Serban is an offshore drilling project located in Nunukan Block, Indonesia, approximately 3 km northwest of Bunyu Island, an offshore area with very shallow water depth, from below 1 (one) meter at low tide to more than 3 (three) meters at high tide. The most suitable drilling rig unit for such conditions is a swamp barge rig, but availability is very limited due to demand. As a result, inspired by the tender-assisted drilling rig, the option to modify an onshore drilling rig for an offshore drilling operation was chosen to overcome the aforementioned lack of availability.
Onshore rig equipment was laid out on an offshore drilling platform and flat top coal cargo barges. An offshore platform size 23 m x 28 m, was built to accommodate rig substructure, mast and well control equipment. The other rig equipment and supporting facilities, such as mud tanks, mud pumps, SCR system, cementing unit, pipe racking area, drilling material area, on site port camps, etc, were located on the existing three (3) flat top coal barges size 288 ft x 80 ft.
Serban-3 offshore well proved to drill safely using this modified system. An initial expense for drilling platform construction was required, but the daily operation rig costs using this system was almost 70% less than when using the swamp barge rig and 50% less than when using the tender-assisted drilling rig. This is of course a significant cost saving, especially for long term drilling projects.
Although some improvements are still required, this system is a promising alternative to overcome the limited availability of rigs for very shallow offshore areas.