Further Development of FLNG Concept Based on Offshore Associated Gas
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This report assesses the technical and economic feasibility of associated gas utilization, based on deepwater oil production in Brazilian fields. In many cases, offshore oil production involves significant amounts of associated gas, which can be reinjected or exported by pipeline. However, there may be limitations on how much gas that can be reinjected, and deepwater locations far from shore may not be favorable for pipeline export. The following gas utilization scenarios are evaluated, with a focus on the FLNG concepts: FLNG receiving gas from one or multiple FPSOs, possibly combined with subsea gas/liquid separation Small-capacity gas processing and liquefaction unit on FPSO Gas pipeline to shore (rich gas transport) Marine Compressed Natural Gas (CNG) transportTwo different cases have been applied for evaluation of the scenarios; a high GOR (gas-to-oil ratio) case, and a low GOR case. Simplified process simulations are performed for oil processing on a FPSO with a capacity of ca 120 000 bpd, in addition to gas processing and liquefaction of the associated gas. For low rates of produced gas from oil processing, integrated small-capacity gas processing and liquefaction unit on a FPSO is evaluated as a technical feasible solution. PRICO or N2 expander process is suggested as liquefaction technology. For higher rates of associated gas, the gas can be transferred from a FPSO to a separate FLNG vessel. DMR, PRICO and N2 expander processes are considered for gas liquefaction. Condensate produced on the FLNG can be transferred back to the FPSO, as no riser system on the FLNG is assumed, and to avoid a storage and offloading system for condensate on the FLNG. If CO2 is reinjected to avoid venting, additional transfer hoses between the FLNG and FPSO are required. The transfer lines increase the complexity and risks for this gas utilization scenario. Subsea separation supplying a FPSO and a FLNG is a solution to eliminate the transfer lines between the two vessels. However, there are uncertainties related to costs for this scenario. Vessel layout, process design and energy system of the FLNG concepts are evaluated. Availability, complexity and technical risks are discussed and compared to pipeline and marine CNG. An economic analysis based on NPV, creates a rough estimate of the value of the projects. Based on the given economic data, pipeline transport and marine CNG appear most valuable for both the high and low GOR case, but all projects show positive and robust NPV.Pipeline appears to be the most favorable option for several criteria. Marine CNG does similarly come out as a promising option, but uncertainties related to costs and offloading solutions are currently a drawback for the scenario. FLNG is considered as a technical feasible option for utilization of associated gas based on deepwater oil production, but the related costs of a FLNG project remain a challenge. The economy of a FLNG project depends on domestic and international LNG markets and prices. The FLNG technology is developing, and companies may invest in FLNG projects due to market expectations and/or a desire to be innovative and on the forefront of future technologies.