Browsing by Author "Baba, Yahaya D."
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Item Open Access Comparative analysis of riser base and flowline gas injection on vertical gas-liquid two-phase flow(MDPI, 2022-10-10) Brini Ahmed, Salem K.; Aliyu, Aliyu M.; Baba, Yahaya D.; Abdulkadir, Mukhtar; Abdulhadi, Rahil Omar; Lao, Liyun; Yeung, HoiGas injection is a frequently used method for artificial lift and flow regime rectification in offshore production and transportation flowlines. The flow behaviour in such flowlines is complex and a better understanding of flow characteristics, such as flow patterns, void fraction/hold up distributions and pressure gradient is always required for efficient and optimal design of downstream handling facilities. Injection method and location have been shown to strongly affect downstream fluid behaviour that can have important implications for pumping and downstream facility design, especially if the development length between pipeline and downstream facility is less than L/D = 50 as reported by many investigators. In this article, we provide the results of an experimental investigation into the effects of the gas injection position on the characteristics of the downstream upwards vertical gas flow using a vertical riser with an internal diameter of 52 mm and a length of 10.5 m. A horizontal 40-m-long section connected at the bottom provides options for riser base or horizontal flow line injection of gas. The flowline gas injection is performed 40 m upstream of the riser base. A 16 by 16 capacitance wire mesh sensor and a gamma densitometer were used to measure the gas-liquid phase cross-sectional distribution at the riser top. A detailed analysis of the flow characteristics is carried out based on the measurements. These include flow regimes, cross-sectional liquid holdup distributions and peaking patterns as well as analysis of the time series data. Our findings show that flow behaviours differences due to different gas injection locations were persisting after a development length of 180D in the riser. More specifically, core-peaking liquid holdup occurred at the lower gas injection rates through the flowline, while wall-peaking holdup profiles were established at the same flow conditions for riser base injection. Wall peaking was associated with dispersed bubbly flows and hence non-pulsating as against core-peaking was associated with Taylor bubbles and slug flows. Furthermore, it was found that the riser base injection generally produced lower holdups. It was noted that the circumferential injector used at the riser base promoted high void fraction and hence low liquid holdups. Due to the bubbly flow structure, the slip velocity is smaller than for larger cap bubbles and hence the void fraction is higher. The measurements and observations presented in the paper provides valuable knowledge on riser base/flowline gas introduction that can directly feed into the design of downstream facilities such as storage tanks, slug catchers and separators.Item Open Access Estimating slug liquid holdup in high viscosity oil-gas two-phase flow(Elsevier, 2018-10-29) Archibong-Eso, Archibong; Okeke, Nonso Evaristus; Baba, Yahaya D.; Aliyu, Abdulkabir; Lao, Liyun; Yeung, H.Slug flow is one of the most critical and often encountered flow patterns in the oil and gas industry. It is characterised by intermittency which results in large fluctuations in liquid holdup and pressure gradient. A proper understanding of its parameters (such as slug holdup) is essential in the design of transport facilities (e.g. pipelines) and process equipment (slug catchers, separators etc.). In this paper, experimental investigation of slug liquid holdup (defined as the liquid volume fraction in the slug body of a slug unit) is performed. Mineral oil with viscosity, μ=−0.0043T3+0.0389T2−1.4174T+18.141 and air were used as test fluids. A 0.0254 m and 0.0762 m pipe internal diameters facilities with pipe lengths of 5.5 and 17 m respectively were used in the study. Electrical Capacitance Tomography was used for slug holdup measurements. Results obtained in the study shows that slug liquid holdup varied directly as the viscosity and inversely as the gas input fraction. Existing slug holdup correlations and models in literature did not sufficiently predict present experimental results. A new empirical predictive correlation for estimating slug liquid holdup was derived from present experimental databank and from data obtained in literature. The databank's liquid viscosity ranges from 0.189 – 8.0 Pa.s. Statistical analysis of the new correlation vis-à-vis existing ones showed that the present correlation gave the best performance with an average percent error, E1; absolute average percent error, E2 and standard deviation, E3 of 0.001, 0.05 and 