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ABSTRACT Gas liquid slug flow can induce vibrations in process piping and large scale slugging can cause some oscillations of subsea flexible pipes. Pipe movements should be avoided, as fatigue can lead to pipe failure. Flow transients can also cause pipe failure, water slugs have lifted geothermal pipelines off support, and runaway hydrate plugs have caused fatalities. The flow – structure interaction is therefore of interest to study and to incorporate in dynamic simulators. Several cases of dynamic slug flow-structure interactions have been studied in small scale laboratory. A two way coupling has been established between a pipe structure model and a slug tracking model. A pigging case of a submerged flexible pipe is presented here. An initially liquid filled hose is hanging freely in a 4m long water tank. A pig is inserted at the inlet, and subject to a backpressure of air which drives the pig and the liquid out of the pipe. The subsequent pipe dynamics is video recorded and compared with the coupled flow-structure simulations. At high flow rates the initially U-shaped pipe rises above the water level and falls back to the surface. The experiments and the coupled models are described as well as key aspects of the numerical solvers.
- Europe (0.68)
- South America > Brazil (0.47)
- Energy > Oil & Gas > Upstream (1.00)
- Materials > Chemicals > Commodity Chemicals > Petrochemicals (0.46)
In this paper, the characteristics of stratified-annular flows such as flow patterns, phase distributions, liquid height, and pressure gradient were studied using a traversing two-energy gamma densitometer, high-speed video recordings and pressure transducers. The experiments were carried out in a 0.069m diameter and 50 m long horizontal pipe. The fluid system consist of high density gas, SF6, at 0.7 MPa and 20 C (46 kg/m) to simulate high pressure conditions of real multiphase transport systems; 0.102 Pa s viscosity oil and water as liquid phases. Two-phase and three-phase flow experiments were conducted at four liquid superficial velocities and different gas velocities for water cut values (The water cut is defined as the ratio between the superficial water velocity to the liquid superficial velocity). The experimental results show that: The liquid fraction profile with a pure gas-oil shows higher values than for the three-phase flow profiles; the oil and water holdup profiles show water accumulation with respect of no-slip conditions due to more oil than water being entrained as droplets into the gas core; the three-phase pressure drop values are in between the gas-oil and gas-water values; when a comparison between the visual liquid heights with holdup measurements is made, there are indications that the shape of the gas-liquid interface may be curved. The application of gamma densitometry for measuring phase fractions in three-phase flows is shown and new data for systems using high viscosity oils for stratified-annular flows in horizontal pipes which is valuable for improving models and closures in multiphase flow simulators.
- Europe (0.46)
- South America > Brazil (0.46)
- North America > United States (0.46)
- Reservoir Description and Dynamics > Reservoir Fluid Dynamics > Multiphase flow (1.00)
- Reservoir Description and Dynamics > Improved and Enhanced Recovery (1.00)
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring > Production logging (1.00)
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring > Downhole and wellsite flow metering (1.00)
Abstract Multiphase flow models require models for each flow regime, and models for the transition between the regimes. Dynamic slug flow models also aim at predicting the slug formation and decay as well as the statistical distributions of lengths, frequencies and velocities. Previous experimental studies have demonstrated the existence of a region in the flow regime map where both stratified and slug flow can be stable flow regimes, typically for low pressure systems. This phenomenon can also lead to large flow transients at the point of stratified-slug transition, with excess liquid transported out of the pipeline in the form of a large liquid slug, with length depending on the pipe geometry and length. This phenomenon is experimentally investigated for 3 degrees downwards air-water flow in a 16 m long pipe of 60 mm internal diameter. An inlet section of 3 m long was configured at 14.6 degree downward and 25 degrees upward, in order to generate either stratified flow or slug flow. The statistical analysis of the slug frequency and length distribution was examined, and the results show a premature stratified-slug transition when slug flow is set as inlet condition. The slug formation and evolution along the pipeline was studied by tracking the slugs at different locations in the downward pipe. Results were compared against flow patterns predicted by a commercial simulator.
