Showing papers on "Multiphase flow published in 1995"

Recent advances in pore scale models for multiphase flow in porous media

Abstract: In the last decade, multi-phase flow in porous media has become a prominent topic in hydrologic research. This has been motivated by the widespread occurrence of subsurface contamination problems involving sparingly soluble liquids, often referred to as non-aqueous phase liquids (NAPLs). NAPL contamination problems require analysis of the simultaneous movement of at least two fluid phases, NAPL and water. This is somewhat different than the traditional multiphase flow problem in hydrology, namely water movement in unsaturated soils. In the traditional treatment of unsaturated systems, the movement of air, the non-aqueous phase, is not of interest, and its movement is ignored. Both NAPL-water and air-water systems are similar in that capillary forces, acting at the pore scale, usually dictate the pore-scale distribution of each fluid phase. Pore-scale fluid distributions then dictate the continuum-scale properties such as relative saturation and relative permeability.

Capacitance probe for fluid flow and volume measurements

Abstract: Method and apparatus for making measurements on fluids are disclosed, including the use of a capacitive probe for measuring the flow volume of a material within a flow stream. The capacitance probe has at least two elongate electrodes and, in a specific embodiment of the invention, has three parallel elongate electrodes with the center electrode being an extension of the center conductor of a co-axial cable. A conductance probe is also provided to provide more accurate flow volume data in response to conductivity of the material within the flow stream. A preferred embodiment of the present invention provides for a gas flow stream through a micro-gravity environment that allows for monitoring a flow volume of a fluid sample, such as a urine sample, that is entrained within the gas flow stream.

Non-Aqueous-Phase Fluids in Heterogeneous Aquifers—Experimental Study

Abstract: Understanding of flow and entrapment of non-aqueous-phase liquids (NAPLs) in aquifers contaminated with organic chemicals is important in the effective design of recovery and remediation schemes. Soil heterogeneities play a significant role in the physical behavior of these chemicals. An experimental facility consisting of a large soil tank (lysimeter) and a dual-gamma spectroscopy system for fluid saturation measurements was developed to simulate and monitor plume migration in water-table aquifers after chemical spills. Experimental techniques and results form a preliminary set of experiments conducted in unsaturated and saturated soils under homogeneous and heterogeneous conditions are presented. the effects of the layered homogeneities were pronounced in modifying the migration pattern and velocity of the plume. Pockets of coarse sand placed across the path of the plume resulted in the soil acting as a light NAPL trap. A fine-sand pocket acted as a barrier. Qualitative and quantitative data generated in the type of experiments presented in this paper can be used to validate multiphase flow models.

Photoluminescent volumetric imaging: A technique for the exploration of multiphase flow and transport in porous media

Abstract: A new measurement technique, photoluminescent volumetric imaging (PVI), has been developed for the visualization and quantification of multiphase flows and interface behavior in porous media. For this technique, a transparent, multiphase porous-medium system is constructed of optical-quality quartz sand, and two immiscible fluids matched to the optical refractive index of fused silica. Doping the fluids with property-selective fluorophores allows planar areas of the system to be successively excited with a shaped laser light to reveal the structure of the system. The resulting illumination is recorded by a high-resolution, cooled, slow scan charged-coupled device (CCD) camera. The planar digital images produced are then processed to generate a true three-dimensional data set that allows for quantitative study of the distribution of phases and interfaces within the porous medium. Sample volumes up to 125 mm³ in size with a resolution of better than 1 µm have been measured. Because of the large sample size and the high resolution of the measured data, geometric, flow, and phase interface information can be visualized and extracted at both subpore and system scales.

Accurate solution algorithms for incompressible multiphase flows

Abstract: A number of advances in modeling multiphase incompressible flow are described. These advances include high-order Godunov projection methods, piecewise linear interface reconstruction and tracking and the continuum surface force model. Examples are given.

