Impacts on seafloor geology of drilling disturbance in shallow waters
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This paper describes the effects of drilling disturbance on the seafloor of the upper continental slope of the Campos Basin, Brazil, as a result of the project Environmental Monitoring of Offshore Drilling for Petroleum Exploration – MAPEM. Field sampling was carried out surrounding wells, operated by the company PETROBRAS, to compare sediment properties of the seafloor, including grain-size distribution, total organic carbon, and clay mineral composition, prior to drilling with samples obtained 3 and 22 months after drilling. The sampling grid used had 74 stations, 68 of which were located along 7 radials from the well up to a distance of 500 m. The other 6 stations were used as reference, and were located 2,500 m from the well. The results show no significant sedimentological variation in the area affected by drilling activity. The observed sedimentological changes include a fining of grain size, increase in total organic carbon, an increase in gibbsite, illite, and smectite, and a decrease in kaolinite after drilling took place.
KeywordsGeological data collections Offshore exploration Environmental monitoring Campos Basin Brazil
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