Low-liquid loading (LLL) and annular gas-liquid flow patterns are commonly encountered in gas transportation pipelines. They may also occur in other off-shore production facilities such as gas/condensate production systems. Experience gained from production of hydrocarbons has shown that severe degradation of production equipment will occur due to sand entrained in gas-dominant multiphase flows.
Sand erosion in multiphase flows is a complex phenomenon since several factors influence the particle impact velocity with the wall. In order to give a more comprehensive understanding of the particle erosion process in this particular scenario and to improve the current semi-mechanistic models, erosion and sand distribution measurements were conducted on 76.2 mm (3 inch) and 101.6 mm (4 inch) diameter pipes in a large scale multiphase flow loop with varying gas (air) and liquid (water) velocities generating low-liquid loading and annular conditions. Particle sizes used in the experiments were 150 and 300 microns with the latter being sharper than the former. Erosion measurements were made at sixteen different locations on a 76.2 mm (3 inch) standard elbow using ultrasonic technology, whereas Electrical Resistance (ER) probes were used for the measurements in a 101.6 mm (4 inch) diameter pipe. The experiments were primarily performed in the upward vertical orientation but a few measurements were performed in the horizontal orientation. Results suggest that the erosion is an order of magnitude higher when the pipe is oriented vertically compared to horizontal orientation. Also, the location of maximum erosion is identified for these flow patterns and it is not dependent on the pipe inclination.