Some of the oil fields offshore Brunei are characterized by complex reservoir geology. This requires the drilling of highcomplexity, tortuous 3D horizontal wells referred to as "snake wells" for optimal reservoir drainage. These wells deliver an ultimate recovery equivalent to multiple horizontal wells drilled in the same structure. This development concept was chosen as the most beneficial with the business value drivers for the Selangkir Iron Duke (SKID) project.

Over a period of several years, drilling performance had improved but plateaued and still contained hours of nonproductive time (NPT), including hole conditioning wiper trips, rough drilling causing bottomhole assembly (BHA) failures due to vibrations, troublesome trips, and even lost production due to stuck-pipe incidents. In previous "snake well" drilling campaigns multiple additions to the BHA design to overcome tight hole problems had seen an ever more complex and rigid BHA being adopted, but without the required NPT or well cost reductions.

In an attempt to make a step change in performance the BHA design and drilling processes have undergone a comprehensive revision. The primary focus areas were to enable shoe-to-shoe runs, reduce the risk of stuck pipe, improve tripability of BHA, reduce torque and drag and last but not least improve the overall hole section progress. A more flexible, slimmer rotary steerable system (RSS) BHA design having a shorter, compact sourceless logging-while-drilling (LWD) tool was proposed to reduce damaging vibrations and ease tripping.

The paper discusses engineering solutions implemented to mitigate risks associated with complex well geometries which consequently contributed greatly to deliver the high-complexity extended-reach drilling (ERD) wells with top quartile and even best-in-class performance in the Rushmore’s Drilling Performance Review (DPR).