Study of numerical simulation method modelling gas injection into fractured reservoirs

Purpose. Fractures are the main flow channels in fractured reservoirs. The rapid flow characteristics of gas are outstanding in fractures. It is a major technical problem in the current oilfield development to calculate and accurately describe the fluid flow of this type of reservoir. Methods. This paper improves the calculation model of oil-water-gas phase equilibrium. Based on the discrete fracture net-work model, the numerical simulation mathematical model, numerical model and solution method of nitrogen injection were established. Findings. A simple discrete fracture network model was designed. Numerical simulations verify the correctness of the method. Originality. A fast solution method for gas injection numerical simulation based on discrete crack network model is proposed. Practical implications. The fractured reservoir numerical simulation method can accurately describe the flow of oil, water and gas in the fracture, which lays a foundation for the gas injection development mechanism and gas injection optimization research.Мета. Розробка нової методики чисельного моделювання впорскування газу у тріщинуваті колектори на основі моделі дискретної мережі тріщин. Методика. Для досягнення поставленої мети виконано критичний аналіз відомих методів моделювання, що довів відсутність на сьогоднішній день ефективних методів. Для дослідження проблемних питань у статті застосовано метод розрахунку фазової рівноваги на основі вільної енергії Гіббса як основи для чисельного моделювання закачування газу. Використовували ітераційний метод Ньютона для визначення складу кожної фази в мінімумі вільної енергії Гіббса. Результати. На основі моделі дискретної мережі тріщин сформовані математична модель, чисельна модель і метод рішення для чисельного моделювання закачування газу у тріщинуваті колектори. Правильність методу підтверджується спрощеною моделлю мережі дискретного руйнування. Результати чисельного моделювання узгоджуються з результатами теоретичних розрахунків. Отримана імітаційна модель дискретної мережі тріщин. Встановлено рівняння збереження маси нафти, води, газу та закачаного газу у тріщинах і матриці. Створено рівняння багатофазного потоку рідини у різних середовищах. Наукова новизна. Розроблено новий науково-методичний підхід до розрахунку та чисельного моделювання впорскування газу у тріщинуваті колектори, що враховує дискретну модель мережі тріщин. Практична значимість. Методика чисельного моделювання поведінки тріщинуватого колектору може точно описати потоки нафти, води і газу у тріщині, що сприяє більш детальному вивченню механізму розвитку впорскування газу та його оптимізації.Цель. Разработка новой методики численного моделирования впрыскивания газа в трещиноватые коллекторы на основе модели дискретной сети трещин. Методика. Для достижения поставленной цели выполнен критический анализ известных методов моделирования, доказавший отсутствие на сегодняшний день эффективных методов. Для исследования проблемных вопросов в статье применен метод расчета фазового равновесия на основе свободной энергии Гиббса как основа для численного моделирования закачки газа. Использовали итерационный метод Ньютона для определения состава каждой фазы в минимуме свободной энергии Гиббса. Результаты. На основе модели дискретной сети трещин сформированы математическая модель, численная модель и метод решения для численного моделирования закачки газа в трещиноватые коллекторы. Правильность метода подтверждается упрощенной моделью сети дискретного разрушения. Результаты численного моделирования согласуются с результатами теоретических расчетов. Получена имитационная модель дискретной сети трещин. Установлены уравнения сохранения массы нефти, воды, газа и закачанного газа в трещинах и матрице. Создано уравнение многофазного потока жидкости в различных средах. Научная новизна. Разработан новый научно-методический подход к расчету и численному моделированию впрыскивания газа в трещиноватые коллекторы, учитывающий дискретную модель сети трещин. Практическая значимость. Методика численного моделирования поведения трещиноватого коллектора может точно описать потоки нефти, воды и газа в трещине, что способствует более детальному изучению механизма развития впрыскивания газа и его оптимизации.Project supported by National Science Foundation (No. 51674285), Major National Science and Technology Special Projects (2016ZX05014-004)

