Erosion in multiphase pseudo slug flow with emphasis on sand sampling and pseudo slug characteristics

Erosion is a complex problem faced by oil and gas producers especially when occurring in multiphase flows. Sand erosion in the oil and gas industry not only causes economic losses resulting from repairs and decreased production but also causes safety and environmental concerns. Commonly, pipelines operated by oil and gas producers carry multiple fluids simultaneously with slug flow as a dominant flow pattern. Thus, this investigation focuses on understanding slug flow erosion in horizontal pipes.;Initially, the erosion magnitudes for various slug flow operating conditions are studied using Electrical Resistance (ER) probes: two in a bend and another mounted in a straight pipe section. After obtaining the local measurements of erosion using ER probes, erosion patterns are measured for various slug flow conditions using a state-of-the-art NanoUT (non-invasive Ultrasonic Technology) device. The metal loss is measured at 16 different locations in the elbow using dual element ultrasonic transducers. For all the erosion experiments performed with ER and UT technologies, three different particle sizes (20 &mgr;m, 150 &mgr;m, and 300 &mgr;m) and three different liquid viscosities (1, 10, and 40 cP) were considered. It is found from the ER and UT measurements that with an increase in either particle size or superficial gas velocity the erosion magnitudes increased. Additionally, it is found from the UT measurements that the pattern of erosion for slug flow is entirely different from other flow patterns. The location of the maximum erosion is measured at the top of an elbow for slug flow conditions in horizontal flow.;In order to better understand the slug flow erosion pattern and magnitudes of measured metal loss, sand sampling studies and multiphase flow characterization studies were performed. The sand sampling studies were performed using both an intrusive probe and sampling ports. It is found from the sand sampling measurements that there is a uniform distribution of liquid and sand in the outside bend, as opposed to the measurements inside a straight pipe. Additionally, the influence of the superficial gas velocity and liquid viscosity on the radial sand distribution inside an elbow is presented and the sand distribution measurements are related to understanding erosion. For the experimental investigations, a state-of-the-art conductance based dual Wire-Mesh Sensor (WMS) is utilized to characterize slug flows at higher superficial gas velocities. Slug length, slug frequency, interfacial velocity distribution, average void fraction distribution, and slug void are extracted from WMS data. The obtained slug characteristics data are utilized in successfully discriminating slug and pseudo slug flows. With the experience obtained from the experimental investigation, the Sand Production Pipe Saver (SPPS) one-dimensional (1D) model has been modified by incorporating the erosion from the Taylor bubble region and successfully integrating slug and pseudo slug characteristics.