At first glance, the Joe C. Richardson building at Texas A&M University blends in with the campus skyline—tall, dignified, and seemingly ordinary. But step inside, and you’ll uncover one of the department’s best-kept secrets: a vertical lab that stretches beyond the roof visible from the street. Hidden within its walls is the 142-ft Multiphase Flow Loop Tower (TowerLAB), a 10-story engineering marvel pushing the boundaries of petroleum research in production operations, flow assurance, and safe offshore drilling.
Some of the research areas the lab has been used for include
- Liquid loading in gas wells.
- Axial development of vertical two-phase flow regimes.
- Liquid transport during gas-flow transients.
- Riser gas expansion and unloading.
- Upward gas-liquid flow.
- Gas kick migration (especially CO2 kicks).
This article highlights the lab's unique capabilities and the Texas A&M petroleum engineering department's contributions to advancing petroleum engineering research.
Introduction to Multiphase Flow
The concept of multiphase flow is one we encounter in our day-to-day activities, from the rise of gas bubbles when opening a bottle of soda, to the splattering of hot cooking oil, and the condensation of exhaled air during winter.
This type of flow is defined as the simultaneous movement of more than one phase, typically of different compositions, through a system or stream.
In the oil and gas industry, multiphase flow is typically encountered in wellbores and flowlines and risers that transport fluids. The phases present in a multiphase flow can be solid, liquid, or gas.
As described by Bello et al. (2007), multiphase flow can involve either two phases or three phases.
Flow Regimes
Flow regime describes the geometrical distribution of multiphase fluids. For instance, in vertical upward gas-liquid flow, four flow regimes based on visual observation of experiments are identified: bubble, slug, churn, and annular flow.
Fig. 1 shows a typical flow pattern in a wellbore.
However, predicting the behavior of multiphase flow (mixtures of gas and liquid or multiple liquids) in petroleum engineering is difficult due to complex interactions, changing conditions, and varied flow patterns. In two-phase systems, relative phase speeds, interfacial tension, and pipe inclination significantly affect flow regimes. Three-phase flows are even more challenging due to extra interfaces that complicate visualization and classification, especially in large-scale operations. Liquid-liquid interactions are particularly difficult to observe and model because of mixed phase distributions and dynamic shifts between different flow types.
To tackle these issues, the industry increasingly uses controlled experiments and advanced simulations. Recognizing that no single lab can mimic all field conditions, Texas A&M University created the TowerLAB. This specialized vertical facility with specific instrumentation is designed to study and validate key aspects of two-phase flow, especially in riser drilling and production, providing critical data for modeling and operational decisions.
The Tower Lab
The length of the tubing as per the depth of the wellbore plays a crucial role, particularly in the formation and evolution of flow regimes along the pipe. In shorter tubes (with length-to-hydraulic diameter (L/D) ratios less than 300), it is typically challenging to achieve fully developed flow. This makes it even more difficult to accurately measure how two-phase flows behave along the axial direction.
Globally, there are only a few research facilities equipped with long vertical tubes (L/D ratios greater than 500), which limits the availability of experimental data on axial two-phase flow behavior. To address this gap, TowerLAB was specifically designed.
The high-pressure research multiphase flow loop was originally designed in 2008 to experimentally investigate liquid loading in vertical gas wells (Fernandez 2010).
TowerLAB is one of the tallest multiphase flow loops designed for experimenting with fluid and gas dynamics in the world (Fig. 2) (Fernandez et al., 2010).
The lab is assembled with 5.5-in.-inner-diameter clear PVC pipe sections for visual observation of in-situ flow regimes, steel pipe sections, a tank and separator, a 200 gal/min multiphase flow pump for fluid circulation, and a compressor for gas injection. Annular flow experiments can be conducted in a 2.625-in. hydraulic diameter while pipe flow experiments can be conducted in a 2.375-in. pipe.
The loop comprises three major parts (Fig. 3):
- Boosting system: Located in the basement and comprises two air compressors and a centrifugal pump which regulate the pressure and flow rates of the working fluids.
- Test section: The vertical transparent/steel tube combination that runs through the entire height of the tower, with a total vertical length of 142 ft. It is equipped with instruments for characterization of flow regimes and measurement of pressure, temperature, and liquid holdup. Video cameras are positioned at three locations along the test section to visualize the two-phase flow.
- Separator: Located on the 10th floor, at the top of the flow loop, with a capacity of 0.57 m3. It separates air from water, vents the air to the atmosphere, and returns the water to the storage tank in the basement.
This arrangement simulates the operational conditions of actual oil wells, facilitating the investigation of gas-liquid two-phase annular flow dynamics under controlled laboratory conditions. The data acquisition from sensors, timed gas injection, and water circulation is operated with the LabVIEW system.
