ONGC abandons deepwater well at KG-DWN-98/2

Vol 9, PW 12 (22 Sep 05) Exploration & Production

ONGC has been forced to abandon the well at the source of its row with the DGH over premature discovery announcements.

PETROWATCH learns the well on the D prospect at eastern offshore deepwater block KG-DWN-98/2 was abandoned as a total loss early this month following an accident on Transocean deepwater drillship Discoverer Seven Seas. Spud on 15th August, it was the most promising exploratory well in ONGCs ambitious 37-well deepwater drilling programme.

Seven Seas had reached target depth of 2400 metres in the first week of September at the end of a 20-day incident-free drilling period. But trouble struck when ONGC logged the well and was lowering the final 9 5/8-inch casing at 1600 metres to 2400 metres.

An industry source tells us there was a power blackout on Seven Seas while the final casing was being lowered on 8th September. Back-up power did not come on and the thrusters that power the rigs dynamic positioning system stopped working, we learn.

With no power to keep it steady the rig began drifting and the yellow (danger) signal came on, indicating a drift beyond permissible limits. As a result of this drift, the riser separated from the Blow Out Preventor and the casing snapped and fell into the well along with the shear ram.

By the time the power supply resumed, the well was severely damaged. ONGC personnel first checked the integrity of the dynamic positioning system, re-latched the Blow Out Preventor and re-lowered it.

Along with the casing, parts of the Blow Out Preventor also fell into the well. ONGC tried to pull the casing up by engaging it, but failed.

When the power supply resumed, ONGC could have attempted a fishing operation to retrieve the string, but decided against it. ONGC calculated it would take at least two to three weeks for a fishing operation, we learn.

Within that time they could drill another well so they decided against fishing and abandoned the well. Cost of the abandoned well: at least Rs40cr ($9m).

ONGC has since relocated Seven Seas to Mahanadi basin block MN-OSN-2000/2.