Experimental study on gas-liquid-coal fines three-phase flow in undulating pipeline

Abstract

Original scientific paper https://doi.org/10.2298/TSCI171218162WThe aggregation of coal fines particles at the bottom of the coal-bed methane well is a common occurrence during production, which could inhibit the flow in the bottom of wells and have adverse effect on the downhole equipment. In this work, gas-liquid-solid three-phase flow experiments were carried out to investigate the migration and discharge of coal fines particles in undulating pipeline. The experiments were conducted in downbent V-shaped pipes with different inclination angles. Based on the conductivity method, the real-time liquid holdup at three positions of the elbow was measured by the developed software. The slugs were identified on the time series curves of liquid holdup, and the characteristics of each slug were calculated, such as length and translational velocity. Meanwhile, the moving of particles with different size and concentration can be observed through visualized flow channel. The dyed coal fines particles are injected into the multiphase flow loop. By observing whether they can be discharged from the V-shaped pipe, the lower limits of superficial gas and liquid velocities to avoid particle retention at the elbow were determined. A correlation to predict the critical gas and liquid velocity was presented, and the accuracy of the calculation model was verified in comparison with the experimental results.

A Case Study on the Fracturing Radius and Time Effects of CO2 Phase Transition Fracturing in Coal Seams

“…It is generally believed that the CPTF zone can be divided into three zones: crushed zone, crack zone, and vibration zone [17,19]. In order to further determine the range of the crack zone caused by phase transition fracturing, in this work, chromatographic analysis was performed on the gas extracted from the 14#, 26#, 31#, 3#, and 10# boreholes before and after fracturing, and the changes in CO 2 content from those boreholes before and after fracturing are observed and recorded.…”

“…Dong et al [16][17][18] studied the mechanism of CPTF, and calculated the equivalent weight of TNT. In addition, Wang et al [19,20] conducted the field tests and achieved an ideal penetration effect. Song et al [21] showed that the fractured radius of liquid CO 2 in coal seam is 12 m via field tests.…”