Terrigenous Mirador formation of Alturitas field, Venezuela: application of acoustic inversion

The Alturitas field is a large South-North trending closure. Wells were drilled between 1948 and 2009. Paleogene Mirador formation was the main target of the work. The formation has a tripartite structure; it is represented by coarse-grained light-coloured sandstone in the cycle base and fine- and medium-grained sandstone in the middle and upper part of the section, with ubiquitous coals. Sediments accumulated in the continental fluvial environment with the provenance area to the west of it. The main oil accumulations discovered occur in the Marcelina formation underlying the Mirador formation. Deterministic Acoustic Inversion applied to legacy seismic data allowed obtaining additional geological information. The choice of the Acoustic Inversion is conditioned by the available data set, namely: stacked 3D CDP cube and caliper, acoustic and density, and gamma-ray logging diagrams in the wells. Deterministic Acoustic Inversion is for the first time carried out for the Mirador formation. The authors used all the available geological and geophysical data to interpret the results obtained. Methodology of Acoustic Inversion calculation and lithology cube building is shown by the example of the Mirador formation. Deterministic Acoustic Inversion allowed calculating the predicted net thickness over the study area and confirming the conceptual model of the Mirador formation