Content of PetroWiki is intended for personal use only and to supplement, not replace, engineering judgment. SPE disclaims any and all liability for your use of such content. More information
Gas-Liquid Two-Phase Flow in Pipes
Gas-liquid two-phase flow is encountered in many industrial processes and is a critical aspect of enormous applications. Examples are oil and gas production, chemical processing, nuclear power plants, aerospace technologies, and renewable energy applications. In the petroleum industry, two-phase flow is a common occurrence in wellbores and pipelines. These pipelines might extend for thousands of miles and through different environments where both flow pressure and temperature change considerably, especially for offshore pipelines. The pipes and wellbores are of varying inclination angles and diameters and they divert liquid and gas through many piping components. As means of connection between the petroleum formation and the processing facilities or export terminals, gas-liquid two-phase flow occurs along these pipes. Design methods are needed to determine the pressure drop, liquid holdup, slug characteristics, and other two-phase flow characteristics that are crucial for designing pipes, pipe components, production equipment, separators, slug catcher, and other processing facilities components for both steady-state and transient operations. Moreover, overcoming flow assurance challenges involves the proper prediction of gas-liquid two-phase flow behavior.
Brill and Arirachakaran (1992) summarized two-phase flow modeling history into three distinct eras. The first era represents the starting of wide dependency on two-phase flow modeling in the oil and gas industry. The third era, which extends to this day, involves many advancements that were not foreseen by Brill and Arirachakaran (1992) and it shapes the future of two-phase flow applications in the petroleum industry. The history of multiphase flow models is summarized as follows,
1. The Empirical Period (1950 - 1975)
During this period, most models relied directly on the experimental behavior of the flow and were based on data collected in the field or laboratory flow loops using conventional instrumentation that are of relatively low accuracy. Many models treated gas and liquid as homogeneous mixtures. However, slippage caused by liquid and gas was captured with these models and the liquid holdup is represented with empirical expressions. At that period of time, the instruments used to capture liquid holdup experimentally in fluid flow loops contributed directly to the accuracy of the developed models. Some of the simplest pressure gradient models that are widely used in the oil and gas industry today were developed in this era, for example, Duns and Ros (1963) and Hagedorn and Brown (1965) for vertical flows and Beggs and Brill (1973) for horizontal and near-horizontal flows. A revolution in modeling efforts was sparked in this era with the Drift Flux Model of Zuber and Findlay (1965) which continued to evolve and improve through the rest of the 20th century and until today. In addition to its importance for the petroleum industry, the contribution of Zuber and Findlay (1965) represented a foundation for the accelerated development of many nuclear planet safety flow codes. This period also witnessed extensive classification and observation for flow patterns, namely, the topological distribution of gas and liquid in pipes. This classification resulted in many versions of flow pattern maps such as Baker (1954), Ros (1961), and Beggs and Brill (1973) which were often based on dimensionless numbers.
2. The Awakening Years (1970 - 1985)
During these years, research focused on addressing the lack of physics in the empirical models. It was quickly realized that the available flow pattern maps are inadequate. Similarly, The empirical relationships of liquid holdups resulted in significant prediction errors. Therefore, the 1970s showed a rising adoption of the physical mechanisms of two-phase flow already in use in other industries, e.g. nuclear industries. The classic works of Dukler and Hubbard (1975) and Taitel and Dukler (1976) introduced mechanistic models that consider more of the governing physics for slug flow and flow pattern. The available pressure gradient correlations coupled with the introduction of the personal computer (PC) in the early 1980s made several practical tools available for petroleum engineers to simulate the flow behavior. Simulating the entire production system and integrating the reservoir performance became possible through simple performance relationships. The true concept of NODALTM analyses was born (Brown 1980).
