In the work environment of continuous improvement as a method to reduce both drilling and production costs, alternative means are required to attain objectives which have previously been deemed unachievable. The introduction of new tools and technologies has enabled increasingly challenging wellpaths to be drilled and completed. Trajectories labeled as undrillable even a few short years ago are now being realized.
The high cost and environmental concerns associated with offshore installations and the resultant requirement for drilling multiple wells from a common facility, has been a significant driver in the field of extended reach drilling to drain reservoirs with significant step-out. Sub-surface geological issues and wells with multiple targets have resulted in complex 3D well trajectories such as ‘pregnant lady’, ‘snake’ and ‘dragon’ wells.
Within the above context, Brunei Shell Petroleum (BSP) has identified that by drilling ‘fishhook’ shape wells, whereby a large section of the wellpath is drilled and completed at an inclination greater than 90°, significant savings in both drilling and production costs can be achieved. This is a case study of such a well drilled in mid 2004, whereby some 875m, or 35% of the total well trajectory was drilled at an inclination greater than 90°. The well also required 7" casing to be run and cemented to well TD, sand control in the form of Frac and Packs, and Expandable Sand Screens (ESS) run across three reservoir zones, with isolation between each zone.
Maximum inclination was 126.5°, and some 366m true vertical depth (TVD) reclaimed.