Increase In Upstream Pressure Research Articles

Estimation of aggressive intensity of a cavitating jet with multiple experimental methods

An experimental study on the cavitating jet was conducted with emphasis placed on the detection of the energy that is emitted by the collapse of cavitation bubble. Four experimental methods, each respectively utilizing a hydrophone, an acoustic emission (AE) sensor, a laser Doppler vibrometer, and a polyvinylidene fluoride (PVDF) sensor, were compared. Aluminum specimens served as the target that would endure the impact of the cavitating jet. The mass loss was measured and the cumulative erosion rate was calculated. Various upstream pressures were used, and the effect of the cavitation number was considered as well. The results indicated that the cumulative erosion rate becomes maximum with the increase in the erosion time, and it is insensitive to variations in upstream pressure. The time span that is required for the cumulative erosion rate to reach its maximum value becomes shorter for high upstream pressures. An overall increase in the normalized energy is evident as the upstream pressure increases. At any given upstream pressure, the normalized energy varies inversely with the threshold level. The optimum threshold levels were obtained separately for each of the four methods. The correlation between the maximum erosion rate and the normalized energy was established statistically. The PVDF sensor proved to be the most effective instrument in estimating the aggressive intensity of the cavitating jet.

Combination of aquifer thermal energy storage and enhanced bioremediation: Biological and chemical clogging

Interest in the combination concept of aquifer thermal energy storage (ATES) and enhanced bioremediation has recently risen due to the demand for both renewable energy technology and sustainable groundwater management in urban areas. However, the impact of enhanced bioremediation on ATES is not yet clear. Of main concern is the potential for biological clogging which might be enhanced and hamper the proper functioning of ATES. On the other hand, more reduced conditions in the subsurface by enhanced bioremediation might lower the chance of chemical clogging, which is normally caused by Fe(III) precipitate. To investigate the possible effects of enhanced bioremediation on clogging with ATES, we conducted two recirculating column experiments with differing flow rates (10 and 50mL/min), where enhanced biological activity and chemically promoted Fe(III) precipitation were studied by addition of lactate and nitrate respectively. The pressure drop between the influent and effluent side of the column was used as a measure of the (change in) hydraulic conductivity, as indication of clogging in these model ATES systems. The results showed no increase in upstream pressure during the period of enhanced biological activity (after lactate addition) under both flow rates, while the addition of nitrate lead to significant buildup of the pressure drop. However, at the flow rate of 10mL/min, high pressure buildup caused by nitrate addition could be alleviated by lactate addition. This indicates that the risk of biological clogging is relatively small in the investigated areas of the mimicked ATES system that combines enhanced bioremediation with lactate as substrate, and furthermore that lactate may counter chemical clogging.

Experimental and applied analyses of particle migration in fractures of coalbed methane reservoirs

This study investigated the behaviors of particle migration within fractures of coalbed methane (CBM) reservoirs using laboratory simulation technology. Two coal samples were collected from Qinshui Basin (Shanxi Province, China) and used in two sets of permeation experiments, which were designed to understand the particle migration process and to determine the critical flux of particle migration. Based on those experimental results, a mathematical model was built to calculate the maximum water production of a CBM well that can be tolerated without damage to the reservoir. Permeation experiments indicate that as upstream pressure increases, the instantaneous permeability of coal samples have different behaviors that represent three distinct stages of non-permeation, particle migration, and stable permeation/particle blockage. In the particle migration stage, particles in the fractures start to migrate and then get deposited in narrower parts of the fractures — this migrating-deposition process repeats a few times. The permeability of the sample also repeatedly increases and then decreases. The migration and deposition of particles will cause a major decline in permeability, and for a working CBM well, this will damage the CBM reservoir. The critical fluxes of the two samples are 0.17 and 0.29 mL/min, and their permeability are 0.038 and 0.043 mD. When a well near sample QSC2 is chosen as an example, the calculated maximum water production during CBM drainage is 3.98 m3/d. This can be a recommended water production value for a real CBM well in the region that can avoid the damage of CBM reservoir.

Flow observations in elastic stenosis biomodel with comparison to rigid-like model

Plaques in blood vessels exhibit a wide range of stiffness depending on disease conditions: stiffness is an important factor in plaque behavior. The geometrical change in plaque based on its behavior can affect blood flow patterns. Thus, it is important to study both blood flow and deformation of plaques and blood vessels. This study aims to identify the differences in flow conditions between in vitro models to discuss experimental materials for arterial wall and flow observation. In order to observe the blood flow pattern and plaque deformation simultaneously, a PVA-H stenosis model was used. In addition, a silicone model was also used as a rigid-like model for comparison with the PVA-H model. PIV was employed to measure the flow velocity distribution and determine the flow levels in the models. PVA-H model exhibits expansion with an increase in upstream pressure and silicone model maintains the diameter. The expansion depends on their mechanical properties and influences flow conditions such as velocity changes and RAP in the parent artery. The balance between the expansion and change in flow conditions determines the final geometries of PVA-H model and flow pattern. The results suggest that the stiffness measurement for blood vessels and plaques such as ultrasound measurements would be important for accurate treatments.

