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By the USGS Brazil Basin Provinces Assessment Team: Christopher J. Schenk, Marilyn E. Tennyson, Timothy R. Klett, Thomas M. Finn, Tracey J. Mercier, Sarah J. Hawkins, Stephanie B. Gaswirth, Kristen R. Marra, Michael E. Brownfield, Phuong A. Le and Heidi M. Leathers-Miller. USGS Fact Sheet 2017–3009, March 2017.
Using a geology-based method, the U.S. Geological Survey estimated a mean of 5 billion barrels of oil and 47 trillion cubic feet of gas — undiscovered, technically recoverable, continuous (shale) resources — in the Paleozoic Solimões, Amazonas and Parnaíba basin provinces of Brazil.
The three basin provinces and five assessment units. Base: National Park Service. Map: USGS.
Three basins, one story
The basins share the geology that matters for oil and gas:
- History: rifting, then thermal sag, wrench faulting and compression.
- Source rock: Devonian organic-rich shales, laid down in the sag phase, with mostly Type II marine kerogen, more than 2 (up to 8) weight percent organic carbon, and more than 15 meters thick.
- Heat: burial plus intrusions matured the shales.
- Risk: whether the oil and gas stayed in the shales.
For each basin the USGS defined a Devonian total petroleum system and one or two assessment units (AUs):
| Basin | Petroleum system | Assessment units |
|---|---|---|
| Solimões | Jandiatuba | Continuous Gas |
| Amazonas | Barreirinha | Continuous Oil; Continuous Gas |
| Parnaíba | Pimenteiras | Continuous Oil; Continuous Gas |
The geologic model
Oil and gas formed as the source rocks were buried, starting in the Permian, and as dolerite dikes and sills intruded from the Late Triassic to the Early Cretaceous. Some of it stayed in the matrix of the Devonian shales. Shale oil was modeled with vertical wells; drainage areas, recoveries and success rates come from U.S. shale-oil and shale-gas analogs.
Key inputs: success ratios of 10, 50 and 90 percent (minimum, mode, maximum; mean 50) in every AU; average recovery per gas well 0.256 billion cubic feet and per oil well 0.034 million barrels (means); and AU probabilities of 0.6 (Solimões gas, both Parnaíba units) and 0.8 (both Amazonas units).
The results
Fully risked estimates. F95 means a 95 percent chance of at least that amount; F5, a 5 percent chance.
| Assessment unit | Prob. | Oil, mean (MMBO) | Gas, mean (BCFG) | Gas F5 (BCFG) | NGL, mean (MMBNGL) |
|---|---|---|---|---|---|
| Solimões Jandiatuba Gas | 0.6 | — | 4,320 | 16,186 | 129 |
| Amazonas Barreirinha Oil | 0.8 | 3,437 | 27,522 | 82,378 | 385 |
| Amazonas Barreirinha Gas | 0.8 | — | 6,294 | 20,040 | 189 |
| Parnaíba Pimenteiras Oil | 0.6 | 1,582 | 6,323 | 22,568 | 139 |
| Parnaíba Pimenteiras Gas | 0.6 | — | 2,742 | 10,370 | 55 |
| Total | 5,019 | 47,201 | 151,542 | 897 |
MMBO: million barrels of oil. BCFG: billion cubic feet of gas. MMBNGL: million barrels of natural gas liquids.
- Oil: a mean of 5,019 million barrels (about 5 billion), ranging 0 to 15,584.
- Gas: a mean of 47,201 billion cubic feet (about 47 trillion), ranging 0 to 151,542.
- Liquids: a mean of 897 million barrels, ranging 0 to 3,006.
- Why zero at F95: every AU carries geologic risk (probability under 1.0) that not even one well of minimum size exists.
The Amazonas Basin dominates: 68 percent of the oil (3,437 MMBO) and 72 percent of the gas (33,816 BCFG). The main risk everywhere is whether oil and gas survived the deformation and intrusions.
More assessments: the USGS Energy Resources Program.
Sources
Based on Assessment of Continuous Oil and Gas Resources of Solimões, Amazonas, and Parnaíba Basin Provinces, Brazil, 2016, USGS Fact Sheet 2017–3009, U.S. Geological Survey; a work of the United States government in the public domain. The map and both tables are taken from the fact sheet's PDF; the import had lost them.
Licence : CC0 1.0 (domaine public) · Adapté de pubs.usgs.gov
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