Injectable venturi for slug control.

Severe slugging is a cyclic flow regime which causes intermittent delivery of oil and gas, which could lead to flow separator flooding, production reduction, platform trips and plant shutdown. The large and rapid variation in flow reduces the average flow output, which could be as large as 50 %. This relative inefficiency results in substantial profit losses. This study presents novel methods for severe slugging mitigation. It describes the use of a Venturi and an injectable Venturi for the improvement of system stability, increase in production and hydrocarbon recovery. An injectable Venturi is a Venturi tube that has an opening at its throat, and a pipe inclined at 45° is inserted into this opening. Thus, gas is injected counter to the flow coming from upstream of the injectable Venturi to choke the working fluid passing through the throat of the injectable Venturi. Flow regimes maps, stability maps, stability curves, severe slug envelopes and Hopf bifurcation maps were generated and used to demonstrate the performance of the Venturi and the injectable Venturi in mitigating severe slugging in a pipeline-riser system. The results from the experiment show that with the Venturi or injectable Venturi coupled to the pipeline-riser system, severe slugging was mitigated, the severity of severe slugging was reduced, the operating region of severe slugging was reduced, and stability was achieved at a larger valve opening and lower riser base pressure. Practically, these results imply an improvement to the stability of the system and increase in oil and gas production. Also, these results indicate that oil and gas production can proceed more smoothly, thus, enhancing flow assurance. Potentially, these results will help to extend the operational life of a reservoir further, thus enhancing oil recovery, safe and continuous production of low-pressure wells.