Sequence Stacking and Reservoir Facies of a Vaca Muerta Shale Outcrop, Puerta Curaco, Neuquen Basin, Argentina
Kernan, Henry1 and Sonnenberg, Steve
The Neuquen Basin is located in the provinces of Neuquen, Rio Negro, and Mendoza in western Argentina. It forms an elongated crescent-shaped basin against the Andes Mountains, with a depocenter towards the western part of the basin and a shallowing ramp towards the east. The Vaca Muerta Formation is part of the transgressive and high stand systems tracks of the Late Jurassic-Early Cretaceous (Kimmeridgian to Berriasian) Lower Mendoza Group in the basin. It overlies the Tordillo sandstone, ranging from an uncomfortable contact at the edges of the basin to a transitional contact at the center. The Quintuco Formation overlies the Vaca Muerta Formation, mostly as a transitional contact into shallow marine carbonates and sandstones. Together the Vaca Muerta and Quintuco Formations form downlapping clinoforms which are uncomfortably overlain by the low stand systems track Mulichinco Formation fluvial sandstones. As a proven source rock, the Vaca Muerta Formation has become an important new target for shale gas and tight oil exploration and development in the Neuquen Basin.
The Vaca Muerta Formation consists of alternating shale, marl, chalk, and limestone beds, with excellent oil prone generating intervals that have been recognized as the main source rock of the basin. The immense thickness of the formation (100 to 1,000 meters), its favorable mineralogy, and high kerogen content indicate it has potential for being a self-sourcing reservoir comparable to current unconventional plays in the United States.
An outcrop 605 meters (1,985 feet) thick was described in the Puerta Curaco area near Chos Malal, Neuquen Province. The area is towards the basin center, where the contact between the Tordillo, Vaca Muerta, and Quintuco formations is transitional, and in the oil to wet gas maturity window (1.3-2.0 Ro). Different facies associations where identified based on lithological stacking.
Samples from key intervals were studied for mineralogy and source potential. The general sequence stacking shows different cycles inside the Vaca Muerta section marked by the presence/absence of carbonate beds, the amount of marl relative to shales, a change in thickness between carbonate beds, and a change in color from black shales and marls to grey shale and siltstone.
The outcrop at Puerta Curaco was tied to subsurface well log, core, and seismic data from PlusPetrol’s Cinco Saltos and Loma Jarillosa Este blocks to the southeast.
AAPG Search and Discovery Article #90166©2013 AAPG International Conference & Exhibition, Cartagena, Colombia, 8-11 September 2013