Solid-Particle Erosion in Slug Flow

Abstract

Abstract Sand erosion in multiphase flow is receiving widespread attention from the oil and gas industry. Several tools to predict erosion have been developed. One tool, called SPPS (Sand Production Pipe Saver), predicts penetration rates (pipe thickness loss rate) in fittings such as elbows. This tool accounts for many different operating conditions and can also be used to predict threshold flow rates that will result in only a tolerable amount of erosion. The SPPS model can be used to help avoid major pipeline failures, plan inspections and maintenance, develop cost to benefit projections, or estimate life expectancy of a pipeline for known flow conditions and sand production rates. Many flow regimes can occur in multiphase flow. This study focuses on the flow properties that effect sand erosion rates for slug flow. Experiments were conducted and a mechanistic flow model was developed. Erosion data were obtained for slug flow through an elbow and in a straight section of pipe. Erosion data show the effects of varying the superficial liquid and gas velocities, the liquid viscosity, the sand size, and sand rate. Data acquisition was accomplished through electrical resistance (ER) probes. Two flat-head ER probes were positioned in an elbow at 45° and 90° flush with the pipe wall. One intrusive probe was deployed in a straight section and protruded into the flow. Increasing the superficial gas velocity in these flow regimes extensively increases the erosion rate while increasing the superficial liquid velocity does not significantly increase erosion. Increased viscosity decreases the impacting velocity of impinging particles, and thereby reducing the magnitude of erosion on the pipe wall. The affect of particle size has been investigated and found to vary with viscosity. These trends were also found to vary with location of the probe. A mechanistic erosion model was also been developed. Model results are compared with sand erosion data. Predicted erosion rates from the model developed during this investigation agree well with the data collected in the present work and in previous studies.