Post Combustion Co2 Capture for Petrobras Offshore Gas Turbine Generators

As one of the twelve member-companies of the Oil & Gas Climate Initiative (OGCI), Petrobras aims for net zero emissions (scopes 1 and 2) among the six Climate Goals presented in the Strategic Plan 2023-2027 (PE23-27), the reduction of the Greenhouse Gas Index in the Exploration & Production segment (acronym IGEE-E&P in Portuguese used by Petrobras) to 15 kgCO2/boe by 2025 maintaining this value until 2030 (PETROBRAS, 2023). This will contribute to the target of total absolute operational reduction of 30% greenhouse gas emissions by 2030, compared to 2015. To put these values into perspective this has motivated the company to double its reinjection target to 80 million tonCO2 by 2025 in CCUS projects. Representing between 60 to 80%, the main source of greenhouse gas (GHG) emissions in an offshore Floating production storage and offloading (FPSO) installation, the combustion of fuel gas in the gas turbine generator (GTG) for main power generation, to drive all the electrical equipment involved in the topside processing. Therefore, in pursuit of its E&P operations GHG emissions reduction goals, Petrobras has carried out strategies focused on its power generation with the implementation of all-electric driven FPSO’s and studies of combined heat and power (CHP) generation units. However, these actions are limited to targeting from 15 to 25% of GHG emissions related to power generation and a more challenging approach is necessary to achieve higher emissions reductions. Consequently, Petrobras is carrying studies with the aim to evaluate the technical and economic feasibility of including in its greenfield projects offshore post combustion CO2 capture (PCCC) units, whereas state-of-the-art developments shows a potential to capture more than 90% of the CO2 from GTGs exhaust gas. Several different approaches can be given to seek PCCC such as: solvent based absorption, temperature swing adsorption (TSA) or pressure swing adsorption (PSA) using solid adsorbents like zeolite, activated carbon among others, membrane separation, hydrate separation and cryogenic distillation. The International Energy Agency on its report related to the different approaches for CCUS pointed out that the most advanced technology readiness level (TRL) option for power generation exhaust gas is using solvent based absorptions that have been classified as on demonstration level with a few demonstration plants operating or under construction to validate the specific solvent developed. It should be noted that natural gas sweetening (CO2 and H2S removal) using solvent-based technology is a dominated field in the industry, including offshore applications in Petrobras assets. However, the exhaust gas stream from the GTG has low pressure (close to atmospheric), low CO2 content (close to 4%v/v) close to high temperature and presence of other contaminants such as O2, N2 and NOx and this presents additional challenges to be addressed. Although, it is not considered as a technological barrier, the PCCC unit will add complexity to the offshore installation when compared to the traditional solvent based natural gas sweetening facility deployed. Seeking acceleration for early adoption of the most advanced technology available, Petrobras has begun an assessment of available technologies within the offshore field expertise that could offer a solvent based solution capable of evolving TRL for offshore applications. Notwithstanding that direct onshore PCCC units still has a limited TRL with a restricted number of projects in operation, the case of offshore applications implies in additional challenges such as footprint and weight limitations along with offshore motion assessments. The ongoing screening process has the intention to, with strong collaborations with technology providers, develop a Front-End Engineering Design (FEED) to present the necessary level of engineering detail with the footprint restrictions of a FPSO project along with technical and economic feasibility assessments for an offshore solvent absorption based PCCC installation.