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Abstract An integral wellhead system is a key component in maintaining sustainable production and a pollution free environment. The wellhead is a part of the well integrity envelope for the well, as it carries some of the safety critical equipment and applicable redundancies. It is designed, installed and maintained to ensure it remains an integral part of the production system throughout the lifecycle of the well on which it is installed. The industry has recorded huge successes in achieving this objective through standardization of wellhead specifications to meet the requirements of different service environments. Despite best endeavours, there are instances where well integrity has been compromised in ageing wells with wellheads that were designed to specifications which are now obsolete, or wellheads that have experienced cavities and corrosion induced wellhead-casing connection failures amongst other defects. Furthermore, in challenging work environments such as the Niger Delta region of Nigeria, human factors such as vandalism of wellhead systems have made maintaining and restoring well integrity more prevalent. In recent times, non-conventional remediations are deployed where the wells have been damaged to the extent that neither well established rig-less or rig-based intervention activities are possible. In these circumstances, the only viable option to restore well integrity is through de-heading damaged wellheads and installing a new one via a tie-back and re-heading process. The tie-back operation is highly specialized and safety critical with bespoke procedures for successful execution. This paper focuses on a case study where a casing jack unit was used in challenging well control circumstances to de-head, tie-back all casings and dual completions tubing, followed by the installation of a new wellhead. It highlights the multi-disciplinary team approach, key considerations and mitigations deployed to carry out the operation in a controlled and safe manner to restore wellhead integrity.
Olowu et al. (Mon,) studied this question.