Sand erosion model improvement for elbows in gas production, multiphase annular and low-liquid flow

Solid particle erosion has been long recognized as a potential problem in oil and gas production systems. The most vulnerable parts of production systems tend to be components in which the flow direction changes suddenly such as elbows and tees. This study focuses on the validation and improvement of mechanistic models that have been developed to predict sand erosion rates in elbows under gas, annular and low-liquid flow conditions in vertical and horizontal flow orientations.;Experimental data has been collected in a large-scale multiphase flow loop with 76.2 mm (3 inch) standard elbows. Erosion data has been obtained in a CPVC test cell with an elbow specimen, Electrical Resistance (ER) probes and state-of-the-art temperature compensated multiple ultrasonic (UT) sensors. Erosion experiments were conducted at low pressure conditions varying gas (air) and liquid (water) velocities with three different particle sizes at low concentration. It is found that the location of highest erosion for single-phase (gas) flow with sand and gas-liquid annular flow with sand is around 45° to the bend for these low pressure conditions. It was found that differences in flow patterns between the vertical and horizontal orientations can cause erosion rates to be different by a factor of 7 in some cases. Additionally, it is found that increasing the particle size resulted in increased wall thickness loss values due to the sharpness of larger sand particles used in the experiments.;In order to better understand the mechanisms governing exchange and transfer of momentum between the liquid film and the gas core in annular two-phase flow, gas-liquid measurements are conducted with the aid of a dual Wire-Mesh Sensor (WMS). The obtained multiphase flow characteristics data are utilized successfully for discriminating stable and unstable annular flows.;Different erosion equations have been generated based on small-scale erosion testing of oilfield materials in air. Since sand particle impact speed with a metal surface greatly influences erosion rates of the material, sand particle velocities were measured by Particle Image Velocimetry (PIV). The new erosion models have been implemented into a commercially available CFD code and a current one-dimensional (1D) procedure to predict erosion rates for a variety of flow conditions. Results from the 1D procedure were compared with present erosion data and results were reasonably agreeable.;With the experience obtained from the experimental investigation, the E/CRC erosion prediction model, Sand Production Pipe Saver (SPPS-1D), has been modified and improved by incorporating new erosion equations and an initial particle velocity modification for unstable vertical annular flow. Additionally, the flow orientation effect has been included in the 1D model for horizontal annular flows. Direct comparisons of these modeling results with experimental erosion ratios show that the results obtained agree better with the trends of the experimental data than the original model.