0.07 respectively, when tested on the high viscosity liquid–gas databank.Item Open Access Experimental investigation of high viscous multiphase flow in horizontal pipelines(2016) Baba, Yahaya D.; Yeung, HoiDiminishing reserves of “conventional” light crude oil, increased production costs amidst increased world energy demand over the last decade has spurred industrial interest in the production of the significantly and more abundant “unconventional” heavy crude oil. Recent findings have shown that unconventional oil being a veritable energy source accounts for over two-thirds of the world total oil reserve. The exploration of this vast resource for easy production and transportation requires a good understanding of multiphase system for which the knowledge of the effect of fluid viscosity is of great importance. Heavy oils are known for their high liquid viscosities which make them even more difficult and expensive to produce and transport in pipelines at ambient temperatures. In the light of this, it has become imperative to investigate the rheology of high viscosity oils and ways of enhancing its production and transportation since a critical understanding of multiphase flow characteristics are vital to aid engineering design. It is clear from experimental investigation reported so far in literatures and in Cranfield University that the behaviour of high viscosity oil-gas flows differs significantly from that of low viscosity oils. This means that most of the existing prediction models in the literature which were developed from observations of low viscosity liquid-gas flow will not perform accurately when compared to oil-gas flow data for high viscosity oil. Therefore, this research work seek to extend databank and provide a clearer understanding of the physics of high viscous multiphase flows. Experimental investigation have been conducted using 3-inch and 1-inch ID horizontal test facilities for oil-gas and oil-water respectively using different oil viscosities. The effects of liquid viscosities on oil-gas two phase flow parameters (i.e. pressure gradient, mean liquid holdup, slug frequency, slug translational velocity and slug body length) have been discussed. Assessment of existing prediction models and correlations in the literature are also carried out and their performance highlighted. New/improved prediction correlations for high viscosity oil-gas flow slug frequency, slug translational velocity and slug body have been proposed with their performance evaluated against the results obtained for this study and in literature. As for high viscosity oil-water flows, a new flow pattern maps have been established for high viscous oil-water two-phase flow in horizontal pipe with ID = 0.0254 m for which four flow patterns were observed namely; rivulet, core annular, plug and dispersed flows were observed. Generally, it was observed that increase in oil viscosity favoured the Core Annular Flow pattern, similar behaviour was also observed for increased oil holdup. Comparatively analysis of results obtained here with low viscous kerosene and water flow study obtained under similar flow geometry and conditions shows significant difference in flow patterns under similar flow conditions.Item Open Access Interfacial friction in upward annular gas–liquid two-phase flow in pipes(Elsevier, 2017-02-17) Aliyu, A. M.; Baba, Yahaya D.; Lao, Liyun; Yeung, H.; Kim, K. C.Accurate prediction of interfacial friction between the gas and liquid in annular two-phase flow in pipes is essential for the proper modelling of pressure drop and heat transfer coefficient in pipeline systems. Many empirical relationships have been obtained over the last half century. However, they are restricted to limited superficial liquid and gas velocity ranges, essentially apply to atmospheric pressures, and the relationships are only relevant for pipes with inner diameters between 10 and 50 mm. In this study, we carried out experiments in a large diameter flow loop of 101.6 mm internal diameter with the superficial gas and liquid ranges of 11–29 m/s and 0.1–1.0 m/s respectively. An examination of published interfacial friction factor correlations was carried out using a diverse database which was collected from the open literature for vertical annular flow. The database includes measurements in pipes of 16–127 mm inner diameter for the liquid film thickness, interfacial shear stress, and pressure gradient for air-water, air-water/glycerol, and argon-water flows. Eleven studies are represented with experimental pressures of up to 6 bar. Significant discrepancies were found between many of the published correlations and the large pipe data, primarily in the thick film region at low interfacial shear stress. A correlation for the interfacial friction factor was hence derived using