Study on sand particle transport characteristics below the screw pump in a sand producing oil well based on laboratory experiments and numerical simulations

Progressing cavity pumps (PCPs) are widely utilized in sand-producing wells in the northern Zhaqi Oilfield due to their sand-carrying capability. However, when sand volume increases, sand particle diameter enlarges, or formation pressure significantly decreases, their sand-carrying capacity gradually diminishes. Sand particles that cannot be pumped to the wellhead settle and accumulate in the wellbore, leading to sand burial of the production layer, blockage of the oil flow path, and ultimately well shutdown. To investigate the migration characteristics and performance of sand particles below the pump during PCP operation and to achieve cost reduction and efficiency improvement, the migration patterns and settling characteristics of formation sand from the perforation entrance to the pump inlet were studied. By analyzing the overall tubular structure and working principles of PCPs during sand-carrying oil production, it was found that sand particles are transported by formation fluids in the wellbore and annulus. Using laboratory experimental setups, a CFD-DEM coupled model, and the control variable method, comparative studies were conducted on sand particle migration in the wellbore below the pump, the central annulus, and the eccentric annulus. Additionally, the effects of fluid characteristics, sand particle properties, and wellbore features on sand migration performance were analyzed. The results indicate that sand particle migration performance in the central annulus is superior to that in the wellbore and the eccentric annulus, with the eccentric annulus exhibiting the poorest migration capability. This research not only provides a significant theoretical basis for optimizing the design of PCP oil production systems but also offers practical guidance for addressing sand-carrying issues in actual production.