Integrated electrical tomography and remote sensing survey for location of shallow subsurface gas

The main goal of this paper is to summarize the results of the geological and geophysical surveys performed at the future location of the Caraguatatuba Gas Treatment Unit (UTG-CA) for the evaluation of shallow subsurface gas. The unit will be responsible for receiving, separating and distributing the gas produced at the Mexilhão field, located approximately 130 km SE of the São Sebastião island, at the Santos Basin. Shallow gas was identified during the initial stages of the project when preliminary geotechnical drilling was conducted. From a total of 159 cores, 17 showed the presence of gas. These cores are preferentially located in the west side of the area, but showed no homogeneous distribution. In order to delineate the limits of the gas body integrated geo-electric and remote sensing surveys were conducted. The results showed that the gas has its occurrence limited to the west side of the area, is trapped by a relatively thick marine clay layer and does not escape to the surface.