Influence Of Pressure Difference Research Articles

Evaluation method for reservoir damage of cementing slurry

The damage of cement slurry to the reservoir is directly related to the production of oil and gas wells, and is a problem that must be solved for the efficient and economic development of oil and gas reservoirs. According to the characteristics and field conditions of reservoir damage caused by cement slurry, this paper analyzes the main factors affecting the degree of reservoir damage, puts forward the technical index requirements of the evaluation device, and establishes the evaluation method of reservoir damage caused by cement slurry in case of loss of injection. The results show that the influence of temperature on the damage of the cement slurry layer is small, and the influence of pressure difference on the damage to the cement slurry layer is large; When the pressure difference is 22 Mpa, the penetration damage rate caused by cement slurry to the pore center without mud cake attachment is about 43%. After a day of core maintenance, the permeability damage rate will reach 61.2%; The damage of cement slurry to the pore micro-fractured core is very serious. After 1 day of maintenance, the damage to the core permeability after cement slurry solidification is as high as 83%, with an average of 76.5%; When the risk of leakage is low, the cement slurry system with low density and low water loss can be used for cementing operation. The filtrate of cement slurry should be better matched with the formation clay minerals, formation water, and drilling fluid filtrate. When the risk of leakage is high, high-density cement slurry, balanced pressure cementing, pressure control cementing, and other technologies to avoid leakage can be used for cementing operations. When the cementing conditions are more difficult, the cementing slurry system can be used to dissolve the cementing slurry system at a later stage. The research results provide theoretical data support for the study of reducing the damage of cement slurry to the reservoir.

Investigation of pressure feedback technique to control ramp based SWBLI

Shock wave boundary layer interaction (SWBLI) and associated boundary layer separation create undesirable phenomena such as enhanced aero-thermodynamic loads, localized turbulent spots, unsteadiness, drag enhancement, pressure recovery losses in high-speed flow applications. It necessitates an investigation on the control of shock-induced boundary layer separation. Therefore, a pressure feedback technique (PFT) to control the boundary layer separation has been studied numerically on a two-dimensional flat plate and ramp configuration. PFT consists of a channel that drains fluid from the separated region and reintroduces it in the core flow under the influence of pressure difference. The effect of various freestream, wall, and geometric conditions on the separation controllability of the PFT is examined. It has been observed that PFT with injection located near the upstream influence point and suction at the ramp foot reduces the length of the separation bubble by 12.15%. Variation of injection location marginally affects the separation reduction capability of PFT, while the performance of PFT is greatly dependent on suction location. The parametric study noted that the optimum suction location, for which the separation size is minimum, shifts downstream with increasing freestream Mach number, wall temperature, and ramp angle. Again the optimum suction location shifts upstream as freestream stagnation temperature to wall temperature ratio increases. Reynolds number is seen to have no impact on the optimum suction location. Moreover, freestream stagnation temperature to wall temperature ratio, which is a governing parameter in SWBLI studies, is also a relevant factor in the mechanism of PFT. Finally, the present limited investigation revealed that the suction end of the PFT positioned between Xsu/L = 1.12 to 1.194 provides a minimum size of shock-induced separation for varying freestream and wall conditions.

Flow field characteristics of micro-scale textured surfaces of water-lubricated bearings using lattice Boltzmann method

PurposeThe purpose of this paper is to study the flow field characteristics of the micro-scale textured bearing surfaces using the lattice Boltzmann method based on the microscopic dynamics of the fluid.Design/methodology/approachConsidering the inertia effects and the micro-scale effects, the models of a single micro-scale texture unit cell with different shapes and different film thickness ratios are established. The influence of pressure difference between inlet and outlet of the unit cell on flow characteristics is studied.FindingsThe surface pressure distribution, flow patterns and pressure contours in the flow field are obtained. The results reveal that the pressure difference has a significant influence on the characteristics of the micro-textured flow field.Originality/valueThe results have certain guiding significance for further step investigation on microscopic lubrication mechanism of the water-lubricated polymer bearings.

The influence of pressure difference at the valve port of hydraulic throttle cone valve on the luminescence of hydraulic oil

In the hydraulic system, when the hydraulic oil flows through the valve port and the pressure difference between the front and back of the valve port is large, a large number of bubbles will be produced, and the phenomenon of luminescence of hydraulic oil may even occur. In this paper, the influence of the pressure difference before and after the port of the hydraulic throttle cone valve on the luminescence of hydraulic oil is studied using simulation analysis and experiments. It is found that, with the increase of pressure difference, the luminescence phenomenon of hydraulic oil becomes more obvious.

Aircore mechanism during draining based on influence of pressure difference and drain port diameter

An understanding of the mechanism of aircore phenomenon during draining is very important. In this study, numerical simulations were conducted for different pressurized and suction pressure water tanks, as well as for different drain port diameters, to explain and validate the proposed aircore mechanism. It was found that increasing the pressure at the top surface of the tank results in suppression of the aircore, whereas an increase in the suction pressure at the drain port outlet enhances the development of the aircore. For different drain port diameters, it was observed that the duration of the aircore during draining decreases with a decrease in the drain port diameter, and that the aircore is suppressed for a very small drain port diameter.

