Cahuil gas field was discovered in 2016 at Magallanes basin, proving commercial gas in Upper Paleocene-Mid Eocene sandstones interbedded with the Bahía-Inútil-Group shales. Sandy intervals, referred as CABI (Complejo Arenoso del Grupo Bahía Inútil or Bahía-Inútil Group’s Sandy Complex), represent submarine-fan distal deposition of multiple turbiditic channels at the continental slope’s mid-section. The reservoir’s stratigraphy allows us to identify several sandchannel cycles distributed as fan-shaped deposits originated in an incision of the shelf break aiming to the southwest. The present structure near Cahuil gas field was shaped by the last tectonic event, consisting mainly of Oligocene-to-present transcurrent deformation. At channels depth, due to seismic vertical resolution, there is more uncertainty in evaluating the reservoir distribution and continuity, making difficult to distinguish between structural features, like inside-reservoir faults, and a more complex stratigraphic configuration like lateral-interlocking of channels. Hence, CABI seismic response was modelled through one- and two-dimensional normal-incidence synthetic seismographs. One-dimensional modelling has allowed to establish a relationship between reservoir stratigraphy and the seismic amplitude attenuation observed on some wells of Cahuil gas field: seismic amplitudes dim proportionally to sand-shale interbedding for constant gross thickness. On the other hand, two-dimensional modelling, confirmed the one-dimensional modelling results and led to propose a new idea for the reservoir’s lateral configuration. The original hypothesis was that the observed reflector discontinuities were caused by faults. Now it is believed that the seismic response may be related to avulsion of turbiditic channels.