Ibp 1693 _ 14 on the oceanography of brazil ’ s equatorial margin : hazardous offshore currents and strategies for mitigation

Brazil’s equatorial margin, extending from Natal to the French Guiana border, is a region characterized by both extraordinary development opportunities and significant operational hazards. Chief among the hazards are intense and highly variable ocean currents capable of delaying, disrupting, or damaging oil and gas exploration and production efforts. Here we review key aspects of the physical oceanography of the equatorial margin based on a collation of historical and contemporary measurements of wind, waves, and currents supplemented with output from a highresolution numerical ocean circulation model. We present new observations of near-surface circulation along the northeastern coast of South America including more than 12 years of satellite-tracked drifter trajectories. These observations reveal strong near-surface flows of greater than 0.75 m/s (1.5 kt) in close proximity to all lease areas within the equatorial margin region. Within this oceanographic context we explore the implications of a high-current environment for seismic survey planning, rig selection and relocation, station keeping, drilling, diving, and spill response. Ultimately, we present recommendations for mitigating the impact of strong and variable oceanic currents on offshore field operations. These include thorough pre-activity preparation (such as site-specific ocean current measurements) and an ongoing program of elevated situational awareness utilizing continuous real-time observations of ocean conditions.