It is generally admitted that experimental data obtained in “laboratory-scale” bubble columns are representative of “industrial-scale” reactors if the well-known three “Wilkinson et al. scale-up criteria” are satisfied: (a) the diameter of the bubble column is larger than 0.15 m, (b) the sparger openings are larger than 1-2 mm and (c) the aspect ratio is larger than 5. The aim of this communication is to contribute to the existing discussion. To this end, this communication collects relevant experimental investigation and include new experimental data: in particular, we have experimentally studied the combined effect of the aspect ratio (within the range of 1-15) and the sparger design (considering both “coarse” and “fine” spargers) on the gas holdup in a large-diameter and large-scale gas-liquid bubble column. The bubble column has been operated both in the batch mode and in the counter-current mode. Filtered air has been used as the gaseous phase in all the experiments, while the liquid phase has included deionized water and different aqueous solutions of organic (i.e., ethanol) and inorganic (i.e., sodium chloride, NaCl) active agents. It is found that the “Wilkinson et al. scale-up criteria” are valid for the air-water case in the batch mode for “very-coarse” spargers. Conversely, they are no more valid when considering different liquid velocity, and/or aqueous solutions of active agents, and other sparger openings.

Micromodel flooding is a cost-effective method to investigate enhanced oil recovery. In this study, we apply Lauryl Betaine as an amphoteric surfactant to the injected fluids into the micromodel and compare the results with conventional EOR techniques such as water flooding, solvent flooding, and microemulsion flooding. First, we determined the optimal flow rate of injected fluid into the micromodel to represent fluid flow in the formation. Next, we did water flooding with varying salinities. Next, we did solvent flooding with two different ratios of solvents. Condensate and hexane are the solvents we applied. Next, we did surfactant flooding using Lauryl Betaine. Surfactant flooding tests are conducted using different salinity and surfactant concentration (C_s). Finally, we did microemulsion flooding. The results show that surfactant flooding at high salinity using Lauryl Betaine leads to highest oil recovery among all tested EOR methods. Besides, the results indicate that addition of Lauryl Betaine to the injected brine leads to higher breakthrough time (BT).

In the transport of gas-liquid mixtures, where the amount of liquid condensate is low, a stratified flow-pattern is predicted by mechanistic two-phase flow models. In this case, the momentum balance between liquid and the gas phases is the key relation for the calculation of the steady state flow equilibrium and the existing liquid hold-up. The latter value is particularly important at low production rates for pipelines with a large number of upward and downward inclined pipe segments (making V shaped sections) where liquid can easily accumulate in the lower parts. The error in predicting the liquid inventory has critical consequences on the evaluation of the total pressure drop along the pipeline. The results obtained from steady state simulation can be far from reality or, at least, cannot be reproduced by a dynamic simulation of the same operating conditions. These topics are analysed using a multiphase flow simulator developed by the Author (XPSIM, eXtended Process SIMulation) which can perform compositional and fluid-mechanical analysis at the same time. Steady state and dynamic simulations are developed for the Ormen-Lange pipeline (about 120 km long): large differences are found between the steady state and dynamic solutions.

Slug catcher is an important and costly equipment in the up-stream assets, but is the less Supported by research or commercial simulation software in terms of design and sizing criteria.

The purpose of this paper is to present a simulation model based on the open-source software for computational fluid-dynamics OpenFOAM^®, which can assist during the preliminary sizing, made by the usual simplified methods, proving the fluid-dynamic behaviour and drive the process engineers to an optimum final design by checking all the expected production profiles of the related oil/gas field, for a comprehensive and safe operation all along the reservoir life.

The slug catcher main function is to ensure the separation of the phases within the acceptance specifications dictated by the process units of downstream CPF (Central Production Facility).

The optimization of the slug catcher could allow the reduction of the equipment overall dimensions, that is essential to reduce the capital expenditure and make the installation more flexible.

The graphic output is a strong tool in the hand of engineers, following the fluid-dynamic response of the slug catcher in the gas-liquid separation section, in function of the flow pattern at the entrance and superficial velocities of the phases.

