Influence of proppant physical properties on sand accumulation in hydraulic fractures

The proppant accumulation form in fractures is related to the formation conductivity after fracture closure, also closely related to the production rate of oil/gas wells. In order to investigate the influence of proppant physical properties on sand accumulation in fractures, a particle–fluid coupling flow model is established based on the Euler two-fluid model. Geometric parameters of a fracture in tight oil wells are approximately scaled in equal proportion as the physical model, which is solved by the finite volume method. And the model accuracy is verified by comparing with the physical experimental simulation in the literature. Results show that the higher proppant concentration corresponds to the faster particle sedimentation rate, and the greater sand embankment accumulation as well. However, the fluid viscosity will increase, inhibiting proppant migration to the deep part of the fracture. Reducing proppant density and particle size will enhance the fluidization ability of particles, which is conducive to the migration to the deep fracture at the initial stage of pumping. But, it is not beneficial to have a desirable accumulation state in the middle and later pumping stage, so it is difficult to obtain a higher comprehensive equilibrium height.

CFD Study on the Physical Behavior of Flue Dust in an Industrial-Scale Copper Waste Heat Boiler

The Flash Smelting Furnace (FSF) is one of the most common reactors for the primary smelting of copper concentrates. Its smooth operation depends on the availability and performance of the downstream Waste Heat Boiler (WHB). The WHB is especially sensitive to problems with its flue dust handling, such as the formation of accretions, which can lead to downtime and equipment failures. Due to the limited accessibility and the harsh conditions of the WHB, experimental studies are challenging. Therefore, CFD simulations can be a promising option to increase knowledge and evaluate a range of options. The present study investigates the physical behavior of flue dust in an industrial-scale WHB via a three-dimensional CFD model. Size-dependent particle sedimentation and the risk areas for flue dust accretions are predicted, finding good agreement with industrial experience and data from the literature. To make the evaluation of accretion risk zones possible, a new sticking function for flue dust is developed. The results are validated against dust samples. Finally, operational recommendations for minimizing flue dust accretions are derived.

Analysis of wear particles in used marine engine oils

В данной статье предпринята удачная попытка комплексирования магнитооптического метода и метода фотонной корреляционной спектроскопии для регистрации ферромагнитных частиц продуктов износа дизельного двигателя и определения их дисперсных характеристик. Такой подход позволяет фиксировать низкое содержание магнитных наноразмерных частиц и их дисперсность в отработанном судовом моторном масле, является новым и решает актуальную задачу. Выполнены эксперименты по наблюдению продольного магнитооптического эффекта Фарадея в модельной магнитной жидкости и в отработанном моторном масле. Показано, что низкая концентрация магнитных частиц в отработанном масле не позволяет наблюдать в нем эффект вращения плоскости поляризации в магнитном поле. Для измерения крупных частиц износа, смытых с фильтрующего элемента масляного фильтра, использовались закономерности процесса осаждения частиц в растворе и регистрация поглощения света, изменяющегося со временем. Полученные результаты позволяют получать важную информацию о состоянии и неисправностях деталей и механизмов двигателя по содержанию частиц износа в отработанном масле. In this article, a successful attempt has been made to combine the magneto-optical method and the method of photon correlation spectroscopy to register ferromagnetic particles of diesel engine wear products and determine their disperse characteristics. This approach makes it possible to record a low content of magnetic nanosized particles and their dispersion in used marine engine oil, is new and solves an urgent problem. Experiments on observation of the longitudinal magneto-optical Faraday effect in a model magnetic fluid and in used engine oil have been carried out. It is shown that the low concentration of magnetic particles in the waste oil does not allow observing the effect of rotation of the plane of polarization in a magnetic field. To measure large wear particles washed away from the filter element of the oil filter, we used the regularities of the process of particle sedimentation in solution and the registration of light absorption that changes over time. The results obtained make it possible to obtain important information on the condition and malfunctions of engine parts and mechanisms by the content of wear particles in the used oil.

Study and Analysis on the Influence Degree of Particle Settlement Factors in Pipe Transportation of Backfill Slurry

In this study, we developed a pipeline transport model to investigate the influence of particle sedimentation factors on slurry transportation through pipelines. The particle tracking module of the software was used to simulate the transport process, and the influences on the sedimentation rate were analyzed considering the slurry concentration, particle size, and flow velocity. The established model exhibited small calculation errors. In addition, the results revealed that the proposed model is reliable for calculating the degree of influence of various factors on particle sedimentation. The effect of the particle sedimentation rate on the pipeline slurry was explored considering the particle size, slurry concentration, and flow velocity. The sedimentation rate was positively related to particle size and adversely related to the slurry concentration and flow velocity. Indeed, study on the sedimentation rate requires considering a reasonable range of particle sizes, preparing a slurry with an appropriate concentration, and adjusting an appropriate flow velocity. Numerical simulations were performed using the filling data as the background for a sample mining area. The experimental results showed optimal slurry concentration and particle size of 60% and 25.25 µm, respectively.

Оn the Analysis of Certain Flotation Processes with Velocities Depending on Time and Height of the Column

— The present paper is an extension of the previous paper of the author where the flotation column dynamics has been investigated. Here we consider the case when particle sedimentation rate and bubble lifting speed depend on time and position in the column. We use the methods for examining the transmission lines set out in the papers mentioned in the References. We formulate a mixed problem for the system describing the processes in the column and present it in a suitable operator form. Then we prove an existence - uniqueness of generalized solution by the fixed point method. We show an explicit approximated solution as a step in the sequence of successive approximations.

Development and application of an integrated system of mathematical models for the transfer of radionuclides upon a hypothetic accident to minimize radioecological consequences

An integrated system of mathematic models is developed and implemented. The system is aimed at predicting the spread of the radioactive materials in the Arctic waters from a complex source distributed in space and time, formed by an emergency release of radionuclides from a nuclear-powered facility. Such approach allows taking into account various mechanisms of radionuclide transfer in arbitrary combinations. In addition to customary considered atmospheric and marine advection-diffusion processes with sedimentation on the underlying surface, it takes into consideration other mechanisms. Among them are particle sedimentation to the sea bottom with bottom capture, reverse process of washing-out from the bottom sediments. Specially attended is the Arctic-specific mechanism of particle ice-binding in the sea ice, drift of the frozen particles with ice, and their return to marine environment in result of ice thawing. The latter process may result in the appearance of the radioactive source at the large distance from the initial source and long time after the release event. The integrated model complex will provide the most realistic picture of the radioactive trace spread. It will sure be the effective tool for minimizing the emergency negative impact on the population and environment. The article a stage of long-term work that is currently ongoing.