Table 1
Data sources and key for data figures
| Materials | Symbol in figures | Number of samples | Sample depth: km |
|---|---|---|---|
| Brine-saturated African shales |  | 5 | 2.3–2.5 |
| Brine-saturated North Sea shales |  | 3 | 1.6–2.1 |
| Other brine-saturated shales |  | 8 | 1.4–4.3 |
| Brine-saturated shaly coal |  | 1 | 3.6 |
| Gas-saturated shaly coal |  | 1 | 3.6 |
| Brine-saturated sands |  | 8 | 2.4–4.1 |
| Gas-saturated African sands |  | 2 | 2.4–2.5 |
| Gas-saturated tight sands |  | 12 | 3.6–4.1 |
| Gas-saturated carbonatesa |  | 35 | 3.3–4.3 |
| Brine-saturated carbonatesa |  | 25 | 3.5–4.5 |
a
Limestone and dolomite
Source: Wang (2002b)