Oscar M. H. Rodriguez

Flow patterns in heavy crude oil-water flow

This paper is aimed to an experimental study on the flow patterns formed by heavy crude oil (initial viscosity and density 488 mPa s, 925.5 kg/m 3 at 20°C) and water inside vertical and horizontal 2.84-cm-i.d. pipes. The oil-water interfacial tension was 29 dyn/ cm. Effort is concentrated into flow pattern characterization, which was visually defined. The similarities with gas-liquid flow patterns are explored and the results are expressed in flow maps. In contrast with other studies, the annular flow pattern (core annular flow) was observed in both horizontal and vertical test sections. These flow pattern tends to occur in heavy oil-water flows at low water input fractions. Because of the practical importance of core flow in providing an effective means for heavy oil production and transportation, this paper discusses criteria that favor its occurrence in pipes.

Phase fraction distribution measurement of oil-water flow using a capacitance wire-mesh sensor

In this paper, a novel wire-mesh sensor based on permittivity (capacitance) measurements is applied to generate images of the phase fraction distribution and investigate the flow of viscous oil and water in a horizontal pipe. Phase fraction values were calculated from the raw data delivered by the wire-mesh sensor using different mixture permittivity models. Furthermore, these data were validated against quick-closing valve measurements. Investigated flow patterns were dispersion of oil in water (Do/w) and dispersion of oil in water and water in oil (Do/w&w/o). The Maxwell–Garnett mixing model is better suited for Dw/o and the logarithmic model for Do/w&w/o flow pattern. Images of the time-averaged cross-sectional oil fraction distribution along with axial slice images were used to visualize and disclose some details of the flow.

Film thickness planar sensor in oil-water flow: prospective study

Purpose – The purpose of this paper is to study a multiphase-flow instrumentation for film thickness measurement, especially impedance-based, not only for gas–liquid flow but also for mixtures of immiscible and more viscous substances such as oil and water. Conductance and capacitive planar sensors were compared to select the most suitable option for oil – water dispersed flow. Design/methodology/approach – A study of techniques for measurement of film thickness in oil – water pipe flow is presented. In the first part, some measurement techniques used for the investigation of multiphase flows are described, with their advantages and disadvantages. Next, examinations of conductive and capacitive techniques with planar sensors are presented. Findings – Film thickness measurement techniques for oil–water flow are scanty in the literature. Some techniques have been used in studies of annular flow (gas–liquid and liquid–liquid flows), but applications in other flow patterns were not encountered. The methods ba...

Water-assisted Flow of Heavy Oil in a Vertical Pipe: Pilot-scale Experiments

The use of the core-annular flow pattern, where a thin fluid surrounds a very viscous one, has been suggested as an attractive artificial-lift method for heavy oils in the current Brazilian ultra-deepwater production scenario. This paper reports the pressure drop measurements and the core-annular flow observed in a 2 7/8-inch and 300 meter deep pilot-scale well conveying a mixture of heavy crude oil (2000 mPa.s and 950 kg/m3 at 35 C) and water at several combinations of the individual flow rates. The two-phase pressure drop data are compared with those of single-phase oil flow to assess the gains due to water injection. Another issue is the handling of the core-annular flow once it has been established. High-frequency pressure-gradient signals were collected and a treatment based on the Gabor transform together with neural networks is proposed as a promising solution for monitoring and control. The preliminary results are encouraging. The pilot-scale tests, including long-term experiments, were conducted in order to investigate the applicability of using water to transport heavy oils in actual wells. It represents an important step towards the full scale application of the proposed artificial-lift technology. The registered improvements in terms of oil production rate and pressure drop reductions are remarkable.

A high spatial and temporal resolution film thickness sensor in oil - water flows

This work presents a study of a new technique for non-intrusive measurement of liquid-liquid flow. The evaluated film thickness sensor has 64 × 16 measuring points and a measuring area of 128 × 32 mm. This sensor measures the electrical conductance and, through a calibration procedure, converts those signals in water film thickness. The experimental work was carried out in the Swiss Federal Institute of Technology Zurich (ETHZ) in Zurich, Switzerland.