the extensive database. The correlation includes dimensionless numbers for the effect of the diameter across pipe scales to be better represented and better fit the wide range of experimental conditions, fluid properties, and operating pressures.Item Open Access Prediction of entrained droplet fraction in co-current annular gas–liquid flow in vertical pipes(Elsevier, 2017-03-07) Aliyu, A. M.; Almabrok, Almabrok Abushanaf; Baba, Yahaya D.; Archibong-Eso, Archibong; Lao, Liyun; Yeung, Hoi; Kim, K. C.The entrained droplet fraction is an important parameter in annular two-phase flow, as its correlations are key inputs in flow simulation codes for the prediction of pressure drop and critical heat flux or dryout. Investigators have stressed the importance of extending the validity range of current correlations so that more conditions are covered. This could be achieved for example by including fluids with higher viscosities, a wider range of operating pressures, and increase in the size of pipes used for experiments (most of the data in the literature are from pipes of 50 mm diameter and below). In attempt to improve the latter, experiments were conducted in a 101.6 mm gas–liquid flow loop at Cranfield University’s Oil and Gas Engineering Laboratory and data on the fraction of droplets were collected in the annular flow regime by measuring the film velocity, from which the droplet fraction was calculated. Comparison of the film velocity by this method and by a mass balance showed close agreement. A capacitance Wire Mesh Sensor was used for flow visualisation in order to distinguish between annular and churn flow. In order to arrive at an improved correlation, over 1300 data points were gathered from other published works. These include air–water studies where large pipes of up to 127 mm in diameter were used. The others were from small-diameter pipes and for refrigerant, steam–water, air–water, and air–glycerine flows. Since in the annular regime, the gas flow entrains liquid droplets into the core, their presence alters the properties of the gas core. Therefore, accurate predictions are pivotal for the energy efficient design and operation of facilities in the petroleum and nuclear power industry. The correlation obtained here showed good agreement with the collected databank.Item Open Access Sand minimum transport conditions in gas–solid–liquid three-phase stratified flow in a horizontal pipe at low particle concentrations(Elsevier, 2019-01-15) Fajemidupe, Olawale T.; Aliyu, Aliyu M.; Baba, Yahaya D.; Archibong-Eso, Archibong; Yeung, HoiSand production in the life of oil and gas reservoirs is inevitable, as it is co-produced from reservoirs. Its deposition in petroleum pipelines poses considerable risk to production and can lead to pipe corrosion and flow assurance challenges. Therefore, it is important that pipe flow conditions are maintained to ensure sand particles are not deposited but in continuous motion with the flow. The combination of minimum gas and liquid velocities that ensure continuous sand motion is known as the minimum transport condition (MTC). This study investigates the effect both of sand particle diameter and concentration on MTC in gas/liquid stratified flow in a horizontal pipeline. We used non-intrusive conductivity sensors for sand detection. These sensors, used for film thickness measurement in gas/liquid flows, were used for the first time here for sand detection. We found that MTC increases with increase in particle diameter for the same concentration and also increases as the concentration increases for the same particle diameter. A correlation is proposed for the prediction of sand transport at MTC in air–water flows in horizontal pipes, by including the effect of sand concentration in Thomas’s lower model. The correlation accounts for low sand concentrations and gave excellent predictions when compared with the experimental results at MTC.Item Open Access Slug length for high viscosity oil-gas flow in horizontal pipes: experiments and prediction(Elsevier, 2018-02-08) Baba, Yahaya D.; Aliyu, Aliyu M.; Archibong-Eso, Archibong; Abdulkadir, Mukhtar; Lao, Liyun; Yeung, HoiAn experimental investigation was carried out on the effects of high liquid viscosities on slug length in a 0.0762-m ID horizontal pipe using air-water and air-oil systems with nominal viscosities ranging from 1.0 to 5.5 Pa s. The measurements of slug length were carried out using two fast sampling gamma densitometers with a sampling frequency of 250 Hz. The results obtained show that liquid viscosity has a significant effect on slug length. An assessment of existing prediction models and correlations in the literature was carried out and statistical analysis against the present data revealed some discrepancies, which can be attributed to fluid