Oil&Gas Decarbonization: Low-Carbon Fuels and Carbon Capture & Storage Offshore Power Barges, a Comprehensive Concepts Comparison

Abstract The objective of this paper is to present and compare two concepts to decarbonize Oil&Gas production facilities, particularly remote deep-offshore assets. The two offshore power barges concepts, called PGU (Power Generation Unit) are either based on low-carbon fuels or on local Capture & Storage to supply low carbon power & enable offshore facilities electrification. One of the main challenges of the Net Zero ambition for the Oil&Gas industry (scope 1 and scope 2) is the reduction of GHG emissions related to the fuel gas consumption for power generation (>70% of the CO2 emissions), particularly for offshore remote sites where Power from Shore is not feasible. Centralized floating Power Generation Units (PGU) can be connected to existing platforms and/or FPSOs to supply low carbon electricity. Either with an offshore PGU fed with low carbon fuels (green or blue ammonia). The PGU include all the functions to store, treat & convert ammonia into a blend of hydrogen and ammonia. Either with an offshore PGU with carbon capture and injection into a local CO2 storage (CCS). The PGU includes a compact backpressure combined cycle, a post combustion solvent based (MEA), a capture package designed for 95% CO2 removal. Some units are directly integrated in the structure of the hull to optimize weight & space. 325 MWe of net electrical power are generated. This low carbon power is exported from the PGU to existing offshore facilities equipped with single cycle gas turbines (<40% efficiency, 500 gCO2/kWh). This decarbonized power is exported through subsea electrical cables. The two concepts are compared in term of technical feasibility, maturity, GHG reduction and costs. A Life cycle analysis was performed to evaluate the environmental impact. These low carbon power generation solutions (30 gCO2/kWh) enable to stop gas turbines on site. The two concepts result in similar floaters dimensions and Capex, with a higher Opex for the carbon free fuel due to fuel cost. The offshore CCS concept is seen as a shorter-term solution, applicable in the current decade, main challenge being the availability of an adequate CO2 storage to ensure a sustainable local reinjection. R&D focus on technology innovations to reduce costs. As an alternative, the offshore NH3 PGU concept is a longer-term solution for hard to abate sites, where CO2 reservoir availability can be an issue. A Life Cycle Analysis (LCA) shows that ammonia chain shall be green or fully sequestrated. R&D is driven by the need for new technologies, fully fuel flexible Gas Turbines to address multiple low carbon fuels scenarios. These developments shall be started now to enable this concept when the low carbon fuel market will be ready. The novelty relies on the development and comparison of offshore power barges concepts delivering a minimum of 325MWe, either based on low-carbon fuels (ammonia) or CCS to power & decarbonize existing assets.