Mapeamento de estruturas rasas de gás em sedimentos na plataforma adjacente ao estado do Amapá: Área Canal do Varador

Abstract

Since the 1950s, significant advances have occurred in mapping and interpreting seafloor gas concentrations. Several techniques, such as bathymetry, sonography, and seismic, have been employed in this process. However, high- resolution seismic surveys stand out as crucial tools to accurately identify and characterize these accumulations. In the Foz do Amazonas Basin, pioneering studies provided evidence of gas through geophysical and geological methods, spurring further investigations. The Varador Channel, the area of interest in this report, is located on the inner Amazon shelf, adjacent to Amapá. It is a marine strait that separates the Maracá-Jipióca Ecological Station (EEMJ) from the mainland, in the state of Amapá. During the months of June and July 2016, a campaign was conducted in which high-resolution seismic data were collected in this region, with the aim of characterizing the geomorphology of the Varador Channel. These collected data served as the basis for this work, where a seismic line crossing the Varador Channel was utilized to identify, map, and classify gas occurrences, as well as to determine the possible source of the gas through analysis and interpretation of the seismic data. The processing of the seismic line followed a specific workflow for high-resolution seismic data, involving blaking of the water column, spectral analysis, gain and filtering applications, as well as interpretation of the seismic data. The results revealed the presence of four distinct types of gas accumulations: acoustic blankets, acoustic columns, acoustic curtains, and acoustic turbidity. Additionally, geomorphological features such as the paleochannel and active channel were also identified. Furthermore, it was possible to indicate that bacterial degradation of organic matter in shallow sediments is the most likely origin of gas in the Varador Channel, as the pressure and temperature conditions are not suitable for thermogenic processes or gas hydrate formation. These findings are highly relevant for future studies in the region, particularly regarding gas exploration and production.