Abstract
Shell Exploration & Production in Aberdeen, Scotland has implemented through tubing rotary drilling (TTRD) as a cost effective method of accessing small accumulations of hydrocarbons in some of its mature assets in the UK sector of the North Sea. Working together with its contractors, the implementation of TTRD has taken place over the past 6 years. The most recent experience is a 5 well campaign on the North Cormorant platform during the past year. This paper gives an overview of the implementation process including a history of the work done, highlights and lowlights of drilling operations that have taken place to date. However, it focuses on the issues that were addressed in relation to the current campaign. Topics that will be covered are:
Planning Process: An evaluation was done leading up to the current campaign to identify the areas of improvement that would yield the highest value. Resources were dedicated to the improvement initiative, beyond what would normally be assigned for conventional drilling operations.
Novel Drilling Fluid Application: The conventional weighting agent (barite) was replaced by manganese tetra-oxide to give a low rheology fluid with enhanced anti-sag characteristics.
Drilling Performance Optimisation: Work was done to reduce the torque requirement of the drill bits used for TTRD and match those requirements to the capability of the slim hole drilling motors for the required hole size.
Equipment Upgrades: Surface equipment and downhole tools were developed and existing tools improved in order to improve performance and increase overall capability. Critical equipment that was either developed or significantly improved included: kick detection equipment, directional drilling bottom hole assembly, perforating guns, and swelling elastomer packers.
The benefit of TTRD, demonstrated by the successful campaign on the North Cormorant, is being carried forward to the rest of the Shell Exploration & Production organisation through the establishment of Global Implementation Team specifically for through tubing drilling. Shell is looking forward to realizing the benefit of this technology worldwide.
