34/10-10

General

Well 34/10-10 was drilled on the Delta structure situated in the Gullfaks Vest area in the north-eastern part of block 34/10. The primary objective was to test sandstones of Middle Jurassic age. Secondary objectives were sandstones of Early Jurassic and Late Triassic age. The well was planned to be drilled into Triassic to a total depth of 2265 m.

Operations and results

On 10 July 1980 at 2330 hrs the semi-submersible installation Norskald was transferred from well 15/9-6 to well 34/10-10. After the rig had been anchored up on the 34/10-10 location a strike broke out among the drilling crew. Due to the strike the operation was one month delayed and the well was not spudded until 15 August at 1930 hrs. The 36" hole was drilled to 229 m with a 26" bit and a 36" hole opener without temporary guide-base. Seawater was used with returns to the sea floor. The hole was slugged with high viscosity mud prior to each connection. The riser was run and the diverter system installed. From 229 to 816 m in the Nordland Group (Miocene age) the well was drilled first as a 17 1/2" pilot hole and logged, then with a 26" hole opener. When disconnecting the marine riser on 21 August, the well started to flow. The rig was quickly moved off location and out of danger from the gas flow.

The well flowed for approximately one and a half hours the morning of the blowout and again for two and a half hours the same evening. Periodic subsea observations over the next days, showed continued flow from the wellhead at a greatly reduced rate with only one brief surface indication of flow. Post-well analysis of the incident concluded that the gas came from shallow sand at 4