Interfacial Heat Transfer Between Steam Bubbles and Subcooled Water in Vertical Upward Flow

Abstract: In two-fluid modeling, accurate prediction of the interfacial transport of mass, momentum, and energy is required. Experiments were carried out to obtain a data base for the development of interfacial transport models, or correlations, for subcooled water-steam bubbly flow in vertical conduits. The experimental data of interest included the interfacial area concentration, interfacial condensation heat transfer, and bubble relative velocity. In the present investigation, bubble condensation in subcooled water-steam flow in a vertical annulus at low flow rate and low pressure is investigated experimentally. A high-speed video system (up to 1000 frame/s) was used to visualize two orthogonal views of the flow simultaneously. A digital image processing technique was used to track and measure the velocity and size of the collapsing bubbles. The axial void fraction distribution was also measured by a single beam gamma densitometer.

Compositional and Black Oil Reservoir Simulation

Abstract: This paper describes a three-dimensional, three-phase reservoir simulation model for black oil and compositional applications. Both IMPES and fully implicit formulations are included. The model`s use of a relaxed volume balance concept effectively conserves both mass and volume and reduces Newton iterations. A new implicit well rate calculation method improves IMPES stability. It approximates wellbore crossflow effects with high efficiency and relative simplicity in both IMPES and fully implicit formulations. Multiphase flow in the tubing and near-well turbulent gas flow effects are treated implicitly. Initial saturations are calculated as a function of water-oil and gas-oil capillary pressures which are optimally dependent upon the Leverett J function or initial saturations may be entered as data arrays. A normalization of the relative permeability and capillary pressure curves is used to calculate these terms as a function of rock type and grid block residual saturations. Example problems are presented, including several of the SPE Comparative Solution problems and field simulations. 48 refs.

Accurate computation of convective transport in transient two‐phase flow

Abstract: SUMMARY The Van Leer method for the computation of convective fluxes is extended to two-phase flow. By preventing spurious undershoots and overshoots, the scheme preserves physical realism while maintaining high-order accuracy. This is particularly important for two-phase flows, since phase exchange terms are typically a function of volume fraction products and numerical diffusion can incorrectly mix the two phases. The scheme described here is constructed to guarantee that the sum of the volume fractions is always unity and that the volume fiactions are always greater than or equal to zero. Various test problems are computed to demonstrate the accuracy of the method and to show how the scheme might be incorporated in existing computational methods. In addition to multiphase flow applications, setting equal phase velocities results in a volume marker scheme that is well suited to single-phase interface tracking problems. There are few known exact solutions of the governing equations of two-phase flow and those that are known represent simple physical systems that have limited practical application. Consequently, investigators of two-phase flow fall back on experimentally determined correlations and more recently solutions of the governing equations obtained by computer. This paper addresses the problem of minimizing numerical diffusion associated with numerical representation of the convective terms in the two-phase governing equations. It is well known that numerical schemes that discretize the convective terms with an upwind procedure suffer from excessive numerical diffusion; the use of a higher-order scheme can substantially reduce this problem but can also lead to oscillations causing non-physical undershoots or overshoots. The implication of these results for two-phase flow calculations is particularly significant for the computation of the convection of phase volume fraction (mass). If an upwind procedure is used for volume fraction advection, then numerical diffusion tends to smear gradients of volume fraction. Typical two-phase exchange terms involve the product of volume fractions, so smearing produces finite values in those exchange terms, leading to numerically induced source terms and consequent inaccuracies throughout the calculation. If a naive higher-order scheme is used for volume fraction advection, then non-physical oscillations might appear in the volume fraction profiles, as well as overshoots or undershoots, so that volume fractions may be less than zero or greater than unity, which again would produce unphysical phase exchange source terms. This paper describes the use of the Van Leer method' for the computation of convective fluxes as applied to the convective transport of phase volume fraction (mass) and phase momentum in two-phase flow. The Van Leer scheme prevents spurious oscillations while maintaining a high order of numerical

Improved Computational Procedure for Retention Relations of Immiscible Fluids Using Pressure Cells

Abstract: The capillary pressure-saturation relation, or the capillary pressure head-volumetric fluid content relation, is of widespread interest in modeling and predicting multiphase fluid flow. A common procedure to determine this relation is to use a pressure cell and assume uniform distributions of capillary pressure and volumetric fluid contents at static equilibrium. The pressure cell method, however, yields inaccurate results for certain combinations of multiphase fluids and porous media. The sensitivity analysis in this study shows that the pressure cell height, the positions of the pressure measuring devices, which can coincide with the in- and outflow ports, and the relative density difference of the fluids, can give rise to considerable errors in the determination of capillary pressure head-volumetric fluid content relations by the standard procedure using pressure cells. We, therefore, propose a curve-fitting method that considers nonuniform distributions of capillary pressure and volumetric fluid content of multiphase fluids. The method uses the same input data as commonly used procedures.

