Showing papers on "Multiphase flow published in 1986"

Determining multiphase saturations by NMR imaging of multiple nuclides

Abstract: The present invention provides a method for measuring fluid saturations during multiphase flow in porous media by NMR imaging of preselected nuclides in preselected fluids. For two-phase imaging, one of the fluids to be imaged may contain protons and the other fluid may contain fluorine. For three phase imaging, the third fluid contains neither protons nor fluorine. The radiofrequency transmitters and receivers may be alternated between proton and fluorine Larmor frequencies on sequential or interleaved imaging cycles. Proton and fluorine calibration standards may also be imaged with the sample and the nuclide signal intensities from the sample normalized to the respective proton and fluorine calibration standards. The saturation of two and three-phases may then be determined throughout the porous media. The porosity of a porous media may also be determined from the images of a calibration standard of a first fluid and the media saturated to one hundred percent with the first fluid.

Experimental and numerical analysis of two-phase infiltration in a partially saturated soil

Abstract: The purpose of this study is to analyze the effects of the soil air flow on the process of water infiltration in a 93.5 cm deep vertical column for varied boundary conditions at the surface - positive time constant head; time constant fluxes smaller and greater than saturated soil hydraulic conductivity. Several experiments conducted on a sandy soil column with and without a possible air flow through the wall are presented. Continuous and simultaneous measurements of water content and air and water pressure heads at different depths allow the analysis of the air and water movements within the soil and the determination of the capillary pressure and relative permeability for each phase as functions of the volumetric water content. A numerical solution of the equations describing the simultaneous flow of air and water is compared with the experimental data and with the traditional one-phase flow modeling. The results show that the air movement may significantly affect water flow variables such as infiltration rates, water content profiles, and ponding times. Furthermore, some basic assumptions used in two-phase flow modeling, such as the hydrodynamic stability of the wetting fronts and the pertinence of the relative permeability concept, are discussed in the light of the experimental data.

An Efficient Finite-Difference Method for Simulating Phase Segregation in the Matrix Blocks in Double-Porosity Reservoirs

Abstract: An efficient finite-difference method is presented for simulating unsteady-state multiphase flow in the matrix blocks (primary porosity) of naturally fractured systems or other reservoirs that have two different porosities. The scheme obtains pressure and saturation distributions in the matrix blocks (rather that average values) by dividing the matrix into subdomains. The method is an extension of the double-porosity concept in which fractures are the continuum for fluid flow and the matrix rock is the primary storage medium that acts as a source term to the fractures. Examples show that this subdivision results in different recoveries from the conventional double-porosity models when phase segregation in the matrix blocks is important to the recovery mechanism. In this formulation, the fracture medium is the major flow path to the wellbore with the matrix subdomains as source terms. The matrix subdomains can be connected to each other or to the fractures in any way desired to conform to the physics of the reservoir. This approach lends itself to an efficient scheme for reducing the system of flow equations to the same structure as conventional single-porosity simulators. The method is presented for a fully implicit, one-dimensional (1D), two-phase (oil/water) simulator.

Shearing motion of a fluid‐saturated granular material

Abstract: We discuss the application of a recently developed theory of multiphase mixtures to fluid‐saturated granular materials. The theory includes the incompressibility of each phase, but unlike other theories of the type, does not require pressure equilibrium between the phases. We do a theoretical study of the motion of this material in a viscometric simple shearing apparatus. It is shown that simple shearing generally does not occur. Typically, in the vicinity of a boundary, if the solid volume fraction is low, a layer of high shear rate occurs, while if the solid volume fraction is high, a ‘‘locking’’ phenomenon occurs. Otherwise, there is a tendency for particles to accumulate in regions of low shear rate.

Comprehensive modeling of a liquid rocket combustion chamber

Abstract: An analytical model for the simulation of detailed three-phase combustion flows inside a liquid rocket combustion chamber is presented. The three phases involved are: a multispecies gaseous phase, an incompressible liquid phase, and a particulate droplet phase. The gas and liquid phases are continuum described in an Eulerian fashion. A two-phase solution capability for these continuum media is obtained through a marriage of the Implicit Continuous Eulerian (ICE) technique and the fractional Volume of Fluid (VOF) free surface description method. On the other hand, the particulate phase is given a discrete treatment and described in a Lagrangian fashion. All three phases are hence treated rigorously. Semi-empirical physical models are used to describe all interphase coupling terms as well as the chemistry among gaseous components. Sample calculations using the model are given. The results show promising application to truly comprehensive modeling of complex liquid-fueled engine systems.

