Twenty years of geophysical operations on the brazilian continental shelf

Abstract

Systematic seismic surveys of the Brazilian continental shelf conducted continuously since 1968 have provided the Petrobras Exploration Department with data on 677,403 km of fines (184,445 km involving 3D techniques). Petrobras has availed itself of the most modem energy sources, cables, and seismographs. At present, the seismic surveys relies on air guns and on two streamers, each equipped with 240 digital transmission channels. Original/y limited to water depths of 50 m, seismic fines now cover wide areas of deep waters, sometimes surpassing 3,000 m. Together with seismic surveys, over these past 21 years the Exploration Department has received the results of 211,000 km of gravimetric surveys, 266,000 km of aeromagnetometric profiles, and 190,000 km of records taken by on-board magnetometers. Under an agreement between Petrobras and the Brazilian Navy, in 1986 the Exploration Department assumed the geophysical work of the oceanographic vessel "Almirante Câmara", with the aid of Navy officers. Geophysical surveys were conducted on the outer edge of the Brazilian and Antarctic continental shelves. Since 1977, under risk contracts with Petrobras, companies have surveyed 134,455 km of seismicline, 50,000 km of gravimetric, and 44,100 km of profile surveys, the latter employing magnetometers.