The accurate prediction of two-phase gas and liquid flow regimes is important in the proper design, operation and scale-up of pressure management and fluid handling systems in a wide range of industrial processes. This paper provides a comprehensive review of 3947 published experimental data points for gas-liquid flow maps in vertical pipes and annuli, including a critical analysis of state-of-the-art measurement techniques used to identify bubble, slug, churn and annular flow regimes. We examine the critical factors of pipe geometry (diameters, deviation from vertical), fluid properties and flow conditions that affect the transition from one flow regime to another. The review surveys the theoretical models available to predict flow regime transitions, and we validate the accuracy of these models using the published experimental data. The most reliable flow regime transition models for Moreover, based on the review we provide an outlook on the research needs and important developments in prediction of two-phase flow in vertical pipes including the use of computational fluid dynamics (CFD) techniques to simulate gas-liquid flows in vertical geometries.

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Coal seam gas (CSG) well operators typically follow an industry rule of thumb 0.5 ft/s liquid velocity to prevent the onset of gas carryover during CSG dewatering operations. However, there is very little experimental data to validate this rule of thumb with only a publication by Sutton, Christiansen, Skinner and Wilson [1] available in the open literature. A review of more general studies on two-phase gas-water flows in vertical pipes and annuli revealed that experimental conditions, especially pipe and annuli diameters, can have a significant impact on development of two-phase flow phenomena. As such, the limited available data may not be applicable due to differences in experimental conditions. This study experimentally investigates the onset of gas carryover using an experimental setup intended specifically for the study of CSG wells. The University of Queensland Well Simulation Flow Facilities were designed to replicate as closely as possible the production zone of a typical vertical CSG well in Queensland, Australia in transparent acrylic pipes to observe two-phase flow behavior in simulated downhole conditions. The annular test section in the rig was constructed of a 7-in casing and 2¾-in tubing. Modification of the experimental setup to include a vertical separator allowed for the detection of gas carryover. Conceptual demonstrations of gas carryover were captured and have been illustrated. The experiments in this study validate the industry rule of thumb of 0.5 ft/s liquid velocity as an appropriate guideline for onset of gas carryover in a casing-tubing annulus dimension similar to a typical CSG well in Queensland.

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Counter-current two-phase gas-liquid flows in annuli occur in many industrial applications, including coal seam gas (CSG) production. In CSG wells, gas is typically produced through counter-current gas-water flow in an annulus. Yet, the models used by CSG companies were designed for conventional wells, wherein co-current upward gas-liquid flow occurs in pipes. Accurately predicting the ensuing flow regimes and counter-current flow limitation (CCFL) is important because they are intrinsically linked to flow characteristics, and dictate operating conditions. The CCFL describes the onset of co-current upward or downward flow due to high gas (gas flooding) or liquid (liquid flooding) rates, respectively. There are currently no experimental publications on counter-current gas-liquid flow regimes in annuli, prohibiting predictive models from being validated. I collated 3,947 flow regime results from 35 experimental studies of counter-current flows in pipes and co-current flows in pipes and annuli, and confirmed that flow configuration, channel geometry, and fluid properties can significantly influence flow regimes (Chapter 2). This thesis aims to experimentally characterise flow regimes and the CCFL during counter-current two-phase flows in an annulus. These findings will allow predictive models of counter-current flow regimes in annuli to be validated.To study counter-current flow regimes in an annulus (Chapter 3), I designed and built an experimental apparatus using acrylic pipes with annulus diameters of 170 mm and 70 mm (170/70 annulus). Flow regimes and the CCFL were documented for air-water at standard conditions using combinations of superficial gas velocities within 0.014-5.794 m/s and superficial liquid velocities within 0.004-0.240 m/s. Differential pressure data were recorded over 1 m and used to infer void fractions, and to quantitatively assess the flows using fast Fourier transform (FFT). High-speed video images were captured at 4,000 frames/s. An apparatus with annulus diameters of 44 mm and 19 mm was also assembled to investigate the impact of annulus size.My observations confirm the 170/70 annulus is a large annulus in which stable slug flow regime cannot develop due to Rayleigh-Taylor instability. Subsequently, the flow regimes in this system are described as homogeneous and heterogeneous instead of bubble and slug-churn regimes.Churn-annular flow was observed, but, the CCFL was reached before a fully annular regime could develop. Existing empirical correlations for the CCFL only considered gas flooding and performed poorly when assessed against my experimental results. So, I developed an empirical correlation for the CCFL that also incorporated liquid flooding. Liquid flooding was detected using a novel experimental technique developed in Chapter 5. Essentially, a water barrel beneath the annulus, used for water re-circulation, was dual-purposed as a vertical separator. The proposed correlation for CCFL ii in an annulus is * 1/2 + 1.7 * 1/2 = 0.56, where * and * are the dimensionless gas and liquid s...

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