The Impact of Sensing Range on Spatial-Temporal Opportunity

In this paper, we study the impact of secondary user (SU) sensing range on spectrum access opportunity in cognitive radio networks. We first derive a closed-form ex- pression of spectrum access opportunity by taking into ac- count the random variations in number, locations and trans- mitted powers of primary users (PUs). Then, we show how SU sensing range affects spectrum access opportunity, and the tradeoff between SU sensing range and spectrum ac- cess opportunity is formulated as an optimization problem to maximize spectrum access opportunity. Furthermore, we prove that there exists an optimal SU sensing range which yields the maximum spectrum access opportunity, and nu- merical results validate our theoretical analysis

Cryo-EM structures of herpes simplex virus type 1 portal vertex and packaged genome.

Herpesviruses are enveloped viruses that are prevalent in the human population and are responsible for diverse pathologies, including cold sores, birth defects and cancers. They are characterized by a highly pressurized pseudo-icosahedral capsid-with triangulation number (T) equal to 16-encapsidating a tightly packed double-stranded DNA (dsDNA) genome1-3. A key process in the herpesvirus life cycle involves the recruitment of an ATP-driven terminase to a unique portal vertex to recognize, package and cleave concatemeric dsDNA, ultimately giving rise to a pressurized, genome-containing virion4,5. Although this process has been studied in dsDNA phages6-9-with which herpesviruses bear some similarities-a lack of high-resolution in situ structures of genome-packaging machinery has prevented the elucidation of how these multi-step reactions, which require close coordination among multiple actors, occur in an integrated environment. To better define the structural basis of genome packaging and organization in herpes simplex virus type 1 (HSV-1), we developed sequential localized classification and symmetry relaxation methods to process cryo-electron microscopy (cryo-EM) images of HSV-1 virions, which enabled us to decouple and reconstruct hetero-symmetric and asymmetric elements within the pseudo-icosahedral capsid. Here we present in situ structures of the unique portal vertex, genomic termini and ordered dsDNA coils in the capsid spooled around a disordered dsDNA core. We identify tentacle-like helices and a globular complex capping the portal vertex that is not observed in phages, indicative of herpesvirus-specific adaptations in the DNA-packaging process. Finally, our atomic models of portal vertex elements reveal how the fivefold-related capsid accommodates symmetry mismatch imparted by the dodecameric portal-a longstanding mystery in icosahedral viruses-and inform possible DNA-sequence recognition and headful-sensing pathways involved in genome packaging. This work showcases how to resolve symmetry-mismatched elements in a large eukaryotic virus and provides insights into the mechanisms of herpesvirus genome packaging

Postsynaptic protein organization revealed by electron microscopy.

Neuronal synapses are key devices for transmitting and processing information in the nervous system. Synaptic plasticity, generally regarded as the cellular basis of learning and memory, involves changes of subcellular structures that take place at the nanoscale. High-resolution imaging methods, especially electron microscopy (EM), have allowed for quantitative analysis of such nanoscale structures in different types of synapses. In particular, the semi-ordered organization of neurotransmitter receptors and their interacting scaffolds in the postsynaptic density have been characterized for both excitatory and inhibitory synapses by studies using various EM techniques such as immuno-EM, electron tomography of high-pressure freezing and freeze-substituted samples, and cryo electron tomography. These techniques, in combination with new correlative approaches, will further facilitate our understanding of the molecular organization underlying diverse functions of neuronal synapses

Accumulation of Dense Core Vesicles in Hippocampal Synapses Following Chronic Inactivity.

