摘要
Separate-layer injection of CO2 is an important method to improve oil and gas production and recovery.Conventional single-stage nozzle is usually blocked by impurities,and the ice-barrier phenomenon is very common.To solve this problem,large-diameter multi-stage circumfluence nozzle was designed to release pressure stage by stage.In order to illuminate the throttle characteristics of the CO2 multi-stage circumfluence nozzles,numerical simulation was performed to test several nozzles with different diameters and stage numbers.Furthermore,we tested the throttle characteristics through laboratory experiments and obtained the effects of several critical parameters such as nozzle diameter,number of stage and pressure drop on the throttle characteristics.The results show that the flow rate decreases as the nozzle stage increases on the condition of constant pressure and nozzle diameter.And pressure difference increases as nozzle stage number increases under the constant flow rate.The throttle capability of multi-stage circumfluence nozzles was much better than the concentric nozzles.Large-diameter multi-stage nozzle is recommended rather than small-diameter single-stage nozzle during the process of separate-layer injection,which can efficiently prevent impurities and ice blocking.The results are expected to provide a theoretical support for the nozzle choice of separate-layer injection of CO2.