Wave model for longitudinal dispersion: Development of the model

Abstract: A new 1-D model for longitudinal dispersion is proposed as an alternative to the Fickian-type dispersed plug-flow model. Accounting for significant features of longitudinal mixing gives rise to a quasilinear hyperbolic system of two first-order equations for the average concentration. The model equations are obtained based on minor extensions of the heuristic equilibrium analysis of Taylor. A qualitative, more general derivation of the equations is given on the basis of the simple generalization of Fick's law, taking into account the finite velocity of fluid elements. For linear problems the mean concentration and the dispersion flux obey a hyperbolic equation of the second order. The proposed hyperbolic model contains three parameters that depend only on the flow conditinos, the physical properties of the fluid, and the gemetry of the system. It effectively resolves the well-known problem of boundary conditions that, for unidirectional flow, are formulated now only at the reactor inlet. The new model eliminates the conceptual shortcomings inherent to the Fickian dispersed plug-flow model: it predicts a finite velocity of signal propagation and does not involve backmixing in the case of unidirectional flow.

The application of network modelling techniques to multiphase flow in porous media

Abstract: A review of the utility of network models is presented to describe multiphase flow at the pore-scale. Precise details of each set of simulations can be found in the appropriate reference and only the most pertinent results are presented here. The main aim of this paper is to highlight the effectiveness of network models as interpolative and interpretative numerical tools. Both primary and secondary capillary-dominated, two-phase displacements are considered and well-documented hysteresis effects are successfully reproduced. Waterfloods of mixed-wet media are subsequently described and associated variations in relative permeability and recovery efficiency reported. Optimum recovery is obtained from networks containing a 50-50 mix of oil-wet and water-wet pores. Finally, a discussion of unsteady-state drainage and imbibition models follows and these are applied to waterfloods in finely-laminated porous media. Results highlight the complex interactions between capillary forces, viscous forces and geological structure.

Surface Network and Well Tubinghead Pressure Constraints in Compositional Simulation

Abstract: A new procedure for the determination of well production rates from surface pipeline network and well tubinghead pressure constraints is presented. The well production rates are calculated using simultaneous modeling of multiphase fluid flow in the reservoir, well perforations, well tubing strings, and surface pipeline network system. The procedure is implemented in an industrial compositional reservoir simulator. It is applicable for both black-oil and compositional reservoir simulations.

The Development of Laboratory Correlations Showing the Impact of Multiphase Flow, Fluid, and Proppant Selection Upon Gas Well Productivity

Abstract: This paper describes the development and use of laboratory data to show the impact of multiphase, non-Darcy flow upon gas production from hydraulic fractures In the work, the impact of proppant type and fracturing fluid damage upon non-Darcy flow and effective conductivity vs closure, temperature and gas/water/oil ratios is shown for sands, resin-coated sands and ceramics with various fracturing fluids Laboratory derived correlations are then used to predict gas productivity and economics under various conditions of multiphase non-Darcy flow and the predictions are compared to field examples The results of the testing show that multiphase non-Darcy flow dramatically increases the difference between the effective conductivities of various proppants at high closures The laboratory data and field observations show that when this is taken into account, a premium proppant can show twice the production rate of commonly used sand products at high closures in gas wells producing as little as 10 barrels of water or condensate per MMCF

