Abstract:
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.