The morphology and function of neuronal synapses are regulated by neural activity, as manifested in activity-dependent synapse maturation and various forms of synaptic plasticity. Here we employed cryo-electron tomography (cryo-ET) to visualize synaptic ultrastructure in cultured hippocampal neurons and investigated changes in subcellular features in response to chronic inactivity, a paradigm often used for the induction of homeostatic synaptic plasticity. We observed a more than 2-fold increase in the mean number of dense core vesicles (DCVs) in the presynaptic compartment of excitatory synapses and an almost 20-fold increase in the number of DCVs in the presynaptic compartment of inhibitory synapses after 2 days treatment with the voltage-gated sodium channel blocker tetrodotoxin (TTX). Short-term treatment with TTX and the N-methyl-D-aspartate receptor (NMDAR) antagonist amino-5-phosphonovaleric acid (AP5) caused a 3-fold increase in the number of DCVs within 100 nm of the active zone area in excitatory synapses but had no significant effects on the overall number of DCVs. In contrast, there were very few DCVs in the postsynaptic compartments of both synapse types under all conditions. These results are consistent with a role for presynaptic DCVs in activity-dependent synapse maturation. We speculate that these accumulated DCVs can be released upon reactivation and may contribute to homeostatic metaplasticity

DNA-Packing Portal and Capsid-Associated Tegument Complexes in the Tumor Herpesvirus KSHV.

Assembly of Kaposi's sarcoma-associated herpesvirus (KSHV) begins at a bacteriophage-like portal complex that nucleates formation of an icosahedral capsid with capsid-associated tegument complexes (CATCs) and facilitates translocation of an ∼150-kb dsDNA genome, followed by acquisition of a pleomorphic tegument and envelope. Because of deviation from icosahedral symmetry, KSHV portal and tegument structures have largely been obscured in previous studies. Using symmetry-relaxed cryo-EM, we determined the in situ structure of the KSHV portal and its interactions with surrounding capsid proteins, CATCs, and the terminal end of KSHV's dsDNA genome. Our atomic models of the portal and capsid/CATC, together with visualization of CATCs' variable occupancy and alternate orientation of CATC-interacting vertex triplexes, suggest a mechanism whereby the portal orchestrates procapsid formation and asymmetric long-range determination of CATC attachment during DNA packaging prior to pleomorphic tegumentation/envelopment. Structure-based mutageneses confirm that a triplex deep binding groove for CATCs is a hotspot that holds promise for antiviral development

Equation of motion for multiqubit entanglement in multiple independent noisy channels

We investigate the possibility and conditions to factorize the entanglement evolution of a multiqubit system passing through multi-sided noisy channels. By means of a lower bound of concurrence (LBC) as entanglement measure, we derive an explicit formula of LBC evolution of the N-qubit generalized Greenberger-Horne-Zeilinger (GGHZ) state under some typical noisy channels, based on which two kinds of factorizing conditions for the LBC evolution are presented. In this case, the time-dependent LBC can be determined by a product of initial LBC of the system and the LBC evolution of a maximally entangled GGHZ state under the same multi-sided noisy channels. We analyze the realistic situations where these two kinds of factorizing conditions can be satisfied. In addition, we also discuss the dependence of entanglement robustness on the number of the qubits and that of the noisy channels.Comment: 14 page

Screening for lipase-producing Enterobacter agglomerans for biodiesel catalyzation

This paper reports a comprehensive study of screening rapeseed soil sample in Victoria blue solution solid medium, with olive oil as sole carbon source. The lipase of Enterobacter agglomerans which hasthe highest activity was identified. Under the optimum conditions determined, the enzyme activity of this strain reached 39.09 U/mL. The optimal conditions were found to be: initial pH 7.0, agitating at 30°Cfor 48 h, with 2.0% (w/v) lactose as carbon source, 1.5% (w/v) beef extract and 1.0% (w/v) yeast extract as nitrogen source, and 0.1% (w/v) MgSO4·7H2O. Olive oil, sesame oil and tea oil as raw materials can be catalyzed to biodiesel by the lipase of this strain at 30°C and 180 rpm. And the yield reached 54.51% with sesame oil as raw material, even when they contained 92.4% (w/v) water in the starting materials. This strain will potentially serve as a promising alternative lipase for biodiesel production with raw materials containing water