G050073 円筒オリフィス内キャビテーションの過渡流れ特性

Cavitation inception and desinent behaviors in a cylindrical orifice under transient flow condition are observed using a high-speed video camera. Pressurized sample water with some conditions of air content is accelerated or decelerated by opening or closing of solenoid valve. Pressures upstream and downstream of test section, and the flow rate are measured simultaneously with high-speed video observation. The test orifice is made of transparent acrylic resin. The orifice has nozzle diameter of 1.6mm and throat length in 6mm without inlet roundness. As a result from observation, the time delay of cavitation inception becomes shorter with the increase in upstream pressure in the accelerated flow and longer with the decrease in air content. Growth rate of cavitation also becomes higher with the increase in upstream pressure. For the decelerating flow, cavitation desinence is delayed with the increase in upstream pressure.

Pressure Loss at the Bit While Drilling with Foam

Foam is one of the most frequently used drilling fluids at underbalanced drilling operations. As foam flows, due to the pressure drop, a volumetric expansion is observed, which causes the foam quality to increase in the same direction with flow. Flow of foams through circular pipes and annular geometries are well studied. Interestingly, although one of the major sources of pressure drop is at the bit, there have been few studies of this subject for foams. Many drilling parameters including hole cleaning capacity, volumetric requirements of liquid and gas phase, and backpressure are out of control if the pressure drop at the bit is not accurately determined, even though pressure drops inside the pipes and wellbore are properly determined. This article introduces a more accurate model for estimating the pressure drop of foam flowing through the bit. The major difference between the proposed and the existing models is that the proposed model includes the effect of foam expansion and velocity change as a function of pressure. Pressure drop has been observed to increase significantly as the upstream pressure and foam average velocity increases when compared with the existing models. For the same flow conditions, pressure drop decreases as the foam quality increases, and as the upstream pressure increases, pressure drop also increases. The existing models cannot detect this event at all. In some cases, the pressure drop at the bit can be 10 times greater than the pressure drop predicted from existing models.

Drill Bit Pressure Drop During Foam Drilling Operations

Abstract Foam is one of the most frequently used drilling fluids for underbalanced drilling operations. This paper introduces a more accurate model than the existing models for estimating the pressure drop of foam flowing through the drill bit. The major difference between the proposed and existing models is that the proposed model includes the effect of foam expansion and velocity change as a function of pressure. It has been observed that pressure drop increases significantly as the upstream pressure and foam average velocity increases. For the same flow conditions, pressure drop decreases as the foam quality increases, and as the upstream pressure increases, pressure drop also increases. These events cannot be detected by existing models. In some cases, the pressure drop at the bit can be 10 times greater than the pressure drop predicted by existing models. Introduction Foam has been used as a drilling fluid in many drilling operations; especially in underbalanced drilling applications. In a number of cases, drilling with foam has shown to provide significant benefits, including increased productivity (by reducing formation damage), increased drilling rate, reduced operational difficulties associated with drilling in low pressure reservoirs (e.g. lost-circulation and differentially stuck pipe) and improved formation evaluation while drilling. Foams consist of a continuous liquid phase, forming a stable cellular structure that surrounds and entraps a gas phase. Special chemicals, called surfactants, are used to capture the gas phase; at least for a desired period of time. Foams are considered to be dry or wet, depending on the gas content. Wet foams have spherical bubbles with large amounts of liquid between the bubbles. Dry foam bubbles are polyhedral in shape, with definite contact between the bubbles. In between these two extremes, geometrical figures having both curved and flat faces can exist. Foams are thermodynamically unstable systems because they always contain more than a minimal amount of gas solution interface(1). This interface represents surface free energy, the amount of which can be estimated from knowledge of the surface tension and the interfacial area of the foam. Wherever a foam membrane breaks and the liquid coalesces, there is a decrease in surface free energy. Thus, the decomposition of foam into its constituent phase is a spontaneous process. Since the solution phase is always denser than the gaseous phase, there is a strong tendency for the liquid to separate or drain from the main body of foam unless it is circulated or agitated in some way. Foams can have extremely high viscosity. In all instances, their viscosity is greater than either the liquid or the gas that they contain(2). At the same time, their densities are much lower than the density of water. They are stable at high temperatures and pressures. So, by using foam as a drilling fluid, its high viscosity allows efficient cuttings transport and its low density allows underbalanced conditions to be established; thereby minimizing formation damage. Foams are also preferred when water influx is a problem because they can handle large amounts of water.