3. The Modeling Era (1980 - Present)
During this era, extensive advancements in instrumentation and data acquisition systems coupled with high-speed PCs allowed high-quality data which enabled testing and improving two-phase flow theory. Steady-state flow models have seen significant improvements with the flow pattern transition criteria introduced by Taitel et al. (1980), Barnea et al. (1982a, 1982b, 1985), and Barnea (1986, 1987). This resulted in the development of mechanistic models that conserve the physics of each flow pattern individually and ensure seamless flow of the calculations at different flow conditions and inclination angles, namely, the "comprehensive" models such as Ozon et al. (1987), Hasan and Kabir (1988), Xiao et al. (1990), Ansari et al. (1994), and Chokshi (1994). These efforts also led to the steady-state "unified" model of Zhang et al. (2003), which eliminates discontinuities of flow patterns at different conditions. Meanwhile, the two-phase models pioneered in the nuclear industry for transient flow application were expanded and integrated into the petroleum industry problems through efforts such as Taitel et al. (1980), Black et al. (1990), and Pauchon et al. (1993). The 1980s witnessed the release of the extensive and well-financed experimental efforts that led to the development of transient flow codes (Bendiksen, 1991). These transient flow models focus on the simultaneous solution of mass and momentum conservation equation for several control volumes changes with flow patterns. These efforts revolutionized offshore petroleum production and led to safe and maintained production and processing through reliable prediction of pipeline pigging, startup/shutdown operation, slugging, and other transient production and flow assurance phenomena. Within the last few years, Artificial Intelligence and Machine Learning applications are being imported and incorporated to improve the empirical parameters within the existing steady-state and transient models. These efforts are accompanied by the advancement of measurement techniques that improved the quality of two-phase flow field data. The utilization of cloud computing is assisting in pushing these techniques forward into the future.
Alsafran, M. and Brill J. 2017. Applied Multiphase Flow in Pipes and Flow Assurance. Society of Petroleum Engineers.
Ansari, A. M., Sylvester, N. D., Sarica, C. et al. 1994. A Comprehensive Mechanistic Model for Upward Two-Phase Flow in Wellbores. SPE Prod Eng 9 (2): 143-152. SPE-20630-PA. https://doi.org/10.2118/20630-PA.
Baker, O. 1954. Simultaneous Flow of Oil and Gas. Oil & Gas J 53: 185-195.
Barnea, D. 1986. Transition From Annular Flow and From Dispersed Bubble Flow: Unified Models for the Whole Range of Pipe Inclinations. Intl J Multiphase Flow 12 (5): 733-744. https://doi.org/10.1016/0301-9322(86)90048-0.
Barnea, D. 1987. A Unified Model for Predicting Flow-Pattern Transitions for the Whole Range of Pipe Inclinations. Intl J Multiphase Flow 13 (1): 1-12. https://doi.org/10.1016/0301-9322(87)90002-4.
Barnea, D., Shoham, O., and Taitel, Y. 1982a. Flow-Pattern Transition for Downward Inclined Two-Phase Flow: Horizontal to Vertical. Chem Eng Sci 37 (5): 735-740. https://doi.org/10.1016/0009-2509(82)85033-1.
Barnea, D., Shoham, O., and Taitel, Y. 1982b. Flow Pattern Transition for Vertical Downward Two-Phase Flow. Chem Eng Sci 37 (5): 741-744. https://doi.org/10.1016/0009-2509(82)85034-3.
Barnea, D., Shoham, O., Taitel, Y. et al. 1985. Gas-Liquid Flow in Inclined Tubes: Flow Pattern Transition for Upward Flow. Chem Eng Sci 40 (1): 131-136. https://doi.org/10.1016/0009-2509(85)85053-3.
Beggs, H.D., and Brill, J.P. 1973. A Study of Two-Phase Flow in Inclined Pipes," JPT 607; Trans., AIME, 255.
Bendiksen, K. H., Malnes, D., Moe, R. et al. 1991. The Dynamic Two-Fluid Model OLGA: Theory and Applications. SPE Prod Eng 6 (2): 171-180. SPE-19451-PA. https://doi.org/10.2118/19451-PA.