Wellbore Heat Transmission and Pressure Drop for Steam/Water Injection and Geothermal Production: A Simple Solution Technique

Abstract: This paper presents a straightforward iterative procedure for the wellbore heat transmission problem during upward or downward flow of a steam/water mixture. The mathematical model is taken directly from the literature and is based on material and momentum balances in the wellbore and a heat balance on the entire system including the surrounding media. The transient heat conduction equation is solved analytically by the application of successive Fourier and Laplace transforms. A simple superimpositioning in the time domain permits a matching procedure similar to multiphase flow calculations in pipelines. This is in contrast to standard numerical schemes that involve the direct solution of a set of algebraic and ordinary and partial differential equations typical of reservoir simulation. The pressure-drop calculations in the wellbore account for the slip concept and the prevailing flow regimes by means of standard two-phase correlations. The validity of the method is demonstrated by comparison with results of other numerical simulation studies and actual field data for both steam injection and geothermal production.

Capillary pressure discontinuities and end effects in homogeneous composite cores: Effect of flow rate and wettability

Abstract: The optimum construction methodology of composite cores for multiphase flow tests is an important practical petrophysical concern. The critical feature of construction is the minimization of saturation disturbances which occur due to capillary pressure discontinuities at individual core segment interfaces. The effect of matrix discontinuities on two-phase flow in homogenous composite cores was studied as a function of flow rate and wettability. Five composite cores, representing a range of wettabilities, were prepared. The composite cores were constructed by splicing multiple core segments with bridging materials of differing wettabilities. Saturation profile data we measured with a microwave saturation scanner during imbibition and drainage floods. The interface between core segments had a strong effect on the saturation distributions when capillary contact was not maintained between contiguous segments. Under drainage conditions at low flow rates, each core segment behaved as though it were an independent core experiencing a strong exit end effect. In steady-state fractional flow experiments this occurred only at fractional flows close to unity. The most effective bridging materials for water-wet Berea were thin paper sheets. No bridging material was found to be completely adequate in an oil-wet environment. In the absence of good capillary contact, increasing the flow rate ismore » a practical remedy for the saturation disturbances.« less

Simultaneous Measurements of Bubble and Liquid Velocities in Two-Phase Bubbly Flow Using Laser Doppler Velocimeter

Abstract: Simultaneous measurements of local velocities of both phases in a two-phase bubbly flow have been successfully made using a laser Doppler velocimeter (LDV). First, an exact theory which forms the basis of the velocity measurement of a large particle, such as bubble, has been derive and its validity has been applied to an air-water vertical bubbly flow. As a result, it has become evident that the measured value of a local slip velocity between bubble and liquid is lower than a terminal velocity of a single bubble rising in still water, and that the slip velocity gradually decreases with an increase in the mean liquid velocity.

Phase distribution for air-water two-phase flow in annuli

Abstract: Experimental data are presented on the phase distribution of air-water two-phase mixtures which flow vertically upwards in annular passages. Three annuli with different radius ratios, R1/R2 =5/13, 8/13 and 10/13, are used in the present experiments. Flow patterns observed in the annuli are first demonstrated. Next, two items characterizing void fraction distributions, i.e. void fraction near the wall and the position of the radius of maximum void fraction are discussed with attention paid to the effect of the passage width. Flow regimes concerned here-in cover bubbly, slug, froth and froth-annular or huge wave flow. Finally, an attempt is made to obtain a correlation for evaluating cross-sectional average void fraction. The proposed correlation is in good agreement with experimental values for both the annuli and a round tube.

Forces on the solid constituent in a multiphase flow

Abstract: I use a representation theorem of continuum mechanics, along with a systematic approximation, to establish an exact correspondence between the momentum interaction on the solid constituent in a multiphase flow, and the Stokes drag, the Faxen force, the Saffman lift, and the Ho and Leal lift on a particle in a viscous fluid.

Mechanism-Based Simulation of Oil Recovery Processes

Abstract: Accurately modeling recovery processes mathematically and simulating their performance numerically requires: (1) a consistent theory of capillary pressures, relative permeabilities, and dispersivities that characterize the flow and distribution of fluid phases, and (2) a flexible discretization of the governing equations that resolves the moving steep fronts that often develop. Recent advances in both are combined and applied to two-phase and three-phase displacements as in cores and reservoir streamtubes. Cases exemplifying one-dimensional displacement in various water-drives and gas drives are examined. Such simulations can be used to design and interpret laboratory measurement of flow properties and tests of process performance.

Detecting multiple phase flow in a conduit

Abstract: Multiple phase flow is detected and characterized in a fluid-containing conduit using a compressional wave acoustic transducer in the pulse-echo mode. The acoustic energy is transmitted in a transverse direction through the conduit and the returning echo is analyzed to determine if single or multiphase flow is present in the conduit.