Holdup estimation in core flow using image processing

In this work holdup is estimated through image processing and compared with the value calculated indirectly by the correlation presented by Rodriguez et al. in [1]. The tests were performed in the multiphase-flow test facilities of the Research Centre (CENPES) of PETROBRAS, Brazil. Flow images were obtained with a high-speed video camera at 1000 fps in a 2 7/8-inch and 300 meter deep pilot-scale well, conveying a mixture of heavy crude oil (2000 mPa.s and 95 0 kg/m3 at 35 °C) and water at several combinations of the individual flow rates. In total, four tests were carried out with 100 images each.

An Exploratory Experimental Technique to Predict Two-Phase Flow Pattern From Vibration Response

Gas-liquid pipe flow is common in nuclear, gas & oil, refrigeration and power generation industries, where gas-liquid mixtures are transported in piping systems. The mixtures flows in different flow patterns, such as bubbly, slug and annular, generating dynamic fluid forces which may induce structural vibration. In many industrial cases, Flow-Induced Vibrations (FIV) are an intrinsic part of the piping operation and does not present risks that may lead to structural component failures. In this sense, the information available on this topic is quite scanty. In this paper, we present an in-depth discussion about the phenomenology of the FIV due to two-phase pipe flow. A set of 32 two-phase horizontal flow conditions was collected, including bubbly, slug and dispersed flow-patterns. The homogeneous mixture velocity J was in the range of 0.5 to 25 m/s, with homogeneous void fractions of β = 10%, 25%, 50%, 75% and 95%. Signals of acceleration were acquired to correlate pipe vibration and two-phase flow parameters. Results show higher acceleration levels in slug and dispersed than in bubbly flow. We find that the acceleration frequency response contains useful information of the flow. Comparisons with single-phase flow are also presented. Finally, an exploratory experimental technique to predict two-phase flow pattern from vibration response based on the combination resonance caused by both single and two-phase flow is proposed. The results indicate that the proposed-technique is acceptable to recognize intermittent flow patterns in two-phase flow.Copyright

Special issue dedicated to the Second Brazilian Conference on Boiling, Condensation and Multiphase Flow, São Carlos, Brazil, 03-07 May 2011

It gives us great pleasure to present this special issue highlighting some of the papers presented at the Second Brazilian Conference on Boiling, Condensation and Multiphase Flow held at the University of Sao Paulo (USP), in Sao Carlos, Brazil, May 03-07, 2011. The event was part of the First Multiphase Flow Brazilian Journey and was jointly cosponsored by PETROBRAS and Sao Paulo Research Foundation (FAPESP). The conference was built on the success of the previous meetings held in Florianopolis in the State of Santa Catarina, southern Brazil. As before, the objective of the conference was to give scientists, engineers and students from Brazil as well as from other countries, an opportunity to get together for the dissemination of the state-of-the-art and recent advances in the field and to enhance future collaborative research activities between them. More than 100 scientists participated in the event. The program of the First Multiphase Flow Brazilian Journey included seven invited keynotes, twelve lectures by Brazilian specialists and thirty four oral presentations of research papers. The invited keynotes were delivered by worldwide leading researchers in their field as Prof. Akio Tomyiama from Kobe University, Prof. Gretar Triggvasson from Worcester Polytechnique Institute, Prof. John R. Thome from Ecole Polytechnique Federale de Lausanne and Profs. Rene Oliemans and Luis M. Portela from Delft University. All research papers were reviewed on full manuscripts by external reviewers and collected together in a CD. Contributed papers have been sorted in sessions on measurement techniques, two-phase flow without phase change, boiling and condensation, multiphase flow fundamentals, CFD and two-phase flow applications. The twelve lectures on fundamental aspects of multiphase flows are published together in a book. This special issue of Journal of the Brazilian Society of Mechanical Sciences and Engineering presents a selection of eight papers presented in the conference. The topics covered include film fraction measurements in a Venturi scrubber, superficial void fraction measurements by using the wire-mesh technique, statistical characterization of the two-phase slug flow in a horizontal pipe, flow boiling in micro-scale channels, a comparison between numerical and experimental results for natural circulation in nuclear reactors and a discussion on the main criterion to determine the transition region from stratified flow to slug or roll-waves and a paper that presents a literature review on two-phase flow pressure drop and heat transfer during flow boiling in tubes containing twisted-tape inserts and the development of a new correlation to predict pressure drop in tubes containing such devices. The volume contains also a kind contribution of Prof. Rene Oliemans in which the author presents a comprehensive state-of-the-art review on two- and three-phase oil/water/gas flows in horizontal and inclined pipes addressing the relevant flow-pattern-dependent model capabilities to compute oil/water pressure loss and hold-up. This review concludes with an outlook on future research directions in this field. Finally, we thanks to all members of the organizing committee, conference delegates, keynote speakers, referees, and authors for their work in ensuring that the Second Brazilian Conference on Boiling, Condensation and Multiphase Flow and the First Multiphase Flow Brazilian Journey were a success. In particular we thank PETROBRAS and the Brazilian Society of Mechanical Sciences and Engineering who have sponsored this special issue.

