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U.S. Geological Survey, National and Global Petroleum Assessment. Fact Sheet 2017–3021, April 2017.
The result: mean undiscovered, technically recoverable resources of 764 million barrels of oil and 3.5 trillion cubic feet of gas in tight reservoirs of the Permian Lucaogou Formation, Junggar basin, northwestern China.
Figure 1: the two assessment units in the Junggar basin. Base from the National Park Service. USGS.
The rock
- What: laminated, organic-rich lake-bed shale of the Lower Permian Lucaogou Formation (Yang and others, 2010; earlier work called it Upper Permian).
- Setting: laid down in a foreland basin north of a thrust belt in the Tian Shan; the Junggar was a sag basin in the Mesozoic and Paleogene and has been a foreland basin again since the Neogene.
- Target: oil and gas held in tight reservoirs between the shale layers. Tight reservoirs are non-shale rocks so impermeable — generally around 0.1 millidarcies or less, as the Lucaogou is — that they need hydraulic fracturing to produce.
- Today: tight-oil work is focused on the relatively shallow Jimusar sag, where 16 wells produce "industrial tight-oil flows."
Two assessment units
| Unit | Where | History |
|---|---|---|
| Lucaogou Continuous Oil | shelves around the basin's edges, shallower than 5 km — for example the Jimusar sag | slow burial generated oil in the Late Jurassic to middle Cretaceous |
| Lucaogou Continuous Gas | organic-rich shale deeper than 5 km | almost continuous lake and river sedimentation from the Permian to the Neogene; oil formed in the latest Permian–earliest Triassic and was later cracked to gas in the Mesozoic |
U.S. continuous oil and gas fields were used as analogs.
Key inputs
Table 1. Minimum / mode / maximum (mean). The whole of each unit is untested (100%); each has a probability of 1.0.
| Input | Oil unit | Gas unit |
|---|---|---|
| Potential production area (acres) | 1,000 / 1,300,000 / 2,671,000 (1,324,000) | 1,000 / 3,000,000 / 6,300,000 (3,100,333) |
| Drainage per well (acres) | 40 / 80 / 120 (80) | 80 / 120 / 160 (120) |
| Success ratio (%) | 10 / 50 / 90 (50) | 10 / 50 / 90 (50) |
| Average EUR per well | 0.04 / 0.085 / 0.2 (0.091) million barrels | 0.08 / 0.2 / 1.2 (0.256) billion cubic feet |
Results
Table 2: fully risked. F95 means a 95-percent chance of at least that amount; F5, a 5-percent chance. These are technically recoverable, not necessarily economic, resources.
| Unit | Oil, million barrels: F95 / F50 / F5 (mean) | Gas, billion cubic feet: F95 / F50 / F5 (mean) | NGL, million barrels (mean) |
|---|---|---|---|
| Oil unit | 171 / 675 / 1,675 (764) | 45 / 192 / 542 (230) | 1 |
| Gas unit | — | 588 / 2,448 / 8,581 (3,235) | 65 |
| Total | 171 / 675 / 1,675 (764) | 633 / 2,640 / 9,123 (3,465) | 66 (range 11–178) |
Sources
Based on Assessment of Permian Tight Oil and Gas Resources in the Junggar Basin of China, 2016, USGS Fact Sheet 2017–3021, by the Junggar Basin Assessment Team: Christopher J. Potter, Christopher J. Schenk, Marilyn E. Tennyson, Timothy R. Klett, Stephanie B. Gaswirth, Heidi M. Leathers-Miller, Thomas M. Finn, Michael E. Brownfield, Janet K. Pitman, Tracey J. Mercier, Phuong A. Le and Ronald M. Drake II, 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, which the import had left out.
Licens: CC0 1.0 (offentligt eje) · Bearbejdet efter pubs.usgs.gov
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