Parameter Estimation for Distributed Systems Arising in Fluid Flow Problems via Time Series Methods

Abstract: The process of determining unknown parameter values, such as porosity and permeability, which are necessary for computer models for fluid flow processes is very complex. The difficulties arising from multiphase flow problems are even more severe. There are many different sources of error in the modeling process which lead to the distributed parameter systems and their computer solution. Use of time series methods addresses several of these sources of error, allowing efficient procedures for large-scale time dependent problems which can often reduce the difficulty of the enormous nonlinear optimization problems arising from many parameter estimation techniques.

Analysis of a multiphase, porous-flow imbibition experiment in fractured volcanic tuff

Abstract: A sub-meter-scale imbibition experiment has been analyzed using a finite element, multiphase-flow code. In the experiment, an initially dry cylindrical core of fractured volcanic tuff was saturated by contacting the ends with pressurized water. Our model discretely accounts for three primary fractures that may be present in the core, as indicated by measurements of porosity and saturation. We show that vapor transport has a small (less than 5%) effect on the speed of the wetting front. By using experimental results to estimate apparent spatial variations in permeability along the core, good agreement with measured, transient, saturation data was achieved. The sensitivity of predicted transient wetting fronts to permeability data indicates a need for more extensive measurements. We conclude that it will be difficult to characterize an entire repository - where inhomogeneities due to variations in matrix and fracture properties are not well known - solely from the results of sub-meter-scale laboratory testing and deterministic modeling. 16 refs., 8 figs., 1 tab.

Behavior of Solid Particles in a Radial-flow Pump Impeller

Abstract: Equations of motion of solid particles in a pump impeller having low specific speed were solved numerically with assumptions of an inviscid and incompressible quasi-three dimensional flow, and the general behavior of solid particles in the pump was clarified. The particle trajectories and forces acting on particles, the diameters of which range from 0.1 to 0.5 mm and the specific-gravities from 1.8 to 5.4 were obtained for different flow capacities. The locations and the velocities, with which the particles impinge on the boundary surface of the pump, were also discussed in order to predict the erosion damage in pumps.

Prediction of flow regime transitions in vertical upward three phase gas-liquid-solid flow

Abstract: The effect of solids concentration on the bubble to bubble-slug, bubble-slug to slug, and slug to churn flow transitions in gas-liquid-solid vertical flow has been studied using air, water, and glass beads in a 5 cm ID plexiglass column. Several simple models to predict the transitions were developed utilizing criteria proposed for gas-liquid vertical flow. These criteria are shown to apply equally well in the absence or presence of the solid phase With solids present in the flow, the bubble to bubble-slug and bubble-slug to slug flow transitions both occurred at lower superficial gas velocities because of increased bubble coalescence. However, the slug to churn flow transition was unaffected by solids in the range of flow conditions studied.

A Wastewater Treatment System Applying Aeration-Cavitation Flotation Mechanism

Abstract: A new type of wastewater treatment system applying not only aeration but also the cavitation flotation mechanism is proposed to attain high capacity and low operation cost. The system can be operated continuously in a single or multistage with ease. The system is composed of four isolated sections: feed section, aeration section, multiphase flow section, and separation section. Aeration and gas dissolution are carried out in the aeration section. Then collisions between the elements to be removed and gas bubbles, and cavitation of dissolved gas are accomplished in the multiphase flow section, followed by the recovery of the aggregates as the froth product in the separation section. The function of each section is evaluated by taking into consideration the contribution to the separation characteristics. It is confirmed through a series of treatment tests that the separation rate is a few tens of times faster than those in conventional treatment systems and, hence, lower energy consumption is antic...

Mass flow meter

Abstract: PURPOSE:To measure with a high accuracy a mass flow rate of gas or a multiphase flow containing gas, by dividing the inside of a tubular body by a face being orthogonal to the vibrating direction, making a fluid flow into this section and exciting it. CONSTITUTION:When a fluid flows and a tubular body 1 is driven like a simple harmonic motion in the Y-Y' direction, Coriolis force works. Accordingly, to the tubular body 1, a displacement quantity by Coriolis force is added against a simple vibration. The Coriolis force is detected as a phase difference by a displacement or a speed at the at time when the tubular body 1 passes through the neutral surface by a displacement detector or speed detectors 51, 52, which have been provided in the vicinity of both supporting bodies 3. A fluid to be measured is excited by a flow separating plate 102 together with the tubular body 1, but since an interval of each flow separating plate 102 is small, the fluid to be measured is excited by the same angular velocity and amplitude as those of the tubular body 1. In this way, a mass flow rate can be measured exactly.