Undiscovered Shale Oil and Gas in Argentina's Neuquén Basin: the 2016 USGS Assessment

A U.S. Geological Survey assessment from 2016, published as Fact Sheet 2017–3025 by Christopher J. Schenk, Timothy R. Klett, Marilyn E. Tennyson, Tracey J. Mercier, Janet K. Pitman, Stephanie B. Gaswirth, Thomas M. Finn, Michael E. Brownfield, Phuong A. Le, Heidi M. Leathers-Miller and Kristen R. Marra.

Using a method built on the geology of the rocks, the U.S. Geological Survey (USGS) estimates that the Neuquén Basin Province of Argentina holds a mean of 14.4 billion barrels of undiscovered, technically recoverable continuous (unconventional) oil and 38 trillion cubic feet of gas.

What was assessed

As the USGS defines it, the province includes the basin, or "embayment", a platform in the east and a fold belt in the west. The study estimated the oil and gas that may remain in three source rocks found in both the basin and the fold belt:

• the Jurassic Los Molles Formation;
• the Jurassic–Early Cretaceous Vaca Muerta Formation;
• the Early Cretaceous Agrio Formation.

Each became a total petroleum system, following published definitions, and twelve continuous assessment units were defined within them.

The geologic model

Three assumptions underlie the assessment:

1. Some of the oil and gas each source rock generated stayed inside it and could be recovered.
2. Repeated phases of structural deformation in the fold belt reduced the oil and gas retained there, compared with the basin.
3. The assessment relied mainly, though not entirely, on vertical wells, which shapes the inputs for well drainage area, estimated ultimate recovery and success ratio.

So the assessment units were drawn according to whether the source rock lies in the fold belt or the embayment, how thermally mature it is, its total organic carbon, and how thick the viable source rock is. The USGS counts a viable continuous accumulation only where the effective source rock is at least 15 metres thick, total organic carbon at least 2 weight percent, and the hydrogen index at least 200 milligrams of hydrocarbon per gram of total organic carbon.

Well drainage areas, estimated ultimate recoveries and success ratios came from U.S. analogues for continuous oil and gas reservoirs.

The five assessment units of the Los Molles Total Petroleum System. Base map from the National Park Service. USGS.

The five assessment units of the Vaca Muerta Total Petroleum System. USGS.

The two assessment units of the Agrio Total Petroleum System. USGS.

Results

The estimated means for the province are:

• oil: 14,370 million barrels, with an F95–F5 range from 4,139 to 27,913 million barrels;
• gas: 37,966 billion cubic feet, from 10,382 to 76,102 billion cubic feet;
• natural gas liquids: 482 million barrels, from 113 to 1,055 million barrels.

Most of the oil — 12,848 million barrels, or 89 percent — is in the three oil units of the Vaca Muerta. Half the gas (19,155 billion cubic feet, 50 percent) is in the Vaca Muerta and 48 percent (18,137 billion cubic feet) in the Los Molles.

By assessment unit, the mean estimates are:

F95 means a 95 percent chance of at least the amount shown, and F5 a 5 percent chance. The results are fully risked; for gas accumulations, all liquids are counted as natural gas liquids.

Sources

• Christopher J. Schenk and others, Assessment of Continuous Oil and Gas Resources in the Neuquén Basin Province, Argentina, 2016, U.S. Geological Survey Fact Sheet 2017–3025. https://doi.org/10.3133/fs20173025 — almost all of it recovered from the PDF, since the imported page had kept only its summary: the introduction, geologic model, maps and tables.
• The fact sheet draws on Barredo and Stinco (2014), Legarreta and others (2005), Legarreta and Villar (2015), Licitra and others (2015), Martínez and others (2008), Rimedio and others (2015), Schmidt and others (2013), Tyson and others (2005) and Urien and Zambrano (1994).
• Rewritten in hubnx's own words.