High spatial and temporal resolution film thickness planar sensor: comparison of geometries

The purpose of this paper is to study planar sensor geometries for the measurement of film thickness in a viscous oil–water flow. The study is relevant due to there are only a few measurement techniques for oil-water flow and these techniques involve oil with low viscosity (close to the water viscosity). Specifically, some techniques have been used in the studies of annular flow (gas–liquid and liquid–liquid flows), but applications in other flow patterns were not encountered.,Different sensor geometries were numerically simulated to compare their characteristics and choose the best to measure the water film thickness in the oil–water flow through an impedance-based technique. Finite element method was used for resolving the tridimensional electric field over each sensor. The compared characteristics were the penetration depth, the sensitivity, the minimum spatial resolution (high spatial resolution) and the quasi-linear curve.,The best geometry tested has a spatial resolution of 2 × 2 mm, a penetration depth of 700 µm and a quasi-linear response in the measuring range. This geometry was tested by means of conductance and capacitance static experiments. From these experiments, it could be determined that conductance and the capacitance systems are promising for measuring water film thickness in an oil–water flow.,Several measurement techniques such as micro-PIV, planar laser-induced fluorescence and planar conductive or capacitive sensors that are supposed to be adaptable to the liquid–liquid flow have been proposed recently. Micro-PIV and planar-induced fluorescence need transparent pipes and fluids. On the other hand, conductive or capacitive methods have been only applied to low viscosity fluids. In that context, this paper proposes to study a new technique for non-intrusive measurement of the liquid-liquid flow. The main goal is the validation of the new planar sensor as a reference tool for the development of instrumentation for oilfield application.

PIV measurements of the instantaneous velocities of flow in an annular duct

Particle image Velocimetry (PIV) is a well-established technique in the field of fluid flow measurement and provides instantaneous velocity fields over global domains. It has been applied to external and internal flows, in single and two-phase flows. Regarding internal flow, works about the application of PIV in annular ducts are scanty. An experimental work is presented, where flow of water is studied in an annular duct of inner diameter of 60 mm and outer diameter of 155 mm and 10.5-m length, with the goal of obtaining detailed velocity measurements. Experiments were also conducted in a 21.1-mm inner-diameter horizontal transparent pipe of 3m length for comparison purposes. Depending on the flow rates of water, it can be laminar, transitional or turbulent. In this study, the water flow rate was kept at two different values for the horizontal pipe, for either laminar or turbulent flow, and three different values for the annular duct, allowing the analysis of one laminar and two turbulent flows. Velocity fields and statistic quantities of the turbulent flow were calculated.