Table 1. Physicochemical characters of the injection water and two production waters of the Gudao petroleum reservoir.
| Parameters | Injection water samples | Production water samples | |
| W (G1–6) | L (6–13) | C (3C15) | |
| Temperature (°C) | 40–50 | 69 | 69 |
| pH | 7.4–7.8 | 7.2–7.5 | 7.2–7.5 |
| Depth (m) | / | 1173–1230 | 1173–1230 |
| Chemical characteristics (mg/l) | |||
| Cl− | 4045 | 3697 | 3183 |
| CO3 2− | 33 | / | / |
| HCO3 − | 854 | 1013 | 1113 |
| Mg2+ | 41 | / | 41 |
| K+ + Na+ | 2795 | 2661 | 2338 |
| SO4 2− | 16 | / | / |
| Ca2+ | 92 | 104 | 56 |
| gas composition (%) | |||
| CH4 | Nd* | 79.87 | 96.90 |
| C2H6 | Nd | 6.95 | 0.99 |
| C3H8 | Nd | 7.54 | 0.93 |
| i-C4H10 | Nd | 1.40 | 0.15 |
| N-C4H10 | Nd | 2.46 | 0.26 |
| CO2 | Nd | 0.47 | 0.01 |
*not detected.