GEO ExPro

Argentina: Unconventional Discoveries

Spanish international oil company Repsol has made its biggest ever oil discovery after drilling 15 wells in the Neuquén province of western Argentina.
This article appeared in Vol. 8, No. 6 - 2012

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Outcrop of the mature source rock in the Vaca Muerta Formation with parallel ‘beef’ bedding (light color veins) – fibrous calcite veins, the result of overpressure and horizontal compression, that grow parallel to the bedding of the shales. Source: NEOS Source: YPF The discovery was made by the Argentinian branch of the company, YPF, and is reported to total 927 MMboe (recoverable) of predominantly non-conventional shale oil, potentially making Argentina one of the world’s leading producers of this commodity. Recoverable resources of 741 MMb of 40 – 45° API shale oil are thought to be reservoired in 428 km2 of the Vaca Muerta Formation. YPF have already drilled 15 wells in the area, known as Loma La Lata Norte, and have reported that the wells have been flowing high quality shale oil at an initial rate of 5,000 boepd.  

The Vaca Muerta Formation is one of the world’s largest non-conventional reservoirs. It is a Late Jurassic to Early Cretaceous transgressive marine sequence of alternating black shales and limestones, the former being one of the principal source rocks for the Neuquén Basin. It extends to over 30,000 km² and in places is up to 425m thick.  

Exploration is also in progress at another discovery in a 502 km2 area of the same formation, where the well is flowing 400 boepd of 35° API shale oil. There is potential for even larger reserve estimates, as Repsol YPF has rights to 12,000 km2 in the Vaca Muerta Basin, which, according to Wood Mackenzie, means that it is the world’s second largest company in terms of non-conventional acreage. This discovery doubles its proven reserves in Argentina and increases by a third the amount of recoverable oil claimed worldwide by the company.  

As reported in GEO ExPro earlier this year (Vol. 8, No. 1), YPF found 4.5 Tcf of unconventional gas in the same area in December 2010, a discovery which was considered a major breakthrough for Argentina at the time, as the country’s gas reserves had fallen 51% to 13.3 Tcf, and domestic consumption had begun to overtake production. According to recent analysis by EIA and Advanced Resources International, Argentina has 774 Tcf of technically recoverable shale gas resources – the world’s third largest assessed endowment, behind only China and the United States – and the Neuquén Basin contains more than half of the country’s technically recoverable shale gas resources.

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