Prirazlomnaya: Drills First Ever Arctic Shelf Fishbone Well

The first ever multi-lateral “fishbone” well involving multiple horizontal branches has been drilled and commissioned at the Prirazlomnaya offshore rig — the only project on the Russian Arctic shelf at which commercial oil production is currently ongoing. The trajectory chosen for the wells allows significantly greater coverage of oil-bearing sections of the strata. The new well represents the fourth injection well at Prirazlomnaya — the platform having 11 wells currently in operation: six production wells, four injection wells, and one absorption well.

A multi-lateral well with a fishbone trajectory does not require the construction of separate wells for each horizontal shaft, thereby reducing the extent of works required, and subsequent drilling costs. Each horizontal section, directed at a specific oil-bearing section of the strata, increases the injection capacity of the well, as well as the drainage area.

The horizontal branches having been created through open-hole cutting and shearing, TAML (Technology Advancement for Multi-Laterals) criteria categorise this new well on the Russian Arctic shelf as among the most complex multi-barrel wells in its construction. The process of drilling multi-lateral fishbone wells is more labour-intensive than drilling traditional horizontal wells, since the main offshoots and the motherbore have a higher drilling difficulty index (DDI).

Andrey Patrushev, Deputy CEO for Offshore Development, Gazprom Neft, commented: “As a result of the seamless work of the Gazprom Neft Shelf team, the additional horizontal shafts were drilled all in one go, five days ahead of schedule. The most cutting-edge technologies — which are both effective and safe — have been used in developing what is a unique project on the Russian Arctic shelf.”