The technological evolution of several productive sectors of society has demanded the same level of evolution for the oil and gas industry, both for energy production and their own systems' functioning. The production of crude oil and natural gas in offshore units is one of the answers to this demand. However, these offshore units have critical onboard activities and risks, notably FPSO units; it is necessary to have adequate recognition of the elements that can support these activities and manage these risks, enabling productive and safe operations. In this sense, this article aims to increase the understanding of the complex interactions and inherent safety issues that arise in the operations of FPSOs, observing and analysing the work done onboard such platforms. The FRAM methodology has been chosen because it allows for the recognition and analysis of the complex interactions involving workers, equipment, system and offshore environment, focusing on the oil treatment area of the process plant. The results demonstrated some interesting findings regarding onboard safety and the relationship between human competences, work demands and process safety.