Ultrasonic measurements of sand particle erosion under upward multiphase annular flow conditions in a vertical-horizontal bend

Abstract

Particulate gas-liquid upward annular flow can be often observed in the oil and gas industry during production. This type of flow, of course, can be very erosive, as it is associated with high gas flow rates. Despite the interest due to this potentially devastating problem, most previous studies have tended to focus on erosion under single-phase flow conditions. Therefore, the aim of the present research was to extend the current knowledge of erosion in multiphase flow and also to broaden the erosion data bank of the Erosion/Corrosion Research Center (E/CRC).Different sets of experiments were conducted in a 76.2mm ID standard vertical–horizontal elbow to obtain erosion patterns and magnitudes. Prior to sand injection, in the vertical pipe before the elbow, the following air-water multiphase flow regimes were established: a) unstable annular flow with upward and downward oscillatory motion of the liquid, b) annular flow, and c) very low liquid-high gas flow rate annular flow. Superficial liquid and gas velocities ranged from 0.003m/s to 0.482m/s and from 11m/s to 49m/s, respectively.For erosion measurements, a non-intrusive ultrasonic device was employed which enabled wall thickness measurements at 16 discrete locations on the elbow before and after each experiment. The effects of superficial gas and liquid velocities, and particle size on erosion rates and patterns were investigated. In summary, erosion increased, when particle size and/or gas flow rate increased. However, when the superficial liquid velocity increased, two different trends were observed; for higher superficial gas velocities, erosion first decreased and then after reaching a minimum, increased. The trend was reverse for lower gas flow rates.