Techno-Economic Comparison of Self-Lift and Gas-Lift Slug Mitigation in Deepwater

Abstract With the most recent down turn in the oil industry, there is an urgent need to optimize production from deepwater oil fields. Adopting a technically sound and cost-effective severe slug mitigation technique is very important. In this work, a sample deepwater oil field in West-Africa operating at over 1000m water depth, currently operating at over 150,000 bbl/d and with an oil API of 47 °, GOR of 385.91 Sm3/Sm3 and a water-cut of over 10%; experienced slugging during it’s early life. This slugging scenario was modelled and subsequently fine-tuned to severe slugging by moderating the flow rates. Self-lift and Gas-lift were then separately applied to mitigate the severe slugging scenario. The results of this work highlighted that the self-lift technique proves effective for valve openings of 0.85, 0.65 and 0.35 for a 4 inch and 3 inch diameter bypass line. The gas lift technique proved effective with increased mass flow rate from 7kg/s and 12kg/s. Although both techniques mitigated the severe slug, the power consumption required by the gas lift technique for 12kg/s the best scenario proved to be huge at about 75,921,254.54 kw and at over $10,000,000 (USD) cost. This was not the case with the self-lift technique which required no external power source for its functionality.