In this study, a deepwater pipeline-riser system that experienced hydrates was modelled in MAXIMUS 6.20 (an integrated production modelling tool) to understand, predict and mitigate hydrates formation in typical deepwater system. Highlights of the results from this study suggest that the injection of low-dosage hydrate inhibitors (LDHIs) into the hydrate-forming structures within the multiphase flow stream disperses the hydrates particles in an irregular manner and subsequently decreases the nucleation rate of the hydrate and prevents the formation of hydrates. This study found that the cost of using monoethylene glycol was significantly higher than that of LDHI by over $500/day although low-dosage hydrate inhibitors have initial relatively high CAPEX. In the long run, its OPEX is relatively low, making it cost-effective for hydrate inhibition in deepwater scenarios.
Separation of gas-liquid mixture, which is achieved by using either large gravity separators or compact separators is a common and vital operation in the petroleum industry. Where space and cost are key project considerations, gas-liquid compact separators are very attractive because of their versatility and cost effectiveness. Efficiencient performance of the cyclonic separator depends on smooth and steady swirling flow. Unsteady swirling flow in the separator may be due to capacity constraint, improper design or unforeseen flow instability at the inlet. An understanding of phase distribution in gas discharge section of these separators would help design engineers make a better decision when selecting and sizing inlet nozzle, diameter and length of the separator. In this paper, the structure of phase distribution and liquid holdup in the gas discharge section of the separator was obtained using a 24x24 resolution wire mesh sensor (WMS). The acquired area average liquid holdup and the images were analysed using time series and 2D slice to discriminate between partial separation and critical separation condition.The liquid holdup as a function of separator inlet superficial velocity was quantified.
Nigeria recently endorsed the World Bank's zero routine flaring by 2030 initiative and raised her own goal to 2020. As a step towards achieving the 2020 flare out goal, the Ministry of Petroleum Resources has established a national gas flare commercialization framework. Under this framework, licenses would be issued to third parties who would become off-takers of the gas. While this framework presents opportunity for investment, most of the oil fields where the gas is being flared may be far from existing pipelines and process infrastructures. Additionally, flare gas is often associated with volume, composition and pressure fluctuations, which make technology selection for its utilization more challenging. This paper reviewed some technologies for flare gas recovery and utilization, and identified promising technologies with capabilities of handling flare gas volume below 1 MMscfd. Mini gas-to-liquid (mini-GTL) technologies for producing diesel, methanol and anhydrous ammonia developed by Greyrock, GasTechno and Proton Ventures, respectively, were selected. The technical viability and economic benefits of these technologies were evaluated based on feed gas rate of 500 Mscfd. While all the technologies are technically viable, the gross profit margin of the GasTechno's miniGTL technology with methanol as the GTL product was found to be more attractive.
Previous studies in literature and field experience indicates that hydrates mitigation can increase production cost by 15%. Hence, the need for optimum hydrates inhibitor selection. In this study, a deepwater oil field; currently producing at over 100,000 bbl/d had experienced hydrates and an integrated production modelling approach was utilized to model this scenario via MAXIMUS 6.20. The key input data to model were reservoir pressure at 2650 psia; Oil API Gravity at 35.4 °API; GOR at 1324 scf/stb and the produced water rate at an average of 3138 STB/d. Key results indicates that the injection of LDHI into the hydrate lattice within the hydrocarbon stream dispersed the hydrates particles in an unsteady manner and subsequently prevented the formation of hydrates at 40 gal/day. The cost of using LDHI was lower by over $520/day, from simulation results. This study also assessed technical benefits and challenges of using LDHI and MEG in deepwater scenario.
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