The interaction of a moving fluid/fluid interface with a flat plate

Abstract: A well-known technique for metering a multiphase flow is to use small probes that utilize some measurement principle to detect the presence of different phases surrounding their tips. In almost all cases of relevance to the oil industry, the flow around such local probes is inviscid and driven by surface tension, with negligible gravitational effects. In order to study the features of the flow around a local probe when it meets a droplet, we analyse a model problem: the interaction of an infinite, initially straight, interface between two inviscid fluids, advected in an initially uniform flow towards a semi-infinite thin flat plate oriented at 90° to the interface. This has enabled us to gain some insight into the factors that control the motion of a contact line over a solid surface, for a range of physical parameter values.The potential flows in the two fluids are coupled nonlinearly at the interface, where surface tension is balanced by a pressure difference. In addition, a dynamic contact angle boundary condition is imposed at the three-phase contact line, which moves along the plate. In order to determine how the interface deforms in such a flow, we consider the small- and large-time asymptotic limits of the solution. The small-time and linearized large-time problems are solved analytically, using Mellin transforms, whilst the general large-time problem is solved numerically, using a boundary integral method.The form of the dynamic contact angle as a function of contact line velocity is the most important factor in determining how an interface deforms as it meets and moves over the plate. Depending on this, the three-phase contact line may, at one extreme, hang up on the leading edge of the plate or, at the other extreme, move rapidly along the surface of the plate. At large times, the solution asymptotes to an interface configuration where the contact line moves at the far-field velocity.

Formation Invasion:: With Applications to Measurement-While-Drilling, Time Lapse Analysis, and Formation Damage

Abstract: Fluid Mechanics of Invasion. Modeling Static Filtration. Dynamic Filtration and Borehole Flow Modeling. Quantitati ve Method s for Tim e Lapse Analysis. Complex Invasion Problems. Numerical Modeling. Forward and Inverse Multiphase Flow Modeling. Special Topics:

An experimental investigation of interfacial instability in superposed flow of viscoelastic fluids in a converging/diverging channel geometry

Abstract: The interfacial stability of superposed flow of polypropylene (PP) and high-density polyethylene (HDPE) in a converging-diverging channel geometry is experimentally investigated. Using the apparatus and procedures developed in our previous study [20], we have investigated the role of base flow kinematics on the interfacial stability of the HDPE/PP system. A comparison of experimentally determined neutral stability contours and disturbance growth rates in parallel, converging and diverging channel flows has revealed that channel convergence tends to stabilize interfacial disturbances while channel divergence has a destabilizing influence. Moreover, we have shown that the most dangerous wave number when made dimensionless with respect to the thickness of the more elastic and/or viscous component is of 0(1). In addition, based on a simple analysis, we have shown that the mechanism of interfacial instability in two-layer viscoelastic flows is due to the coupling between the perturbation velocity field and the polymeric stress gradient in the base flow.

Virtual Measurement in Pipes, Part 2: Liquid Holdup and Flow Pattern Correlations

Abstract: The prediction of liquid holdup and multiphase flow regimes present in a well or pipeline is very important to the petroleum industry. Liquid holdup, defined as the fraction of pipe occupied by liquid, and flow regimes must be predicted to design separation equipment and slug catchers in pipeline operations properly. It is also important when designing gas storage fields in depleted oil reservoirs.

Determination of the watercut of a multiphase flow directly from measured microwave frequency dielectric properties

Abstract: The watercut of fluid in a mulitphase flow is measured. Microwave energy in the 10 Ghz range is transmitted through a test call having flow passing therein through a known geometry. Attenuation and phase shift of the microwave energy is measured and used to derive the wave number of the microwaves in the unknown fluid. The water fraction of the unknown fluid is then determined from the wave number and the known geometry of the test all using Hannai's equation.

Dynamics of concentration and vorticity modification in a cellular flow laden with solid heavy particles

Abstract: The processes of the accumulation of solid heavy particles settling under gravity and modification of the carrier flow are studied analytically and numerically. The dilute limit is considered when the effects of particle–particle interactions are neglected. The flow Reynolds number is assumed to be large enough to disregard effects related to the viscous dissipation. Particles with a small Stokes (St) number are considered, when approximate solution for the particulate velocity in the form of a series in St can be derived.Analytical solutions are obtained for initially uniform distribution of particles in a cellular flow (formed by a lattice of two‐dimensional vortices with different circulations) describing dynamics of the particulate concentration and corresponding modification of the fluid flow. Two different regimes of large and moderate flow Froude number (Fr) are considered. Solutions obtained show that in the first case (Fr≫1), when the gravitational settling of the particles is insignificant, the ...

Electronic wellhead apparatus for measuring properties of multiphase flow

Abstract: A system for producing hydrocarbons from a subterranean reservoir, the system including a multiplicity of wells producing hydrocarbons through flow lines, sensor units attached to each of the wells for monitoring hydrocarbon flow through the flow lines, and a portable electronics unit for operating the multiplicity of sensor units.