Open Access

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

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