ONGC Achieves a New Water Depth Record Outside Atlantic

ONGC's conventionally-drilled deepwater well, GSDW1-1A, with water depth of 2839 meters, now occupies the topmost position in highest water depth wells, outside the Atlantic.

When Sagar Samriddhi started off its ultra deepwater campaign with well GKDWA-1, it created a water depth record of 1860 meters, for Indian Offshore. That well was drilled conventionally, i.e. by installing subsea BOP/risers after lowering the surface conductors. Since then, there has been many firsts to the credit of Sagar Samriddhi.

An earlier explorer well GSDW-2A-1 in water depth of 3008 meters was drilled successfully to the TD, without having to lower subsea BOP and risers as the subsurface conditions did not allow installation of BOP and risers. That was an unique achievement which put ONGC into the league of top deepwater operators.

Among the conventionally-drilled deepwater wells, the GSDW1-1A, with water depth of 2839 meters, now occupies the top position in highest water depth wells outside the Atlantic.

The most challenging part of deepwater drilling is handling of the risers, which connect the drillship to the wellhead placed at seabed. The heavy weight of the risers and the various types of loading on them due to met-oceanic forces put enormous amount of power requirement on the rig systems. In fact the major factor in determining the water depth capability of the drillship is her ability to handle risers. The drillship Belford Dolphin had to face the ultimate test when she spudded the well GSDW1-1A. The requirement of long riser string together with unfavorable weather conditions put enormous load, >1900 kips on the hook, forcing the rig to suspend operations on the well.

New floatation equipment was mobilized and installed on the risers. The floatation equipment is buoyancy modules, which make the riser buoyant, and therefore only part of the riser weight is required to be supported by the rig. With new floatation equipment and relatively better weather conditions the well was re-entered on December 7, 2004. The lowering of risers and BOP progressed without any problems, the hook-load remaining within the acceptable limits. Further drilling continued as per plan and the TD was reached on December 14, 2004. Another notable feature of this well was use of 20" X 13 3/8" crossover, which resulted in saving of over US$100,000. The BOP and risers were pulled out successfully and the rig moved to the next location on December 19, 2004.

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