properties in particular, low viscous oil data used in their derivation Hence, a new high viscous oil data presented here from which we derive a new slug length correlation was derived using dimensional analysis. The proposed correlation will improve prediction of slug length as well as provide a closure relationship for use in flow simulations involving heavy oil. This is important since most current fields produce highly viscous oil with some reaching 10 Pa s.Item Open Access Slug translational velocity for highly viscous oil and gas flows in horizontal pipes(MDPI, 2019-09-12) Baba, Yahaya D.; Archibong-Eso, Archibong; Aliyu, Aliyu M.; Fajemidupe, Olawale T.; Ribeiro, Joseph X. F.; Lao, Liyun; Yeung, HoiSlug translational velocity, described as the velocity of slug units, is the summation of the maximum mixture velocity in the slug body and the drift velocity. Existing prediction models in literature were developed based on observation from low viscosity liquids, neglecting the effects of fluid properties (i.e., viscosity). However, slug translational velocity is expected to be affected by the fluid viscosity. Here, we investigate the influence of high liquid viscosity on slug translational velocity in a horizontal pipeline of 76.2-mm internal diameter. Air and mineral oil with viscosities within the range of 1.0–5.5 Pa·s were used in this investigation. Measurement was by means of a pair of gamma densitometer with fast sampling frequencies (up to 250 Hz). The results obtained show that slug translational velocity increases with increase in liquid viscosity. Existing slug translational velocity prediction models in literature were assessed based on the present high viscosity data for which statistical analysis revealed discrepancies. In view of this, a new empirical correlation for the calculation of slug translational velocity in highly viscous two-phase flow is proposed. A comparison study and validation of the new correlation showed an improved prediction performance.Item Open Access Upward gas–liquid two-phase flow after a U-bend in a large-diameter serpentine pipe(Elsevier, 2017-01-02) Aliyu, A. M.; Almabrok, Almabrok Abushanaf; Baba, Yahaya D.; Lao, Liyun; Yeung, Hoi; Kim, Kyung ChunWe present an experimental study on the flow behaviour of gas and liquid in the upward section of a vertical pipe system with an internal diameter of 101.6 mm and a serpentine geometry. The experimental matrix consists of superficial gas and liquid velocities in ranges of 0.15–30 m/s and from 0.07 to 1.5 m/s, respectively, which cover bubbly to annular flow. The effects on the flow behaviours downstream of the 180° return bend are significantly reduced when the flow reaches an axial distance of 47 pipe diameters from the U-bend. Therefore, reasonably developed flow is attained at this development length downstream of the bend. Other published measurements for large-diameter film thickness show similar trends with respect to the superficial gas velocity. However, the trends differ from those of small-diameter pipes, with which the film thickness decreases much faster with increasing gas flow. As a result, only a few of the published correlations for small pipe data agreed with the experimental data for large pipe film thickness. We therefore modified one of the best-performing correlations, which produced a better fit. Qualitative and statistical analyses show that the new correlation provides improved predictions for two-phase flow film thickness in large-diameter pipes.Item Open Access Void fraction development in gas-liquid flow after a U-bend in a vertically upwards serpentine-configuration large-diameter pipe(Springer, 2017-08-01) Almabrok, Almabrok Abushanaf; Aliyu, Aliyu M.; Baba, Yahaya D.; Lao, Liyun; Yeung, HoiWe investigate the effect of a return U-bend on flow behaviour in the vertical upward section of a large-diameter pipe. A wire mesh sensor was employed to study the void fraction distributions at axial distances of 5, 28 and 47 pipe diameters after the upstream bottom bend. The study found that, the bottom bend has considerable impacts on up-flow behaviour. In all conditions, centrifugal action causes appreciable misdistribution in the adjacent straight section. Plots from WMS measurements show that flow asymmetry significantly reduces along the axis at L/D = 47. Regime maps generated from three axial locations showed that, in addition to bubbly, intermittent and annular flows, oscillatory flow occurred particularly when gas and liquid flow rates were relatively low. At this position, mean void fractions were in agreement with those from other large-pipe studies, and comparisons were made with existing void fraction correlations. Among the correlations surveyed, drift flux-type correlations were found to give the best predictive results.