Abstract
A large number of subsea production wells have been drilled, but to date there has been limited industry experience of redrilling subsea wells, whereas, redrills have become routine in platform and surface wellhead applications. The focus of this paper is to highlight some of the key aspects of redrilling a subsea production well to extend field life.
The paper will describe how the unique challenges of redrilling three subsea wells were overcome in old and declining fields where the original wells were designed and drilled with limited consideration for redevelopment of the fields through reuse of existing wells. The paper will define the problems of and describe the solutions to:
The mooring and BOP handling constraints in the crowded subsea infrastructure of a subsea field development.
The riser and wellhead analysis for redrilling a well through a subsea tree, and the operational practices required to maintain tree and wellbore integrity.
The analysis of the additional loads put on a subsea well through the extended period of riser and BOP loading.
The casing exit and redrill constraints unique to operations from a semi-submersible rig; casing recovery operations, the management of window milling debris in a subsea BOP system.
There has been limited industry experience to date of subsea production well redrills, and this paper will share the significant lessons learned which will be of wider application, as the number of subsea wells increase along with the requirement to maximize recovery and extend field life.