- South America > Brazil (0.46)
- Europe (0.28)
- Research Report > New Finding (0.68)
- Research Report > Experimental Study (0.68)
- Reservoir Description and Dynamics (1.00)
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring > Production logging (1.00)
Abstract Some cases of marine operations with pipes conveying multiphase flows can show structural movements depending on the internal flow dynamics. A floating pipe conveying two-phase gas-liquid flow is an example where a two-way coupling between the internal flow and the structural dynamics is needed. The objectives of the paper is to demonstrate a method for dynamic coupling of slug flow and pipe structure simulations by comparing numerical results with small scale experiments on flexible pipes. Two small scale experimental setups for two-phase slug flow in floating and submerged flexible pipes were prepared. The experiments were designed to give unstable flows. The air and water flow rates were measured and the pipe movements were video recorded. A new coupled model was established, in which a structural dynamic model has been implemented into a dynamic slug tracking model. Forces due to the internal flow such as fluid weight, friction and centrifugal force were included in the structural model, as well as external fluid drag and soil contact forces among others. The implemented model can reproduce fairly well the dynamic forces due to the internal flow as well as predict the associated pipe deformations and movements. Slug flow can potentially have an impact on pipe dynamics, in particular for cases where severe slugging can occur.
- South America > Brazil (0.70)
- Europe (0.68)
- North America > United States > California (0.28)
- Reservoir Description and Dynamics (1.00)
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring > Production logging (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers (1.00)
This paper is focused on the modelling of liquid droplet concentration profiles in horizontal stratified-annular flows. Two approaches are studied. First a review of the current state of 1D prediction models for liquid droplet concentration profiles is made. The limitations and assumptions are also discussed. Second, a new methodology is proposed as an alternative for the droplet concentration profiles prediction assuming an exponential droplet distribution in the vertical diameter. The methodology is built by obtaining empirical correlations using genetic algorithms. The algorithm implementation is made by using Binary trees and Prüfer encoding. As a result two empirical correlations are presented for the droplet concentration at the gas-liquid interface and the profiles decay coefficient. The correlations are developed for two-phase gas-liquid flows and are expressed in terms of three non-dimensional parameters including the effects of the physical fluid properties and operational conditions. The obtained two-phase flow correlations are extended to the three-phase oil-water-gas flows. The model and correlations are tested against recent experiments and available data from the literature. Introduction Separated gas-liquid flows are very common in the oil and gas industry. One important mechanism to be considered at high gas velocities is the liquid droplet entrainment. In some cases a large fraction of the liquid transport in the pipe occurs in the droplet field. Predicting the liquid holdup in transport pipes is important so an accurate droplet model should be considered.
- Data Science & Engineering Analytics > Information Management and Systems (1.00)
- Reservoir Description and Dynamics > Reservoir Fluid Dynamics (0.86)
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring > Production logging (0.86)
Abstract An experimental study on air-water surge waves is conducted in the multiphase flow laboratory at NTNU. A special configuration of a 57 meter long test pipeline of 60 mm I.D. was prepared with 3 pipes and two bends. The waves were generated in a dip in the pipe close to the inlet after a variation of the gas flowrate. The wave propagation behavior along the pipeline was recorded with conductance ring proves. The wave characteristics were compared with OLGA simulations with good results. Introduction Surge waves are mainly a transient phenomenon that is initiated by a change from one steady state to another. In gas-condensate pipelines the surge waves can be initiated by a change in the production rate. The oscillations in the liquid flow are caused by liquid mass waves propagating down the pipeline with a velocity close to the liquid transport velocity [1]. Surge waves normally occur during production at low flow rates, typically during production ramp up [2] and sometimes also during ramp down [3]. When the production rate is increased the pipeline will move from a state with a large liquid content to a state with less liquid content. When this excess liquid is expelled out of the pipeline, it is seen as a long surge wave at the outlet [2]. The liquid content (condensed fluids and inhibitors) in the pipelines is normally very low. A surge wave is a modest surface elevation with a very long wavelength, and the waves can potentially flood the receiving facilities. Validation of dynamic flow simulators for the prediction of surge waves occurrence and behaviour is then of high importance. It has been a challenge for commercial transient multiphase flow simulators to predict surge waves in gas-condensate systems satisfactorily [1]. With special tuning of their models, FlowManager could give excellent prediction of surge waves observed in the Ormen Lange field [4]. There are still uncertainties for other fields or systems, in particular regarding three phase flows. The main reasons are weak understandings of the basic fluid mechanics in the initiation of surge waves, and the dynamics of the wave propagation. In the current work, an experimental study is conducted to investigate the possibility of reproducing surge waves in a small scale laboratory with air and water at atmospheric pressure. The experimental data can then be used for comparisons with dynamic flow simulators.
