Batch Drilling of Two Exploration Wells from a Jack Up Rig by Modifying Conductor Deck Results in Substantial Savings

Sharma, Deepak (Cairn Oil & Gas, Vedanta Ltd.) | Golwalkar, Anirudh (Cairn Oil & Gas, Vedanta Ltd.) | Singh, Ankit (Cairn Oil & Gas, Vedanta Ltd.) | Doodraj, Sunil (Cairn Oil & Gas, Vedanta Ltd.) | Vermani, Sanjeev (Cairn Oil & Gas, Vedanta Ltd.)



The scope of the paper is to explain, at first, the modification done to the conductor deck of a jack up rig in order to drill two exploration wells from one open water location, offshore of east coast of India. Further the paper explains the process of batch drilling used in the campaign and how the combination of the two resulted in substantial cost saving.

For the modification in conductor deck, feasibilities were checked for each rig during the tender evaluation stage to create an additional slot in the conductor deck while maintaining the conductor tensioning requirement on both slots. The conductor deck of the finalized rig was fabricated accordingly. The wells were planned, with one being vertical and the other deviated, to two different targets. The conductors on both wells were batch set. Similarly, the surface hole sections on both the wells were batch drilled & cased. Then drilling of the production holes, logging & abandonment were carried out batchwise.

As a result of batch drilling, the time in installation & removal of wellhead was completely saved as it was carried out offline. Similarly the time in installation & removal of BOP was reduced to half as it was done only once. There were other instances as well, described in detail in the paper, which led to a cumulative savings of 29.86 days against total planned time of 96.51 days during the complete drilling campaign, apart from saving days & associated weather risk by eliminating one complete rig move. Much of the time saved above was due to the batch drilling which was a result of the conductor deck modification and also due to the well design changes based on actual well conditions, which are also explained briefly in the paper.

As industry is recovering from a steep decline in drilling activity, it is only incremental innovations & even more so, a combination of existing innovations like the one showcased in this paper, which can lead to a positive economics for E&P companies, especially for exploration drilling projects.