Interpretation of several 3D volumes from the Oriente basin suggests that faults define the extent of a given field. Additionally, the subtle stratigraphic boundaries characterised by the clay-filled zones of low porosity compartmentalise oil pools within a field. Identification of these zones is critical. In our experience, neural network based waveform classification has proven to be a successful tool to identify these zones. Qualitative analysis of seismic facies derived from the classification is a common practice. However, we demonstrate in this paper that the quantitative interpretation of seismic facies is possible provided a geological understanding of the seismic signatures is achieved. This paper discusses the extensive 1D-modeling carried out to comprehend the trace shape variations due to changing isopach of the sand/shale sequences, which was fundamental in assigning a realistic geological model to each facies. Also described in the paper is the workflow and a key methodology developed to derive "Net thickness" of reservoir sands from the seismic facies. Rigorous study of this technique on several 3D data sets from Ecuador's Oriente Basin has produced results, which have established the foundation for understanding the depositional environments and the reservoir models, validated by subsequent drilling.