- Europe > Norway > Norwegian Sea (0.34)
- Asia > Middle East > Israel > Mediterranean Sea (0.24)
- Research Report > New Finding (0.69)
- Research Report > Experimental Study (0.69)
- Europe > Norway > Norwegian Sea > Møre Basin > PL 442 > Block 6305/8 > Ormen Lange Field > Springar Formation (0.99)
- Europe > Norway > Norwegian Sea > Møre Basin > PL 442 > Block 6305/8 > Ormen Lange Field > Egga Formation (0.99)
- Europe > Norway > Norwegian Sea > Møre Basin > PL 442 > Block 6305/6 > Ormen Lange Field > Springar Formation (0.99)
- (21 more...)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers (1.00)
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring > Production logging (0.96)
- Reservoir Description and Dynamics > Reservoir Fluid Dynamics > Multiphase flow (0.75)
- Reservoir Description and Dynamics > Unconventional and Complex Reservoirs > Gas-condensate reservoirs (0.69)
Inclination Effect on Stratified Oil-Water Pipe Flow
Khatibi, M. (University of Stavanger) | Schumann, H. (Norwegian University of Science and Technology) | Nydal, O. J. (Norwegian University of Science and Technology) | Yang, Z. (Norwegian University of Science and Technology and Statoil ASA) | Time, R. W. (University of Stavanger)
Abstract Oil-water pipe flow experiments in a horizontal and slightly inclined test section are presented. The experimental work was performed in a 16 m acrylic test section with ID of 60 mm, using tap water and a medium viscosity oil (61 cP) as test fluids. The pipe inclination was gradually changed from −5° to +5°. In-put water cuts from 0 % to 100 % were covered. The mixing velocity was varied from 0.1 m/s to 1.0 m/s. Flow pattern maps, local phase fraction, and pressure gradient measurements are shown. Significant influence of the pipe inclination was found. This effect became more crucial as the mixing velocity was reduced. The experimental results are compared with low viscosity data from Kumara el al. (2) and the commercial flow simulator OLGA. Introduction Pipelines in hilly terrain are a common scenario for offshore as well as onshore production systems. The inclination of a pipeline is a crucial factor considerably influencing the oil-water flow. Small deviations from horizontal alignment can cause large changes of the local phase fractions and consequently the pressure gradient. Available data is, however, often limited to low viscosity oils and small inclination angles. Furthermore, the tested flow velocities are a restriction in the available data. Common flow simulators are mainly developed based on low viscosity data. Predicting flow with high viscosity oil these simulators often do not give satisfying results. Further research on high viscosity fluids is needed. Abduvayt et al. (1) found that slight changes in the angle of pipe inclination can cause significant changes in the local water fraction. The higher the upward inclinations, the larger the water fraction compared to horizontal alignment. An opposite effect was observed for the downward inclined pipe. A similar behavior was found by Kumara et al. (2); who performed similar experiments as presented in this study, while using a low viscosity oil (1.6 cP). Also Lum et al. (4, 5) studied oil-water flows with a low viscosity oil (5.5 cP) in a smaller pipe diameter (ID = 38 mm) and reported higher local water fraction in upward inclined pipes than horizontal pipe.
- Production and Well Operations > Well & Reservoir Surveillance and Monitoring > Production logging (1.00)
- Reservoir Description and Dynamics > Improved and Enhanced Recovery (0.94)
- Reservoir Description and Dynamics > Fluid Characterization (0.70)