A precise prediction of the fluid dynamics in bubble columns is of Fundamental importance to correctly design “industrial-scale” reactors. It is known that the fluid dynamics in bubble columns is related to the prevailing bubble size distribution existing in the systems. In this respect, multiphase computational fluid dynamic simulations, in the Eulerian multi-fluid framework, are able to predict the local bubble size distributions and, thus, the global fluid dynamics from the fluid flow conditions and by applying modeling closured. In particular, in in “industrial-scale” reactors, owing to the large gas sparger openings, the “pseudo-homogeneous” flow regime—characterized by a wide spectrum of bubble sizes—is typically observed. Unfortunately, reliable predictions of the “pseudo-homogeneous” flow regime are limited up to now: one important drawback concerns the selection of appropriate models for the coalescence and break-up. A set of closure relations was collected at the Helmholtz-Zentrum Dresden-Rossendorf that represents the best available knowledge. Recently, the Authors have extended the validation of this set of closure relations to the “pseudo-homogeneous” flow regime, by comparing the numerical predictions to a comprehensive experimental dataset (gas holdup, bubble size distributions and local flow measurements). Unfortunately, the previous study suffers from some limitations; in particular, in the previous experimental dataset, the bubble size distributions concerned only one axial position and a detailed characterization of the gas sparger was missing. This study contributes to the existing discussion and proposed a step ahead in the study of the “pseudo-homogenous” flow regime. To this end, we propose an experimental study, to improve the comprehensive dataset previously obtained. The novel dataset—obtained for two gas velocities—concerns bubble size distributions at different axial and radial positions and a precise characterization of the gas sparger. The comprehensive bubble size distribution dataset may serve as basis to improve the coalescence and break-up closures; conversely, the precise characterization of the gas sparger served as an improved input to the numerical simulations. The numerical results, with two different lift force implementations, have been compared with the whole dataset and have been critically analyzed. Reasons for the discrepancies between the numerical results and the experimental data have been identified and may serve as basis for future studies.

An inherent problem with both oil and natural gas production is the deposition of sand particles in pipeline, which could lead to problems such as excessive pressure drops, equipment failure, pipeline erosion, and production decline. The characterization of sand particles transport and sedimentation in different flow systems such as sand-multiphase mixtures is vital to predict the sand transport velocity and entrainment processes in oil and gas transportation pipelines. However, it seems that no model exists able to accurately characterize the sand transport and deposition in multiphase pipeline. In fact, in the last decade several researchers tried to extend the modeling of liquid-solid flow to gas-liquid-solid flow, but no significant results have been obtained, especially in slug flow condition due to the complexity of the phenomenon. In order to develop and validate a mathematical model properly formulated for the calculation of the sand critical deposition velocity in gas-liquid flow, more and more experimental data are necessary. This paper presents a preliminary experimental study of three phase flows (air-water-sand) inside a horizontal pipe and the application of the sand-liquid models present in literature. Significant observations were made during the experimental study from which several conclusions were drawn. Different sand flow regimes were established by physical observation and data analysis: fully dispersed solid flow, moving dunes and stationary bed. The critical deposition velocities were determined at different sand concentrations. It was concluded that sand transport characteristics and the critical deposition velocity are strongly dependent on the gas-liquid flow regime and on sand concentration.

Previous work showed that a one-dimensional, hyperbolic, transient five-equation two-fluid model can predict automatically the formation, growth, and subsequent development of slugs in horizontal and near-horizontal flow. This method was implemented in a finite volume numerical scheme -called 5ESCARGOTS code. Comparison with experimental data showed that it can be used to predict the flow pattern and statistical characteristics (slug velocity, length, and frequency). However, the capabilities of this approach have been tested only for water-air flows in a straight horizontal pipe.

In this work, we validate the application of the code to some unconventional problems. Firstly, we test the possibility of slug capturing approach to describe and predict the relevant features of air/high viscosity oils or air/non-Newtonian fluids flows. Comparisons between some slug characteristics and empirical correlations, available in literature, are discussed. Then, we move from simple geometries toward more complex conditions that may be representative of actual application cases, also employing high viscous oils as liquid phase. Comparison against experimental data shows results in reasonable agreement.

