoms may not alarm the patient or the doctor and can be confused with allergies and other simple viral respiratory tract infections in mild cases. Aim of this study was to evaluate the various presentations of COVID-19 patients in department of otorhinolaryngology.</p><p class="abstract"><strong>Methods:</strong> This study was done during pandemic, from March 2020 to May 2020 for a period of 3 months in government medical college Srinagar. If the patient had any significant travel or contact with the known or suspected COVID-19 positive patient and the various ENT symptoms with which COVID positive patients presented, to the department were evaluated.  </p><p class="abstract"><strong>Results:</strong> Majority of patients were males between the age group of 21 to 40 years. The most common symptoms encountered was cough and fever followed by sore throat and rhinitis. One patient also presented with subacute thyroiditis and two others as neck abscess. Two patients presented with sudden sensorineural hearing loss.</p><p class="abstract"><strong>Conclusions:</strong> Patients in the department can present with mild respiratory tract infection or also with some peculiar symptoms of subacute thyroiditis or abcess. So, careful history is the key to recognize these patients. And it is highly recommended that doctors during addressing the patients should be in proper protective kits to avoid contracting the disease.</p>