Use of pressure signal analysis to characterise counter-current two-phase flow regimes in annuli

Wu, Benjamin; Ribeiro, Ayrton; Firouzi, Mahshid; Rufford, Thomas E.; Towler, Brian F.

doi:10.1016/j.cherd.2019.11.009

Cited by 24 publications

(11 citation statements)

References 33 publications

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“…Larger values of permutation entropy indicate the time series is composed of shorter growth trends. A reverse in trend for Shannon entropy, with increasing gas rate, and cut-off value of 0.88 for permutation entropy were determined in Chapter 4 (Wu, Ribeiro, et al, 2019), and proved to be effective for the tested saline water flows. The post-heterogeneous transition boundary was unaffected by salinity and consistently occurred at a superficial gas velocity of 3.555 m/s, see Figure 6-8.…”

Section: Presentation Of Data and Resultsmentioning

confidence: 96%

“…When considering air and water (accounting for salinity) at standard conditions, the greatest observed difference in pressure was a decrease of 532 Pa/m (0.02 psi/ft) at a superficial gas velocity of 0.531 m/s when using 11,198±142 ppm NaCl instead of fresh water. To objectively identify the flow regimes that developed we implemented the signal analysis techniques of autocorrelation, PSD, Shannon entropy and permutation entropy detailed in Chapter 4 (Wu, Ribeiro, et al, 2019). The autocorrelation function assumes that each data point is dependent upon its predecessors and determines the importance of information on past data values for predicting future data.…”

Section: Presentation Of Data and Resultsmentioning

confidence: 99%

“…The content of this chapter is based on: Wu, B., Firouzi, M., Ribeiro, A., Rufford, T. E., and Towler, B. (2019)…”

Section: Chapter 6 Investigating the Effect Of Salinity On Counter-cumentioning

confidence: 99%

“…Time-averaged void fractions were inferred from differential pressure measurements, see Chapter 3, that were captured at a sampling rate of 100 Hz sampling, and averaged over a 30 s sampling period. A sampling period of 30 s was confirmed to be sufficient for pressure fluctuation signal analysis in Chapter 4 (Wu, Ribeiro, et al, 2019). Additionally, high-speed video images were captured using a Photron Fastcam Mini UX100 operated at 125 frames/s with a shutter speed of 1/5,000 s. A frame rate of 125 frames/s allowed us to capture video recordings over longer time periods whilst producing manageable uncompressed file sizes.…”

Section: Description and Application Of Equipment And Processesmentioning

confidence: 99%

“…These water salinities are above and below the critical salt concentration for NaCl of approximately 7,600 ppm (0.13 Molar), the concentration above which NaCl was found to significantly inhibit the coalescence of gas bubbles . The flow regimes that ensued were objectively identified and characterised using the procedure developed in Chapter 4 (Wu, Ribeiro, et al, 2019), This work gathers empirical data on the influence of salinity on flow regimes. In doing so, improving the ability to predict and quantify flow behaviour in CSG operations with saline associated water.…”

Section: Introductionmentioning

confidence: 99%

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The experimental study of counter-current two-phase flows in annuli

Wu¹

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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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Section: Presentation Of Data and Resultsmentioning

confidence: 96%

Section: Presentation Of Data and Resultsmentioning

confidence: 99%

“…The content of this chapter is based on: Wu, B., Firouzi, M., Ribeiro, A., Rufford, T. E., and Towler, B. (2019)…”

Section: Chapter 6 Investigating the Effect Of Salinity On Counter-cumentioning

confidence: 99%

Section: Description and Application Of Equipment And Processesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%