Black, P. S. Daniels, L. C., Hoyle, N. C. et al. 1990. Studying Transient Multi-Phase Flow Using the Pipeline Analysis Code (PLAC). ASME J Energ Resour Tech 112 (1): 25-29. http;//dx.doi.org/10.1115/1.2905708.
Brill, J. P. and Arirachakaran, S. 1992. State of the Art in Multiphase Flow. J Pet Technol 44 (5): 538-541. SPE-23835-PA. https://doi.org/10.2118/23835-PA.
Brown, K. E. 1980. The Technology of Artificial Lift Methods, Vols. 2a, 3a, 3b, 4. Tulsa: Petroleum Publishing.
Chokshi, R. N. 1994. Prediction of Pressure Drop and Liquid Holdup in Vertical Two-Phase Flow Through Large Diameter Tubing. PhD dissertation, University of Tulsa, Tulsa.
Dukler, A. E. and Hubbard, M. G. 1975. A Model for Gas-Liquid Slug Flow in Horizontal and Near Horizontal Tubes. Ind Eng Chem Fund 14 (4): 337-347. https://doi.org/10.1021/i160056a011.
Duns, H. Jr., and Ros, N.C.J. 1963. Vertical Flow of Gas and Liquid Mixtures in Wells," Proc., Sixth World Pet. Cong., Tokyo 451.
Hagedorn, A.R. and Brown, K.E. 1965. Experimental Study of Pressure Gradients Occurring During Continuous Two-Phase Flow in Small-Diameter Vertical Conduits. JPT 475; Trans., AIME, 234.
Hasan, A. R. and Kabir, C. S. 1988. A Study of Multiphase Flow Behavior in Vertical Wells. SPE Prod Eng 3 (2): 263-272. SPE-15138-PA. https://doi.org/10.2118/15138-PA.
Ozon, P. M., Ferschneider, G., and Chwetzoff, A. 1987. A New Multiphase Flow Model Predicts Pressure and Temperature Profiles in Wells. Paper presented at the SPE Offshore Europe Conference, Aberdeen, 8-11 September. SPE-16535-MS. https://doi.org/10.2118/16535-MS.
Pauchon, C., Dhulesia, H., Lopez, D. et al. 1993. TACITE: A Comprehensive Mechanistic Model for Two-Phase Flow. Paper presented at the BHR Group 6th International Conference on Multiphase Production Technology, Cannes, France, 16-18 June.
Ros, N. C. J. 1961. Simultaneous Flow of Gas and Liquid as Encountered in Well Tubing. J Pet Technol 13 (10): 1037-1049. SPE-18-PA. https://doi.org/10.2118/18-PA.
Taitel, Y. and Dukler, A. E. 1976. A Model for Predicting Flow Regime Transitions in Horizontal and Near Horizontal Gas-Liquid Flow. AIChE J 22 (1): 47-55. https://doi.org/10.1002/aic.690220105.
Taitel, Y., Barnea, D., and Dukler, A. E. 1980. Modeling Flow Pattern Transition for Steady Upward Gas-Liquid Flow in Vertical Tubes. AIChE J 26 (3): 345-354.
Xiao, J. J., Shoham, O., and Brill, J. P. 1990. A Comprehensive Mechanistic Model for Two-Phase Flow in Pipelines. Paper presented at the SPE Annual Technical Conference and Exhibition, New Orleans, 23-26 September. SPE-20631-MS. https://doi.org/10.2118/20631-MS.
Zhang, H. -Q., Wang, Q., Sarica, C. et al. 2003. Unified Model for Gas-Liquid Pipe Flow via Slug Dynamics—Part 1: Model Development. ASME J Energ Resour Tech 125 (4): 266-273. https://doi.org/10.1115/E1615246.
Zuber, N. and Findlay, J. A. 1965. Average Volumetric Concentration in Two-Phase Flow Systems. J. Heat Transfer 87, 453-468.