Table 3
The main characteristics of Eminence, Mississipi; Teutschenthal, Germany; Boling, Texas; Clute, Texas.
| Eminence, Mississipi | Teutschenthal, Germany | Boling, Texas | Clute, Texas | ||
|---|---|---|---|---|---|
| Cavern information | Commissioning | 1970–1973. Caverns #1–#4 | 1971 | 1983. Caverns #1, #2, #4 | Leached out in 1961 |
| Inccident date (1st noticed) | December 26, 2010 | March 29, 1988 | December 24, 2003 | December 1988 | |
| Geology | Domal salt (Eminence dome), 150-m thick caprock, whose roof is at 600 m. | Bedded salt. Top of salt from 500 to 1000 m, overlaid by a 300 m thick clay layer and 110 m of clay/sand layers. | Domal salt (Boling dome), Caprock at 190 m and above, salt roof at 300 m | Domal salt (Stratton Ridge dome), 100-m thick caprock, limestone, gypsum, anhydrite. The dome is likely to be active. | |
| Stored product | Natural gas | Ethylene | Natural gas | Ethylene | |
| Last cemented casing shoe | 13-⅜ at 1737 m | 11-¾″ at 728.4 m | 1066–1083 m. Very close to cavern roof for #1, #2, #4. | ||
| Penultimate cemented c.s. | 20″ at 823 m | 16¾″ at 92,1 m | |||
| Leak mechanism | Breach depth | Connection at 111.8 m? | Eight seen from video logs between 3100 and 3400 ft | ||
| Pressure drop | 2.46 MPa in 1 min on #3 | From 7.5 MPa to 4 MPa | Rapid pressure drop over several weeks | ||
| Mechanism | Likely factors: Fast cavern closure rate (40% in one year) frequent re-brining, | Ethylene accumulated in a 100–140-m deep layer overlain by a poorly permeable, 25-m thick layer. Layer uplift led to overstretch of the 11-¾″ casing, which breaks on March 29, followed by a massive leak. Ethylene leakage paths are along existing faults. | Casing overstretch and failure, dragged down by the salt. This was facilitated by the flat roofs and the absence of cavern necks. | Effects of dome internal movements? | |
| Impact at the surface | Effects at ground level | Blow-outs in shallow boreholes | One hour after the pressure drop, first ethylene + water blow-out, followed by several others, gas production during several days, 60% to 80% of cavern volume is lost. Blow-out spots aligned on parallel lines. Ground uplift by 1.5 m before the eruption. Fractures at ground level. | None | None. Gas loss estimated to be 27 000 m3 on December 30. |
| Distance from wellhead | The leak escaped from the ground around #1 wellhead | 50 m–250 m | |||
| Evacuation/Casualties | Twenty families during two weeks | An 8 km2 zone | |||
| Emergency resp. and remediation | Measures taken | Partial venting 245 shallow boreholes drilled 13 boreholes drilled to the caprock | Ethylene dilution was swift. Alignment of blow-out spots was checked through aerial photos. | Cold spots detected above the casing shoe by temperature logs. Video inspection. | After discussion with the mining authorities, a new borehole was drilled, encountering gas on March 19, 1990. Gas was vented. |
| Remediation | The four caverns are abandoned | An 8-⅝″ string is set in the casing and the annular space is monitored. | Milling of the 11-¾″ casing on a 30-m length, a 10-¾″ string is set in the casing. | Unknown |