Gas-liquid separation is a very common process in industrial plants, where often high Efficiency of Gas Separation (EGS) is demanded. In the upstream oil industry, gas separation is also crucial for the proper operation of Electrical Submergible Pumps (ESP). Recent studies report the excellent performance of a gravitational separator known as Inverted-Shroud separator (IS-separator). Laboratory results indicate that this kind of separator can achieve total gas separation for a wide range of operation conditions under continuous two-phase flow. The original intent is to use the IS-separator for downhole gas separation in oil production wells. However, by account of its simple design and relatively compact size, it may be suitable for using in industrial plants. In this paper, we present the IS-separator in details, including geometry characteristics and phenomenology. The equipment performance is also discussed. In addition, the challenges related to the deep understanding of the gas separation process inside the IS-separator and the possible practical solutions are outlined.

In petroleum development, low-permeability reservoir means having permeability of porous media lower than 50 micro-Darcy. The mathematical model of liquid flow in low-permeability reservoirs has been difficult to describe for a long time, and an ideal model has not been available until now because of the threshold pressure gradient. With the boundary adhesion layer model of a micro-channel as basis, a new liquid flow model was derived for low-permeability reservoirs in this study. The no-movement liquid layer close to the solid surface was defined as the boundary adhesion layer regarded as the negative slip length. Using the exponential function of the boundary stick layer to the pressure drop gradient, the formulae of the liquid velocity and flow rate of a round channel were derived. The liquid flows model in low permeability reservoirs was then obtained. Finally, the flow model was tested by examples, and applications to a low-permeability reservoir were demonstrated. The analysis results show that the new non-linear model of liquid flows exhibits clear physical definition, and can be easily used to describe liquid flows in low-permeability media.

In a previous work it has been shown that a one-dimensional, hyperbolic, transient five equations two-fluid model is able to numerically describe stratified, wavy, and slug flow in horizontal and near-horizontal pipes. Slug statistical characteristics can be numerically predicted with results in good agreement with experimental data and well-known empirical relations. In this model some approximated and simplified assumptions are adopted to describe shear stresses at wall and at phase interface.

In this paper, we focus on the possibility to account for the cross sectional flow by inserting shape factors into the momentum balance equations of the aforementioned model. Velocity profiles are obtained by a pre-integrated model and they are computed at each time step and at each computational cell. Once that the velocity profiles are known, the obtained shape factors are inserted in the numerical resolution. In this way it is possible to recover part of the information lost due to the one-dimensional flow description.

Velocity profiles computed in stratified conditions are compared against experimental profiles measured by PIV technique; a method to compute the velocity profile during slug initiation and growth has been developed and the computed velocity distribution in the liquid phase was compared against the one-seventh power law.

An experimental study has been made of oil-water core-annular flow in a horizontal pipe with special attention for the influence of the oil viscosity on the pressure drop. For that purpose a heating system has been installed and configured that is able to control the oil temperature, such that the oil viscosity could be varied between 3000 cSt at 20 °C and 400 cSt at 50 °C. The oil flow rate was kept at a constant value of 0.35 l/s, whereas the watercut was varied between 9% and 25%. The measured pressure drop is scaled with the calculated pressure drop of only oil flowing at the same flow rate and viscosity.

The main conclusion is that for a large oil viscosity the scaled pressure drop is almost independent of the watercut, whereas with decreasing viscosity the scaled pressure drop becomes strongly dependent on the watercut. Visualisation of the oil-water interface shows a more irregular wave shape with smaller wave lengths when the viscosity is decreased. There is very good agreement between the predictions of the model of Ullmann & Brauner for the scaled pressure drop and the measurements.

This paper presents the results of a sensitivity study carried out to investigate the performances of two commercial codes, OLGA and LedaFlow, used to model the wax deposition process in pipelines under multiphase flow. Reliable simulations of the phenomenon are essential to properly design pipelines and to adopt cost-effective strategies for prevention and removal of wax deposits, reducing the risks of blockage. The main limit of the available models is that their predictions depend on a number of parameters which are usually adjusted to fit the experimental data obtained from laboratory deposition tests. Since a reliable upscale criterion has not been developed yet, model predictions have been more suitably validated using real field data, reported in literature. The performances of the commercial codes in modelling wax precipitation and deposition have been compared to each other.