Periplatform Ooze Within the Vaca Muerta Formation, Neuquén Basin, Argentina

Abstract

The distribution of carbonate-rich facies and their interplay with organic matter are essential when determining the prospective character of potential targets. This work provides a better understanding of the stratigraphic distribution and facies variability of carbonate-rich intervals within the Vaca Muerta Formation in the Neuquén Basin, Argentina. Specifically, the aim is to predict the occurrence of carbonate rich intervals, their areal extent and relationship to TOC-rich facies, and to assess their potential as unconventional reservoirs.

The data set is from two outcrop areas: in the Sierra de la Vaca Muerta that is in a relatively proximal position, and Puerta Curaco, which is in a more distal setting. We characterized four carbonate-rich intervals of different ages in detail with respect to lithofacies and both carbonate and TOC content, and placed them into a sequence and bio-stratigraphic framework. The results help explain the origin of the observed facial heterogeneities and the time-space distribution of the studied intervals.

The carbonate-rich intervals were predominantly sourced from carbonate-rich shelves and the basinward thinning and decrease in frequency of carbonate beds gives evidence of a periplatform origin of the studied intervals. The distribution of these intervals is predictable within the sequence-stratigraphic framework as carbonate-rich facies correspond to the regressive portions of cycles, cycle sets and sequences. The accompanying increase in skeletal content towards the top of cycles indicates an enhancement of the platform shedding process during sea level highstands. Sequence-stratigraphic control was observed for TOC content that shows the highest values in transgressive and maximum flooding portions of cycles. The presence of carbonate-rich intervals of different ages points towards production and export of shelf carbonates at different times and from different locations within the basin, accompanying the prograding character of the Vaca Muerta Formation. The analyzed lateral and vertical facies transitions within the studied intervals show that the facies with the highest potential for unconventional reservoirs can be found towards deeper basinal settings where carbonate-rich beds and intervals become thinner and more intercalated with organic-rich facies.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018