CTD (Coil Tubing Drilling) has become a mature and successful technology in the continued development of the northern Alaska oilfields. Driven by advancing existing product limits and embracing new technologies, this paper details the development of a new completion technology that allows the operator to plan for and place pre-determined casing exit points within the wellbore to be accessed in the future as the well matures. This new technology addresses many of the typical limiting factors faced by operators when identifying future CTD candidates by reducing the typical preparation time, costs, and equipment limitations currently available to them.
The paper will show the viability and flexibility the operator gains by incorporating the use of pre-determined and spaced outer wedge assemblies affixed to the outside of the production tubing joints and run during the completion phase. The operator has the flexibility to run as many outer wedge assemblies as needed, based on their future field development strategy without imposing limitations on primary completion access or drainage capabilities. When required, an inner wedge assembly is then run and positioned within the outer wedge assembly, using a common wireline set tubing plug as a false bottom no-go. Orientation of the inner wedge is at the operators' discretion. The milling assembly will first mill through the production tubing before being deflected by the outer wedge assembly to then mill through the production casing. Details of the design, testing, and implementation of the system and components will be detailed within the paper.
This technology allows operators to plan for the life of the well at the completion phase. This reduces CTD preparation costs, provides simplified zonal isolation flexibility, and allows upper zones to be exited first if required. The technology reduces the risks and cost of dual string exits, while removing the need to leave an exposed large bore casing/liner at the exit point that could create difficulties during CTD drilling. Future advances and optimization of completion designs are expected to provide a cementless CTD liner completion while retaining zonal isolation capabilities within the wellbore.