Integrated Sedimentology and Sequence Stratigraphy Using Well Cuttings in the Upper Jurassic–Lower Cretaceous Quintuco-Vaca Muerta System, Neuquen Basin, Argentina

Abstract

Cuttings thin sections have been analyzed semi-quantitatively from 20 wells through the Vaca Muerta Quintuco System across the southern half the of the Neuquen Basin. The study interval ranges from a few hundred up to 1000 meters thick. The system grades from nonmarine siliciclastics to the south and east to coastal evaporites, then to shallow marine carbonates and siliciclastics of the Quintuco Formation deposited on top of the platform. Platform margin carbonate buildups mainly consisting of bivalve floatstone grade into upper slope siltstones and carbonates with common sponge spicules which grade downslope into calcisiltites with sponge spicules, radiolarians, epistomina forams and moderately organic-rich mudstones. At the toe of the slope, carbonates are commonly dolomitized. The basinal facies of the Vaca Muerta Formation consist of silty organic-rich mudrock with common concretions and varying quantities of radiolarian and coccolith pellets, organic-poor wackestone and mudstone and both calcitized and clay-rich ash bed deposits.

Conventional reservoirs occur in the shallow marine carbonates and siliciclastics of the Quintuco and unconventional oil and gas reservoirs are being developed in the vast organic-rich basinal facies of the Vaca Muerta. Sequence boundaries can be picked in the shallow marine facies using evaporites and fitted fabric grainstones that formed in the vadose zone. Sequence boundaries are correlated across facies tracts from coastline to the basinal facies. Reservoir facies are partitioned and occur in predictable stratigraphic positions within sequences. Cuttings studies provide a great deal of sedimentological, stratigraphic and diagenetic information at a fraction of the cost of core.

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