Deep water well intervention and fluid selection

Abstract

Worldwide, the number of subsea wells showed a substantial increase over the last decade. This trend is particularly relevant for deep- and ultra deep-water field developments, indicating that the offshore oil and gas production continues to move into deeper regions. West Africa, South America and the Gulf of Mexico (GoM) lead the deep-water operations and related subsea well intervention activities. The scope of this study is to explain why deep-water well intervention has become such a requirement and discuss the factors that are propagating this need. This thesis principally focuses on light well intervention operations performed on subsea wells. The challenges that follow by moving to increasing depths are presented and solutions are discussed. In particular, an assessment of selecting hydrate prevention inhibitors is presented, as the formation of hydrates is one of the major limiting factors regarding operations at large depths. Well integrity during well intervention is another aspect that is covered in this study, based on the standard NORSOK D-010 “Well integrity in drilling and well operations” for evaluations. This section contains technical and operational solutions to reduce the risk of uncontrolled release of formation fluids throughout the well intervention operation. Finally, this thesis outlines that well intervention operations can be economical and feasible in deep- and ultra-deep subsea wells by employing recently developed vessels, provided with dynamic positioning systems and designed specifically for subsea well intervention purposes.