Department of Chemical & Petroleum Engineering

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Browsing Department of Chemical & Petroleum Engineering by Subject "Choking"

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  • Item
    Open Access
    Attenuating Severe Slug Flow at Large Valve Opening for Increased Oil Production Without Feedback Control Signal
    (Elsevier B.V, 2016) Ehinmowo, A.B; Orodu, O.D; Anawe, P.A; Ogunleye, O.O
    In the co-current flow of gas-liquid mixtures through pipeline-riser system, severe slugging is frequently encountered and manifests in significant fluctuation of flow and pressure. This can pose serious threat to production facilities. The most common method for its mitigation is by choking which unfortunately could negatively affect production. The objective of this study therefore is to develop a technique that can help stabilise the system and maximise production simultaneously. In this paper, a new general method for multiphase flow system stability analysis was proposed based on a new passive attenuation method – the intermittent absorber. A series of experiments were carried out in a 4″ pipeline-riser system which is 55 m long with horizontal pipe inclined at 2° connected to 10.5 m high catenary riser followed by 3 m horizontal topside section. Air and water were used as experimental fluids. Numerical studies were also conducted on a 4″ pipeline-riser system to proof the concept. The results showed that the intermittent absorber possess potential for stabilising severe slug flow at larger valve opening and lower pressure. For the case studied, up to 9% reduction in the riser base pressure was reported which practically implies increased oil production.
  • Item
    Open Access
    Experimental Investigation of Hydrodynamic Slug Mitigation Potential of an Intermittent Absorber
    (Elsevier B.V, 2016) Ehinmowo, A.B; Ogunleye, O.O; Orodu, O.D
    The need to handle hydrodynamic slugs in a more efficient way becomes important as oil and gas activities shift deep offshore. This study describes the use of a vessel coupled to the pipeline-riser system upstream of the first stage separator for hydrodynamic slug attenuation. The experiments were carried out in a 2 pipeline-riser system which comprises of a 40 m long horizontal pipe connected to a 11 m high vertical riser followed by a 3 m horizontal topside section. Air and water were used as experimental fluids. Bifurcation maps and slug attenuation index (SAI) have been used to quantify increase in oil production and the slug attenuation potential of this concept. The device was observed to reduce the pressure fluctuations characterising hydrodynamic slug flow up to 22%. The device also provides additional benefits of stabilising the flow at higher valve opening (choke setting) and lower pressure compared to traditional choking. This in practice translates to increase in oil production. Special case of hydrodynamic slugs which exhibit overchoking induced slugging (OIS) was also observed to be relatively attenuated by the introduction of the absorber.