Challenges and Innovations
The fluid-flow experiments in the TowerLab are limited to a vertical fluid-flow scenario. The hydraulic diameter is suitable to establish a fully developed two-phase multiphase flow ranging from bubbly flow to churn flow as the gas void fraction increases. Annular flow can sometimes be established for short periods at high gas-flow rates and reduced liquid levels. For safety considerations, the experiments are limited to less than 100 psi operating pressure.
Although the TowerLab is a relatively large multiphase flow loop compared to other experimental setups, it is still significantly small to actual field well depths. Therefore, a coupled approach with computational fluid dynamics of the experiments is adopted to scale experimental results to field applications.
The TowerLab is currently fitted with thermocouples for insights into the thermal effects of these fluid-flow problems. However, future experiments can also benefit from advanced data acquisition tools such as fiber optics, if installed. Coupling the experimental setup with distributed temperature sensing data, pressure, and visual observation data can significantly advance research on multiphase flow-related problems. This is applicable to industries such as oil and gas, geothermal, nuclear, and complex fluid flow in channel scenarios.
Conclusion
Since its inception in 2008, TowerLAB has been a cornerstone of research and innovation in complex fluid flow. Through its unique vertical design and experimental capabilities, it has enabled impactful research in fluid dynamics, machine vision, and computational modeling. It has supported the training of students at all academic levels and fostered collaborations between renowned faculty and industry partners on projects aimed at enhancing offshore drilling safety and advancing automation.
TowerLab remains essential to preparing the next generation of engineers and addressing the technical challenges of a more data-driven and sustainable energy future.
For Further Reading
Vertical Two-Phase Flow Regimes in an Annulus Image Dataset—Texas A&M University by K. Manikonda, C. Obi, A. Brahmane, et. al., Texas A&M University.
Onset and Subsequent Transient Phenomena of Liquid Loading in Gas Wells: Experimental Investigation Using a Large-Scale Flow Loop by P. Waltrich, Texas A&M University.
Experimental Validation of Multiphase Flow Models and Testing of Multiphase Flow Meters: A Critical Review of Flow Loops Worldwide by O.O. Bello, Clausthal University of Technology; G. Falcone and C. Teodoriu, Texas A&M University.
Fluid Flow and Heat Transfers in Wellbores by R. Hasan and S. Kabir, OnePetro.
Design of a High-Pressure Research Flow Loop for the Experimental Investigation of Liquid Loading in Gas Wells by J. Fernandez, SPE, G. Falcone, SPE, and C. Teodoriu Texas A&M University.
Axial Development of Annular, Churn and Slug Flows in a Long Vertical Tube by P. Waltrich, Louisiana State University; G. Falcone, Clausthal University of Technology; and J. Barbosa, Federal University of Santa Catarina.
Liquid Transport During Gas Flow Transients Applied to Liquid Loading in Long Vertical Pipes by P. Waltrich, Louisiana State University; G. Falcone, Clausthal University of Technology; and J. Barbosa, Federal University of Santa Catarina.
Experimental Study on Riser Gas Expansion and Unloading by O. Kaldrim and J. Schubert, Texas A&M University.
Upward Gas-Liquid Flow in Concentric and Eccentric Annular Spaces by P.C. de Sousa, Texas A&M University; G. Falcone, Clausthal University of Technology; and M. Barrufet, Texas A&M University.
Dynamics of Gas Kick Migration in the Annulus While Drilling/Circulating by C.E. Obi, K. Manikonda, L. Abril, R. Hasan and M. Rahman, Texas A&M University.
Adeshina Badejo is a petroleum engineering PhD student at Texas A&M University under the Texas A&M at Qatar Strategic Research Initiatives Program. He has a strong interest in reducing the environmental impact of the continued use of fossil fuels. His research focuses on flow assurance challenges of the CO2 value chain from the extraction point to the subsurface injectivity point with the integration of machine learning. Badejo has been actively involved with SPE since 2016 as a volunteer. He led the Heriot-Watt University PetroBowl team to the regional qualifiers in Zagreb, Croatia, and received the 2023 SPE Aberdeen Section Student Bursary Award. He also served as the 2018–2019 SPE Programs chairperson during his undergraduate studies and co-initiated the inaugural edition of The Industry Discourse, a student-led energy conference. He holds a master’s degree in subsurface energy systems from Heriot-Watt University and a bachelor’s degree in petroleum and gas engineering from the University of Lagos, Nigeria.
Chinemerem Edmond Obi is a graduate of the Harold Vance Department of Petroleum Engineering at Texas A&M University. He holds MS and PhD degrees in petroleum engineering. He specializes in solving complex fluid flow challenges in the energy industry. His doctoral research was conducted under Rashid Hasan. Beyond his academic achievements, Obi is an active volunteer and avid explorer. He has worked offshore in the Gulf of Mexico, onshore in west Texas, and LNG sectors. Obi's passion for volunteering and knowledge shapes his approach to learning and mentorship. In his free time, he enjoys sports, chess, music, and engaging with people.