Manipulation of micro-objects using acoustically oscillating bubbles based on the gas permeability of PDMS.

This paper presents a novel manipulation method for micro-objects using acoustically oscillating bubbles with a controllable position based on the gas permeability of polydimethylsiloxane. The oscillating bubble trapped within the side channel attracts the neighboring micro-objects, and the position of the air-liquid interface is controlled by generating temporary pressure difference between the side channel and the air channel. To demonstrate the feasibility of the method in technological applications, polystyrene microparticles of 10 μm in diameter were successfully captured, transported, and released. The influence of pressure difference on the movement speed of the air-liquid interface was demonstrated in our experiments, and the manipulation performance was also characterized by varying the frequency of the acoustic excitation and the pressure difference. Since the bubble generation and the air-liquid interface movement in our manipulation method do not need any electrochemical reaction and any high temperature, this on-chip manipulation method provides a controllable, efficient, and noninvasive tool for handling micro-objects such as particles, cells, and other entities. The whole manipulation process, including capturing, transporting, and releasing of particles, spent less than 1 min. It can be used to select the cells and particles in the microfluidic device or change the cell culture medium.

Pressure Effects on the Kinetic Separation of Isopropyl Alcohol-Water Vapor Mixtures with FricDiff

Accurate experimental data are presented on the kinetic separation of isopropyl alcohol-water vapor mixtures with pure nitrogen as separating agent using FricDiff technology, which is based on differences in diffusion velocities of the mixture components in the separating agent. The influence of pressure differences over the macro-porous barrier on the separation process in a FricDiff module is studied under various operating conditions, including varying molar flow rate of the feed mixture, varying ratio between inlet molar flow rates of feed mixture, and separating agent and varying composition of the feed mixture. The experimental results are compared to data generated with a model. Because this work presents the first dataset where pressure differences are measured with sufficient accuracy, it is in fact the first rigorous comparison between FricDiff models and experiments. It is generally found that the trends observed in the experiments are well described by the model.

Discontinuous Meniscus Location in Tapered Capillaries Driven by Pressure Difference and Dielectrophoretic Forces

We calculate the meniscus location in tapered capillaries under the influence of pressure difference and dielectrophoretic forces with and without gravity. We find that the meniscus location can be a discontinuous function of the pressure difference or the applied voltage and that the meniscus can "jump" to one end or another of the capillary. Phase diagrams are given as a function of the pressure and voltage, depending on the geometrical parameters of the system. We further consider a revision of the dielectric rise under dielectrophoretic force in wedge capillaries and in the case of electrowetting, where the dielectrophoretic force is a small perturbation. Finally, we also find discontinuous liquid-gas interface location in the case of liquid penetration into closed volumes.

Flow Modeling in Negative-Pressure Infiltration Casting Process of Aluminum Open-Cell Fabrication

Aluminum open cell foam can be fabricated by negative-pressure infiltration casting process. In the process, pressure difference and surface tension are very important parameters, and greatly influence aluminum open cell structure formation. In this study a 3-D geometry unit that can be periodically extended to be an infinite CCP open cell was constructed. A numerical model including this unit and a series of proper boundary conditions was utilized to simulate the infiltration process using a commercial code. Influence of pressure difference, surface tension and turbulent flow on infiltration time was studied using this model. With pressure difference increasing from 1000 to 20000 [Pa], infiltration time is decreased from 0.0268 to 0.0100 [s]. Infiltration time is reduced from 0.0142 to 0.0115 [s] when surface tension is changed from 0.914 to 0[N/m]. The effect of turbulence is to reduce the infiltration time with 17.6%.

An open‐top chamber for measuring soil respiration and the influence of pressure difference on CO2 efflux measurement

1. A new open‐top chamber for measuring CO2 efflux from the soil is reported here. The new design enables measurement of the equilibrium CO2 efflux, when there is no detectable pressure difference between the chamber and outside nor leakage of CO2 into or out of the chamber. 2. In previous dynamic‐chamber techniques, the measured CO2 efflux is dependent on the pressure difference between the inside and outside of the chamber, and a negative pressure difference of –1Pa may cause an order of magnitude increase in measured CO2 efflux. Although the measured CO2 efflux is less sensitive to a positive pressure difference than to a negative one, a positive pressure difference of even a few tenths of a Pa will lead to a considerable underestimation in soil CO2 evolution. 3. The influence of pressure difference on measured CO2 efflux is negligible in the new design and the estimated CO2 efflux is close to the undisturbed soil respiration rate. Flow rates up to 8lmin–1, or air movement over the soil surface up to 55cmmin–1, will not affect CO2 evolution from the soil. The influence of pressure difference is related to the type of soil being measured and this has also been reported here for the new design.