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Utilizing a basin-wide data set of three-dimensional seismic volumes and the application of principles of seismic stratigraphy and seismic geomorphology allowed identifying numerous depositional elements within the Vaca Muerta–Quintuco system, a set of clinoforms whose topsets belong to the Quintuco Formation, whereas the bottomsets and foresets belong to the Vaca Muerta Formation. Within the topsets, small circular geobodies clustered near the prograding shelf margin, averaging 200–800 m (656–2625 ft) in diameter and up to 75 m (246 ft) in height. These features comprise small carbonate buildups defining carbonate factories trending strike parallel. Identification of intervals where these geobodies are abundant is important because wells drilled through them have experienced either drilling mud admission or gas influx. In addition to these biogenic carbonate mounds, the topsets show elongated oolitic grainstone shoals oriented orthogonal to coeval shelf margins, in some cases measuring up to 22 km (14 mi) long and 5 km (3 mi) wide.

The foresets (slope deposits) become progressively enriched in total organic carbon (TOC) and porosity downdip—key variables for a self-sourced unconventional reservoir. These deposits commonly comprise mudstone and marlstone, interbedded with limestones. In the lower foresets to toesets, strike-parallel, high–seismic-amplitude, and high-energy calcareous deposits are embedded in organic-rich mudstones. In some instances, these amplitude anomalies, drilled and cored by a few wells, show both well-defined linear geobodies along the toeset and evidence of bottom currents in cores (thicker limestone beds, ripples, bioturbation, and occasional centimeter-scale soft-sediment deformation). Identification of such geobodies is critical, as there is evidence from ongoing development drilling that these may act as hydraulic-fracture barriers and can also affect well performance as evidenced by increased water production.

The bottomsets consist of low–amplitude-parallel, “railroad track” reflections that extend for tens of kilometers, characterizing the classic basin center Vaca Muerta play. Within these deposits, no major mappable geobodies are observed other than localized compressional ridges of mass-transport deposits (MTD) near the toesets. In some areas of the basin, the Vaca Muerta Formation was deposited directly on top of a preexisting non-marine paleo-aeolian dune topography which had a direct impact on the stratal geometries and the bottomset facies of the Vaca Muerta Formation.

Acoustic impedance (AI) from seismic inversion show well-defined Vaca Muerta low-impedance seismic facies, which relate to the presence of predominantly fine-grained, organic-rich (~5%), porous (~11%) mudstones and marlstones. Within the high-TOC Vaca Muerta interval, most AI three-dimensional (3-D) volumes throughout the basin show an average of five to six seismic facies with discrete AI values that can be directly correlated to rock types, depending on their position within the clinoform (i.e., topset, foreset, bottomset). These seismic facies correlate to facies associations with distinct petrophysical and geomechanical properties at core/outcrop scale, as measured by lab studies. Understanding this relationship and its distribution in space is critical to predicting optimum horizontal well landing zones and sweet spots.

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