A U.S. Geological Survey assessment from 2017, published as Fact Sheet 2017–3086 in February 2018.
Using a method built on the geology of the rocks, the U.S. Geological Survey (USGS) estimates that the Hanoi Trough of Vietnam holds a mean of 52 million barrels of undiscovered, technically recoverable continuous oil and 591 billion cubic feet of continuous gas.
Figure 1. The three continuous assessment units in the Hanoi Trough. Base map from the National Park Service. USGS.
A trough shaped by the Red River fault
The Hanoi Trough is the onshore part of the Song Hong Basin. Its structure is tied to the Red River fault zone, which runs from Tibet eastward for more than 1,000 kilometres to the Hanoi Trough and on into the Gulf of Tonkin.
| Period | What the Red River fault did |
|---|---|
| Late Eocene to early Miocene | slipped sideways (left-lateral) while pulling apart, splitting into several strands that formed the horsts and grabens of the trough |
| Middle Miocene | as seafloor spreading in the South China Sea stopped, switched to squeezing, with minor inversion and uplift in the trough |
| Since the end of the Miocene | a right-lateral (dextral) fault with little or no movement |
In the grabens, sediments are up to 6 kilometres thick. The earliest fill, from the latest Eocene to early Oligocene, is river and lake-edge conglomerate and sandstone, plus deep-water, organic-rich lake shale. From the late Oligocene into the Miocene the grabens filled with river, delta and estuary sediments with layers of coal and lignite. The main petroleum source rocks are the late Eocene–early Oligocene lake shales and the Neogene coals and lignites.
Two petroleum systems, three assessment units
The Hanoi Trough Oligocene Lacustrine Total Petroleum System, based on mapping by Hiep (2015), holds two units: a shale oil unit and a shale gas unit.
- Organic-rich lake shales in the rift basins of northern Vietnam are up to 500 metres thick.
- Their organic matter is mostly Type I, with some Type III, and total organic carbon reaches 8 weight percent.
- The source rocks are thought to be mostly in the oil window, with a small area in the gas window.
- The model: oil and gas formed in these Oligocene shales, and some stayed in the shales after the rest migrated.
The Hanoi Trough Neogene Coalbed Gas Total Petroleum System holds one unit, defined for biogenic gas that may have formed and stayed in the shallow, thermally immature coals and lignites.
Inputs for well drainage areas, success ratios and estimated ultimate recoveries came from similar shale-oil, shale-gas and coalbed-gas units in the United States.
| Key input (minimum / mode / maximum / mean) | Shale oil | Shale gas | Coalbed gas |
|---|---|---|---|
| Potential production area (acres) | 800 / 155,000 / 310,000 / 155,267 | 800 / 17,174 / 34,348 / 17,441 | 800 / 426,500 / 853,000 / 426,767 |
| Average drainage area of wells (acres) | 40 / 120 / 200 / 120 | 80 / 120 / 160 / 120 | 40 / 80 / 120 / 80 |
| Success ratio (percent) | 10 / 50 / 90 / 50 | 10 / 50 / 90 / 50 | 40 / 60 / 80 / 60 |
| Average estimated ultimate recovery per well | 0.04 / 0.08 / 0.2 / 0.086 million barrels | 0.1 / 0.25 / 0.7 / 0.273 billion cubic feet | 0.08 / 0.2 / 0.4 / 0.215 billion cubic feet |
| Assessment unit probability | 0.9 | 0.9 | 1.0 |
Results
The estimated mean for continuous oil is 52 million barrels, with an F95–F5 range from 0 to 127 million barrels. For continuous gas, the mean is 591 billion cubic feet, ranging from 147 to 1,210 billion cubic feet.
| Assessment unit | Oil, million barrels (F95 / F50 / F5 / mean) | Gas, billion cubic feet | Natural gas liquids, million barrels |
|---|---|---|---|
| Shale oil | 0 / 46 / 127 / 52 | 0 / 36 / 106 / 42 | 0 / 0 / 1 / 0 |
| Shale gas | — | 0 / 16 / 43 / 18 | 0 / 0 / 1 / 0 |
| Coalbed gas | — | 147 / 488 / 1,061 / 531 | 0 / 0 / 0 / 0 |
| Total | 0 / 46 / 127 / 52 | 147 / 540 / 1,210 / 591 | 0 / 0 / 2 / 0 |
F95 means a 95 percent chance of at least the amount shown, and the other columns are read the same way. The results are fully risked; for gas accumulations, all liquids are counted as natural gas liquids.
Sources
- Schenk, C.J., Tennyson, M.E., Mercier, T.J., Woodall, C.A., Le, P.A., Klett, T.R., Finn, T.M., Leathers-Miller, H.M., Gaswirth, S.B., and Marra, K.R., Assessment of Undiscovered Continuous Oil and Gas Resources in the Hanoi Trough, Vietnam, 2017, U.S. Geological Survey Fact Sheet 2017–3086, February 2018. https://doi.org/10.3133/fs20173086 — the map and both tables recovered from the PDF, which the imported page had lost.
- The fact sheet draws on Hiep (2015), Lei and others (2015), Nielsen and others (1999, 2007), Petersen and others (2001), Rangin and others (1995) and Wysocka and Świerczewska (2005).
- Rewritten in hubnx's own words.
Licence: CC0 1.0 (public domain) · Adapted from pubs.usgs.gov
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