Abstract
Based on the mechanistic model of the two-phase swirling annular flow behavior, a calculation method for the effective distance of vortex tool is obtained by taking Kelvin–Helmholtz instability into account. The rationality of the proposed method is validated by comparing the predicted liquid film thickness and pressure under non-swirling flow with the commonly used correlations. Then, the influences of gas–liquid ratio, helix angle, and hub diameter of vortex tool on the liquid film thickness, pressure drop, and effective distance have been analyzed. Results show that the presence of the vortex tool causes the decrease in the liquid film thickness and increase in the pressure drop. The liquid film thickness increases gradually as the helix angle and the hub diameter increase, and the larger helix angle results in smaller pressure drop. The effective distance increases with an increase in the gas–liquid ratio and decreases with an increase in helix angle and hub diameter. A sudden decrease occurs when the helix angle exceeds 60°. The gas–liquid ratio and helix angle are more dominant factors than the hub diameter on the liquid film thickness, pressure drop, and effective distance.
Highlights
Swirl flows have a variety of applications in the oil and gas industry, such as in casing turbulators,[1] rotary gas separators,[2] and vortex tools,[3] due to good separating properties and conveyance performance
The main objective of this study is to establish a prediction model of the swirling annular flow behavior induced by the vortex tool based on the force balance of liquid film, and derive a calculation method for the effective distance of interfacial disturbance wave, in which the Kelvin–Helmholtz (KH) instability was taken into account
A mechanistic model is established for the prediction of the swirling annular two-phase flow behavior in the downstream of the vortex tool, which is helpful to understand and recognize the difference of the dynamic characteristics of swirling and non-swirling flow
Summary
Swirl flows have a variety of applications in the oil and gas industry, such as in casing turbulators,[1] rotary gas separators,[2] and vortex tools,[3] due to good separating properties and conveyance performance. The vortex tool is a newly developed downhole equipment to unload liquid and restore continuous production of low-rate gas wells. It has no moving parts and does not need additional energy source. Field tests and laboratory experiments[3,4,5] revealed that the vortex tool was able to lower the critical gas velocity, reduce the tubing pressure loss, and improve the liquid-carrying capacity of gas wells.
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