The Bohaiwan Basin Province and its three assessment units. Base map from the National Park Service; USGS.
The estimate
The U.S. Geological Survey assessed undiscovered, technically recoverable continuous resources — shale oil, shale gas and tight gas — in the Bohaiwan Basin (or Bohai Bay Basin) Province, China's most prolific petroleum province. The means:
- 2,036 million barrels of oil (MMBO) — 2.0 billion barrels — with an F95–F5 range of 423 to 4,774 MMBO;
- 20,320 billion cubic feet of gas (BCFG) — 20.3 trillion cubic feet — range 4,325 to 46,124 BCFG; of this, 16,814 BCFG (83 percent) is potential tight gas;
- 203 million barrels of natural gas liquids (MMBNGL), range 41 to 479 MMBNGL.
F95 means a 95-percent chance of at least that amount; F5, a 5-percent chance.
The basin
The Bohaiwan Basin is a patchwork of grabens, half-grabens, tilted fault blocks and horsts, holding sedimentary rock from Cambrian to Neogene in age. Its complicated tectonic history shaped two major petroleum systems:
- Carboniferous–Permian coals, known sources of gas in the deep subbasins;
- Paleogene lake shales, known sources of oil and gas and the basin's main source rocks.
Three assessment units
| Carboniferous–Permian Tight Gas | Eocene Shahejie Lacustrine Shale Oil | Eocene Shahejie Lacustrine Shale Gas | |
|---|---|---|---|
| Petroleum system | Carboniferous–Permian Coal | Eocene Lacustrine Shale | Eocene Lacustrine Shale |
| Model | gas from coals moved locally into low-permeability rock, mostly deeper than 5,000 meters | some of the oil made in the shales stayed in them after the rest migrated | the same, for gas |
| Main risk | whether gas can be recovered from such tight rock | oil or gas retained, variable rift-lake facies, and how much source rock is mature for gas | the same |
- The coals: up to 25 seams, the thickest 9 meters.
- The shales: members 1, 3 and 4 of the lake-deposited Shahejie Formation, together several hundred meters thick, with Type I and II organic matter and total organic carbon up to 13 weight percent (averaging 3).
- Well drainage areas, success ratios and ultimate recoveries were based on U.S. tight-gas, shale-oil and shale-gas analogs, modeled with vertical wells.
Results by assessment unit
Fully risked means (all units have a probability of 1.0):
| Assessment unit | Oil (MMBO) | Gas (BCFG) | NGL (MMBNGL) |
|---|---|---|---|
| Eocene Shahejie Lacustrine Shale Oil | 2,036 | 1,224 | 12 |
| Eocene Shahejie Lacustrine Shale Gas | — | 2,282 | 23 |
| Carboniferous–Permian Tight Gas | — | 16,814 | 168 |
| Total | 2,036 | 20,320 | 203 |
Sources
Based on Assessment of Undiscovered Continuous Oil and Gas Resources in the Bohaiwan Basin Province, China, 2017, USGS Fact Sheet 2017–3082 (February 2018), by the Bohaiwan Basin Province Assessment Team, U.S. Geological Survey; a work of the United States government in the public domain. The map and results table are taken from the fact sheet's PDF.
Licence: CC0 1.0 (public domain) · Adapted from pubs.usgs.gov
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