As part of its assessment of priority basins worldwide, the U.S. Geological Survey estimated the technically recoverable continuous (unconventional) natural gas in the Ordos Basin Province of China, using a geology-based method.
The basin
Large volumes of tight gas and coalbed gas have been found and produced from upper Paleozoic rocks here. But data on the number of wells and their productivity are not public, so the USGS based its inputs on analogous tight-gas and coalbed-gas plays in the United States — one reason the estimates are highly uncertain.
The method uses Monte Carlo simulation over probabilistic estimates of each assessment unit's area, well drainage area, untested share, success ratio, recovery per well and coproduct ratios.
Two assessment units
| Upper Paleozoic Tight Gas | Upper Paleozoic Coalbed Gas | |
|---|---|---|
| Area | 147,409 km², central basin, dipping gently (less than 1 degree) west | 24,410 km², eastern basin |
| Boundaries | fault zones to the west and south; the gas–water transition to the north; the −1,200 meter depth contour to the east | the basin's structural edge to the east; the gas–water transition (the 0.8 percent vitrinite reflectance contour) to the north; the 5-meter net-coal line to the south; the −1,200 meter contour to the west |
| Source | coal beds of the Taiyuan and Shanxi Formations | the same coals, which are also the reservoir |
| Reservoirs | low-permeability sandstones, especially the Shanxi and lower Shihezi Formations — a basin-center gas zone with an updip water leg, with potential in poorer-quality rock | the coals themselves |
Results
| Assessment unit | Gas, mean (F95–F5) | Natural gas liquids, mean (F95–F5) | Wells to develop |
|---|---|---|---|
| Tight gas | 27,964 billion cubic feet (13,172–50,005) | 70 million barrels (25–147) | 44,880 |
| Coalbed gas | 5,622 billion cubic feet (2,302–11,311) | — | 17,258 |
F95 means a 95 percent chance of at least that amount; F5, a 5 percent chance.
Sources
Based on Assessment of Undiscovered Continuous Gas Resources of the Ordos Basin Province, China, 2015, by the Ordos Basin Assessment Team (Ronald R. Charpentier and others), USGS Fact Sheet 2015–3087, U.S. Geological Survey (DOI), citing Charpentier and Cook (2010), IHS Energy (2014) and Xiao and others (2005); a work of the United States government in the public domain. The fact sheet's map is drawn on a licensed Esri base and is left out. Full results: the USGS Energy Resources Program.
Licence: CC0 1.0 (public domain) · Adapted from pubs.usgs.gov
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